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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 14:40:04 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 14:40:04 +0000
commit25505898530a333011f4fd5cbc841ad6b26c089c (patch)
tree333a33fdd60930bcccc3f177ed9467d535e9bac6 /kex.c
parentInitial commit. (diff)
downloadopenssh-upstream/1%9.2p1.tar.xz
openssh-upstream/1%9.2p1.zip
Adding upstream version 1:9.2p1.upstream/1%9.2p1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'kex.c')
-rw-r--r--kex.c1421
1 files changed, 1421 insertions, 0 deletions
diff --git a/kex.c b/kex.c
new file mode 100644
index 0000000..8cdefcf
--- /dev/null
+++ b/kex.c
@@ -0,0 +1,1421 @@
+/* $OpenBSD: kex.c,v 1.173 2022/11/07 10:05:38 dtucker 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 <sys/types.h>
+#include <errno.h>
+#include <signal.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#ifdef HAVE_POLL_H
+#include <poll.h>
+#endif
+
+#ifdef WITH_OPENSSL
+#include <openssl/crypto.h>
+#include <openssl/dh.h>
+#endif
+
+#include "ssh.h"
+#include "ssh2.h"
+#include "atomicio.h"
+#include "version.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 * const 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 },
+#ifdef USE_SNTRUP761X25519
+ { KEX_SNTRUP761X25519_SHA512, KEX_KEM_SNTRUP761X25519_SHA512, 0,
+ SSH_DIGEST_SHA512 },
+#endif
+#endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */
+ { NULL, 0, -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, '-' that the
+ * specified names should be removed, or '^' that they should be placed
+ * at the head.
+ */
+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 || def == NULL || all == NULL)
+ return SSH_ERR_INVALID_ARGUMENT;
+
+ if (*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_denylist(def, list + 1)) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto fail;
+ }
+ free(list);
+ /* filtering has already been done */
+ return 0;
+ } else if (*list == '^') {
+ /* Place names at head of default list */
+ if ((tmp = kex_names_cat(list + 1, def)) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto fail;
+ }
+ free(list);
+ list = tmp;
+ } 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_allowlist(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 */
+ error_fr(r, "consume 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) {
+ error_fr(r, "parse proposal %u", i);
+ 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 */
+ error_fr(r, "parse");
+ 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 */
+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;
+
+ debug("Sending SSH2_MSG_EXT_INFO");
+ 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, 2)) != 0 ||
+ (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 ||
+ (r = sshpkt_put_cstring(ssh, algs)) != 0 ||
+ (r = sshpkt_put_cstring(ssh,
+ "publickey-hostbound@openssh.com")) != 0 ||
+ (r = sshpkt_put_cstring(ssh, "0")) != 0 ||
+ (r = sshpkt_send(ssh)) != 0) {
+ error_fr(r, "compose");
+ 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");
+ ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
+ if (ssh->kex->ext_info_c && (ssh->kex->flags & KEX_INITIAL) != 0)
+ if ((r = kex_send_ext_info(ssh)) != 0)
+ return r;
+ debug("expecting SSH2_MSG_NEWKEYS");
+ 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_f("nul byte in %s", name);
+ return SSH_ERR_INVALID_FORMAT;
+ }
+ debug_f("%s=<%s>", name, val);
+ kex->server_sig_algs = val;
+ val = NULL;
+ } else if (strcmp(name,
+ "publickey-hostbound@openssh.com") == 0) {
+ /* XXX refactor */
+ /* Ensure no \0 lurking in value */
+ if (memchr(val, '\0', vlen) != NULL) {
+ error_f("nul byte in %s", name);
+ return SSH_ERR_INVALID_FORMAT;
+ }
+ debug_f("%s=<%s>", name, val);
+ if (strcmp(val, "0") == 0)
+ kex->flags |= KEX_HAS_PUBKEY_HOSTBOUND;
+ else {
+ debug_f("unsupported version of %s extension",
+ name);
+ }
+ } else
+ debug_f("%s (unrecognised)", 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;
+ kex->flags &= ~KEX_INITIAL;
+ 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) {
+ error_f("no kex");
+ 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) {
+ error_f("bad kex length: %zu < %d",
+ sshbuf_len(kex->my), KEX_COOKIE_LEN);
+ return SSH_ERR_INVALID_FORMAT;
+ }
+ if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL) {
+ error_f("buffer error");
+ 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) {
+ error_fr(r, "compose reply");
+ 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) {
+ error_f("no kex");
+ return SSH_ERR_INTERNAL_ERROR;
+ }
+ 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) {
+ error_fr(r, "discard cookie");
+ return r;
+ }
+ }
+ for (i = 0; i < PROPOSAL_MAX; i++) {
+ if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0) {
+ error_fr(r, "discard proposal");
+ 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);
+
+ error_f("unknown kex type %u", kex->kex_type);
+ return SSH_ERR_INTERNAL_ERROR;
+}
+
+struct kex *
+kex_new(void)
+{
+ struct kex *kex;
+
+ if ((kex = calloc(1, sizeof(*kex))) == NULL ||
+ (kex->peer = sshbuf_new()) == NULL ||
+ (kex->my = sshbuf_new()) == NULL ||
+ (kex->client_version = sshbuf_new()) == NULL ||
+ (kex->server_version = sshbuf_new()) == NULL ||
+ (kex->session_id = sshbuf_new()) == NULL) {
+ kex_free(kex);
+ return NULL;
+ }
+ return kex;
+}
+
+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));
+ freezero(newkeys, sizeof(*newkeys));
+}
+
+void
+kex_free(struct kex *kex)
+{
+ u_int mode;
+
+ if (kex == NULL)
+ return;
+
+#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);
+ sshbuf_free(kex->client_version);
+ sshbuf_free(kex->server_version);
+ sshbuf_free(kex->client_pub);
+ sshbuf_free(kex->session_id);
+ sshbuf_free(kex->initial_sig);
+ sshkey_free(kex->initial_hostkey);
+ free(kex->failed_choice);
+ free(kex->hostkey_alg);
+ free(kex->name);
+ free(kex);
+}
+
+int
+kex_ready(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
+{
+ int r;
+
+ if ((r = kex_prop2buf(ssh->kex->my, proposal)) != 0)
+ return r;
+ ssh->kex->flags = KEX_INITIAL;
+ kex_reset_dispatch(ssh);
+ ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
+ return 0;
+}
+
+int
+kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
+{
+ int r;
+
+ if ((r = kex_ready(ssh, proposal)) != 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_f("no kex");
+ return SSH_ERR_INTERNAL_ERROR;
+ }
+ if (ssh->kex->done == 0) {
+ error_f("requested twice");
+ 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) {
+ error_f("unsupported cipher %s", name);
+ 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) {
+ error_f("unsupported MAC %s", name);
+ 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;
+#ifdef WITH_ZLIB
+ if (strcmp(name, "zlib@openssh.com") == 0) {
+ comp->type = COMP_DELAYED;
+ } else if (strcmp(name, "zlib") == 0) {
+ comp->type = COMP_ZLIB;
+ } else
+#endif /* WITH_ZLIB */
+ if (strcmp(name, "none") == 0) {
+ comp->type = COMP_NONE;
+ } else {
+ error_f("unsupported compression scheme %s", name);
+ 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) {
+ error_f("unsupported KEX method %s", k->name);
+ 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)
+{
+ free(k->hostkey_alg);
+ 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) {
+ error_f("unsupported hostkey algorithm %s", k->hostkey_alg);
+ 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);
+}
+
+/* returns non-zero if proposal contains any algorithm from algs */
+static int
+has_any_alg(const char *proposal, const char *algs)
+{
+ char *cp;
+
+ if ((cp = match_list(proposal, algs, NULL)) == NULL)
+ return 0;
+ free(cp);
+ 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 && (kex->flags & KEX_INITIAL)) {
+ char *ext;
+
+ ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
+ kex->ext_info_c = (ext != NULL);
+ free(ext);
+ }
+
+ /* Check whether client supports rsa-sha2 algorithms */
+ if (kex->server && (kex->flags & KEX_INITIAL)) {
+ if (has_any_alg(peer[PROPOSAL_SERVER_HOST_KEY_ALGS],
+ "rsa-sha2-256,rsa-sha2-256-cert-v01@openssh.com"))
+ kex->flags |= KEX_RSA_SHA2_256_SUPPORTED;
+ if (has_any_alg(peer[PROPOSAL_SERVER_HOST_KEY_ALGS],
+ "rsa-sha2-512,rsa-sha2-512-cert-v01@openssh.com"))
+ kex->flags |= KEX_RSA_SHA2_512_SUPPORTED;
+ }
+
+ /* 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_buffer(hashctx, kex->session_id) != 0 ||
+ ssh_digest_final(hashctx, digest, mdsz) != 0) {
+ r = SSH_ERR_LIBCRYPTO_ERROR;
+ error_f("KEX hash failed");
+ 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) {
+ error_f("KDF failed");
+ 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;
+
+ /* save initial hash as session id */
+ if ((kex->flags & KEX_INITIAL) != 0) {
+ if (sshbuf_len(kex->session_id) != 0) {
+ error_f("already have session ID at kex");
+ return SSH_ERR_INTERNAL_ERROR;
+ }
+ if ((r = sshbuf_put(kex->session_id, hash, hashlen)) != 0)
+ return r;
+ } else if (sshbuf_len(kex->session_id) == 0) {
+ error_f("no session ID in rekex");
+ return SSH_ERR_INTERNAL_ERROR;
+ }
+ 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;
+}
+
+int
+kex_load_hostkey(struct ssh *ssh, struct sshkey **prvp, struct sshkey **pubp)
+{
+ struct kex *kex = ssh->kex;
+
+ *pubp = NULL;
+ *prvp = NULL;
+ if (kex->load_host_public_key == NULL ||
+ kex->load_host_private_key == NULL) {
+ error_f("missing hostkey loader");
+ return SSH_ERR_INVALID_ARGUMENT;
+ }
+ *pubp = kex->load_host_public_key(kex->hostkey_type,
+ kex->hostkey_nid, ssh);
+ *prvp = kex->load_host_private_key(kex->hostkey_type,
+ kex->hostkey_nid, ssh);
+ if (*pubp == NULL)
+ return SSH_ERR_NO_HOSTKEY_LOADED;
+ return 0;
+}
+
+int
+kex_verify_host_key(struct ssh *ssh, struct sshkey *server_host_key)
+{
+ struct kex *kex = ssh->kex;
+
+ if (kex->verify_host_key == NULL) {
+ error_f("missing hostkey verifier");
+ return SSH_ERR_INVALID_ARGUMENT;
+ }
+ if (server_host_key->type != kex->hostkey_type ||
+ (kex->hostkey_type == KEY_ECDSA &&
+ server_host_key->ecdsa_nid != kex->hostkey_nid))
+ return SSH_ERR_KEY_TYPE_MISMATCH;
+ if (kex->verify_host_key(server_host_key, ssh) == -1)
+ return SSH_ERR_SIGNATURE_INVALID;
+ return 0;
+}
+
+#if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
+void
+dump_digest(const char *msg, const u_char *digest, int len)
+{
+ fprintf(stderr, "%s\n", msg);
+ sshbuf_dump_data(digest, len, stderr);
+}
+#endif
+
+/*
+ * Send a plaintext error message to the peer, suffixed by \r\n.
+ * Only used during banner exchange, and there only for the server.
+ */
+static void
+send_error(struct ssh *ssh, char *msg)
+{
+ char *crnl = "\r\n";
+
+ if (!ssh->kex->server)
+ return;
+
+ if (atomicio(vwrite, ssh_packet_get_connection_out(ssh),
+ msg, strlen(msg)) != strlen(msg) ||
+ atomicio(vwrite, ssh_packet_get_connection_out(ssh),
+ crnl, strlen(crnl)) != strlen(crnl))
+ error_f("write: %.100s", strerror(errno));
+}
+
+/*
+ * Sends our identification string and waits for the peer's. Will block for
+ * up to timeout_ms (or indefinitely if timeout_ms <= 0).
+ * Returns on 0 success or a ssherr.h code on failure.
+ */
+int
+kex_exchange_identification(struct ssh *ssh, int timeout_ms,
+ const char *version_addendum)
+{
+ int remote_major, remote_minor, mismatch, oerrno = 0;
+ size_t len, n;
+ int r, expect_nl;
+ u_char c;
+ struct sshbuf *our_version = ssh->kex->server ?
+ ssh->kex->server_version : ssh->kex->client_version;
+ struct sshbuf *peer_version = ssh->kex->server ?
+ ssh->kex->client_version : ssh->kex->server_version;
+ char *our_version_string = NULL, *peer_version_string = NULL;
+ char *cp, *remote_version = NULL;
+
+ /* Prepare and send our banner */
+ sshbuf_reset(our_version);
+ if (version_addendum != NULL && *version_addendum == '\0')
+ version_addendum = NULL;
+ if ((r = sshbuf_putf(our_version, "SSH-%d.%d-%.100s%s%s\r\n",
+ PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION,
+ version_addendum == NULL ? "" : " ",
+ version_addendum == NULL ? "" : version_addendum)) != 0) {
+ oerrno = errno;
+ error_fr(r, "sshbuf_putf");
+ goto out;
+ }
+
+ if (atomicio(vwrite, ssh_packet_get_connection_out(ssh),
+ sshbuf_mutable_ptr(our_version),
+ sshbuf_len(our_version)) != sshbuf_len(our_version)) {
+ oerrno = errno;
+ debug_f("write: %.100s", strerror(errno));
+ r = SSH_ERR_SYSTEM_ERROR;
+ goto out;
+ }
+ if ((r = sshbuf_consume_end(our_version, 2)) != 0) { /* trim \r\n */
+ oerrno = errno;
+ error_fr(r, "sshbuf_consume_end");
+ goto out;
+ }
+ our_version_string = sshbuf_dup_string(our_version);
+ if (our_version_string == NULL) {
+ error_f("sshbuf_dup_string failed");
+ r = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+ debug("Local version string %.100s", our_version_string);
+
+ /* Read other side's version identification. */
+ for (n = 0; ; n++) {
+ if (n >= SSH_MAX_PRE_BANNER_LINES) {
+ send_error(ssh, "No SSH identification string "
+ "received.");
+ error_f("No SSH version received in first %u lines "
+ "from server", SSH_MAX_PRE_BANNER_LINES);
+ r = SSH_ERR_INVALID_FORMAT;
+ goto out;
+ }
+ sshbuf_reset(peer_version);
+ expect_nl = 0;
+ for (;;) {
+ if (timeout_ms > 0) {
+ r = waitrfd(ssh_packet_get_connection_in(ssh),
+ &timeout_ms);
+ if (r == -1 && errno == ETIMEDOUT) {
+ send_error(ssh, "Timed out waiting "
+ "for SSH identification string.");
+ error("Connection timed out during "
+ "banner exchange");
+ r = SSH_ERR_CONN_TIMEOUT;
+ goto out;
+ } else if (r == -1) {
+ oerrno = errno;
+ error_f("%s", strerror(errno));
+ r = SSH_ERR_SYSTEM_ERROR;
+ goto out;
+ }
+ }
+
+ len = atomicio(read, ssh_packet_get_connection_in(ssh),
+ &c, 1);
+ if (len != 1 && errno == EPIPE) {
+ error_f("Connection closed by remote host");
+ r = SSH_ERR_CONN_CLOSED;
+ goto out;
+ } else if (len != 1) {
+ oerrno = errno;
+ error_f("read: %.100s", strerror(errno));
+ r = SSH_ERR_SYSTEM_ERROR;
+ goto out;
+ }
+ if (c == '\r') {
+ expect_nl = 1;
+ continue;
+ }
+ if (c == '\n')
+ break;
+ if (c == '\0' || expect_nl) {
+ error_f("banner line contains invalid "
+ "characters");
+ goto invalid;
+ }
+ if ((r = sshbuf_put_u8(peer_version, c)) != 0) {
+ oerrno = errno;
+ error_fr(r, "sshbuf_put");
+ goto out;
+ }
+ if (sshbuf_len(peer_version) > SSH_MAX_BANNER_LEN) {
+ error_f("banner line too long");
+ goto invalid;
+ }
+ }
+ /* Is this an actual protocol banner? */
+ if (sshbuf_len(peer_version) > 4 &&
+ memcmp(sshbuf_ptr(peer_version), "SSH-", 4) == 0)
+ break;
+ /* If not, then just log the line and continue */
+ if ((cp = sshbuf_dup_string(peer_version)) == NULL) {
+ error_f("sshbuf_dup_string failed");
+ r = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+ /* Do not accept lines before the SSH ident from a client */
+ if (ssh->kex->server) {
+ error_f("client sent invalid protocol identifier "
+ "\"%.256s\"", cp);
+ free(cp);
+ goto invalid;
+ }
+ debug_f("banner line %zu: %s", n, cp);
+ free(cp);
+ }
+ peer_version_string = sshbuf_dup_string(peer_version);
+ if (peer_version_string == NULL)
+ error_f("sshbuf_dup_string failed");
+ /* XXX must be same size for sscanf */
+ if ((remote_version = calloc(1, sshbuf_len(peer_version))) == NULL) {
+ error_f("calloc failed");
+ r = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+
+ /*
+ * Check that the versions match. In future this might accept
+ * several versions and set appropriate flags to handle them.
+ */
+ if (sscanf(peer_version_string, "SSH-%d.%d-%[^\n]\n",
+ &remote_major, &remote_minor, remote_version) != 3) {
+ error("Bad remote protocol version identification: '%.100s'",
+ peer_version_string);
+ invalid:
+ send_error(ssh, "Invalid SSH identification string.");
+ r = SSH_ERR_INVALID_FORMAT;
+ goto out;
+ }
+ debug("Remote protocol version %d.%d, remote software version %.100s",
+ remote_major, remote_minor, remote_version);
+ compat_banner(ssh, remote_version);
+
+ mismatch = 0;
+ switch (remote_major) {
+ case 2:
+ break;
+ case 1:
+ if (remote_minor != 99)
+ mismatch = 1;
+ break;
+ default:
+ mismatch = 1;
+ break;
+ }
+ if (mismatch) {
+ error("Protocol major versions differ: %d vs. %d",
+ PROTOCOL_MAJOR_2, remote_major);
+ send_error(ssh, "Protocol major versions differ.");
+ r = SSH_ERR_NO_PROTOCOL_VERSION;
+ goto out;
+ }
+
+ if (ssh->kex->server && (ssh->compat & SSH_BUG_PROBE) != 0) {
+ logit("probed from %s port %d with %s. Don't panic.",
+ ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
+ peer_version_string);
+ r = SSH_ERR_CONN_CLOSED; /* XXX */
+ goto out;
+ }
+ if (ssh->kex->server && (ssh->compat & SSH_BUG_SCANNER) != 0) {
+ logit("scanned from %s port %d with %s. Don't panic.",
+ ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
+ peer_version_string);
+ r = SSH_ERR_CONN_CLOSED; /* XXX */
+ goto out;
+ }
+ if ((ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
+ logit("Remote version \"%.100s\" uses unsafe RSA signature "
+ "scheme; disabling use of RSA keys", remote_version);
+ }
+ /* success */
+ r = 0;
+ out:
+ free(our_version_string);
+ free(peer_version_string);
+ free(remote_version);
+ if (r == SSH_ERR_SYSTEM_ERROR)
+ errno = oerrno;
+ return r;
+}
+