Annotation of src/usr.bin/ssh/kexgexc.c, Revision 1.19
1.19 ! markus 1: /* $OpenBSD: kexgexc.c,v 1.18 2015/01/19 19:52:16 markus Exp $ */
1.1 markus 2: /*
3: * Copyright (c) 2000 Niels Provos. All rights reserved.
4: * Copyright (c) 2001 Markus Friedl. All rights reserved.
5: *
6: * Redistribution and use in source and binary forms, with or without
7: * modification, are permitted provided that the following conditions
8: * are met:
9: * 1. Redistributions of source code must retain the above copyright
10: * notice, this list of conditions and the following disclaimer.
11: * 2. Redistributions in binary form must reproduce the above copyright
12: * notice, this list of conditions and the following disclaimer in the
13: * documentation and/or other materials provided with the distribution.
14: *
15: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25: */
26:
1.9 deraadt 27: #include <sys/types.h>
1.12 djm 28:
29: #include <openssl/dh.h>
1.7 stevesk 30:
1.8 stevesk 31: #include <stdio.h>
1.7 stevesk 32: #include <string.h>
1.9 deraadt 33: #include <signal.h>
1.1 markus 34:
1.19 ! markus 35: #include "sshkey.h"
1.9 deraadt 36: #include "cipher.h"
1.19 ! markus 37: #include "digest.h"
1.1 markus 38: #include "kex.h"
39: #include "log.h"
40: #include "packet.h"
41: #include "dh.h"
42: #include "ssh2.h"
43: #include "compat.h"
1.19 ! markus 44: #include "dispatch.h"
! 45: #include "ssherr.h"
! 46: #include "sshbuf.h"
1.1 markus 47:
1.19 ! markus 48: static int input_kex_dh_gex_group(int, u_int32_t, void *);
! 49: static int input_kex_dh_gex_reply(int, u_int32_t, void *);
! 50:
! 51: int
! 52: kexgex_client(struct ssh *ssh)
1.1 markus 53: {
1.19 ! markus 54: struct kex *kex = ssh->kex;
! 55: int r;
! 56: u_int nbits;
1.1 markus 57:
1.16 dtucker 58: nbits = dh_estimate(kex->dh_need * 8);
1.1 markus 59:
1.19 ! markus 60: kex->min = DH_GRP_MIN;
! 61: kex->max = DH_GRP_MAX;
! 62: kex->nbits = nbits;
! 63: if (ssh->compat & SSH_OLD_DHGEX) {
1.1 markus 64: /* Old GEX request */
1.19 ! markus 65: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST_OLD))
! 66: != 0 ||
! 67: (r = sshpkt_put_u32(ssh, kex->nbits)) != 0 ||
! 68: (r = sshpkt_send(ssh)) != 0)
! 69: goto out;
! 70: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", kex->nbits);
1.1 markus 71: } else {
72: /* New GEX request */
1.19 ! markus 73: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST)) != 0 ||
! 74: (r = sshpkt_put_u32(ssh, kex->min)) != 0 ||
! 75: (r = sshpkt_put_u32(ssh, kex->nbits)) != 0 ||
! 76: (r = sshpkt_put_u32(ssh, kex->max)) != 0 ||
! 77: (r = sshpkt_send(ssh)) != 0)
! 78: goto out;
1.2 markus 79: debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
1.19 ! markus 80: kex->min, kex->nbits, kex->max);
1.1 markus 81: }
82: #ifdef DEBUG_KEXDH
83: fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
1.19 ! markus 84: kex->min, kex->nbits, kex->max);
1.1 markus 85: #endif
1.19 ! markus 86: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP,
! 87: &input_kex_dh_gex_group);
! 88: r = 0;
! 89: out:
! 90: return r;
! 91: }
1.1 markus 92:
1.19 ! markus 93: static int
! 94: input_kex_dh_gex_group(int type, u_int32_t seq, void *ctxt)
! 95: {
! 96: struct ssh *ssh = ctxt;
! 97: struct kex *kex = ssh->kex;
! 98: BIGNUM *p = NULL, *g = NULL;
! 99: int r, bits;
1.1 markus 100:
1.19 ! markus 101: debug("got SSH2_MSG_KEX_DH_GEX_GROUP");
1.1 markus 102:
1.19 ! markus 103: if ((p = BN_new()) == NULL ||
! 104: (g = BN_new()) == NULL) {
! 105: r = SSH_ERR_ALLOC_FAIL;
! 106: goto out;
! 107: }
! 108: if ((r = sshpkt_get_bignum2(ssh, p)) != 0 ||
! 109: (r = sshpkt_get_bignum2(ssh, g)) != 0 ||
! 110: (r = sshpkt_get_end(ssh)) != 0)
! 111: goto out;
! 112: if ((bits = BN_num_bits(p)) < 0 ||
! 113: (u_int)bits < kex->min || (u_int)bits > kex->max) {
! 114: r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
! 115: goto out;
! 116: }
! 117: if ((kex->dh = dh_new_group(g, p)) == NULL) {
! 118: r = SSH_ERR_ALLOC_FAIL;
! 119: goto out;
! 120: }
! 121: p = g = NULL; /* belong to kex->dh now */
1.1 markus 122:
1.19 ! markus 123: /* generate and send 'e', client DH public key */
! 124: if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 ||
! 125: (r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_INIT)) != 0 ||
! 126: (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||
! 127: (r = sshpkt_send(ssh)) != 0)
! 128: goto out;
! 129: debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
1.1 markus 130: #ifdef DEBUG_KEXDH
1.19 ! markus 131: DHparams_print_fp(stderr, kex->dh);
1.1 markus 132: fprintf(stderr, "pub= ");
1.19 ! markus 133: BN_print_fp(stderr, kex->dh->pub_key);
1.1 markus 134: fprintf(stderr, "\n");
135: #endif
1.19 ! markus 136: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, NULL);
! 137: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REPLY, &input_kex_dh_gex_reply);
! 138: r = 0;
! 139: out:
! 140: if (p)
! 141: BN_clear_free(p);
! 142: if (g)
! 143: BN_clear_free(g);
! 144: return r;
! 145: }
1.1 markus 146:
1.19 ! markus 147: static int
! 148: input_kex_dh_gex_reply(int type, u_int32_t seq, void *ctxt)
! 149: {
! 150: struct ssh *ssh = ctxt;
! 151: struct kex *kex = ssh->kex;
! 152: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
! 153: struct sshkey *server_host_key = NULL;
! 154: u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
! 155: u_char hash[SSH_DIGEST_MAX_LENGTH];
! 156: size_t klen = 0, slen, sbloblen, hashlen;
! 157: int kout, r;
! 158:
! 159: debug("got SSH2_MSG_KEX_DH_GEX_REPLY");
! 160: if (kex->verify_host_key == NULL) {
! 161: r = SSH_ERR_INVALID_ARGUMENT;
! 162: goto out;
! 163: }
1.1 markus 164: /* key, cert */
1.19 ! markus 165: if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
! 166: &sbloblen)) != 0 ||
! 167: (r = sshkey_from_blob(server_host_key_blob, sbloblen,
! 168: &server_host_key)) != 0)
! 169: goto out;
! 170: if (server_host_key->type != kex->hostkey_type) {
! 171: r = SSH_ERR_KEY_TYPE_MISMATCH;
! 172: goto out;
! 173: }
! 174: if (kex->verify_host_key(server_host_key, ssh) == -1) {
! 175: r = SSH_ERR_SIGNATURE_INVALID;
! 176: goto out;
! 177: }
1.6 miod 178: /* DH parameter f, server public DH key */
1.19 ! markus 179: if ((dh_server_pub = BN_new()) == NULL) {
! 180: r = SSH_ERR_ALLOC_FAIL;
! 181: goto out;
! 182: }
! 183: /* signed H */
! 184: if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 ||
! 185: (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
! 186: (r = sshpkt_get_end(ssh)) != 0)
! 187: goto out;
1.1 markus 188: #ifdef DEBUG_KEXDH
189: fprintf(stderr, "dh_server_pub= ");
190: BN_print_fp(stderr, dh_server_pub);
191: fprintf(stderr, "\n");
192: debug("bits %d", BN_num_bits(dh_server_pub));
193: #endif
1.19 ! markus 194: if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
! 195: sshpkt_disconnect(ssh, "bad server public DH value");
! 196: r = SSH_ERR_MESSAGE_INCOMPLETE;
! 197: goto out;
! 198: }
1.1 markus 199:
1.19 ! markus 200: klen = DH_size(kex->dh);
! 201: if ((kbuf = malloc(klen)) == NULL ||
! 202: (shared_secret = BN_new()) == NULL) {
! 203: r = SSH_ERR_ALLOC_FAIL;
! 204: goto out;
! 205: }
! 206: if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
! 207: BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
! 208: r = SSH_ERR_LIBCRYPTO_ERROR;
! 209: goto out;
! 210: }
1.1 markus 211: #ifdef DEBUG_KEXDH
212: dump_digest("shared secret", kbuf, kout);
213: #endif
1.19 ! markus 214: if (ssh->compat & SSH_OLD_DHGEX)
! 215: kex->min = kex->max = -1;
1.1 markus 216:
217: /* calc and verify H */
1.19 ! markus 218: hashlen = sizeof(hash);
! 219: if ((r = kexgex_hash(
1.14 djm 220: kex->hash_alg,
1.1 markus 221: kex->client_version_string,
222: kex->server_version_string,
1.19 ! markus 223: sshbuf_ptr(kex->my), sshbuf_len(kex->my),
! 224: sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
1.1 markus 225: server_host_key_blob, sbloblen,
1.19 ! markus 226: kex->min, kex->nbits, kex->max,
! 227: kex->dh->p, kex->dh->g,
! 228: kex->dh->pub_key,
1.1 markus 229: dh_server_pub,
1.3 djm 230: shared_secret,
1.19 ! markus 231: hash, &hashlen)) != 0)
! 232: goto out;
1.3 djm 233:
1.19 ! markus 234: if ((r = sshkey_verify(server_host_key, signature, slen, hash,
! 235: hashlen, ssh->compat)) != 0)
! 236: goto out;
1.1 markus 237:
238: /* save session id */
239: if (kex->session_id == NULL) {
1.3 djm 240: kex->session_id_len = hashlen;
1.19 ! markus 241: kex->session_id = malloc(kex->session_id_len);
! 242: if (kex->session_id == NULL) {
! 243: r = SSH_ERR_ALLOC_FAIL;
! 244: goto out;
! 245: }
1.1 markus 246: memcpy(kex->session_id, hash, kex->session_id_len);
247: }
248:
1.19 ! markus 249: if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
! 250: r = kex_send_newkeys(ssh);
! 251: out:
! 252: explicit_bzero(hash, sizeof(hash));
! 253: DH_free(kex->dh);
! 254: kex->dh = NULL;
! 255: if (dh_server_pub)
! 256: BN_clear_free(dh_server_pub);
! 257: if (kbuf) {
! 258: explicit_bzero(kbuf, klen);
! 259: free(kbuf);
! 260: }
! 261: if (shared_secret)
! 262: BN_clear_free(shared_secret);
! 263: sshkey_free(server_host_key);
! 264: free(server_host_key_blob);
! 265: free(signature);
! 266: return r;
1.1 markus 267: }
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