Annotation of src/usr.bin/ssh/kexecdhs.c, Revision 1.3
1.3 ! djm 1: /* $OpenBSD: kexecdhs.c,v 1.2 2010/09/22 05:01:29 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 "dh.h"
41: #include "ssh2.h"
42: #ifdef GSSAPI
43: #include "ssh-gss.h"
44: #endif
45: #include "monitor_wrap.h"
46:
47: void
48: kexecdh_server(Kex *kex)
49: {
50: EC_POINT *client_public;
51: EC_KEY *server_key;
52: const EC_GROUP *group;
53: BIGNUM *shared_secret;
54: Key *server_host_private, *server_host_public;
55: u_char *server_host_key_blob = NULL, *signature = NULL;
56: u_char *kbuf, *hash;
57: u_int klen, slen, sbloblen, hashlen;
58:
1.3 ! djm 59: if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL)
1.1 djm 60: fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
61: if (EC_KEY_generate_key(server_key) != 1)
62: fatal("%s: EC_KEY_generate_key failed", __func__);
63: group = EC_KEY_get0_group(server_key);
64:
65: #ifdef DEBUG_KEXECDH
66: fputs("server private key:\n", stderr);
67: key_dump_ec_key(server_key);
68: #endif
69:
70: if (kex->load_host_public_key == NULL ||
71: kex->load_host_private_key == NULL)
72: fatal("Cannot load hostkey");
73: server_host_public = kex->load_host_public_key(kex->hostkey_type);
74: if (server_host_public == NULL)
75: fatal("Unsupported hostkey type %d", kex->hostkey_type);
76: server_host_private = kex->load_host_private_key(kex->hostkey_type);
77: if (server_host_private == NULL)
78: fatal("Missing private key for hostkey type %d",
79: kex->hostkey_type);
80:
81: debug("expecting SSH2_MSG_KEX_ECDH_INIT");
82: packet_read_expect(SSH2_MSG_KEX_ECDH_INIT);
83: if ((client_public = EC_POINT_new(group)) == NULL)
84: fatal("%s: EC_POINT_new failed", __func__);
85: packet_get_ecpoint(group, client_public);
86: packet_check_eom();
87:
88: if (key_ec_validate_public(group, client_public) != 0)
89: fatal("%s: invalid client public key", __func__);
90:
91: #ifdef DEBUG_KEXECDH
92: fputs("client public key:\n", stderr);
93: key_dump_ec_point(group, client_public);
94: #endif
95:
96: /* Calculate shared_secret */
97: klen = (EC_GROUP_get_degree(group) + 7) / 8;
98: kbuf = xmalloc(klen);
99: if (ECDH_compute_key(kbuf, klen, client_public,
100: server_key, NULL) != (int)klen)
101: fatal("%s: ECDH_compute_key failed", __func__);
102:
103: #ifdef DEBUG_KEXDH
104: dump_digest("shared secret", kbuf, klen);
105: #endif
106: if ((shared_secret = BN_new()) == NULL)
107: fatal("%s: BN_new failed", __func__);
108: if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
109: fatal("%s: BN_bin2bn failed", __func__);
110: memset(kbuf, 0, klen);
111: xfree(kbuf);
112:
113: /* calc H */
114: key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
115: kex_ecdh_hash(
116: kex->evp_md,
117: group,
118: kex->client_version_string,
119: kex->server_version_string,
120: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
121: buffer_ptr(&kex->my), buffer_len(&kex->my),
122: server_host_key_blob, sbloblen,
123: client_public,
124: EC_KEY_get0_public_key(server_key),
125: shared_secret,
126: &hash, &hashlen
127: );
128: EC_POINT_clear_free(client_public);
129:
130: /* save session id := H */
131: if (kex->session_id == NULL) {
132: kex->session_id_len = hashlen;
133: kex->session_id = xmalloc(kex->session_id_len);
134: memcpy(kex->session_id, hash, kex->session_id_len);
135: }
136:
137: /* sign H */
138: if (PRIVSEP(key_sign(server_host_private, &signature, &slen,
139: hash, hashlen)) < 0)
140: fatal("kexdh_server: key_sign failed");
141:
142: /* destroy_sensitive_data(); */
143:
144: /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
145: packet_start(SSH2_MSG_KEX_ECDH_REPLY);
146: packet_put_string(server_host_key_blob, sbloblen);
147: packet_put_ecpoint(group, EC_KEY_get0_public_key(server_key));
148: packet_put_string(signature, slen);
149: packet_send();
150:
151: xfree(signature);
152: xfree(server_host_key_blob);
153: /* have keys, free server key */
154: EC_KEY_free(server_key);
155:
156: kex_derive_keys(kex, hash, hashlen, shared_secret);
157: BN_clear_free(shared_secret);
158: kex_finish(kex);
159: }
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