| /* $OpenBSD: kexgexc.c,v 1.35 2019/11/25 00:51:37 djm 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 ((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; |
| const BIGNUM *pub_key, *dh_p, *dh_g; |
| struct sshbuf *shared_secret = NULL; |
| struct sshbuf *tmp = NULL, *server_host_key_blob = NULL; |
| struct sshkey *server_host_key = NULL; |
| u_char *signature = NULL; |
| u_char hash[SSH_DIGEST_MAX_LENGTH]; |
| size_t slen, hashlen; |
| int r; |
| |
| debug("got SSH2_MSG_KEX_DH_GEX_REPLY"); |
| /* key, cert */ |
| 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 || |
| (r = kex_verify_host_key(ssh, server_host_key)) != 0) |
| goto out; |
| /* DH parameter f, server public DH key, 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; |
| if ((shared_secret = sshbuf_new()) == NULL) { |
| r = SSH_ERR_ALLOC_FAIL; |
| goto out; |
| } |
| if ((r = kex_dh_compute_key(kex, dh_server_pub, shared_secret)) != 0) |
| goto out; |
| 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, |
| kex->server_version, |
| kex->my, |
| kex->peer, |
| server_host_key_blob, |
| kex->min, kex->nbits, kex->max, |
| dh_p, dh_g, |
| pub_key, |
| dh_server_pub, |
| sshbuf_ptr(shared_secret), sshbuf_len(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); |
| out: |
| explicit_bzero(hash, sizeof(hash)); |
| DH_free(kex->dh); |
| kex->dh = NULL; |
| BN_clear_free(dh_server_pub); |
| sshbuf_free(shared_secret); |
| sshkey_free(server_host_key); |
| sshbuf_free(tmp); |
| sshbuf_free(server_host_key_blob); |
| free(signature); |
| return r; |
| } |
| #endif /* WITH_OPENSSL */ |