crypto/openssh/auth2-gss.c

   1 /* $OpenBSD: auth2-gss.c,v 1.26 2017/06/24 06:34:38 djm Exp $ */
   2
   3 /*
   4  * Copyright (c) 2001-2003 Simon Wilkinson. 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 #ifdef GSSAPI
  30
  31 #include <sys/types.h>
  32
  33 #include <stdarg.h>
  34
  35 #include "xmalloc.h"
  36 #include "key.h"
  37 #include "hostfile.h"
  38 #include "auth.h"
  39 #include "ssh2.h"
  40 #include "log.h"
  41 #include "dispatch.h"
  42 #include "buffer.h"
  43 #include "misc.h"
  44 #include "servconf.h"
  45 #include "packet.h"
  46 #include "ssh-gss.h"
  47 #include "monitor_wrap.h"
  48
  49 extern ServerOptions options;
  50
  51 static int input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh);
  52 static int input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh);
  53 static int input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh);
  54 static int input_gssapi_errtok(int, u_int32_t, struct ssh *);
  55
  56 /*
  57  * We only support those mechanisms that we know about (ie ones that we know
  58  * how to check local user kuserok and the like)
  59  */
  60 static int
  61 userauth_gssapi(struct ssh *ssh)
  62 {
  63         Authctxt *authctxt = ssh->authctxt;
  64         gss_OID_desc goid = {0, NULL};
  65         Gssctxt *ctxt = NULL;
  66         int mechs;
  67         int present;
  68         OM_uint32 ms;
  69         u_int len;
  70         u_char *doid = NULL;
  71
  72         if (!authctxt->valid || authctxt->user == NULL)
  73                 return (0);
  74
  75         mechs = packet_get_int();
  76         if (mechs == 0) {
  77                 debug("Mechanism negotiation is not supported");
  78                 return (0);
  79         }
  80
  81         do {
  82                 mechs--;
  83
  84                 free(doid);
  85
  86                 present = 0;
  87                 doid = packet_get_string(&len);
  88
  89                 if (len > 2 && doid[0] == SSH_GSS_OIDTYPE &&
  90                     doid[1] == len - 2) {
  91                         goid.elements = doid + 2;
  92                         goid.length   = len - 2;
  93                         ssh_gssapi_test_oid_supported(&ms, &goid, &present);
  94                 } else {
  95                         logit("Badly formed OID received");
  96                 }
  97         } while (mechs > 0 && !present);
  98
  99         if (!present) {
 100                 free(doid);
 101                 authctxt->server_caused_failure = 1;
 102                 return (0);
 103         }
 104
 105         if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
 106                 if (ctxt != NULL)
 107                         ssh_gssapi_delete_ctx(&ctxt);
 108                 free(doid);
 109                 authctxt->server_caused_failure = 1;
 110                 return (0);
 111         }
 112
 113         authctxt->methoddata = (void *)ctxt;
 114
 115         packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
 116
 117         /* Return the OID that we received */
 118         packet_put_string(doid, len);
 119
 120         packet_send();
 121         free(doid);
 122
 123         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
 124         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
 125         authctxt->postponed = 1;
 126
 127         return (0);
 128 }
 129
 130 static int
 131 input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh)
 132 {
 133         Authctxt *authctxt = ssh->authctxt;
 134         Gssctxt *gssctxt;
 135         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 136         gss_buffer_desc recv_tok;
 137         OM_uint32 maj_status, min_status, flags;
 138         u_int len;
 139
 140         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 141                 fatal("No authentication or GSSAPI context");
 142
 143         gssctxt = authctxt->methoddata;
 144         recv_tok.value = packet_get_string(&len);
 145         recv_tok.length = len; /* u_int vs. size_t */
 146
 147         packet_check_eom();
 148
 149         maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 150             &send_tok, &flags));
 151
 152         free(recv_tok.value);
 153
 154         if (GSS_ERROR(maj_status)) {
 155                 if (send_tok.length != 0) {
 156                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
 157                         packet_put_string(send_tok.value, send_tok.length);
 158                         packet_send();
 159                 }
 160                 authctxt->postponed = 0;
 161                 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 162                 userauth_finish(ssh, 0, "gssapi-with-mic", NULL);
 163         } else {
 164                 if (send_tok.length != 0) {
 165                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
 166                         packet_put_string(send_tok.value, send_tok.length);
 167                         packet_send();
 168                 }
 169                 if (maj_status == GSS_S_COMPLETE) {
 170                         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 171                         if (flags & GSS_C_INTEG_FLAG)
 172                                 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC,
 173                                     &input_gssapi_mic);
 174                         else
 175                                 ssh_dispatch_set(ssh,
 176                                     SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
 177                                     &input_gssapi_exchange_complete);
 178                 }
 179         }
 180
 181         gss_release_buffer(&min_status, &send_tok);
 182         return 0;
 183 }
 184
 185 static int
 186 input_gssapi_errtok(int type, u_int32_t plen, struct ssh *ssh)
 187 {
 188         Authctxt *authctxt = ssh->authctxt;
 189         Gssctxt *gssctxt;
 190         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 191         gss_buffer_desc recv_tok;
 192         OM_uint32 maj_status;
 193         u_int len;
 194
 195         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 196                 fatal("No authentication or GSSAPI context");
 197
 198         gssctxt = authctxt->methoddata;
 199         recv_tok.value = packet_get_string(&len);
 200         recv_tok.length = len;
 201
 202         packet_check_eom();
 203
 204         /* Push the error token into GSSAPI to see what it says */
 205         maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 206             &send_tok, NULL));
 207
 208         free(recv_tok.value);
 209
 210         /* We can't return anything to the client, even if we wanted to */
 211         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 212         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 213
 214         /* The client will have already moved on to the next auth */
 215
 216         gss_release_buffer(&maj_status, &send_tok);
 217         return 0;
 218 }
 219
 220 /*
 221  * This is called when the client thinks we've completed authentication.
 222  * It should only be enabled in the dispatch handler by the function above,
 223  * which only enables it once the GSSAPI exchange is complete.
 224  */
 225
 226 static int
 227 input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh)
 228 {
 229         Authctxt *authctxt = ssh->authctxt;
 230         int authenticated;
 231         const char *displayname;
 232
 233         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 234                 fatal("No authentication or GSSAPI context");
 235
 236         /*
 237          * We don't need to check the status, because we're only enabled in
 238          * the dispatcher once the exchange is complete
 239          */
 240
 241         packet_check_eom();
 242
 243         authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 244
 245         if ((!use_privsep || mm_is_monitor()) &&
 246             (displayname = ssh_gssapi_displayname()) != NULL)
 247                 auth2_record_info(authctxt, "%s", displayname);
 248
 249         authctxt->postponed = 0;
 250         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 251         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 252         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
 253         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 254         userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL);
 255         return 0;
 256 }
 257
 258 static int
 259 input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh)
 260 {
 261         Authctxt *authctxt = ssh->authctxt;
 262         Gssctxt *gssctxt;
 263         int authenticated = 0;
 264         Buffer b;
 265         gss_buffer_desc mic, gssbuf;
 266         u_int len;
 267         const char *displayname;
 268
 269         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 270                 fatal("No authentication or GSSAPI context");
 271
 272         gssctxt = authctxt->methoddata;
 273
 274         mic.value = packet_get_string(&len);
 275         mic.length = len;
 276
 277         ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service,
 278             "gssapi-with-mic");
 279
 280         gssbuf.value = buffer_ptr(&b);
 281         gssbuf.length = buffer_len(&b);
 282
 283         if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
 284                 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 285         else
 286                 logit("GSSAPI MIC check failed");
 287
 288         buffer_free(&b);
 289         free(mic.value);
 290
 291         if ((!use_privsep || mm_is_monitor()) &&
 292             (displayname = ssh_gssapi_displayname()) != NULL)
 293                 auth2_record_info(authctxt, "%s", displayname);
 294
 295         authctxt->postponed = 0;
 296         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 297         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 298         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
 299         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 300         userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL);
 301         return 0;
 302 }
 303
 304 Authmethod method_gssapi = {
 305         "gssapi-with-mic",
 306         userauth_gssapi,
 307         &options.gss_authentication
 308 };
 309
 310 #endif /* GSSAPI */