openssh/kexgssc.c

   1 /*
   2  * Copyright (c) 2001-2006 Simon Wilkinson. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
  14  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  15  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  16  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  17  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  18  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  19  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  20  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  22  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  23  */
  24
  25 #include "includes.h"
  26
  27 #ifdef GSSAPI
  28
  29 #include "includes.h"
  30
  31 #include <openssl/crypto.h>
  32 #include <openssl/bn.h>
  33
  34 #include <string.h>
  35
  36 #include "xmalloc.h"
  37 #include "buffer.h"
  38 #include "ssh2.h"
  39 #include "key.h"
  40 #include "cipher.h"
  41 #include "kex.h"
  42 #include "log.h"
  43 #include "packet.h"
  44 #include "dh.h"
  45
  46 #include "ssh-gss.h"
  47
  48 void
  49 kexgss_client(Kex *kex) {
  50         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
  51         gss_buffer_desc recv_tok, gssbuf, msg_tok, *token_ptr;
  52         Gssctxt *ctxt;
  53         OM_uint32 maj_status, min_status, ret_flags;
  54         u_int klen, kout, slen = 0, hashlen, strlen;
  55         DH *dh;
  56         BIGNUM *dh_server_pub = NULL;
  57         BIGNUM *shared_secret = NULL;
  58         BIGNUM *p = NULL;
  59         BIGNUM *g = NULL;
  60         u_char *kbuf, *hash;
  61         u_char *serverhostkey = NULL;
  62         char *msg;
  63         char *lang;
  64         int type = 0;
  65         int first = 1;
  66         int nbits = 0, min = DH_GRP_MIN, max = DH_GRP_MAX;
  67
  68         /* Initialise our GSSAPI world */
  69         ssh_gssapi_build_ctx(&ctxt);
  70         if (ssh_gssapi_id_kex(ctxt, kex->name, kex->kex_type)
  71             == GSS_C_NO_OID)
  72                 fatal("Couldn't identify host exchange");
  73
  74         if (ssh_gssapi_import_name(ctxt, kex->gss_host))
  75                 fatal("Couldn't import hostname");
  76
  77         switch (kex->kex_type) {
  78         case KEX_GSS_GRP1_SHA1:
  79                 dh = dh_new_group1();
  80                 break;
  81         case KEX_GSS_GRP14_SHA1:
  82                 dh = dh_new_group14();
  83                 break;
  84         case KEX_GSS_GEX_SHA1:
  85                 debug("Doing group exchange\n");
  86                 nbits = dh_estimate(kex->we_need * 8);
  87                 packet_start(SSH2_MSG_KEXGSS_GROUPREQ);
  88                 packet_put_int(min);
  89                 packet_put_int(nbits);
  90                 packet_put_int(max);
  91
  92                 packet_send();
  93
  94                 packet_read_expect(SSH2_MSG_KEXGSS_GROUP);
  95
  96                 if ((p = BN_new()) == NULL)
  97                         fatal("BN_new() failed");
  98                 packet_get_bignum2(p);
  99                 if ((g = BN_new()) == NULL)
 100                         fatal("BN_new() failed");
 101                 packet_get_bignum2(g);
 102                 packet_check_eom();
 103
 104                 if (BN_num_bits(p) < min || BN_num_bits(p) > max)
 105                         fatal("GSSGRP_GEX group out of range: %d !< %d !< %d",
 106                             min, BN_num_bits(p), max);
 107
 108                 dh = dh_new_group(g, p);
 109                 break;
 110         default:
 111                 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
 112         }
 113
 114         /* Step 1 - e is dh->pub_key */
 115         dh_gen_key(dh, kex->we_need * 8);
 116
 117         /* This is f, we initialise it now to make life easier */
 118         dh_server_pub = BN_new();
 119         if (dh_server_pub == NULL)
 120                 fatal("dh_server_pub == NULL");
 121
 122         token_ptr = GSS_C_NO_BUFFER;
 123
 124         do {
 125                 debug("Calling gss_init_sec_context");
 126
 127                 maj_status = ssh_gssapi_init_ctx(ctxt,
 128                     kex->gss_deleg_creds, token_ptr, &send_tok,
 129                     &ret_flags);
 130
 131                 if (GSS_ERROR(maj_status)) {
 132                         if (send_tok.length != 0) {
 133                                 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
 134                                 packet_put_string(send_tok.value,
 135                                     send_tok.length);
 136                         }
 137                         fatal("gss_init_context failed");
 138                 }
 139
 140                 /* If we've got an old receive buffer get rid of it */
 141                 if (token_ptr != GSS_C_NO_BUFFER)
 142                         xfree(recv_tok.value);
 143
 144                 if (maj_status == GSS_S_COMPLETE) {
 145                         /* If mutual state flag is not true, kex fails */
 146                         if (!(ret_flags & GSS_C_MUTUAL_FLAG))
 147                                 fatal("Mutual authentication failed");
 148
 149                         /* If integ avail flag is not true kex fails */
 150                         if (!(ret_flags & GSS_C_INTEG_FLAG))
 151                                 fatal("Integrity check failed");
 152                 }
 153
 154                 /*
 155                  * If we have data to send, then the last message that we
 156                  * received cannot have been a 'complete'.
 157                  */
 158                 if (send_tok.length != 0) {
 159                         if (first) {
 160                                 packet_start(SSH2_MSG_KEXGSS_INIT);
 161                                 packet_put_string(send_tok.value,
 162                                     send_tok.length);
 163                                 packet_put_bignum2(dh->pub_key);
 164                                 first = 0;
 165                         } else {
 166                                 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
 167                                 packet_put_string(send_tok.value,
 168                                     send_tok.length);
 169                         }
 170                         packet_send();
 171                         gss_release_buffer(&min_status, &send_tok);
 172
 173                         /* If we've sent them data, they should reply */
 174                         do {
 175                                 type = packet_read();
 176                                 if (type == SSH2_MSG_KEXGSS_HOSTKEY) {
 177                                         debug("Received KEXGSS_HOSTKEY");
 178                                         if (serverhostkey)
 179                                                 fatal("Server host key received more than once");
 180                                         serverhostkey =
 181                                             packet_get_string(&slen);
 182                                 }
 183                         } while (type == SSH2_MSG_KEXGSS_HOSTKEY);
 184
 185                         switch (type) {
 186                         case SSH2_MSG_KEXGSS_CONTINUE:
 187                                 debug("Received GSSAPI_CONTINUE");
 188                                 if (maj_status == GSS_S_COMPLETE)
 189                                         fatal("GSSAPI Continue received from server when complete");
 190                                 recv_tok.value = packet_get_string(&strlen);
 191                                 recv_tok.length = strlen;
 192                                 break;
 193                         case SSH2_MSG_KEXGSS_COMPLETE:
 194                                 debug("Received GSSAPI_COMPLETE");
 195                                 packet_get_bignum2(dh_server_pub);
 196                                 msg_tok.value =  packet_get_string(&strlen);
 197                                 msg_tok.length = strlen;
 198
 199                                 /* Is there a token included? */
 200                                 if (packet_get_char()) {
 201                                         recv_tok.value=
 202                                             packet_get_string(&strlen);
 203                                         recv_tok.length = strlen;
 204                                         /* If we're already complete - protocol error */
 205                                         if (maj_status == GSS_S_COMPLETE)
 206                                                 packet_disconnect("Protocol error: received token when complete");
 207                                         } else {
 208                                                 /* No token included */
 209                                                 if (maj_status != GSS_S_COMPLETE)
 210                                                         packet_disconnect("Protocol error: did not receive final token");
 211                                 }
 212                                 break;
 213                         case SSH2_MSG_KEXGSS_ERROR:
 214                                 debug("Received Error");
 215                                 maj_status = packet_get_int();
 216                                 min_status = packet_get_int();
 217                                 msg = packet_get_string(NULL);
 218                                 lang = packet_get_string(NULL);
 219                                 fatal("GSSAPI Error: \n%.400s",msg);
 220                         default:
 221                                 packet_disconnect("Protocol error: didn't expect packet type %d",
 222                                 type);
 223                         }
 224                         token_ptr = &recv_tok;
 225                 } else {
 226                         /* No data, and not complete */
 227                         if (maj_status != GSS_S_COMPLETE)
 228                                 fatal("Not complete, and no token output");
 229                 }
 230         } while (maj_status & GSS_S_CONTINUE_NEEDED);
 231
 232         /*
 233          * We _must_ have received a COMPLETE message in reply from the
 234          * server, which will have set dh_server_pub and msg_tok
 235          */
 236
 237         if (type != SSH2_MSG_KEXGSS_COMPLETE)
 238                 fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it");
 239
 240         /* Check f in range [1, p-1] */
 241         if (!dh_pub_is_valid(dh, dh_server_pub))
 242                 packet_disconnect("bad server public DH value");
 243
 244         /* compute K=f^x mod p */
 245         klen = DH_size(dh);
 246         kbuf = xmalloc(klen);
 247         kout = DH_compute_key(kbuf, dh_server_pub, dh);
 248
 249         shared_secret = BN_new();
 250         BN_bin2bn(kbuf,kout, shared_secret);
 251         memset(kbuf, 0, klen);
 252         xfree(kbuf);
 253
 254         switch (kex->kex_type) {
 255         case KEX_GSS_GRP1_SHA1:
 256         case KEX_GSS_GRP14_SHA1:
 257                 kex_dh_hash( kex->client_version_string,
 258                     kex->server_version_string,
 259                     buffer_ptr(&kex->my), buffer_len(&kex->my),
 260                     buffer_ptr(&kex->peer), buffer_len(&kex->peer),
 261                     serverhostkey, slen, /* server host key */
 262                     dh->pub_key,        /* e */
 263                     dh_server_pub,      /* f */
 264                     shared_secret,      /* K */
 265                     &hash, &hashlen
 266                 );
 267                 break;
 268         case KEX_GSS_GEX_SHA1:
 269                 kexgex_hash(
 270                     kex->evp_md,
 271                     kex->client_version_string,
 272                     kex->server_version_string,
 273                     buffer_ptr(&kex->my), buffer_len(&kex->my),
 274                     buffer_ptr(&kex->peer), buffer_len(&kex->peer),
 275                     serverhostkey, slen,
 276                     min, nbits, max,
 277                     dh->p, dh->g,
 278                     dh->pub_key,
 279                     dh_server_pub,
 280                     shared_secret,
 281                     &hash, &hashlen
 282                 );
 283                 break;
 284         default:
 285                 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
 286         }
 287
 288         gssbuf.value = hash;
 289         gssbuf.length = hashlen;
 290
 291         /* Verify that the hash matches the MIC we just got. */
 292         if (GSS_ERROR(ssh_gssapi_checkmic(ctxt, &gssbuf, &msg_tok)))
 293                 packet_disconnect("Hash's MIC didn't verify");
 294
 295         xfree(msg_tok.value);
 296
 297         DH_free(dh);
 298         if (serverhostkey)
 299                 xfree(serverhostkey);
 300         BN_clear_free(dh_server_pub);
 301
 302         /* save session id */
 303         if (kex->session_id == NULL) {
 304                 kex->session_id_len = hashlen;
 305                 kex->session_id = xmalloc(kex->session_id_len);
 306                 memcpy(kex->session_id, hash, kex->session_id_len);
 307         }
 308
 309         if (gss_kex_context == NULL)
 310                 gss_kex_context = ctxt;
 311         else
 312                 ssh_gssapi_delete_ctx(&ctxt);
 313
 314         kex_derive_keys(kex, hash, hashlen, shared_secret);
 315         BN_clear_free(shared_secret);
 316         kex_finish(kex);
 317 }
 318
 319 #endif /* GSSAPI */