Annotation of src/usr.bin/ssh/kexgexs.c, Revision 1.18
1.18 ! djm 1: /* $OpenBSD: kexgexs.c,v 1.17 2014/01/09 23:20:00 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:
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>
1.14 djm 32:
33: #include <openssl/dh.h>
1.1 markus 34:
35: #include "xmalloc.h"
1.8 deraadt 36: #include "buffer.h"
1.1 markus 37: #include "key.h"
1.8 deraadt 38: #include "cipher.h"
1.1 markus 39: #include "kex.h"
40: #include "log.h"
41: #include "packet.h"
42: #include "dh.h"
43: #include "ssh2.h"
44: #include "compat.h"
1.8 deraadt 45: #ifdef GSSAPI
46: #include "ssh-gss.h"
47: #endif
1.1 markus 48: #include "monitor_wrap.h"
49:
50: void
51: kexgex_server(Kex *kex)
52: {
53: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
1.13 djm 54: Key *server_host_public, *server_host_private;
1.1 markus 55: DH *dh;
56: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
1.9 markus 57: u_int sbloblen, klen, slen, hashlen;
1.11 djm 58: int omin = -1, min = -1, omax = -1, max = -1, onbits = -1, nbits = -1;
59: int type, kout;
1.1 markus 60:
1.13 djm 61: if (kex->load_host_public_key == NULL ||
62: kex->load_host_private_key == NULL)
1.1 markus 63: fatal("Cannot load hostkey");
1.13 djm 64: server_host_public = kex->load_host_public_key(kex->hostkey_type);
65: if (server_host_public == NULL)
1.1 markus 66: fatal("Unsupported hostkey type %d", kex->hostkey_type);
1.13 djm 67: server_host_private = kex->load_host_private_key(kex->hostkey_type);
1.1 markus 68:
69: type = packet_read();
70: switch (type) {
71: case SSH2_MSG_KEX_DH_GEX_REQUEST:
72: debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
1.11 djm 73: omin = min = packet_get_int();
74: onbits = nbits = packet_get_int();
75: omax = max = packet_get_int();
1.1 markus 76: min = MAX(DH_GRP_MIN, min);
77: max = MIN(DH_GRP_MAX, max);
1.11 djm 78: nbits = MAX(DH_GRP_MIN, nbits);
79: nbits = MIN(DH_GRP_MAX, nbits);
1.1 markus 80: break;
81: case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
82: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
1.11 djm 83: onbits = nbits = packet_get_int();
1.1 markus 84: /* unused for old GEX */
1.11 djm 85: omin = min = DH_GRP_MIN;
86: omax = max = DH_GRP_MAX;
1.1 markus 87: break;
88: default:
89: fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
90: }
91: packet_check_eom();
92:
1.11 djm 93: if (omax < omin || onbits < omin || omax < onbits)
1.1 markus 94: fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
1.11 djm 95: omin, onbits, omax);
1.1 markus 96:
97: /* Contact privileged parent */
98: dh = PRIVSEP(choose_dh(min, nbits, max));
99: if (dh == NULL)
100: packet_disconnect("Protocol error: no matching DH grp found");
101:
102: debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
103: packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
104: packet_put_bignum2(dh->p);
105: packet_put_bignum2(dh->g);
106: packet_send();
107:
108: /* flush */
109: packet_write_wait();
110:
111: /* Compute our exchange value in parallel with the client */
112: dh_gen_key(dh, kex->we_need * 8);
113:
114: debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
115: packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
116:
117: /* key, cert */
118: if ((dh_client_pub = BN_new()) == NULL)
119: fatal("dh_client_pub == NULL");
120: packet_get_bignum2(dh_client_pub);
121: packet_check_eom();
122:
123: #ifdef DEBUG_KEXDH
124: fprintf(stderr, "dh_client_pub= ");
125: BN_print_fp(stderr, dh_client_pub);
126: fprintf(stderr, "\n");
127: debug("bits %d", BN_num_bits(dh_client_pub));
128: #endif
129:
130: #ifdef DEBUG_KEXDH
131: DHparams_print_fp(stderr, dh);
132: fprintf(stderr, "pub= ");
133: BN_print_fp(stderr, dh->pub_key);
134: fprintf(stderr, "\n");
135: #endif
136: if (!dh_pub_is_valid(dh, dh_client_pub))
137: packet_disconnect("bad client public DH value");
138:
139: klen = DH_size(dh);
140: kbuf = xmalloc(klen);
1.9 markus 141: if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
142: fatal("DH_compute_key: failed");
1.1 markus 143: #ifdef DEBUG_KEXDH
144: dump_digest("shared secret", kbuf, kout);
145: #endif
146: if ((shared_secret = BN_new()) == NULL)
147: fatal("kexgex_server: BN_new failed");
1.10 markus 148: if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
149: fatal("kexgex_server: BN_bin2bn failed");
1.1 markus 150: memset(kbuf, 0, klen);
1.15 djm 151: free(kbuf);
1.1 markus 152:
1.13 djm 153: key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
1.1 markus 154:
155: if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
1.11 djm 156: omin = min = omax = max = -1;
1.1 markus 157:
1.2 djm 158: /* calc H */
159: kexgex_hash(
1.17 djm 160: kex->hash_alg,
1.1 markus 161: kex->client_version_string,
162: kex->server_version_string,
163: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
164: buffer_ptr(&kex->my), buffer_len(&kex->my),
165: server_host_key_blob, sbloblen,
1.11 djm 166: omin, onbits, omax,
1.1 markus 167: dh->p, dh->g,
168: dh_client_pub,
169: dh->pub_key,
1.2 djm 170: shared_secret,
171: &hash, &hashlen
1.1 markus 172: );
173: BN_clear_free(dh_client_pub);
174:
175: /* save session id := H */
176: if (kex->session_id == NULL) {
1.2 djm 177: kex->session_id_len = hashlen;
1.1 markus 178: kex->session_id = xmalloc(kex->session_id_len);
179: memcpy(kex->session_id, hash, kex->session_id_len);
180: }
181:
182: /* sign H */
1.16 markus 183: kex->sign(server_host_private, server_host_public, &signature, &slen,
184: hash, hashlen);
1.1 markus 185:
186: /* destroy_sensitive_data(); */
187:
188: /* send server hostkey, DH pubkey 'f' and singed H */
189: debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
190: packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
191: packet_put_string(server_host_key_blob, sbloblen);
192: packet_put_bignum2(dh->pub_key); /* f */
193: packet_put_string(signature, slen);
194: packet_send();
195:
1.15 djm 196: free(signature);
197: free(server_host_key_blob);
1.1 markus 198: /* have keys, free DH */
199: DH_free(dh);
200:
1.18 ! djm 201: kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
1.1 markus 202: BN_clear_free(shared_secret);
203:
204: kex_finish(kex);
205: }
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