Annotation of src/usr.bin/ssh/kexgexs.c, Revision 1.7
1.7 ! stevesk 1: /* $OpenBSD: kexgexs.c,v 1.6 2006/07/26 02:35:17 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:
1.7 ! stevesk 31: #include <stdio.h>
1.5 stevesk 32: #include <string.h>
1.1 markus 33:
34: #include "xmalloc.h"
35: #include "key.h"
36: #include "kex.h"
37: #include "log.h"
38: #include "packet.h"
39: #include "dh.h"
40: #include "ssh2.h"
41: #include "compat.h"
42: #include "monitor_wrap.h"
43:
44: void
45: kexgex_server(Kex *kex)
46: {
47: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
48: Key *server_host_key;
49: DH *dh;
50: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
1.2 djm 51: u_int sbloblen, klen, kout, slen, hashlen;
1.1 markus 52: int min = -1, max = -1, nbits = -1, type;
53:
54: if (kex->load_host_key == NULL)
55: fatal("Cannot load hostkey");
56: server_host_key = kex->load_host_key(kex->hostkey_type);
57: if (server_host_key == NULL)
58: fatal("Unsupported hostkey type %d", kex->hostkey_type);
59:
60: type = packet_read();
61: switch (type) {
62: case SSH2_MSG_KEX_DH_GEX_REQUEST:
63: debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
64: min = packet_get_int();
65: nbits = packet_get_int();
66: max = packet_get_int();
67: min = MAX(DH_GRP_MIN, min);
68: max = MIN(DH_GRP_MAX, max);
69: break;
70: case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
71: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
72: nbits = packet_get_int();
73: min = DH_GRP_MIN;
74: max = DH_GRP_MAX;
75: /* unused for old GEX */
76: break;
77: default:
78: fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
79: }
80: packet_check_eom();
81:
82: if (max < min || nbits < min || max < nbits)
83: fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
84: min, nbits, max);
85:
86: /* Contact privileged parent */
87: dh = PRIVSEP(choose_dh(min, nbits, max));
88: if (dh == NULL)
89: packet_disconnect("Protocol error: no matching DH grp found");
90:
91: debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
92: packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
93: packet_put_bignum2(dh->p);
94: packet_put_bignum2(dh->g);
95: packet_send();
96:
97: /* flush */
98: packet_write_wait();
99:
100: /* Compute our exchange value in parallel with the client */
101: dh_gen_key(dh, kex->we_need * 8);
102:
103: debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
104: packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
105:
106: /* key, cert */
107: if ((dh_client_pub = BN_new()) == NULL)
108: fatal("dh_client_pub == NULL");
109: packet_get_bignum2(dh_client_pub);
110: packet_check_eom();
111:
112: #ifdef DEBUG_KEXDH
113: fprintf(stderr, "dh_client_pub= ");
114: BN_print_fp(stderr, dh_client_pub);
115: fprintf(stderr, "\n");
116: debug("bits %d", BN_num_bits(dh_client_pub));
117: #endif
118:
119: #ifdef DEBUG_KEXDH
120: DHparams_print_fp(stderr, dh);
121: fprintf(stderr, "pub= ");
122: BN_print_fp(stderr, dh->pub_key);
123: fprintf(stderr, "\n");
124: #endif
125: if (!dh_pub_is_valid(dh, dh_client_pub))
126: packet_disconnect("bad client public DH value");
127:
128: klen = DH_size(dh);
129: kbuf = xmalloc(klen);
130: kout = DH_compute_key(kbuf, dh_client_pub, dh);
131: #ifdef DEBUG_KEXDH
132: dump_digest("shared secret", kbuf, kout);
133: #endif
134: if ((shared_secret = BN_new()) == NULL)
135: fatal("kexgex_server: BN_new failed");
136: BN_bin2bn(kbuf, kout, shared_secret);
137: memset(kbuf, 0, klen);
138: xfree(kbuf);
139:
140: key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
141:
142: if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
143: min = max = -1;
144:
1.2 djm 145: /* calc H */
146: kexgex_hash(
147: kex->evp_md,
1.1 markus 148: kex->client_version_string,
149: kex->server_version_string,
150: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
151: buffer_ptr(&kex->my), buffer_len(&kex->my),
152: server_host_key_blob, sbloblen,
153: min, nbits, max,
154: dh->p, dh->g,
155: dh_client_pub,
156: dh->pub_key,
1.2 djm 157: shared_secret,
158: &hash, &hashlen
1.1 markus 159: );
160: BN_clear_free(dh_client_pub);
161:
162: /* save session id := H */
163: if (kex->session_id == NULL) {
1.2 djm 164: kex->session_id_len = hashlen;
1.1 markus 165: kex->session_id = xmalloc(kex->session_id_len);
166: memcpy(kex->session_id, hash, kex->session_id_len);
167: }
168:
169: /* sign H */
1.2 djm 170: PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen));
1.1 markus 171:
172: /* destroy_sensitive_data(); */
173:
174: /* send server hostkey, DH pubkey 'f' and singed H */
175: debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
176: packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
177: packet_put_string(server_host_key_blob, sbloblen);
178: packet_put_bignum2(dh->pub_key); /* f */
179: packet_put_string(signature, slen);
180: packet_send();
181:
182: xfree(signature);
183: xfree(server_host_key_blob);
184: /* have keys, free DH */
185: DH_free(dh);
186:
1.2 djm 187: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 188: BN_clear_free(shared_secret);
189:
190: kex_finish(kex);
191: }
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