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-rw-r--r--kexgen.c371
1 files changed, 371 insertions, 0 deletions
diff --git a/kexgen.c b/kexgen.c
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+++ b/kexgen.c
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+/* $OpenBSD: kexgen.c,v 1.8 2021/12/19 22:08:06 djm Exp $ */
+/*
+ * Copyright (c) 2019 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 <stdarg.h>
+#include <stdio.h>
+#include <string.h>
+#include <signal.h>
+
+#include "sshkey.h"
+#include "kex.h"
+#include "log.h"
+#include "packet.h"
+#include "ssh2.h"
+#include "sshbuf.h"
+#include "digest.h"
+#include "ssherr.h"
+
+static int input_kex_gen_init(int, u_int32_t, struct ssh *);
+static int input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh);
+
+static int
+kex_gen_hash(
+ int hash_alg,
+ const struct sshbuf *client_version,
+ const struct sshbuf *server_version,
+ const struct sshbuf *client_kexinit,
+ const struct sshbuf *server_kexinit,
+ const struct sshbuf *server_host_key_blob,
+ const struct sshbuf *client_pub,
+ const struct sshbuf *server_pub,
+ const struct sshbuf *shared_secret,
+ u_char *hash, size_t *hashlen)
+{
+ struct sshbuf *b;
+ int r;
+
+ if (*hashlen < ssh_digest_bytes(hash_alg))
+ return SSH_ERR_INVALID_ARGUMENT;
+ if ((b = sshbuf_new()) == NULL)
+ return SSH_ERR_ALLOC_FAIL;
+ if ((r = sshbuf_put_stringb(b, client_version)) != 0 ||
+ (r = sshbuf_put_stringb(b, server_version)) != 0 ||
+ /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
+ (r = sshbuf_put_u32(b, sshbuf_len(client_kexinit) + 1)) != 0 ||
+ (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
+ (r = sshbuf_putb(b, client_kexinit)) != 0 ||
+ (r = sshbuf_put_u32(b, sshbuf_len(server_kexinit) + 1)) != 0 ||
+ (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
+ (r = sshbuf_putb(b, server_kexinit)) != 0 ||
+ (r = sshbuf_put_stringb(b, server_host_key_blob)) != 0 ||
+ (r = sshbuf_put_stringb(b, client_pub)) != 0 ||
+ (r = sshbuf_put_stringb(b, server_pub)) != 0 ||
+ (r = sshbuf_putb(b, shared_secret)) != 0) {
+ sshbuf_free(b);
+ return r;
+ }
+#ifdef DEBUG_KEX
+ sshbuf_dump(b, stderr);
+#endif
+ if (ssh_digest_buffer(hash_alg, b, hash, *hashlen) != 0) {
+ sshbuf_free(b);
+ return SSH_ERR_LIBCRYPTO_ERROR;
+ }
+ sshbuf_free(b);
+ *hashlen = ssh_digest_bytes(hash_alg);
+#ifdef DEBUG_KEX
+ dump_digest("hash", hash, *hashlen);
+#endif
+ return 0;
+}
+
+int
+kex_gen_client(struct ssh *ssh)
+{
+ struct kex *kex = ssh->kex;
+ int r;
+
+ switch (kex->kex_type) {
+#ifdef WITH_OPENSSL
+ case KEX_DH_GRP1_SHA1:
+ case KEX_DH_GRP14_SHA1:
+ case KEX_DH_GRP14_SHA256:
+ case KEX_DH_GRP16_SHA512:
+ case KEX_DH_GRP18_SHA512:
+ r = kex_dh_keypair(kex);
+ break;
+ case KEX_ECDH_SHA2:
+ r = kex_ecdh_keypair(kex);
+ break;
+#endif
+ case KEX_C25519_SHA256:
+ r = kex_c25519_keypair(kex);
+ break;
+ case KEX_KEM_SNTRUP761X25519_SHA512:
+ r = kex_kem_sntrup761x25519_keypair(kex);
+ break;
+ default:
+ r = SSH_ERR_INVALID_ARGUMENT;
+ break;
+ }
+ if (r != 0)
+ return r;
+ if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 ||
+ (r = sshpkt_put_stringb(ssh, kex->client_pub)) != 0 ||
+ (r = sshpkt_send(ssh)) != 0)
+ return r;
+ debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
+ ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_gen_reply);
+ return 0;
+}
+
+static int
+input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh)
+{
+ struct kex *kex = ssh->kex;
+ struct sshkey *server_host_key = NULL;
+ struct sshbuf *shared_secret = NULL;
+ struct sshbuf *server_blob = NULL;
+ struct sshbuf *tmp = NULL, *server_host_key_blob = NULL;
+ u_char *signature = NULL;
+ u_char hash[SSH_DIGEST_MAX_LENGTH];
+ size_t slen, hashlen;
+ int r;
+
+ debug("SSH2_MSG_KEX_ECDH_REPLY received");
+ ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &kex_protocol_error);
+
+ /* hostkey */
+ if ((r = sshpkt_getb_froms(ssh, &server_host_key_blob)) != 0)
+ goto out;
+ /* sshkey_fromb() consumes its buffer, so make a copy */
+ if ((tmp = sshbuf_fromb(server_host_key_blob)) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+ if ((r = sshkey_fromb(tmp, &server_host_key)) != 0)
+ goto out;
+ if ((r = kex_verify_host_key(ssh, server_host_key)) != 0)
+ goto out;
+
+ /* Q_S, server public key */
+ /* signed H */
+ if ((r = sshpkt_getb_froms(ssh, &server_blob)) != 0 ||
+ (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
+ (r = sshpkt_get_end(ssh)) != 0)
+ goto out;
+
+ /* compute shared secret */
+ switch (kex->kex_type) {
+#ifdef WITH_OPENSSL
+ case KEX_DH_GRP1_SHA1:
+ case KEX_DH_GRP14_SHA1:
+ case KEX_DH_GRP14_SHA256:
+ case KEX_DH_GRP16_SHA512:
+ case KEX_DH_GRP18_SHA512:
+ r = kex_dh_dec(kex, server_blob, &shared_secret);
+ break;
+ case KEX_ECDH_SHA2:
+ r = kex_ecdh_dec(kex, server_blob, &shared_secret);
+ break;
+#endif
+ case KEX_C25519_SHA256:
+ r = kex_c25519_dec(kex, server_blob, &shared_secret);
+ break;
+ case KEX_KEM_SNTRUP761X25519_SHA512:
+ r = kex_kem_sntrup761x25519_dec(kex, server_blob,
+ &shared_secret);
+ break;
+ default:
+ r = SSH_ERR_INVALID_ARGUMENT;
+ break;
+ }
+ if (r !=0 )
+ goto out;
+
+ /* calc and verify H */
+ hashlen = sizeof(hash);
+ if ((r = kex_gen_hash(
+ kex->hash_alg,
+ kex->client_version,
+ kex->server_version,
+ kex->my,
+ kex->peer,
+ server_host_key_blob,
+ kex->client_pub,
+ server_blob,
+ shared_secret,
+ hash, &hashlen)) != 0)
+ goto out;
+
+ if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
+ kex->hostkey_alg, ssh->compat, NULL)) != 0)
+ goto out;
+
+ if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) != 0 ||
+ (r = kex_send_newkeys(ssh)) != 0)
+ goto out;
+
+ /* save initial signature and hostkey */
+ if ((kex->flags & KEX_INITIAL) != 0) {
+ if (kex->initial_hostkey != NULL || kex->initial_sig != NULL) {
+ r = SSH_ERR_INTERNAL_ERROR;
+ goto out;
+ }
+ if ((kex->initial_sig = sshbuf_new()) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+ if ((r = sshbuf_put(kex->initial_sig, signature, slen)) != 0)
+ goto out;
+ kex->initial_hostkey = server_host_key;
+ server_host_key = NULL;
+ }
+ /* success */
+out:
+ explicit_bzero(hash, sizeof(hash));
+ explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key));
+ explicit_bzero(kex->sntrup761_client_key,
+ sizeof(kex->sntrup761_client_key));
+ sshbuf_free(server_host_key_blob);
+ free(signature);
+ sshbuf_free(tmp);
+ sshkey_free(server_host_key);
+ sshbuf_free(server_blob);
+ sshbuf_free(shared_secret);
+ sshbuf_free(kex->client_pub);
+ kex->client_pub = NULL;
+ return r;
+}
+
+int
+kex_gen_server(struct ssh *ssh)
+{
+ debug("expecting SSH2_MSG_KEX_ECDH_INIT");
+ ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_gen_init);
+ return 0;
+}
+
+static int
+input_kex_gen_init(int type, u_int32_t seq, struct ssh *ssh)
+{
+ struct kex *kex = ssh->kex;
+ struct sshkey *server_host_private, *server_host_public;
+ struct sshbuf *shared_secret = NULL;
+ struct sshbuf *server_pubkey = NULL;
+ struct sshbuf *client_pubkey = NULL;
+ struct sshbuf *server_host_key_blob = NULL;
+ u_char *signature = NULL, hash[SSH_DIGEST_MAX_LENGTH];
+ size_t slen, hashlen;
+ int r;
+
+ debug("SSH2_MSG_KEX_ECDH_INIT received");
+ ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &kex_protocol_error);
+
+ if ((r = kex_load_hostkey(ssh, &server_host_private,
+ &server_host_public)) != 0)
+ goto out;
+
+ if ((r = sshpkt_getb_froms(ssh, &client_pubkey)) != 0 ||
+ (r = sshpkt_get_end(ssh)) != 0)
+ goto out;
+
+ /* compute shared secret */
+ switch (kex->kex_type) {
+#ifdef WITH_OPENSSL
+ case KEX_DH_GRP1_SHA1:
+ case KEX_DH_GRP14_SHA1:
+ case KEX_DH_GRP14_SHA256:
+ case KEX_DH_GRP16_SHA512:
+ case KEX_DH_GRP18_SHA512:
+ r = kex_dh_enc(kex, client_pubkey, &server_pubkey,
+ &shared_secret);
+ break;
+ case KEX_ECDH_SHA2:
+ r = kex_ecdh_enc(kex, client_pubkey, &server_pubkey,
+ &shared_secret);
+ break;
+#endif
+ case KEX_C25519_SHA256:
+ r = kex_c25519_enc(kex, client_pubkey, &server_pubkey,
+ &shared_secret);
+ break;
+ case KEX_KEM_SNTRUP761X25519_SHA512:
+ r = kex_kem_sntrup761x25519_enc(kex, client_pubkey,
+ &server_pubkey, &shared_secret);
+ break;
+ default:
+ r = SSH_ERR_INVALID_ARGUMENT;
+ break;
+ }
+ if (r !=0 )
+ goto out;
+
+ /* calc H */
+ if ((server_host_key_blob = sshbuf_new()) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+ if ((r = sshkey_putb(server_host_public, server_host_key_blob)) != 0)
+ goto out;
+ hashlen = sizeof(hash);
+ if ((r = kex_gen_hash(
+ kex->hash_alg,
+ kex->client_version,
+ kex->server_version,
+ kex->peer,
+ kex->my,
+ server_host_key_blob,
+ client_pubkey,
+ server_pubkey,
+ shared_secret,
+ hash, &hashlen)) != 0)
+ goto out;
+
+ /* sign H */
+ if ((r = kex->sign(ssh, server_host_private, server_host_public,
+ &signature, &slen, hash, hashlen, kex->hostkey_alg)) != 0)
+ goto out;
+
+ /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
+ if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
+ (r = sshpkt_put_stringb(ssh, server_host_key_blob)) != 0 ||
+ (r = sshpkt_put_stringb(ssh, server_pubkey)) != 0 ||
+ (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
+ (r = sshpkt_send(ssh)) != 0)
+ goto out;
+
+ if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) != 0 ||
+ (r = kex_send_newkeys(ssh)) != 0)
+ goto out;
+ /* retain copy of hostkey used at initial KEX */
+ if (kex->initial_hostkey == NULL &&
+ (r = sshkey_from_private(server_host_public,
+ &kex->initial_hostkey)) != 0)
+ goto out;
+ /* success */
+out:
+ explicit_bzero(hash, sizeof(hash));
+ sshbuf_free(server_host_key_blob);
+ free(signature);
+ sshbuf_free(shared_secret);
+ sshbuf_free(client_pubkey);
+ sshbuf_free(server_pubkey);
+ return r;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-04 01:16:23 +0000