crypto/openssh/kexdhc.c

   1 /* $OpenBSD: kexdhc.c,v 1.20 2017/05/30 14:23:52 markus Exp $ */
   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
  26 #include "includes.h"
  27
  28 #ifdef WITH_OPENSSL
  29
  30 #include <sys/types.h>
  31
  32 #include <openssl/dh.h>
  33
  34 #include <stdarg.h>
  35 #include <stdio.h>
  36 #include <string.h>
  37 #include <signal.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_dh(int, u_int32_t, struct ssh *);
  53
  54 int
  55 kexdh_client(struct ssh *ssh)
  56 {
  57         struct kex *kex = ssh->kex;
  58         int r;
  59
  60         /* generate and send 'e', client DH public key */
  61         switch (kex->kex_type) {
  62         case KEX_DH_GRP1_SHA1:
  63                 kex->dh = dh_new_group1();
  64                 break;
  65         case KEX_DH_GRP14_SHA1:
  66         case KEX_DH_GRP14_SHA256:
  67                 kex->dh = dh_new_group14();
  68                 break;
  69         case KEX_DH_GRP16_SHA512:
  70                 kex->dh = dh_new_group16();
  71                 break;
  72         case KEX_DH_GRP18_SHA512:
  73                 kex->dh = dh_new_group18();
  74                 break;
  75         default:
  76                 r = SSH_ERR_INVALID_ARGUMENT;
  77                 goto out;
  78         }
  79         if (kex->dh == NULL) {
  80                 r = SSH_ERR_ALLOC_FAIL;
  81                 goto out;
  82         }
  83         debug("sending SSH2_MSG_KEXDH_INIT");
  84         if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 ||
  85             (r = sshpkt_start(ssh, SSH2_MSG_KEXDH_INIT)) != 0 ||
  86             (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||
  87             (r = sshpkt_send(ssh)) != 0)
  88                 goto out;
  89 #ifdef DEBUG_KEXDH
  90         DHparams_print_fp(stderr, kex->dh);
  91         fprintf(stderr, "pub= ");
  92         BN_print_fp(stderr, kex->dh->pub_key);
  93         fprintf(stderr, "\n");
  94 #endif
  95         debug("expecting SSH2_MSG_KEXDH_REPLY");
  96         ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_REPLY, &input_kex_dh);
  97         r = 0;
  98  out:
  99         return r;
 100 }
 101
 102 static int
 103 input_kex_dh(int type, u_int32_t seq, struct ssh *ssh)
 104 {
 105         struct kex *kex = ssh->kex;
 106         BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
 107         struct sshkey *server_host_key = NULL;
 108         u_char *kbuf = NULL, *server_host_key_blob = NULL, *signature = NULL;
 109         u_char hash[SSH_DIGEST_MAX_LENGTH];
 110         size_t klen = 0, slen, sbloblen, hashlen;
 111         int kout, r;
 112
 113         if (kex->verify_host_key == NULL) {
 114                 r = SSH_ERR_INVALID_ARGUMENT;
 115                 goto out;
 116         }
 117         /* key, cert */
 118         if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
 119             &sbloblen)) != 0 ||
 120             (r = sshkey_from_blob(server_host_key_blob, sbloblen,
 121             &server_host_key)) != 0)
 122                 goto out;
 123         if (server_host_key->type != kex->hostkey_type ||
 124             (kex->hostkey_type == KEY_ECDSA &&
 125             server_host_key->ecdsa_nid != kex->hostkey_nid)) {
 126                 r = SSH_ERR_KEY_TYPE_MISMATCH;
 127                 goto out;
 128         }
 129         if (kex->verify_host_key(server_host_key, ssh) == -1) {
 130                 r = SSH_ERR_SIGNATURE_INVALID;
 131                 goto out;
 132         }
 133         /* DH parameter f, server public DH key */
 134         if ((dh_server_pub = BN_new()) == NULL) {
 135                 r = SSH_ERR_ALLOC_FAIL;
 136                 goto out;
 137         }
 138         /* signed H */
 139         if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 ||
 140             (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
 141             (r = sshpkt_get_end(ssh)) != 0)
 142                 goto out;
 143 #ifdef DEBUG_KEXDH
 144         fprintf(stderr, "dh_server_pub= ");
 145         BN_print_fp(stderr, dh_server_pub);
 146         fprintf(stderr, "\n");
 147         debug("bits %d", BN_num_bits(dh_server_pub));
 148 #endif
 149         if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
 150                 sshpkt_disconnect(ssh, "bad server public DH value");
 151                 r = SSH_ERR_MESSAGE_INCOMPLETE;
 152                 goto out;
 153         }
 154
 155         klen = DH_size(kex->dh);
 156         if ((kbuf = malloc(klen)) == NULL ||
 157             (shared_secret = BN_new()) == NULL) {
 158                 r = SSH_ERR_ALLOC_FAIL;
 159                 goto out;
 160         }
 161         if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
 162             BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
 163                 r = SSH_ERR_LIBCRYPTO_ERROR;
 164                 goto out;
 165         }
 166 #ifdef DEBUG_KEXDH
 167         dump_digest("shared secret", kbuf, kout);
 168 #endif
 169
 170         /* calc and verify H */
 171         hashlen = sizeof(hash);
 172         if ((r = kex_dh_hash(
 173             kex->hash_alg,
 174             kex->client_version_string,
 175             kex->server_version_string,
 176             sshbuf_ptr(kex->my), sshbuf_len(kex->my),
 177             sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
 178             server_host_key_blob, sbloblen,
 179             kex->dh->pub_key,
 180             dh_server_pub,
 181             shared_secret,
 182             hash, &hashlen)) != 0)
 183                 goto out;
 184
 185         if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
 186             ssh->compat)) != 0)
 187                 goto out;
 188
 189         /* save session id */
 190         if (kex->session_id == NULL) {
 191                 kex->session_id_len = hashlen;
 192                 kex->session_id = malloc(kex->session_id_len);
 193                 if (kex->session_id == NULL) {
 194                         r = SSH_ERR_ALLOC_FAIL;
 195                         goto out;
 196                 }
 197                 memcpy(kex->session_id, hash, kex->session_id_len);
 198         }
 199
 200         if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
 201                 r = kex_send_newkeys(ssh);
 202  out:
 203         explicit_bzero(hash, sizeof(hash));
 204         DH_free(kex->dh);
 205         kex->dh = NULL;
 206         if (dh_server_pub)
 207                 BN_clear_free(dh_server_pub);
 208         if (kbuf) {
 209                 explicit_bzero(kbuf, klen);
 210                 free(kbuf);
 211         }
 212         if (shared_secret)
 213                 BN_clear_free(shared_secret);
 214         sshkey_free(server_host_key);
 215         free(server_host_key_blob);
 216         free(signature);
 217         return r;
 218 }
 219 #endif /* WITH_OPENSSL */