Annotation of src/usr.bin/ssh/kexgexc.c, Revision 1.1.2.1
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"
1.1.2.1 ! brad 27: RCSID("$OpenBSD: kexgexc.c,v 1.2 2003/12/08 11:00:47 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: /* 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;
57:
1.1.2.1 ! brad 58: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits);
! 59: } else {
1.1 markus 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);
1.1.2.1 ! brad 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:
123: /* DH paramter f, server public DH key */
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 */
158: hash = kexgex_hash(
159: kex->client_version_string,
160: kex->server_version_string,
161: buffer_ptr(&kex->my), buffer_len(&kex->my),
162: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
163: server_host_key_blob, sbloblen,
164: min, nbits, max,
165: dh->p, dh->g,
166: dh->pub_key,
167: dh_server_pub,
168: shared_secret
169: );
170: /* have keys, free DH */
171: DH_free(dh);
172: xfree(server_host_key_blob);
173: BN_clear_free(dh_server_pub);
174:
175: if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
176: fatal("key_verify failed for server_host_key");
177: key_free(server_host_key);
178: xfree(signature);
179:
180: /* save session id */
181: if (kex->session_id == NULL) {
182: kex->session_id_len = 20;
183: kex->session_id = xmalloc(kex->session_id_len);
184: memcpy(kex->session_id, hash, kex->session_id_len);
185: }
186: kex_derive_keys(kex, hash, shared_secret);
187: BN_clear_free(shared_secret);
188:
189: kex_finish(kex);
190: }
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