Annotation of src/usr.bin/ssh/kexecdhs.c, Revision 1.14
1.14 ! djm 1: /* $OpenBSD: kexecdhs.c,v 1.13 2015/01/20 07:55:33 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:
46: static int input_kex_ecdh_init(int, u_int32_t, void *);
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
57: input_kex_ecdh_init(int type, u_int32_t seq, void *ctxt)
58: {
59: struct ssh *ssh = ctxt;
60: struct kex *kex = ssh->kex;
1.1 djm 61: EC_POINT *client_public;
1.12 markus 62: EC_KEY *server_key = NULL;
1.1 djm 63: const EC_GROUP *group;
1.12 markus 64: const EC_POINT *public_key;
65: BIGNUM *shared_secret = NULL;
66: struct sshkey *server_host_private, *server_host_public;
1.1 djm 67: u_char *server_host_key_blob = NULL, *signature = NULL;
1.12 markus 68: u_char *kbuf = NULL;
69: u_char hash[SSH_DIGEST_MAX_LENGTH];
70: size_t slen, sbloblen;
71: size_t klen = 0, hashlen;
72: int r;
73:
74: if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) {
75: r = SSH_ERR_ALLOC_FAIL;
76: goto out;
77: }
78: if (EC_KEY_generate_key(server_key) != 1) {
79: r = SSH_ERR_LIBCRYPTO_ERROR;
80: goto out;
81: }
1.1 djm 82: group = EC_KEY_get0_group(server_key);
83:
84: #ifdef DEBUG_KEXECDH
85: fputs("server private key:\n", stderr);
1.12 markus 86: sshkey_dump_ec_key(server_key);
1.1 djm 87: #endif
88:
89: if (kex->load_host_public_key == NULL ||
1.12 markus 90: kex->load_host_private_key == NULL) {
91: r = SSH_ERR_INVALID_ARGUMENT;
92: goto out;
93: }
1.14 ! djm 94: server_host_public = kex->load_host_public_key(kex->hostkey_type,
! 95: kex->hostkey_nid, ssh);
! 96: server_host_private = kex->load_host_private_key(kex->hostkey_type,
! 97: kex->hostkey_nid, ssh);
1.13 djm 98: if (server_host_public == NULL) {
1.12 markus 99: r = SSH_ERR_NO_HOSTKEY_LOADED;
100: goto out;
101: }
102: if ((client_public = EC_POINT_new(group)) == NULL) {
103: r = SSH_ERR_ALLOC_FAIL;
104: goto out;
105: }
106: if ((r = sshpkt_get_ec(ssh, client_public, group)) != 0 ||
107: (r = sshpkt_get_end(ssh)) != 0)
108: goto out;
1.1 djm 109:
110: #ifdef DEBUG_KEXECDH
111: fputs("client public key:\n", stderr);
1.12 markus 112: sshkey_dump_ec_point(group, client_public);
1.1 djm 113: #endif
1.12 markus 114: if (sshkey_ec_validate_public(group, client_public) != 0) {
115: sshpkt_disconnect(ssh, "invalid client public key");
116: r = SSH_ERR_MESSAGE_INCOMPLETE;
117: goto out;
118: }
1.1 djm 119:
120: /* Calculate shared_secret */
121: klen = (EC_GROUP_get_degree(group) + 7) / 8;
1.12 markus 122: if ((kbuf = malloc(klen)) == NULL ||
123: (shared_secret = BN_new()) == NULL) {
124: r = SSH_ERR_ALLOC_FAIL;
125: goto out;
126: }
1.1 djm 127: if (ECDH_compute_key(kbuf, klen, client_public,
1.12 markus 128: server_key, NULL) != (int)klen ||
129: BN_bin2bn(kbuf, klen, shared_secret) == NULL) {
130: r = SSH_ERR_LIBCRYPTO_ERROR;
131: goto out;
132: }
1.1 djm 133:
1.12 markus 134: #ifdef DEBUG_KEXECDH
1.1 djm 135: dump_digest("shared secret", kbuf, klen);
136: #endif
137: /* calc H */
1.12 markus 138: if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
139: &sbloblen)) != 0)
140: goto out;
141: hashlen = sizeof(hash);
142: if ((r = kex_ecdh_hash(
1.8 djm 143: kex->hash_alg,
1.1 djm 144: group,
145: kex->client_version_string,
146: kex->server_version_string,
1.12 markus 147: sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
148: sshbuf_ptr(kex->my), sshbuf_len(kex->my),
1.1 djm 149: server_host_key_blob, sbloblen,
150: client_public,
151: EC_KEY_get0_public_key(server_key),
152: shared_secret,
1.12 markus 153: hash, &hashlen)) != 0)
154: goto out;
1.1 djm 155:
156: /* save session id := H */
157: if (kex->session_id == NULL) {
158: kex->session_id_len = hashlen;
1.12 markus 159: kex->session_id = malloc(kex->session_id_len);
160: if (kex->session_id == NULL) {
161: r = SSH_ERR_ALLOC_FAIL;
162: goto out;
163: }
1.1 djm 164: memcpy(kex->session_id, hash, kex->session_id_len);
165: }
166:
167: /* sign H */
1.12 markus 168: if ((r = kex->sign(server_host_private, server_host_public,
169: &signature, &slen, hash, hashlen, ssh->compat)) < 0)
170: goto out;
1.1 djm 171:
172: /* destroy_sensitive_data(); */
173:
1.12 markus 174: public_key = EC_KEY_get0_public_key(server_key);
1.1 djm 175: /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
1.12 markus 176: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
177: (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
178: (r = sshpkt_put_ec(ssh, public_key, group)) != 0 ||
179: (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
180: (r = sshpkt_send(ssh)) != 0)
181: goto out;
182:
183: if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
184: r = kex_send_newkeys(ssh);
185: out:
186: explicit_bzero(hash, sizeof(hash));
187: if (kex->ec_client_key) {
188: EC_KEY_free(kex->ec_client_key);
189: kex->ec_client_key = NULL;
190: }
191: if (server_key)
192: EC_KEY_free(server_key);
193: if (kbuf) {
194: explicit_bzero(kbuf, klen);
195: free(kbuf);
196: }
197: if (shared_secret)
198: BN_clear_free(shared_secret);
199: free(server_host_key_blob);
1.4 djm 200: free(signature);
1.12 markus 201: return r;
1.1 djm 202: }
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