Annotation of src/usr.bin/ssh/kexgexc.c, Revision 1.4
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"
27:
28: #include "xmalloc.h"
29: #include "key.h"
30: #include "kex.h"
31: #include "log.h"
32: #include "packet.h"
33: #include "dh.h"
34: #include "ssh2.h"
35: #include "compat.h"
36:
37: void
38: kexgex_client(Kex *kex)
39: {
40: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
41: BIGNUM *p = NULL, *g = NULL;
42: Key *server_host_key;
43: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
1.3 djm 44: u_int klen, kout, slen, sbloblen, hashlen;
1.1 markus 45: int min, max, nbits;
46: DH *dh;
47:
48: nbits = dh_estimate(kex->we_need * 8);
49:
50: if (datafellows & SSH_OLD_DHGEX) {
51: /* Old GEX request */
52: packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
53: packet_put_int(nbits);
54: min = DH_GRP_MIN;
55: max = DH_GRP_MAX;
1.2 markus 56:
57: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits);
1.1 markus 58: } else {
59: /* New GEX request */
60: min = DH_GRP_MIN;
61: max = DH_GRP_MAX;
62: packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
63: packet_put_int(min);
64: packet_put_int(nbits);
65: packet_put_int(max);
1.2 markus 66:
67: debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
68: min, nbits, max);
1.1 markus 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 */
1.3 djm 157: kexgex_hash(
158: kex->evp_md,
1.1 markus 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,
1.3 djm 168: shared_secret,
169: &hash, &hashlen
1.1 markus 170: );
1.3 djm 171:
1.1 markus 172: /* have keys, free DH */
173: DH_free(dh);
174: xfree(server_host_key_blob);
175: BN_clear_free(dh_server_pub);
176:
1.3 djm 177: if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
1.1 markus 178: fatal("key_verify failed for server_host_key");
179: key_free(server_host_key);
180: xfree(signature);
181:
182: /* save session id */
183: if (kex->session_id == NULL) {
1.3 djm 184: kex->session_id_len = hashlen;
1.1 markus 185: kex->session_id = xmalloc(kex->session_id_len);
186: memcpy(kex->session_id, hash, kex->session_id_len);
187: }
1.3 djm 188: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 189: BN_clear_free(shared_secret);
190:
191: kex_finish(kex);
192: }
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