Annotation of src/usr.bin/ssh/kexecdhs.c, Revision 1.21
1.21 ! djm 1: /* $OpenBSD: kexecdhs.c,v 1.20 2019/01/21 09:55:52 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:
1.12 markus 33: #include "sshkey.h"
1.1 djm 34: #include "cipher.h"
1.12 markus 35: #include "digest.h"
1.1 djm 36: #include "kex.h"
37: #include "log.h"
38: #include "packet.h"
39: #include "ssh2.h"
40:
1.12 markus 41: #include "dispatch.h"
42: #include "compat.h"
43: #include "ssherr.h"
44: #include "sshbuf.h"
45:
1.16 markus 46: static int input_kex_ecdh_init(int, u_int32_t, struct ssh *);
1.12 markus 47:
48: int
49: kexecdh_server(struct ssh *ssh)
1.1 djm 50: {
1.12 markus 51: debug("expecting SSH2_MSG_KEX_ECDH_INIT");
52: ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_ecdh_init);
53: return 0;
54: }
55:
56: static int
1.16 markus 57: input_kex_ecdh_init(int type, u_int32_t seq, struct ssh *ssh)
1.12 markus 58: {
59: struct kex *kex = ssh->kex;
1.1 djm 60: EC_POINT *client_public;
1.12 markus 61: EC_KEY *server_key = NULL;
1.1 djm 62: const EC_GROUP *group;
1.12 markus 63: const EC_POINT *public_key;
64: BIGNUM *shared_secret = NULL;
65: struct sshkey *server_host_private, *server_host_public;
1.1 djm 66: u_char *server_host_key_blob = NULL, *signature = NULL;
1.12 markus 67: u_char *kbuf = NULL;
68: u_char hash[SSH_DIGEST_MAX_LENGTH];
69: size_t slen, sbloblen;
70: size_t klen = 0, hashlen;
71: int r;
72:
73: if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) {
74: r = SSH_ERR_ALLOC_FAIL;
75: goto out;
76: }
77: if (EC_KEY_generate_key(server_key) != 1) {
78: r = SSH_ERR_LIBCRYPTO_ERROR;
79: goto out;
80: }
1.1 djm 81: group = EC_KEY_get0_group(server_key);
82:
83: #ifdef DEBUG_KEXECDH
84: fputs("server private key:\n", stderr);
1.12 markus 85: sshkey_dump_ec_key(server_key);
1.1 djm 86: #endif
87:
1.21 ! djm 88: if ((r = kex_load_hostkey(ssh, &server_host_private,
! 89: &server_host_public)) != 0)
1.12 markus 90: goto out;
91: if ((client_public = EC_POINT_new(group)) == NULL) {
92: r = SSH_ERR_ALLOC_FAIL;
93: goto out;
94: }
95: if ((r = sshpkt_get_ec(ssh, client_public, group)) != 0 ||
96: (r = sshpkt_get_end(ssh)) != 0)
97: goto out;
1.1 djm 98:
99: #ifdef DEBUG_KEXECDH
100: fputs("client public key:\n", stderr);
1.12 markus 101: sshkey_dump_ec_point(group, client_public);
1.1 djm 102: #endif
1.12 markus 103: if (sshkey_ec_validate_public(group, client_public) != 0) {
104: sshpkt_disconnect(ssh, "invalid client public key");
105: r = SSH_ERR_MESSAGE_INCOMPLETE;
106: goto out;
107: }
1.1 djm 108:
109: /* Calculate shared_secret */
110: klen = (EC_GROUP_get_degree(group) + 7) / 8;
1.12 markus 111: if ((kbuf = malloc(klen)) == NULL ||
112: (shared_secret = BN_new()) == NULL) {
113: r = SSH_ERR_ALLOC_FAIL;
114: goto out;
115: }
1.1 djm 116: if (ECDH_compute_key(kbuf, klen, client_public,
1.12 markus 117: server_key, NULL) != (int)klen ||
118: BN_bin2bn(kbuf, klen, shared_secret) == NULL) {
119: r = SSH_ERR_LIBCRYPTO_ERROR;
120: goto out;
121: }
1.1 djm 122:
1.12 markus 123: #ifdef DEBUG_KEXECDH
1.1 djm 124: dump_digest("shared secret", kbuf, klen);
125: #endif
126: /* calc H */
1.12 markus 127: if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
128: &sbloblen)) != 0)
129: goto out;
130: hashlen = sizeof(hash);
131: if ((r = kex_ecdh_hash(
1.8 djm 132: kex->hash_alg,
1.1 djm 133: group,
1.18 djm 134: kex->client_version,
135: kex->server_version,
1.12 markus 136: sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
137: sshbuf_ptr(kex->my), sshbuf_len(kex->my),
1.1 djm 138: server_host_key_blob, sbloblen,
139: client_public,
140: EC_KEY_get0_public_key(server_key),
141: shared_secret,
1.12 markus 142: hash, &hashlen)) != 0)
143: goto out;
1.1 djm 144:
145: /* sign H */
1.19 djm 146: if ((r = kex->sign(ssh, server_host_private, server_host_public,
147: &signature, &slen, hash, hashlen, kex->hostkey_alg)) < 0)
1.12 markus 148: goto out;
1.1 djm 149:
150: /* destroy_sensitive_data(); */
151:
1.12 markus 152: public_key = EC_KEY_get0_public_key(server_key);
1.1 djm 153: /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
1.12 markus 154: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
155: (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
156: (r = sshpkt_put_ec(ssh, public_key, group)) != 0 ||
157: (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
158: (r = sshpkt_send(ssh)) != 0)
159: goto out;
160:
161: if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
162: r = kex_send_newkeys(ssh);
163: out:
164: explicit_bzero(hash, sizeof(hash));
1.17 jsing 165: EC_KEY_free(kex->ec_client_key);
166: kex->ec_client_key = NULL;
167: EC_KEY_free(server_key);
1.12 markus 168: if (kbuf) {
169: explicit_bzero(kbuf, klen);
170: free(kbuf);
171: }
1.17 jsing 172: BN_clear_free(shared_secret);
1.12 markus 173: free(server_host_key_blob);
1.4 djm 174: free(signature);
1.12 markus 175: return r;
1.1 djm 176: }
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