Annotation of src/usr.bin/ssh/kexgexs.c, Revision 1.11
1.11 ! djm 1: /* $OpenBSD: kexgexs.c,v 1.10 2006/11/06 21:25:28 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;
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:
59: if (kex->load_host_key == NULL)
60: fatal("Cannot load hostkey");
61: server_host_key = kex->load_host_key(kex->hostkey_type);
62: if (server_host_key == NULL)
63: fatal("Unsupported hostkey type %d", kex->hostkey_type);
64:
65: type = packet_read();
66: switch (type) {
67: case SSH2_MSG_KEX_DH_GEX_REQUEST:
68: debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
1.11 ! djm 69: omin = min = packet_get_int();
! 70: onbits = nbits = packet_get_int();
! 71: omax = max = packet_get_int();
1.1 markus 72: min = MAX(DH_GRP_MIN, min);
73: max = MIN(DH_GRP_MAX, max);
1.11 ! djm 74: nbits = MAX(DH_GRP_MIN, nbits);
! 75: nbits = MIN(DH_GRP_MAX, nbits);
1.1 markus 76: break;
77: case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
78: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
1.11 ! djm 79: onbits = nbits = packet_get_int();
1.1 markus 80: /* unused for old GEX */
1.11 ! djm 81: omin = min = DH_GRP_MIN;
! 82: omax = max = DH_GRP_MAX;
1.1 markus 83: break;
84: default:
85: fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
86: }
87: packet_check_eom();
88:
1.11 ! djm 89: if (omax < omin || onbits < omin || omax < onbits)
1.1 markus 90: fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
1.11 ! djm 91: omin, onbits, omax);
1.1 markus 92:
93: /* Contact privileged parent */
94: dh = PRIVSEP(choose_dh(min, nbits, max));
95: if (dh == NULL)
96: packet_disconnect("Protocol error: no matching DH grp found");
97:
98: debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
99: packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
100: packet_put_bignum2(dh->p);
101: packet_put_bignum2(dh->g);
102: packet_send();
103:
104: /* flush */
105: packet_write_wait();
106:
107: /* Compute our exchange value in parallel with the client */
108: dh_gen_key(dh, kex->we_need * 8);
109:
110: debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
111: packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
112:
113: /* key, cert */
114: if ((dh_client_pub = BN_new()) == NULL)
115: fatal("dh_client_pub == NULL");
116: packet_get_bignum2(dh_client_pub);
117: packet_check_eom();
118:
119: #ifdef DEBUG_KEXDH
120: fprintf(stderr, "dh_client_pub= ");
121: BN_print_fp(stderr, dh_client_pub);
122: fprintf(stderr, "\n");
123: debug("bits %d", BN_num_bits(dh_client_pub));
124: #endif
125:
126: #ifdef DEBUG_KEXDH
127: DHparams_print_fp(stderr, dh);
128: fprintf(stderr, "pub= ");
129: BN_print_fp(stderr, dh->pub_key);
130: fprintf(stderr, "\n");
131: #endif
132: if (!dh_pub_is_valid(dh, dh_client_pub))
133: packet_disconnect("bad client public DH value");
134:
135: klen = DH_size(dh);
136: kbuf = xmalloc(klen);
1.9 markus 137: if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
138: fatal("DH_compute_key: failed");
1.1 markus 139: #ifdef DEBUG_KEXDH
140: dump_digest("shared secret", kbuf, kout);
141: #endif
142: if ((shared_secret = BN_new()) == NULL)
143: fatal("kexgex_server: BN_new failed");
1.10 markus 144: if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
145: fatal("kexgex_server: BN_bin2bn failed");
1.1 markus 146: memset(kbuf, 0, klen);
147: xfree(kbuf);
148:
149: key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
150:
151: if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
1.11 ! djm 152: omin = min = omax = max = -1;
1.1 markus 153:
1.2 djm 154: /* calc H */
155: kexgex_hash(
156: kex->evp_md,
1.1 markus 157: kex->client_version_string,
158: kex->server_version_string,
159: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
160: buffer_ptr(&kex->my), buffer_len(&kex->my),
161: server_host_key_blob, sbloblen,
1.11 ! djm 162: omin, onbits, omax,
1.1 markus 163: dh->p, dh->g,
164: dh_client_pub,
165: dh->pub_key,
1.2 djm 166: shared_secret,
167: &hash, &hashlen
1.1 markus 168: );
169: BN_clear_free(dh_client_pub);
170:
171: /* save session id := H */
172: if (kex->session_id == NULL) {
1.2 djm 173: kex->session_id_len = hashlen;
1.1 markus 174: kex->session_id = xmalloc(kex->session_id_len);
175: memcpy(kex->session_id, hash, kex->session_id_len);
176: }
177:
178: /* sign H */
1.2 djm 179: PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen));
1.1 markus 180:
181: /* destroy_sensitive_data(); */
182:
183: /* send server hostkey, DH pubkey 'f' and singed H */
184: debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
185: packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
186: packet_put_string(server_host_key_blob, sbloblen);
187: packet_put_bignum2(dh->pub_key); /* f */
188: packet_put_string(signature, slen);
189: packet_send();
190:
191: xfree(signature);
192: xfree(server_host_key_blob);
193: /* have keys, free DH */
194: DH_free(dh);
195:
1.2 djm 196: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 197: BN_clear_free(shared_secret);
198:
199: kex_finish(kex);
200: }
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