crypto/openssh/kexecdhs.c

   1 /* $OpenBSD: kexecdhs.c,v 1.15 2015/12/04 16:41:28 markus 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 #include <string.h>
  33 #include <signal.h>
  34
  35 #include <openssl/ecdh.h>
  36
  37 #include "sshkey.h"
  38 #include "cipher.h"
  39 #include "digest.h"
  40 #include "kex.h"
  41 #include "log.h"
  42 #include "packet.h"
  43 #include "ssh2.h"
  44
  45 #include "dispatch.h"
  46 #include "compat.h"
  47 #include "ssherr.h"
  48 #include "sshbuf.h"
  49
  50 static int input_kex_ecdh_init(int, u_int32_t, void *);
  51
  52 int
  53 kexecdh_server(struct ssh *ssh)
  54 {
  55         debug("expecting SSH2_MSG_KEX_ECDH_INIT");
  56         ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_ecdh_init);
  57         return 0;
  58 }
  59
  60 static int
  61 input_kex_ecdh_init(int type, u_int32_t seq, void *ctxt)
  62 {
  63         struct ssh *ssh = ctxt;
  64         struct kex *kex = ssh->kex;
  65         EC_POINT *client_public;
  66         EC_KEY *server_key = NULL;
  67         const EC_GROUP *group;
  68         const EC_POINT *public_key;
  69         BIGNUM *shared_secret = NULL;
  70         struct sshkey *server_host_private, *server_host_public;
  71         u_char *server_host_key_blob = NULL, *signature = NULL;
  72         u_char *kbuf = NULL;
  73         u_char hash[SSH_DIGEST_MAX_LENGTH];
  74         size_t slen, sbloblen;
  75         size_t klen = 0, hashlen;
  76         int r;
  77
  78         if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) {
  79                 r = SSH_ERR_ALLOC_FAIL;
  80                 goto out;
  81         }
  82         if (EC_KEY_generate_key(server_key) != 1) {
  83                 r = SSH_ERR_LIBCRYPTO_ERROR;
  84                 goto out;
  85         }
  86         group = EC_KEY_get0_group(server_key);
  87
  88 #ifdef DEBUG_KEXECDH
  89         fputs("server private key:\n", stderr);
  90         sshkey_dump_ec_key(server_key);
  91 #endif
  92
  93         if (kex->load_host_public_key == NULL ||
  94             kex->load_host_private_key == NULL) {
  95                 r = SSH_ERR_INVALID_ARGUMENT;
  96                 goto out;
  97         }
  98         server_host_public = kex->load_host_public_key(kex->hostkey_type,
  99             kex->hostkey_nid, ssh);
 100         server_host_private = kex->load_host_private_key(kex->hostkey_type,
 101             kex->hostkey_nid, ssh);
 102         if (server_host_public == NULL) {
 103                 r = SSH_ERR_NO_HOSTKEY_LOADED;
 104                 goto out;
 105         }
 106         if ((client_public = EC_POINT_new(group)) == NULL) {
 107                 r = SSH_ERR_ALLOC_FAIL;
 108                 goto out;
 109         }
 110         if ((r = sshpkt_get_ec(ssh, client_public, group)) != 0 ||
 111             (r = sshpkt_get_end(ssh)) != 0)
 112                 goto out;
 113
 114 #ifdef DEBUG_KEXECDH
 115         fputs("client public key:\n", stderr);
 116         sshkey_dump_ec_point(group, client_public);
 117 #endif
 118         if (sshkey_ec_validate_public(group, client_public) != 0) {
 119                 sshpkt_disconnect(ssh, "invalid client public key");
 120                 r = SSH_ERR_MESSAGE_INCOMPLETE;
 121                 goto out;
 122         }
 123
 124         /* Calculate shared_secret */
 125         klen = (EC_GROUP_get_degree(group) + 7) / 8;
 126         if ((kbuf = malloc(klen)) == NULL ||
 127             (shared_secret = BN_new()) == NULL) {
 128                 r = SSH_ERR_ALLOC_FAIL;
 129                 goto out;
 130         }
 131         if (ECDH_compute_key(kbuf, klen, client_public,
 132             server_key, NULL) != (int)klen ||
 133             BN_bin2bn(kbuf, klen, shared_secret) == NULL) {
 134                 r = SSH_ERR_LIBCRYPTO_ERROR;
 135                 goto out;
 136         }
 137
 138 #ifdef DEBUG_KEXECDH
 139         dump_digest("shared secret", kbuf, klen);
 140 #endif
 141         /* calc H */
 142         if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
 143             &sbloblen)) != 0)
 144                 goto out;
 145         hashlen = sizeof(hash);
 146         if ((r = kex_ecdh_hash(
 147             kex->hash_alg,
 148             group,
 149             kex->client_version_string,
 150             kex->server_version_string,
 151             sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
 152             sshbuf_ptr(kex->my), sshbuf_len(kex->my),
 153             server_host_key_blob, sbloblen,
 154             client_public,
 155             EC_KEY_get0_public_key(server_key),
 156             shared_secret,
 157             hash, &hashlen)) != 0)
 158                 goto out;
 159
 160         /* save session id := H */
 161         if (kex->session_id == NULL) {
 162                 kex->session_id_len = hashlen;
 163                 kex->session_id = malloc(kex->session_id_len);
 164                 if (kex->session_id == NULL) {
 165                         r = SSH_ERR_ALLOC_FAIL;
 166                         goto out;
 167                 }
 168                 memcpy(kex->session_id, hash, kex->session_id_len);
 169         }
 170
 171         /* sign H */
 172         if ((r = kex->sign(server_host_private, server_host_public, &signature,
 173              &slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0)
 174                 goto out;
 175
 176         /* destroy_sensitive_data(); */
 177
 178         public_key = EC_KEY_get0_public_key(server_key);
 179         /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
 180         if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
 181             (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
 182             (r = sshpkt_put_ec(ssh, public_key, group)) != 0 ||
 183             (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
 184             (r = sshpkt_send(ssh)) != 0)
 185                 goto out;
 186
 187         if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
 188                 r = kex_send_newkeys(ssh);
 189  out:
 190         explicit_bzero(hash, sizeof(hash));
 191         if (kex->ec_client_key) {
 192                 EC_KEY_free(kex->ec_client_key);
 193                 kex->ec_client_key = NULL;
 194         }
 195         if (server_key)
 196                 EC_KEY_free(server_key);
 197         if (kbuf) {
 198                 explicit_bzero(kbuf, klen);
 199                 free(kbuf);
 200         }
 201         if (shared_secret)
 202                 BN_clear_free(shared_secret);
 203         free(server_host_key_blob);
 204         free(signature);
 205         return r;
 206 }
 207 #endif /* defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) */
 208