Annotation of src/usr.bin/ssh/kexgexc.c, Revision 1.8
1.8 ! stevesk 1: /* $OpenBSD: kexgexc.c,v 1.7 2006/07/22 20:48:23 stevesk 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:
27: #include "includes.h"
1.7 stevesk 28:
1.8 ! stevesk 29: #include <stdio.h>
1.7 stevesk 30: #include <string.h>
1.1 markus 31:
32: #include "xmalloc.h"
33: #include "key.h"
34: #include "kex.h"
35: #include "log.h"
36: #include "packet.h"
37: #include "dh.h"
38: #include "ssh2.h"
39: #include "compat.h"
40:
41: void
42: kexgex_client(Kex *kex)
43: {
44: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
45: BIGNUM *p = NULL, *g = NULL;
46: Key *server_host_key;
47: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
1.3 djm 48: u_int klen, kout, slen, sbloblen, hashlen;
1.1 markus 49: int min, max, nbits;
50: DH *dh;
51:
52: nbits = dh_estimate(kex->we_need * 8);
53:
54: if (datafellows & SSH_OLD_DHGEX) {
55: /* Old GEX request */
56: packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
57: packet_put_int(nbits);
58: min = DH_GRP_MIN;
59: max = DH_GRP_MAX;
1.2 markus 60:
61: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits);
1.1 markus 62: } else {
63: /* New GEX request */
64: min = DH_GRP_MIN;
65: max = DH_GRP_MAX;
66: packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
67: packet_put_int(min);
68: packet_put_int(nbits);
69: packet_put_int(max);
1.2 markus 70:
71: debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
72: min, nbits, max);
1.1 markus 73: }
74: #ifdef DEBUG_KEXDH
75: fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
76: min, nbits, max);
77: #endif
78: packet_send();
79:
80: debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
81: packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
82:
83: if ((p = BN_new()) == NULL)
84: fatal("BN_new");
85: packet_get_bignum2(p);
86: if ((g = BN_new()) == NULL)
87: fatal("BN_new");
88: packet_get_bignum2(g);
89: packet_check_eom();
90:
91: if (BN_num_bits(p) < min || BN_num_bits(p) > max)
92: fatal("DH_GEX group out of range: %d !< %d !< %d",
93: min, BN_num_bits(p), max);
94:
95: dh = dh_new_group(g, p);
96: dh_gen_key(dh, kex->we_need * 8);
97:
98: #ifdef DEBUG_KEXDH
99: DHparams_print_fp(stderr, dh);
100: fprintf(stderr, "pub= ");
101: BN_print_fp(stderr, dh->pub_key);
102: fprintf(stderr, "\n");
103: #endif
104:
105: debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
106: /* generate and send 'e', client DH public key */
107: packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
108: packet_put_bignum2(dh->pub_key);
109: packet_send();
110:
111: debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
112: packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
113:
114: /* key, cert */
115: server_host_key_blob = packet_get_string(&sbloblen);
116: server_host_key = key_from_blob(server_host_key_blob, sbloblen);
117: if (server_host_key == NULL)
118: fatal("cannot decode server_host_key_blob");
119: if (server_host_key->type != kex->hostkey_type)
120: fatal("type mismatch for decoded server_host_key_blob");
121: if (kex->verify_host_key == NULL)
122: fatal("cannot verify server_host_key");
123: if (kex->verify_host_key(server_host_key) == -1)
124: fatal("server_host_key verification failed");
125:
1.6 miod 126: /* DH parameter f, server public DH key */
1.1 markus 127: if ((dh_server_pub = BN_new()) == NULL)
128: fatal("dh_server_pub == NULL");
129: packet_get_bignum2(dh_server_pub);
130:
131: #ifdef DEBUG_KEXDH
132: fprintf(stderr, "dh_server_pub= ");
133: BN_print_fp(stderr, dh_server_pub);
134: fprintf(stderr, "\n");
135: debug("bits %d", BN_num_bits(dh_server_pub));
136: #endif
137:
138: /* signed H */
139: signature = packet_get_string(&slen);
140: packet_check_eom();
141:
142: if (!dh_pub_is_valid(dh, dh_server_pub))
143: packet_disconnect("bad server public DH value");
144:
145: klen = DH_size(dh);
146: kbuf = xmalloc(klen);
147: kout = DH_compute_key(kbuf, dh_server_pub, dh);
148: #ifdef DEBUG_KEXDH
149: dump_digest("shared secret", kbuf, kout);
150: #endif
151: if ((shared_secret = BN_new()) == NULL)
152: fatal("kexgex_client: BN_new failed");
153: BN_bin2bn(kbuf, kout, shared_secret);
154: memset(kbuf, 0, klen);
155: xfree(kbuf);
156:
157: if (datafellows & SSH_OLD_DHGEX)
158: min = max = -1;
159:
160: /* calc and verify H */
1.3 djm 161: kexgex_hash(
162: kex->evp_md,
1.1 markus 163: kex->client_version_string,
164: kex->server_version_string,
165: buffer_ptr(&kex->my), buffer_len(&kex->my),
166: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
167: server_host_key_blob, sbloblen,
168: min, nbits, max,
169: dh->p, dh->g,
170: dh->pub_key,
171: dh_server_pub,
1.3 djm 172: shared_secret,
173: &hash, &hashlen
1.1 markus 174: );
1.3 djm 175:
1.1 markus 176: /* have keys, free DH */
177: DH_free(dh);
178: xfree(server_host_key_blob);
179: BN_clear_free(dh_server_pub);
180:
1.3 djm 181: if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
1.1 markus 182: fatal("key_verify failed for server_host_key");
183: key_free(server_host_key);
184: xfree(signature);
185:
186: /* save session id */
187: if (kex->session_id == NULL) {
1.3 djm 188: kex->session_id_len = hashlen;
1.1 markus 189: kex->session_id = xmalloc(kex->session_id_len);
190: memcpy(kex->session_id, hash, kex->session_id_len);
191: }
1.3 djm 192: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 193: BN_clear_free(shared_secret);
194:
195: kex_finish(kex);
196: }