Annotation of src/usr.bin/ssh/kexdhs.c, Revision 1.32
1.32 ! djm 1: /* $OpenBSD: kexdhs.c,v 1.31 2019/01/21 09:54:11 djm 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:
1.6 stevesk 26:
1.7 deraadt 27: #include <sys/types.h>
1.6 stevesk 28: #include <string.h>
1.7 deraadt 29: #include <signal.h>
1.12 djm 30:
31: #include <openssl/dh.h>
1.1 markus 32:
1.20 markus 33: #include "sshkey.h"
1.7 deraadt 34: #include "cipher.h"
1.20 markus 35: #include "digest.h"
1.1 markus 36: #include "kex.h"
37: #include "log.h"
38: #include "packet.h"
39: #include "dh.h"
40: #include "ssh2.h"
41:
1.20 markus 42: #include "dispatch.h"
43: #include "compat.h"
44: #include "ssherr.h"
45: #include "sshbuf.h"
46:
1.25 markus 47: static int input_kex_dh_init(int, u_int32_t, struct ssh *);
1.20 markus 48:
49: int
50: kexdh_server(struct ssh *ssh)
1.1 markus 51: {
1.20 markus 52: struct kex *kex = ssh->kex;
53: int r;
1.1 markus 54:
55: /* generate server DH public key */
1.2 djm 56: switch (kex->kex_type) {
57: case KEX_DH_GRP1_SHA1:
1.20 markus 58: kex->dh = dh_new_group1();
1.2 djm 59: break;
60: case KEX_DH_GRP14_SHA1:
1.24 djm 61: case KEX_DH_GRP14_SHA256:
1.20 markus 62: kex->dh = dh_new_group14();
1.2 djm 63: break;
1.24 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:
1.20 markus 71: r = SSH_ERR_INVALID_ARGUMENT;
72: goto out;
1.2 djm 73: }
1.20 markus 74: if (kex->dh == NULL) {
75: r = SSH_ERR_ALLOC_FAIL;
76: goto out;
77: }
78: if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
79: goto out;
1.1 markus 80:
81: debug("expecting SSH2_MSG_KEXDH_INIT");
1.20 markus 82: ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_INIT, &input_kex_dh_init);
83: r = 0;
84: out:
85: return r;
86: }
87:
88: int
1.25 markus 89: input_kex_dh_init(int type, u_int32_t seq, struct ssh *ssh)
1.20 markus 90: {
91: struct kex *kex = ssh->kex;
92: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
1.28 djm 93: const BIGNUM *pub_key;
1.20 markus 94: struct sshkey *server_host_public, *server_host_private;
95: u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
96: u_char hash[SSH_DIGEST_MAX_LENGTH];
97: size_t sbloblen, slen;
98: size_t klen = 0, hashlen;
99: int kout, r;
1.1 markus 100:
1.11 djm 101: if (kex->load_host_public_key == NULL ||
1.20 markus 102: kex->load_host_private_key == NULL) {
103: r = SSH_ERR_INVALID_ARGUMENT;
104: goto out;
105: }
1.22 djm 106: server_host_public = kex->load_host_public_key(kex->hostkey_type,
107: kex->hostkey_nid, ssh);
108: server_host_private = kex->load_host_private_key(kex->hostkey_type,
109: kex->hostkey_nid, ssh);
1.21 djm 110: if (server_host_public == NULL) {
1.20 markus 111: r = SSH_ERR_NO_HOSTKEY_LOADED;
112: goto out;
113: }
1.1 markus 114:
115: /* key, cert */
1.31 djm 116: if ((r = sshpkt_get_bignum2(ssh, &dh_client_pub)) != 0 ||
117: (r = sshpkt_get_end(ssh)) != 0)
1.20 markus 118: goto out;
1.28 djm 119: DH_get0_key(kex->dh, &pub_key, NULL);
1.1 markus 120:
121: #ifdef DEBUG_KEXDH
122: fprintf(stderr, "dh_client_pub= ");
123: BN_print_fp(stderr, dh_client_pub);
124: fprintf(stderr, "\n");
125: debug("bits %d", BN_num_bits(dh_client_pub));
1.20 markus 126: DHparams_print_fp(stderr, kex->dh);
1.1 markus 127: fprintf(stderr, "pub= ");
1.28 djm 128: BN_print_fp(stderr, pub_key);
1.1 markus 129: fprintf(stderr, "\n");
130: #endif
1.20 markus 131: if (!dh_pub_is_valid(kex->dh, dh_client_pub)) {
132: sshpkt_disconnect(ssh, "bad client public DH value");
133: r = SSH_ERR_MESSAGE_INCOMPLETE;
134: goto out;
135: }
1.1 markus 136:
1.20 markus 137: klen = DH_size(kex->dh);
138: if ((kbuf = malloc(klen)) == NULL ||
139: (shared_secret = BN_new()) == NULL) {
140: r = SSH_ERR_ALLOC_FAIL;
141: goto out;
142: }
143: if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 ||
144: BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
145: r = SSH_ERR_LIBCRYPTO_ERROR;
146: goto out;
147: }
1.1 markus 148: #ifdef DEBUG_KEXDH
149: dump_digest("shared secret", kbuf, kout);
150: #endif
1.20 markus 151: if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
152: &sbloblen)) != 0)
153: goto out;
1.1 markus 154: /* calc H */
1.20 markus 155: hashlen = sizeof(hash);
156: if ((r = kex_dh_hash(
1.24 djm 157: kex->hash_alg,
1.29 djm 158: kex->client_version,
159: kex->server_version,
1.20 markus 160: sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
161: sshbuf_ptr(kex->my), sshbuf_len(kex->my),
1.1 markus 162: server_host_key_blob, sbloblen,
163: dh_client_pub,
1.28 djm 164: pub_key,
1.3 djm 165: shared_secret,
1.20 markus 166: hash, &hashlen)) != 0)
167: goto out;
1.1 markus 168:
169: /* sign H */
1.30 djm 170: if ((r = kex->sign(ssh, server_host_private, server_host_public,
171: &signature, &slen, hash, hashlen, kex->hostkey_alg)) < 0)
1.20 markus 172: goto out;
1.1 markus 173:
174: /* destroy_sensitive_data(); */
175:
1.27 djm 176: /* send server hostkey, DH pubkey 'f' and signed H */
1.20 markus 177: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXDH_REPLY)) != 0 ||
178: (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
1.28 djm 179: (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 || /* f */
1.20 markus 180: (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
181: (r = sshpkt_send(ssh)) != 0)
182: goto out;
183:
184: if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
185: r = kex_send_newkeys(ssh);
186: out:
187: explicit_bzero(hash, sizeof(hash));
188: DH_free(kex->dh);
189: kex->dh = NULL;
1.26 jsing 190: BN_clear_free(dh_client_pub);
1.20 markus 191: if (kbuf) {
192: explicit_bzero(kbuf, klen);
193: free(kbuf);
194: }
1.26 jsing 195: BN_clear_free(shared_secret);
1.20 markus 196: free(server_host_key_blob);
1.13 djm 197: free(signature);
1.20 markus 198: return r;
1.1 markus 199: }