Annotation of src/usr.bin/ssh/kexecdhs.c, Revision 1.9
1.9 ! djm 1: /* $OpenBSD: kexecdhs.c,v 1.8 2014/01/09 23:20:00 djm Exp $ */
1.1 djm 2: /*
3: * Copyright (c) 2001 Markus Friedl. All rights reserved.
4: * Copyright (c) 2010 Damien Miller. 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:
27: #include <sys/types.h>
28: #include <string.h>
29: #include <signal.h>
30:
31: #include <openssl/ecdh.h>
32:
33: #include "xmalloc.h"
34: #include "buffer.h"
35: #include "key.h"
36: #include "cipher.h"
37: #include "kex.h"
38: #include "log.h"
39: #include "packet.h"
40: #include "ssh2.h"
41:
42: void
43: kexecdh_server(Kex *kex)
44: {
45: EC_POINT *client_public;
46: EC_KEY *server_key;
47: const EC_GROUP *group;
48: BIGNUM *shared_secret;
49: Key *server_host_private, *server_host_public;
50: u_char *server_host_key_blob = NULL, *signature = NULL;
51: u_char *kbuf, *hash;
52: u_int klen, slen, sbloblen, hashlen;
53:
1.3 djm 54: if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL)
1.1 djm 55: fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
56: if (EC_KEY_generate_key(server_key) != 1)
57: fatal("%s: EC_KEY_generate_key failed", __func__);
58: group = EC_KEY_get0_group(server_key);
59:
60: #ifdef DEBUG_KEXECDH
61: fputs("server private key:\n", stderr);
62: key_dump_ec_key(server_key);
63: #endif
64:
65: if (kex->load_host_public_key == NULL ||
66: kex->load_host_private_key == NULL)
67: fatal("Cannot load hostkey");
68: server_host_public = kex->load_host_public_key(kex->hostkey_type);
69: if (server_host_public == NULL)
70: fatal("Unsupported hostkey type %d", kex->hostkey_type);
71: server_host_private = kex->load_host_private_key(kex->hostkey_type);
72:
73: debug("expecting SSH2_MSG_KEX_ECDH_INIT");
74: packet_read_expect(SSH2_MSG_KEX_ECDH_INIT);
75: if ((client_public = EC_POINT_new(group)) == NULL)
76: fatal("%s: EC_POINT_new failed", __func__);
77: packet_get_ecpoint(group, client_public);
78: packet_check_eom();
79:
80: if (key_ec_validate_public(group, client_public) != 0)
81: fatal("%s: invalid client public key", __func__);
82:
83: #ifdef DEBUG_KEXECDH
84: fputs("client public key:\n", stderr);
85: key_dump_ec_point(group, client_public);
86: #endif
87:
88: /* Calculate shared_secret */
89: klen = (EC_GROUP_get_degree(group) + 7) / 8;
90: kbuf = xmalloc(klen);
91: if (ECDH_compute_key(kbuf, klen, client_public,
92: server_key, NULL) != (int)klen)
93: fatal("%s: ECDH_compute_key failed", __func__);
94:
95: #ifdef DEBUG_KEXDH
96: dump_digest("shared secret", kbuf, klen);
97: #endif
98: if ((shared_secret = BN_new()) == NULL)
99: fatal("%s: BN_new failed", __func__);
100: if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
101: fatal("%s: BN_bin2bn failed", __func__);
102: memset(kbuf, 0, klen);
1.4 djm 103: free(kbuf);
1.1 djm 104:
105: /* calc H */
106: key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
107: kex_ecdh_hash(
1.8 djm 108: kex->hash_alg,
1.1 djm 109: group,
110: kex->client_version_string,
111: kex->server_version_string,
112: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
113: buffer_ptr(&kex->my), buffer_len(&kex->my),
114: server_host_key_blob, sbloblen,
115: client_public,
116: EC_KEY_get0_public_key(server_key),
117: shared_secret,
118: &hash, &hashlen
119: );
120: EC_POINT_clear_free(client_public);
121:
122: /* save session id := H */
123: if (kex->session_id == NULL) {
124: kex->session_id_len = hashlen;
125: kex->session_id = xmalloc(kex->session_id_len);
126: memcpy(kex->session_id, hash, kex->session_id_len);
127: }
128:
129: /* sign H */
1.5 markus 130: kex->sign(server_host_private, server_host_public, &signature, &slen,
131: hash, hashlen);
1.1 djm 132:
133: /* destroy_sensitive_data(); */
134:
135: /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
136: packet_start(SSH2_MSG_KEX_ECDH_REPLY);
137: packet_put_string(server_host_key_blob, sbloblen);
138: packet_put_ecpoint(group, EC_KEY_get0_public_key(server_key));
139: packet_put_string(signature, slen);
140: packet_send();
141:
1.4 djm 142: free(signature);
143: free(server_host_key_blob);
1.1 djm 144: /* have keys, free server key */
145: EC_KEY_free(server_key);
146:
1.9 ! djm 147: kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
1.1 djm 148: BN_clear_free(shared_secret);
149: kex_finish(kex);
150: }
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