Annotation of src/usr.bin/ssh/kexgexc.c, Revision 1.1.4.2
1.1 markus 1: /*
2: * Copyright (c) 2000 Niels Provos. All rights reserved.
3: * Copyright (c) 2001 Markus Friedl. All rights reserved.
4: *
5: * Redistribution and use in source and binary forms, with or without
6: * modification, are permitted provided that the following conditions
7: * are met:
8: * 1. Redistributions of source code must retain the above copyright
9: * notice, this list of conditions and the following disclaimer.
10: * 2. Redistributions in binary form must reproduce the above copyright
11: * notice, this list of conditions and the following disclaimer in the
12: * documentation and/or other materials provided with the distribution.
13: *
14: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24: */
25:
26: #include "includes.h"
1.1.4.1 margarid 27: RCSID("$OpenBSD: kexgexc.c,v 1.1 2003/02/16 17:09:57 markus Exp $");
1.1 markus 28:
29: #include "xmalloc.h"
30: #include "key.h"
31: #include "kex.h"
32: #include "log.h"
33: #include "packet.h"
34: #include "dh.h"
35: #include "ssh2.h"
36: #include "compat.h"
37:
38: void
39: kexgex_client(Kex *kex)
40: {
41: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
42: BIGNUM *p = NULL, *g = NULL;
43: Key *server_host_key;
44: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
45: u_int klen, kout, slen, sbloblen;
46: int min, max, nbits;
47: DH *dh;
48:
49: nbits = dh_estimate(kex->we_need * 8);
50:
51: if (datafellows & SSH_OLD_DHGEX) {
52: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD sent");
53:
54: /* Old GEX request */
55: packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
56: packet_put_int(nbits);
57: min = DH_GRP_MIN;
58: max = DH_GRP_MAX;
59: } else {
60: debug("SSH2_MSG_KEX_DH_GEX_REQUEST sent");
61:
62: /* New GEX request */
63: min = DH_GRP_MIN;
64: max = DH_GRP_MAX;
65: packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
66: packet_put_int(min);
67: packet_put_int(nbits);
68: packet_put_int(max);
69: }
70: #ifdef DEBUG_KEXDH
71: fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
72: min, nbits, max);
73: #endif
74: packet_send();
75:
76: debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
77: packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
78:
79: if ((p = BN_new()) == NULL)
80: fatal("BN_new");
81: packet_get_bignum2(p);
82: if ((g = BN_new()) == NULL)
83: fatal("BN_new");
84: packet_get_bignum2(g);
85: packet_check_eom();
86:
87: if (BN_num_bits(p) < min || BN_num_bits(p) > max)
88: fatal("DH_GEX group out of range: %d !< %d !< %d",
89: min, BN_num_bits(p), max);
90:
91: dh = dh_new_group(g, p);
92: dh_gen_key(dh, kex->we_need * 8);
93:
94: #ifdef DEBUG_KEXDH
95: DHparams_print_fp(stderr, dh);
96: fprintf(stderr, "pub= ");
97: BN_print_fp(stderr, dh->pub_key);
98: fprintf(stderr, "\n");
99: #endif
100:
101: debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
102: /* generate and send 'e', client DH public key */
103: packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
104: packet_put_bignum2(dh->pub_key);
105: packet_send();
106:
107: debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
108: packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
109:
110: /* key, cert */
111: server_host_key_blob = packet_get_string(&sbloblen);
112: server_host_key = key_from_blob(server_host_key_blob, sbloblen);
113: if (server_host_key == NULL)
114: fatal("cannot decode server_host_key_blob");
115: if (server_host_key->type != kex->hostkey_type)
116: fatal("type mismatch for decoded server_host_key_blob");
117: if (kex->verify_host_key == NULL)
118: fatal("cannot verify server_host_key");
119: if (kex->verify_host_key(server_host_key) == -1)
120: fatal("server_host_key verification failed");
121:
122: /* DH paramter f, server public DH key */
123: if ((dh_server_pub = BN_new()) == NULL)
124: fatal("dh_server_pub == NULL");
125: packet_get_bignum2(dh_server_pub);
126:
127: #ifdef DEBUG_KEXDH
128: fprintf(stderr, "dh_server_pub= ");
129: BN_print_fp(stderr, dh_server_pub);
130: fprintf(stderr, "\n");
131: debug("bits %d", BN_num_bits(dh_server_pub));
132: #endif
133:
134: /* signed H */
135: signature = packet_get_string(&slen);
136: packet_check_eom();
137:
138: if (!dh_pub_is_valid(dh, dh_server_pub))
139: packet_disconnect("bad server public DH value");
140:
141: klen = DH_size(dh);
142: kbuf = xmalloc(klen);
143: kout = DH_compute_key(kbuf, dh_server_pub, dh);
144: #ifdef DEBUG_KEXDH
145: dump_digest("shared secret", kbuf, kout);
146: #endif
147: if ((shared_secret = BN_new()) == NULL)
148: fatal("kexgex_client: BN_new failed");
149: BN_bin2bn(kbuf, kout, shared_secret);
150: memset(kbuf, 0, klen);
151: xfree(kbuf);
152:
153: if (datafellows & SSH_OLD_DHGEX)
154: min = max = -1;
155:
156: /* calc and verify H */
157: hash = kexgex_hash(
158: kex->client_version_string,
159: kex->server_version_string,
160: buffer_ptr(&kex->my), buffer_len(&kex->my),
161: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
162: server_host_key_blob, sbloblen,
163: min, nbits, max,
164: dh->p, dh->g,
165: dh->pub_key,
166: dh_server_pub,
167: shared_secret
168: );
169: /* have keys, free DH */
170: DH_free(dh);
171: xfree(server_host_key_blob);
172: BN_clear_free(dh_server_pub);
173:
174: if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
175: fatal("key_verify failed for server_host_key");
176: key_free(server_host_key);
177: xfree(signature);
178:
179: /* save session id */
180: if (kex->session_id == NULL) {
181: kex->session_id_len = 20;
182: kex->session_id = xmalloc(kex->session_id_len);
183: memcpy(kex->session_id, hash, kex->session_id_len);
184: }
185: kex_derive_keys(kex, hash, shared_secret);
186: BN_clear_free(shared_secret);
187:
188: kex_finish(kex);
189: }