Annotation of src/usr.bin/ssh/kexdhc.c, Revision 1.18
1.18 ! djm 1: /* $OpenBSD: kexdhc.c,v 1.17 2015/01/19 20:16:15 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:
1.17 markus 47: static int input_kex_dh(int, u_int32_t, void *);
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:
1.17 markus 61: kex->dh = dh_new_group14();
1.2 djm 62: break;
63: default:
1.17 markus 64: r = SSH_ERR_INVALID_ARGUMENT;
65: goto out;
66: }
67: if (kex->dh == NULL) {
68: r = SSH_ERR_ALLOC_FAIL;
69: goto out;
1.2 djm 70: }
1.1 markus 71: debug("sending SSH2_MSG_KEXDH_INIT");
1.17 markus 72: if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 ||
73: (r = sshpkt_start(ssh, SSH2_MSG_KEXDH_INIT)) != 0 ||
74: (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||
75: (r = sshpkt_send(ssh)) != 0)
76: goto out;
1.1 markus 77: #ifdef DEBUG_KEXDH
1.17 markus 78: DHparams_print_fp(stderr, kex->dh);
1.1 markus 79: fprintf(stderr, "pub= ");
1.17 markus 80: BN_print_fp(stderr, kex->dh->pub_key);
1.1 markus 81: fprintf(stderr, "\n");
82: #endif
83: debug("expecting SSH2_MSG_KEXDH_REPLY");
1.17 markus 84: ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_REPLY, &input_kex_dh);
85: r = 0;
86: out:
87: return r;
88: }
1.1 markus 89:
1.17 markus 90: static int
91: input_kex_dh(int type, u_int32_t seq, void *ctxt)
92: {
93: struct ssh *ssh = ctxt;
94: struct kex *kex = ssh->kex;
95: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
96: struct sshkey *server_host_key = NULL;
97: u_char *kbuf = NULL, *server_host_key_blob = NULL, *signature = NULL;
98: u_char hash[SSH_DIGEST_MAX_LENGTH];
99: size_t klen = 0, slen, sbloblen, hashlen;
100: int kout, r;
101:
102: if (kex->verify_host_key == NULL) {
103: r = SSH_ERR_INVALID_ARGUMENT;
104: goto out;
105: }
1.1 markus 106: /* key, cert */
1.17 markus 107: if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
108: &sbloblen)) != 0 ||
109: (r = sshkey_from_blob(server_host_key_blob, sbloblen,
110: &server_host_key)) != 0)
111: goto out;
1.18 ! djm 112: if (server_host_key->type != kex->hostkey_type ||
! 113: (kex->hostkey_type == KEY_ECDSA &&
! 114: server_host_key->ecdsa_nid != kex->hostkey_nid)) {
1.17 markus 115: r = SSH_ERR_KEY_TYPE_MISMATCH;
116: goto out;
117: }
118: if (kex->verify_host_key(server_host_key, ssh) == -1) {
119: r = SSH_ERR_SIGNATURE_INVALID;
120: goto out;
121: }
1.6 miod 122: /* DH parameter f, server public DH key */
1.17 markus 123: if ((dh_server_pub = BN_new()) == NULL) {
124: r = SSH_ERR_ALLOC_FAIL;
125: goto out;
126: }
127: /* signed H */
128: if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 ||
129: (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
130: (r = sshpkt_get_end(ssh)) != 0)
131: goto out;
1.1 markus 132: #ifdef DEBUG_KEXDH
133: fprintf(stderr, "dh_server_pub= ");
134: BN_print_fp(stderr, dh_server_pub);
135: fprintf(stderr, "\n");
136: debug("bits %d", BN_num_bits(dh_server_pub));
137: #endif
1.17 markus 138: if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
139: sshpkt_disconnect(ssh, "bad server public DH value");
140: r = SSH_ERR_MESSAGE_INCOMPLETE;
141: goto out;
142: }
1.1 markus 143:
1.17 markus 144: klen = DH_size(kex->dh);
145: if ((kbuf = malloc(klen)) == NULL ||
146: (shared_secret = BN_new()) == NULL) {
147: r = SSH_ERR_ALLOC_FAIL;
148: goto out;
149: }
150: if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
151: BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
152: r = SSH_ERR_LIBCRYPTO_ERROR;
153: goto out;
154: }
1.1 markus 155: #ifdef DEBUG_KEXDH
156: dump_digest("shared secret", kbuf, kout);
157: #endif
158:
159: /* calc and verify H */
1.17 markus 160: hashlen = sizeof(hash);
161: if ((r = kex_dh_hash(
1.1 markus 162: kex->client_version_string,
163: kex->server_version_string,
1.17 markus 164: sshbuf_ptr(kex->my), sshbuf_len(kex->my),
165: sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
1.1 markus 166: server_host_key_blob, sbloblen,
1.17 markus 167: kex->dh->pub_key,
1.1 markus 168: dh_server_pub,
1.3 djm 169: shared_secret,
1.17 markus 170: hash, &hashlen)) != 0)
171: goto out;
1.1 markus 172:
1.17 markus 173: if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
174: ssh->compat)) != 0)
175: goto out;
1.1 markus 176:
177: /* save session id */
178: if (kex->session_id == NULL) {
1.3 djm 179: kex->session_id_len = hashlen;
1.17 markus 180: kex->session_id = malloc(kex->session_id_len);
181: if (kex->session_id == NULL) {
182: r = SSH_ERR_ALLOC_FAIL;
183: goto out;
184: }
1.1 markus 185: memcpy(kex->session_id, hash, kex->session_id_len);
186: }
187:
1.17 markus 188: if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
189: r = kex_send_newkeys(ssh);
190: out:
191: explicit_bzero(hash, sizeof(hash));
192: DH_free(kex->dh);
193: kex->dh = NULL;
194: if (dh_server_pub)
195: BN_clear_free(dh_server_pub);
196: if (kbuf) {
197: explicit_bzero(kbuf, klen);
198: free(kbuf);
199: }
200: if (shared_secret)
201: BN_clear_free(shared_secret);
202: sshkey_free(server_host_key);
203: free(server_host_key_blob);
204: free(signature);
205: return r;
1.1 markus 206: }
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