crypto/openssh/kexecdhc.c

   1 /* $OpenBSD: kexecdhc.c,v 1.11 2017/05/30 14:23:52 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
  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, struct ssh *);
  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, struct ssh *ssh)
  99 {
 100         struct kex *kex = ssh->kex;
 101         const EC_GROUP *group;
 102         EC_POINT *server_public = NULL;
 103         EC_KEY *client_key;
 104         BIGNUM *shared_secret = NULL;
 105         struct sshkey *server_host_key = NULL;
 106         u_char *server_host_key_blob = NULL, *signature = NULL;
 107         u_char *kbuf = NULL;
 108         u_char hash[SSH_DIGEST_MAX_LENGTH];
 109         size_t slen, sbloblen;
 110         size_t klen = 0, hashlen;
 111         int r;
 112
 113         if (kex->verify_host_key == NULL) {
 114                 r = SSH_ERR_INVALID_ARGUMENT;
 115                 goto out;
 116         }
 117         group = kex->ec_group;
 118         client_key = kex->ec_client_key;
 119
 120         /* hostkey */
 121         if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
 122             &sbloblen)) != 0 ||
 123             (r = sshkey_from_blob(server_host_key_blob, sbloblen,
 124             &server_host_key)) != 0)
 125                 goto out;
 126         if (server_host_key->type != kex->hostkey_type ||
 127             (kex->hostkey_type == KEY_ECDSA &&
 128             server_host_key->ecdsa_nid != kex->hostkey_nid)) {
 129                 r = SSH_ERR_KEY_TYPE_MISMATCH;
 130                 goto out;
 131         }
 132         if (kex->verify_host_key(server_host_key, ssh) == -1) {
 133                 r = SSH_ERR_SIGNATURE_INVALID;
 134                 goto out;
 135         }
 136
 137         /* Q_S, server public key */
 138         /* signed H */
 139         if ((server_public = EC_POINT_new(group)) == NULL) {
 140                 r = SSH_ERR_ALLOC_FAIL;
 141                 goto out;
 142         }
 143         if ((r = sshpkt_get_ec(ssh, server_public, group)) != 0 ||
 144             (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
 145             (r = sshpkt_get_end(ssh)) != 0)
 146                 goto out;
 147
 148 #ifdef DEBUG_KEXECDH
 149         fputs("server public key:\n", stderr);
 150         sshkey_dump_ec_point(group, server_public);
 151 #endif
 152         if (sshkey_ec_validate_public(group, server_public) != 0) {
 153                 sshpkt_disconnect(ssh, "invalid server public key");
 154                 r = SSH_ERR_MESSAGE_INCOMPLETE;
 155                 goto out;
 156         }
 157
 158         klen = (EC_GROUP_get_degree(group) + 7) / 8;
 159         if ((kbuf = malloc(klen)) == NULL ||
 160             (shared_secret = BN_new()) == NULL) {
 161                 r = SSH_ERR_ALLOC_FAIL;
 162                 goto out;
 163         }
 164         if (ECDH_compute_key(kbuf, klen, server_public,
 165             client_key, NULL) != (int)klen ||
 166             BN_bin2bn(kbuf, klen, shared_secret) == NULL) {
 167                 r = SSH_ERR_LIBCRYPTO_ERROR;
 168                 goto out;
 169         }
 170
 171 #ifdef DEBUG_KEXECDH
 172         dump_digest("shared secret", kbuf, klen);
 173 #endif
 174         /* calc and verify H */
 175         hashlen = sizeof(hash);
 176         if ((r = kex_ecdh_hash(
 177             kex->hash_alg,
 178             group,
 179             kex->client_version_string,
 180             kex->server_version_string,
 181             sshbuf_ptr(kex->my), sshbuf_len(kex->my),
 182             sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
 183             server_host_key_blob, sbloblen,
 184             EC_KEY_get0_public_key(client_key),
 185             server_public,
 186             shared_secret,
 187             hash, &hashlen)) != 0)
 188                 goto out;
 189
 190         if ((r = sshkey_verify(server_host_key, signature, slen, hash,
 191             hashlen, ssh->compat)) != 0)
 192                 goto out;
 193
 194         /* save session id */
 195         if (kex->session_id == NULL) {
 196                 kex->session_id_len = hashlen;
 197                 kex->session_id = malloc(kex->session_id_len);
 198                 if (kex->session_id == NULL) {
 199                         r = SSH_ERR_ALLOC_FAIL;
 200                         goto out;
 201                 }
 202                 memcpy(kex->session_id, hash, kex->session_id_len);
 203         }
 204
 205         if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
 206                 r = kex_send_newkeys(ssh);
 207  out:
 208         explicit_bzero(hash, sizeof(hash));
 209         if (kex->ec_client_key) {
 210                 EC_KEY_free(kex->ec_client_key);
 211                 kex->ec_client_key = NULL;
 212         }
 213         if (server_public)
 214                 EC_POINT_clear_free(server_public);
 215         if (kbuf) {
 216                 explicit_bzero(kbuf, klen);
 217                 free(kbuf);
 218         }
 219         if (shared_secret)
 220                 BN_clear_free(shared_secret);
 221         sshkey_free(server_host_key);
 222         free(server_host_key_blob);
 223         free(signature);
 224         return r;
 225 }
 226 #endif /* defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) */
 227