Annotation of src/usr.bin/ssh/kexgexc.c, Revision 1.6
1.6 ! miod 1: /* $OpenBSD: kexgexc.c,v 1.5 2006/03/25 13:17:02 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:
27: #include "includes.h"
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;
1.3 djm 45: u_int klen, kout, slen, sbloblen, hashlen;
1.1 markus 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: /* Old GEX request */
53: packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
54: packet_put_int(nbits);
55: min = DH_GRP_MIN;
56: max = DH_GRP_MAX;
1.2 markus 57:
58: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits);
1.1 markus 59: } else {
60: /* New GEX request */
61: min = DH_GRP_MIN;
62: max = DH_GRP_MAX;
63: packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
64: packet_put_int(min);
65: packet_put_int(nbits);
66: packet_put_int(max);
1.2 markus 67:
68: debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
69: min, nbits, max);
1.1 markus 70: }
71: #ifdef DEBUG_KEXDH
72: fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
73: min, nbits, max);
74: #endif
75: packet_send();
76:
77: debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
78: packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
79:
80: if ((p = BN_new()) == NULL)
81: fatal("BN_new");
82: packet_get_bignum2(p);
83: if ((g = BN_new()) == NULL)
84: fatal("BN_new");
85: packet_get_bignum2(g);
86: packet_check_eom();
87:
88: if (BN_num_bits(p) < min || BN_num_bits(p) > max)
89: fatal("DH_GEX group out of range: %d !< %d !< %d",
90: min, BN_num_bits(p), max);
91:
92: dh = dh_new_group(g, p);
93: dh_gen_key(dh, kex->we_need * 8);
94:
95: #ifdef DEBUG_KEXDH
96: DHparams_print_fp(stderr, dh);
97: fprintf(stderr, "pub= ");
98: BN_print_fp(stderr, dh->pub_key);
99: fprintf(stderr, "\n");
100: #endif
101:
102: debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
103: /* generate and send 'e', client DH public key */
104: packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
105: packet_put_bignum2(dh->pub_key);
106: packet_send();
107:
108: debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
109: packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
110:
111: /* key, cert */
112: server_host_key_blob = packet_get_string(&sbloblen);
113: server_host_key = key_from_blob(server_host_key_blob, sbloblen);
114: if (server_host_key == NULL)
115: fatal("cannot decode server_host_key_blob");
116: if (server_host_key->type != kex->hostkey_type)
117: fatal("type mismatch for decoded server_host_key_blob");
118: if (kex->verify_host_key == NULL)
119: fatal("cannot verify server_host_key");
120: if (kex->verify_host_key(server_host_key) == -1)
121: fatal("server_host_key verification failed");
122:
1.6 ! miod 123: /* DH parameter f, server public DH key */
1.1 markus 124: if ((dh_server_pub = BN_new()) == NULL)
125: fatal("dh_server_pub == NULL");
126: packet_get_bignum2(dh_server_pub);
127:
128: #ifdef DEBUG_KEXDH
129: fprintf(stderr, "dh_server_pub= ");
130: BN_print_fp(stderr, dh_server_pub);
131: fprintf(stderr, "\n");
132: debug("bits %d", BN_num_bits(dh_server_pub));
133: #endif
134:
135: /* signed H */
136: signature = packet_get_string(&slen);
137: packet_check_eom();
138:
139: if (!dh_pub_is_valid(dh, dh_server_pub))
140: packet_disconnect("bad server public DH value");
141:
142: klen = DH_size(dh);
143: kbuf = xmalloc(klen);
144: kout = DH_compute_key(kbuf, dh_server_pub, dh);
145: #ifdef DEBUG_KEXDH
146: dump_digest("shared secret", kbuf, kout);
147: #endif
148: if ((shared_secret = BN_new()) == NULL)
149: fatal("kexgex_client: BN_new failed");
150: BN_bin2bn(kbuf, kout, shared_secret);
151: memset(kbuf, 0, klen);
152: xfree(kbuf);
153:
154: if (datafellows & SSH_OLD_DHGEX)
155: min = max = -1;
156:
157: /* calc and verify H */
1.3 djm 158: kexgex_hash(
159: kex->evp_md,
1.1 markus 160: kex->client_version_string,
161: kex->server_version_string,
162: buffer_ptr(&kex->my), buffer_len(&kex->my),
163: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
164: server_host_key_blob, sbloblen,
165: min, nbits, max,
166: dh->p, dh->g,
167: dh->pub_key,
168: dh_server_pub,
1.3 djm 169: shared_secret,
170: &hash, &hashlen
1.1 markus 171: );
1.3 djm 172:
1.1 markus 173: /* have keys, free DH */
174: DH_free(dh);
175: xfree(server_host_key_blob);
176: BN_clear_free(dh_server_pub);
177:
1.3 djm 178: if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
1.1 markus 179: fatal("key_verify failed for server_host_key");
180: key_free(server_host_key);
181: xfree(signature);
182:
183: /* save session id */
184: if (kex->session_id == NULL) {
1.3 djm 185: kex->session_id_len = hashlen;
1.1 markus 186: kex->session_id = xmalloc(kex->session_id_len);
187: memcpy(kex->session_id, hash, kex->session_id_len);
188: }
1.3 djm 189: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 190: BN_clear_free(shared_secret);
191:
192: kex_finish(kex);
193: }
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