1 /* $OpenBSD: kexecdhc.c,v 1.10 2015/01/26 06:10:03 djm Exp $ */ 2 /* 3 * Copyright (c) 2001 Markus Friedl. All rights reserved. 4 * Copyright (c) 2010 Damien Miller. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 29 #if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) 30 31 #include <sys/types.h> 32 33 #include <stdio.h> 34 #include <string.h> 35 #include <signal.h> 36 37 #include <openssl/ecdh.h> 38 39 #include "sshkey.h" 40 #include "cipher.h" 41 #include "digest.h" 42 #include "kex.h" 43 #include "log.h" 44 #include "packet.h" 45 #include "dh.h" 46 #include "ssh2.h" 47 #include "dispatch.h" 48 #include "compat.h" 49 #include "ssherr.h" 50 #include "sshbuf.h" 51 52 static int input_kex_ecdh_reply(int, u_int32_t, void *); 53 54 int 55 kexecdh_client(struct ssh *ssh) 56 { 57 struct kex *kex = ssh->kex; 58 EC_KEY *client_key = NULL; 59 const EC_GROUP *group; 60 const EC_POINT *public_key; 61 int r; 62 63 if ((client_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) { 64 r = SSH_ERR_ALLOC_FAIL; 65 goto out; 66 } 67 if (EC_KEY_generate_key(client_key) != 1) { 68 r = SSH_ERR_LIBCRYPTO_ERROR; 69 goto out; 70 } 71 group = EC_KEY_get0_group(client_key); 72 public_key = EC_KEY_get0_public_key(client_key); 73 74 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 || 75 (r = sshpkt_put_ec(ssh, public_key, group)) != 0 || 76 (r = sshpkt_send(ssh)) != 0) 77 goto out; 78 debug("sending SSH2_MSG_KEX_ECDH_INIT"); 79 80 #ifdef DEBUG_KEXECDH 81 fputs("client private key:\n", stderr); 82 sshkey_dump_ec_key(client_key); 83 #endif 84 kex->ec_client_key = client_key; 85 kex->ec_group = group; 86 client_key = NULL; /* owned by the kex */ 87 88 debug("expecting SSH2_MSG_KEX_ECDH_REPLY"); 89 ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_ecdh_reply); 90 r = 0; 91 out: 92 if (client_key) 93 EC_KEY_free(client_key); 94 return r; 95 } 96 97 static int 98 input_kex_ecdh_reply(int type, u_int32_t seq, void *ctxt) 99 { 100 struct ssh *ssh = ctxt; 101 struct kex *kex = ssh->kex; 102 const EC_GROUP *group; 103 EC_POINT *server_public = NULL; 104 EC_KEY *client_key; 105 BIGNUM *shared_secret = NULL; 106 struct sshkey *server_host_key = NULL; 107 u_char *server_host_key_blob = NULL, *signature = NULL; 108 u_char *kbuf = NULL; 109 u_char hash[SSH_DIGEST_MAX_LENGTH]; 110 size_t slen, sbloblen; 111 size_t klen = 0, hashlen; 112 int r; 113 114 if (kex->verify_host_key == NULL) { 115 r = SSH_ERR_INVALID_ARGUMENT; 116 goto out; 117 } 118 group = kex->ec_group; 119 client_key = kex->ec_client_key; 120 121 /* hostkey */ 122 if ((r = sshpkt_get_string(ssh, &server_host_key_blob, 123 &sbloblen)) != 0 || 124 (r = sshkey_from_blob(server_host_key_blob, sbloblen, 125 &server_host_key)) != 0) 126 goto out; 127 if (server_host_key->type != kex->hostkey_type || 128 (kex->hostkey_type == KEY_ECDSA && 129 server_host_key->ecdsa_nid != kex->hostkey_nid)) { 130 r = SSH_ERR_KEY_TYPE_MISMATCH; 131 goto out; 132 } 133 if (kex->verify_host_key(server_host_key, ssh) == -1) { 134 r = SSH_ERR_SIGNATURE_INVALID; 135 goto out; 136 } 137 138 /* Q_S, server public key */ 139 /* signed H */ 140 if ((server_public = EC_POINT_new(group)) == NULL) { 141 r = SSH_ERR_ALLOC_FAIL; 142 goto out; 143 } 144 if ((r = sshpkt_get_ec(ssh, server_public, group)) != 0 || 145 (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 || 146 (r = sshpkt_get_end(ssh)) != 0) 147 goto out; 148 149 #ifdef DEBUG_KEXECDH 150 fputs("server public key:\n", stderr); 151 sshkey_dump_ec_point(group, server_public); 152 #endif 153 if (sshkey_ec_validate_public(group, server_public) != 0) { 154 sshpkt_disconnect(ssh, "invalid server public key"); 155 r = SSH_ERR_MESSAGE_INCOMPLETE; 156 goto out; 157 } 158 159 klen = (EC_GROUP_get_degree(group) + 7) / 8; 160 if ((kbuf = malloc(klen)) == NULL || 161 (shared_secret = BN_new()) == NULL) { 162 r = SSH_ERR_ALLOC_FAIL; 163 goto out; 164 } 165 if (ECDH_compute_key(kbuf, klen, server_public, 166 client_key, NULL) != (int)klen || 167 BN_bin2bn(kbuf, klen, shared_secret) == NULL) { 168 r = SSH_ERR_LIBCRYPTO_ERROR; 169 goto out; 170 } 171 172 #ifdef DEBUG_KEXECDH 173 dump_digest("shared secret", kbuf, klen); 174 #endif 175 /* calc and verify H */ 176 hashlen = sizeof(hash); 177 if ((r = kex_ecdh_hash( 178 kex->hash_alg, 179 group, 180 kex->client_version_string, 181 kex->server_version_string, 182 sshbuf_ptr(kex->my), sshbuf_len(kex->my), 183 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer), 184 server_host_key_blob, sbloblen, 185 EC_KEY_get0_public_key(client_key), 186 server_public, 187 shared_secret, 188 hash, &hashlen)) != 0) 189 goto out; 190 191 if ((r = sshkey_verify(server_host_key, signature, slen, hash, 192 hashlen, ssh->compat)) != 0) 193 goto out; 194 195 /* save session id */ 196 if (kex->session_id == NULL) { 197 kex->session_id_len = hashlen; 198 kex->session_id = malloc(kex->session_id_len); 199 if (kex->session_id == NULL) { 200 r = SSH_ERR_ALLOC_FAIL; 201 goto out; 202 } 203 memcpy(kex->session_id, hash, kex->session_id_len); 204 } 205 206 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0) 207 r = kex_send_newkeys(ssh); 208 out: 209 explicit_bzero(hash, sizeof(hash)); 210 if (kex->ec_client_key) { 211 EC_KEY_free(kex->ec_client_key); 212 kex->ec_client_key = NULL; 213 } 214 if (server_public) 215 EC_POINT_clear_free(server_public); 216 if (kbuf) { 217 explicit_bzero(kbuf, klen); 218 free(kbuf); 219 } 220 if (shared_secret) 221 BN_clear_free(shared_secret); 222 sshkey_free(server_host_key); 223 free(server_host_key_blob); 224 free(signature); 225 return r; 226 } 227 #endif /* defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) */ 228 229
