Annotation of src/usr.bin/ssh/kexdhc.c, Revision 1.8
1.8 ! stevesk 1: /* $OpenBSD: kexdhc.c,v 1.7 2006/07/22 20:48:23 stevesk Exp $ */
1.1 markus 2: /*
3: * Copyright (c) 2001 Markus Friedl. All rights reserved.
4: *
5: * Redistribution and use in source and binary forms, with or without
6: * modification, are permitted provided that the following conditions
7: * are met:
8: * 1. Redistributions of source code must retain the above copyright
9: * notice, this list of conditions and the following disclaimer.
10: * 2. Redistributions in binary form must reproduce the above copyright
11: * notice, this list of conditions and the following disclaimer in the
12: * documentation and/or other materials provided with the distribution.
13: *
14: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24: */
25:
26: #include "includes.h"
1.7 stevesk 27:
1.8 ! stevesk 28: #include <stdio.h>
1.7 stevesk 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:
39: void
40: kexdh_client(Kex *kex)
41: {
42: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
43: DH *dh;
44: Key *server_host_key;
45: u_char *server_host_key_blob = NULL, *signature = NULL;
46: u_char *kbuf, *hash;
1.3 djm 47: u_int klen, kout, slen, sbloblen, hashlen;
1.1 markus 48:
49: /* generate and send 'e', client DH public key */
1.2 djm 50: switch (kex->kex_type) {
51: case KEX_DH_GRP1_SHA1:
52: dh = dh_new_group1();
53: break;
54: case KEX_DH_GRP14_SHA1:
55: dh = dh_new_group14();
56: break;
57: default:
58: fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
59: }
1.1 markus 60: dh_gen_key(dh, kex->we_need * 8);
61: packet_start(SSH2_MSG_KEXDH_INIT);
62: packet_put_bignum2(dh->pub_key);
63: packet_send();
64:
65: debug("sending SSH2_MSG_KEXDH_INIT");
66: #ifdef DEBUG_KEXDH
67: DHparams_print_fp(stderr, dh);
68: fprintf(stderr, "pub= ");
69: BN_print_fp(stderr, dh->pub_key);
70: fprintf(stderr, "\n");
71: #endif
72:
73: debug("expecting SSH2_MSG_KEXDH_REPLY");
74: packet_read_expect(SSH2_MSG_KEXDH_REPLY);
75:
76: /* key, cert */
77: server_host_key_blob = packet_get_string(&sbloblen);
78: server_host_key = key_from_blob(server_host_key_blob, sbloblen);
79: if (server_host_key == NULL)
80: fatal("cannot decode server_host_key_blob");
81: if (server_host_key->type != kex->hostkey_type)
82: fatal("type mismatch for decoded server_host_key_blob");
83: if (kex->verify_host_key == NULL)
84: fatal("cannot verify server_host_key");
85: if (kex->verify_host_key(server_host_key) == -1)
86: fatal("server_host_key verification failed");
87:
1.6 miod 88: /* DH parameter f, server public DH key */
1.1 markus 89: if ((dh_server_pub = BN_new()) == NULL)
90: fatal("dh_server_pub == NULL");
91: packet_get_bignum2(dh_server_pub);
92:
93: #ifdef DEBUG_KEXDH
94: fprintf(stderr, "dh_server_pub= ");
95: BN_print_fp(stderr, dh_server_pub);
96: fprintf(stderr, "\n");
97: debug("bits %d", BN_num_bits(dh_server_pub));
98: #endif
99:
100: /* signed H */
101: signature = packet_get_string(&slen);
102: packet_check_eom();
103:
104: if (!dh_pub_is_valid(dh, dh_server_pub))
105: packet_disconnect("bad server public DH value");
106:
107: klen = DH_size(dh);
108: kbuf = xmalloc(klen);
109: kout = DH_compute_key(kbuf, dh_server_pub, dh);
110: #ifdef DEBUG_KEXDH
111: dump_digest("shared secret", kbuf, kout);
112: #endif
113: if ((shared_secret = BN_new()) == NULL)
114: fatal("kexdh_client: BN_new failed");
115: BN_bin2bn(kbuf, kout, shared_secret);
116: memset(kbuf, 0, klen);
117: xfree(kbuf);
118:
119: /* calc and verify H */
1.3 djm 120: kex_dh_hash(
1.1 markus 121: kex->client_version_string,
122: kex->server_version_string,
123: buffer_ptr(&kex->my), buffer_len(&kex->my),
124: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
125: server_host_key_blob, sbloblen,
126: dh->pub_key,
127: dh_server_pub,
1.3 djm 128: shared_secret,
129: &hash, &hashlen
1.1 markus 130: );
131: xfree(server_host_key_blob);
132: BN_clear_free(dh_server_pub);
133: DH_free(dh);
134:
1.3 djm 135: if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
1.1 markus 136: fatal("key_verify failed for server_host_key");
137: key_free(server_host_key);
138: xfree(signature);
139:
140: /* save session id */
141: if (kex->session_id == NULL) {
1.3 djm 142: kex->session_id_len = hashlen;
1.1 markus 143: kex->session_id = xmalloc(kex->session_id_len);
144: memcpy(kex->session_id, hash, kex->session_id_len);
145: }
146:
1.3 djm 147: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 148: BN_clear_free(shared_secret);
149: kex_finish(kex);
150: }