Annotation of src/usr.bin/ssh/kexdhs.c, Revision 1.12
1.12 ! djm 1: /* $OpenBSD: kexdhs.c,v 1.11 2010/02/26 20:29:54 djm 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:
1.6 stevesk 26:
1.7 deraadt 27: #include <sys/types.h>
1.6 stevesk 28: #include <string.h>
1.7 deraadt 29: #include <signal.h>
1.12 ! djm 30:
! 31: #include <openssl/dh.h>
1.1 markus 32:
33: #include "xmalloc.h"
1.7 deraadt 34: #include "buffer.h"
1.1 markus 35: #include "key.h"
1.7 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"
1.7 deraadt 42: #ifdef GSSAPI
43: #include "ssh-gss.h"
44: #endif
1.1 markus 45: #include "monitor_wrap.h"
46:
47: void
48: kexdh_server(Kex *kex)
49: {
50: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
51: DH *dh;
1.11 djm 52: Key *server_host_public, *server_host_private;
1.1 markus 53: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
1.8 markus 54: u_int sbloblen, klen, hashlen, slen;
55: int kout;
1.1 markus 56:
57: /* generate server DH public key */
1.2 djm 58: switch (kex->kex_type) {
59: case KEX_DH_GRP1_SHA1:
60: dh = dh_new_group1();
61: break;
62: case KEX_DH_GRP14_SHA1:
63: dh = dh_new_group14();
64: break;
65: default:
66: fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
67: }
1.1 markus 68: dh_gen_key(dh, kex->we_need * 8);
69:
70: debug("expecting SSH2_MSG_KEXDH_INIT");
71: packet_read_expect(SSH2_MSG_KEXDH_INIT);
72:
1.11 djm 73: if (kex->load_host_public_key == NULL ||
74: kex->load_host_private_key == NULL)
1.1 markus 75: fatal("Cannot load hostkey");
1.11 djm 76: server_host_public = kex->load_host_public_key(kex->hostkey_type);
77: if (server_host_public == NULL)
1.1 markus 78: fatal("Unsupported hostkey type %d", kex->hostkey_type);
1.11 djm 79: server_host_private = kex->load_host_private_key(kex->hostkey_type);
80: if (server_host_private == NULL)
81: fatal("Missing private key for hostkey type %d",
82: kex->hostkey_type);
1.1 markus 83:
84: /* key, cert */
85: if ((dh_client_pub = BN_new()) == NULL)
86: fatal("dh_client_pub == NULL");
87: packet_get_bignum2(dh_client_pub);
88: packet_check_eom();
89:
90: #ifdef DEBUG_KEXDH
91: fprintf(stderr, "dh_client_pub= ");
92: BN_print_fp(stderr, dh_client_pub);
93: fprintf(stderr, "\n");
94: debug("bits %d", BN_num_bits(dh_client_pub));
95: #endif
96:
97: #ifdef DEBUG_KEXDH
98: DHparams_print_fp(stderr, dh);
99: fprintf(stderr, "pub= ");
100: BN_print_fp(stderr, dh->pub_key);
101: fprintf(stderr, "\n");
102: #endif
103: if (!dh_pub_is_valid(dh, dh_client_pub))
104: packet_disconnect("bad client public DH value");
105:
106: klen = DH_size(dh);
107: kbuf = xmalloc(klen);
1.8 markus 108: if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
109: fatal("DH_compute_key: failed");
1.1 markus 110: #ifdef DEBUG_KEXDH
111: dump_digest("shared secret", kbuf, kout);
112: #endif
113: if ((shared_secret = BN_new()) == NULL)
114: fatal("kexdh_server: BN_new failed");
1.9 markus 115: if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
116: fatal("kexdh_server: BN_bin2bn failed");
1.1 markus 117: memset(kbuf, 0, klen);
118: xfree(kbuf);
119:
1.11 djm 120: key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
1.1 markus 121:
122: /* calc H */
1.3 djm 123: kex_dh_hash(
1.1 markus 124: kex->client_version_string,
125: kex->server_version_string,
126: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
127: buffer_ptr(&kex->my), buffer_len(&kex->my),
128: server_host_key_blob, sbloblen,
129: dh_client_pub,
130: dh->pub_key,
1.3 djm 131: shared_secret,
132: &hash, &hashlen
1.1 markus 133: );
134: BN_clear_free(dh_client_pub);
135:
136: /* save session id := H */
137: if (kex->session_id == NULL) {
1.3 djm 138: kex->session_id_len = hashlen;
1.1 markus 139: kex->session_id = xmalloc(kex->session_id_len);
140: memcpy(kex->session_id, hash, kex->session_id_len);
141: }
142:
143: /* sign H */
1.11 djm 144: if (PRIVSEP(key_sign(server_host_private, &signature, &slen, hash,
1.10 dtucker 145: hashlen)) < 0)
146: fatal("kexdh_server: key_sign failed");
1.1 markus 147:
148: /* destroy_sensitive_data(); */
149:
150: /* send server hostkey, DH pubkey 'f' and singed H */
151: packet_start(SSH2_MSG_KEXDH_REPLY);
152: packet_put_string(server_host_key_blob, sbloblen);
153: packet_put_bignum2(dh->pub_key); /* f */
154: packet_put_string(signature, slen);
155: packet_send();
156:
157: xfree(signature);
158: xfree(server_host_key_blob);
159: /* have keys, free DH */
160: DH_free(dh);
161:
1.3 djm 162: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 163: BN_clear_free(shared_secret);
164: kex_finish(kex);
165: }
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