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Diffstat (limited to '')
| -rw-r--r-- | kexgexc.c | 241 |
1 files changed, 241 insertions, 0 deletions
diff --git a/kexgexc.c b/kexgexc.c new file mode 100644 index 0000000..e99e0cf --- /dev/null +++ b/kexgexc.c @@ -0,0 +1,241 @@ +/* $OpenBSD: kexgexc.c,v 1.38 2021/12/19 22:08:06 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 (ssh->compat & 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 + debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP"); + 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("SSH2_MSG_KEX_DH_GEX_GROUP received"); + ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, &kex_protocol_error); + + 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 + debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY"); + 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("SSH2_MSG_KEX_DH_GEX_REPLY received"); + ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REPLY, &kex_protocol_error); + + /* 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)) != 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)); + 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 */ |