Annotation of src/usr.bin/ssh/kexgexs.c, Revision 1.10
1.10 ! markus 1: /* $OpenBSD: kexgexs.c,v 1.9 2006/10/31 16:33:12 markus 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:
1.6 stevesk 27: #include <sys/param.h>
1.5 stevesk 28:
1.7 stevesk 29: #include <stdio.h>
1.5 stevesk 30: #include <string.h>
1.8 deraadt 31: #include <signal.h>
1.1 markus 32:
33: #include "xmalloc.h"
1.8 deraadt 34: #include "buffer.h"
1.1 markus 35: #include "key.h"
1.8 deraadt 36: #include "cipher.h"
1.1 markus 37: #include "kex.h"
38: #include "log.h"
39: #include "packet.h"
40: #include "dh.h"
41: #include "ssh2.h"
42: #include "compat.h"
1.8 deraadt 43: #ifdef GSSAPI
44: #include "ssh-gss.h"
45: #endif
1.1 markus 46: #include "monitor_wrap.h"
47:
48: void
49: kexgex_server(Kex *kex)
50: {
51: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
52: Key *server_host_key;
53: DH *dh;
54: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
1.9 markus 55: u_int sbloblen, klen, slen, hashlen;
56: int min = -1, max = -1, nbits = -1, type, kout;
1.1 markus 57:
58: if (kex->load_host_key == NULL)
59: fatal("Cannot load hostkey");
60: server_host_key = kex->load_host_key(kex->hostkey_type);
61: if (server_host_key == NULL)
62: fatal("Unsupported hostkey type %d", kex->hostkey_type);
63:
64: type = packet_read();
65: switch (type) {
66: case SSH2_MSG_KEX_DH_GEX_REQUEST:
67: debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
68: min = packet_get_int();
69: nbits = packet_get_int();
70: max = packet_get_int();
71: min = MAX(DH_GRP_MIN, min);
72: max = MIN(DH_GRP_MAX, max);
73: break;
74: case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
75: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
76: nbits = packet_get_int();
77: min = DH_GRP_MIN;
78: max = DH_GRP_MAX;
79: /* unused for old GEX */
80: break;
81: default:
82: fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
83: }
84: packet_check_eom();
85:
86: if (max < min || nbits < min || max < nbits)
87: fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
88: min, nbits, max);
89:
90: /* Contact privileged parent */
91: dh = PRIVSEP(choose_dh(min, nbits, max));
92: if (dh == NULL)
93: packet_disconnect("Protocol error: no matching DH grp found");
94:
95: debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
96: packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
97: packet_put_bignum2(dh->p);
98: packet_put_bignum2(dh->g);
99: packet_send();
100:
101: /* flush */
102: packet_write_wait();
103:
104: /* Compute our exchange value in parallel with the client */
105: dh_gen_key(dh, kex->we_need * 8);
106:
107: debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
108: packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
109:
110: /* key, cert */
111: if ((dh_client_pub = BN_new()) == NULL)
112: fatal("dh_client_pub == NULL");
113: packet_get_bignum2(dh_client_pub);
114: packet_check_eom();
115:
116: #ifdef DEBUG_KEXDH
117: fprintf(stderr, "dh_client_pub= ");
118: BN_print_fp(stderr, dh_client_pub);
119: fprintf(stderr, "\n");
120: debug("bits %d", BN_num_bits(dh_client_pub));
121: #endif
122:
123: #ifdef DEBUG_KEXDH
124: DHparams_print_fp(stderr, dh);
125: fprintf(stderr, "pub= ");
126: BN_print_fp(stderr, dh->pub_key);
127: fprintf(stderr, "\n");
128: #endif
129: if (!dh_pub_is_valid(dh, dh_client_pub))
130: packet_disconnect("bad client public DH value");
131:
132: klen = DH_size(dh);
133: kbuf = xmalloc(klen);
1.9 markus 134: if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
135: fatal("DH_compute_key: failed");
1.1 markus 136: #ifdef DEBUG_KEXDH
137: dump_digest("shared secret", kbuf, kout);
138: #endif
139: if ((shared_secret = BN_new()) == NULL)
140: fatal("kexgex_server: BN_new failed");
1.10 ! markus 141: if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
! 142: fatal("kexgex_server: BN_bin2bn failed");
1.1 markus 143: memset(kbuf, 0, klen);
144: xfree(kbuf);
145:
146: key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
147:
148: if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
149: min = max = -1;
150:
1.2 djm 151: /* calc H */
152: kexgex_hash(
153: kex->evp_md,
1.1 markus 154: kex->client_version_string,
155: kex->server_version_string,
156: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
157: buffer_ptr(&kex->my), buffer_len(&kex->my),
158: server_host_key_blob, sbloblen,
159: min, nbits, max,
160: dh->p, dh->g,
161: dh_client_pub,
162: dh->pub_key,
1.2 djm 163: shared_secret,
164: &hash, &hashlen
1.1 markus 165: );
166: BN_clear_free(dh_client_pub);
167:
168: /* save session id := H */
169: if (kex->session_id == NULL) {
1.2 djm 170: kex->session_id_len = hashlen;
1.1 markus 171: kex->session_id = xmalloc(kex->session_id_len);
172: memcpy(kex->session_id, hash, kex->session_id_len);
173: }
174:
175: /* sign H */
1.2 djm 176: PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen));
1.1 markus 177:
178: /* destroy_sensitive_data(); */
179:
180: /* send server hostkey, DH pubkey 'f' and singed H */
181: debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
182: packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
183: packet_put_string(server_host_key_blob, sbloblen);
184: packet_put_bignum2(dh->pub_key); /* f */
185: packet_put_string(signature, slen);
186: packet_send();
187:
188: xfree(signature);
189: xfree(server_host_key_blob);
190: /* have keys, free DH */
191: DH_free(dh);
192:
1.2 djm 193: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 194: BN_clear_free(shared_secret);
195:
196: kex_finish(kex);
197: }
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