Annotation of src/usr.bin/ssh/kexgexs.c, Revision 1.31
1.31 ! markus 1: /* $OpenBSD: kexgexs.c,v 1.30 2016/09/12 01:22:38 deraadt 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;
1.1 markus 70:
1.25 djm 71: debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
72: if ((r = sshpkt_get_u32(ssh, &min)) != 0 ||
73: (r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
74: (r = sshpkt_get_u32(ssh, &max)) != 0 ||
75: (r = sshpkt_get_end(ssh)) != 0)
1.21 markus 76: goto out;
1.25 djm 77: kex->nbits = nbits;
78: kex->min = min;
79: kex->max = max;
1.30 deraadt 80: min = MAXIMUM(DH_GRP_MIN, min);
81: max = MINIMUM(DH_GRP_MAX, max);
82: nbits = MAXIMUM(DH_GRP_MIN, nbits);
83: nbits = MINIMUM(DH_GRP_MAX, nbits);
1.29 dtucker 84:
1.21 markus 85: if (kex->max < kex->min || kex->nbits < kex->min ||
1.29 dtucker 86: kex->max < kex->nbits || kex->max < DH_GRP_MIN) {
1.21 markus 87: r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
88: goto out;
89: }
1.1 markus 90:
91: /* Contact privileged parent */
1.29 dtucker 92: kex->dh = PRIVSEP(choose_dh(min, nbits, max));
1.21 markus 93: if (kex->dh == NULL) {
1.29 dtucker 94: sshpkt_disconnect(ssh, "no matching DH grp found");
1.21 markus 95: r = SSH_ERR_ALLOC_FAIL;
96: goto out;
97: }
1.1 markus 98: debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
1.21 markus 99: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 ||
100: (r = sshpkt_put_bignum2(ssh, kex->dh->p)) != 0 ||
101: (r = sshpkt_put_bignum2(ssh, kex->dh->g)) != 0 ||
102: (r = sshpkt_send(ssh)) != 0)
103: goto out;
1.1 markus 104:
1.21 markus 105: /* Compute our exchange value in parallel with the client */
106: if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
107: goto out;
1.1 markus 108:
109: debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
1.21 markus 110: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init);
111: r = 0;
112: out:
113: return r;
114: }
115:
116: static int
1.31 ! markus 117: input_kex_dh_gex_init(int type, u_int32_t seq, struct ssh *ssh)
1.21 markus 118: {
119: struct kex *kex = ssh->kex;
120: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
121: struct sshkey *server_host_public, *server_host_private;
122: u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
123: u_char hash[SSH_DIGEST_MAX_LENGTH];
124: size_t sbloblen, slen;
125: size_t klen = 0, hashlen;
126: int kout, r;
127:
128: if (kex->load_host_public_key == NULL ||
129: kex->load_host_private_key == NULL) {
130: r = SSH_ERR_INVALID_ARGUMENT;
131: goto out;
132: }
1.24 djm 133: server_host_public = kex->load_host_public_key(kex->hostkey_type,
134: kex->hostkey_nid, ssh);
135: server_host_private = kex->load_host_private_key(kex->hostkey_type,
136: kex->hostkey_nid, ssh);
1.22 djm 137: if (server_host_public == NULL) {
1.21 markus 138: r = SSH_ERR_NO_HOSTKEY_LOADED;
139: goto out;
140: }
1.1 markus 141:
142: /* key, cert */
1.21 markus 143: if ((dh_client_pub = BN_new()) == NULL) {
144: r = SSH_ERR_ALLOC_FAIL;
145: goto out;
146: }
147: if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 ||
148: (r = sshpkt_get_end(ssh)) != 0)
149: goto out;
1.1 markus 150:
151: #ifdef DEBUG_KEXDH
152: fprintf(stderr, "dh_client_pub= ");
153: BN_print_fp(stderr, dh_client_pub);
154: fprintf(stderr, "\n");
155: debug("bits %d", BN_num_bits(dh_client_pub));
156: #endif
157:
158: #ifdef DEBUG_KEXDH
1.21 markus 159: DHparams_print_fp(stderr, kex->dh);
1.1 markus 160: fprintf(stderr, "pub= ");
1.21 markus 161: BN_print_fp(stderr, kex->dh->pub_key);
1.1 markus 162: fprintf(stderr, "\n");
163: #endif
1.21 markus 164: if (!dh_pub_is_valid(kex->dh, dh_client_pub)) {
165: sshpkt_disconnect(ssh, "bad client public DH value");
166: r = SSH_ERR_MESSAGE_INCOMPLETE;
167: goto out;
168: }
1.1 markus 169:
1.21 markus 170: klen = DH_size(kex->dh);
171: if ((kbuf = malloc(klen)) == NULL ||
172: (shared_secret = BN_new()) == NULL) {
173: r = SSH_ERR_ALLOC_FAIL;
174: goto out;
175: }
176: if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 ||
177: BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
178: r = SSH_ERR_LIBCRYPTO_ERROR;
179: goto out;
180: }
1.1 markus 181: #ifdef DEBUG_KEXDH
182: dump_digest("shared secret", kbuf, kout);
183: #endif
1.21 markus 184: if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
185: &sbloblen)) != 0)
186: goto out;
1.2 djm 187: /* calc H */
1.21 markus 188: hashlen = sizeof(hash);
189: if ((r = kexgex_hash(
1.17 djm 190: kex->hash_alg,
1.1 markus 191: kex->client_version_string,
192: kex->server_version_string,
1.21 markus 193: sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
194: sshbuf_ptr(kex->my), sshbuf_len(kex->my),
1.1 markus 195: server_host_key_blob, sbloblen,
1.21 markus 196: kex->min, kex->nbits, kex->max,
197: kex->dh->p, kex->dh->g,
1.1 markus 198: dh_client_pub,
1.21 markus 199: kex->dh->pub_key,
1.2 djm 200: shared_secret,
1.21 markus 201: hash, &hashlen)) != 0)
202: goto out;
1.1 markus 203:
204: /* save session id := H */
205: if (kex->session_id == NULL) {
1.2 djm 206: kex->session_id_len = hashlen;
1.21 markus 207: kex->session_id = malloc(kex->session_id_len);
208: if (kex->session_id == NULL) {
209: r = SSH_ERR_ALLOC_FAIL;
210: goto out;
211: }
1.1 markus 212: memcpy(kex->session_id, hash, kex->session_id_len);
213: }
214:
215: /* sign H */
1.26 markus 216: if ((r = kex->sign(server_host_private, server_host_public, &signature,
217: &slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0)
1.21 markus 218: goto out;
1.1 markus 219:
220: /* destroy_sensitive_data(); */
221:
222: /* send server hostkey, DH pubkey 'f' and singed H */
1.21 markus 223: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REPLY)) != 0 ||
224: (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
225: (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 || /* f */
226: (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
227: (r = sshpkt_send(ssh)) != 0)
228: goto out;
229:
230: if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
231: r = kex_send_newkeys(ssh);
232: out:
233: DH_free(kex->dh);
234: kex->dh = NULL;
235: if (dh_client_pub)
236: BN_clear_free(dh_client_pub);
237: if (kbuf) {
238: explicit_bzero(kbuf, klen);
239: free(kbuf);
240: }
241: if (shared_secret)
242: BN_clear_free(shared_secret);
243: free(server_host_key_blob);
1.15 djm 244: free(signature);
1.21 markus 245: return r;
1.1 markus 246: }
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