Annotation of src/usr.bin/ssh/kexdhc.c, Revision 1.7
1.7 ! stevesk 1: /* $OpenBSD: kexdhc.c,v 1.6 2006/05/18 21:27:25 miod 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:
! 28: #include <string.h>
1.1 markus 29:
30: #include "xmalloc.h"
31: #include "key.h"
32: #include "kex.h"
33: #include "log.h"
34: #include "packet.h"
35: #include "dh.h"
36: #include "ssh2.h"
37:
38: void
39: kexdh_client(Kex *kex)
40: {
41: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
42: DH *dh;
43: Key *server_host_key;
44: u_char *server_host_key_blob = NULL, *signature = NULL;
45: u_char *kbuf, *hash;
1.3 djm 46: u_int klen, kout, slen, sbloblen, hashlen;
1.1 markus 47:
48: /* generate and send 'e', client DH public key */
1.2 djm 49: switch (kex->kex_type) {
50: case KEX_DH_GRP1_SHA1:
51: dh = dh_new_group1();
52: break;
53: case KEX_DH_GRP14_SHA1:
54: dh = dh_new_group14();
55: break;
56: default:
57: fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
58: }
1.1 markus 59: dh_gen_key(dh, kex->we_need * 8);
60: packet_start(SSH2_MSG_KEXDH_INIT);
61: packet_put_bignum2(dh->pub_key);
62: packet_send();
63:
64: debug("sending SSH2_MSG_KEXDH_INIT");
65: #ifdef DEBUG_KEXDH
66: DHparams_print_fp(stderr, dh);
67: fprintf(stderr, "pub= ");
68: BN_print_fp(stderr, dh->pub_key);
69: fprintf(stderr, "\n");
70: #endif
71:
72: debug("expecting SSH2_MSG_KEXDH_REPLY");
73: packet_read_expect(SSH2_MSG_KEXDH_REPLY);
74:
75: /* key, cert */
76: server_host_key_blob = packet_get_string(&sbloblen);
77: server_host_key = key_from_blob(server_host_key_blob, sbloblen);
78: if (server_host_key == NULL)
79: fatal("cannot decode server_host_key_blob");
80: if (server_host_key->type != kex->hostkey_type)
81: fatal("type mismatch for decoded server_host_key_blob");
82: if (kex->verify_host_key == NULL)
83: fatal("cannot verify server_host_key");
84: if (kex->verify_host_key(server_host_key) == -1)
85: fatal("server_host_key verification failed");
86:
1.6 miod 87: /* DH parameter f, server public DH key */
1.1 markus 88: if ((dh_server_pub = BN_new()) == NULL)
89: fatal("dh_server_pub == NULL");
90: packet_get_bignum2(dh_server_pub);
91:
92: #ifdef DEBUG_KEXDH
93: fprintf(stderr, "dh_server_pub= ");
94: BN_print_fp(stderr, dh_server_pub);
95: fprintf(stderr, "\n");
96: debug("bits %d", BN_num_bits(dh_server_pub));
97: #endif
98:
99: /* signed H */
100: signature = packet_get_string(&slen);
101: packet_check_eom();
102:
103: if (!dh_pub_is_valid(dh, dh_server_pub))
104: packet_disconnect("bad server public DH value");
105:
106: klen = DH_size(dh);
107: kbuf = xmalloc(klen);
108: kout = DH_compute_key(kbuf, dh_server_pub, dh);
109: #ifdef DEBUG_KEXDH
110: dump_digest("shared secret", kbuf, kout);
111: #endif
112: if ((shared_secret = BN_new()) == NULL)
113: fatal("kexdh_client: BN_new failed");
114: BN_bin2bn(kbuf, kout, shared_secret);
115: memset(kbuf, 0, klen);
116: xfree(kbuf);
117:
118: /* calc and verify H */
1.3 djm 119: kex_dh_hash(
1.1 markus 120: kex->client_version_string,
121: kex->server_version_string,
122: buffer_ptr(&kex->my), buffer_len(&kex->my),
123: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
124: server_host_key_blob, sbloblen,
125: dh->pub_key,
126: dh_server_pub,
1.3 djm 127: shared_secret,
128: &hash, &hashlen
1.1 markus 129: );
130: xfree(server_host_key_blob);
131: BN_clear_free(dh_server_pub);
132: DH_free(dh);
133:
1.3 djm 134: if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
1.1 markus 135: fatal("key_verify failed for server_host_key");
136: key_free(server_host_key);
137: xfree(signature);
138:
139: /* save session id */
140: if (kex->session_id == NULL) {
1.3 djm 141: kex->session_id_len = hashlen;
1.1 markus 142: kex->session_id = xmalloc(kex->session_id_len);
143: memcpy(kex->session_id, hash, kex->session_id_len);
144: }
145:
1.3 djm 146: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 147: BN_clear_free(shared_secret);
148: kex_finish(kex);
149: }
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