diff options
Diffstat (limited to 'usr.bin/ssh/kexgexc.c')
| -rw-r--r-- | usr.bin/ssh/kexgexc.c | 189 |
1 files changed, 189 insertions, 0 deletions
diff --git a/usr.bin/ssh/kexgexc.c b/usr.bin/ssh/kexgexc.c new file mode 100644 index 00000000000..f14ac44ca04 --- /dev/null +++ b/usr.bin/ssh/kexgexc.c @@ -0,0 +1,189 @@ +/* + * 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" +RCSID("$OpenBSD: kexgexc.c,v 1.1 2003/02/16 17:09:57 markus Exp $"); + +#include "xmalloc.h" +#include "key.h" +#include "kex.h" +#include "log.h" +#include "packet.h" +#include "dh.h" +#include "ssh2.h" +#include "compat.h" + +void +kexgex_client(Kex *kex) +{ + BIGNUM *dh_server_pub = NULL, *shared_secret = NULL; + BIGNUM *p = NULL, *g = NULL; + Key *server_host_key; + u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; + u_int klen, kout, slen, sbloblen; + int min, max, nbits; + DH *dh; + + nbits = dh_estimate(kex->we_need * 8); + + if (datafellows & SSH_OLD_DHGEX) { + debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD sent"); + + /* Old GEX request */ + packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD); + packet_put_int(nbits); + min = DH_GRP_MIN; + max = DH_GRP_MAX; + } else { + debug("SSH2_MSG_KEX_DH_GEX_REQUEST sent"); + + /* New GEX request */ + min = DH_GRP_MIN; + max = DH_GRP_MAX; + packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST); + packet_put_int(min); + packet_put_int(nbits); + packet_put_int(max); + } +#ifdef DEBUG_KEXDH + fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n", + min, nbits, max); +#endif + packet_send(); + + debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP"); + packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP); + + if ((p = BN_new()) == NULL) + fatal("BN_new"); + packet_get_bignum2(p); + if ((g = BN_new()) == NULL) + fatal("BN_new"); + packet_get_bignum2(g); + packet_check_eom(); + + if (BN_num_bits(p) < min || BN_num_bits(p) > max) + fatal("DH_GEX group out of range: %d !< %d !< %d", + min, BN_num_bits(p), max); + + dh = dh_new_group(g, p); + dh_gen_key(dh, kex->we_need * 8); + +#ifdef DEBUG_KEXDH + DHparams_print_fp(stderr, dh); + fprintf(stderr, "pub= "); + BN_print_fp(stderr, dh->pub_key); + fprintf(stderr, "\n"); +#endif + + debug("SSH2_MSG_KEX_DH_GEX_INIT sent"); + /* generate and send 'e', client DH public key */ + packet_start(SSH2_MSG_KEX_DH_GEX_INIT); + packet_put_bignum2(dh->pub_key); + packet_send(); + + debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY"); + packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY); + + /* key, cert */ + server_host_key_blob = packet_get_string(&sbloblen); + server_host_key = key_from_blob(server_host_key_blob, sbloblen); + if (server_host_key == NULL) + fatal("cannot decode server_host_key_blob"); + if (server_host_key->type != kex->hostkey_type) + fatal("type mismatch for decoded server_host_key_blob"); + if (kex->verify_host_key == NULL) + fatal("cannot verify server_host_key"); + if (kex->verify_host_key(server_host_key) == -1) + fatal("server_host_key verification failed"); + + /* DH paramter f, server public DH key */ + if ((dh_server_pub = BN_new()) == NULL) + fatal("dh_server_pub == NULL"); + packet_get_bignum2(dh_server_pub); + +#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 + + /* signed H */ + signature = packet_get_string(&slen); + packet_check_eom(); + + if (!dh_pub_is_valid(dh, dh_server_pub)) + packet_disconnect("bad server public DH value"); + + klen = DH_size(dh); + kbuf = xmalloc(klen); + kout = DH_compute_key(kbuf, dh_server_pub, dh); +#ifdef DEBUG_KEXDH + dump_digest("shared secret", kbuf, kout); +#endif + if ((shared_secret = BN_new()) == NULL) + fatal("kexgex_client: BN_new failed"); + BN_bin2bn(kbuf, kout, shared_secret); + memset(kbuf, 0, klen); + xfree(kbuf); + + if (datafellows & SSH_OLD_DHGEX) + min = max = -1; + + /* calc and verify H */ + hash = kexgex_hash( + kex->client_version_string, + kex->server_version_string, + buffer_ptr(&kex->my), buffer_len(&kex->my), + buffer_ptr(&kex->peer), buffer_len(&kex->peer), + server_host_key_blob, sbloblen, + min, nbits, max, + dh->p, dh->g, + dh->pub_key, + dh_server_pub, + shared_secret + ); + /* have keys, free DH */ + DH_free(dh); + xfree(server_host_key_blob); + BN_clear_free(dh_server_pub); + + if (key_verify(server_host_key, signature, slen, hash, 20) != 1) + fatal("key_verify failed for server_host_key"); + key_free(server_host_key); + xfree(signature); + + /* save session id */ + if (kex->session_id == NULL) { + kex->session_id_len = 20; + kex->session_id = xmalloc(kex->session_id_len); + memcpy(kex->session_id, hash, kex->session_id_len); + } + kex_derive_keys(kex, hash, shared_secret); + BN_clear_free(shared_secret); + + kex_finish(kex); +} |