Annotation of src/usr.bin/ssh/kexdhs.c, Revision 1.18
1.18 ! djm 1: /* $OpenBSD: kexdhs.c,v 1.17 2014/01/12 08:13:13 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"
42:
43: void
44: kexdh_server(Kex *kex)
45: {
46: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
47: DH *dh;
1.11 djm 48: Key *server_host_public, *server_host_private;
1.1 markus 49: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
1.8 markus 50: u_int sbloblen, klen, hashlen, slen;
51: int kout;
1.1 markus 52:
53: /* generate server DH public key */
1.2 djm 54: switch (kex->kex_type) {
55: case KEX_DH_GRP1_SHA1:
56: dh = dh_new_group1();
57: break;
58: case KEX_DH_GRP14_SHA1:
59: dh = dh_new_group14();
60: break;
61: default:
62: fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
63: }
1.1 markus 64: dh_gen_key(dh, kex->we_need * 8);
65:
66: debug("expecting SSH2_MSG_KEXDH_INIT");
67: packet_read_expect(SSH2_MSG_KEXDH_INIT);
68:
1.11 djm 69: if (kex->load_host_public_key == NULL ||
70: kex->load_host_private_key == NULL)
1.1 markus 71: fatal("Cannot load hostkey");
1.11 djm 72: server_host_public = kex->load_host_public_key(kex->hostkey_type);
73: if (server_host_public == NULL)
1.1 markus 74: fatal("Unsupported hostkey type %d", kex->hostkey_type);
1.11 djm 75: server_host_private = kex->load_host_private_key(kex->hostkey_type);
1.1 markus 76:
77: /* key, cert */
78: if ((dh_client_pub = BN_new()) == NULL)
79: fatal("dh_client_pub == NULL");
80: packet_get_bignum2(dh_client_pub);
81: packet_check_eom();
82:
83: #ifdef DEBUG_KEXDH
84: fprintf(stderr, "dh_client_pub= ");
85: BN_print_fp(stderr, dh_client_pub);
86: fprintf(stderr, "\n");
87: debug("bits %d", BN_num_bits(dh_client_pub));
88: #endif
89:
90: #ifdef DEBUG_KEXDH
91: DHparams_print_fp(stderr, dh);
92: fprintf(stderr, "pub= ");
93: BN_print_fp(stderr, dh->pub_key);
94: fprintf(stderr, "\n");
95: #endif
96: if (!dh_pub_is_valid(dh, dh_client_pub))
97: packet_disconnect("bad client public DH value");
98:
99: klen = DH_size(dh);
100: kbuf = xmalloc(klen);
1.8 markus 101: if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
102: fatal("DH_compute_key: failed");
1.1 markus 103: #ifdef DEBUG_KEXDH
104: dump_digest("shared secret", kbuf, kout);
105: #endif
106: if ((shared_secret = BN_new()) == NULL)
107: fatal("kexdh_server: BN_new failed");
1.9 markus 108: if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
109: fatal("kexdh_server: BN_bin2bn failed");
1.18 ! djm 110: explicit_bzero(kbuf, klen);
1.13 djm 111: free(kbuf);
1.1 markus 112:
1.11 djm 113: key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
1.1 markus 114:
115: /* calc H */
1.3 djm 116: kex_dh_hash(
1.1 markus 117: kex->client_version_string,
118: kex->server_version_string,
119: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
120: buffer_ptr(&kex->my), buffer_len(&kex->my),
121: server_host_key_blob, sbloblen,
122: dh_client_pub,
123: dh->pub_key,
1.3 djm 124: shared_secret,
125: &hash, &hashlen
1.1 markus 126: );
127: BN_clear_free(dh_client_pub);
128:
129: /* save session id := H */
130: if (kex->session_id == NULL) {
1.3 djm 131: kex->session_id_len = hashlen;
1.1 markus 132: kex->session_id = xmalloc(kex->session_id_len);
133: memcpy(kex->session_id, hash, kex->session_id_len);
134: }
135:
136: /* sign H */
1.14 markus 137: kex->sign(server_host_private, server_host_public, &signature, &slen,
138: hash, hashlen);
1.1 markus 139:
140: /* destroy_sensitive_data(); */
141:
142: /* send server hostkey, DH pubkey 'f' and singed H */
143: packet_start(SSH2_MSG_KEXDH_REPLY);
144: packet_put_string(server_host_key_blob, sbloblen);
145: packet_put_bignum2(dh->pub_key); /* f */
146: packet_put_string(signature, slen);
147: packet_send();
148:
1.13 djm 149: free(signature);
150: free(server_host_key_blob);
1.1 markus 151: /* have keys, free DH */
152: DH_free(dh);
153:
1.17 djm 154: kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
1.1 markus 155: BN_clear_free(shared_secret);
156: kex_finish(kex);
157: }
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