Annotation of src/usr.bin/ssh/kexgexs.c, Revision 1.13
1.13 ! djm 1: /* $OpenBSD: kexgexs.c,v 1.12 2009/06/21 07:37:15 dtucker 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;
1.13 ! djm 52: Key *server_host_public, *server_host_private;
1.1 markus 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;
1.11 djm 56: int omin = -1, min = -1, omax = -1, max = -1, onbits = -1, nbits = -1;
57: int type, kout;
1.1 markus 58:
1.13 ! djm 59: if (kex->load_host_public_key == NULL ||
! 60: kex->load_host_private_key == NULL)
1.1 markus 61: fatal("Cannot load hostkey");
1.13 ! djm 62: server_host_public = kex->load_host_public_key(kex->hostkey_type);
! 63: if (server_host_public == NULL)
1.1 markus 64: fatal("Unsupported hostkey type %d", kex->hostkey_type);
1.13 ! djm 65: server_host_private = kex->load_host_private_key(kex->hostkey_type);
! 66: if (server_host_private == NULL)
! 67: fatal("Missing private key for hostkey type %d",
! 68: kex->hostkey_type);
! 69:
1.1 markus 70:
71: type = packet_read();
72: switch (type) {
73: case SSH2_MSG_KEX_DH_GEX_REQUEST:
74: debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
1.11 djm 75: omin = min = packet_get_int();
76: onbits = nbits = packet_get_int();
77: omax = max = packet_get_int();
1.1 markus 78: min = MAX(DH_GRP_MIN, min);
79: max = MIN(DH_GRP_MAX, max);
1.11 djm 80: nbits = MAX(DH_GRP_MIN, nbits);
81: nbits = MIN(DH_GRP_MAX, nbits);
1.1 markus 82: break;
83: case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
84: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
1.11 djm 85: onbits = nbits = packet_get_int();
1.1 markus 86: /* unused for old GEX */
1.11 djm 87: omin = min = DH_GRP_MIN;
88: omax = max = DH_GRP_MAX;
1.1 markus 89: break;
90: default:
91: fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
92: }
93: packet_check_eom();
94:
1.11 djm 95: if (omax < omin || onbits < omin || omax < onbits)
1.1 markus 96: fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
1.11 djm 97: omin, onbits, omax);
1.1 markus 98:
99: /* Contact privileged parent */
100: dh = PRIVSEP(choose_dh(min, nbits, max));
101: if (dh == NULL)
102: packet_disconnect("Protocol error: no matching DH grp found");
103:
104: debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
105: packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
106: packet_put_bignum2(dh->p);
107: packet_put_bignum2(dh->g);
108: packet_send();
109:
110: /* flush */
111: packet_write_wait();
112:
113: /* Compute our exchange value in parallel with the client */
114: dh_gen_key(dh, kex->we_need * 8);
115:
116: debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
117: packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
118:
119: /* key, cert */
120: if ((dh_client_pub = BN_new()) == NULL)
121: fatal("dh_client_pub == NULL");
122: packet_get_bignum2(dh_client_pub);
123: packet_check_eom();
124:
125: #ifdef DEBUG_KEXDH
126: fprintf(stderr, "dh_client_pub= ");
127: BN_print_fp(stderr, dh_client_pub);
128: fprintf(stderr, "\n");
129: debug("bits %d", BN_num_bits(dh_client_pub));
130: #endif
131:
132: #ifdef DEBUG_KEXDH
133: DHparams_print_fp(stderr, dh);
134: fprintf(stderr, "pub= ");
135: BN_print_fp(stderr, dh->pub_key);
136: fprintf(stderr, "\n");
137: #endif
138: if (!dh_pub_is_valid(dh, dh_client_pub))
139: packet_disconnect("bad client public DH value");
140:
141: klen = DH_size(dh);
142: kbuf = xmalloc(klen);
1.9 markus 143: if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
144: fatal("DH_compute_key: failed");
1.1 markus 145: #ifdef DEBUG_KEXDH
146: dump_digest("shared secret", kbuf, kout);
147: #endif
148: if ((shared_secret = BN_new()) == NULL)
149: fatal("kexgex_server: BN_new failed");
1.10 markus 150: if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
151: fatal("kexgex_server: BN_bin2bn failed");
1.1 markus 152: memset(kbuf, 0, klen);
153: xfree(kbuf);
154:
1.13 ! djm 155: key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
1.1 markus 156:
157: if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
1.11 djm 158: omin = min = omax = max = -1;
1.1 markus 159:
1.2 djm 160: /* calc H */
161: kexgex_hash(
162: kex->evp_md,
1.1 markus 163: kex->client_version_string,
164: kex->server_version_string,
165: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
166: buffer_ptr(&kex->my), buffer_len(&kex->my),
167: server_host_key_blob, sbloblen,
1.11 djm 168: omin, onbits, omax,
1.1 markus 169: dh->p, dh->g,
170: dh_client_pub,
171: dh->pub_key,
1.2 djm 172: shared_secret,
173: &hash, &hashlen
1.1 markus 174: );
175: BN_clear_free(dh_client_pub);
176:
177: /* save session id := H */
178: if (kex->session_id == NULL) {
1.2 djm 179: kex->session_id_len = hashlen;
1.1 markus 180: kex->session_id = xmalloc(kex->session_id_len);
181: memcpy(kex->session_id, hash, kex->session_id_len);
182: }
183:
184: /* sign H */
1.13 ! djm 185: if (PRIVSEP(key_sign(server_host_private, &signature, &slen, hash,
1.12 dtucker 186: hashlen)) < 0)
187: fatal("kexgex_server: key_sign failed");
1.1 markus 188:
189: /* destroy_sensitive_data(); */
190:
191: /* send server hostkey, DH pubkey 'f' and singed H */
192: debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
193: packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
194: packet_put_string(server_host_key_blob, sbloblen);
195: packet_put_bignum2(dh->pub_key); /* f */
196: packet_put_string(signature, slen);
197: packet_send();
198:
199: xfree(signature);
200: xfree(server_host_key_blob);
201: /* have keys, free DH */
202: DH_free(dh);
203:
1.2 djm 204: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 205: BN_clear_free(shared_secret);
206:
207: kex_finish(kex);
208: }
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