Annotation of src/usr.bin/ssh/kexdhc.c, Revision 1.27
1.27 ! djm 1: /* $OpenBSD: kexdhc.c,v 1.26 2019/01/21 09:55:52 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:
1.9 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"
1.27 ! djm 37: #include "dh.h"
1.1 markus 38: #include "kex.h"
39: #include "log.h"
40: #include "packet.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 */
1.27 ! djm 57: if ((r = kex_dh_keygen(kex)) != 0)
1.17 markus 58: goto out;
1.1 markus 59: debug("sending SSH2_MSG_KEXDH_INIT");
1.23 djm 60: DH_get0_key(kex->dh, &pub_key, NULL);
61: if ((r = sshpkt_start(ssh, SSH2_MSG_KEXDH_INIT)) != 0 ||
62: (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 ||
1.17 markus 63: (r = sshpkt_send(ssh)) != 0)
64: goto out;
1.1 markus 65: #ifdef DEBUG_KEXDH
1.17 markus 66: DHparams_print_fp(stderr, kex->dh);
1.1 markus 67: fprintf(stderr, "pub= ");
1.23 djm 68: BN_print_fp(stderr, pub_key);
1.1 markus 69: fprintf(stderr, "\n");
70: #endif
71: debug("expecting SSH2_MSG_KEXDH_REPLY");
1.17 markus 72: ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_REPLY, &input_kex_dh);
73: r = 0;
74: out:
75: return r;
76: }
1.1 markus 77:
1.17 markus 78: static int
1.20 markus 79: input_kex_dh(int type, u_int32_t seq, struct ssh *ssh)
1.17 markus 80: {
81: struct kex *kex = ssh->kex;
82: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
1.23 djm 83: const BIGNUM *pub_key;
1.17 markus 84: struct sshkey *server_host_key = NULL;
85: u_char *kbuf = NULL, *server_host_key_blob = NULL, *signature = NULL;
86: u_char hash[SSH_DIGEST_MAX_LENGTH];
87: size_t klen = 0, slen, sbloblen, hashlen;
88: int kout, r;
89:
90: if (kex->verify_host_key == NULL) {
91: r = SSH_ERR_INVALID_ARGUMENT;
92: goto out;
93: }
1.1 markus 94: /* key, cert */
1.17 markus 95: if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
96: &sbloblen)) != 0 ||
97: (r = sshkey_from_blob(server_host_key_blob, sbloblen,
98: &server_host_key)) != 0)
99: goto out;
1.18 djm 100: if (server_host_key->type != kex->hostkey_type ||
101: (kex->hostkey_type == KEY_ECDSA &&
102: server_host_key->ecdsa_nid != kex->hostkey_nid)) {
1.17 markus 103: r = SSH_ERR_KEY_TYPE_MISMATCH;
104: goto out;
105: }
106: if (kex->verify_host_key(server_host_key, ssh) == -1) {
107: r = SSH_ERR_SIGNATURE_INVALID;
108: goto out;
109: }
1.25 djm 110: /* DH parameter f, server public DH key, signed H */
111: if ((r = sshpkt_get_bignum2(ssh, &dh_server_pub)) != 0 ||
1.17 markus 112: (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
113: (r = sshpkt_get_end(ssh)) != 0)
114: goto out;
1.1 markus 115: #ifdef DEBUG_KEXDH
116: fprintf(stderr, "dh_server_pub= ");
117: BN_print_fp(stderr, dh_server_pub);
118: fprintf(stderr, "\n");
119: debug("bits %d", BN_num_bits(dh_server_pub));
120: #endif
1.17 markus 121: if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
122: sshpkt_disconnect(ssh, "bad server public DH value");
123: r = SSH_ERR_MESSAGE_INCOMPLETE;
124: goto out;
125: }
1.1 markus 126:
1.17 markus 127: klen = DH_size(kex->dh);
128: if ((kbuf = malloc(klen)) == NULL ||
129: (shared_secret = BN_new()) == NULL) {
130: r = SSH_ERR_ALLOC_FAIL;
131: goto out;
132: }
133: if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
134: BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
135: r = SSH_ERR_LIBCRYPTO_ERROR;
136: goto out;
137: }
1.1 markus 138: #ifdef DEBUG_KEXDH
139: dump_digest("shared secret", kbuf, kout);
140: #endif
141:
142: /* calc and verify H */
1.23 djm 143: DH_get0_key(kex->dh, &pub_key, NULL);
1.17 markus 144: hashlen = sizeof(hash);
145: if ((r = kex_dh_hash(
1.19 djm 146: kex->hash_alg,
1.24 djm 147: kex->client_version,
148: kex->server_version,
1.17 markus 149: sshbuf_ptr(kex->my), sshbuf_len(kex->my),
150: sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
1.1 markus 151: server_host_key_blob, sbloblen,
1.23 djm 152: pub_key,
1.1 markus 153: dh_server_pub,
1.3 djm 154: shared_secret,
1.17 markus 155: hash, &hashlen)) != 0)
156: goto out;
1.1 markus 157:
1.17 markus 158: if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
1.21 djm 159: kex->hostkey_alg, ssh->compat)) != 0)
1.17 markus 160: goto out;
1.1 markus 161:
1.17 markus 162: if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
163: r = kex_send_newkeys(ssh);
164: out:
165: explicit_bzero(hash, sizeof(hash));
166: DH_free(kex->dh);
167: kex->dh = NULL;
1.22 jsing 168: BN_clear_free(dh_server_pub);
1.17 markus 169: if (kbuf) {
170: explicit_bzero(kbuf, klen);
171: free(kbuf);
172: }
1.22 jsing 173: BN_clear_free(shared_secret);
1.17 markus 174: sshkey_free(server_host_key);
175: free(server_host_key_blob);
176: free(signature);
177: return r;
1.1 markus 178: }
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