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-rw-r--r--kex.c1043
1 files changed, 1043 insertions, 0 deletions
diff --git a/kex.c b/kex.c
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+++ b/kex.c
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+/* $OpenBSD: kex.c,v 1.141 2018/07/09 13:37:10 sf Exp $ */
+/*
+ * Copyright (c) 2000, 2001 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 <signal.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifdef WITH_OPENSSL
+#include <openssl/crypto.h>
+#include <openssl/dh.h>
+#endif
+
+#include "ssh2.h"
+#include "packet.h"
+#include "compat.h"
+#include "cipher.h"
+#include "sshkey.h"
+#include "kex.h"
+#include "log.h"
+#include "mac.h"
+#include "match.h"
+#include "misc.h"
+#include "dispatch.h"
+#include "monitor.h"
+
+#include "ssherr.h"
+#include "sshbuf.h"
+#include "digest.h"
+
+/* prototype */
+static int kex_choose_conf(struct ssh *);
+static int kex_input_newkeys(int, u_int32_t, struct ssh *);
+
+static const char *proposal_names[PROPOSAL_MAX] = {
+ "KEX algorithms",
+ "host key algorithms",
+ "ciphers ctos",
+ "ciphers stoc",
+ "MACs ctos",
+ "MACs stoc",
+ "compression ctos",
+ "compression stoc",
+ "languages ctos",
+ "languages stoc",
+};
+
+struct kexalg {
+ char *name;
+ u_int type;
+ int ec_nid;
+ int hash_alg;
+};
+static const struct kexalg kexalgs[] = {
+#ifdef WITH_OPENSSL
+ { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
+ { KEX_DH14_SHA1, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
+ { KEX_DH14_SHA256, KEX_DH_GRP14_SHA256, 0, SSH_DIGEST_SHA256 },
+ { KEX_DH16_SHA512, KEX_DH_GRP16_SHA512, 0, SSH_DIGEST_SHA512 },
+ { KEX_DH18_SHA512, KEX_DH_GRP18_SHA512, 0, SSH_DIGEST_SHA512 },
+ { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
+#ifdef HAVE_EVP_SHA256
+ { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
+#endif /* HAVE_EVP_SHA256 */
+#ifdef OPENSSL_HAS_ECC
+ { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
+ NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
+ { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
+ SSH_DIGEST_SHA384 },
+# ifdef OPENSSL_HAS_NISTP521
+ { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
+ SSH_DIGEST_SHA512 },
+# endif /* OPENSSL_HAS_NISTP521 */
+#endif /* OPENSSL_HAS_ECC */
+#endif /* WITH_OPENSSL */
+#if defined(HAVE_EVP_SHA256) || !defined(WITH_OPENSSL)
+ { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
+ { KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
+#endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */
+ { NULL, -1, -1, -1},
+};
+
+char *
+kex_alg_list(char sep)
+{
+ char *ret = NULL, *tmp;
+ size_t nlen, rlen = 0;
+ const struct kexalg *k;
+
+ for (k = kexalgs; k->name != NULL; k++) {
+ if (ret != NULL)
+ ret[rlen++] = sep;
+ nlen = strlen(k->name);
+ if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
+ free(ret);
+ return NULL;
+ }
+ ret = tmp;
+ memcpy(ret + rlen, k->name, nlen + 1);
+ rlen += nlen;
+ }
+ return ret;
+}
+
+static const struct kexalg *
+kex_alg_by_name(const char *name)
+{
+ const struct kexalg *k;
+
+ for (k = kexalgs; k->name != NULL; k++) {
+ if (strcmp(k->name, name) == 0)
+ return k;
+ }
+ return NULL;
+}
+
+/* Validate KEX method name list */
+int
+kex_names_valid(const char *names)
+{
+ char *s, *cp, *p;
+
+ if (names == NULL || strcmp(names, "") == 0)
+ return 0;
+ if ((s = cp = strdup(names)) == NULL)
+ return 0;
+ for ((p = strsep(&cp, ",")); p && *p != '\0';
+ (p = strsep(&cp, ","))) {
+ if (kex_alg_by_name(p) == NULL) {
+ error("Unsupported KEX algorithm \"%.100s\"", p);
+ free(s);
+ return 0;
+ }
+ }
+ debug3("kex names ok: [%s]", names);
+ free(s);
+ return 1;
+}
+
+/*
+ * Concatenate algorithm names, avoiding duplicates in the process.
+ * Caller must free returned string.
+ */
+char *
+kex_names_cat(const char *a, const char *b)
+{
+ char *ret = NULL, *tmp = NULL, *cp, *p, *m;
+ size_t len;
+
+ if (a == NULL || *a == '\0')
+ return strdup(b);
+ if (b == NULL || *b == '\0')
+ return strdup(a);
+ if (strlen(b) > 1024*1024)
+ return NULL;
+ len = strlen(a) + strlen(b) + 2;
+ if ((tmp = cp = strdup(b)) == NULL ||
+ (ret = calloc(1, len)) == NULL) {
+ free(tmp);
+ return NULL;
+ }
+ strlcpy(ret, a, len);
+ for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
+ if ((m = match_list(ret, p, NULL)) != NULL) {
+ free(m);
+ continue; /* Algorithm already present */
+ }
+ if (strlcat(ret, ",", len) >= len ||
+ strlcat(ret, p, len) >= len) {
+ free(tmp);
+ free(ret);
+ return NULL; /* Shouldn't happen */
+ }
+ }
+ free(tmp);
+ return ret;
+}
+
+/*
+ * Assemble a list of algorithms from a default list and a string from a
+ * configuration file. The user-provided string may begin with '+' to
+ * indicate that it should be appended to the default or '-' that the
+ * specified names should be removed.
+ */
+int
+kex_assemble_names(char **listp, const char *def, const char *all)
+{
+ char *cp, *tmp, *patterns;
+ char *list = NULL, *ret = NULL, *matching = NULL, *opatterns = NULL;
+ int r = SSH_ERR_INTERNAL_ERROR;
+
+ if (listp == NULL || *listp == NULL || **listp == '\0') {
+ if ((*listp = strdup(def)) == NULL)
+ return SSH_ERR_ALLOC_FAIL;
+ return 0;
+ }
+
+ list = *listp;
+ *listp = NULL;
+ if (*list == '+') {
+ /* Append names to default list */
+ if ((tmp = kex_names_cat(def, list + 1)) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto fail;
+ }
+ free(list);
+ list = tmp;
+ } else if (*list == '-') {
+ /* Remove names from default list */
+ if ((*listp = match_filter_blacklist(def, list + 1)) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto fail;
+ }
+ free(list);
+ /* filtering has already been done */
+ return 0;
+ } else {
+ /* Explicit list, overrides default - just use "list" as is */
+ }
+
+ /*
+ * The supplied names may be a pattern-list. For the -list case,
+ * the patterns are applied above. For the +list and explicit list
+ * cases we need to do it now.
+ */
+ ret = NULL;
+ if ((patterns = opatterns = strdup(list)) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto fail;
+ }
+ /* Apply positive (i.e. non-negated) patterns from the list */
+ while ((cp = strsep(&patterns, ",")) != NULL) {
+ if (*cp == '!') {
+ /* negated matches are not supported here */
+ r = SSH_ERR_INVALID_ARGUMENT;
+ goto fail;
+ }
+ free(matching);
+ if ((matching = match_filter_whitelist(all, cp)) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto fail;
+ }
+ if ((tmp = kex_names_cat(ret, matching)) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto fail;
+ }
+ free(ret);
+ ret = tmp;
+ }
+ if (ret == NULL || *ret == '\0') {
+ /* An empty name-list is an error */
+ /* XXX better error code? */
+ r = SSH_ERR_INVALID_ARGUMENT;
+ goto fail;
+ }
+
+ /* success */
+ *listp = ret;
+ ret = NULL;
+ r = 0;
+
+ fail:
+ free(matching);
+ free(opatterns);
+ free(list);
+ free(ret);
+ return r;
+}
+
+/* put algorithm proposal into buffer */
+int
+kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
+{
+ u_int i;
+ int r;
+
+ sshbuf_reset(b);
+
+ /*
+ * add a dummy cookie, the cookie will be overwritten by
+ * kex_send_kexinit(), each time a kexinit is set
+ */
+ for (i = 0; i < KEX_COOKIE_LEN; i++) {
+ if ((r = sshbuf_put_u8(b, 0)) != 0)
+ return r;
+ }
+ for (i = 0; i < PROPOSAL_MAX; i++) {
+ if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
+ return r;
+ }
+ if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */
+ (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */
+ return r;
+ return 0;
+}
+
+/* parse buffer and return algorithm proposal */
+int
+kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
+{
+ struct sshbuf *b = NULL;
+ u_char v;
+ u_int i;
+ char **proposal = NULL;
+ int r;
+
+ *propp = NULL;
+ if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
+ return SSH_ERR_ALLOC_FAIL;
+ if ((b = sshbuf_fromb(raw)) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+ if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
+ goto out;
+ /* extract kex init proposal strings */
+ for (i = 0; i < PROPOSAL_MAX; i++) {
+ if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
+ goto out;
+ debug2("%s: %s", proposal_names[i], proposal[i]);
+ }
+ /* first kex follows / reserved */
+ if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */
+ (r = sshbuf_get_u32(b, &i)) != 0) /* reserved */
+ goto out;
+ if (first_kex_follows != NULL)
+ *first_kex_follows = v;
+ debug2("first_kex_follows %d ", v);
+ debug2("reserved %u ", i);
+ r = 0;
+ *propp = proposal;
+ out:
+ if (r != 0 && proposal != NULL)
+ kex_prop_free(proposal);
+ sshbuf_free(b);
+ return r;
+}
+
+void
+kex_prop_free(char **proposal)
+{
+ u_int i;
+
+ if (proposal == NULL)
+ return;
+ for (i = 0; i < PROPOSAL_MAX; i++)
+ free(proposal[i]);
+ free(proposal);
+}
+
+/* ARGSUSED */
+static int
+kex_protocol_error(int type, u_int32_t seq, struct ssh *ssh)
+{
+ int r;
+
+ error("kex protocol error: type %d seq %u", type, seq);
+ if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
+ (r = sshpkt_put_u32(ssh, seq)) != 0 ||
+ (r = sshpkt_send(ssh)) != 0)
+ return r;
+ return 0;
+}
+
+static void
+kex_reset_dispatch(struct ssh *ssh)
+{
+ ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
+ SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
+}
+
+static int
+kex_send_ext_info(struct ssh *ssh)
+{
+ int r;
+ char *algs;
+
+ if ((algs = sshkey_alg_list(0, 1, 1, ',')) == NULL)
+ return SSH_ERR_ALLOC_FAIL;
+ /* XXX filter algs list by allowed pubkey/hostbased types */
+ if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 ||
+ (r = sshpkt_put_u32(ssh, 1)) != 0 ||
+ (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
+ (r = sshpkt_put_cstring(ssh, algs)) != 0 ||
+ (r = sshpkt_send(ssh)) != 0)
+ goto out;
+ /* success */
+ r = 0;
+ out:
+ free(algs);
+ return r;
+}
+
+int
+kex_send_newkeys(struct ssh *ssh)
+{
+ int r;
+
+ kex_reset_dispatch(ssh);
+ if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
+ (r = sshpkt_send(ssh)) != 0)
+ return r;
+ debug("SSH2_MSG_NEWKEYS sent");
+ debug("expecting SSH2_MSG_NEWKEYS");
+ ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
+ if (ssh->kex->ext_info_c)
+ if ((r = kex_send_ext_info(ssh)) != 0)
+ return r;
+ return 0;
+}
+
+int
+kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
+{
+ struct kex *kex = ssh->kex;
+ u_int32_t i, ninfo;
+ char *name;
+ u_char *val;
+ size_t vlen;
+ int r;
+
+ debug("SSH2_MSG_EXT_INFO received");
+ ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
+ if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
+ return r;
+ for (i = 0; i < ninfo; i++) {
+ if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
+ return r;
+ if ((r = sshpkt_get_string(ssh, &val, &vlen)) != 0) {
+ free(name);
+ return r;
+ }
+ if (strcmp(name, "server-sig-algs") == 0) {
+ /* Ensure no \0 lurking in value */
+ if (memchr(val, '\0', vlen) != NULL) {
+ error("%s: nul byte in %s", __func__, name);
+ return SSH_ERR_INVALID_FORMAT;
+ }
+ debug("%s: %s=<%s>", __func__, name, val);
+ kex->server_sig_algs = val;
+ val = NULL;
+ } else
+ debug("%s: %s (unrecognised)", __func__, name);
+ free(name);
+ free(val);
+ }
+ return sshpkt_get_end(ssh);
+}
+
+static int
+kex_input_newkeys(int type, u_int32_t seq, struct ssh *ssh)
+{
+ struct kex *kex = ssh->kex;
+ int r;
+
+ debug("SSH2_MSG_NEWKEYS received");
+ ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
+ ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
+ if ((r = sshpkt_get_end(ssh)) != 0)
+ return r;
+ if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0)
+ return r;
+ kex->done = 1;
+ sshbuf_reset(kex->peer);
+ /* sshbuf_reset(kex->my); */
+ kex->flags &= ~KEX_INIT_SENT;
+ free(kex->name);
+ kex->name = NULL;
+ return 0;
+}
+
+int
+kex_send_kexinit(struct ssh *ssh)
+{
+ u_char *cookie;
+ struct kex *kex = ssh->kex;
+ int r;
+
+ if (kex == NULL)
+ return SSH_ERR_INTERNAL_ERROR;
+ if (kex->flags & KEX_INIT_SENT)
+ return 0;
+ kex->done = 0;
+
+ /* generate a random cookie */
+ if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
+ return SSH_ERR_INVALID_FORMAT;
+ if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
+ return SSH_ERR_INTERNAL_ERROR;
+ arc4random_buf(cookie, KEX_COOKIE_LEN);
+
+ if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
+ (r = sshpkt_putb(ssh, kex->my)) != 0 ||
+ (r = sshpkt_send(ssh)) != 0)
+ return r;
+ debug("SSH2_MSG_KEXINIT sent");
+ kex->flags |= KEX_INIT_SENT;
+ return 0;
+}
+
+/* ARGSUSED */
+int
+kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh)
+{
+ struct kex *kex = ssh->kex;
+ const u_char *ptr;
+ u_int i;
+ size_t dlen;
+ int r;
+
+ debug("SSH2_MSG_KEXINIT received");
+ if (kex == NULL)
+ return SSH_ERR_INVALID_ARGUMENT;
+
+ ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
+ ptr = sshpkt_ptr(ssh, &dlen);
+ if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
+ return r;
+
+ /* discard packet */
+ for (i = 0; i < KEX_COOKIE_LEN; i++)
+ if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
+ return r;
+ for (i = 0; i < PROPOSAL_MAX; i++)
+ if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
+ return r;
+ /*
+ * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
+ * KEX method has the server move first, but a server might be using
+ * a custom method or one that we otherwise don't support. We should
+ * be prepared to remember first_kex_follows here so we can eat a
+ * packet later.
+ * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
+ * for cases where the server *doesn't* go first. I guess we should
+ * ignore it when it is set for these cases, which is what we do now.
+ */
+ if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */
+ (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */
+ (r = sshpkt_get_end(ssh)) != 0)
+ return r;
+
+ if (!(kex->flags & KEX_INIT_SENT))
+ if ((r = kex_send_kexinit(ssh)) != 0)
+ return r;
+ if ((r = kex_choose_conf(ssh)) != 0)
+ return r;
+
+ if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
+ return (kex->kex[kex->kex_type])(ssh);
+
+ return SSH_ERR_INTERNAL_ERROR;
+}
+
+int
+kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
+{
+ struct kex *kex;
+ int r;
+
+ *kexp = NULL;
+ if ((kex = calloc(1, sizeof(*kex))) == NULL)
+ return SSH_ERR_ALLOC_FAIL;
+ if ((kex->peer = sshbuf_new()) == NULL ||
+ (kex->my = sshbuf_new()) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+ if ((r = kex_prop2buf(kex->my, proposal)) != 0)
+ goto out;
+ kex->done = 0;
+ kex_reset_dispatch(ssh);
+ ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
+ r = 0;
+ *kexp = kex;
+ out:
+ if (r != 0)
+ kex_free(kex);
+ return r;
+}
+
+void
+kex_free_newkeys(struct newkeys *newkeys)
+{
+ if (newkeys == NULL)
+ return;
+ if (newkeys->enc.key) {
+ explicit_bzero(newkeys->enc.key, newkeys->enc.key_len);
+ free(newkeys->enc.key);
+ newkeys->enc.key = NULL;
+ }
+ if (newkeys->enc.iv) {
+ explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len);
+ free(newkeys->enc.iv);
+ newkeys->enc.iv = NULL;
+ }
+ free(newkeys->enc.name);
+ explicit_bzero(&newkeys->enc, sizeof(newkeys->enc));
+ free(newkeys->comp.name);
+ explicit_bzero(&newkeys->comp, sizeof(newkeys->comp));
+ mac_clear(&newkeys->mac);
+ if (newkeys->mac.key) {
+ explicit_bzero(newkeys->mac.key, newkeys->mac.key_len);
+ free(newkeys->mac.key);
+ newkeys->mac.key = NULL;
+ }
+ free(newkeys->mac.name);
+ explicit_bzero(&newkeys->mac, sizeof(newkeys->mac));
+ explicit_bzero(newkeys, sizeof(*newkeys));
+ free(newkeys);
+}
+
+void
+kex_free(struct kex *kex)
+{
+ u_int mode;
+
+#ifdef WITH_OPENSSL
+ DH_free(kex->dh);
+#ifdef OPENSSL_HAS_ECC
+ EC_KEY_free(kex->ec_client_key);
+#endif /* OPENSSL_HAS_ECC */
+#endif /* WITH_OPENSSL */
+ for (mode = 0; mode < MODE_MAX; mode++) {
+ kex_free_newkeys(kex->newkeys[mode]);
+ kex->newkeys[mode] = NULL;
+ }
+ sshbuf_free(kex->peer);
+ sshbuf_free(kex->my);
+ free(kex->session_id);
+ free(kex->client_version_string);
+ free(kex->server_version_string);
+ free(kex->failed_choice);
+ free(kex->hostkey_alg);
+ free(kex->name);
+ free(kex);
+}
+
+int
+kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
+{
+ int r;
+
+ if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
+ return r;
+ if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */
+ kex_free(ssh->kex);
+ ssh->kex = NULL;
+ return r;
+ }
+ return 0;
+}
+
+/*
+ * Request key re-exchange, returns 0 on success or a ssherr.h error
+ * code otherwise. Must not be called if KEX is incomplete or in-progress.
+ */
+int
+kex_start_rekex(struct ssh *ssh)
+{
+ if (ssh->kex == NULL) {
+ error("%s: no kex", __func__);
+ return SSH_ERR_INTERNAL_ERROR;
+ }
+ if (ssh->kex->done == 0) {
+ error("%s: requested twice", __func__);
+ return SSH_ERR_INTERNAL_ERROR;
+ }
+ ssh->kex->done = 0;
+ return kex_send_kexinit(ssh);
+}
+
+static int
+choose_enc(struct sshenc *enc, char *client, char *server)
+{
+ char *name = match_list(client, server, NULL);
+
+ if (name == NULL)
+ return SSH_ERR_NO_CIPHER_ALG_MATCH;
+ if ((enc->cipher = cipher_by_name(name)) == NULL) {
+ free(name);
+ return SSH_ERR_INTERNAL_ERROR;
+ }
+ enc->name = name;
+ enc->enabled = 0;
+ enc->iv = NULL;
+ enc->iv_len = cipher_ivlen(enc->cipher);
+ enc->key = NULL;
+ enc->key_len = cipher_keylen(enc->cipher);
+ enc->block_size = cipher_blocksize(enc->cipher);
+ return 0;
+}
+
+static int
+choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
+{
+ char *name = match_list(client, server, NULL);
+
+ if (name == NULL)
+ return SSH_ERR_NO_MAC_ALG_MATCH;
+ if (mac_setup(mac, name) < 0) {
+ free(name);
+ return SSH_ERR_INTERNAL_ERROR;
+ }
+ mac->name = name;
+ mac->key = NULL;
+ mac->enabled = 0;
+ return 0;
+}
+
+static int
+choose_comp(struct sshcomp *comp, char *client, char *server)
+{
+ char *name = match_list(client, server, NULL);
+
+ if (name == NULL)
+ return SSH_ERR_NO_COMPRESS_ALG_MATCH;
+ if (strcmp(name, "zlib@openssh.com") == 0) {
+ comp->type = COMP_DELAYED;
+ } else if (strcmp(name, "zlib") == 0) {
+ comp->type = COMP_ZLIB;
+ } else if (strcmp(name, "none") == 0) {
+ comp->type = COMP_NONE;
+ } else {
+ free(name);
+ return SSH_ERR_INTERNAL_ERROR;
+ }
+ comp->name = name;
+ return 0;
+}
+
+static int
+choose_kex(struct kex *k, char *client, char *server)
+{
+ const struct kexalg *kexalg;
+
+ k->name = match_list(client, server, NULL);
+
+ debug("kex: algorithm: %s", k->name ? k->name : "(no match)");
+ if (k->name == NULL)
+ return SSH_ERR_NO_KEX_ALG_MATCH;
+ if ((kexalg = kex_alg_by_name(k->name)) == NULL)
+ return SSH_ERR_INTERNAL_ERROR;
+ k->kex_type = kexalg->type;
+ k->hash_alg = kexalg->hash_alg;
+ k->ec_nid = kexalg->ec_nid;
+ return 0;
+}
+
+static int
+choose_hostkeyalg(struct kex *k, char *client, char *server)
+{
+ k->hostkey_alg = match_list(client, server, NULL);
+
+ debug("kex: host key algorithm: %s",
+ k->hostkey_alg ? k->hostkey_alg : "(no match)");
+ if (k->hostkey_alg == NULL)
+ return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
+ k->hostkey_type = sshkey_type_from_name(k->hostkey_alg);
+ if (k->hostkey_type == KEY_UNSPEC)
+ return SSH_ERR_INTERNAL_ERROR;
+ k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg);
+ return 0;
+}
+
+static int
+proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
+{
+ static int check[] = {
+ PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
+ };
+ int *idx;
+ char *p;
+
+ for (idx = &check[0]; *idx != -1; idx++) {
+ if ((p = strchr(my[*idx], ',')) != NULL)
+ *p = '\0';
+ if ((p = strchr(peer[*idx], ',')) != NULL)
+ *p = '\0';
+ if (strcmp(my[*idx], peer[*idx]) != 0) {
+ debug2("proposal mismatch: my %s peer %s",
+ my[*idx], peer[*idx]);
+ return (0);
+ }
+ }
+ debug2("proposals match");
+ return (1);
+}
+
+static int
+kex_choose_conf(struct ssh *ssh)
+{
+ struct kex *kex = ssh->kex;
+ struct newkeys *newkeys;
+ char **my = NULL, **peer = NULL;
+ char **cprop, **sprop;
+ int nenc, nmac, ncomp;
+ u_int mode, ctos, need, dh_need, authlen;
+ int r, first_kex_follows;
+
+ debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
+ if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
+ goto out;
+ debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
+ if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
+ goto out;
+
+ if (kex->server) {
+ cprop=peer;
+ sprop=my;
+ } else {
+ cprop=my;
+ sprop=peer;
+ }
+
+ /* Check whether client supports ext_info_c */
+ if (kex->server) {
+ char *ext;
+
+ ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
+ kex->ext_info_c = (ext != NULL);
+ free(ext);
+ }
+
+ /* Algorithm Negotiation */
+ if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
+ sprop[PROPOSAL_KEX_ALGS])) != 0) {
+ kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
+ peer[PROPOSAL_KEX_ALGS] = NULL;
+ goto out;
+ }
+ if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
+ sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
+ kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
+ peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
+ goto out;
+ }
+ for (mode = 0; mode < MODE_MAX; mode++) {
+ if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+ kex->newkeys[mode] = newkeys;
+ ctos = (!kex->server && mode == MODE_OUT) ||
+ (kex->server && mode == MODE_IN);
+ nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
+ nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
+ ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
+ if ((r = choose_enc(&newkeys->enc, cprop[nenc],
+ sprop[nenc])) != 0) {
+ kex->failed_choice = peer[nenc];
+ peer[nenc] = NULL;
+ goto out;
+ }
+ authlen = cipher_authlen(newkeys->enc.cipher);
+ /* ignore mac for authenticated encryption */
+ if (authlen == 0 &&
+ (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
+ sprop[nmac])) != 0) {
+ kex->failed_choice = peer[nmac];
+ peer[nmac] = NULL;
+ goto out;
+ }
+ if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
+ sprop[ncomp])) != 0) {
+ kex->failed_choice = peer[ncomp];
+ peer[ncomp] = NULL;
+ goto out;
+ }
+ debug("kex: %s cipher: %s MAC: %s compression: %s",
+ ctos ? "client->server" : "server->client",
+ newkeys->enc.name,
+ authlen == 0 ? newkeys->mac.name : "<implicit>",
+ newkeys->comp.name);
+ }
+ need = dh_need = 0;
+ for (mode = 0; mode < MODE_MAX; mode++) {
+ newkeys = kex->newkeys[mode];
+ need = MAXIMUM(need, newkeys->enc.key_len);
+ need = MAXIMUM(need, newkeys->enc.block_size);
+ need = MAXIMUM(need, newkeys->enc.iv_len);
+ need = MAXIMUM(need, newkeys->mac.key_len);
+ dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
+ dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
+ dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
+ dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
+ }
+ /* XXX need runden? */
+ kex->we_need = need;
+ kex->dh_need = dh_need;
+
+ /* ignore the next message if the proposals do not match */
+ if (first_kex_follows && !proposals_match(my, peer))
+ ssh->dispatch_skip_packets = 1;
+ r = 0;
+ out:
+ kex_prop_free(my);
+ kex_prop_free(peer);
+ return r;
+}
+
+static int
+derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
+ const struct sshbuf *shared_secret, u_char **keyp)
+{
+ struct kex *kex = ssh->kex;
+ struct ssh_digest_ctx *hashctx = NULL;
+ char c = id;
+ u_int have;
+ size_t mdsz;
+ u_char *digest;
+ int r;
+
+ if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
+ return SSH_ERR_INVALID_ARGUMENT;
+ if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+
+ /* K1 = HASH(K || H || "A" || session_id) */
+ if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
+ ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
+ ssh_digest_update(hashctx, hash, hashlen) != 0 ||
+ ssh_digest_update(hashctx, &c, 1) != 0 ||
+ ssh_digest_update(hashctx, kex->session_id,
+ kex->session_id_len) != 0 ||
+ ssh_digest_final(hashctx, digest, mdsz) != 0) {
+ r = SSH_ERR_LIBCRYPTO_ERROR;
+ goto out;
+ }
+ ssh_digest_free(hashctx);
+ hashctx = NULL;
+
+ /*
+ * expand key:
+ * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
+ * Key = K1 || K2 || ... || Kn
+ */
+ for (have = mdsz; need > have; have += mdsz) {
+ if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
+ ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
+ ssh_digest_update(hashctx, hash, hashlen) != 0 ||
+ ssh_digest_update(hashctx, digest, have) != 0 ||
+ ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
+ r = SSH_ERR_LIBCRYPTO_ERROR;
+ goto out;
+ }
+ ssh_digest_free(hashctx);
+ hashctx = NULL;
+ }
+#ifdef DEBUG_KEX
+ fprintf(stderr, "key '%c'== ", c);
+ dump_digest("key", digest, need);
+#endif
+ *keyp = digest;
+ digest = NULL;
+ r = 0;
+ out:
+ free(digest);
+ ssh_digest_free(hashctx);
+ return r;
+}
+
+#define NKEYS 6
+int
+kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
+ const struct sshbuf *shared_secret)
+{
+ struct kex *kex = ssh->kex;
+ u_char *keys[NKEYS];
+ u_int i, j, mode, ctos;
+ int r;
+
+ for (i = 0; i < NKEYS; i++) {
+ if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
+ shared_secret, &keys[i])) != 0) {
+ for (j = 0; j < i; j++)
+ free(keys[j]);
+ return r;
+ }
+ }
+ for (mode = 0; mode < MODE_MAX; mode++) {
+ ctos = (!kex->server && mode == MODE_OUT) ||
+ (kex->server && mode == MODE_IN);
+ kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1];
+ kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
+ kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
+ }
+ return 0;
+}
+
+#ifdef WITH_OPENSSL
+int
+kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
+ const BIGNUM *secret)
+{
+ struct sshbuf *shared_secret;
+ int r;
+
+ if ((shared_secret = sshbuf_new()) == NULL)
+ return SSH_ERR_ALLOC_FAIL;
+ if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
+ r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
+ sshbuf_free(shared_secret);
+ return r;
+}
+#endif
+
+
+#if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
+void
+dump_digest(char *msg, u_char *digest, int len)
+{
+ fprintf(stderr, "%s\n", msg);
+ sshbuf_dump_data(digest, len, stderr);
+}
+#endif