Annotation of src/usr.bin/ssh/kexdhc.c, Revision 1.21
1.21 ! djm 1: /* $OpenBSD: kexdhc.c,v 1.20 2017/05/30 14:23:52 markus Exp $ */
1.1 markus 2: /*
3: * Copyright (c) 2001 Markus Friedl. All rights reserved.
4: *
5: * Redistribution and use in source and binary forms, with or without
6: * modification, are permitted provided that the following conditions
7: * are met:
8: * 1. Redistributions of source code must retain the above copyright
9: * notice, this list of conditions and the following disclaimer.
10: * 2. Redistributions in binary form must reproduce the above copyright
11: * notice, this list of conditions and the following disclaimer in the
12: * documentation and/or other materials provided with the distribution.
13: *
14: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24: */
25:
1.9 deraadt 26: #include <sys/types.h>
1.12 djm 27:
28: #include <openssl/dh.h>
1.7 stevesk 29:
1.8 stevesk 30: #include <stdio.h>
1.7 stevesk 31: #include <string.h>
1.9 deraadt 32: #include <signal.h>
1.1 markus 33:
1.17 markus 34: #include "sshkey.h"
1.9 deraadt 35: #include "cipher.h"
1.17 markus 36: #include "digest.h"
1.1 markus 37: #include "kex.h"
38: #include "log.h"
39: #include "packet.h"
40: #include "dh.h"
41: #include "ssh2.h"
1.17 markus 42: #include "dispatch.h"
43: #include "compat.h"
44: #include "ssherr.h"
45: #include "sshbuf.h"
1.1 markus 46:
1.20 markus 47: static int input_kex_dh(int, u_int32_t, struct ssh *);
1.17 markus 48:
49: int
50: kexdh_client(struct ssh *ssh)
1.1 markus 51: {
1.17 markus 52: struct kex *kex = ssh->kex;
53: int r;
1.1 markus 54:
55: /* generate and send 'e', client DH public key */
1.2 djm 56: switch (kex->kex_type) {
57: case KEX_DH_GRP1_SHA1:
1.17 markus 58: kex->dh = dh_new_group1();
1.2 djm 59: break;
60: case KEX_DH_GRP14_SHA1:
1.19 djm 61: case KEX_DH_GRP14_SHA256:
1.17 markus 62: kex->dh = dh_new_group14();
1.2 djm 63: break;
1.19 djm 64: case KEX_DH_GRP16_SHA512:
65: kex->dh = dh_new_group16();
66: break;
67: case KEX_DH_GRP18_SHA512:
68: kex->dh = dh_new_group18();
69: break;
1.2 djm 70: default:
1.17 markus 71: r = SSH_ERR_INVALID_ARGUMENT;
72: goto out;
73: }
74: if (kex->dh == NULL) {
75: r = SSH_ERR_ALLOC_FAIL;
76: goto out;
1.2 djm 77: }
1.1 markus 78: debug("sending SSH2_MSG_KEXDH_INIT");
1.17 markus 79: if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 ||
80: (r = sshpkt_start(ssh, SSH2_MSG_KEXDH_INIT)) != 0 ||
81: (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||
82: (r = sshpkt_send(ssh)) != 0)
83: goto out;
1.1 markus 84: #ifdef DEBUG_KEXDH
1.17 markus 85: DHparams_print_fp(stderr, kex->dh);
1.1 markus 86: fprintf(stderr, "pub= ");
1.17 markus 87: BN_print_fp(stderr, kex->dh->pub_key);
1.1 markus 88: fprintf(stderr, "\n");
89: #endif
90: debug("expecting SSH2_MSG_KEXDH_REPLY");
1.17 markus 91: ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_REPLY, &input_kex_dh);
92: r = 0;
93: out:
94: return r;
95: }
1.1 markus 96:
1.17 markus 97: static int
1.20 markus 98: input_kex_dh(int type, u_int32_t seq, struct ssh *ssh)
1.17 markus 99: {
100: struct kex *kex = ssh->kex;
101: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
102: struct sshkey *server_host_key = NULL;
103: u_char *kbuf = NULL, *server_host_key_blob = NULL, *signature = NULL;
104: u_char hash[SSH_DIGEST_MAX_LENGTH];
105: size_t klen = 0, slen, sbloblen, hashlen;
106: int kout, r;
107:
108: if (kex->verify_host_key == NULL) {
109: r = SSH_ERR_INVALID_ARGUMENT;
110: goto out;
111: }
1.1 markus 112: /* key, cert */
1.17 markus 113: if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
114: &sbloblen)) != 0 ||
115: (r = sshkey_from_blob(server_host_key_blob, sbloblen,
116: &server_host_key)) != 0)
117: goto out;
1.18 djm 118: if (server_host_key->type != kex->hostkey_type ||
119: (kex->hostkey_type == KEY_ECDSA &&
120: server_host_key->ecdsa_nid != kex->hostkey_nid)) {
1.17 markus 121: r = SSH_ERR_KEY_TYPE_MISMATCH;
122: goto out;
123: }
124: if (kex->verify_host_key(server_host_key, ssh) == -1) {
125: r = SSH_ERR_SIGNATURE_INVALID;
126: goto out;
127: }
1.6 miod 128: /* DH parameter f, server public DH key */
1.17 markus 129: if ((dh_server_pub = BN_new()) == NULL) {
130: r = SSH_ERR_ALLOC_FAIL;
131: goto out;
132: }
133: /* signed H */
134: if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 ||
135: (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
136: (r = sshpkt_get_end(ssh)) != 0)
137: goto out;
1.1 markus 138: #ifdef DEBUG_KEXDH
139: fprintf(stderr, "dh_server_pub= ");
140: BN_print_fp(stderr, dh_server_pub);
141: fprintf(stderr, "\n");
142: debug("bits %d", BN_num_bits(dh_server_pub));
143: #endif
1.17 markus 144: if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
145: sshpkt_disconnect(ssh, "bad server public DH value");
146: r = SSH_ERR_MESSAGE_INCOMPLETE;
147: goto out;
148: }
1.1 markus 149:
1.17 markus 150: klen = DH_size(kex->dh);
151: if ((kbuf = malloc(klen)) == NULL ||
152: (shared_secret = BN_new()) == NULL) {
153: r = SSH_ERR_ALLOC_FAIL;
154: goto out;
155: }
156: if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
157: BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
158: r = SSH_ERR_LIBCRYPTO_ERROR;
159: goto out;
160: }
1.1 markus 161: #ifdef DEBUG_KEXDH
162: dump_digest("shared secret", kbuf, kout);
163: #endif
164:
165: /* calc and verify H */
1.17 markus 166: hashlen = sizeof(hash);
167: if ((r = kex_dh_hash(
1.19 djm 168: kex->hash_alg,
1.1 markus 169: kex->client_version_string,
170: kex->server_version_string,
1.17 markus 171: sshbuf_ptr(kex->my), sshbuf_len(kex->my),
172: sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
1.1 markus 173: server_host_key_blob, sbloblen,
1.17 markus 174: kex->dh->pub_key,
1.1 markus 175: dh_server_pub,
1.3 djm 176: shared_secret,
1.17 markus 177: hash, &hashlen)) != 0)
178: goto out;
1.1 markus 179:
1.17 markus 180: if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
1.21 ! djm 181: kex->hostkey_alg, ssh->compat)) != 0)
1.17 markus 182: goto out;
1.1 markus 183:
184: /* save session id */
185: if (kex->session_id == NULL) {
1.3 djm 186: kex->session_id_len = hashlen;
1.17 markus 187: kex->session_id = malloc(kex->session_id_len);
188: if (kex->session_id == NULL) {
189: r = SSH_ERR_ALLOC_FAIL;
190: goto out;
191: }
1.1 markus 192: memcpy(kex->session_id, hash, kex->session_id_len);
193: }
194:
1.17 markus 195: if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
196: r = kex_send_newkeys(ssh);
197: out:
198: explicit_bzero(hash, sizeof(hash));
199: DH_free(kex->dh);
200: kex->dh = NULL;
201: if (dh_server_pub)
202: BN_clear_free(dh_server_pub);
203: if (kbuf) {
204: explicit_bzero(kbuf, klen);
205: free(kbuf);
206: }
207: if (shared_secret)
208: BN_clear_free(shared_secret);
209: sshkey_free(server_host_key);
210: free(server_host_key_blob);
211: free(signature);
212: return r;
1.1 markus 213: }
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