Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4723 insertions, 0 deletions

diff --git a/third_party/libsrtp/src/srtp/srtp.c b/third_party/libsrtp/src/srtp/srtp.c
new file mode 100644
index 0000000000..fc0b1b0ad1
--- /dev/null
+++ b/third_party/libsrtp/src/srtp/srtp.c
@@ -0,0 +1,4723 @@
+/*
+ * srtp.c
+ *
+ * the secure real-time transport protocol
+ *
+ * David A. McGrew
+ * Cisco Systems, Inc.
+ */
+/*
+ *
+ * Copyright (c) 2001-2017, Cisco Systems, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ *   Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ *   Neither the name of the Cisco Systems, Inc. nor the names of its
+ *   contributors may be used to endorse or promote products derived
+ *   from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+// Leave this as the top level import. Ensures the existence of defines
+#include "config.h"
+
+#include "srtp_priv.h"
+#include "crypto_types.h"
+#include "err.h"
+#include "alloc.h" /* for srtp_crypto_alloc() */
+
+#ifdef GCM
+#include "aes_gcm.h" /* for AES GCM mode */
+#endif
+
+#ifdef OPENSSL_KDF
+#include <openssl/kdf.h>
+#include "aes_icm_ext.h"
+#endif
+
+#include <limits.h>
+#ifdef HAVE_NETINET_IN_H
+#include <netinet/in.h>
+#elif defined(HAVE_WINSOCK2_H)
+#include <winsock2.h>
+#endif
+
+/* the debug module for srtp */
+srtp_debug_module_t mod_srtp = {
+    0,     /* debugging is off by default */
+    "srtp" /* printable name for module */
+};
+
+#define octets_in_rtp_header 12
+#define uint32s_in_rtp_header 3
+#define octets_in_rtcp_header 8
+#define uint32s_in_rtcp_header 2
+#define octets_in_rtp_extn_hdr 4
+
+static srtp_err_status_t srtp_validate_rtp_header(void *rtp_hdr,
+                                                  int *pkt_octet_len)
+{
+    srtp_hdr_t *hdr = (srtp_hdr_t *)rtp_hdr;
+    int rtp_header_len;
+
+    if (*pkt_octet_len < octets_in_rtp_header)
+        return srtp_err_status_bad_param;
+
+    /* Check RTP header length */
+    rtp_header_len = octets_in_rtp_header + 4 * hdr->cc;
+    if (hdr->x == 1)
+        rtp_header_len += octets_in_rtp_extn_hdr;
+
+    if (*pkt_octet_len < rtp_header_len)
+        return srtp_err_status_bad_param;
+
+    /* Verifing profile length. */
+    if (hdr->x == 1) {
+        srtp_hdr_xtnd_t *xtn_hdr =
+            (srtp_hdr_xtnd_t *)((uint32_t *)hdr + uint32s_in_rtp_header +
+                                hdr->cc);
+        int profile_len = ntohs(xtn_hdr->length);
+        rtp_header_len += profile_len * 4;
+        /* profile length counts the number of 32-bit words */
+        if (*pkt_octet_len < rtp_header_len)
+            return srtp_err_status_bad_param;
+    }
+    return srtp_err_status_ok;
+}
+
+const char *srtp_get_version_string()
+{
+    /*
+     * Simply return the autotools generated string
+     */
+    return SRTP_VER_STRING;
+}
+
+unsigned int srtp_get_version()
+{
+    unsigned int major = 0, minor = 0, micro = 0;
+    unsigned int rv = 0;
+    int parse_rv;
+
+    /*
+     * Parse the autotools generated version
+     */
+    parse_rv = sscanf(SRTP_VERSION, "%u.%u.%u", &major, &minor, &micro);
+    if (parse_rv != 3) {
+        /*
+         * We're expected to parse all 3 version levels.
+         * If not, then this must not be an official release.
+         * Return all zeros on the version
+         */
+        return (0);
+    }
+
+    /*
+     * We allow 8 bits for the major and minor, while
+     * allowing 16 bits for the micro.  16 bits for the micro
+     * may be beneficial for a continuous delivery model
+     * in the future.
+     */
+    rv |= (major & 0xFF) << 24;
+    rv |= (minor & 0xFF) << 16;
+    rv |= micro & 0xFF;
+    return rv;
+}
+
+srtp_err_status_t srtp_stream_dealloc(srtp_stream_ctx_t *stream,
+                                      const srtp_stream_ctx_t *stream_template)
+{
+    srtp_err_status_t status;
+    unsigned int i = 0;
+    srtp_session_keys_t *session_keys = NULL;
+    srtp_session_keys_t *template_session_keys = NULL;
+
+    /*
+     * we use a conservative deallocation strategy - if any deallocation
+     * fails, then we report that fact without trying to deallocate
+     * anything else
+     */
+    if (stream->session_keys) {
+        for (i = 0; i < stream->num_master_keys; i++) {
+            session_keys = &stream->session_keys[i];
+
+            if (stream_template &&
+                stream->num_master_keys == stream_template->num_master_keys) {
+                template_session_keys = &stream_template->session_keys[i];
+            } else {
+                template_session_keys = NULL;
+            }
+
+            /*
+            * deallocate cipher, if it is not the same as that in template
+            */
+            if (template_session_keys &&
+                session_keys->rtp_cipher == template_session_keys->rtp_cipher) {
+                /* do nothing */
+            } else if (session_keys->rtp_cipher) {
+                status = srtp_cipher_dealloc(session_keys->rtp_cipher);
+                if (status)
+                    return status;
+            }
+
+            /*
+             * deallocate auth function, if it is not the same as that in
+             * template
+             */
+            if (template_session_keys &&
+                session_keys->rtp_auth == template_session_keys->rtp_auth) {
+                /* do nothing */
+            } else if (session_keys->rtp_auth) {
+                status = srtp_auth_dealloc(session_keys->rtp_auth);
+                if (status)
+                    return status;
+            }
+
+            if (template_session_keys &&
+                session_keys->rtp_xtn_hdr_cipher ==
+                    template_session_keys->rtp_xtn_hdr_cipher) {
+                /* do nothing */
+            } else if (session_keys->rtp_xtn_hdr_cipher) {
+                status = srtp_cipher_dealloc(session_keys->rtp_xtn_hdr_cipher);
+                if (status)
+                    return status;
+            }
+
+            /*
+             * deallocate rtcp cipher, if it is not the same as that in
+             * template
+             */
+            if (template_session_keys &&
+                session_keys->rtcp_cipher ==
+                    template_session_keys->rtcp_cipher) {
+                /* do nothing */
+            } else if (session_keys->rtcp_cipher) {
+                status = srtp_cipher_dealloc(session_keys->rtcp_cipher);
+                if (status)
+                    return status;
+            }
+
+            /*
+             * deallocate rtcp auth function, if it is not the same as that in
+             * template
+             */
+            if (template_session_keys &&
+                session_keys->rtcp_auth == template_session_keys->rtcp_auth) {
+                /* do nothing */
+            } else if (session_keys->rtcp_auth) {
+                status = srtp_auth_dealloc(session_keys->rtcp_auth);
+                if (status)
+                    return status;
+            }
+
+            /*
+             * zeroize the salt value
+             */
+            octet_string_set_to_zero(session_keys->salt, SRTP_AEAD_SALT_LEN);
+            octet_string_set_to_zero(session_keys->c_salt, SRTP_AEAD_SALT_LEN);
+
+            if (session_keys->mki_id) {
+                octet_string_set_to_zero(session_keys->mki_id,
+                                         session_keys->mki_size);
+                srtp_crypto_free(session_keys->mki_id);
+                session_keys->mki_id = NULL;
+            }
+
+            /*
+             * deallocate key usage limit, if it is not the same as that in
+             * template
+             */
+            if (template_session_keys &&
+                session_keys->limit == template_session_keys->limit) {
+                /* do nothing */
+            } else if (session_keys->limit) {
+                srtp_crypto_free(session_keys->limit);
+            }
+        }
+        srtp_crypto_free(stream->session_keys);
+    }
+
+    status = srtp_rdbx_dealloc(&stream->rtp_rdbx);
+    if (status)
+        return status;
+
+    if (stream_template &&
+        stream->enc_xtn_hdr == stream_template->enc_xtn_hdr) {
+        /* do nothing */
+    } else if (stream->enc_xtn_hdr) {
+        srtp_crypto_free(stream->enc_xtn_hdr);
+    }
+
+    /* deallocate srtp stream context */
+    srtp_crypto_free(stream);
+
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_valid_policy(const srtp_policy_t *p)
+{
+    if (p != NULL && p->deprecated_ekt != NULL) {
+        return srtp_err_status_bad_param;
+    }
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_stream_alloc(srtp_stream_ctx_t **str_ptr,
+                                    const srtp_policy_t *p)
+{
+    srtp_stream_ctx_t *str;
+    srtp_err_status_t stat;
+    unsigned int i = 0;
+    srtp_session_keys_t *session_keys = NULL;
+
+    stat = srtp_valid_policy(p);
+    if (stat != srtp_err_status_ok) {
+        return stat;
+    }
+
+    /*
+     * This function allocates the stream context, rtp and rtcp ciphers
+     * and auth functions, and key limit structure.  If there is a
+     * failure during allocation, we free all previously allocated
+     * memory and return a failure code.  The code could probably
+     * be improved, but it works and should be clear.
+     */
+
+    /* allocate srtp stream and set str_ptr */
+    str = (srtp_stream_ctx_t *)srtp_crypto_alloc(sizeof(srtp_stream_ctx_t));
+    if (str == NULL)
+        return srtp_err_status_alloc_fail;
+
+    *str_ptr = str;
+
+    /*
+     *To keep backwards API compatible if someone is using multiple master
+     * keys then key should be set to NULL
+     */
+    if (p->key != NULL) {
+        str->num_master_keys = 1;
+    } else {
+        str->num_master_keys = p->num_master_keys;
+    }
+
+    str->session_keys = (srtp_session_keys_t *)srtp_crypto_alloc(
+        sizeof(srtp_session_keys_t) * str->num_master_keys);
+
+    if (str->session_keys == NULL) {
+        srtp_stream_dealloc(str, NULL);
+        return srtp_err_status_alloc_fail;
+    }
+
+    for (i = 0; i < str->num_master_keys; i++) {
+        session_keys = &str->session_keys[i];
+
+        /* allocate cipher */
+        stat = srtp_crypto_kernel_alloc_cipher(
+            p->rtp.cipher_type, &session_keys->rtp_cipher,
+            p->rtp.cipher_key_len, p->rtp.auth_tag_len);
+        if (stat) {
+            srtp_stream_dealloc(str, NULL);
+            return stat;
+        }
+
+        /* allocate auth function */
+        stat = srtp_crypto_kernel_alloc_auth(
+            p->rtp.auth_type, &session_keys->rtp_auth, p->rtp.auth_key_len,
+            p->rtp.auth_tag_len);
+        if (stat) {
+            srtp_stream_dealloc(str, NULL);
+            return stat;
+        }
+
+        /*
+         * ...and now the RTCP-specific initialization - first, allocate
+         * the cipher
+         */
+        stat = srtp_crypto_kernel_alloc_cipher(
+            p->rtcp.cipher_type, &session_keys->rtcp_cipher,
+            p->rtcp.cipher_key_len, p->rtcp.auth_tag_len);
+        if (stat) {
+            srtp_stream_dealloc(str, NULL);
+            return stat;
+        }
+
+        /* allocate auth function */
+        stat = srtp_crypto_kernel_alloc_auth(
+            p->rtcp.auth_type, &session_keys->rtcp_auth, p->rtcp.auth_key_len,
+            p->rtcp.auth_tag_len);
+        if (stat) {
+            srtp_stream_dealloc(str, NULL);
+            return stat;
+        }
+
+        session_keys->mki_id = NULL;
+
+        /* allocate key limit structure */
+        session_keys->limit = (srtp_key_limit_ctx_t *)srtp_crypto_alloc(
+            sizeof(srtp_key_limit_ctx_t));
+        if (session_keys->limit == NULL) {
+            srtp_stream_dealloc(str, NULL);
+            return srtp_err_status_alloc_fail;
+        }
+    }
+
+    if (p->enc_xtn_hdr && p->enc_xtn_hdr_count > 0) {
+        srtp_cipher_type_id_t enc_xtn_hdr_cipher_type;
+        int enc_xtn_hdr_cipher_key_len;
+
+        str->enc_xtn_hdr = (int *)srtp_crypto_alloc(p->enc_xtn_hdr_count *
+                                                    sizeof(p->enc_xtn_hdr[0]));
+        if (!str->enc_xtn_hdr) {
+            srtp_stream_dealloc(str, NULL);
+            return srtp_err_status_alloc_fail;
+        }
+        memcpy(str->enc_xtn_hdr, p->enc_xtn_hdr,
+               p->enc_xtn_hdr_count * sizeof(p->enc_xtn_hdr[0]));
+        str->enc_xtn_hdr_count = p->enc_xtn_hdr_count;
+
+        /*
+         * For GCM ciphers, the corresponding ICM cipher is used for header
+         * extensions encryption.
+         */
+        switch (p->rtp.cipher_type) {
+        case SRTP_AES_GCM_128:
+            enc_xtn_hdr_cipher_type = SRTP_AES_ICM_128;
+            enc_xtn_hdr_cipher_key_len = SRTP_AES_ICM_128_KEY_LEN_WSALT;
+            break;
+        case SRTP_AES_GCM_256:
+            enc_xtn_hdr_cipher_type = SRTP_AES_ICM_256;
+            enc_xtn_hdr_cipher_key_len = SRTP_AES_ICM_256_KEY_LEN_WSALT;
+            break;
+        default:
+            enc_xtn_hdr_cipher_type = p->rtp.cipher_type;
+            enc_xtn_hdr_cipher_key_len = p->rtp.cipher_key_len;
+            break;
+        }
+
+        for (i = 0; i < str->num_master_keys; i++) {
+            session_keys = &str->session_keys[i];
+
+            /* allocate cipher for extensions header encryption */
+            stat = srtp_crypto_kernel_alloc_cipher(
+                enc_xtn_hdr_cipher_type, &session_keys->rtp_xtn_hdr_cipher,
+                enc_xtn_hdr_cipher_key_len, 0);
+            if (stat) {
+                srtp_stream_dealloc(str, NULL);
+                return stat;
+            }
+        }
+    } else {
+        for (i = 0; i < str->num_master_keys; i++) {
+            session_keys = &str->session_keys[i];
+            session_keys->rtp_xtn_hdr_cipher = NULL;
+        }
+
+        str->enc_xtn_hdr = NULL;
+        str->enc_xtn_hdr_count = 0;
+    }
+
+    return srtp_err_status_ok;
+}
+
+/*
+ * srtp_stream_clone(stream_template, new) allocates a new stream and
+ * initializes it using the cipher and auth of the stream_template
+ *
+ * the only unique data in a cloned stream is the replay database and
+ * the SSRC
+ */
+
+srtp_err_status_t srtp_stream_clone(const srtp_stream_ctx_t *stream_template,
+                                    uint32_t ssrc,
+                                    srtp_stream_ctx_t **str_ptr)
+{
+    srtp_err_status_t status;
+    srtp_stream_ctx_t *str;
+    unsigned int i = 0;
+    srtp_session_keys_t *session_keys = NULL;
+    const srtp_session_keys_t *template_session_keys = NULL;
+
+    debug_print(mod_srtp, "cloning stream (SSRC: 0x%08x)", ntohl(ssrc));
+
+    /* allocate srtp stream and set str_ptr */
+    str = (srtp_stream_ctx_t *)srtp_crypto_alloc(sizeof(srtp_stream_ctx_t));
+    if (str == NULL)
+        return srtp_err_status_alloc_fail;
+    *str_ptr = str;
+
+    str->num_master_keys = stream_template->num_master_keys;
+    str->session_keys = (srtp_session_keys_t *)srtp_crypto_alloc(
+        sizeof(srtp_session_keys_t) * str->num_master_keys);
+
+    if (str->session_keys == NULL) {
+        srtp_stream_dealloc(*str_ptr, stream_template);
+        *str_ptr = NULL;
+        return srtp_err_status_alloc_fail;
+    }
+
+    for (i = 0; i < stream_template->num_master_keys; i++) {
+        session_keys = &str->session_keys[i];
+        template_session_keys = &stream_template->session_keys[i];
+
+        /* set cipher and auth pointers to those of the template */
+        session_keys->rtp_cipher = template_session_keys->rtp_cipher;
+        session_keys->rtp_auth = template_session_keys->rtp_auth;
+        session_keys->rtp_xtn_hdr_cipher =
+            template_session_keys->rtp_xtn_hdr_cipher;
+        session_keys->rtcp_cipher = template_session_keys->rtcp_cipher;
+        session_keys->rtcp_auth = template_session_keys->rtcp_auth;
+        session_keys->mki_size = template_session_keys->mki_size;
+
+        if (template_session_keys->mki_size == 0) {
+            session_keys->mki_id = NULL;
+        } else {
+            session_keys->mki_id =
+                srtp_crypto_alloc(template_session_keys->mki_size);
+
+            if (session_keys->mki_id == NULL) {
+                srtp_stream_dealloc(*str_ptr, stream_template);
+                *str_ptr = NULL;
+                return srtp_err_status_init_fail;
+            }
+            memcpy(session_keys->mki_id, template_session_keys->mki_id,
+                   session_keys->mki_size);
+        }
+        /* Copy the salt values */
+        memcpy(session_keys->salt, template_session_keys->salt,
+               SRTP_AEAD_SALT_LEN);
+        memcpy(session_keys->c_salt, template_session_keys->c_salt,
+               SRTP_AEAD_SALT_LEN);
+
+        /* set key limit to point to that of the template */
+        status = srtp_key_limit_clone(template_session_keys->limit,
+                                      &session_keys->limit);
+        if (status) {
+            srtp_stream_dealloc(*str_ptr, stream_template);
+            *str_ptr = NULL;
+            return status;
+        }
+    }
+
+    /* initialize replay databases */
+    status = srtp_rdbx_init(
+        &str->rtp_rdbx, srtp_rdbx_get_window_size(&stream_template->rtp_rdbx));
+    if (status) {
+        srtp_stream_dealloc(*str_ptr, stream_template);
+        *str_ptr = NULL;
+        return status;
+    }
+    srtp_rdb_init(&str->rtcp_rdb);
+    str->allow_repeat_tx = stream_template->allow_repeat_tx;
+
+    /* set ssrc to that provided */
+    str->ssrc = ssrc;
+
+    /* reset pending ROC */
+    str->pending_roc = 0;
+
+    /* set direction and security services */
+    str->direction = stream_template->direction;
+    str->rtp_services = stream_template->rtp_services;
+    str->rtcp_services = stream_template->rtcp_services;
+
+    /* copy information about extensions header encryption */
+    str->enc_xtn_hdr = stream_template->enc_xtn_hdr;
+    str->enc_xtn_hdr_count = stream_template->enc_xtn_hdr_count;
+
+    /* defensive coding */
+    str->next = NULL;
+    return srtp_err_status_ok;
+}
+
+/*
+ * key derivation functions, internal to libSRTP
+ *
+ * srtp_kdf_t is a key derivation context
+ *
+ * srtp_kdf_init(&kdf, cipher_id, k, keylen) initializes kdf to use cipher
+ * described by cipher_id, with the master key k with length in octets keylen.
+ *
+ * srtp_kdf_generate(&kdf, l, kl, keylen) derives the key
+ * corresponding to label l and puts it into kl; the length
+ * of the key in octets is provided as keylen.  this function
+ * should be called once for each subkey that is derived.
+ *
+ * srtp_kdf_clear(&kdf) zeroizes and deallocates the kdf state
+ */
+
+typedef enum {
+    label_rtp_encryption = 0x00,
+    label_rtp_msg_auth = 0x01,
+    label_rtp_salt = 0x02,
+    label_rtcp_encryption = 0x03,
+    label_rtcp_msg_auth = 0x04,
+    label_rtcp_salt = 0x05,
+    label_rtp_header_encryption = 0x06,
+    label_rtp_header_salt = 0x07
+} srtp_prf_label;
+
+#define MAX_SRTP_KEY_LEN 256
+
+#if defined(OPENSSL) && defined(OPENSSL_KDF)
+#define MAX_SRTP_AESKEY_LEN 32
+#define MAX_SRTP_SALT_LEN 14
+
+/*
+ * srtp_kdf_t represents a key derivation function.  The SRTP
+ * default KDF is the only one implemented at present.
+ */
+typedef struct {
+    uint8_t master_key[MAX_SRTP_AESKEY_LEN];
+    uint8_t master_salt[MAX_SRTP_SALT_LEN];
+    const EVP_CIPHER *evp;
+} srtp_kdf_t;
+
+static srtp_err_status_t srtp_kdf_init(srtp_kdf_t *kdf,
+                                       const uint8_t *key,
+                                       int key_len,
+                                       int salt_len)
+{
+    memset(kdf, 0x0, sizeof(srtp_kdf_t));
+
+    /* The NULL cipher has zero key length */
+    if (key_len == 0)
+        return srtp_err_status_ok;
+
+    if ((key_len > MAX_SRTP_AESKEY_LEN) || (salt_len > MAX_SRTP_SALT_LEN)) {
+        return srtp_err_status_bad_param;
+    }
+    switch (key_len) {
+    case SRTP_AES_256_KEYSIZE:
+        kdf->evp = EVP_aes_256_ctr();
+        break;
+    case SRTP_AES_192_KEYSIZE:
+        kdf->evp = EVP_aes_192_ctr();
+        break;
+    case SRTP_AES_128_KEYSIZE:
+        kdf->evp = EVP_aes_128_ctr();
+        break;
+    default:
+        return srtp_err_status_bad_param;
+        break;
+    }
+    memcpy(kdf->master_key, key, key_len);
+    memcpy(kdf->master_salt, key + key_len, salt_len);
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_kdf_generate(srtp_kdf_t *kdf,
+                                           srtp_prf_label label,
+                                           uint8_t *key,
+                                           unsigned int length)
+{
+    int ret;
+
+    /* The NULL cipher will not have an EVP */
+    if (!kdf->evp)
+        return srtp_err_status_ok;
+    octet_string_set_to_zero(key, length);
+
+    /*
+     * Invoke the OpenSSL SRTP KDF function
+     * This is useful if OpenSSL is in FIPS mode and FIP
+     * compliance is required for SRTP.
+     */
+    ret = kdf_srtp(kdf->evp, (char *)&kdf->master_key,
+                   (char *)&kdf->master_salt, NULL, NULL, label, (char *)key);
+    if (ret == -1) {
+        return (srtp_err_status_algo_fail);
+    }
+
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_kdf_clear(srtp_kdf_t *kdf)
+{
+    octet_string_set_to_zero(kdf->master_key, MAX_SRTP_AESKEY_LEN);
+    octet_string_set_to_zero(kdf->master_salt, MAX_SRTP_SALT_LEN);
+    kdf->evp = NULL;
+
+    return srtp_err_status_ok;
+}
+
+#else  /* if OPENSSL_KDF */
+
+/*
+ * srtp_kdf_t represents a key derivation function.  The SRTP
+ * default KDF is the only one implemented at present.
+ */
+typedef struct {
+    srtp_cipher_t *cipher; /* cipher used for key derivation  */
+} srtp_kdf_t;
+
+static srtp_err_status_t srtp_kdf_init(srtp_kdf_t *kdf,
+                                       const uint8_t *key,
+                                       int key_len)
+{
+    srtp_cipher_type_id_t cipher_id;
+    srtp_err_status_t stat;
+
+    switch (key_len) {
+    case SRTP_AES_ICM_256_KEY_LEN_WSALT:
+        cipher_id = SRTP_AES_ICM_256;
+        break;
+    case SRTP_AES_ICM_192_KEY_LEN_WSALT:
+        cipher_id = SRTP_AES_ICM_192;
+        break;
+    case SRTP_AES_ICM_128_KEY_LEN_WSALT:
+        cipher_id = SRTP_AES_ICM_128;
+        break;
+    default:
+        return srtp_err_status_bad_param;
+        break;
+    }
+
+    stat = srtp_crypto_kernel_alloc_cipher(cipher_id, &kdf->cipher, key_len, 0);
+    if (stat)
+        return stat;
+
+    stat = srtp_cipher_init(kdf->cipher, key);
+    if (stat) {
+        srtp_cipher_dealloc(kdf->cipher);
+        return stat;
+    }
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_kdf_generate(srtp_kdf_t *kdf,
+                                           srtp_prf_label label,
+                                           uint8_t *key,
+                                           unsigned int length)
+{
+    srtp_err_status_t status;
+    v128_t nonce;
+
+    /* set eigth octet of nonce to <label>, set the rest of it to zero */
+    v128_set_to_zero(&nonce);
+    nonce.v8[7] = label;
+
+    status = srtp_cipher_set_iv(kdf->cipher, (uint8_t *)&nonce,
+                                srtp_direction_encrypt);
+    if (status)
+        return status;
+
+    /* generate keystream output */
+    octet_string_set_to_zero(key, length);
+    status = srtp_cipher_encrypt(kdf->cipher, key, &length);
+    if (status)
+        return status;
+
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_kdf_clear(srtp_kdf_t *kdf)
+{
+    srtp_err_status_t status;
+    status = srtp_cipher_dealloc(kdf->cipher);
+    if (status)
+        return status;
+    kdf->cipher = NULL;
+    return srtp_err_status_ok;
+}
+#endif /* else OPENSSL_KDF */
+
+/*
+ *  end of key derivation functions
+ */
+
+/* Get the base key length corresponding to a given combined key+salt
+ * length for the given cipher.
+ * TODO: key and salt lengths should be separate fields in the policy.  */
+static inline int base_key_length(const srtp_cipher_type_t *cipher,
+                                  int key_length)
+{
+    switch (cipher->id) {
+    case SRTP_NULL_CIPHER:
+        return 0;
+    case SRTP_AES_ICM_128:
+    case SRTP_AES_ICM_192:
+    case SRTP_AES_ICM_256:
+        /* The legacy modes are derived from
+         * the configured key length on the policy */
+        return key_length - SRTP_SALT_LEN;
+    case SRTP_AES_GCM_128:
+        return key_length - SRTP_AEAD_SALT_LEN;
+    case SRTP_AES_GCM_256:
+        return key_length - SRTP_AEAD_SALT_LEN;
+    default:
+        return key_length;
+    }
+}
+
+/* Get the key length that the application should supply for the given cipher */
+static inline int full_key_length(const srtp_cipher_type_t *cipher)
+{
+    switch (cipher->id) {
+    case SRTP_NULL_CIPHER:
+    case SRTP_AES_ICM_128:
+        return SRTP_AES_ICM_128_KEY_LEN_WSALT;
+    case SRTP_AES_ICM_192:
+        return SRTP_AES_ICM_192_KEY_LEN_WSALT;
+    case SRTP_AES_ICM_256:
+        return SRTP_AES_ICM_256_KEY_LEN_WSALT;
+    case SRTP_AES_GCM_128:
+        return SRTP_AES_GCM_128_KEY_LEN_WSALT;
+    case SRTP_AES_GCM_256:
+        return SRTP_AES_GCM_256_KEY_LEN_WSALT;
+    default:
+        return 0;
+    }
+}
+
+unsigned int srtp_validate_policy_master_keys(const srtp_policy_t *policy)
+{
+    unsigned long i = 0;
+
+    if (policy->key == NULL) {
+        if (policy->num_master_keys <= 0)
+            return 0;
+
+        if (policy->num_master_keys > SRTP_MAX_NUM_MASTER_KEYS)
+            return 0;
+
+        for (i = 0; i < policy->num_master_keys; i++) {
+            if (policy->keys[i]->key == NULL)
+                return 0;
+            if (policy->keys[i]->mki_size > SRTP_MAX_MKI_LEN)
+                return 0;
+        }
+    }
+
+    return 1;
+}
+
+srtp_session_keys_t *srtp_get_session_keys_with_mki_index(
+    srtp_stream_ctx_t *stream,
+    unsigned int use_mki,
+    unsigned int mki_index)
+{
+    if (use_mki) {
+        if (mki_index >= stream->num_master_keys) {
+            return NULL;
+        }
+        return &stream->session_keys[mki_index];
+    }
+
+    return &stream->session_keys[0];
+}
+
+unsigned int srtp_inject_mki(uint8_t *mki_tag_location,
+                             srtp_session_keys_t *session_keys,
+                             unsigned int use_mki)
+{
+    unsigned int mki_size = 0;
+
+    if (use_mki) {
+        mki_size = session_keys->mki_size;
+
+        if (mki_size != 0) {
+            // Write MKI into memory
+            memcpy(mki_tag_location, session_keys->mki_id, mki_size);
+        }
+    }
+
+    return mki_size;
+}
+
+srtp_err_status_t srtp_stream_init_all_master_keys(
+    srtp_stream_ctx_t *srtp,
+    unsigned char *key,
+    srtp_master_key_t **keys,
+    const unsigned int max_master_keys)
+{
+    unsigned int i = 0;
+    srtp_err_status_t status = srtp_err_status_ok;
+    srtp_master_key_t single_master_key;
+
+    if (key != NULL) {
+        srtp->num_master_keys = 1;
+        single_master_key.key = key;
+        single_master_key.mki_id = NULL;
+        single_master_key.mki_size = 0;
+        status = srtp_stream_init_keys(srtp, &single_master_key, 0);
+    } else {
+        srtp->num_master_keys = max_master_keys;
+
+        for (i = 0; i < srtp->num_master_keys && i < SRTP_MAX_NUM_MASTER_KEYS;
+             i++) {
+            status = srtp_stream_init_keys(srtp, keys[i], i);
+
+            if (status) {
+                return status;
+            }
+        }
+    }
+
+    return status;
+}
+
+srtp_err_status_t srtp_stream_init_keys(srtp_stream_ctx_t *srtp,
+                                        srtp_master_key_t *master_key,
+                                        const unsigned int current_mki_index)
+{
+    srtp_err_status_t stat;
+    srtp_kdf_t kdf;
+    uint8_t tmp_key[MAX_SRTP_KEY_LEN];
+    int input_keylen, input_keylen_rtcp;
+    int kdf_keylen = 30, rtp_keylen, rtcp_keylen;
+    int rtp_base_key_len, rtp_salt_len;
+    int rtcp_base_key_len, rtcp_salt_len;
+    srtp_session_keys_t *session_keys = NULL;
+    unsigned char *key = master_key->key;
+
+    /* If RTP or RTCP have a key length > AES-128, assume matching kdf. */
+    /* TODO: kdf algorithm, master key length, and master salt length should
+     * be part of srtp_policy_t.
+    */
+    session_keys = &srtp->session_keys[current_mki_index];
+
+/* initialize key limit to maximum value */
+#ifdef NO_64BIT_MATH
+    {
+        uint64_t temp;
+        temp = make64(UINT_MAX, UINT_MAX);
+        srtp_key_limit_set(session_keys->limit, temp);
+    }
+#else
+    srtp_key_limit_set(session_keys->limit, 0xffffffffffffLL);
+#endif
+
+    if (master_key->mki_size != 0) {
+        session_keys->mki_id = srtp_crypto_alloc(master_key->mki_size);
+
+        if (session_keys->mki_id == NULL) {
+            return srtp_err_status_init_fail;
+        }
+        memcpy(session_keys->mki_id, master_key->mki_id, master_key->mki_size);
+    } else {
+        session_keys->mki_id = NULL;
+    }
+
+    session_keys->mki_size = master_key->mki_size;
+
+    input_keylen = full_key_length(session_keys->rtp_cipher->type);
+    input_keylen_rtcp = full_key_length(session_keys->rtcp_cipher->type);
+    if (input_keylen_rtcp > input_keylen) {
+        input_keylen = input_keylen_rtcp;
+    }
+
+    rtp_keylen = srtp_cipher_get_key_length(session_keys->rtp_cipher);
+    rtcp_keylen = srtp_cipher_get_key_length(session_keys->rtcp_cipher);
+    rtp_base_key_len =
+        base_key_length(session_keys->rtp_cipher->type, rtp_keylen);
+    rtp_salt_len = rtp_keylen - rtp_base_key_len;
+
+    if (rtp_keylen > kdf_keylen) {
+        kdf_keylen = 46; /* AES-CTR mode is always used for KDF */
+    }
+
+    if (rtcp_keylen > kdf_keylen) {
+        kdf_keylen = 46; /* AES-CTR mode is always used for KDF */
+    }
+
+    if (input_keylen > kdf_keylen) {
+        kdf_keylen = 46; /* AES-CTR mode is always used for KDF */
+    }
+
+    debug_print(mod_srtp, "input key len: %d", input_keylen);
+    debug_print(mod_srtp, "srtp key len: %d", rtp_keylen);
+    debug_print(mod_srtp, "srtcp key len: %d", rtcp_keylen);
+    debug_print(mod_srtp, "base key len: %d", rtp_base_key_len);
+    debug_print(mod_srtp, "kdf key len: %d", kdf_keylen);
+    debug_print(mod_srtp, "rtp salt len: %d", rtp_salt_len);
+
+    /*
+     * Make sure the key given to us is 'zero' appended.  GCM
+     * mode uses a shorter master SALT (96 bits), but still relies on
+     * the legacy CTR mode KDF, which uses a 112 bit master SALT.
+     */
+    memset(tmp_key, 0x0, MAX_SRTP_KEY_LEN);
+    memcpy(tmp_key, key, input_keylen);
+
+/* initialize KDF state     */
+#if defined(OPENSSL) && defined(OPENSSL_KDF)
+    stat = srtp_kdf_init(&kdf, (const uint8_t *)tmp_key, rtp_base_key_len,
+                         rtp_salt_len);
+#else
+    stat = srtp_kdf_init(&kdf, (const uint8_t *)tmp_key, kdf_keylen);
+#endif
+    if (stat) {
+        /* zeroize temp buffer */
+        octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+        return srtp_err_status_init_fail;
+    }
+
+    /* generate encryption key  */
+    stat = srtp_kdf_generate(&kdf, label_rtp_encryption, tmp_key,
+                             rtp_base_key_len);
+    if (stat) {
+        /* zeroize temp buffer */
+        octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+        return srtp_err_status_init_fail;
+    }
+    debug_print(mod_srtp, "cipher key: %s",
+                srtp_octet_string_hex_string(tmp_key, rtp_base_key_len));
+
+    /*
+     * if the cipher in the srtp context uses a salt, then we need
+     * to generate the salt value
+     */
+    if (rtp_salt_len > 0) {
+        debug_print0(mod_srtp, "found rtp_salt_len > 0, generating salt");
+
+        /* generate encryption salt, put after encryption key */
+        stat = srtp_kdf_generate(&kdf, label_rtp_salt,
+                                 tmp_key + rtp_base_key_len, rtp_salt_len);
+        if (stat) {
+            /* zeroize temp buffer */
+            octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+            return srtp_err_status_init_fail;
+        }
+        memcpy(session_keys->salt, tmp_key + rtp_base_key_len,
+               SRTP_AEAD_SALT_LEN);
+    }
+    if (rtp_salt_len > 0) {
+        debug_print(mod_srtp, "cipher salt: %s",
+                    srtp_octet_string_hex_string(tmp_key + rtp_base_key_len,
+                                                 rtp_salt_len));
+    }
+
+    /* initialize cipher */
+    stat = srtp_cipher_init(session_keys->rtp_cipher, tmp_key);
+    if (stat) {
+        /* zeroize temp buffer */
+        octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+        return srtp_err_status_init_fail;
+    }
+
+    if (session_keys->rtp_xtn_hdr_cipher) {
+        /* generate extensions header encryption key  */
+        int rtp_xtn_hdr_keylen;
+        int rtp_xtn_hdr_base_key_len;
+        int rtp_xtn_hdr_salt_len;
+        srtp_kdf_t tmp_kdf;
+        srtp_kdf_t *xtn_hdr_kdf;
+
+        if (session_keys->rtp_xtn_hdr_cipher->type !=
+            session_keys->rtp_cipher->type) {
+            /*
+             * With GCM ciphers, the header extensions are still encrypted using
+             * the corresponding ICM cipher.
+             * See https://tools.ietf.org/html/rfc7714#section-8.3
+             */
+            uint8_t tmp_xtn_hdr_key[MAX_SRTP_KEY_LEN];
+            rtp_xtn_hdr_keylen =
+                srtp_cipher_get_key_length(session_keys->rtp_xtn_hdr_cipher);
+            rtp_xtn_hdr_base_key_len = base_key_length(
+                session_keys->rtp_xtn_hdr_cipher->type, rtp_xtn_hdr_keylen);
+            rtp_xtn_hdr_salt_len =
+                rtp_xtn_hdr_keylen - rtp_xtn_hdr_base_key_len;
+            if (rtp_xtn_hdr_salt_len > rtp_salt_len) {
+                switch (session_keys->rtp_cipher->type->id) {
+                case SRTP_AES_GCM_128:
+                case SRTP_AES_GCM_256:
+                    /*
+                     * The shorter GCM salt is padded to the required ICM salt
+                     * length.
+                     */
+                    rtp_xtn_hdr_salt_len = rtp_salt_len;
+                    break;
+                default:
+                    /* zeroize temp buffer */
+                    octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+                    return srtp_err_status_bad_param;
+                }
+            }
+            memset(tmp_xtn_hdr_key, 0x0, MAX_SRTP_KEY_LEN);
+            memcpy(tmp_xtn_hdr_key, key,
+                   (rtp_xtn_hdr_base_key_len + rtp_xtn_hdr_salt_len));
+            xtn_hdr_kdf = &tmp_kdf;
+
+/* initialize KDF state */
+#if defined(OPENSSL) && defined(OPENSSL_KDF)
+            stat =
+                srtp_kdf_init(xtn_hdr_kdf, (const uint8_t *)tmp_xtn_hdr_key,
+                              rtp_xtn_hdr_base_key_len, rtp_xtn_hdr_salt_len);
+#else
+            stat = srtp_kdf_init(xtn_hdr_kdf, (const uint8_t *)tmp_xtn_hdr_key,
+                                 kdf_keylen);
+#endif
+            octet_string_set_to_zero(tmp_xtn_hdr_key, MAX_SRTP_KEY_LEN);
+            if (stat) {
+                /* zeroize temp buffer */
+                octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+                return srtp_err_status_init_fail;
+            }
+        } else {
+            /* Reuse main KDF. */
+            rtp_xtn_hdr_keylen = rtp_keylen;
+            rtp_xtn_hdr_base_key_len = rtp_base_key_len;
+            rtp_xtn_hdr_salt_len = rtp_salt_len;
+            xtn_hdr_kdf = &kdf;
+        }
+
+        stat = srtp_kdf_generate(xtn_hdr_kdf, label_rtp_header_encryption,
+                                 tmp_key, rtp_xtn_hdr_base_key_len);
+        if (stat) {
+            /* zeroize temp buffer */
+            octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+            return srtp_err_status_init_fail;
+        }
+        debug_print(
+            mod_srtp, "extensions cipher key: %s",
+            srtp_octet_string_hex_string(tmp_key, rtp_xtn_hdr_base_key_len));
+
+        /*
+         * if the cipher in the srtp context uses a salt, then we need
+         * to generate the salt value
+         */
+        if (rtp_xtn_hdr_salt_len > 0) {
+            debug_print0(mod_srtp,
+                         "found rtp_xtn_hdr_salt_len > 0, generating salt");
+
+            /* generate encryption salt, put after encryption key */
+            stat = srtp_kdf_generate(xtn_hdr_kdf, label_rtp_header_salt,
+                                     tmp_key + rtp_xtn_hdr_base_key_len,
+                                     rtp_xtn_hdr_salt_len);
+            if (stat) {
+                /* zeroize temp buffer */
+                octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+                return srtp_err_status_init_fail;
+            }
+        }
+        if (rtp_xtn_hdr_salt_len > 0) {
+            debug_print(
+                mod_srtp, "extensions cipher salt: %s",
+                srtp_octet_string_hex_string(tmp_key + rtp_xtn_hdr_base_key_len,
+                                             rtp_xtn_hdr_salt_len));
+        }
+
+        /* initialize extensions header cipher */
+        stat = srtp_cipher_init(session_keys->rtp_xtn_hdr_cipher, tmp_key);
+        if (stat) {
+            /* zeroize temp buffer */
+            octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+            return srtp_err_status_init_fail;
+        }
+
+        if (xtn_hdr_kdf != &kdf) {
+            /* release memory for custom header extension encryption kdf */
+            stat = srtp_kdf_clear(xtn_hdr_kdf);
+            if (stat) {
+                /* zeroize temp buffer */
+                octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+                return srtp_err_status_init_fail;
+            }
+        }
+    }
+
+    /* generate authentication key */
+    stat = srtp_kdf_generate(&kdf, label_rtp_msg_auth, tmp_key,
+                             srtp_auth_get_key_length(session_keys->rtp_auth));
+    if (stat) {
+        /* zeroize temp buffer */
+        octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+        return srtp_err_status_init_fail;
+    }
+    debug_print(mod_srtp, "auth key:   %s",
+                srtp_octet_string_hex_string(
+                    tmp_key, srtp_auth_get_key_length(session_keys->rtp_auth)));
+
+    /* initialize auth function */
+    stat = srtp_auth_init(session_keys->rtp_auth, tmp_key);
+    if (stat) {
+        /* zeroize temp buffer */
+        octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+        return srtp_err_status_init_fail;
+    }
+
+    /*
+     * ...now initialize SRTCP keys
+     */
+
+    rtcp_base_key_len =
+        base_key_length(session_keys->rtcp_cipher->type, rtcp_keylen);
+    rtcp_salt_len = rtcp_keylen - rtcp_base_key_len;
+    debug_print(mod_srtp, "rtcp salt len: %d", rtcp_salt_len);
+
+    /* generate encryption key  */
+    stat = srtp_kdf_generate(&kdf, label_rtcp_encryption, tmp_key,
+                             rtcp_base_key_len);
+    if (stat) {
+        /* zeroize temp buffer */
+        octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+        return srtp_err_status_init_fail;
+    }
+
+    /*
+     * if the cipher in the srtp context uses a salt, then we need
+     * to generate the salt value
+     */
+    if (rtcp_salt_len > 0) {
+        debug_print0(mod_srtp, "found rtcp_salt_len > 0, generating rtcp salt");
+
+        /* generate encryption salt, put after encryption key */
+        stat = srtp_kdf_generate(&kdf, label_rtcp_salt,
+                                 tmp_key + rtcp_base_key_len, rtcp_salt_len);
+        if (stat) {
+            /* zeroize temp buffer */
+            octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+            return srtp_err_status_init_fail;
+        }
+        memcpy(session_keys->c_salt, tmp_key + rtcp_base_key_len,
+               SRTP_AEAD_SALT_LEN);
+    }
+    debug_print(mod_srtp, "rtcp cipher key: %s",
+                srtp_octet_string_hex_string(tmp_key, rtcp_base_key_len));
+    if (rtcp_salt_len > 0) {
+        debug_print(mod_srtp, "rtcp cipher salt: %s",
+                    srtp_octet_string_hex_string(tmp_key + rtcp_base_key_len,
+                                                 rtcp_salt_len));
+    }
+
+    /* initialize cipher */
+    stat = srtp_cipher_init(session_keys->rtcp_cipher, tmp_key);
+    if (stat) {
+        /* zeroize temp buffer */
+        octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+        return srtp_err_status_init_fail;
+    }
+
+    /* generate authentication key */
+    stat = srtp_kdf_generate(&kdf, label_rtcp_msg_auth, tmp_key,
+                             srtp_auth_get_key_length(session_keys->rtcp_auth));
+    if (stat) {
+        /* zeroize temp buffer */
+        octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+        return srtp_err_status_init_fail;
+    }
+
+    debug_print(
+        mod_srtp, "rtcp auth key:   %s",
+        srtp_octet_string_hex_string(
+            tmp_key, srtp_auth_get_key_length(session_keys->rtcp_auth)));
+
+    /* initialize auth function */
+    stat = srtp_auth_init(session_keys->rtcp_auth, tmp_key);
+    if (stat) {
+        /* zeroize temp buffer */
+        octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+        return srtp_err_status_init_fail;
+    }
+
+    /* clear memory then return */
+    stat = srtp_kdf_clear(&kdf);
+    octet_string_set_to_zero(tmp_key, MAX_SRTP_KEY_LEN);
+    if (stat)
+        return srtp_err_status_init_fail;
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_stream_init(srtp_stream_ctx_t *srtp,
+                                   const srtp_policy_t *p)
+{
+    srtp_err_status_t err;
+
+    err = srtp_valid_policy(p);
+    if (err != srtp_err_status_ok) {
+        return err;
+    }
+
+    debug_print(mod_srtp, "initializing stream (SSRC: 0x%08x)", p->ssrc.value);
+
+    /* initialize replay database */
+    /*
+     * window size MUST be at least 64.  MAY be larger.  Values more than
+     * 2^15 aren't meaningful due to how extended sequence numbers are
+     * calculated.
+     * Let a window size of 0 imply the default value.
+     */
+
+    if (p->window_size != 0 &&
+        (p->window_size < 64 || p->window_size >= 0x8000))
+        return srtp_err_status_bad_param;
+
+    if (p->window_size != 0)
+        err = srtp_rdbx_init(&srtp->rtp_rdbx, p->window_size);
+    else
+        err = srtp_rdbx_init(&srtp->rtp_rdbx, 128);
+    if (err)
+        return err;
+
+    /* set the SSRC value */
+    srtp->ssrc = htonl(p->ssrc.value);
+
+    /* reset pending ROC */
+    srtp->pending_roc = 0;
+
+    /* set the security service flags */
+    srtp->rtp_services = p->rtp.sec_serv;
+    srtp->rtcp_services = p->rtcp.sec_serv;
+
+    /*
+     * set direction to unknown - this flag gets checked in srtp_protect(),
+     * srtp_unprotect(), srtp_protect_rtcp(), and srtp_unprotect_rtcp(), and
+     * gets set appropriately if it is set to unknown.
+     */
+    srtp->direction = dir_unknown;
+
+    /* initialize SRTCP replay database */
+    srtp_rdb_init(&srtp->rtcp_rdb);
+
+    /* initialize allow_repeat_tx */
+    /* guard against uninitialized memory: allow only 0 or 1 here */
+    if (p->allow_repeat_tx != 0 && p->allow_repeat_tx != 1) {
+        srtp_rdbx_dealloc(&srtp->rtp_rdbx);
+        return srtp_err_status_bad_param;
+    }
+    srtp->allow_repeat_tx = p->allow_repeat_tx;
+
+    /* DAM - no RTCP key limit at present */
+
+    /* initialize keys */
+    err = srtp_stream_init_all_master_keys(srtp, p->key, p->keys,
+                                           p->num_master_keys);
+    if (err) {
+        srtp_rdbx_dealloc(&srtp->rtp_rdbx);
+        return err;
+    }
+
+    return srtp_err_status_ok;
+}
+
+/*
+ * srtp_event_reporter is an event handler function that merely
+ * reports the events that are reported by the callbacks
+ */
+
+void srtp_event_reporter(srtp_event_data_t *data)
+{
+    srtp_err_report(srtp_err_level_warning, "srtp: in stream 0x%x: ",
+                    data->ssrc);
+
+    switch (data->event) {
+    case event_ssrc_collision:
+        srtp_err_report(srtp_err_level_warning, "\tSSRC collision\n");
+        break;
+    case event_key_soft_limit:
+        srtp_err_report(srtp_err_level_warning,
+                        "\tkey usage soft limit reached\n");
+        break;
+    case event_key_hard_limit:
+        srtp_err_report(srtp_err_level_warning,
+                        "\tkey usage hard limit reached\n");
+        break;
+    case event_packet_index_limit:
+        srtp_err_report(srtp_err_level_warning,
+                        "\tpacket index limit reached\n");
+        break;
+    default:
+        srtp_err_report(srtp_err_level_warning,
+                        "\tunknown event reported to handler\n");
+    }
+}
+
+/*
+ * srtp_event_handler is a global variable holding a pointer to the
+ * event handler function; this function is called for any unexpected
+ * event that needs to be handled out of the SRTP data path.  see
+ * srtp_event_t in srtp.h for more info
+ *
+ * it is okay to set srtp_event_handler to NULL, but we set
+ * it to the srtp_event_reporter.
+ */
+
+static srtp_event_handler_func_t *srtp_event_handler = srtp_event_reporter;
+
+srtp_err_status_t srtp_install_event_handler(srtp_event_handler_func_t func)
+{
+    /*
+     * note that we accept NULL arguments intentionally - calling this
+     * function with a NULL arguments removes an event handler that's
+     * been previously installed
+     */
+
+    /* set global event handling function */
+    srtp_event_handler = func;
+    return srtp_err_status_ok;
+}
+
+/*
+ * Check if the given extension header id is / should be encrypted.
+ * Returns 1 if yes, otherwise 0.
+ */
+static int srtp_protect_extension_header(srtp_stream_ctx_t *stream, int id)
+{
+    int *enc_xtn_hdr = stream->enc_xtn_hdr;
+    int count = stream->enc_xtn_hdr_count;
+
+    if (!enc_xtn_hdr || count <= 0) {
+        return 0;
+    }
+
+    while (count > 0) {
+        if (*enc_xtn_hdr == id) {
+            return 1;
+        }
+
+        enc_xtn_hdr++;
+        count--;
+    }
+    return 0;
+}
+
+/*
+ * extensions header encryption RFC 6904
+ */
+static srtp_err_status_t srtp_process_header_encryption(
+    srtp_stream_ctx_t *stream,
+    srtp_hdr_xtnd_t *xtn_hdr,
+    srtp_session_keys_t *session_keys)
+{
+    srtp_err_status_t status;
+    uint8_t keystream[257]; /* Maximum 2 bytes header + 255 bytes data. */
+    int keystream_pos;
+    uint8_t *xtn_hdr_data = ((uint8_t *)xtn_hdr) + octets_in_rtp_extn_hdr;
+    uint8_t *xtn_hdr_end =
+        xtn_hdr_data + (ntohs(xtn_hdr->length) * sizeof(uint32_t));
+
+    if (ntohs(xtn_hdr->profile_specific) == 0xbede) {
+        /* RFC 5285, section 4.2. One-Byte Header */
+        while (xtn_hdr_data < xtn_hdr_end) {
+            uint8_t xid = (*xtn_hdr_data & 0xf0) >> 4;
+            unsigned int xlen = (*xtn_hdr_data & 0x0f) + 1;
+            uint32_t xlen_with_header = 1 + xlen;
+            xtn_hdr_data++;
+
+            if (xtn_hdr_data + xlen > xtn_hdr_end)
+                return srtp_err_status_parse_err;
+
+            if (xid == 15) {
+                /* found header 15, stop further processing. */
+                break;
+            }
+
+            status = srtp_cipher_output(session_keys->rtp_xtn_hdr_cipher,
+                                        keystream, &xlen_with_header);
+            if (status)
+                return srtp_err_status_cipher_fail;
+
+            if (srtp_protect_extension_header(stream, xid)) {
+                keystream_pos = 1;
+                while (xlen > 0) {
+                    *xtn_hdr_data ^= keystream[keystream_pos++];
+                    xtn_hdr_data++;
+                    xlen--;
+                }
+            } else {
+                xtn_hdr_data += xlen;
+            }
+
+            /* skip padding bytes. */
+            while (xtn_hdr_data < xtn_hdr_end && *xtn_hdr_data == 0) {
+                xtn_hdr_data++;
+            }
+        }
+    } else if ((ntohs(xtn_hdr->profile_specific) & 0xfff0) == 0x1000) {
+        /* RFC 5285, section 4.3. Two-Byte Header */
+        while (xtn_hdr_data + 1 < xtn_hdr_end) {
+            uint8_t xid = *xtn_hdr_data;
+            unsigned int xlen = *(xtn_hdr_data + 1);
+            uint32_t xlen_with_header = 2 + xlen;
+            xtn_hdr_data += 2;
+
+            if (xtn_hdr_data + xlen > xtn_hdr_end)
+                return srtp_err_status_parse_err;
+
+            status = srtp_cipher_output(session_keys->rtp_xtn_hdr_cipher,
+                                        keystream, &xlen_with_header);
+            if (status)
+                return srtp_err_status_cipher_fail;
+
+            if (xlen > 0 && srtp_protect_extension_header(stream, xid)) {
+                keystream_pos = 2;
+                while (xlen > 0) {
+                    *xtn_hdr_data ^= keystream[keystream_pos++];
+                    xtn_hdr_data++;
+                    xlen--;
+                }
+            } else {
+                xtn_hdr_data += xlen;
+            }
+
+            /* skip padding bytes. */
+            while (xtn_hdr_data < xtn_hdr_end && *xtn_hdr_data == 0) {
+                xtn_hdr_data++;
+            }
+        }
+    } else {
+        /* unsupported extension header format. */
+        return srtp_err_status_parse_err;
+    }
+
+    return srtp_err_status_ok;
+}
+
+/*
+ * AEAD uses a new IV formation method.  This function implements
+ * section 8.1. (SRTP IV Formation for AES-GCM) of RFC7714.
+ * The calculation is defined as, where (+) is the xor operation:
+ *
+ *
+ *              0  0  0  0  0  0  0  0  0  0  1  1
+ *              0  1  2  3  4  5  6  7  8  9  0  1
+ *            +--+--+--+--+--+--+--+--+--+--+--+--+
+ *            |00|00|    SSRC   |     ROC   | SEQ |---+
+ *            +--+--+--+--+--+--+--+--+--+--+--+--+   |
+ *                                                    |
+ *            +--+--+--+--+--+--+--+--+--+--+--+--+   |
+ *            |         Encryption Salt           |->(+)
+ *            +--+--+--+--+--+--+--+--+--+--+--+--+   |
+ *                                                    |
+ *            +--+--+--+--+--+--+--+--+--+--+--+--+   |
+ *            |       Initialization Vector       |<--+
+ *            +--+--+--+--+--+--+--+--+--+--+--+--+*
+ *
+ * Input:  *session_keys - pointer to SRTP stream context session keys,
+ *                         used to retrieve the SALT
+ *         *iv     - Pointer to receive the calculated IV
+ *         *seq    - The ROC and SEQ value to use for the
+ *                   IV calculation.
+ *         *hdr    - The RTP header, used to get the SSRC value
+ *
+ */
+
+static void srtp_calc_aead_iv(srtp_session_keys_t *session_keys,
+                              v128_t *iv,
+                              srtp_xtd_seq_num_t *seq,
+                              srtp_hdr_t *hdr)
+{
+    v128_t in;
+    v128_t salt;
+
+#ifdef NO_64BIT_MATH
+    uint32_t local_roc = ((high32(*seq) << 16) | (low32(*seq) >> 16));
+    uint16_t local_seq = (uint16_t)(low32(*seq));
+#else
+    uint32_t local_roc = (uint32_t)(*seq >> 16);
+    uint16_t local_seq = (uint16_t)*seq;
+#endif
+
+    memset(&in, 0, sizeof(v128_t));
+    memset(&salt, 0, sizeof(v128_t));
+
+    in.v16[5] = htons(local_seq);
+    local_roc = htonl(local_roc);
+    memcpy(&in.v16[3], &local_roc, sizeof(local_roc));
+
+    /*
+     * Copy in the RTP SSRC value
+     */
+    memcpy(&in.v8[2], &hdr->ssrc, 4);
+    debug_print(mod_srtp, "Pre-salted RTP IV = %s\n", v128_hex_string(&in));
+
+    /*
+     * Get the SALT value from the context
+     */
+    memcpy(salt.v8, session_keys->salt, SRTP_AEAD_SALT_LEN);
+    debug_print(mod_srtp, "RTP SALT = %s\n", v128_hex_string(&salt));
+
+    /*
+     * Finally, apply tyhe SALT to the input
+     */
+    v128_xor(iv, &in, &salt);
+}
+
+srtp_session_keys_t *srtp_get_session_keys(srtp_stream_ctx_t *stream,
+                                           uint8_t *hdr,
+                                           const unsigned int *pkt_octet_len,
+                                           unsigned int *mki_size)
+{
+    unsigned int base_mki_start_location = *pkt_octet_len;
+    unsigned int mki_start_location = 0;
+    unsigned int tag_len = 0;
+    unsigned int i = 0;
+
+    // Determine the authentication tag size
+    if (stream->session_keys[0].rtp_cipher->algorithm == SRTP_AES_GCM_128 ||
+        stream->session_keys[0].rtp_cipher->algorithm == SRTP_AES_GCM_256) {
+        tag_len = 0;
+    } else {
+        tag_len = srtp_auth_get_tag_length(stream->session_keys[0].rtp_auth);
+    }
+
+    if (tag_len > base_mki_start_location) {
+        *mki_size = 0;
+        return NULL;
+    }
+
+    base_mki_start_location -= tag_len;
+
+    for (i = 0; i < stream->num_master_keys; i++) {
+        if (stream->session_keys[i].mki_size != 0 &&
+            stream->session_keys[i].mki_size <= base_mki_start_location) {
+            *mki_size = stream->session_keys[i].mki_size;
+            mki_start_location = base_mki_start_location - *mki_size;
+
+            if (memcmp(hdr + mki_start_location, stream->session_keys[i].mki_id,
+                       *mki_size) == 0) {
+                return &stream->session_keys[i];
+            }
+        }
+    }
+
+    *mki_size = 0;
+    return NULL;
+}
+
+static srtp_err_status_t srtp_estimate_index(srtp_rdbx_t *rdbx,
+                                             uint32_t roc,
+                                             srtp_xtd_seq_num_t *est,
+                                             srtp_sequence_number_t seq,
+                                             int *delta)
+{
+#ifdef NO_64BIT_MATH
+    uint32_t internal_pkt_idx_reduced;
+    uint32_t external_pkt_idx_reduced;
+    uint32_t internal_roc;
+    uint32_t roc_difference;
+#endif
+
+#ifdef NO_64BIT_MATH
+    *est = (srtp_xtd_seq_num_t)make64(roc >> 16, (roc << 16) | seq);
+    *delta = low32(est) - rdbx->index;
+#else
+    *est = (srtp_xtd_seq_num_t)(((uint64_t)roc) << 16) | seq;
+    *delta = (int)(*est - rdbx->index);
+#endif
+
+    if (*est > rdbx->index) {
+#ifdef NO_64BIT_MATH
+        internal_roc = (uint32_t)(rdbx->index >> 16);
+        roc_difference = roc - internal_roc;
+        if (roc_difference > 1) {
+            *delta = 0;
+            return srtp_err_status_pkt_idx_adv;
+        }
+
+        internal_pkt_idx_reduced = (uint32_t)(rdbx->index & 0xFFFF);
+        external_pkt_idx_reduced = (uint32_t)((roc_difference << 16) | seq);
+
+        if (external_pkt_idx_reduced - internal_pkt_idx_reduced >
+            seq_num_median) {
+            *delta = 0;
+            return srtp_err_status_pkt_idx_adv;
+        }
+#else
+        if (*est - rdbx->index > seq_num_median) {
+            *delta = 0;
+            return srtp_err_status_pkt_idx_adv;
+        }
+#endif
+    } else if (*est < rdbx->index) {
+#ifdef NO_64BIT_MATH
+
+        internal_roc = (uint32_t)(rdbx->index >> 16);
+        roc_difference = internal_roc - roc;
+        if (roc_difference > 1) {
+            *delta = 0;
+            return srtp_err_status_pkt_idx_adv;
+        }
+
+        internal_pkt_idx_reduced =
+            (uint32_t)((roc_difference << 16) | rdbx->index & 0xFFFF);
+        external_pkt_idx_reduced = (uint32_t)(seq);
+
+        if (internal_pkt_idx_reduced - external_pkt_idx_reduced >
+            seq_num_median) {
+            *delta = 0;
+            return srtp_err_status_pkt_idx_old;
+        }
+#else
+        if (rdbx->index - *est > seq_num_median) {
+            *delta = 0;
+            return srtp_err_status_pkt_idx_old;
+        }
+#endif
+    }
+
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_get_est_pkt_index(srtp_hdr_t *hdr,
+                                                srtp_stream_ctx_t *stream,
+                                                srtp_xtd_seq_num_t *est,
+                                                int *delta)
+{
+    srtp_err_status_t result = srtp_err_status_ok;
+
+    if (stream->pending_roc) {
+        result = srtp_estimate_index(&stream->rtp_rdbx, stream->pending_roc,
+                                     est, ntohs(hdr->seq), delta);
+    } else {
+        /* estimate packet index from seq. num. in header */
+        *delta =
+            srtp_rdbx_estimate_index(&stream->rtp_rdbx, est, ntohs(hdr->seq));
+    }
+
+#ifdef NO_64BIT_MATH
+    debug_print2(mod_srtp, "estimated u_packet index: %08x%08x", high32(*est),
+                 low32(*est));
+#else
+    debug_print(mod_srtp, "estimated u_packet index: %016" PRIx64, *est);
+#endif
+    return result;
+}
+
+/*
+ * This function handles outgoing SRTP packets while in AEAD mode,
+ * which currently supports AES-GCM encryption.  All packets are
+ * encrypted and authenticated.
+ */
+static srtp_err_status_t srtp_protect_aead(srtp_ctx_t *ctx,
+                                           srtp_stream_ctx_t *stream,
+                                           void *rtp_hdr,
+                                           unsigned int *pkt_octet_len,
+                                           srtp_session_keys_t *session_keys,
+                                           unsigned int use_mki)
+{
+    srtp_hdr_t *hdr = (srtp_hdr_t *)rtp_hdr;
+    uint32_t *enc_start;    /* pointer to start of encrypted portion  */
+    int enc_octet_len = 0;  /* number of octets in encrypted portion  */
+    srtp_xtd_seq_num_t est; /* estimated xtd_seq_num_t of *hdr        */
+    int delta;              /* delta of local pkt idx and that in hdr */
+    srtp_err_status_t status;
+    uint32_t tag_len;
+    v128_t iv;
+    unsigned int aad_len;
+    srtp_hdr_xtnd_t *xtn_hdr = NULL;
+    unsigned int mki_size = 0;
+    uint8_t *mki_location = NULL;
+
+    debug_print0(mod_srtp, "function srtp_protect_aead");
+
+    /*
+     * update the key usage limit, and check it to make sure that we
+     * didn't just hit either the soft limit or the hard limit, and call
+     * the event handler if we hit either.
+     */
+    switch (srtp_key_limit_update(session_keys->limit)) {
+    case srtp_key_event_normal:
+        break;
+    case srtp_key_event_hard_limit:
+        srtp_handle_event(ctx, stream, event_key_hard_limit);
+        return srtp_err_status_key_expired;
+    case srtp_key_event_soft_limit:
+    default:
+        srtp_handle_event(ctx, stream, event_key_soft_limit);
+        break;
+    }
+
+    /* get tag length from stream */
+    tag_len = srtp_auth_get_tag_length(session_keys->rtp_auth);
+
+    /*
+     * find starting point for encryption and length of data to be
+     * encrypted - the encrypted portion starts after the rtp header
+     * extension, if present; otherwise, it starts after the last csrc,
+     * if any are present
+     */
+    enc_start = (uint32_t *)hdr + uint32s_in_rtp_header + hdr->cc;
+    if (hdr->x == 1) {
+        xtn_hdr = (srtp_hdr_xtnd_t *)enc_start;
+        enc_start += (ntohs(xtn_hdr->length) + 1);
+    }
+    /* note: the passed size is without the auth tag */
+    if (!((uint8_t *)enc_start <= (uint8_t *)hdr + *pkt_octet_len))
+        return srtp_err_status_parse_err;
+    enc_octet_len =
+        (int)(*pkt_octet_len - ((uint8_t *)enc_start - (uint8_t *)hdr));
+    if (enc_octet_len < 0)
+        return srtp_err_status_parse_err;
+
+    /*
+     * estimate the packet index using the start of the replay window
+     * and the sequence number from the header
+     */
+    delta = srtp_rdbx_estimate_index(&stream->rtp_rdbx, &est, ntohs(hdr->seq));
+    status = srtp_rdbx_check(&stream->rtp_rdbx, delta);
+    if (status) {
+        if (status != srtp_err_status_replay_fail || !stream->allow_repeat_tx) {
+            return status; /* we've been asked to reuse an index */
+        }
+    } else {
+        srtp_rdbx_add_index(&stream->rtp_rdbx, delta);
+    }
+
+#ifdef NO_64BIT_MATH
+    debug_print2(mod_srtp, "estimated packet index: %08x%08x", high32(est),
+                 low32(est));
+#else
+    debug_print(mod_srtp, "estimated packet index: %016" PRIx64, est);
+#endif
+
+    /*
+     * AEAD uses a new IV formation method
+     */
+    srtp_calc_aead_iv(session_keys, &iv, &est, hdr);
+/* shift est, put into network byte order */
+#ifdef NO_64BIT_MATH
+    est = be64_to_cpu(
+        make64((high32(est) << 16) | (low32(est) >> 16), low32(est) << 16));
+#else
+    est = be64_to_cpu(est << 16);
+#endif
+
+    status = srtp_cipher_set_iv(session_keys->rtp_cipher, (uint8_t *)&iv,
+                                srtp_direction_encrypt);
+    if (!status && session_keys->rtp_xtn_hdr_cipher) {
+        iv.v32[0] = 0;
+        iv.v32[1] = hdr->ssrc;
+        iv.v64[1] = est;
+        status = srtp_cipher_set_iv(session_keys->rtp_xtn_hdr_cipher,
+                                    (uint8_t *)&iv, srtp_direction_encrypt);
+    }
+    if (status) {
+        return srtp_err_status_cipher_fail;
+    }
+
+    if (xtn_hdr && session_keys->rtp_xtn_hdr_cipher) {
+        /*
+         * extensions header encryption RFC 6904
+         */
+        status = srtp_process_header_encryption(stream, xtn_hdr, session_keys);
+        if (status) {
+            return status;
+        }
+    }
+
+    /*
+     * Set the AAD over the RTP header
+     */
+    aad_len = (uint8_t *)enc_start - (uint8_t *)hdr;
+    status =
+        srtp_cipher_set_aad(session_keys->rtp_cipher, (uint8_t *)hdr, aad_len);
+    if (status) {
+        return (srtp_err_status_cipher_fail);
+    }
+
+    /* Encrypt the payload  */
+    status = srtp_cipher_encrypt(session_keys->rtp_cipher, (uint8_t *)enc_start,
+                                 (unsigned int *)&enc_octet_len);
+    if (status) {
+        return srtp_err_status_cipher_fail;
+    }
+    /*
+     * If we're doing GCM, we need to get the tag
+     * and append that to the output
+     */
+    status =
+        srtp_cipher_get_tag(session_keys->rtp_cipher,
+                            (uint8_t *)enc_start + enc_octet_len, &tag_len);
+    if (status) {
+        return (srtp_err_status_cipher_fail);
+    }
+
+    mki_location = (uint8_t *)hdr + *pkt_octet_len + tag_len;
+    mki_size = srtp_inject_mki(mki_location, session_keys, use_mki);
+
+    /* increase the packet length by the length of the auth tag */
+    *pkt_octet_len += tag_len;
+
+    /* increase the packet length by the length of the mki_size */
+    *pkt_octet_len += mki_size;
+
+    return srtp_err_status_ok;
+}
+
+/*
+ * This function handles incoming SRTP packets while in AEAD mode,
+ * which currently supports AES-GCM encryption.  All packets are
+ * encrypted and authenticated.  Note, the auth tag is at the end
+ * of the packet stream and is automatically checked by GCM
+ * when decrypting the payload.
+ */
+static srtp_err_status_t srtp_unprotect_aead(srtp_ctx_t *ctx,
+                                             srtp_stream_ctx_t *stream,
+                                             int delta,
+                                             srtp_xtd_seq_num_t est,
+                                             void *srtp_hdr,
+                                             unsigned int *pkt_octet_len,
+                                             srtp_session_keys_t *session_keys,
+                                             unsigned int mki_size)
+{
+    srtp_hdr_t *hdr = (srtp_hdr_t *)srtp_hdr;
+    uint32_t *enc_start;            /* pointer to start of encrypted portion  */
+    unsigned int enc_octet_len = 0; /* number of octets in encrypted portion */
+    v128_t iv;
+    srtp_err_status_t status;
+    int tag_len;
+    unsigned int aad_len;
+    srtp_hdr_xtnd_t *xtn_hdr = NULL;
+
+    debug_print0(mod_srtp, "function srtp_unprotect_aead");
+
+#ifdef NO_64BIT_MATH
+    debug_print2(mod_srtp, "estimated u_packet index: %08x%08x", high32(est),
+                 low32(est));
+#else
+    debug_print(mod_srtp, "estimated u_packet index: %016" PRIx64, est);
+#endif
+
+    /* get tag length from stream */
+    tag_len = srtp_auth_get_tag_length(session_keys->rtp_auth);
+
+    /*
+     * AEAD uses a new IV formation method
+     */
+    srtp_calc_aead_iv(session_keys, &iv, &est, hdr);
+    status = srtp_cipher_set_iv(session_keys->rtp_cipher, (uint8_t *)&iv,
+                                srtp_direction_decrypt);
+    if (!status && session_keys->rtp_xtn_hdr_cipher) {
+        iv.v32[0] = 0;
+        iv.v32[1] = hdr->ssrc;
+#ifdef NO_64BIT_MATH
+        iv.v64[1] = be64_to_cpu(
+            make64((high32(est) << 16) | (low32(est) >> 16), low32(est) << 16));
+#else
+        iv.v64[1] = be64_to_cpu(est << 16);
+#endif
+        status = srtp_cipher_set_iv(session_keys->rtp_xtn_hdr_cipher,
+                                    (uint8_t *)&iv, srtp_direction_encrypt);
+    }
+    if (status) {
+        return srtp_err_status_cipher_fail;
+    }
+
+    /*
+     * find starting point for decryption and length of data to be
+     * decrypted - the encrypted portion starts after the rtp header
+     * extension, if present; otherwise, it starts after the last csrc,
+     * if any are present
+     */
+    enc_start = (uint32_t *)hdr + uint32s_in_rtp_header + hdr->cc;
+    if (hdr->x == 1) {
+        xtn_hdr = (srtp_hdr_xtnd_t *)enc_start;
+        enc_start += (ntohs(xtn_hdr->length) + 1);
+    }
+    if (!((uint8_t *)enc_start <=
+          (uint8_t *)hdr + (*pkt_octet_len - tag_len - mki_size)))
+        return srtp_err_status_parse_err;
+    /*
+     * We pass the tag down to the cipher when doing GCM mode
+     */
+    enc_octet_len = (unsigned int)(*pkt_octet_len - mki_size -
+                                   ((uint8_t *)enc_start - (uint8_t *)hdr));
+
+    /*
+     * Sanity check the encrypted payload length against
+     * the tag size.  It must always be at least as large
+     * as the tag length.
+     */
+    if (enc_octet_len < (unsigned int)tag_len) {
+        return srtp_err_status_cipher_fail;
+    }
+
+    /*
+     * update the key usage limit, and check it to make sure that we
+     * didn't just hit either the soft limit or the hard limit, and call
+     * the event handler if we hit either.
+     */
+    switch (srtp_key_limit_update(session_keys->limit)) {
+    case srtp_key_event_normal:
+        break;
+    case srtp_key_event_soft_limit:
+        srtp_handle_event(ctx, stream, event_key_soft_limit);
+        break;
+    case srtp_key_event_hard_limit:
+        srtp_handle_event(ctx, stream, event_key_hard_limit);
+        return srtp_err_status_key_expired;
+    default:
+        break;
+    }
+
+    /*
+     * Set the AAD for AES-GCM, which is the RTP header
+     */
+    aad_len = (uint8_t *)enc_start - (uint8_t *)hdr;
+    status =
+        srtp_cipher_set_aad(session_keys->rtp_cipher, (uint8_t *)hdr, aad_len);
+    if (status) {
+        return (srtp_err_status_cipher_fail);
+    }
+
+    /* Decrypt the ciphertext.  This also checks the auth tag based
+     * on the AAD we just specified above */
+    status = srtp_cipher_decrypt(session_keys->rtp_cipher, (uint8_t *)enc_start,
+                                 &enc_octet_len);
+    if (status) {
+        return status;
+    }
+
+    if (xtn_hdr && session_keys->rtp_xtn_hdr_cipher) {
+        /*
+         * extensions header encryption RFC 6904
+         */
+        status = srtp_process_header_encryption(stream, xtn_hdr, session_keys);
+        if (status) {
+            return status;
+        }
+    }
+
+    /*
+     * verify that stream is for received traffic - this check will
+     * detect SSRC collisions, since a stream that appears in both
+     * srtp_protect() and srtp_unprotect() will fail this test in one of
+     * those functions.
+     *
+     * we do this check *after* the authentication check, so that the
+     * latter check will catch any attempts to fool us into thinking
+     * that we've got a collision
+     */
+    if (stream->direction != dir_srtp_receiver) {
+        if (stream->direction == dir_unknown) {
+            stream->direction = dir_srtp_receiver;
+        } else {
+            srtp_handle_event(ctx, stream, event_ssrc_collision);
+        }
+    }
+
+    /*
+     * if the stream is a 'provisional' one, in which the template context
+     * is used, then we need to allocate a new stream at this point, since
+     * the authentication passed
+     */
+    if (stream == ctx->stream_template) {
+        srtp_stream_ctx_t *new_stream;
+
+        /*
+         * allocate and initialize a new stream
+         *
+         * note that we indicate failure if we can't allocate the new
+         * stream, and some implementations will want to not return
+         * failure here
+         */
+        status =
+            srtp_stream_clone(ctx->stream_template, hdr->ssrc, &new_stream);
+        if (status) {
+            return status;
+        }
+
+        /* add new stream to the head of the stream_list */
+        new_stream->next = ctx->stream_list;
+        ctx->stream_list = new_stream;
+
+        /* set stream (the pointer used in this function) */
+        stream = new_stream;
+    }
+
+    /*
+     * the message authentication function passed, so add the packet
+     * index into the replay database
+     */
+    srtp_rdbx_add_index(&stream->rtp_rdbx, delta);
+
+    /* decrease the packet length by the length of the auth tag */
+    *pkt_octet_len -= tag_len;
+
+    /* decrease the packet length by the length of the mki_size */
+    *pkt_octet_len -= mki_size;
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_protect(srtp_ctx_t *ctx,
+                               void *rtp_hdr,
+                               int *pkt_octet_len)
+{
+    return srtp_protect_mki(ctx, rtp_hdr, pkt_octet_len, 0, 0);
+}
+
+srtp_err_status_t srtp_protect_mki(srtp_ctx_t *ctx,
+                                   void *rtp_hdr,
+                                   int *pkt_octet_len,
+                                   unsigned int use_mki,
+                                   unsigned int mki_index)
+{
+    srtp_hdr_t *hdr = (srtp_hdr_t *)rtp_hdr;
+    uint32_t *enc_start;      /* pointer to start of encrypted portion  */
+    uint32_t *auth_start;     /* pointer to start of auth. portion      */
+    int enc_octet_len = 0;    /* number of octets in encrypted portion  */
+    srtp_xtd_seq_num_t est;   /* estimated xtd_seq_num_t of *hdr        */
+    int delta;                /* delta of local pkt idx and that in hdr */
+    uint8_t *auth_tag = NULL; /* location of auth_tag within packet     */
+    srtp_err_status_t status;
+    int tag_len;
+    srtp_stream_ctx_t *stream;
+    uint32_t prefix_len;
+    srtp_hdr_xtnd_t *xtn_hdr = NULL;
+    unsigned int mki_size = 0;
+    srtp_session_keys_t *session_keys = NULL;
+    uint8_t *mki_location = NULL;
+    int advance_packet_index = 0;
+
+    debug_print0(mod_srtp, "function srtp_protect");
+
+    /* we assume the hdr is 32-bit aligned to start */
+
+    /* Verify RTP header */
+    status = srtp_validate_rtp_header(rtp_hdr, pkt_octet_len);
+    if (status)
+        return status;
+
+    /* check the packet length - it must at least contain a full header */
+    if (*pkt_octet_len < octets_in_rtp_header)
+        return srtp_err_status_bad_param;
+
+    /*
+     * look up ssrc in srtp_stream list, and process the packet with
+     * the appropriate stream.  if we haven't seen this stream before,
+     * there's a template key for this srtp_session, and the cipher
+     * supports key-sharing, then we assume that a new stream using
+     * that key has just started up
+     */
+    stream = srtp_get_stream(ctx, hdr->ssrc);
+    if (stream == NULL) {
+        if (ctx->stream_template != NULL) {
+            srtp_stream_ctx_t *new_stream;
+
+            /* allocate and initialize a new stream */
+            status =
+                srtp_stream_clone(ctx->stream_template, hdr->ssrc, &new_stream);
+            if (status)
+                return status;
+
+            /* add new stream to the head of the stream_list */
+            new_stream->next = ctx->stream_list;
+            ctx->stream_list = new_stream;
+
+            /* set direction to outbound */
+            new_stream->direction = dir_srtp_sender;
+
+            /* set stream (the pointer used in this function) */
+            stream = new_stream;
+        } else {
+            /* no template stream, so we return an error */
+            return srtp_err_status_no_ctx;
+        }
+    }
+
+    /*
+     * verify that stream is for sending traffic - this check will
+     * detect SSRC collisions, since a stream that appears in both
+     * srtp_protect() and srtp_unprotect() will fail this test in one of
+     * those functions.
+     */
+
+    if (stream->direction != dir_srtp_sender) {
+        if (stream->direction == dir_unknown) {
+            stream->direction = dir_srtp_sender;
+        } else {
+            srtp_handle_event(ctx, stream, event_ssrc_collision);
+        }
+    }
+
+    session_keys =
+        srtp_get_session_keys_with_mki_index(stream, use_mki, mki_index);
+
+    if (session_keys == NULL)
+        return srtp_err_status_bad_mki;
+
+    /*
+     * Check if this is an AEAD stream (GCM mode).  If so, then dispatch
+     * the request to our AEAD handler.
+     */
+    if (session_keys->rtp_cipher->algorithm == SRTP_AES_GCM_128 ||
+        session_keys->rtp_cipher->algorithm == SRTP_AES_GCM_256) {
+        return srtp_protect_aead(ctx, stream, rtp_hdr,
+                                 (unsigned int *)pkt_octet_len, session_keys,
+                                 use_mki);
+    }
+
+    /*
+     * update the key usage limit, and check it to make sure that we
+     * didn't just hit either the soft limit or the hard limit, and call
+     * the event handler if we hit either.
+     */
+    switch (srtp_key_limit_update(session_keys->limit)) {
+    case srtp_key_event_normal:
+        break;
+    case srtp_key_event_soft_limit:
+        srtp_handle_event(ctx, stream, event_key_soft_limit);
+        break;
+    case srtp_key_event_hard_limit:
+        srtp_handle_event(ctx, stream, event_key_hard_limit);
+        return srtp_err_status_key_expired;
+    default:
+        break;
+    }
+
+    /* get tag length from stream */
+    tag_len = srtp_auth_get_tag_length(session_keys->rtp_auth);
+
+    /*
+     * find starting point for encryption and length of data to be
+     * encrypted - the encrypted portion starts after the rtp header
+     * extension, if present; otherwise, it starts after the last csrc,
+     * if any are present
+     *
+     * if we're not providing confidentiality, set enc_start to NULL
+     */
+    if (stream->rtp_services & sec_serv_conf) {
+        enc_start = (uint32_t *)hdr + uint32s_in_rtp_header + hdr->cc;
+        if (hdr->x == 1) {
+            xtn_hdr = (srtp_hdr_xtnd_t *)enc_start;
+            enc_start += (ntohs(xtn_hdr->length) + 1);
+        }
+        /* note: the passed size is without the auth tag */
+        if (!((uint8_t *)enc_start <= (uint8_t *)hdr + *pkt_octet_len))
+            return srtp_err_status_parse_err;
+        enc_octet_len =
+            (int)(*pkt_octet_len - ((uint8_t *)enc_start - (uint8_t *)hdr));
+        if (enc_octet_len < 0)
+            return srtp_err_status_parse_err;
+    } else {
+        enc_start = NULL;
+    }
+
+    mki_location = (uint8_t *)hdr + *pkt_octet_len;
+    mki_size = srtp_inject_mki(mki_location, session_keys, use_mki);
+
+    /*
+     * if we're providing authentication, set the auth_start and auth_tag
+     * pointers to the proper locations; otherwise, set auth_start to NULL
+     * to indicate that no authentication is needed
+     */
+    if (stream->rtp_services & sec_serv_auth) {
+        auth_start = (uint32_t *)hdr;
+        auth_tag = (uint8_t *)hdr + *pkt_octet_len + mki_size;
+    } else {
+        auth_start = NULL;
+        auth_tag = NULL;
+    }
+
+    /*
+     * estimate the packet index using the start of the replay window
+     * and the sequence number from the header
+     */
+    status = srtp_get_est_pkt_index(hdr, stream, &est, &delta);
+
+    if (status && (status != srtp_err_status_pkt_idx_adv))
+        return status;
+
+    if (status == srtp_err_status_pkt_idx_adv)
+        advance_packet_index = 1;
+
+    if (advance_packet_index) {
+        srtp_rdbx_set_roc_seq(&stream->rtp_rdbx, (uint32_t)(est >> 16),
+                              (uint16_t)(est & 0xFFFF));
+        stream->pending_roc = 0;
+        srtp_rdbx_add_index(&stream->rtp_rdbx, 0);
+    } else {
+        status = srtp_rdbx_check(&stream->rtp_rdbx, delta);
+        if (status) {
+            if (status != srtp_err_status_replay_fail ||
+                !stream->allow_repeat_tx)
+                return status; /* we've been asked to reuse an index */
+        }
+        srtp_rdbx_add_index(&stream->rtp_rdbx, delta);
+    }
+
+#ifdef NO_64BIT_MATH
+    debug_print2(mod_srtp, "estimated packet index: %08x%08x", high32(est),
+                 low32(est));
+#else
+    debug_print(mod_srtp, "estimated packet index: %016" PRIx64, est);
+#endif
+
+    /*
+     * if we're using rindael counter mode, set nonce and seq
+     */
+    if (session_keys->rtp_cipher->type->id == SRTP_AES_ICM_128 ||
+        session_keys->rtp_cipher->type->id == SRTP_AES_ICM_192 ||
+        session_keys->rtp_cipher->type->id == SRTP_AES_ICM_256) {
+        v128_t iv;
+
+        iv.v32[0] = 0;
+        iv.v32[1] = hdr->ssrc;
+#ifdef NO_64BIT_MATH
+        iv.v64[1] = be64_to_cpu(
+            make64((high32(est) << 16) | (low32(est) >> 16), low32(est) << 16));
+#else
+        iv.v64[1] = be64_to_cpu(est << 16);
+#endif
+        status = srtp_cipher_set_iv(session_keys->rtp_cipher, (uint8_t *)&iv,
+                                    srtp_direction_encrypt);
+        if (!status && session_keys->rtp_xtn_hdr_cipher) {
+            status = srtp_cipher_set_iv(session_keys->rtp_xtn_hdr_cipher,
+                                        (uint8_t *)&iv, srtp_direction_encrypt);
+        }
+    } else {
+        v128_t iv;
+
+/* otherwise, set the index to est */
+#ifdef NO_64BIT_MATH
+        iv.v32[0] = 0;
+        iv.v32[1] = 0;
+#else
+        iv.v64[0] = 0;
+#endif
+        iv.v64[1] = be64_to_cpu(est);
+        status = srtp_cipher_set_iv(session_keys->rtp_cipher, (uint8_t *)&iv,
+                                    srtp_direction_encrypt);
+        if (!status && session_keys->rtp_xtn_hdr_cipher) {
+            status = srtp_cipher_set_iv(session_keys->rtp_xtn_hdr_cipher,
+                                        (uint8_t *)&iv, srtp_direction_encrypt);
+        }
+    }
+    if (status)
+        return srtp_err_status_cipher_fail;
+
+/* shift est, put into network byte order */
+#ifdef NO_64BIT_MATH
+    est = be64_to_cpu(
+        make64((high32(est) << 16) | (low32(est) >> 16), low32(est) << 16));
+#else
+    est = be64_to_cpu(est << 16);
+#endif
+
+    /*
+     * if we're authenticating using a universal hash, put the keystream
+     * prefix into the authentication tag
+     */
+    if (auth_start) {
+        prefix_len = srtp_auth_get_prefix_length(session_keys->rtp_auth);
+        if (prefix_len) {
+            status = srtp_cipher_output(session_keys->rtp_cipher, auth_tag,
+                                        &prefix_len);
+            if (status)
+                return srtp_err_status_cipher_fail;
+            debug_print(mod_srtp, "keystream prefix: %s",
+                        srtp_octet_string_hex_string(auth_tag, prefix_len));
+        }
+    }
+
+    if (xtn_hdr && session_keys->rtp_xtn_hdr_cipher) {
+        /*
+         * extensions header encryption RFC 6904
+         */
+        status = srtp_process_header_encryption(stream, xtn_hdr, session_keys);
+        if (status) {
+            return status;
+        }
+    }
+
+    /* if we're encrypting, exor keystream into the message */
+    if (enc_start) {
+        status =
+            srtp_cipher_encrypt(session_keys->rtp_cipher, (uint8_t *)enc_start,
+                                (unsigned int *)&enc_octet_len);
+        if (status)
+            return srtp_err_status_cipher_fail;
+    }
+
+    /*
+     *  if we're authenticating, run authentication function and put result
+     *  into the auth_tag
+     */
+    if (auth_start) {
+        /* initialize auth func context */
+        status = srtp_auth_start(session_keys->rtp_auth);
+        if (status)
+            return status;
+
+        /* run auth func over packet */
+        status = srtp_auth_update(session_keys->rtp_auth, (uint8_t *)auth_start,
+                                  *pkt_octet_len);
+        if (status)
+            return status;
+
+        /* run auth func over ROC, put result into auth_tag */
+        debug_print(mod_srtp, "estimated packet index: %016" PRIx64, est);
+        status = srtp_auth_compute(session_keys->rtp_auth, (uint8_t *)&est, 4,
+                                   auth_tag);
+        debug_print(mod_srtp, "srtp auth tag:    %s",
+                    srtp_octet_string_hex_string(auth_tag, tag_len));
+        if (status)
+            return srtp_err_status_auth_fail;
+    }
+
+    if (auth_tag) {
+        /* increase the packet length by the length of the auth tag */
+        *pkt_octet_len += tag_len;
+    }
+
+    if (use_mki) {
+        /* increate the packet length by the mki size */
+        *pkt_octet_len += mki_size;
+    }
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_unprotect(srtp_ctx_t *ctx,
+                                 void *srtp_hdr,
+                                 int *pkt_octet_len)
+{
+    return srtp_unprotect_mki(ctx, srtp_hdr, pkt_octet_len, 0);
+}
+
+srtp_err_status_t srtp_unprotect_mki(srtp_ctx_t *ctx,
+                                     void *srtp_hdr,
+                                     int *pkt_octet_len,
+                                     unsigned int use_mki)
+{
+    srtp_hdr_t *hdr = (srtp_hdr_t *)srtp_hdr;
+    uint32_t *enc_start;            /* pointer to start of encrypted portion  */
+    uint32_t *auth_start;           /* pointer to start of auth. portion      */
+    unsigned int enc_octet_len = 0; /* number of octets in encrypted portion */
+    uint8_t *auth_tag = NULL;       /* location of auth_tag within packet     */
+    srtp_xtd_seq_num_t est;         /* estimated xtd_seq_num_t of *hdr        */
+    int delta;                      /* delta of local pkt idx and that in hdr */
+    v128_t iv;
+    srtp_err_status_t status;
+    srtp_stream_ctx_t *stream;
+    uint8_t tmp_tag[SRTP_MAX_TAG_LEN];
+    uint32_t tag_len, prefix_len;
+    srtp_hdr_xtnd_t *xtn_hdr = NULL;
+    unsigned int mki_size = 0;
+    srtp_session_keys_t *session_keys = NULL;
+    int advance_packet_index = 0;
+    uint32_t roc_to_set = 0;
+    uint16_t seq_to_set = 0;
+
+    debug_print0(mod_srtp, "function srtp_unprotect");
+
+    /* we assume the hdr is 32-bit aligned to start */
+
+    /* Verify RTP header */
+    status = srtp_validate_rtp_header(srtp_hdr, pkt_octet_len);
+    if (status)
+        return status;
+
+    /* check the packet length - it must at least contain a full header */
+    if (*pkt_octet_len < octets_in_rtp_header)
+        return srtp_err_status_bad_param;
+
+    /*
+     * look up ssrc in srtp_stream list, and process the packet with
+     * the appropriate stream.  if we haven't seen this stream before,
+     * there's only one key for this srtp_session, and the cipher
+     * supports key-sharing, then we assume that a new stream using
+     * that key has just started up
+     */
+    stream = srtp_get_stream(ctx, hdr->ssrc);
+    if (stream == NULL) {
+        if (ctx->stream_template != NULL) {
+            stream = ctx->stream_template;
+            debug_print(mod_srtp, "using provisional stream (SSRC: 0x%08x)",
+                        ntohl(hdr->ssrc));
+
+/*
+ * set estimated packet index to sequence number from header,
+ * and set delta equal to the same value
+ */
+#ifdef NO_64BIT_MATH
+            est = (srtp_xtd_seq_num_t)make64(0, ntohs(hdr->seq));
+            delta = low32(est);
+#else
+            est = (srtp_xtd_seq_num_t)ntohs(hdr->seq);
+            delta = (int)est;
+#endif
+        } else {
+            /*
+             * no stream corresponding to SSRC found, and we don't do
+             * key-sharing, so return an error
+             */
+            return srtp_err_status_no_ctx;
+        }
+    } else {
+        status = srtp_get_est_pkt_index(hdr, stream, &est, &delta);
+
+        if (status && (status != srtp_err_status_pkt_idx_adv))
+            return status;
+
+        if (status == srtp_err_status_pkt_idx_adv) {
+            advance_packet_index = 1;
+            roc_to_set = (uint32_t)(est >> 16);
+            seq_to_set = (uint16_t)(est & 0xFFFF);
+        }
+
+        /* check replay database */
+        if (!advance_packet_index) {
+            status = srtp_rdbx_check(&stream->rtp_rdbx, delta);
+            if (status)
+                return status;
+        }
+    }
+
+#ifdef NO_64BIT_MATH
+    debug_print2(mod_srtp, "estimated u_packet index: %08x%08x", high32(est),
+                 low32(est));
+#else
+    debug_print(mod_srtp, "estimated u_packet index: %016" PRIx64, est);
+#endif
+
+    /* Determine if MKI is being used and what session keys should be used */
+    if (use_mki) {
+        session_keys = srtp_get_session_keys(
+            stream, (uint8_t *)hdr, (const unsigned int *)pkt_octet_len,
+            &mki_size);
+
+        if (session_keys == NULL)
+            return srtp_err_status_bad_mki;
+    } else {
+        session_keys = &stream->session_keys[0];
+    }
+
+    /*
+     * Check if this is an AEAD stream (GCM mode).  If so, then dispatch
+     * the request to our AEAD handler.
+     */
+    if (session_keys->rtp_cipher->algorithm == SRTP_AES_GCM_128 ||
+        session_keys->rtp_cipher->algorithm == SRTP_AES_GCM_256) {
+        return srtp_unprotect_aead(ctx, stream, delta, est, srtp_hdr,
+                                   (unsigned int *)pkt_octet_len, session_keys,
+                                   mki_size);
+    }
+
+    /* get tag length from stream */
+    tag_len = srtp_auth_get_tag_length(session_keys->rtp_auth);
+
+    /*
+     * set the cipher's IV properly, depending on whatever cipher we
+     * happen to be using
+     */
+    if (session_keys->rtp_cipher->type->id == SRTP_AES_ICM_128 ||
+        session_keys->rtp_cipher->type->id == SRTP_AES_ICM_192 ||
+        session_keys->rtp_cipher->type->id == SRTP_AES_ICM_256) {
+        /* aes counter mode */
+        iv.v32[0] = 0;
+        iv.v32[1] = hdr->ssrc; /* still in network order */
+#ifdef NO_64BIT_MATH
+        iv.v64[1] = be64_to_cpu(
+            make64((high32(est) << 16) | (low32(est) >> 16), low32(est) << 16));
+#else
+        iv.v64[1] = be64_to_cpu(est << 16);
+#endif
+        status = srtp_cipher_set_iv(session_keys->rtp_cipher, (uint8_t *)&iv,
+                                    srtp_direction_decrypt);
+        if (!status && session_keys->rtp_xtn_hdr_cipher) {
+            status = srtp_cipher_set_iv(session_keys->rtp_xtn_hdr_cipher,
+                                        (uint8_t *)&iv, srtp_direction_decrypt);
+        }
+    } else {
+/* no particular format - set the iv to the pakcet index */
+#ifdef NO_64BIT_MATH
+        iv.v32[0] = 0;
+        iv.v32[1] = 0;
+#else
+        iv.v64[0] = 0;
+#endif
+        iv.v64[1] = be64_to_cpu(est);
+        status = srtp_cipher_set_iv(session_keys->rtp_cipher, (uint8_t *)&iv,
+                                    srtp_direction_decrypt);
+        if (!status && session_keys->rtp_xtn_hdr_cipher) {
+            status = srtp_cipher_set_iv(session_keys->rtp_xtn_hdr_cipher,
+                                        (uint8_t *)&iv, srtp_direction_decrypt);
+        }
+    }
+    if (status)
+        return srtp_err_status_cipher_fail;
+
+/* shift est, put into network byte order */
+#ifdef NO_64BIT_MATH
+    est = be64_to_cpu(
+        make64((high32(est) << 16) | (low32(est) >> 16), low32(est) << 16));
+#else
+    est = be64_to_cpu(est << 16);
+#endif
+
+    /*
+     * find starting point for decryption and length of data to be
+     * decrypted - the encrypted portion starts after the rtp header
+     * extension, if present; otherwise, it starts after the last csrc,
+     * if any are present
+     *
+     * if we're not providing confidentiality, set enc_start to NULL
+     */
+    if (stream->rtp_services & sec_serv_conf) {
+        enc_start = (uint32_t *)hdr + uint32s_in_rtp_header + hdr->cc;
+        if (hdr->x == 1) {
+            xtn_hdr = (srtp_hdr_xtnd_t *)enc_start;
+            enc_start += (ntohs(xtn_hdr->length) + 1);
+        }
+        if (!((uint8_t *)enc_start <=
+              (uint8_t *)hdr + (*pkt_octet_len - tag_len - mki_size)))
+            return srtp_err_status_parse_err;
+        enc_octet_len = (uint32_t)(*pkt_octet_len - tag_len - mki_size -
+                                   ((uint8_t *)enc_start - (uint8_t *)hdr));
+    } else {
+        enc_start = NULL;
+    }
+
+    /*
+     * if we're providing authentication, set the auth_start and auth_tag
+     * pointers to the proper locations; otherwise, set auth_start to NULL
+     * to indicate that no authentication is needed
+     */
+    if (stream->rtp_services & sec_serv_auth) {
+        auth_start = (uint32_t *)hdr;
+        auth_tag = (uint8_t *)hdr + *pkt_octet_len - tag_len;
+    } else {
+        auth_start = NULL;
+        auth_tag = NULL;
+    }
+
+    /*
+     * if we expect message authentication, run the authentication
+     * function and compare the result with the value of the auth_tag
+     */
+    if (auth_start) {
+        /*
+         * if we're using a universal hash, then we need to compute the
+         * keystream prefix for encrypting the universal hash output
+         *
+         * if the keystream prefix length is zero, then we know that
+         * the authenticator isn't using a universal hash function
+         */
+        if (session_keys->rtp_auth->prefix_len != 0) {
+            prefix_len = srtp_auth_get_prefix_length(session_keys->rtp_auth);
+            status = srtp_cipher_output(session_keys->rtp_cipher, tmp_tag,
+                                        &prefix_len);
+            debug_print(mod_srtp, "keystream prefix: %s",
+                        srtp_octet_string_hex_string(tmp_tag, prefix_len));
+            if (status)
+                return srtp_err_status_cipher_fail;
+        }
+
+        /* initialize auth func context */
+        status = srtp_auth_start(session_keys->rtp_auth);
+        if (status)
+            return status;
+
+        /* now compute auth function over packet */
+        status = srtp_auth_update(session_keys->rtp_auth, (uint8_t *)auth_start,
+                                  *pkt_octet_len - tag_len - mki_size);
+        if (status)
+            return status;
+
+        /* run auth func over ROC, then write tmp tag */
+        status = srtp_auth_compute(session_keys->rtp_auth, (uint8_t *)&est, 4,
+                                   tmp_tag);
+
+        debug_print(mod_srtp, "computed auth tag:    %s",
+                    srtp_octet_string_hex_string(tmp_tag, tag_len));
+        debug_print(mod_srtp, "packet auth tag:      %s",
+                    srtp_octet_string_hex_string(auth_tag, tag_len));
+        if (status)
+            return srtp_err_status_auth_fail;
+
+        if (srtp_octet_string_is_eq(tmp_tag, auth_tag, tag_len))
+            return srtp_err_status_auth_fail;
+    }
+
+    /*
+     * update the key usage limit, and check it to make sure that we
+     * didn't just hit either the soft limit or the hard limit, and call
+     * the event handler if we hit either.
+     */
+    switch (srtp_key_limit_update(session_keys->limit)) {
+    case srtp_key_event_normal:
+        break;
+    case srtp_key_event_soft_limit:
+        srtp_handle_event(ctx, stream, event_key_soft_limit);
+        break;
+    case srtp_key_event_hard_limit:
+        srtp_handle_event(ctx, stream, event_key_hard_limit);
+        return srtp_err_status_key_expired;
+    default:
+        break;
+    }
+
+    if (xtn_hdr && session_keys->rtp_xtn_hdr_cipher) {
+        /* extensions header encryption RFC 6904 */
+        status = srtp_process_header_encryption(stream, xtn_hdr, session_keys);
+        if (status) {
+            return status;
+        }
+    }
+
+    /* if we're decrypting, add keystream into ciphertext */
+    if (enc_start) {
+        status = srtp_cipher_decrypt(session_keys->rtp_cipher,
+                                     (uint8_t *)enc_start, &enc_octet_len);
+        if (status)
+            return srtp_err_status_cipher_fail;
+    }
+
+    /*
+     * verify that stream is for received traffic - this check will
+     * detect SSRC collisions, since a stream that appears in both
+     * srtp_protect() and srtp_unprotect() will fail this test in one of
+     * those functions.
+     *
+     * we do this check *after* the authentication check, so that the
+     * latter check will catch any attempts to fool us into thinking
+     * that we've got a collision
+     */
+    if (stream->direction != dir_srtp_receiver) {
+        if (stream->direction == dir_unknown) {
+            stream->direction = dir_srtp_receiver;
+        } else {
+            srtp_handle_event(ctx, stream, event_ssrc_collision);
+        }
+    }
+
+    /*
+     * if the stream is a 'provisional' one, in which the template context
+     * is used, then we need to allocate a new stream at this point, since
+     * the authentication passed
+     */
+    if (stream == ctx->stream_template) {
+        srtp_stream_ctx_t *new_stream;
+
+        /*
+         * allocate and initialize a new stream
+         *
+         * note that we indicate failure if we can't allocate the new
+         * stream, and some implementations will want to not return
+         * failure here
+         */
+        status =
+            srtp_stream_clone(ctx->stream_template, hdr->ssrc, &new_stream);
+        if (status)
+            return status;
+
+        /* add new stream to the head of the stream_list */
+        new_stream->next = ctx->stream_list;
+        ctx->stream_list = new_stream;
+
+        /* set stream (the pointer used in this function) */
+        stream = new_stream;
+    }
+
+    /*
+     * the message authentication function passed, so add the packet
+     * index into the replay database
+     */
+    if (advance_packet_index) {
+        srtp_rdbx_set_roc_seq(&stream->rtp_rdbx, roc_to_set, seq_to_set);
+        stream->pending_roc = 0;
+        srtp_rdbx_add_index(&stream->rtp_rdbx, 0);
+    } else {
+        srtp_rdbx_add_index(&stream->rtp_rdbx, delta);
+    }
+
+    /* decrease the packet length by the length of the auth tag */
+    *pkt_octet_len -= tag_len;
+
+    /* decrease the packet length by the mki size */
+    *pkt_octet_len -= mki_size;
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_init()
+{
+    srtp_err_status_t status;
+
+    /* initialize crypto kernel */
+    status = srtp_crypto_kernel_init();
+    if (status)
+        return status;
+
+    /* load srtp debug module into the kernel */
+    status = srtp_crypto_kernel_load_debug_module(&mod_srtp);
+    if (status)
+        return status;
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_shutdown()
+{
+    srtp_err_status_t status;
+
+    /* shut down crypto kernel */
+    status = srtp_crypto_kernel_shutdown();
+    if (status)
+        return status;
+
+    /* shutting down crypto kernel frees the srtp debug module as well */
+
+    return srtp_err_status_ok;
+}
+
+/*
+ * srtp_get_stream(ssrc) returns a pointer to the stream corresponding
+ * to ssrc, or NULL if no stream exists for that ssrc
+ *
+ * this is an internal function
+ */
+
+srtp_stream_ctx_t *srtp_get_stream(srtp_t srtp, uint32_t ssrc)
+{
+    srtp_stream_ctx_t *stream;
+
+    /* walk down list until ssrc is found */
+    stream = srtp->stream_list;
+    while (stream != NULL) {
+        if (stream->ssrc == ssrc)
+            return stream;
+        stream = stream->next;
+    }
+
+    /* we haven't found our ssrc, so return a null */
+    return NULL;
+}
+
+srtp_err_status_t srtp_dealloc(srtp_t session)
+{
+    srtp_stream_ctx_t *stream;
+    srtp_err_status_t status;
+
+    /*
+     * we take a conservative deallocation strategy - if we encounter an
+     * error deallocating a stream, then we stop trying to deallocate
+     * memory and just return an error
+     */
+
+    /* walk list of streams, deallocating as we go */
+    stream = session->stream_list;
+    while (stream != NULL) {
+        srtp_stream_t next = stream->next;
+        status = srtp_stream_dealloc(stream, session->stream_template);
+        if (status)
+            return status;
+        stream = next;
+    }
+
+    /* deallocate stream template, if there is one */
+    if (session->stream_template != NULL) {
+        status = srtp_stream_dealloc(session->stream_template, NULL);
+        if (status)
+            return status;
+    }
+
+    /* deallocate session context */
+    srtp_crypto_free(session);
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_add_stream(srtp_t session, const srtp_policy_t *policy)
+{
+    srtp_err_status_t status;
+    srtp_stream_t tmp;
+
+    status = srtp_valid_policy(policy);
+    if (status != srtp_err_status_ok) {
+        return status;
+    }
+
+    /* sanity check arguments */
+    if ((session == NULL) || (policy == NULL) ||
+        (!srtp_validate_policy_master_keys(policy)))
+        return srtp_err_status_bad_param;
+
+    /* allocate stream  */
+    status = srtp_stream_alloc(&tmp, policy);
+    if (status) {
+        return status;
+    }
+
+    /* initialize stream  */
+    status = srtp_stream_init(tmp, policy);
+    if (status) {
+        srtp_stream_dealloc(tmp, NULL);
+        return status;
+    }
+
+    /*
+     * set the head of the stream list or the template to point to the
+     * stream that we've just alloced and init'ed, depending on whether
+     * or not it has a wildcard SSRC value or not
+     *
+     * if the template stream has already been set, then the policy is
+     * inconsistent, so we return a bad_param error code
+     */
+    switch (policy->ssrc.type) {
+    case (ssrc_any_outbound):
+        if (session->stream_template) {
+            srtp_stream_dealloc(tmp, NULL);
+            return srtp_err_status_bad_param;
+        }
+        session->stream_template = tmp;
+        session->stream_template->direction = dir_srtp_sender;
+        break;
+    case (ssrc_any_inbound):
+        if (session->stream_template) {
+            srtp_stream_dealloc(tmp, NULL);
+            return srtp_err_status_bad_param;
+        }
+        session->stream_template = tmp;
+        session->stream_template->direction = dir_srtp_receiver;
+        break;
+    case (ssrc_specific):
+        tmp->next = session->stream_list;
+        session->stream_list = tmp;
+        break;
+    case (ssrc_undefined):
+    default:
+        srtp_stream_dealloc(tmp, NULL);
+        return srtp_err_status_bad_param;
+    }
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_create(srtp_t *session, /* handle for session     */
+                              const srtp_policy_t *policy)
+{ /* SRTP policy (list)     */
+    srtp_err_status_t stat;
+    srtp_ctx_t *ctx;
+
+    stat = srtp_valid_policy(policy);
+    if (stat != srtp_err_status_ok) {
+        return stat;
+    }
+
+    /* sanity check arguments */
+    if (session == NULL)
+        return srtp_err_status_bad_param;
+
+    /* allocate srtp context and set ctx_ptr */
+    ctx = (srtp_ctx_t *)srtp_crypto_alloc(sizeof(srtp_ctx_t));
+    if (ctx == NULL)
+        return srtp_err_status_alloc_fail;
+    *session = ctx;
+
+    /*
+     * loop over elements in the policy list, allocating and
+     * initializing a stream for each element
+     */
+    ctx->stream_template = NULL;
+    ctx->stream_list = NULL;
+    ctx->user_data = NULL;
+    while (policy != NULL) {
+        stat = srtp_add_stream(ctx, policy);
+        if (stat) {
+            /* clean up everything */
+            srtp_dealloc(*session);
+            *session = NULL;
+            return stat;
+        }
+
+        /* set policy to next item in list  */
+        policy = policy->next;
+    }
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_remove_stream(srtp_t session, uint32_t ssrc)
+{
+    srtp_stream_ctx_t *stream, *last_stream;
+    srtp_err_status_t status;
+
+    /* sanity check arguments */
+    if (session == NULL)
+        return srtp_err_status_bad_param;
+
+    /* find stream in list; complain if not found */
+    last_stream = stream = session->stream_list;
+    while ((stream != NULL) && (ssrc != stream->ssrc)) {
+        last_stream = stream;
+        stream = stream->next;
+    }
+    if (stream == NULL)
+        return srtp_err_status_no_ctx;
+
+    /* remove stream from the list */
+    if (last_stream == stream)
+        /* stream was first in list */
+        session->stream_list = stream->next;
+    else
+        last_stream->next = stream->next;
+
+    /* deallocate the stream */
+    status = srtp_stream_dealloc(stream, session->stream_template);
+    if (status)
+        return status;
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_update(srtp_t session, const srtp_policy_t *policy)
+{
+    srtp_err_status_t stat;
+
+    stat = srtp_valid_policy(policy);
+    if (stat != srtp_err_status_ok) {
+        return stat;
+    }
+
+    /* sanity check arguments */
+    if ((session == NULL) || (policy == NULL) ||
+        (!srtp_validate_policy_master_keys(policy))) {
+        return srtp_err_status_bad_param;
+    }
+
+    while (policy != NULL) {
+        stat = srtp_update_stream(session, policy);
+        if (stat) {
+            return stat;
+        }
+
+        /* set policy to next item in list  */
+        policy = policy->next;
+    }
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t update_template_streams(srtp_t session,
+                                                 const srtp_policy_t *policy)
+{
+    srtp_err_status_t status;
+    srtp_stream_t new_stream_template;
+    srtp_stream_t new_stream_list = NULL;
+
+    status = srtp_valid_policy(policy);
+    if (status != srtp_err_status_ok) {
+        return status;
+    }
+
+    if (session->stream_template == NULL) {
+        return srtp_err_status_bad_param;
+    }
+
+    /* allocate new template stream  */
+    status = srtp_stream_alloc(&new_stream_template, policy);
+    if (status) {
+        return status;
+    }
+
+    /* initialize new template stream  */
+    status = srtp_stream_init(new_stream_template, policy);
+    if (status) {
+        srtp_crypto_free(new_stream_template);
+        return status;
+    }
+
+    /* for all old templated streams */
+    for (;;) {
+        srtp_stream_t stream;
+        uint32_t ssrc;
+        srtp_xtd_seq_num_t old_index;
+        srtp_rdb_t old_rtcp_rdb;
+
+        stream = session->stream_list;
+        while ((stream != NULL) &&
+               (stream->session_keys[0].rtp_auth !=
+                session->stream_template->session_keys[0].rtp_auth)) {
+            stream = stream->next;
+        }
+        if (stream == NULL) {
+            /* no more templated streams */
+            break;
+        }
+
+        /* save old extendard seq */
+        ssrc = stream->ssrc;
+        old_index = stream->rtp_rdbx.index;
+        old_rtcp_rdb = stream->rtcp_rdb;
+
+        /* remove stream */
+        status = srtp_remove_stream(session, ssrc);
+        if (status) {
+            /* free new allocations */
+            while (new_stream_list != NULL) {
+                srtp_stream_t next = new_stream_list->next;
+                srtp_stream_dealloc(new_stream_list, new_stream_template);
+                new_stream_list = next;
+            }
+            srtp_stream_dealloc(new_stream_template, NULL);
+            return status;
+        }
+
+        /* allocate and initialize a new stream */
+        status = srtp_stream_clone(new_stream_template, ssrc, &stream);
+        if (status) {
+            /* free new allocations */
+            while (new_stream_list != NULL) {
+                srtp_stream_t next = new_stream_list->next;
+                srtp_stream_dealloc(new_stream_list, new_stream_template);
+                new_stream_list = next;
+            }
+            srtp_stream_dealloc(new_stream_template, NULL);
+            return status;
+        }
+
+        /* add new stream to the head of the new_stream_list */
+        stream->next = new_stream_list;
+        new_stream_list = stream;
+
+        /* restore old extended seq */
+        stream->rtp_rdbx.index = old_index;
+        stream->rtcp_rdb = old_rtcp_rdb;
+    }
+    /* dealloc old template */
+    srtp_stream_dealloc(session->stream_template, NULL);
+    /* set new template */
+    session->stream_template = new_stream_template;
+    /* add new list */
+    if (new_stream_list) {
+        srtp_stream_t tail = new_stream_list;
+        while (tail->next) {
+            tail = tail->next;
+        }
+        tail->next = session->stream_list;
+        session->stream_list = new_stream_list;
+    }
+    return status;
+}
+
+static srtp_err_status_t update_stream(srtp_t session,
+                                       const srtp_policy_t *policy)
+{
+    srtp_err_status_t status;
+    srtp_xtd_seq_num_t old_index;
+    srtp_rdb_t old_rtcp_rdb;
+    srtp_stream_t stream;
+
+    status = srtp_valid_policy(policy);
+    if (status != srtp_err_status_ok) {
+        return status;
+    }
+
+    stream = srtp_get_stream(session, htonl(policy->ssrc.value));
+    if (stream == NULL) {
+        return srtp_err_status_bad_param;
+    }
+
+    /* save old extendard seq */
+    old_index = stream->rtp_rdbx.index;
+    old_rtcp_rdb = stream->rtcp_rdb;
+
+    status = srtp_remove_stream(session, htonl(policy->ssrc.value));
+    if (status) {
+        return status;
+    }
+
+    status = srtp_add_stream(session, policy);
+    if (status) {
+        return status;
+    }
+
+    stream = srtp_get_stream(session, htonl(policy->ssrc.value));
+    if (stream == NULL) {
+        return srtp_err_status_fail;
+    }
+
+    /* restore old extended seq */
+    stream->rtp_rdbx.index = old_index;
+    stream->rtcp_rdb = old_rtcp_rdb;
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_update_stream(srtp_t session,
+                                     const srtp_policy_t *policy)
+{
+    srtp_err_status_t status;
+
+    status = srtp_valid_policy(policy);
+    if (status != srtp_err_status_ok) {
+        return status;
+    }
+
+    /* sanity check arguments */
+    if ((session == NULL) || (policy == NULL) ||
+        (!srtp_validate_policy_master_keys(policy)))
+        return srtp_err_status_bad_param;
+
+    switch (policy->ssrc.type) {
+    case (ssrc_any_outbound):
+    case (ssrc_any_inbound):
+        status = update_template_streams(session, policy);
+        break;
+    case (ssrc_specific):
+        status = update_stream(session, policy);
+        break;
+    case (ssrc_undefined):
+    default:
+        return srtp_err_status_bad_param;
+    }
+
+    return status;
+}
+
+/*
+ * The default policy - provides a convenient way for callers to use
+ * the default security policy
+ *
+ * The default policy is defined in RFC 3711
+ * (Section 5. Default and mandatory-to-implement Transforms)
+ *
+ */
+
+/*
+ * NOTE: cipher_key_len is really key len (128 bits) plus salt len
+ *  (112 bits)
+ */
+/* There are hard-coded 16's for base_key_len in the key generation code */
+
+void srtp_crypto_policy_set_rtp_default(srtp_crypto_policy_t *p)
+{
+    p->cipher_type = SRTP_AES_ICM_128;
+    p->cipher_key_len =
+        SRTP_AES_ICM_128_KEY_LEN_WSALT; /* default 128 bits per RFC 3711 */
+    p->auth_type = SRTP_HMAC_SHA1;
+    p->auth_key_len = 20; /* default 160 bits per RFC 3711 */
+    p->auth_tag_len = 10; /* default 80 bits per RFC 3711 */
+    p->sec_serv = sec_serv_conf_and_auth;
+}
+
+void srtp_crypto_policy_set_rtcp_default(srtp_crypto_policy_t *p)
+{
+    p->cipher_type = SRTP_AES_ICM_128;
+    p->cipher_key_len =
+        SRTP_AES_ICM_128_KEY_LEN_WSALT; /* default 128 bits per RFC 3711 */
+    p->auth_type = SRTP_HMAC_SHA1;
+    p->auth_key_len = 20; /* default 160 bits per RFC 3711 */
+    p->auth_tag_len = 10; /* default 80 bits per RFC 3711 */
+    p->sec_serv = sec_serv_conf_and_auth;
+}
+
+void srtp_crypto_policy_set_aes_cm_128_hmac_sha1_32(srtp_crypto_policy_t *p)
+{
+    /*
+     * corresponds to RFC 4568
+     *
+     * note that this crypto policy is intended for SRTP, but not SRTCP
+     */
+
+    p->cipher_type = SRTP_AES_ICM_128;
+    p->cipher_key_len =
+        SRTP_AES_ICM_128_KEY_LEN_WSALT; /* 128 bit key, 112 bit salt */
+    p->auth_type = SRTP_HMAC_SHA1;
+    p->auth_key_len = 20; /* 160 bit key               */
+    p->auth_tag_len = 4;  /* 32 bit tag                */
+    p->sec_serv = sec_serv_conf_and_auth;
+}
+
+void srtp_crypto_policy_set_aes_cm_128_null_auth(srtp_crypto_policy_t *p)
+{
+    /*
+     * corresponds to RFC 4568
+     *
+     * note that this crypto policy is intended for SRTP, but not SRTCP
+     */
+
+    p->cipher_type = SRTP_AES_ICM_128;
+    p->cipher_key_len =
+        SRTP_AES_ICM_128_KEY_LEN_WSALT; /* 128 bit key, 112 bit salt */
+    p->auth_type = SRTP_NULL_AUTH;
+    p->auth_key_len = 0;
+    p->auth_tag_len = 0;
+    p->sec_serv = sec_serv_conf;
+}
+
+void srtp_crypto_policy_set_null_cipher_hmac_sha1_80(srtp_crypto_policy_t *p)
+{
+    /*
+     * corresponds to RFC 4568
+     */
+
+    p->cipher_type = SRTP_NULL_CIPHER;
+    p->cipher_key_len = 16;
+    p->auth_type = SRTP_HMAC_SHA1;
+    p->auth_key_len = 20;
+    p->auth_tag_len = 10;
+    p->sec_serv = sec_serv_auth;
+}
+
+void srtp_crypto_policy_set_null_cipher_hmac_null(srtp_crypto_policy_t *p)
+{
+    /*
+     * Should only be used for testing
+     */
+
+    p->cipher_type = SRTP_NULL_CIPHER;
+    p->cipher_key_len = 16;
+    p->auth_type = SRTP_NULL_AUTH;
+    p->auth_key_len = 0;
+    p->auth_tag_len = 0;
+    p->sec_serv = sec_serv_none;
+}
+
+void srtp_crypto_policy_set_aes_cm_256_hmac_sha1_80(srtp_crypto_policy_t *p)
+{
+    /*
+     * corresponds to RFC 6188
+     */
+
+    p->cipher_type = SRTP_AES_ICM_256;
+    p->cipher_key_len = SRTP_AES_ICM_256_KEY_LEN_WSALT;
+    p->auth_type = SRTP_HMAC_SHA1;
+    p->auth_key_len = 20; /* default 160 bits per RFC 3711 */
+    p->auth_tag_len = 10; /* default 80 bits per RFC 3711 */
+    p->sec_serv = sec_serv_conf_and_auth;
+}
+
+void srtp_crypto_policy_set_aes_cm_256_hmac_sha1_32(srtp_crypto_policy_t *p)
+{
+    /*
+     * corresponds to RFC 6188
+     *
+     * note that this crypto policy is intended for SRTP, but not SRTCP
+     */
+
+    p->cipher_type = SRTP_AES_ICM_256;
+    p->cipher_key_len = SRTP_AES_ICM_256_KEY_LEN_WSALT;
+    p->auth_type = SRTP_HMAC_SHA1;
+    p->auth_key_len = 20; /* default 160 bits per RFC 3711 */
+    p->auth_tag_len = 4;  /* default 80 bits per RFC 3711 */
+    p->sec_serv = sec_serv_conf_and_auth;
+}
+
+/*
+ * AES-256 with no authentication.
+ */
+void srtp_crypto_policy_set_aes_cm_256_null_auth(srtp_crypto_policy_t *p)
+{
+    p->cipher_type = SRTP_AES_ICM_256;
+    p->cipher_key_len = SRTP_AES_ICM_256_KEY_LEN_WSALT;
+    p->auth_type = SRTP_NULL_AUTH;
+    p->auth_key_len = 0;
+    p->auth_tag_len = 0;
+    p->sec_serv = sec_serv_conf;
+}
+
+void srtp_crypto_policy_set_aes_cm_192_hmac_sha1_80(srtp_crypto_policy_t *p)
+{
+    /*
+     * corresponds to RFC 6188
+     */
+
+    p->cipher_type = SRTP_AES_ICM_192;
+    p->cipher_key_len = SRTP_AES_ICM_192_KEY_LEN_WSALT;
+    p->auth_type = SRTP_HMAC_SHA1;
+    p->auth_key_len = 20; /* default 160 bits per RFC 3711 */
+    p->auth_tag_len = 10; /* default 80 bits per RFC 3711 */
+    p->sec_serv = sec_serv_conf_and_auth;
+}
+
+void srtp_crypto_policy_set_aes_cm_192_hmac_sha1_32(srtp_crypto_policy_t *p)
+{
+    /*
+     * corresponds to RFC 6188
+     *
+     * note that this crypto policy is intended for SRTP, but not SRTCP
+     */
+
+    p->cipher_type = SRTP_AES_ICM_192;
+    p->cipher_key_len = SRTP_AES_ICM_192_KEY_LEN_WSALT;
+    p->auth_type = SRTP_HMAC_SHA1;
+    p->auth_key_len = 20; /* default 160 bits per RFC 3711 */
+    p->auth_tag_len = 4;  /* default 80 bits per RFC 3711 */
+    p->sec_serv = sec_serv_conf_and_auth;
+}
+
+/*
+ * AES-192 with no authentication.
+ */
+void srtp_crypto_policy_set_aes_cm_192_null_auth(srtp_crypto_policy_t *p)
+{
+    p->cipher_type = SRTP_AES_ICM_192;
+    p->cipher_key_len = SRTP_AES_ICM_192_KEY_LEN_WSALT;
+    p->auth_type = SRTP_NULL_AUTH;
+    p->auth_key_len = 0;
+    p->auth_tag_len = 0;
+    p->sec_serv = sec_serv_conf;
+}
+
+/*
+ * AES-128 GCM mode with 8 octet auth tag.
+ */
+void srtp_crypto_policy_set_aes_gcm_128_8_auth(srtp_crypto_policy_t *p)
+{
+    p->cipher_type = SRTP_AES_GCM_128;
+    p->cipher_key_len = SRTP_AES_GCM_128_KEY_LEN_WSALT;
+    p->auth_type = SRTP_NULL_AUTH; /* GCM handles the auth for us */
+    p->auth_key_len = 0;
+    p->auth_tag_len = 8; /* 8 octet tag length */
+    p->sec_serv = sec_serv_conf_and_auth;
+}
+
+/*
+ * AES-256 GCM mode with 8 octet auth tag.
+ */
+void srtp_crypto_policy_set_aes_gcm_256_8_auth(srtp_crypto_policy_t *p)
+{
+    p->cipher_type = SRTP_AES_GCM_256;
+    p->cipher_key_len = SRTP_AES_GCM_256_KEY_LEN_WSALT;
+    p->auth_type = SRTP_NULL_AUTH; /* GCM handles the auth for us */
+    p->auth_key_len = 0;
+    p->auth_tag_len = 8; /* 8 octet tag length */
+    p->sec_serv = sec_serv_conf_and_auth;
+}
+
+/*
+ * AES-128 GCM mode with 8 octet auth tag, no RTCP encryption.
+ */
+void srtp_crypto_policy_set_aes_gcm_128_8_only_auth(srtp_crypto_policy_t *p)
+{
+    p->cipher_type = SRTP_AES_GCM_128;
+    p->cipher_key_len = SRTP_AES_GCM_128_KEY_LEN_WSALT;
+    p->auth_type = SRTP_NULL_AUTH; /* GCM handles the auth for us */
+    p->auth_key_len = 0;
+    p->auth_tag_len = 8;         /* 8 octet tag length */
+    p->sec_serv = sec_serv_auth; /* This only applies to RTCP */
+}
+
+/*
+ * AES-256 GCM mode with 8 octet auth tag, no RTCP encryption.
+ */
+void srtp_crypto_policy_set_aes_gcm_256_8_only_auth(srtp_crypto_policy_t *p)
+{
+    p->cipher_type = SRTP_AES_GCM_256;
+    p->cipher_key_len = SRTP_AES_GCM_256_KEY_LEN_WSALT;
+    p->auth_type = SRTP_NULL_AUTH; /* GCM handles the auth for us */
+    p->auth_key_len = 0;
+    p->auth_tag_len = 8;         /* 8 octet tag length */
+    p->sec_serv = sec_serv_auth; /* This only applies to RTCP */
+}
+
+/*
+ * AES-128 GCM mode with 16 octet auth tag.
+ */
+void srtp_crypto_policy_set_aes_gcm_128_16_auth(srtp_crypto_policy_t *p)
+{
+    p->cipher_type = SRTP_AES_GCM_128;
+    p->cipher_key_len = SRTP_AES_GCM_128_KEY_LEN_WSALT;
+    p->auth_type = SRTP_NULL_AUTH; /* GCM handles the auth for us */
+    p->auth_key_len = 0;
+    p->auth_tag_len = 16; /* 16 octet tag length */
+    p->sec_serv = sec_serv_conf_and_auth;
+}
+
+/*
+ * AES-256 GCM mode with 16 octet auth tag.
+ */
+void srtp_crypto_policy_set_aes_gcm_256_16_auth(srtp_crypto_policy_t *p)
+{
+    p->cipher_type = SRTP_AES_GCM_256;
+    p->cipher_key_len = SRTP_AES_GCM_256_KEY_LEN_WSALT;
+    p->auth_type = SRTP_NULL_AUTH; /* GCM handles the auth for us */
+    p->auth_key_len = 0;
+    p->auth_tag_len = 16; /* 16 octet tag length */
+    p->sec_serv = sec_serv_conf_and_auth;
+}
+
+/*
+ * secure rtcp functions
+ */
+
+/*
+ * AEAD uses a new IV formation method.  This function implements
+ * section 9.1 (SRTCP IV Formation for AES-GCM) from RFC7714.
+ * The calculation is defined as, where (+) is the xor operation:
+ *
+ *                0  1  2  3  4  5  6  7  8  9 10 11
+ *               +--+--+--+--+--+--+--+--+--+--+--+--+
+ *               |00|00|    SSRC   |00|00|0+SRTCP Idx|---+
+ *               +--+--+--+--+--+--+--+--+--+--+--+--+   |
+ *                                                       |
+ *               +--+--+--+--+--+--+--+--+--+--+--+--+   |
+ *               |         Encryption Salt           |->(+)
+ *               +--+--+--+--+--+--+--+--+--+--+--+--+   |
+ *                                                       |
+ *               +--+--+--+--+--+--+--+--+--+--+--+--+   |
+ *               |       Initialization Vector       |<--+
+ *               +--+--+--+--+--+--+--+--+--+--+--+--+*
+ *
+ * Input:  *session_keys - pointer to SRTP stream context session keys,
+ *                        used to retrieve the SALT
+ *         *iv           - Pointer to recieve the calculated IV
+ *         seq_num       - The SEQ value to use for the IV calculation.
+ *         *hdr          - The RTP header, used to get the SSRC value
+ *
+ * Returns: srtp_err_status_ok if no error or srtp_err_status_bad_param
+ *          if seq_num is invalid
+ *
+ */
+static srtp_err_status_t srtp_calc_aead_iv_srtcp(
+    srtp_session_keys_t *session_keys,
+    v128_t *iv,
+    uint32_t seq_num,
+    srtcp_hdr_t *hdr)
+{
+    v128_t in;
+    v128_t salt;
+
+    memset(&in, 0, sizeof(v128_t));
+    memset(&salt, 0, sizeof(v128_t));
+
+    in.v16[0] = 0;
+    memcpy(&in.v16[1], &hdr->ssrc, 4); /* still in network order! */
+    in.v16[3] = 0;
+
+    /*
+     *  The SRTCP index (seq_num) spans bits 0 through 30 inclusive.
+     *  The most significant bit should be zero.
+     */
+    if (seq_num & 0x80000000UL) {
+        return srtp_err_status_bad_param;
+    }
+    in.v32[2] = htonl(seq_num);
+
+    debug_print(mod_srtp, "Pre-salted RTCP IV = %s\n", v128_hex_string(&in));
+
+    /*
+     * Get the SALT value from the context
+     */
+    memcpy(salt.v8, session_keys->c_salt, 12);
+    debug_print(mod_srtp, "RTCP SALT = %s\n", v128_hex_string(&salt));
+
+    /*
+     * Finally, apply the SALT to the input
+     */
+    v128_xor(iv, &in, &salt);
+
+    return srtp_err_status_ok;
+}
+
+/*
+ * This code handles AEAD ciphers for outgoing RTCP.  We currently support
+ * AES-GCM mode with 128 or 256 bit keys.
+ */
+static srtp_err_status_t srtp_protect_rtcp_aead(
+    srtp_t ctx,
+    srtp_stream_ctx_t *stream,
+    void *rtcp_hdr,
+    unsigned int *pkt_octet_len,
+    srtp_session_keys_t *session_keys,
+    unsigned int use_mki)
+{
+    srtcp_hdr_t *hdr = (srtcp_hdr_t *)rtcp_hdr;
+    uint32_t *enc_start;            /* pointer to start of encrypted portion  */
+    uint32_t *trailer_p;            /* pointer to start of trailer            */
+    uint32_t trailer;               /* trailer value                          */
+    unsigned int enc_octet_len = 0; /* number of octets in encrypted portion */
+    uint8_t *auth_tag = NULL;       /* location of auth_tag within packet     */
+    srtp_err_status_t status;
+    uint32_t tag_len;
+    uint32_t seq_num;
+    v128_t iv;
+    uint32_t tseq;
+    unsigned int mki_size = 0;
+
+    /* get tag length from stream context */
+    tag_len = srtp_auth_get_tag_length(session_keys->rtcp_auth);
+
+    /*
+     * set encryption start and encryption length - if we're not
+     * providing confidentiality, set enc_start to NULL
+     */
+    enc_start = (uint32_t *)hdr + uint32s_in_rtcp_header;
+    enc_octet_len = *pkt_octet_len - octets_in_rtcp_header;
+
+    /* NOTE: hdr->length is not usable - it refers to only the first
+     * RTCP report in the compound packet!
+     */
+    trailer_p = (uint32_t *)((char *)enc_start + enc_octet_len + tag_len);
+
+    if (stream->rtcp_services & sec_serv_conf) {
+        trailer = htonl(SRTCP_E_BIT); /* set encrypt bit */
+    } else {
+        enc_start = NULL;
+        enc_octet_len = 0;
+        /* 0 is network-order independant */
+        trailer = 0x00000000; /* set encrypt bit */
+    }
+
+    mki_size = srtp_inject_mki((uint8_t *)hdr + *pkt_octet_len + tag_len +
+                                   sizeof(srtcp_trailer_t),
+                               session_keys, use_mki);
+
+    /*
+     * set the auth_tag pointer to the proper location, which is after
+     * the payload, but before the trailer
+     * (note that srtpc *always* provides authentication, unlike srtp)
+     */
+    /* Note: This would need to change for optional mikey data */
+    auth_tag = (uint8_t *)hdr + *pkt_octet_len;
+
+    /*
+     * check sequence number for overruns, and copy it into the packet
+     * if its value isn't too big
+     */
+    status = srtp_rdb_increment(&stream->rtcp_rdb);
+    if (status) {
+        return status;
+    }
+    seq_num = srtp_rdb_get_value(&stream->rtcp_rdb);
+    trailer |= htonl(seq_num);
+    debug_print(mod_srtp, "srtcp index: %x", seq_num);
+
+    memcpy(trailer_p, &trailer, sizeof(trailer));
+
+    /*
+     * Calculate and set the IV
+     */
+    status = srtp_calc_aead_iv_srtcp(session_keys, &iv, seq_num, hdr);
+    if (status) {
+        return srtp_err_status_cipher_fail;
+    }
+    status = srtp_cipher_set_iv(session_keys->rtcp_cipher, (uint8_t *)&iv,
+                                srtp_direction_encrypt);
+    if (status) {
+        return srtp_err_status_cipher_fail;
+    }
+
+    /*
+     * Set the AAD for GCM mode
+     */
+    if (enc_start) {
+        /*
+         * If payload encryption is enabled, then the AAD consist of
+         * the RTCP header and the seq# at the end of the packet
+         */
+        status = srtp_cipher_set_aad(session_keys->rtcp_cipher, (uint8_t *)hdr,
+                                     octets_in_rtcp_header);
+        if (status) {
+            return (srtp_err_status_cipher_fail);
+        }
+    } else {
+        /*
+         * Since payload encryption is not enabled, we must authenticate
+         * the entire packet as described in RFC 7714 (Section 9.3. Data
+         * Types in Unencrypted SRTCP Compound Packets)
+         */
+        status = srtp_cipher_set_aad(session_keys->rtcp_cipher, (uint8_t *)hdr,
+                                     *pkt_octet_len);
+        if (status) {
+            return (srtp_err_status_cipher_fail);
+        }
+    }
+    /*
+     * Process the sequence# as AAD
+     */
+    tseq = trailer;
+    status = srtp_cipher_set_aad(session_keys->rtcp_cipher, (uint8_t *)&tseq,
+                                 sizeof(srtcp_trailer_t));
+    if (status) {
+        return (srtp_err_status_cipher_fail);
+    }
+
+    /* if we're encrypting, exor keystream into the message */
+    if (enc_start) {
+        status = srtp_cipher_encrypt(session_keys->rtcp_cipher,
+                                     (uint8_t *)enc_start, &enc_octet_len);
+        if (status) {
+            return srtp_err_status_cipher_fail;
+        }
+        /*
+         * Get the tag and append that to the output
+         */
+        status = srtp_cipher_get_tag(session_keys->rtcp_cipher,
+                                     (uint8_t *)auth_tag, &tag_len);
+        if (status) {
+            return (srtp_err_status_cipher_fail);
+        }
+        enc_octet_len += tag_len;
+    } else {
+        /*
+         * Even though we're not encrypting the payload, we need
+         * to run the cipher to get the auth tag.
+         */
+        unsigned int nolen = 0;
+        status = srtp_cipher_encrypt(session_keys->rtcp_cipher, NULL, &nolen);
+        if (status) {
+            return srtp_err_status_cipher_fail;
+        }
+        /*
+         * Get the tag and append that to the output
+         */
+        status = srtp_cipher_get_tag(session_keys->rtcp_cipher,
+                                     (uint8_t *)auth_tag, &tag_len);
+        if (status) {
+            return (srtp_err_status_cipher_fail);
+        }
+        enc_octet_len += tag_len;
+    }
+
+    /* increase the packet length by the length of the auth tag and seq_num*/
+    *pkt_octet_len += (tag_len + sizeof(srtcp_trailer_t));
+
+    /* increase the packet by the mki_size */
+    *pkt_octet_len += mki_size;
+
+    return srtp_err_status_ok;
+}
+
+/*
+ * This function handles incoming SRTCP packets while in AEAD mode,
+ * which currently supports AES-GCM encryption.  Note, the auth tag is
+ * at the end of the packet stream and is automatically checked by GCM
+ * when decrypting the payload.
+ */
+static srtp_err_status_t srtp_unprotect_rtcp_aead(
+    srtp_t ctx,
+    srtp_stream_ctx_t *stream,
+    void *srtcp_hdr,
+    unsigned int *pkt_octet_len,
+    srtp_session_keys_t *session_keys,
+    unsigned int use_mki)
+{
+    srtcp_hdr_t *hdr = (srtcp_hdr_t *)srtcp_hdr;
+    uint32_t *enc_start;            /* pointer to start of encrypted portion  */
+    uint32_t *trailer_p;            /* pointer to start of trailer            */
+    uint32_t trailer;               /* trailer value                          */
+    unsigned int enc_octet_len = 0; /* number of octets in encrypted portion */
+    uint8_t *auth_tag = NULL;       /* location of auth_tag within packet     */
+    srtp_err_status_t status;
+    int tag_len;
+    unsigned int tmp_len;
+    uint32_t seq_num;
+    v128_t iv;
+    uint32_t tseq;
+    unsigned int mki_size = 0;
+
+    /* get tag length from stream context */
+    tag_len = srtp_auth_get_tag_length(session_keys->rtcp_auth);
+
+    if (use_mki) {
+        mki_size = session_keys->mki_size;
+    }
+
+    /*
+     * set encryption start, encryption length, and trailer
+     */
+    /* index & E (encryption) bit follow normal data. hdr->len is the number of
+     * words (32-bit) in the normal packet minus 1
+     */
+    /* This should point trailer to the word past the end of the normal data. */
+    /* This would need to be modified for optional mikey data */
+    trailer_p = (uint32_t *)((char *)hdr + *pkt_octet_len -
+                             sizeof(srtcp_trailer_t) - mki_size);
+    memcpy(&trailer, trailer_p, sizeof(trailer));
+
+    /*
+     * We pass the tag down to the cipher when doing GCM mode
+     */
+    enc_octet_len = *pkt_octet_len - (octets_in_rtcp_header +
+                                      sizeof(srtcp_trailer_t) + mki_size);
+    auth_tag = (uint8_t *)hdr + *pkt_octet_len - tag_len - mki_size -
+               sizeof(srtcp_trailer_t);
+
+    if (*((unsigned char *)trailer_p) & SRTCP_E_BYTE_BIT) {
+        enc_start = (uint32_t *)hdr + uint32s_in_rtcp_header;
+    } else {
+        enc_octet_len = 0;
+        enc_start = NULL; /* this indicates that there's no encryption */
+    }
+
+    /*
+     * check the sequence number for replays
+     */
+    /* this is easier than dealing with bitfield access */
+    seq_num = ntohl(trailer) & SRTCP_INDEX_MASK;
+    debug_print(mod_srtp, "srtcp index: %x", seq_num);
+    status = srtp_rdb_check(&stream->rtcp_rdb, seq_num);
+    if (status) {
+        return status;
+    }
+
+    /*
+     * Calculate and set the IV
+     */
+    status = srtp_calc_aead_iv_srtcp(session_keys, &iv, seq_num, hdr);
+    if (status) {
+        return srtp_err_status_cipher_fail;
+    }
+    status = srtp_cipher_set_iv(session_keys->rtcp_cipher, (uint8_t *)&iv,
+                                srtp_direction_decrypt);
+    if (status) {
+        return srtp_err_status_cipher_fail;
+    }
+
+    /*
+     * Set the AAD for GCM mode
+     */
+    if (enc_start) {
+        /*
+         * If payload encryption is enabled, then the AAD consist of
+         * the RTCP header and the seq# at the end of the packet
+         */
+        status = srtp_cipher_set_aad(session_keys->rtcp_cipher, (uint8_t *)hdr,
+                                     octets_in_rtcp_header);
+        if (status) {
+            return (srtp_err_status_cipher_fail);
+        }
+    } else {
+        /*
+         * Since payload encryption is not enabled, we must authenticate
+         * the entire packet as described in RFC 7714 (Section 9.3. Data
+         * Types in Unencrypted SRTCP Compound Packets)
+         */
+        status = srtp_cipher_set_aad(
+            session_keys->rtcp_cipher, (uint8_t *)hdr,
+            (*pkt_octet_len - tag_len - sizeof(srtcp_trailer_t) - mki_size));
+        if (status) {
+            return (srtp_err_status_cipher_fail);
+        }
+    }
+
+    /*
+     * Process the sequence# as AAD
+     */
+    tseq = trailer;
+    status = srtp_cipher_set_aad(session_keys->rtcp_cipher, (uint8_t *)&tseq,
+                                 sizeof(srtcp_trailer_t));
+    if (status) {
+        return (srtp_err_status_cipher_fail);
+    }
+
+    /* if we're decrypting, exor keystream into the message */
+    if (enc_start) {
+        status = srtp_cipher_decrypt(session_keys->rtcp_cipher,
+                                     (uint8_t *)enc_start, &enc_octet_len);
+        if (status) {
+            return status;
+        }
+    } else {
+        /*
+         * Still need to run the cipher to check the tag
+         */
+        tmp_len = tag_len;
+        status = srtp_cipher_decrypt(session_keys->rtcp_cipher,
+                                     (uint8_t *)auth_tag, &tmp_len);
+        if (status) {
+            return status;
+        }
+    }
+
+    /* decrease the packet length by the length of the auth tag and seq_num*/
+    *pkt_octet_len -= (tag_len + sizeof(srtcp_trailer_t) + mki_size);
+
+    /*
+     * verify that stream is for received traffic - this check will
+     * detect SSRC collisions, since a stream that appears in both
+     * srtp_protect() and srtp_unprotect() will fail this test in one of
+     * those functions.
+     *
+     * we do this check *after* the authentication check, so that the
+     * latter check will catch any attempts to fool us into thinking
+     * that we've got a collision
+     */
+    if (stream->direction != dir_srtp_receiver) {
+        if (stream->direction == dir_unknown) {
+            stream->direction = dir_srtp_receiver;
+        } else {
+            srtp_handle_event(ctx, stream, event_ssrc_collision);
+        }
+    }
+
+    /*
+     * if the stream is a 'provisional' one, in which the template context
+     * is used, then we need to allocate a new stream at this point, since
+     * the authentication passed
+     */
+    if (stream == ctx->stream_template) {
+        srtp_stream_ctx_t *new_stream;
+
+        /*
+         * allocate and initialize a new stream
+         *
+         * note that we indicate failure if we can't allocate the new
+         * stream, and some implementations will want to not return
+         * failure here
+         */
+        status =
+            srtp_stream_clone(ctx->stream_template, hdr->ssrc, &new_stream);
+        if (status) {
+            return status;
+        }
+
+        /* add new stream to the head of the stream_list */
+        new_stream->next = ctx->stream_list;
+        ctx->stream_list = new_stream;
+
+        /* set stream (the pointer used in this function) */
+        stream = new_stream;
+    }
+
+    /* we've passed the authentication check, so add seq_num to the rdb */
+    srtp_rdb_add_index(&stream->rtcp_rdb, seq_num);
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_protect_rtcp(srtp_t ctx,
+                                    void *rtcp_hdr,
+                                    int *pkt_octet_len)
+{
+    return srtp_protect_rtcp_mki(ctx, rtcp_hdr, pkt_octet_len, 0, 0);
+}
+
+srtp_err_status_t srtp_protect_rtcp_mki(srtp_t ctx,
+                                        void *rtcp_hdr,
+                                        int *pkt_octet_len,
+                                        unsigned int use_mki,
+                                        unsigned int mki_index)
+{
+    srtcp_hdr_t *hdr = (srtcp_hdr_t *)rtcp_hdr;
+    uint32_t *enc_start;            /* pointer to start of encrypted portion  */
+    uint32_t *auth_start;           /* pointer to start of auth. portion      */
+    uint32_t *trailer_p;            /* pointer to start of trailer            */
+    uint32_t trailer;               /* trailer value                          */
+    unsigned int enc_octet_len = 0; /* number of octets in encrypted portion */
+    uint8_t *auth_tag = NULL;       /* location of auth_tag within packet     */
+    srtp_err_status_t status;
+    int tag_len;
+    srtp_stream_ctx_t *stream;
+    uint32_t prefix_len;
+    uint32_t seq_num;
+    unsigned int mki_size = 0;
+    srtp_session_keys_t *session_keys = NULL;
+
+    /* we assume the hdr is 32-bit aligned to start */
+
+    /* check the packet length - it must at least contain a full header */
+    if (*pkt_octet_len < octets_in_rtcp_header)
+        return srtp_err_status_bad_param;
+
+    /*
+     * look up ssrc in srtp_stream list, and process the packet with
+     * the appropriate stream.  if we haven't seen this stream before,
+     * there's only one key for this srtp_session, and the cipher
+     * supports key-sharing, then we assume that a new stream using
+     * that key has just started up
+     */
+    stream = srtp_get_stream(ctx, hdr->ssrc);
+    if (stream == NULL) {
+        if (ctx->stream_template != NULL) {
+            srtp_stream_ctx_t *new_stream;
+
+            /* allocate and initialize a new stream */
+            status =
+                srtp_stream_clone(ctx->stream_template, hdr->ssrc, &new_stream);
+            if (status)
+                return status;
+
+            /* add new stream to the head of the stream_list */
+            new_stream->next = ctx->stream_list;
+            ctx->stream_list = new_stream;
+
+            /* set stream (the pointer used in this function) */
+            stream = new_stream;
+        } else {
+            /* no template stream, so we return an error */
+            return srtp_err_status_no_ctx;
+        }
+    }
+
+    /*
+     * verify that stream is for sending traffic - this check will
+     * detect SSRC collisions, since a stream that appears in both
+     * srtp_protect() and srtp_unprotect() will fail this test in one of
+     * those functions.
+     */
+    if (stream->direction != dir_srtp_sender) {
+        if (stream->direction == dir_unknown) {
+            stream->direction = dir_srtp_sender;
+        } else {
+            srtp_handle_event(ctx, stream, event_ssrc_collision);
+        }
+    }
+
+    session_keys =
+        srtp_get_session_keys_with_mki_index(stream, use_mki, mki_index);
+
+    if (session_keys == NULL)
+        return srtp_err_status_bad_mki;
+
+    /*
+     * Check if this is an AEAD stream (GCM mode).  If so, then dispatch
+     * the request to our AEAD handler.
+     */
+    if (session_keys->rtp_cipher->algorithm == SRTP_AES_GCM_128 ||
+        session_keys->rtp_cipher->algorithm == SRTP_AES_GCM_256) {
+        return srtp_protect_rtcp_aead(ctx, stream, rtcp_hdr,
+                                      (unsigned int *)pkt_octet_len,
+                                      session_keys, use_mki);
+    }
+
+    /* get tag length from stream context */
+    tag_len = srtp_auth_get_tag_length(session_keys->rtcp_auth);
+
+    /*
+     * set encryption start and encryption length - if we're not
+     * providing confidentiality, set enc_start to NULL
+     */
+    enc_start = (uint32_t *)hdr + uint32s_in_rtcp_header;
+    enc_octet_len = *pkt_octet_len - octets_in_rtcp_header;
+
+    /* all of the packet, except the header, gets encrypted */
+    /*
+     * NOTE: hdr->length is not usable - it refers to only the first RTCP report
+     * in the compound packet!
+     */
+    trailer_p = (uint32_t *)((char *)enc_start + enc_octet_len);
+
+    if (stream->rtcp_services & sec_serv_conf) {
+        trailer = htonl(SRTCP_E_BIT); /* set encrypt bit */
+    } else {
+        enc_start = NULL;
+        enc_octet_len = 0;
+        /* 0 is network-order independant */
+        trailer = 0x00000000; /* set encrypt bit */
+    }
+
+    mki_size = srtp_inject_mki((uint8_t *)hdr + *pkt_octet_len +
+                                   sizeof(srtcp_trailer_t),
+                               session_keys, use_mki);
+
+    /*
+     * set the auth_start and auth_tag pointers to the proper locations
+     * (note that srtpc *always* provides authentication, unlike srtp)
+     */
+    /* Note: This would need to change for optional mikey data */
+    auth_start = (uint32_t *)hdr;
+    auth_tag =
+        (uint8_t *)hdr + *pkt_octet_len + sizeof(srtcp_trailer_t) + mki_size;
+
+    /*
+     * check sequence number for overruns, and copy it into the packet
+     * if its value isn't too big
+     */
+    status = srtp_rdb_increment(&stream->rtcp_rdb);
+    if (status)
+        return status;
+    seq_num = srtp_rdb_get_value(&stream->rtcp_rdb);
+    trailer |= htonl(seq_num);
+    debug_print(mod_srtp, "srtcp index: %x", seq_num);
+
+    memcpy(trailer_p, &trailer, sizeof(trailer));
+
+    /*
+     * if we're using rindael counter mode, set nonce and seq
+     */
+    if (session_keys->rtcp_cipher->type->id == SRTP_AES_ICM_128 ||
+        session_keys->rtcp_cipher->type->id == SRTP_AES_ICM_192 ||
+        session_keys->rtcp_cipher->type->id == SRTP_AES_ICM_256) {
+        v128_t iv;
+
+        iv.v32[0] = 0;
+        iv.v32[1] = hdr->ssrc; /* still in network order! */
+        iv.v32[2] = htonl(seq_num >> 16);
+        iv.v32[3] = htonl(seq_num << 16);
+        status = srtp_cipher_set_iv(session_keys->rtcp_cipher, (uint8_t *)&iv,
+                                    srtp_direction_encrypt);
+
+    } else {
+        v128_t iv;
+
+        /* otherwise, just set the index to seq_num */
+        iv.v32[0] = 0;
+        iv.v32[1] = 0;
+        iv.v32[2] = 0;
+        iv.v32[3] = htonl(seq_num);
+        status = srtp_cipher_set_iv(session_keys->rtcp_cipher, (uint8_t *)&iv,
+                                    srtp_direction_encrypt);
+    }
+    if (status)
+        return srtp_err_status_cipher_fail;
+
+    /*
+     * if we're authenticating using a universal hash, put the keystream
+     * prefix into the authentication tag
+     */
+
+    /* if auth_start is non-null, then put keystream into tag  */
+    if (auth_start) {
+        /* put keystream prefix into auth_tag */
+        prefix_len = srtp_auth_get_prefix_length(session_keys->rtcp_auth);
+        status = srtp_cipher_output(session_keys->rtcp_cipher, auth_tag,
+                                    &prefix_len);
+
+        debug_print(mod_srtp, "keystream prefix: %s",
+                    srtp_octet_string_hex_string(auth_tag, prefix_len));
+
+        if (status)
+            return srtp_err_status_cipher_fail;
+    }
+
+    /* if we're encrypting, exor keystream into the message */
+    if (enc_start) {
+        status = srtp_cipher_encrypt(session_keys->rtcp_cipher,
+                                     (uint8_t *)enc_start, &enc_octet_len);
+        if (status)
+            return srtp_err_status_cipher_fail;
+    }
+
+    /* initialize auth func context */
+    status = srtp_auth_start(session_keys->rtcp_auth);
+    if (status)
+        return status;
+
+    /*
+     * run auth func over packet (including trailer), and write the
+     * result at auth_tag
+     */
+    status =
+        srtp_auth_compute(session_keys->rtcp_auth, (uint8_t *)auth_start,
+                          (*pkt_octet_len) + sizeof(srtcp_trailer_t), auth_tag);
+    debug_print(mod_srtp, "srtcp auth tag:    %s",
+                srtp_octet_string_hex_string(auth_tag, tag_len));
+    if (status)
+        return srtp_err_status_auth_fail;
+
+    /* increase the packet length by the length of the auth tag and seq_num*/
+    *pkt_octet_len += (tag_len + sizeof(srtcp_trailer_t));
+
+    /* increase the packet by the mki_size */
+    *pkt_octet_len += mki_size;
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_unprotect_rtcp(srtp_t ctx,
+                                      void *srtcp_hdr,
+                                      int *pkt_octet_len)
+{
+    return srtp_unprotect_rtcp_mki(ctx, srtcp_hdr, pkt_octet_len, 0);
+}
+
+srtp_err_status_t srtp_unprotect_rtcp_mki(srtp_t ctx,
+                                          void *srtcp_hdr,
+                                          int *pkt_octet_len,
+                                          unsigned int use_mki)
+{
+    srtcp_hdr_t *hdr = (srtcp_hdr_t *)srtcp_hdr;
+    uint32_t *enc_start;            /* pointer to start of encrypted portion  */
+    uint32_t *auth_start;           /* pointer to start of auth. portion      */
+    uint32_t *trailer_p;            /* pointer to start of trailer            */
+    uint32_t trailer;               /* trailer value                          */
+    unsigned int enc_octet_len = 0; /* number of octets in encrypted portion */
+    uint8_t *auth_tag = NULL;       /* location of auth_tag within packet     */
+    uint8_t tmp_tag[SRTP_MAX_TAG_LEN];
+    srtp_err_status_t status;
+    unsigned int auth_len;
+    int tag_len;
+    srtp_stream_ctx_t *stream;
+    uint32_t prefix_len;
+    uint32_t seq_num;
+    int e_bit_in_packet; /* whether the E-bit was found in the packet */
+    int sec_serv_confidentiality; /* whether confidentiality was requested */
+    unsigned int mki_size = 0;
+    srtp_session_keys_t *session_keys = NULL;
+
+    /* we assume the hdr is 32-bit aligned to start */
+
+    if (*pkt_octet_len < 0)
+        return srtp_err_status_bad_param;
+
+    /*
+     * check that the length value is sane; we'll check again once we
+     * know the tag length, but we at least want to know that it is
+     * a positive value
+     */
+    if ((unsigned int)(*pkt_octet_len) <
+        octets_in_rtcp_header + sizeof(srtcp_trailer_t))
+        return srtp_err_status_bad_param;
+
+    /*
+     * look up ssrc in srtp_stream list, and process the packet with
+     * the appropriate stream.  if we haven't seen this stream before,
+     * there's only one key for this srtp_session, and the cipher
+     * supports key-sharing, then we assume that a new stream using
+     * that key has just started up
+     */
+    stream = srtp_get_stream(ctx, hdr->ssrc);
+    if (stream == NULL) {
+        if (ctx->stream_template != NULL) {
+            stream = ctx->stream_template;
+
+            debug_print(mod_srtp,
+                        "srtcp using provisional stream (SSRC: 0x%08x)",
+                        ntohl(hdr->ssrc));
+        } else {
+            /* no template stream, so we return an error */
+            return srtp_err_status_no_ctx;
+        }
+    }
+
+    /*
+     * Determine if MKI is being used and what session keys should be used
+     */
+    if (use_mki) {
+        session_keys = srtp_get_session_keys(
+            stream, (uint8_t *)hdr, (const unsigned int *)pkt_octet_len,
+            &mki_size);
+
+        if (session_keys == NULL)
+            return srtp_err_status_bad_mki;
+    } else {
+        session_keys = &stream->session_keys[0];
+    }
+
+    /* get tag length from stream context */
+    tag_len = srtp_auth_get_tag_length(session_keys->rtcp_auth);
+
+    /* check the packet length - it must contain at least a full RTCP
+       header, an auth tag (if applicable), and the SRTCP encrypted flag
+       and 31-bit index value */
+    if (*pkt_octet_len < (int)(octets_in_rtcp_header + tag_len + mki_size +
+                               sizeof(srtcp_trailer_t))) {
+        return srtp_err_status_bad_param;
+    }
+
+    /*
+     * Check if this is an AEAD stream (GCM mode).  If so, then dispatch
+     * the request to our AEAD handler.
+     */
+    if (session_keys->rtp_cipher->algorithm == SRTP_AES_GCM_128 ||
+        session_keys->rtp_cipher->algorithm == SRTP_AES_GCM_256) {
+        return srtp_unprotect_rtcp_aead(ctx, stream, srtcp_hdr,
+                                        (unsigned int *)pkt_octet_len,
+                                        session_keys, mki_size);
+    }
+
+    sec_serv_confidentiality = stream->rtcp_services == sec_serv_conf ||
+                               stream->rtcp_services == sec_serv_conf_and_auth;
+
+    /*
+     * set encryption start, encryption length, and trailer
+     */
+    enc_octet_len = *pkt_octet_len - (octets_in_rtcp_header + tag_len +
+                                      mki_size + sizeof(srtcp_trailer_t));
+    /*
+     *index & E (encryption) bit follow normal data. hdr->len is the number of
+     * words (32-bit) in the normal packet minus 1
+     */
+    /* This should point trailer to the word past the end of the normal data. */
+    /* This would need to be modified for optional mikey data */
+    trailer_p = (uint32_t *)((char *)hdr + *pkt_octet_len -
+                             (tag_len + mki_size + sizeof(srtcp_trailer_t)));
+    memcpy(&trailer, trailer_p, sizeof(trailer));
+
+    e_bit_in_packet =
+        (*((unsigned char *)trailer_p) & SRTCP_E_BYTE_BIT) == SRTCP_E_BYTE_BIT;
+    if (e_bit_in_packet != sec_serv_confidentiality) {
+        return srtp_err_status_cant_check;
+    }
+    if (sec_serv_confidentiality) {
+        enc_start = (uint32_t *)hdr + uint32s_in_rtcp_header;
+    } else {
+        enc_octet_len = 0;
+        enc_start = NULL; /* this indicates that there's no encryption */
+    }
+
+    /*
+     * set the auth_start and auth_tag pointers to the proper locations
+     * (note that srtcp *always* uses authentication, unlike srtp)
+     */
+    auth_start = (uint32_t *)hdr;
+
+    /*
+     * The location of the auth tag in the packet needs to know MKI
+     * could be present.  The data needed to calculate the Auth tag
+     * must not include the MKI
+     */
+    auth_len = *pkt_octet_len - tag_len - mki_size;
+    auth_tag = (uint8_t *)hdr + auth_len + mki_size;
+
+    /*
+     * check the sequence number for replays
+     */
+    /* this is easier than dealing with bitfield access */
+    seq_num = ntohl(trailer) & SRTCP_INDEX_MASK;
+    debug_print(mod_srtp, "srtcp index: %x", seq_num);
+    status = srtp_rdb_check(&stream->rtcp_rdb, seq_num);
+    if (status)
+        return status;
+
+    /*
+     * if we're using aes counter mode, set nonce and seq
+     */
+    if (session_keys->rtcp_cipher->type->id == SRTP_AES_ICM_128 ||
+        session_keys->rtcp_cipher->type->id == SRTP_AES_ICM_192 ||
+        session_keys->rtcp_cipher->type->id == SRTP_AES_ICM_256) {
+        v128_t iv;
+
+        iv.v32[0] = 0;
+        iv.v32[1] = hdr->ssrc; /* still in network order! */
+        iv.v32[2] = htonl(seq_num >> 16);
+        iv.v32[3] = htonl(seq_num << 16);
+        status = srtp_cipher_set_iv(session_keys->rtcp_cipher, (uint8_t *)&iv,
+                                    srtp_direction_decrypt);
+
+    } else {
+        v128_t iv;
+
+        /* otherwise, just set the index to seq_num */
+        iv.v32[0] = 0;
+        iv.v32[1] = 0;
+        iv.v32[2] = 0;
+        iv.v32[3] = htonl(seq_num);
+        status = srtp_cipher_set_iv(session_keys->rtcp_cipher, (uint8_t *)&iv,
+                                    srtp_direction_decrypt);
+    }
+    if (status)
+        return srtp_err_status_cipher_fail;
+
+    /* initialize auth func context */
+    status = srtp_auth_start(session_keys->rtcp_auth);
+    if (status)
+        return status;
+
+    /* run auth func over packet, put result into tmp_tag */
+    status = srtp_auth_compute(session_keys->rtcp_auth, (uint8_t *)auth_start,
+                               auth_len, tmp_tag);
+    debug_print(mod_srtp, "srtcp computed tag:       %s",
+                srtp_octet_string_hex_string(tmp_tag, tag_len));
+    if (status)
+        return srtp_err_status_auth_fail;
+
+    /* compare the tag just computed with the one in the packet */
+    debug_print(mod_srtp, "srtcp tag from packet:    %s",
+                srtp_octet_string_hex_string(auth_tag, tag_len));
+    if (srtp_octet_string_is_eq(tmp_tag, auth_tag, tag_len))
+        return srtp_err_status_auth_fail;
+
+    /*
+     * if we're authenticating using a universal hash, put the keystream
+     * prefix into the authentication tag
+     */
+    prefix_len = srtp_auth_get_prefix_length(session_keys->rtcp_auth);
+    if (prefix_len) {
+        status = srtp_cipher_output(session_keys->rtcp_cipher, auth_tag,
+                                    &prefix_len);
+        debug_print(mod_srtp, "keystream prefix: %s",
+                    srtp_octet_string_hex_string(auth_tag, prefix_len));
+        if (status)
+            return srtp_err_status_cipher_fail;
+    }
+
+    /* if we're decrypting, exor keystream into the message */
+    if (enc_start) {
+        status = srtp_cipher_decrypt(session_keys->rtcp_cipher,
+                                     (uint8_t *)enc_start, &enc_octet_len);
+        if (status)
+            return srtp_err_status_cipher_fail;
+    }
+
+    /* decrease the packet length by the length of the auth tag and seq_num */
+    *pkt_octet_len -= (tag_len + sizeof(srtcp_trailer_t));
+
+    /* decrease the packet length by the length of the mki_size */
+    *pkt_octet_len -= mki_size;
+
+    /*
+     * verify that stream is for received traffic - this check will
+     * detect SSRC collisions, since a stream that appears in both
+     * srtp_protect() and srtp_unprotect() will fail this test in one of
+     * those functions.
+     *
+     * we do this check *after* the authentication check, so that the
+     * latter check will catch any attempts to fool us into thinking
+     * that we've got a collision
+     */
+    if (stream->direction != dir_srtp_receiver) {
+        if (stream->direction == dir_unknown) {
+            stream->direction = dir_srtp_receiver;
+        } else {
+            srtp_handle_event(ctx, stream, event_ssrc_collision);
+        }
+    }
+
+    /*
+     * if the stream is a 'provisional' one, in which the template context
+     * is used, then we need to allocate a new stream at this point, since
+     * the authentication passed
+     */
+    if (stream == ctx->stream_template) {
+        srtp_stream_ctx_t *new_stream;
+
+        /*
+         * allocate and initialize a new stream
+         *
+         * note that we indicate failure if we can't allocate the new
+         * stream, and some implementations will want to not return
+         * failure here
+         */
+        status =
+            srtp_stream_clone(ctx->stream_template, hdr->ssrc, &new_stream);
+        if (status)
+            return status;
+
+        /* add new stream to the head of the stream_list */
+        new_stream->next = ctx->stream_list;
+        ctx->stream_list = new_stream;
+
+        /* set stream (the pointer used in this function) */
+        stream = new_stream;
+    }
+
+    /* we've passed the authentication check, so add seq_num to the rdb */
+    srtp_rdb_add_index(&stream->rtcp_rdb, seq_num);
+
+    return srtp_err_status_ok;
+}
+
+/*
+ * user data within srtp_t context
+ */
+
+void srtp_set_user_data(srtp_t ctx, void *data)
+{
+    ctx->user_data = data;
+}
+
+void *srtp_get_user_data(srtp_t ctx)
+{
+    return ctx->user_data;
+}
+
+srtp_err_status_t srtp_crypto_policy_set_from_profile_for_rtp(
+    srtp_crypto_policy_t *policy,
+    srtp_profile_t profile)
+{
+    /* set SRTP policy from the SRTP profile in the key set */
+    switch (profile) {
+    case srtp_profile_aes128_cm_sha1_80:
+        srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80(policy);
+        break;
+    case srtp_profile_aes128_cm_sha1_32:
+        srtp_crypto_policy_set_aes_cm_128_hmac_sha1_32(policy);
+        break;
+    case srtp_profile_null_sha1_80:
+        srtp_crypto_policy_set_null_cipher_hmac_sha1_80(policy);
+        break;
+#ifdef GCM
+    case srtp_profile_aead_aes_128_gcm:
+        srtp_crypto_policy_set_aes_gcm_128_16_auth(policy);
+        break;
+    case srtp_profile_aead_aes_256_gcm:
+        srtp_crypto_policy_set_aes_gcm_256_16_auth(policy);
+        break;
+#endif
+    /* the following profiles are not (yet) supported */
+    case srtp_profile_null_sha1_32:
+    default:
+        return srtp_err_status_bad_param;
+    }
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_crypto_policy_set_from_profile_for_rtcp(
+    srtp_crypto_policy_t *policy,
+    srtp_profile_t profile)
+{
+    /* set SRTP policy from the SRTP profile in the key set */
+    switch (profile) {
+    case srtp_profile_aes128_cm_sha1_80:
+        srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80(policy);
+        break;
+    case srtp_profile_aes128_cm_sha1_32:
+        /* We do not honor the 32-bit auth tag request since
+         * this is not compliant with RFC 3711 */
+        srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80(policy);
+        break;
+    case srtp_profile_null_sha1_80:
+        srtp_crypto_policy_set_null_cipher_hmac_sha1_80(policy);
+        break;
+#ifdef GCM
+    case srtp_profile_aead_aes_128_gcm:
+        srtp_crypto_policy_set_aes_gcm_128_16_auth(policy);
+        break;
+    case srtp_profile_aead_aes_256_gcm:
+        srtp_crypto_policy_set_aes_gcm_256_16_auth(policy);
+        break;
+#endif
+    /* the following profiles are not (yet) supported */
+    case srtp_profile_null_sha1_32:
+    default:
+        return srtp_err_status_bad_param;
+    }
+
+    return srtp_err_status_ok;
+}
+
+void srtp_append_salt_to_key(uint8_t *key,
+                             unsigned int bytes_in_key,
+                             uint8_t *salt,
+                             unsigned int bytes_in_salt)
+{
+    memcpy(key + bytes_in_key, salt, bytes_in_salt);
+}
+
+unsigned int srtp_profile_get_master_key_length(srtp_profile_t profile)
+{
+    switch (profile) {
+    case srtp_profile_aes128_cm_sha1_80:
+        return SRTP_AES_128_KEY_LEN;
+        break;
+    case srtp_profile_aes128_cm_sha1_32:
+        return SRTP_AES_128_KEY_LEN;
+        break;
+    case srtp_profile_null_sha1_80:
+        return SRTP_AES_128_KEY_LEN;
+        break;
+    case srtp_profile_aead_aes_128_gcm:
+        return SRTP_AES_128_KEY_LEN;
+        break;
+    case srtp_profile_aead_aes_256_gcm:
+        return SRTP_AES_256_KEY_LEN;
+        break;
+    /* the following profiles are not (yet) supported */
+    case srtp_profile_null_sha1_32:
+    default:
+        return 0; /* indicate error by returning a zero */
+    }
+}
+
+unsigned int srtp_profile_get_master_salt_length(srtp_profile_t profile)
+{
+    switch (profile) {
+    case srtp_profile_aes128_cm_sha1_80:
+        return SRTP_SALT_LEN;
+        break;
+    case srtp_profile_aes128_cm_sha1_32:
+        return SRTP_SALT_LEN;
+        break;
+    case srtp_profile_null_sha1_80:
+        return SRTP_SALT_LEN;
+        break;
+    case srtp_profile_aead_aes_128_gcm:
+        return SRTP_AEAD_SALT_LEN;
+        break;
+    case srtp_profile_aead_aes_256_gcm:
+        return SRTP_AEAD_SALT_LEN;
+        break;
+    /* the following profiles are not (yet) supported */
+    case srtp_profile_null_sha1_32:
+    default:
+        return 0; /* indicate error by returning a zero */
+    }
+}
+
+srtp_err_status_t stream_get_protect_trailer_length(srtp_stream_ctx_t *stream,
+                                                    uint32_t is_rtp,
+                                                    uint32_t use_mki,
+                                                    uint32_t mki_index,
+                                                    uint32_t *length)
+{
+    srtp_session_keys_t *session_key;
+
+    *length = 0;
+
+    if (use_mki) {
+        if (mki_index >= stream->num_master_keys) {
+            return srtp_err_status_bad_mki;
+        }
+        session_key = &stream->session_keys[mki_index];
+
+        *length += session_key->mki_size;
+
+    } else {
+        session_key = &stream->session_keys[0];
+    }
+    if (is_rtp) {
+        *length += srtp_auth_get_tag_length(session_key->rtp_auth);
+    } else {
+        *length += srtp_auth_get_tag_length(session_key->rtcp_auth);
+        *length += sizeof(srtcp_trailer_t);
+    }
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t get_protect_trailer_length(srtp_t session,
+                                             uint32_t is_rtp,
+                                             uint32_t use_mki,
+                                             uint32_t mki_index,
+                                             uint32_t *length)
+{
+    srtp_stream_ctx_t *stream;
+
+    if (session == NULL) {
+        return srtp_err_status_bad_param;
+    }
+
+    if (session->stream_template == NULL && session->stream_list == NULL) {
+        return srtp_err_status_bad_param;
+    }
+
+    *length = 0;
+
+    stream = session->stream_template;
+
+    if (stream != NULL) {
+        stream_get_protect_trailer_length(stream, is_rtp, use_mki, mki_index,
+                                          length);
+    }
+
+    stream = session->stream_list;
+
+    while (stream != NULL) {
+        uint32_t temp_length;
+        if (stream_get_protect_trailer_length(stream, is_rtp, use_mki,
+                                              mki_index, &temp_length) ==
+            srtp_err_status_ok) {
+            if (temp_length > *length) {
+                *length = temp_length;
+            }
+        }
+        stream = stream->next;
+    }
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_get_protect_trailer_length(srtp_t session,
+                                                  uint32_t use_mki,
+                                                  uint32_t mki_index,
+                                                  uint32_t *length)
+{
+    return get_protect_trailer_length(session, 1, use_mki, mki_index, length);
+}
+
+srtp_err_status_t srtp_get_protect_rtcp_trailer_length(srtp_t session,
+                                                       uint32_t use_mki,
+                                                       uint32_t mki_index,
+                                                       uint32_t *length)
+{
+    return get_protect_trailer_length(session, 0, use_mki, mki_index, length);
+}
+
+/*
+ * SRTP debug interface
+ */
+srtp_err_status_t srtp_set_debug_module(const char *mod_name, int v)
+{
+    return srtp_crypto_kernel_set_debug_module(mod_name, v);
+}
+
+srtp_err_status_t srtp_list_debug_modules(void)
+{
+    return srtp_crypto_kernel_list_debug_modules();
+}
+
+/*
+ * srtp_log_handler is a global variable holding a pointer to the
+ * log handler function; this function is called for any log
+ * output.
+ */
+
+static srtp_log_handler_func_t *srtp_log_handler = NULL;
+static void *srtp_log_handler_data = NULL;
+
+void srtp_err_handler(srtp_err_reporting_level_t level, const char *msg)
+{
+    if (srtp_log_handler) {
+        srtp_log_level_t log_level = srtp_log_level_error;
+        switch (level) {
+        case srtp_err_level_error:
+            log_level = srtp_log_level_error;
+            break;
+        case srtp_err_level_warning:
+            log_level = srtp_log_level_warning;
+            break;
+        case srtp_err_level_info:
+            log_level = srtp_log_level_info;
+            break;
+        case srtp_err_level_debug:
+            log_level = srtp_log_level_debug;
+            break;
+        }
+
+        srtp_log_handler(log_level, msg, srtp_log_handler_data);
+    }
+}
+
+srtp_err_status_t srtp_install_log_handler(srtp_log_handler_func_t func,
+                                           void *data)
+{
+    /*
+     * note that we accept NULL arguments intentionally - calling this
+     * function with a NULL arguments removes a log handler that's
+     * been previously installed
+     */
+
+    if (srtp_log_handler) {
+        srtp_install_err_report_handler(NULL);
+    }
+    srtp_log_handler = func;
+    srtp_log_handler_data = data;
+    if (srtp_log_handler) {
+        srtp_install_err_report_handler(srtp_err_handler);
+    }
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_set_stream_roc(srtp_t session,
+                                      uint32_t ssrc,
+                                      uint32_t roc)
+{
+    srtp_stream_t stream;
+
+    stream = srtp_get_stream(session, htonl(ssrc));
+    if (stream == NULL)
+        return srtp_err_status_bad_param;
+
+    stream->pending_roc = roc;
+
+    return srtp_err_status_ok;
+}
+
+srtp_err_status_t srtp_get_stream_roc(srtp_t session,
+                                      uint32_t ssrc,
+                                      uint32_t *roc)
+{
+    srtp_stream_t stream;
+
+    stream = srtp_get_stream(session, htonl(ssrc));
+    if (stream == NULL)
+        return srtp_err_status_bad_param;
+
+    *roc = srtp_rdbx_get_roc(&stream->rtp_rdbx);
+
+    return srtp_err_status_ok;
+}