openssh/kexgssc.c

   1 /*
   2  * Copyright (c) 2001-2003 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 "canohost.h"
  40 #include "ssh2.h"
  41 #include "ssh-gss.h"
  42
  43 void
  44 kexgss_client(Kex *kex)
  45 {
  46         gss_buffer_desc gssbuf,send_tok,recv_tok, msg_tok, *token_ptr;
  47         Gssctxt *ctxt;
  48         OM_uint32 maj_status, min_status, ret_flags;
  49         unsigned int klen, kout;
  50         DH *dh;
  51         BIGNUM *dh_server_pub = 0;
  52         BIGNUM *shared_secret = 0;
  53         unsigned char *kbuf;
  54         unsigned char *hash;
  55         unsigned char *serverhostkey;
  56         char *msg;
  57         char *lang;
  58         int type = 0;
  59         int first = 1;
  60         int slen = 0;
  61         u_int 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
  69         if (ssh_gssapi_import_name(ctxt,get_canonical_hostname(1))) {
  70                 fatal("Couldn't import hostname ");
  71         }
  72
  73         /* This code should match that in ssh_dh1_client */
  74
  75         /* Step 1 - e is dh->pub_key */
  76         dh = dh_new_group1();
  77         dh_gen_key(dh, kex->we_need * 8);
  78
  79         /* This is f, we initialise it now to make life easier */
  80         dh_server_pub = BN_new();
  81         if (dh_server_pub == NULL) {
  82                 fatal("dh_server_pub == NULL");
  83         }
  84
  85         token_ptr = GSS_C_NO_BUFFER;
  86
  87         do {
  88                 debug("Calling gss_init_sec_context");
  89
  90                 maj_status=ssh_gssapi_init_ctx(ctxt,
  91                                                kex->options.gss_deleg_creds,
  92                                                token_ptr,&send_tok,
  93                                                &ret_flags);
  94
  95                 if (GSS_ERROR(maj_status)) {
  96                         if (send_tok.length!=0) {
  97                                 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
  98                                 packet_put_string(send_tok.value,
  99                                                   send_tok.length);
 100                         }
 101                         fatal("gss_init_context failed");
 102                 }
 103
 104                 /* If we've got an old receive buffer get rid of it */
 105                 if (token_ptr != GSS_C_NO_BUFFER)
 106                         (void) gss_release_buffer(&min_status, &recv_tok);
 107
 108
 109                 if (maj_status == GSS_S_COMPLETE) {
 110                         /* If mutual state flag is not true, kex fails */
 111                         if (!(ret_flags & GSS_C_MUTUAL_FLAG)) {
 112                                 fatal("Mutual authentication failed");
 113                         }
 114                         /* If integ avail flag is not true kex fails */
 115                         if (!(ret_flags & GSS_C_INTEG_FLAG)) {
 116                                 fatal("Integrity check failed");
 117                         }
 118                 }
 119
 120                 /* If we have data to send, then the last message that we
 121                  * received cannot have been a 'complete'. */
 122                 if (send_tok.length !=0) {
 123                         if (first) {
 124                                 packet_start(SSH2_MSG_KEXGSS_INIT);
 125                                 packet_put_string(send_tok.value,
 126                                                   send_tok.length);
 127                                 packet_put_bignum2(dh->pub_key);
 128                                 first=0;
 129                         } else {
 130                                 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
 131                                 packet_put_string(send_tok.value,
 132                                                   send_tok.length);
 133                         }
 134                         packet_send();
 135                         packet_write_wait();
 136
 137
 138                         /* If we've sent them data, they'd better be polite
 139                          * and reply. */
 140
 141                         type = packet_read();
 142                         switch (type) {
 143                         case SSH2_MSG_KEXGSS_HOSTKEY:
 144                                 debug("Received KEXGSS_HOSTKEY");
 145                                 serverhostkey=packet_get_string(&slen);
 146                                 break;
 147                         case SSH2_MSG_KEXGSS_CONTINUE:
 148                                 debug("Received GSSAPI_CONTINUE");
 149                                 if (maj_status == GSS_S_COMPLETE)
 150                                         fatal("GSSAPI Continue received from server when complete");
 151                                 recv_tok.value=packet_get_string(&strlen);
 152                                 recv_tok.length=strlen; /* u_int vs. size_t */
 153                                 break;
 154                         case SSH2_MSG_KEXGSS_COMPLETE:
 155                                 debug("Received GSSAPI_COMPLETE");
 156                                 packet_get_bignum2(dh_server_pub);
 157                                 msg_tok.value=packet_get_string(&strlen);
 158                                 msg_tok.length=strlen; /* u_int vs. size_t */
 159
 160                                 /* Is there a token included? */
 161                                 if (packet_get_char()) {
 162                                         recv_tok.value=
 163                                             packet_get_string(&strlen);
 164                                         recv_tok.length=strlen; /*u_int/size_t*/
 165                                         /* If we're already complete - protocol error */
 166                                         if (maj_status == GSS_S_COMPLETE)
 167                                                 packet_disconnect("Protocol error: received token when complete");
 168                                 } else {
 169                                         /* No token included */
 170                                         if (maj_status != GSS_S_COMPLETE)
 171                                                 packet_disconnect("Protocol error: did not receive final token");
 172                                 }
 173                                 break;
 174                         case SSH2_MSG_KEXGSS_ERROR:
 175                                 debug("Received Error");
 176                                 maj_status=packet_get_int();
 177                                 min_status=packet_get_int();
 178                                 msg=packet_get_string(NULL);
 179                                 lang=packet_get_string(NULL);
 180                                 fprintf(stderr,"GSSAPI Error: \n%s",msg);
 181                         default:
 182                                 packet_disconnect("Protocol error: didn't expect packet type %d",
 183                                 type);
 184                         }
 185                         token_ptr=&recv_tok;
 186                 } else {
 187                         /* No data, and not complete */
 188                         if (maj_status!=GSS_S_COMPLETE) {
 189                                 fatal("Not complete, and no token output");
 190                         }
 191                 }
 192         } while (maj_status & GSS_S_CONTINUE_NEEDED);
 193
 194         /* We _must_ have received a COMPLETE message in reply from the
 195          * server, which will have set dh_server_pub and msg_tok */
 196
 197         if (type!=SSH2_MSG_KEXGSS_COMPLETE)
 198            fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it");
 199
 200         /* Check f in range [1, p-1] */
 201         if (!dh_pub_is_valid(dh, dh_server_pub))
 202                         packet_disconnect("bad server public DH value");
 203
 204         /* compute K=f^x mod p */
 205         klen = DH_size(dh);
 206         kbuf = xmalloc(klen);
 207         kout = DH_compute_key(kbuf, dh_server_pub, dh);
 208
 209         shared_secret = BN_new();
 210         BN_bin2bn(kbuf,kout, shared_secret);
 211         memset(kbuf, 0, klen);
 212         xfree(kbuf);
 213
 214         /* The GSS hash is identical to the DH one */
 215         hash = kex_dh_hash(
 216             kex->client_version_string,
 217             kex->server_version_string,
 218             buffer_ptr(&kex->my), buffer_len(&kex->my),
 219             buffer_ptr(&kex->peer), buffer_len(&kex->peer),
 220             serverhostkey, slen, /* server host key */
 221             dh->pub_key,        /* e */
 222             dh_server_pub,      /* f */
 223             shared_secret       /* K */
 224         );
 225
 226         gssbuf.value=hash;
 227         gssbuf.length=20;
 228
 229         /* Verify that H matches the token we just got. */
 230                 if ((maj_status = gss_verify_mic(&min_status,
 231                                          ctxt->context,
 232                                          &gssbuf,
 233                                          &msg_tok,
 234                                          NULL))) {
 235
 236                 packet_disconnect("Hash's MIC didn't verify");
 237         }
 238
 239         DH_free(dh);
 240         ssh_gssapi_delete_ctx(&ctxt);
 241         /* save session id */
 242         if (kex->session_id == NULL) {
 243                 kex->session_id_len = 20;
 244                 kex->session_id = xmalloc(kex->session_id_len);
 245                 memcpy(kex->session_id, hash, kex->session_id_len);
 246         }
 247
 248         kex_derive_keys(kex, hash, shared_secret);
 249         BN_clear_free(shared_secret);
 250         kex_finish(kex);
 251 }
 252
 253 #endif /* GSSAPI */