Annotation of src/usr.bin/ssh/kexecdhs.c, Revision 1.6
1.6 ! markus 1: /* $OpenBSD: kexecdhs.c,v 1.5 2013/07/19 07:37:48 markus 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: #ifdef GSSAPI
42: #include "ssh-gss.h"
43: #endif
44:
45: void
46: kexecdh_server(Kex *kex)
47: {
48: EC_POINT *client_public;
49: EC_KEY *server_key;
50: const EC_GROUP *group;
51: BIGNUM *shared_secret;
52: Key *server_host_private, *server_host_public;
53: u_char *server_host_key_blob = NULL, *signature = NULL;
54: u_char *kbuf, *hash;
55: u_int klen, slen, sbloblen, hashlen;
56:
1.3 djm 57: if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL)
1.1 djm 58: fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
59: if (EC_KEY_generate_key(server_key) != 1)
60: fatal("%s: EC_KEY_generate_key failed", __func__);
61: group = EC_KEY_get0_group(server_key);
62:
63: #ifdef DEBUG_KEXECDH
64: fputs("server private key:\n", stderr);
65: key_dump_ec_key(server_key);
66: #endif
67:
68: if (kex->load_host_public_key == NULL ||
69: kex->load_host_private_key == NULL)
70: fatal("Cannot load hostkey");
71: server_host_public = kex->load_host_public_key(kex->hostkey_type);
72: if (server_host_public == NULL)
73: fatal("Unsupported hostkey type %d", kex->hostkey_type);
74: server_host_private = kex->load_host_private_key(kex->hostkey_type);
75:
76: debug("expecting SSH2_MSG_KEX_ECDH_INIT");
77: packet_read_expect(SSH2_MSG_KEX_ECDH_INIT);
78: if ((client_public = EC_POINT_new(group)) == NULL)
79: fatal("%s: EC_POINT_new failed", __func__);
80: packet_get_ecpoint(group, client_public);
81: packet_check_eom();
82:
83: if (key_ec_validate_public(group, client_public) != 0)
84: fatal("%s: invalid client public key", __func__);
85:
86: #ifdef DEBUG_KEXECDH
87: fputs("client public key:\n", stderr);
88: key_dump_ec_point(group, client_public);
89: #endif
90:
91: /* Calculate shared_secret */
92: klen = (EC_GROUP_get_degree(group) + 7) / 8;
93: kbuf = xmalloc(klen);
94: if (ECDH_compute_key(kbuf, klen, client_public,
95: server_key, NULL) != (int)klen)
96: fatal("%s: ECDH_compute_key failed", __func__);
97:
98: #ifdef DEBUG_KEXDH
99: dump_digest("shared secret", kbuf, klen);
100: #endif
101: if ((shared_secret = BN_new()) == NULL)
102: fatal("%s: BN_new failed", __func__);
103: if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
104: fatal("%s: BN_bin2bn failed", __func__);
105: memset(kbuf, 0, klen);
1.4 djm 106: free(kbuf);
1.1 djm 107:
108: /* calc H */
109: key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
110: kex_ecdh_hash(
111: kex->evp_md,
112: group,
113: kex->client_version_string,
114: kex->server_version_string,
115: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
116: buffer_ptr(&kex->my), buffer_len(&kex->my),
117: server_host_key_blob, sbloblen,
118: client_public,
119: EC_KEY_get0_public_key(server_key),
120: shared_secret,
121: &hash, &hashlen
122: );
123: EC_POINT_clear_free(client_public);
124:
125: /* save session id := H */
126: if (kex->session_id == NULL) {
127: kex->session_id_len = hashlen;
128: kex->session_id = xmalloc(kex->session_id_len);
129: memcpy(kex->session_id, hash, kex->session_id_len);
130: }
131:
132: /* sign H */
1.5 markus 133: kex->sign(server_host_private, server_host_public, &signature, &slen,
134: hash, hashlen);
1.1 djm 135:
136: /* destroy_sensitive_data(); */
137:
138: /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
139: packet_start(SSH2_MSG_KEX_ECDH_REPLY);
140: packet_put_string(server_host_key_blob, sbloblen);
141: packet_put_ecpoint(group, EC_KEY_get0_public_key(server_key));
142: packet_put_string(signature, slen);
143: packet_send();
144:
1.4 djm 145: free(signature);
146: free(server_host_key_blob);
1.1 djm 147: /* have keys, free server key */
148: EC_KEY_free(server_key);
149:
150: kex_derive_keys(kex, hash, hashlen, shared_secret);
151: BN_clear_free(shared_secret);
152: kex_finish(kex);
153: }