openssh/kexgssc.c

   1 /*
   2  * Copyright (c) 2001,2002 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 <openssl/crypto.h>
  30 #include <openssl/bn.h>
  31
  32 #include "xmalloc.h"
  33 #include "buffer.h"
  34 #include "bufaux.h"
  35 #include "kex.h"
  36 #include "log.h"
  37 #include "packet.h"
  38 #include "dh.h"
  39 #include "ssh2.h"
  40 #include "ssh-gss.h"
  41 #include "canohost.h"
  42
  43
  44 void
  45 kexgss_client(Kex *kex)
  46 {
  47         gss_buffer_desc gssbuf,send_tok,recv_tok, msg_tok, *token_ptr;
  48         Gssctxt *ctxt;
  49         OM_uint32 maj_status, min_status, ret_flags;
  50         unsigned int klen, kout;
  51         DH *dh;
  52         BIGNUM *dh_server_pub = 0;
  53         BIGNUM *shared_secret = 0;
  54         unsigned char *kbuf;
  55         unsigned char *hash;
  56         unsigned char *serverhostkey;
  57         char *msg;
  58         char *lang;
  59         int type = 0;
  60         int first = 1;
  61         int slen = 0, strlen;
  62
  63         /* Initialise our GSSAPI world */
  64         ssh_gssapi_build_ctx(&ctxt);
  65         if (ssh_gssapi_client_id_kex(ctxt,kex->name)==NULL) {
  66                 fatal("Couldn't identify host exchange");
  67         }
  68         if (ssh_gssapi_import_name(ctxt,get_canonical_hostname(1))) {
  69                 fatal("Couldn't import hostname ");
  70         }
  71
  72         /* This code should match that in ssh_dh1_client */
  73
  74         /* Step 1 - e is dh->pub_key */
  75         dh = dh_new_group1();
  76         dh_gen_key(dh, kex->we_need * 8);
  77
  78         /* This is f, we initialise it now to make life easier */
  79         dh_server_pub = BN_new();
  80         if (dh_server_pub == NULL) {
  81                 fatal("dh_server_pub == NULL");
  82         }
  83
  84         token_ptr = GSS_C_NO_BUFFER;
  85
  86         do {
  87                 debug("Calling gss_init_sec_context");
  88
  89                 maj_status=ssh_gssapi_init_ctx(ctxt,
  90                                                kex->options.gss_deleg_creds,
  91                                                token_ptr,&send_tok,
  92                                                &ret_flags);
  93
  94                 if (GSS_ERROR(maj_status)) {
  95                         fatal("gss_init_context failed");
  96                 }
  97
  98                 /* If we've got an old receive buffer get rid of it */
  99                 if (token_ptr != GSS_C_NO_BUFFER)
 100                         (void) gss_release_buffer(&min_status, &recv_tok);
 101
 102
 103                 if (maj_status == GSS_S_COMPLETE) {
 104                         /* If mutual state flag is not true, kex fails */
 105                         if (!(ret_flags & GSS_C_MUTUAL_FLAG)) {
 106                                 fatal("Mutual authentication failed");
 107                         }
 108                         /* If integ avail flag is not true kex fails */
 109                         if (!(ret_flags & GSS_C_INTEG_FLAG)) {
 110                                 fatal("Integrity check failed");
 111                         }
 112                 }
 113
 114                 /* If we have data to send, then the last message that we
 115                  * received cannot have been a 'complete'. */
 116                 if (send_tok.length !=0) {
 117                         if (first) {
 118                                 packet_start(SSH2_MSG_KEXGSS_INIT);
 119                                 packet_put_string(send_tok.value,
 120                                                   send_tok.length);
 121                                 packet_put_bignum2(dh->pub_key);
 122                                 first=0;
 123                         } else {
 124                                 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
 125                                 packet_put_string(send_tok.value,
 126                                                   send_tok.length);
 127                         }
 128                         packet_send();
 129                         packet_write_wait();
 130
 131
 132                         /* If we've sent them data, they'd better be polite
 133                          * and reply. */
 134
 135                         type = packet_read();
 136                         switch (type) {
 137                         case SSH2_MSG_KEXGSS_HOSTKEY:
 138                                 debug("Received KEXGSS_HOSTKEY");
 139                                 serverhostkey=packet_get_string(&slen);
 140                                 break;
 141                         case SSH2_MSG_KEXGSS_CONTINUE:
 142                                 debug("Received GSSAPI_CONTINUE");
 143                                 if (maj_status == GSS_S_COMPLETE)
 144                                         fatal("GSSAPI Continue received from server when complete");
 145                                 recv_tok.value=packet_get_string(&strlen);
 146                                 recv_tok.length=strlen; /* int vs. size_t */
 147                                 break;
 148                         case SSH2_MSG_KEXGSS_COMPLETE:
 149                                 debug("Received GSSAPI_COMPLETE");
 150                                 packet_get_bignum2(dh_server_pub);
 151                                 msg_tok.value=packet_get_string(&strlen);
 152                                 msg_tok.length=strlen; /* int vs. size_t */
 153
 154                                 /* Is there a token included? */
 155                                 if (packet_get_char()) {
 156                                         recv_tok.value=
 157                                             packet_get_string(&strlen);
 158                                         recv_tok.length=strlen; /*int/size_t*/
 159                                         /* If we're already complete - protocol error */
 160                                         if (maj_status == GSS_S_COMPLETE)
 161                                                 packet_disconnect("Protocol error: received token when complete");
 162                                 } else {
 163                                         /* No token included */
 164                                         if (maj_status != GSS_S_COMPLETE)
 165                                                 packet_disconnect("Protocol error: did not receive final token");
 166                                 }
 167                                 break;
 168                         case SSH2_MSG_KEXGSS_ERROR:
 169                                 debug("Received Error");
 170                                 maj_status=packet_get_int();
 171                                 min_status=packet_get_int();
 172                                 msg=packet_get_string(NULL);
 173                                 lang=packet_get_string(NULL);
 174                                 fatal(msg);
 175                         default:
 176                                 packet_disconnect("Protocol error: didn't expect packet type %d",
 177                                 type);
 178                         }
 179                         token_ptr=&recv_tok;
 180                 }
 181
 182         } while (maj_status & GSS_S_CONTINUE_NEEDED);
 183
 184         /* We _must_ have received a COMPLETE message in reply from the
 185          * server, which will have set dh_server_pub and msg_tok */
 186
 187         if (type!=SSH2_MSG_KEXGSS_COMPLETE)
 188            fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it");
 189
 190         /* Check f in range [1, p-1] */
 191         if (!dh_pub_is_valid(dh, dh_server_pub))
 192                         packet_disconnect("bad server public DH value");
 193
 194         /* compute K=f^x mod p */
 195         klen = DH_size(dh);
 196         kbuf = xmalloc(klen);
 197         kout = DH_compute_key(kbuf, dh_server_pub, dh);
 198
 199         shared_secret = BN_new();
 200         BN_bin2bn(kbuf,kout, shared_secret);
 201         memset(kbuf, 0, klen);
 202         xfree(kbuf);
 203
 204         /* The GSS hash is identical to the DH one */
 205         hash = kex_dh_hash(
 206             kex->client_version_string,
 207             kex->server_version_string,
 208             buffer_ptr(&kex->my), buffer_len(&kex->my),
 209             buffer_ptr(&kex->peer), buffer_len(&kex->peer),
 210             serverhostkey, slen, /* server host key */
 211             dh->pub_key,        /* e */
 212             dh_server_pub,      /* f */
 213             shared_secret       /* K */
 214         );
 215
 216         gssbuf.value=hash;
 217         gssbuf.length=20;
 218
 219         /* Verify that H matches the token we just got. */
 220                 if ((maj_status = gss_verify_mic(&min_status,
 221                                          ctxt->context,
 222                                          &gssbuf,
 223                                          &msg_tok,
 224                                          NULL))) {
 225
 226                 packet_disconnect("Hash's MIC didn't verify");
 227         }
 228
 229         DH_free(dh);
 230         ssh_gssapi_delete_ctx(&ctxt);
 231         /* save session id */
 232         if (kex->session_id == NULL) {
 233                 kex->session_id_len = 20;
 234                 kex->session_id = xmalloc(kex->session_id_len);
 235                 memcpy(kex->session_id, hash, kex->session_id_len);
 236         }
 237
 238         kex_derive_keys(kex, hash, shared_secret);
 239         BN_clear_free(shared_secret);
 240         kex_finish(kex);
 241 }
 242
 243 #endif /* GSSAPI */