diff options
Diffstat (limited to 'kexgexc.c')
| -rw-r--r-- | kexgexc.c | 270 |
1 files changed, 270 insertions, 0 deletions
diff --git a/kexgexc.c b/kexgexc.c new file mode 100644 index 0000000..0d07f73 --- /dev/null +++ b/kexgexc.c @@ -0,0 +1,270 @@ +/* $OpenBSD: kexgexc.c,v 1.27 2018/02/07 02:06:51 jsing Exp $ */ +/* + * Copyright (c) 2000 Niels Provos. All rights reserved. + * Copyright (c) 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" + +#ifdef WITH_OPENSSL + +#include <sys/types.h> + +#include <openssl/dh.h> + +#include <stdarg.h> +#include <stdio.h> +#include <string.h> +#include <signal.h> + +#include "openbsd-compat/openssl-compat.h" + +#include "sshkey.h" +#include "cipher.h" +#include "digest.h" +#include "kex.h" +#include "log.h" +#include "packet.h" +#include "dh.h" +#include "ssh2.h" +#include "compat.h" +#include "dispatch.h" +#include "ssherr.h" +#include "sshbuf.h" +#include "misc.h" + +static int input_kex_dh_gex_group(int, u_int32_t, struct ssh *); +static int input_kex_dh_gex_reply(int, u_int32_t, struct ssh *); + +int +kexgex_client(struct ssh *ssh) +{ + struct kex *kex = ssh->kex; + int r; + u_int nbits; + + nbits = dh_estimate(kex->dh_need * 8); + + kex->min = DH_GRP_MIN; + kex->max = DH_GRP_MAX; + kex->nbits = nbits; + if (datafellows & SSH_BUG_DHGEX_LARGE) + kex->nbits = MINIMUM(kex->nbits, 4096); + /* New GEX request */ + if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST)) != 0 || + (r = sshpkt_put_u32(ssh, kex->min)) != 0 || + (r = sshpkt_put_u32(ssh, kex->nbits)) != 0 || + (r = sshpkt_put_u32(ssh, kex->max)) != 0 || + (r = sshpkt_send(ssh)) != 0) + goto out; + debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent", + kex->min, kex->nbits, kex->max); +#ifdef DEBUG_KEXDH + fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n", + kex->min, kex->nbits, kex->max); +#endif + ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, + &input_kex_dh_gex_group); + r = 0; + out: + return r; +} + +static int +input_kex_dh_gex_group(int type, u_int32_t seq, struct ssh *ssh) +{ + struct kex *kex = ssh->kex; + BIGNUM *p = NULL, *g = NULL; + const BIGNUM *pub_key; + int r, bits; + + debug("got SSH2_MSG_KEX_DH_GEX_GROUP"); + + if ((p = BN_new()) == NULL || + (g = BN_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + if ((r = sshpkt_get_bignum2(ssh, p)) != 0 || + (r = sshpkt_get_bignum2(ssh, g)) != 0 || + (r = sshpkt_get_end(ssh)) != 0) + goto out; + if ((bits = BN_num_bits(p)) < 0 || + (u_int)bits < kex->min || (u_int)bits > kex->max) { + r = SSH_ERR_DH_GEX_OUT_OF_RANGE; + goto out; + } + if ((kex->dh = dh_new_group(g, p)) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + p = g = NULL; /* belong to kex->dh now */ + + /* generate and send 'e', client DH public key */ + if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0) + goto out; + DH_get0_key(kex->dh, &pub_key, NULL); + if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_INIT)) != 0 || + (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 || + (r = sshpkt_send(ssh)) != 0) + goto out; + debug("SSH2_MSG_KEX_DH_GEX_INIT sent"); +#ifdef DEBUG_KEXDH + DHparams_print_fp(stderr, kex->dh); + fprintf(stderr, "pub= "); + BN_print_fp(stderr, pub_key); + fprintf(stderr, "\n"); +#endif + ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, NULL); + ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REPLY, &input_kex_dh_gex_reply); + r = 0; +out: + BN_clear_free(p); + BN_clear_free(g); + return r; +} + +static int +input_kex_dh_gex_reply(int type, u_int32_t seq, struct ssh *ssh) +{ + struct kex *kex = ssh->kex; + BIGNUM *dh_server_pub = NULL, *shared_secret = NULL; + const BIGNUM *pub_key, *dh_p, *dh_g; + struct sshkey *server_host_key = NULL; + u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL; + u_char hash[SSH_DIGEST_MAX_LENGTH]; + size_t klen = 0, slen, sbloblen, hashlen; + int kout, r; + + debug("got SSH2_MSG_KEX_DH_GEX_REPLY"); + if (kex->verify_host_key == NULL) { + r = SSH_ERR_INVALID_ARGUMENT; + goto out; + } + /* key, cert */ + if ((r = sshpkt_get_string(ssh, &server_host_key_blob, + &sbloblen)) != 0 || + (r = sshkey_from_blob(server_host_key_blob, sbloblen, + &server_host_key)) != 0) + goto out; + if (server_host_key->type != kex->hostkey_type || + (kex->hostkey_type == KEY_ECDSA && + server_host_key->ecdsa_nid != kex->hostkey_nid)) { + r = SSH_ERR_KEY_TYPE_MISMATCH; + goto out; + } + if (kex->verify_host_key(server_host_key, ssh) == -1) { + r = SSH_ERR_SIGNATURE_INVALID; + goto out; + } + /* DH parameter f, server public DH key */ + if ((dh_server_pub = BN_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + /* signed H */ + if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 || + (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 || + (r = sshpkt_get_end(ssh)) != 0) + goto out; +#ifdef DEBUG_KEXDH + fprintf(stderr, "dh_server_pub= "); + BN_print_fp(stderr, dh_server_pub); + fprintf(stderr, "\n"); + debug("bits %d", BN_num_bits(dh_server_pub)); +#endif + if (!dh_pub_is_valid(kex->dh, dh_server_pub)) { + sshpkt_disconnect(ssh, "bad server public DH value"); + r = SSH_ERR_MESSAGE_INCOMPLETE; + goto out; + } + + klen = DH_size(kex->dh); + if ((kbuf = malloc(klen)) == NULL || + (shared_secret = BN_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 || + BN_bin2bn(kbuf, kout, shared_secret) == NULL) { + r = SSH_ERR_LIBCRYPTO_ERROR; + goto out; + } +#ifdef DEBUG_KEXDH + dump_digest("shared secret", kbuf, kout); +#endif + if (ssh->compat & SSH_OLD_DHGEX) + kex->min = kex->max = -1; + + /* calc and verify H */ + DH_get0_key(kex->dh, &pub_key, NULL); + DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g); + hashlen = sizeof(hash); + if ((r = kexgex_hash( + kex->hash_alg, + kex->client_version_string, + kex->server_version_string, + sshbuf_ptr(kex->my), sshbuf_len(kex->my), + sshbuf_ptr(kex->peer), sshbuf_len(kex->peer), + server_host_key_blob, sbloblen, + kex->min, kex->nbits, kex->max, + dh_p, dh_g, + pub_key, + dh_server_pub, + shared_secret, + hash, &hashlen)) != 0) + goto out; + + if ((r = sshkey_verify(server_host_key, signature, slen, hash, + hashlen, kex->hostkey_alg, ssh->compat)) != 0) + goto out; + + /* save session id */ + if (kex->session_id == NULL) { + kex->session_id_len = hashlen; + kex->session_id = malloc(kex->session_id_len); + if (kex->session_id == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + memcpy(kex->session_id, hash, kex->session_id_len); + } + + if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0) + r = kex_send_newkeys(ssh); + out: + explicit_bzero(hash, sizeof(hash)); + DH_free(kex->dh); + kex->dh = NULL; + BN_clear_free(dh_server_pub); + if (kbuf) { + explicit_bzero(kbuf, klen); + free(kbuf); + } + BN_clear_free(shared_secret); + sshkey_free(server_host_key); + free(server_host_key_blob); + free(signature); + return r; +} +#endif /* WITH_OPENSSL */ |