Annotation of src/usr.bin/ssh/kexgexc.c, Revision 1.18
1.18 ! markus 1: /* $OpenBSD: kexgexc.c,v 1.17 2014/02/02 03:44:31 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:
1.9 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:
35: #include "xmalloc.h"
1.9 deraadt 36: #include "buffer.h"
1.1 markus 37: #include "key.h"
1.9 deraadt 38: #include "cipher.h"
1.1 markus 39: #include "kex.h"
40: #include "log.h"
41: #include "packet.h"
42: #include "dh.h"
43: #include "ssh2.h"
44: #include "compat.h"
45:
46: void
47: kexgex_client(Kex *kex)
48: {
49: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
50: BIGNUM *p = NULL, *g = NULL;
51: Key *server_host_key;
52: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
1.10 markus 53: u_int klen, slen, sbloblen, hashlen;
54: int kout;
1.1 markus 55: int min, max, nbits;
56: DH *dh;
57:
1.16 dtucker 58: nbits = dh_estimate(kex->dh_need * 8);
1.1 markus 59:
60: if (datafellows & SSH_OLD_DHGEX) {
61: /* Old GEX request */
62: packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
63: packet_put_int(nbits);
64: min = DH_GRP_MIN;
65: max = DH_GRP_MAX;
1.2 markus 66:
67: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits);
1.1 markus 68: } else {
69: /* New GEX request */
70: min = DH_GRP_MIN;
71: max = DH_GRP_MAX;
72: packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
73: packet_put_int(min);
74: packet_put_int(nbits);
75: packet_put_int(max);
1.2 markus 76:
77: debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
78: min, nbits, max);
1.1 markus 79: }
80: #ifdef DEBUG_KEXDH
81: fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
82: min, nbits, max);
83: #endif
84: packet_send();
85:
86: debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
87: packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
88:
89: if ((p = BN_new()) == NULL)
90: fatal("BN_new");
91: packet_get_bignum2(p);
92: if ((g = BN_new()) == NULL)
93: fatal("BN_new");
94: packet_get_bignum2(g);
95: packet_check_eom();
96:
97: if (BN_num_bits(p) < min || BN_num_bits(p) > max)
98: fatal("DH_GEX group out of range: %d !< %d !< %d",
99: min, BN_num_bits(p), max);
100:
101: dh = dh_new_group(g, p);
102: dh_gen_key(dh, kex->we_need * 8);
103:
104: #ifdef DEBUG_KEXDH
105: DHparams_print_fp(stderr, dh);
106: fprintf(stderr, "pub= ");
107: BN_print_fp(stderr, dh->pub_key);
108: fprintf(stderr, "\n");
109: #endif
110:
111: debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
112: /* generate and send 'e', client DH public key */
113: packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
114: packet_put_bignum2(dh->pub_key);
115: packet_send();
116:
117: debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
118: packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
119:
120: /* key, cert */
121: server_host_key_blob = packet_get_string(&sbloblen);
122: server_host_key = key_from_blob(server_host_key_blob, sbloblen);
123: if (server_host_key == NULL)
124: fatal("cannot decode server_host_key_blob");
125: if (server_host_key->type != kex->hostkey_type)
126: fatal("type mismatch for decoded server_host_key_blob");
127: if (kex->verify_host_key == NULL)
128: fatal("cannot verify server_host_key");
129: if (kex->verify_host_key(server_host_key) == -1)
130: fatal("server_host_key verification failed");
131:
1.6 miod 132: /* DH parameter f, server public DH key */
1.1 markus 133: if ((dh_server_pub = BN_new()) == NULL)
134: fatal("dh_server_pub == NULL");
135: packet_get_bignum2(dh_server_pub);
136:
137: #ifdef DEBUG_KEXDH
138: fprintf(stderr, "dh_server_pub= ");
139: BN_print_fp(stderr, dh_server_pub);
140: fprintf(stderr, "\n");
141: debug("bits %d", BN_num_bits(dh_server_pub));
142: #endif
143:
144: /* signed H */
145: signature = packet_get_string(&slen);
146: packet_check_eom();
147:
148: if (!dh_pub_is_valid(dh, dh_server_pub))
149: packet_disconnect("bad server public DH value");
150:
151: klen = DH_size(dh);
152: kbuf = xmalloc(klen);
1.10 markus 153: if ((kout = DH_compute_key(kbuf, dh_server_pub, dh)) < 0)
154: fatal("DH_compute_key: failed");
1.1 markus 155: #ifdef DEBUG_KEXDH
156: dump_digest("shared secret", kbuf, kout);
157: #endif
158: if ((shared_secret = BN_new()) == NULL)
159: fatal("kexgex_client: BN_new failed");
1.11 markus 160: if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
161: fatal("kexgex_client: BN_bin2bn failed");
1.17 djm 162: explicit_bzero(kbuf, klen);
1.13 djm 163: free(kbuf);
1.1 markus 164:
165: if (datafellows & SSH_OLD_DHGEX)
166: min = max = -1;
167:
168: /* calc and verify H */
1.3 djm 169: kexgex_hash(
1.14 djm 170: kex->hash_alg,
1.1 markus 171: kex->client_version_string,
172: kex->server_version_string,
1.18 ! markus 173: buffer_ptr(kex->my), buffer_len(kex->my),
! 174: buffer_ptr(kex->peer), buffer_len(kex->peer),
1.1 markus 175: server_host_key_blob, sbloblen,
176: min, nbits, max,
177: dh->p, dh->g,
178: dh->pub_key,
179: dh_server_pub,
1.3 djm 180: shared_secret,
181: &hash, &hashlen
1.1 markus 182: );
1.3 djm 183:
1.1 markus 184: /* have keys, free DH */
185: DH_free(dh);
1.13 djm 186: free(server_host_key_blob);
1.1 markus 187: BN_clear_free(dh_server_pub);
188:
1.3 djm 189: if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
1.1 markus 190: fatal("key_verify failed for server_host_key");
191: key_free(server_host_key);
1.13 djm 192: free(signature);
1.1 markus 193:
194: /* save session id */
195: if (kex->session_id == NULL) {
1.3 djm 196: kex->session_id_len = hashlen;
1.1 markus 197: kex->session_id = xmalloc(kex->session_id_len);
198: memcpy(kex->session_id, hash, kex->session_id_len);
199: }
1.15 djm 200: kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
1.1 markus 201: BN_clear_free(shared_secret);
202:
203: kex_finish(kex);
204: }
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