Annotation of src/usr.bin/ssh/kexdhc.c, Revision 1.23
1.23 ! djm 1: /* $OpenBSD: kexdhc.c,v 1.22 2018/02/07 02:06:51 jsing 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;
1.23 ! djm 54: const BIGNUM *pub_key;
1.1 markus 55:
56: /* generate and send 'e', client DH public key */
1.2 djm 57: switch (kex->kex_type) {
58: case KEX_DH_GRP1_SHA1:
1.17 markus 59: kex->dh = dh_new_group1();
1.2 djm 60: break;
61: case KEX_DH_GRP14_SHA1:
1.19 djm 62: case KEX_DH_GRP14_SHA256:
1.17 markus 63: kex->dh = dh_new_group14();
1.2 djm 64: break;
1.19 djm 65: case KEX_DH_GRP16_SHA512:
66: kex->dh = dh_new_group16();
67: break;
68: case KEX_DH_GRP18_SHA512:
69: kex->dh = dh_new_group18();
70: break;
1.2 djm 71: default:
1.17 markus 72: r = SSH_ERR_INVALID_ARGUMENT;
73: goto out;
74: }
75: if (kex->dh == NULL) {
76: r = SSH_ERR_ALLOC_FAIL;
77: goto out;
1.2 djm 78: }
1.1 markus 79: debug("sending SSH2_MSG_KEXDH_INIT");
1.23 ! djm 80: if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
! 81: goto out;
! 82: DH_get0_key(kex->dh, &pub_key, NULL);
! 83: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXDH_INIT)) != 0 ||
! 84: (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 ||
1.17 markus 85: (r = sshpkt_send(ssh)) != 0)
86: goto out;
1.1 markus 87: #ifdef DEBUG_KEXDH
1.17 markus 88: DHparams_print_fp(stderr, kex->dh);
1.1 markus 89: fprintf(stderr, "pub= ");
1.23 ! djm 90: BN_print_fp(stderr, pub_key);
1.1 markus 91: fprintf(stderr, "\n");
92: #endif
93: debug("expecting SSH2_MSG_KEXDH_REPLY");
1.17 markus 94: ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_REPLY, &input_kex_dh);
95: r = 0;
96: out:
97: return r;
98: }
1.1 markus 99:
1.17 markus 100: static int
1.20 markus 101: input_kex_dh(int type, u_int32_t seq, struct ssh *ssh)
1.17 markus 102: {
103: struct kex *kex = ssh->kex;
104: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
1.23 ! djm 105: const BIGNUM *pub_key;
1.17 markus 106: struct sshkey *server_host_key = NULL;
107: u_char *kbuf = NULL, *server_host_key_blob = NULL, *signature = NULL;
108: u_char hash[SSH_DIGEST_MAX_LENGTH];
109: size_t klen = 0, slen, sbloblen, hashlen;
110: int kout, r;
111:
112: if (kex->verify_host_key == NULL) {
113: r = SSH_ERR_INVALID_ARGUMENT;
114: goto out;
115: }
1.1 markus 116: /* key, cert */
1.17 markus 117: if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
118: &sbloblen)) != 0 ||
119: (r = sshkey_from_blob(server_host_key_blob, sbloblen,
120: &server_host_key)) != 0)
121: goto out;
1.18 djm 122: if (server_host_key->type != kex->hostkey_type ||
123: (kex->hostkey_type == KEY_ECDSA &&
124: server_host_key->ecdsa_nid != kex->hostkey_nid)) {
1.17 markus 125: r = SSH_ERR_KEY_TYPE_MISMATCH;
126: goto out;
127: }
128: if (kex->verify_host_key(server_host_key, ssh) == -1) {
129: r = SSH_ERR_SIGNATURE_INVALID;
130: goto out;
131: }
1.6 miod 132: /* DH parameter f, server public DH key */
1.17 markus 133: if ((dh_server_pub = BN_new()) == NULL) {
134: r = SSH_ERR_ALLOC_FAIL;
135: goto out;
136: }
137: /* signed H */
138: if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 ||
139: (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
140: (r = sshpkt_get_end(ssh)) != 0)
141: goto out;
1.1 markus 142: #ifdef DEBUG_KEXDH
143: fprintf(stderr, "dh_server_pub= ");
144: BN_print_fp(stderr, dh_server_pub);
145: fprintf(stderr, "\n");
146: debug("bits %d", BN_num_bits(dh_server_pub));
147: #endif
1.17 markus 148: if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
149: sshpkt_disconnect(ssh, "bad server public DH value");
150: r = SSH_ERR_MESSAGE_INCOMPLETE;
151: goto out;
152: }
1.1 markus 153:
1.17 markus 154: klen = DH_size(kex->dh);
155: if ((kbuf = malloc(klen)) == NULL ||
156: (shared_secret = BN_new()) == NULL) {
157: r = SSH_ERR_ALLOC_FAIL;
158: goto out;
159: }
160: if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
161: BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
162: r = SSH_ERR_LIBCRYPTO_ERROR;
163: goto out;
164: }
1.1 markus 165: #ifdef DEBUG_KEXDH
166: dump_digest("shared secret", kbuf, kout);
167: #endif
168:
169: /* calc and verify H */
1.23 ! djm 170: DH_get0_key(kex->dh, &pub_key, NULL);
1.17 markus 171: hashlen = sizeof(hash);
172: if ((r = kex_dh_hash(
1.19 djm 173: kex->hash_alg,
1.1 markus 174: kex->client_version_string,
175: kex->server_version_string,
1.17 markus 176: sshbuf_ptr(kex->my), sshbuf_len(kex->my),
177: sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
1.1 markus 178: server_host_key_blob, sbloblen,
1.23 ! djm 179: pub_key,
1.1 markus 180: dh_server_pub,
1.3 djm 181: shared_secret,
1.17 markus 182: hash, &hashlen)) != 0)
183: goto out;
1.1 markus 184:
1.17 markus 185: if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
1.21 djm 186: kex->hostkey_alg, ssh->compat)) != 0)
1.17 markus 187: goto out;
1.1 markus 188:
189: /* save session id */
190: if (kex->session_id == NULL) {
1.3 djm 191: kex->session_id_len = hashlen;
1.17 markus 192: kex->session_id = malloc(kex->session_id_len);
193: if (kex->session_id == NULL) {
194: r = SSH_ERR_ALLOC_FAIL;
195: goto out;
196: }
1.1 markus 197: memcpy(kex->session_id, hash, kex->session_id_len);
198: }
199:
1.17 markus 200: if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
201: r = kex_send_newkeys(ssh);
202: out:
203: explicit_bzero(hash, sizeof(hash));
204: DH_free(kex->dh);
205: kex->dh = NULL;
1.22 jsing 206: BN_clear_free(dh_server_pub);
1.17 markus 207: if (kbuf) {
208: explicit_bzero(kbuf, klen);
209: free(kbuf);
210: }
1.22 jsing 211: BN_clear_free(shared_secret);
1.17 markus 212: sshkey_free(server_host_key);
213: free(server_host_key_blob);
214: free(signature);
215: return r;
1.1 markus 216: }
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