Annotation of src/usr.bin/ssh/kexgexs.c, Revision 1.39
1.39 ! djm 1: /* $OpenBSD: kexgexs.c,v 1.38 2019/01/21 09:54:11 djm 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:
1.5 stevesk 27:
1.7 stevesk 28: #include <stdio.h>
1.5 stevesk 29: #include <string.h>
1.8 deraadt 30: #include <signal.h>
1.14 djm 31:
32: #include <openssl/dh.h>
1.1 markus 33:
1.21 markus 34: #include "sshkey.h"
1.8 deraadt 35: #include "cipher.h"
1.21 markus 36: #include "digest.h"
1.1 markus 37: #include "kex.h"
38: #include "log.h"
39: #include "packet.h"
40: #include "dh.h"
41: #include "ssh2.h"
42: #include "compat.h"
1.8 deraadt 43: #ifdef GSSAPI
44: #include "ssh-gss.h"
45: #endif
1.1 markus 46: #include "monitor_wrap.h"
1.21 markus 47: #include "dispatch.h"
48: #include "ssherr.h"
49: #include "sshbuf.h"
1.30 deraadt 50: #include "misc.h"
1.1 markus 51:
1.31 markus 52: static int input_kex_dh_gex_request(int, u_int32_t, struct ssh *);
53: static int input_kex_dh_gex_init(int, u_int32_t, struct ssh *);
1.21 markus 54:
55: int
56: kexgex_server(struct ssh *ssh)
1.1 markus 57: {
1.21 markus 58: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST,
59: &input_kex_dh_gex_request);
60: debug("expecting SSH2_MSG_KEX_DH_GEX_REQUEST");
61: return 0;
62: }
1.1 markus 63:
1.21 markus 64: static int
1.31 markus 65: input_kex_dh_gex_request(int type, u_int32_t seq, struct ssh *ssh)
1.21 markus 66: {
67: struct kex *kex = ssh->kex;
68: int r;
69: u_int min = 0, max = 0, nbits = 0;
1.34 djm 70: const BIGNUM *dh_p, *dh_g;
1.1 markus 71:
1.25 djm 72: debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
73: if ((r = sshpkt_get_u32(ssh, &min)) != 0 ||
74: (r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
75: (r = sshpkt_get_u32(ssh, &max)) != 0 ||
76: (r = sshpkt_get_end(ssh)) != 0)
1.21 markus 77: goto out;
1.25 djm 78: kex->nbits = nbits;
79: kex->min = min;
80: kex->max = max;
1.30 deraadt 81: min = MAXIMUM(DH_GRP_MIN, min);
82: max = MINIMUM(DH_GRP_MAX, max);
83: nbits = MAXIMUM(DH_GRP_MIN, nbits);
84: nbits = MINIMUM(DH_GRP_MAX, nbits);
1.29 dtucker 85:
1.21 markus 86: if (kex->max < kex->min || kex->nbits < kex->min ||
1.29 dtucker 87: kex->max < kex->nbits || kex->max < DH_GRP_MIN) {
1.21 markus 88: r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
89: goto out;
90: }
1.1 markus 91:
92: /* Contact privileged parent */
1.29 dtucker 93: kex->dh = PRIVSEP(choose_dh(min, nbits, max));
1.21 markus 94: if (kex->dh == NULL) {
1.29 dtucker 95: sshpkt_disconnect(ssh, "no matching DH grp found");
1.21 markus 96: r = SSH_ERR_ALLOC_FAIL;
97: goto out;
98: }
1.1 markus 99: debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
1.34 djm 100: DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
1.21 markus 101: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 ||
1.34 djm 102: (r = sshpkt_put_bignum2(ssh, dh_p)) != 0 ||
103: (r = sshpkt_put_bignum2(ssh, dh_g)) != 0 ||
1.21 markus 104: (r = sshpkt_send(ssh)) != 0)
105: goto out;
1.1 markus 106:
1.21 markus 107: /* Compute our exchange value in parallel with the client */
108: if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
109: goto out;
1.1 markus 110:
111: debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
1.21 markus 112: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init);
113: r = 0;
114: out:
115: return r;
116: }
117:
118: static int
1.31 markus 119: input_kex_dh_gex_init(int type, u_int32_t seq, struct ssh *ssh)
1.21 markus 120: {
121: struct kex *kex = ssh->kex;
122: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
1.34 djm 123: const BIGNUM *pub_key, *dh_p, *dh_g;
1.21 markus 124: struct sshkey *server_host_public, *server_host_private;
125: u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
126: u_char hash[SSH_DIGEST_MAX_LENGTH];
127: size_t sbloblen, slen;
128: size_t klen = 0, hashlen;
129: int kout, r;
130:
131: if (kex->load_host_public_key == NULL ||
132: kex->load_host_private_key == NULL) {
133: r = SSH_ERR_INVALID_ARGUMENT;
134: goto out;
135: }
1.24 djm 136: server_host_public = kex->load_host_public_key(kex->hostkey_type,
137: kex->hostkey_nid, ssh);
138: server_host_private = kex->load_host_private_key(kex->hostkey_type,
139: kex->hostkey_nid, ssh);
1.22 djm 140: if (server_host_public == NULL) {
1.21 markus 141: r = SSH_ERR_NO_HOSTKEY_LOADED;
142: goto out;
143: }
1.1 markus 144:
145: /* key, cert */
1.38 djm 146: if ((r = sshpkt_get_bignum2(ssh, &dh_client_pub)) != 0 ||
1.21 markus 147: (r = sshpkt_get_end(ssh)) != 0)
148: goto out;
1.1 markus 149:
1.34 djm 150: DH_get0_key(kex->dh, &pub_key, NULL);
151: DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
152:
1.1 markus 153: #ifdef DEBUG_KEXDH
154: fprintf(stderr, "dh_client_pub= ");
155: BN_print_fp(stderr, dh_client_pub);
156: fprintf(stderr, "\n");
157: debug("bits %d", BN_num_bits(dh_client_pub));
1.21 markus 158: DHparams_print_fp(stderr, kex->dh);
1.1 markus 159: fprintf(stderr, "pub= ");
1.34 djm 160: BN_print_fp(stderr, pub_key);
1.1 markus 161: fprintf(stderr, "\n");
162: #endif
1.21 markus 163: if (!dh_pub_is_valid(kex->dh, dh_client_pub)) {
164: sshpkt_disconnect(ssh, "bad client public DH value");
165: r = SSH_ERR_MESSAGE_INCOMPLETE;
166: goto out;
167: }
1.1 markus 168:
1.21 markus 169: klen = DH_size(kex->dh);
170: if ((kbuf = malloc(klen)) == NULL ||
171: (shared_secret = BN_new()) == NULL) {
172: r = SSH_ERR_ALLOC_FAIL;
173: goto out;
174: }
175: if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 ||
176: BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
177: r = SSH_ERR_LIBCRYPTO_ERROR;
178: goto out;
179: }
1.1 markus 180: #ifdef DEBUG_KEXDH
181: dump_digest("shared secret", kbuf, kout);
182: #endif
1.21 markus 183: if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
184: &sbloblen)) != 0)
185: goto out;
1.2 djm 186: /* calc H */
1.21 markus 187: hashlen = sizeof(hash);
188: if ((r = kexgex_hash(
1.17 djm 189: kex->hash_alg,
1.36 djm 190: kex->client_version,
191: kex->server_version,
1.21 markus 192: sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
193: sshbuf_ptr(kex->my), sshbuf_len(kex->my),
1.1 markus 194: server_host_key_blob, sbloblen,
1.21 markus 195: kex->min, kex->nbits, kex->max,
1.34 djm 196: dh_p, dh_g,
1.1 markus 197: dh_client_pub,
1.34 djm 198: pub_key,
1.2 djm 199: shared_secret,
1.21 markus 200: hash, &hashlen)) != 0)
201: goto out;
1.1 markus 202:
203: /* sign H */
1.37 djm 204: if ((r = kex->sign(ssh, server_host_private, server_host_public,
205: &signature, &slen, hash, hashlen, kex->hostkey_alg)) < 0)
1.21 markus 206: goto out;
1.1 markus 207:
208: /* destroy_sensitive_data(); */
209:
1.33 djm 210: /* send server hostkey, DH pubkey 'f' and signed H */
1.21 markus 211: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REPLY)) != 0 ||
212: (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
1.34 djm 213: (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 || /* f */
1.21 markus 214: (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
215: (r = sshpkt_send(ssh)) != 0)
216: goto out;
217:
218: if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
219: r = kex_send_newkeys(ssh);
220: out:
1.35 djm 221: explicit_bzero(hash, sizeof(hash));
1.21 markus 222: DH_free(kex->dh);
223: kex->dh = NULL;
1.32 jsing 224: BN_clear_free(dh_client_pub);
1.21 markus 225: if (kbuf) {
226: explicit_bzero(kbuf, klen);
227: free(kbuf);
228: }
1.32 jsing 229: BN_clear_free(shared_secret);
1.21 markus 230: free(server_host_key_blob);
1.15 djm 231: free(signature);
1.21 markus 232: return r;
1.1 markus 233: }
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