Annotation of src/usr.bin/ssh/kexgexs.c, Revision 1.5
1.5 ! stevesk 1: /* $OpenBSD: kexgexs.c,v 1.4 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"
1.5 ! stevesk 28:
! 29: #include <string.h>
1.1 markus 30:
31: #include "xmalloc.h"
32: #include "key.h"
33: #include "kex.h"
34: #include "log.h"
35: #include "packet.h"
36: #include "dh.h"
37: #include "ssh2.h"
38: #include "compat.h"
39: #include "monitor_wrap.h"
40:
41: void
42: kexgex_server(Kex *kex)
43: {
44: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
45: Key *server_host_key;
46: DH *dh;
47: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
1.2 djm 48: u_int sbloblen, klen, kout, slen, hashlen;
1.1 markus 49: int min = -1, max = -1, nbits = -1, type;
50:
51: if (kex->load_host_key == NULL)
52: fatal("Cannot load hostkey");
53: server_host_key = kex->load_host_key(kex->hostkey_type);
54: if (server_host_key == NULL)
55: fatal("Unsupported hostkey type %d", kex->hostkey_type);
56:
57: type = packet_read();
58: switch (type) {
59: case SSH2_MSG_KEX_DH_GEX_REQUEST:
60: debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
61: min = packet_get_int();
62: nbits = packet_get_int();
63: max = packet_get_int();
64: min = MAX(DH_GRP_MIN, min);
65: max = MIN(DH_GRP_MAX, max);
66: break;
67: case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
68: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
69: nbits = packet_get_int();
70: min = DH_GRP_MIN;
71: max = DH_GRP_MAX;
72: /* unused for old GEX */
73: break;
74: default:
75: fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
76: }
77: packet_check_eom();
78:
79: if (max < min || nbits < min || max < nbits)
80: fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
81: min, nbits, max);
82:
83: /* Contact privileged parent */
84: dh = PRIVSEP(choose_dh(min, nbits, max));
85: if (dh == NULL)
86: packet_disconnect("Protocol error: no matching DH grp found");
87:
88: debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
89: packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
90: packet_put_bignum2(dh->p);
91: packet_put_bignum2(dh->g);
92: packet_send();
93:
94: /* flush */
95: packet_write_wait();
96:
97: /* Compute our exchange value in parallel with the client */
98: dh_gen_key(dh, kex->we_need * 8);
99:
100: debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
101: packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
102:
103: /* key, cert */
104: if ((dh_client_pub = BN_new()) == NULL)
105: fatal("dh_client_pub == NULL");
106: packet_get_bignum2(dh_client_pub);
107: packet_check_eom();
108:
109: #ifdef DEBUG_KEXDH
110: fprintf(stderr, "dh_client_pub= ");
111: BN_print_fp(stderr, dh_client_pub);
112: fprintf(stderr, "\n");
113: debug("bits %d", BN_num_bits(dh_client_pub));
114: #endif
115:
116: #ifdef DEBUG_KEXDH
117: DHparams_print_fp(stderr, dh);
118: fprintf(stderr, "pub= ");
119: BN_print_fp(stderr, dh->pub_key);
120: fprintf(stderr, "\n");
121: #endif
122: if (!dh_pub_is_valid(dh, dh_client_pub))
123: packet_disconnect("bad client public DH value");
124:
125: klen = DH_size(dh);
126: kbuf = xmalloc(klen);
127: kout = DH_compute_key(kbuf, dh_client_pub, dh);
128: #ifdef DEBUG_KEXDH
129: dump_digest("shared secret", kbuf, kout);
130: #endif
131: if ((shared_secret = BN_new()) == NULL)
132: fatal("kexgex_server: BN_new failed");
133: BN_bin2bn(kbuf, kout, shared_secret);
134: memset(kbuf, 0, klen);
135: xfree(kbuf);
136:
137: key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
138:
139: if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
140: min = max = -1;
141:
1.2 djm 142: /* calc H */
143: kexgex_hash(
144: kex->evp_md,
1.1 markus 145: kex->client_version_string,
146: kex->server_version_string,
147: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
148: buffer_ptr(&kex->my), buffer_len(&kex->my),
149: server_host_key_blob, sbloblen,
150: min, nbits, max,
151: dh->p, dh->g,
152: dh_client_pub,
153: dh->pub_key,
1.2 djm 154: shared_secret,
155: &hash, &hashlen
1.1 markus 156: );
157: BN_clear_free(dh_client_pub);
158:
159: /* save session id := H */
160: if (kex->session_id == NULL) {
1.2 djm 161: kex->session_id_len = hashlen;
1.1 markus 162: kex->session_id = xmalloc(kex->session_id_len);
163: memcpy(kex->session_id, hash, kex->session_id_len);
164: }
165:
166: /* sign H */
1.2 djm 167: PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen));
1.1 markus 168:
169: /* destroy_sensitive_data(); */
170:
171: /* send server hostkey, DH pubkey 'f' and singed H */
172: debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
173: packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
174: packet_put_string(server_host_key_blob, sbloblen);
175: packet_put_bignum2(dh->pub_key); /* f */
176: packet_put_string(signature, slen);
177: packet_send();
178:
179: xfree(signature);
180: xfree(server_host_key_blob);
181: /* have keys, free DH */
182: DH_free(dh);
183:
1.2 djm 184: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 185: BN_clear_free(shared_secret);
186:
187: kex_finish(kex);
188: }
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