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-rw-r--r--cipher.c526
1 files changed, 526 insertions, 0 deletions
diff --git a/cipher.c b/cipher.c
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+/* $OpenBSD: cipher.c,v 1.119 2021/04/03 06:18:40 djm Exp $ */
+/*
+ * Author: Tatu Ylonen <ylo@cs.hut.fi>
+ * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+ * All rights reserved
+ *
+ * As far as I am concerned, the code I have written for this software
+ * can be used freely for any purpose. Any derived versions of this
+ * software must be clearly marked as such, and if the derived work is
+ * incompatible with the protocol description in the RFC file, it must be
+ * called by a name other than "ssh" or "Secure Shell".
+ *
+ *
+ * Copyright (c) 1999 Niels Provos. All rights reserved.
+ * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
+ */
+
+#include "includes.h"
+
+#include <sys/types.h>
+
+#include <string.h>
+#include <stdarg.h>
+#include <stdio.h>
+
+#include "cipher.h"
+#include "misc.h"
+#include "sshbuf.h"
+#include "ssherr.h"
+#include "digest.h"
+
+#include "openbsd-compat/openssl-compat.h"
+
+#ifndef WITH_OPENSSL
+#define EVP_CIPHER_CTX void
+#endif
+
+struct sshcipher_ctx {
+ int plaintext;
+ int encrypt;
+ EVP_CIPHER_CTX *evp;
+ struct chachapoly_ctx *cp_ctx;
+ struct aesctr_ctx ac_ctx; /* XXX union with evp? */
+ const struct sshcipher *cipher;
+};
+
+struct sshcipher {
+ char *name;
+ u_int block_size;
+ u_int key_len;
+ u_int iv_len; /* defaults to block_size */
+ u_int auth_len;
+ u_int flags;
+#define CFLAG_CBC (1<<0)
+#define CFLAG_CHACHAPOLY (1<<1)
+#define CFLAG_AESCTR (1<<2)
+#define CFLAG_NONE (1<<3)
+#define CFLAG_INTERNAL CFLAG_NONE /* Don't use "none" for packets */
+#ifdef WITH_OPENSSL
+ const EVP_CIPHER *(*evptype)(void);
+#else
+ void *ignored;
+#endif
+};
+
+static const struct sshcipher ciphers[] = {
+#ifdef WITH_OPENSSL
+#ifndef OPENSSL_NO_DES
+ { "3des-cbc", 8, 24, 0, 0, CFLAG_CBC, EVP_des_ede3_cbc },
+#endif
+ { "aes128-cbc", 16, 16, 0, 0, CFLAG_CBC, EVP_aes_128_cbc },
+ { "aes192-cbc", 16, 24, 0, 0, CFLAG_CBC, EVP_aes_192_cbc },
+ { "aes256-cbc", 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc },
+ { "aes128-ctr", 16, 16, 0, 0, 0, EVP_aes_128_ctr },
+ { "aes192-ctr", 16, 24, 0, 0, 0, EVP_aes_192_ctr },
+ { "aes256-ctr", 16, 32, 0, 0, 0, EVP_aes_256_ctr },
+ { "aes128-gcm@openssh.com",
+ 16, 16, 12, 16, 0, EVP_aes_128_gcm },
+ { "aes256-gcm@openssh.com",
+ 16, 32, 12, 16, 0, EVP_aes_256_gcm },
+#else
+ { "aes128-ctr", 16, 16, 0, 0, CFLAG_AESCTR, NULL },
+ { "aes192-ctr", 16, 24, 0, 0, CFLAG_AESCTR, NULL },
+ { "aes256-ctr", 16, 32, 0, 0, CFLAG_AESCTR, NULL },
+#endif
+ { "chacha20-poly1305@openssh.com",
+ 8, 64, 0, 16, CFLAG_CHACHAPOLY, NULL },
+ { "none", 8, 0, 0, 0, CFLAG_NONE, NULL },
+
+ { NULL, 0, 0, 0, 0, 0, NULL }
+};
+
+/*--*/
+
+/* Returns a comma-separated list of supported ciphers. */
+char *
+cipher_alg_list(char sep, int auth_only)
+{
+ char *tmp, *ret = NULL;
+ size_t nlen, rlen = 0;
+ const struct sshcipher *c;
+
+ for (c = ciphers; c->name != NULL; c++) {
+ if ((c->flags & CFLAG_INTERNAL) != 0)
+ continue;
+ if (auth_only && c->auth_len == 0)
+ continue;
+ if (ret != NULL)
+ ret[rlen++] = sep;
+ nlen = strlen(c->name);
+ if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
+ free(ret);
+ return NULL;
+ }
+ ret = tmp;
+ memcpy(ret + rlen, c->name, nlen + 1);
+ rlen += nlen;
+ }
+ return ret;
+}
+
+const char *
+compression_alg_list(int compression)
+{
+#ifdef WITH_ZLIB
+ return compression ? "zlib@openssh.com,zlib,none" :
+ "none,zlib@openssh.com,zlib";
+#else
+ return "none";
+#endif
+}
+
+u_int
+cipher_blocksize(const struct sshcipher *c)
+{
+ return (c->block_size);
+}
+
+u_int
+cipher_keylen(const struct sshcipher *c)
+{
+ return (c->key_len);
+}
+
+u_int
+cipher_seclen(const struct sshcipher *c)
+{
+ if (strcmp("3des-cbc", c->name) == 0)
+ return 14;
+ return cipher_keylen(c);
+}
+
+u_int
+cipher_authlen(const struct sshcipher *c)
+{
+ return (c->auth_len);
+}
+
+u_int
+cipher_ivlen(const struct sshcipher *c)
+{
+ /*
+ * Default is cipher block size, except for chacha20+poly1305 that
+ * needs no IV. XXX make iv_len == -1 default?
+ */
+ return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ?
+ c->iv_len : c->block_size;
+}
+
+u_int
+cipher_is_cbc(const struct sshcipher *c)
+{
+ return (c->flags & CFLAG_CBC) != 0;
+}
+
+u_int
+cipher_ctx_is_plaintext(struct sshcipher_ctx *cc)
+{
+ return cc->plaintext;
+}
+
+const struct sshcipher *
+cipher_by_name(const char *name)
+{
+ const struct sshcipher *c;
+ for (c = ciphers; c->name != NULL; c++)
+ if (strcmp(c->name, name) == 0)
+ return c;
+ return NULL;
+}
+
+#define CIPHER_SEP ","
+int
+ciphers_valid(const char *names)
+{
+ const struct sshcipher *c;
+ char *cipher_list, *cp;
+ char *p;
+
+ if (names == NULL || strcmp(names, "") == 0)
+ return 0;
+ if ((cipher_list = cp = strdup(names)) == NULL)
+ return 0;
+ for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
+ (p = strsep(&cp, CIPHER_SEP))) {
+ c = cipher_by_name(p);
+ if (c == NULL || (c->flags & CFLAG_INTERNAL) != 0) {
+ free(cipher_list);
+ return 0;
+ }
+ }
+ free(cipher_list);
+ return 1;
+}
+
+const char *
+cipher_warning_message(const struct sshcipher_ctx *cc)
+{
+ if (cc == NULL || cc->cipher == NULL)
+ return NULL;
+ /* XXX repurpose for CBC warning */
+ return NULL;
+}
+
+int
+cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher,
+ const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
+ int do_encrypt)
+{
+ struct sshcipher_ctx *cc = NULL;
+ int ret = SSH_ERR_INTERNAL_ERROR;
+#ifdef WITH_OPENSSL
+ const EVP_CIPHER *type;
+ int klen;
+#endif
+
+ *ccp = NULL;
+ if ((cc = calloc(sizeof(*cc), 1)) == NULL)
+ return SSH_ERR_ALLOC_FAIL;
+
+ cc->plaintext = (cipher->flags & CFLAG_NONE) != 0;
+ cc->encrypt = do_encrypt;
+
+ if (keylen < cipher->key_len ||
+ (iv != NULL && ivlen < cipher_ivlen(cipher))) {
+ ret = SSH_ERR_INVALID_ARGUMENT;
+ goto out;
+ }
+
+ cc->cipher = cipher;
+ if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
+ cc->cp_ctx = chachapoly_new(key, keylen);
+ ret = cc->cp_ctx != NULL ? 0 : SSH_ERR_INVALID_ARGUMENT;
+ goto out;
+ }
+ if ((cc->cipher->flags & CFLAG_NONE) != 0) {
+ ret = 0;
+ goto out;
+ }
+#ifndef WITH_OPENSSL
+ if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
+ aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen);
+ aesctr_ivsetup(&cc->ac_ctx, iv);
+ ret = 0;
+ goto out;
+ }
+ ret = SSH_ERR_INVALID_ARGUMENT;
+ goto out;
+#else /* WITH_OPENSSL */
+ type = (*cipher->evptype)();
+ if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) {
+ ret = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+ if (EVP_CipherInit(cc->evp, type, NULL, (u_char *)iv,
+ (do_encrypt == CIPHER_ENCRYPT)) == 0) {
+ ret = SSH_ERR_LIBCRYPTO_ERROR;
+ goto out;
+ }
+ if (cipher_authlen(cipher) &&
+ !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED,
+ -1, (u_char *)iv)) {
+ ret = SSH_ERR_LIBCRYPTO_ERROR;
+ goto out;
+ }
+ klen = EVP_CIPHER_CTX_key_length(cc->evp);
+ if (klen > 0 && keylen != (u_int)klen) {
+ if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) {
+ ret = SSH_ERR_LIBCRYPTO_ERROR;
+ goto out;
+ }
+ }
+ if (EVP_CipherInit(cc->evp, NULL, (u_char *)key, NULL, -1) == 0) {
+ ret = SSH_ERR_LIBCRYPTO_ERROR;
+ goto out;
+ }
+ ret = 0;
+#endif /* WITH_OPENSSL */
+ out:
+ if (ret == 0) {
+ /* success */
+ *ccp = cc;
+ } else {
+ if (cc != NULL) {
+#ifdef WITH_OPENSSL
+ EVP_CIPHER_CTX_free(cc->evp);
+#endif /* WITH_OPENSSL */
+ freezero(cc, sizeof(*cc));
+ }
+ }
+ return ret;
+}
+
+/*
+ * cipher_crypt() operates as following:
+ * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'.
+ * These bytes are treated as additional authenticated data for
+ * authenticated encryption modes.
+ * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'.
+ * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag.
+ * This tag is written on encryption and verified on decryption.
+ * Both 'aadlen' and 'authlen' can be set to 0.
+ */
+int
+cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest,
+ const u_char *src, u_int len, u_int aadlen, u_int authlen)
+{
+ if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
+ return chachapoly_crypt(cc->cp_ctx, seqnr, dest, src,
+ len, aadlen, authlen, cc->encrypt);
+ }
+ if ((cc->cipher->flags & CFLAG_NONE) != 0) {
+ memcpy(dest, src, aadlen + len);
+ return 0;
+ }
+#ifndef WITH_OPENSSL
+ if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
+ if (aadlen)
+ memcpy(dest, src, aadlen);
+ aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen,
+ dest + aadlen, len);
+ return 0;
+ }
+ return SSH_ERR_INVALID_ARGUMENT;
+#else
+ if (authlen) {
+ u_char lastiv[1];
+
+ if (authlen != cipher_authlen(cc->cipher))
+ return SSH_ERR_INVALID_ARGUMENT;
+ /* increment IV */
+ if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN,
+ 1, lastiv))
+ return SSH_ERR_LIBCRYPTO_ERROR;
+ /* set tag on decyption */
+ if (!cc->encrypt &&
+ !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG,
+ authlen, (u_char *)src + aadlen + len))
+ return SSH_ERR_LIBCRYPTO_ERROR;
+ }
+ if (aadlen) {
+ if (authlen &&
+ EVP_Cipher(cc->evp, NULL, (u_char *)src, aadlen) < 0)
+ return SSH_ERR_LIBCRYPTO_ERROR;
+ memcpy(dest, src, aadlen);
+ }
+ if (len % cc->cipher->block_size)
+ return SSH_ERR_INVALID_ARGUMENT;
+ if (EVP_Cipher(cc->evp, dest + aadlen, (u_char *)src + aadlen,
+ len) < 0)
+ return SSH_ERR_LIBCRYPTO_ERROR;
+ if (authlen) {
+ /* compute tag (on encrypt) or verify tag (on decrypt) */
+ if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0)
+ return cc->encrypt ?
+ SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID;
+ if (cc->encrypt &&
+ !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG,
+ authlen, dest + aadlen + len))
+ return SSH_ERR_LIBCRYPTO_ERROR;
+ }
+ return 0;
+#endif
+}
+
+/* Extract the packet length, including any decryption necessary beforehand */
+int
+cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr,
+ const u_char *cp, u_int len)
+{
+ if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
+ return chachapoly_get_length(cc->cp_ctx, plenp, seqnr,
+ cp, len);
+ if (len < 4)
+ return SSH_ERR_MESSAGE_INCOMPLETE;
+ *plenp = PEEK_U32(cp);
+ return 0;
+}
+
+void
+cipher_free(struct sshcipher_ctx *cc)
+{
+ if (cc == NULL)
+ return;
+ if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
+ chachapoly_free(cc->cp_ctx);
+ cc->cp_ctx = NULL;
+ } else if ((cc->cipher->flags & CFLAG_AESCTR) != 0)
+ explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx));
+#ifdef WITH_OPENSSL
+ EVP_CIPHER_CTX_free(cc->evp);
+ cc->evp = NULL;
+#endif
+ freezero(cc, sizeof(*cc));
+}
+
+/*
+ * Exports an IV from the sshcipher_ctx required to export the key
+ * state back from the unprivileged child to the privileged parent
+ * process.
+ */
+int
+cipher_get_keyiv_len(const struct sshcipher_ctx *cc)
+{
+ const struct sshcipher *c = cc->cipher;
+
+ if ((c->flags & CFLAG_CHACHAPOLY) != 0)
+ return 0;
+ else if ((c->flags & CFLAG_AESCTR) != 0)
+ return sizeof(cc->ac_ctx.ctr);
+#ifdef WITH_OPENSSL
+ return EVP_CIPHER_CTX_iv_length(cc->evp);
+#else
+ return 0;
+#endif
+}
+
+int
+cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, size_t len)
+{
+#ifdef WITH_OPENSSL
+ const struct sshcipher *c = cc->cipher;
+ int evplen;
+#endif
+
+ if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
+ if (len != 0)
+ return SSH_ERR_INVALID_ARGUMENT;
+ return 0;
+ }
+ if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
+ if (len != sizeof(cc->ac_ctx.ctr))
+ return SSH_ERR_INVALID_ARGUMENT;
+ memcpy(iv, cc->ac_ctx.ctr, len);
+ return 0;
+ }
+ if ((cc->cipher->flags & CFLAG_NONE) != 0)
+ return 0;
+
+#ifdef WITH_OPENSSL
+ evplen = EVP_CIPHER_CTX_iv_length(cc->evp);
+ if (evplen == 0)
+ return 0;
+ else if (evplen < 0)
+ return SSH_ERR_LIBCRYPTO_ERROR;
+ if ((size_t)evplen != len)
+ return SSH_ERR_INVALID_ARGUMENT;
+ if (cipher_authlen(c)) {
+ if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN,
+ len, iv))
+ return SSH_ERR_LIBCRYPTO_ERROR;
+ } else if (!EVP_CIPHER_CTX_get_iv(cc->evp, iv, len))
+ return SSH_ERR_LIBCRYPTO_ERROR;
+#endif
+ return 0;
+}
+
+int
+cipher_set_keyiv(struct sshcipher_ctx *cc, const u_char *iv, size_t len)
+{
+#ifdef WITH_OPENSSL
+ const struct sshcipher *c = cc->cipher;
+ int evplen = 0;
+#endif
+
+ if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
+ return 0;
+ if ((cc->cipher->flags & CFLAG_NONE) != 0)
+ return 0;
+
+#ifdef WITH_OPENSSL
+ evplen = EVP_CIPHER_CTX_iv_length(cc->evp);
+ if (evplen <= 0)
+ return SSH_ERR_LIBCRYPTO_ERROR;
+ if ((size_t)evplen != len)
+ return SSH_ERR_INVALID_ARGUMENT;
+ if (cipher_authlen(c)) {
+ /* XXX iv arg is const, but EVP_CIPHER_CTX_ctrl isn't */
+ if (!EVP_CIPHER_CTX_ctrl(cc->evp,
+ EVP_CTRL_GCM_SET_IV_FIXED, -1, (void *)iv))
+ return SSH_ERR_LIBCRYPTO_ERROR;
+ } else if (!EVP_CIPHER_CTX_set_iv(cc->evp, iv, evplen))
+ return SSH_ERR_LIBCRYPTO_ERROR;
+#endif
+ return 0;
+}
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