Annotation of src/usr.bin/ssh/kexecdhc.c, Revision 1.2
1.2 ! djm 1: /* $OpenBSD: kexecdhc.c,v 1.1 2010/08/31 11:54:45 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:
29: #include <stdio.h>
30: #include <string.h>
31: #include <signal.h>
32:
33: #include <openssl/ecdh.h>
34:
35: #include "xmalloc.h"
36: #include "buffer.h"
37: #include "key.h"
38: #include "cipher.h"
39: #include "kex.h"
40: #include "log.h"
41: #include "packet.h"
42: #include "dh.h"
43: #include "ssh2.h"
44:
45: void
46: kexecdh_client(Kex *kex)
47: {
48: EC_KEY *client_key;
49: EC_POINT *server_public;
50: const EC_GROUP *group;
51: BIGNUM *shared_secret;
52: Key *server_host_key;
53: u_char *server_host_key_blob = NULL, *signature = NULL;
54: u_char *kbuf, *hash;
55: u_int klen, slen, sbloblen, hashlen;
56: int curve_nid;
57:
1.2 ! djm 58: if ((curve_nid = kex_ecdh_name_to_nid(kex->name)) == -1)
! 59: fatal("%s: unsupported ECDH curve \"%s\"", __func__, kex->name);
1.1 djm 60: if ((client_key = EC_KEY_new_by_curve_name(curve_nid)) == NULL)
61: fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
62: if (EC_KEY_generate_key(client_key) != 1)
63: fatal("%s: EC_KEY_generate_key failed", __func__);
64: group = EC_KEY_get0_group(client_key);
65:
66: packet_start(SSH2_MSG_KEX_ECDH_INIT);
67: packet_put_ecpoint(group, EC_KEY_get0_public_key(client_key));
68: packet_send();
69: debug("sending SSH2_MSG_KEX_ECDH_INIT");
70:
71: #ifdef DEBUG_KEXECDH
72: fputs("client private key:\n", stderr);
73: key_dump_ec_key(client_key);
74: #endif
75:
76: debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
77: packet_read_expect(SSH2_MSG_KEX_ECDH_REPLY);
78:
79: /* hostkey */
80: server_host_key_blob = packet_get_string(&sbloblen);
81: server_host_key = key_from_blob(server_host_key_blob, sbloblen);
82: if (server_host_key == NULL)
83: fatal("cannot decode server_host_key_blob");
84: if (server_host_key->type != kex->hostkey_type)
85: fatal("type mismatch for decoded server_host_key_blob");
86: if (kex->verify_host_key == NULL)
87: fatal("cannot verify server_host_key");
88: if (kex->verify_host_key(server_host_key) == -1)
89: fatal("server_host_key verification failed");
90:
91: /* Q_S, server public key */
92: if ((server_public = EC_POINT_new(group)) == NULL)
93: fatal("%s: EC_POINT_new failed", __func__);
94: packet_get_ecpoint(group, server_public);
95:
96: if (key_ec_validate_public(group, server_public) != 0)
97: fatal("%s: invalid server public key", __func__);
98:
99: #ifdef DEBUG_KEXECDH
100: fputs("server public key:\n", stderr);
101: key_dump_ec_point(group, server_public);
102: #endif
103:
104: /* signed H */
105: signature = packet_get_string(&slen);
106: packet_check_eom();
107:
108: klen = (EC_GROUP_get_degree(group) + 7) / 8;
109: kbuf = xmalloc(klen);
110: if (ECDH_compute_key(kbuf, klen, server_public,
111: client_key, NULL) != (int)klen)
112: fatal("%s: ECDH_compute_key failed", __func__);
113:
114: #ifdef DEBUG_KEXECDH
115: dump_digest("shared secret", kbuf, klen);
116: #endif
117: if ((shared_secret = BN_new()) == NULL)
118: fatal("%s: BN_new failed", __func__);
119: if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
120: fatal("%s: BN_bin2bn failed", __func__);
121: memset(kbuf, 0, klen);
122: xfree(kbuf);
123:
124: /* calc and verify H */
125: kex_ecdh_hash(
126: kex->evp_md,
127: group,
128: kex->client_version_string,
129: kex->server_version_string,
130: buffer_ptr(&kex->my), buffer_len(&kex->my),
131: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
132: server_host_key_blob, sbloblen,
133: EC_KEY_get0_public_key(client_key),
134: server_public,
135: shared_secret,
136: &hash, &hashlen
137: );
138: xfree(server_host_key_blob);
139: EC_POINT_clear_free(server_public);
140: EC_KEY_free(client_key);
141:
142: if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
143: fatal("key_verify failed for server_host_key");
144: key_free(server_host_key);
145: xfree(signature);
146:
147: /* save session id */
148: if (kex->session_id == NULL) {
149: kex->session_id_len = hashlen;
150: kex->session_id = xmalloc(kex->session_id_len);
151: memcpy(kex->session_id, hash, kex->session_id_len);
152: }
153:
154: kex_derive_keys(kex, hash, hashlen, shared_secret);
155: BN_clear_free(shared_secret);
156: kex_finish(kex);
157: }
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