Annotation of src/usr.bin/ssh/kexgexs.c, Revision 1.6
1.6 ! stevesk 1: /* $OpenBSD: kexgexs.c,v 1.5 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"
1.6 ! stevesk 28:
! 29: #include <sys/param.h>
1.5 stevesk 30:
31: #include <string.h>
1.1 markus 32:
33: #include "xmalloc.h"
34: #include "key.h"
35: #include "kex.h"
36: #include "log.h"
37: #include "packet.h"
38: #include "dh.h"
39: #include "ssh2.h"
40: #include "compat.h"
41: #include "monitor_wrap.h"
42:
43: void
44: kexgex_server(Kex *kex)
45: {
46: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
47: Key *server_host_key;
48: DH *dh;
49: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
1.2 djm 50: u_int sbloblen, klen, kout, slen, hashlen;
1.1 markus 51: int min = -1, max = -1, nbits = -1, type;
52:
53: if (kex->load_host_key == NULL)
54: fatal("Cannot load hostkey");
55: server_host_key = kex->load_host_key(kex->hostkey_type);
56: if (server_host_key == NULL)
57: fatal("Unsupported hostkey type %d", kex->hostkey_type);
58:
59: type = packet_read();
60: switch (type) {
61: case SSH2_MSG_KEX_DH_GEX_REQUEST:
62: debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
63: min = packet_get_int();
64: nbits = packet_get_int();
65: max = packet_get_int();
66: min = MAX(DH_GRP_MIN, min);
67: max = MIN(DH_GRP_MAX, max);
68: break;
69: case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
70: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
71: nbits = packet_get_int();
72: min = DH_GRP_MIN;
73: max = DH_GRP_MAX;
74: /* unused for old GEX */
75: break;
76: default:
77: fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
78: }
79: packet_check_eom();
80:
81: if (max < min || nbits < min || max < nbits)
82: fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
83: min, nbits, max);
84:
85: /* Contact privileged parent */
86: dh = PRIVSEP(choose_dh(min, nbits, max));
87: if (dh == NULL)
88: packet_disconnect("Protocol error: no matching DH grp found");
89:
90: debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
91: packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
92: packet_put_bignum2(dh->p);
93: packet_put_bignum2(dh->g);
94: packet_send();
95:
96: /* flush */
97: packet_write_wait();
98:
99: /* Compute our exchange value in parallel with the client */
100: dh_gen_key(dh, kex->we_need * 8);
101:
102: debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
103: packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
104:
105: /* key, cert */
106: if ((dh_client_pub = BN_new()) == NULL)
107: fatal("dh_client_pub == NULL");
108: packet_get_bignum2(dh_client_pub);
109: packet_check_eom();
110:
111: #ifdef DEBUG_KEXDH
112: fprintf(stderr, "dh_client_pub= ");
113: BN_print_fp(stderr, dh_client_pub);
114: fprintf(stderr, "\n");
115: debug("bits %d", BN_num_bits(dh_client_pub));
116: #endif
117:
118: #ifdef DEBUG_KEXDH
119: DHparams_print_fp(stderr, dh);
120: fprintf(stderr, "pub= ");
121: BN_print_fp(stderr, dh->pub_key);
122: fprintf(stderr, "\n");
123: #endif
124: if (!dh_pub_is_valid(dh, dh_client_pub))
125: packet_disconnect("bad client public DH value");
126:
127: klen = DH_size(dh);
128: kbuf = xmalloc(klen);
129: kout = DH_compute_key(kbuf, dh_client_pub, dh);
130: #ifdef DEBUG_KEXDH
131: dump_digest("shared secret", kbuf, kout);
132: #endif
133: if ((shared_secret = BN_new()) == NULL)
134: fatal("kexgex_server: BN_new failed");
135: BN_bin2bn(kbuf, kout, shared_secret);
136: memset(kbuf, 0, klen);
137: xfree(kbuf);
138:
139: key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
140:
141: if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
142: min = max = -1;
143:
1.2 djm 144: /* calc H */
145: kexgex_hash(
146: kex->evp_md,
1.1 markus 147: kex->client_version_string,
148: kex->server_version_string,
149: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
150: buffer_ptr(&kex->my), buffer_len(&kex->my),
151: server_host_key_blob, sbloblen,
152: min, nbits, max,
153: dh->p, dh->g,
154: dh_client_pub,
155: dh->pub_key,
1.2 djm 156: shared_secret,
157: &hash, &hashlen
1.1 markus 158: );
159: BN_clear_free(dh_client_pub);
160:
161: /* save session id := H */
162: if (kex->session_id == NULL) {
1.2 djm 163: kex->session_id_len = hashlen;
1.1 markus 164: kex->session_id = xmalloc(kex->session_id_len);
165: memcpy(kex->session_id, hash, kex->session_id_len);
166: }
167:
168: /* sign H */
1.2 djm 169: PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen));
1.1 markus 170:
171: /* destroy_sensitive_data(); */
172:
173: /* send server hostkey, DH pubkey 'f' and singed H */
174: debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
175: packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
176: packet_put_string(server_host_key_blob, sbloblen);
177: packet_put_bignum2(dh->pub_key); /* f */
178: packet_put_string(signature, slen);
179: packet_send();
180:
181: xfree(signature);
182: xfree(server_host_key_blob);
183: /* have keys, free DH */
184: DH_free(dh);
185:
1.2 djm 186: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 187: BN_clear_free(shared_secret);
188:
189: kex_finish(kex);
190: }