openssh/auth2-gss.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 #include "auth.h"
  29 #include "ssh2.h"
  30 #include "ssh1.h"
  31 #include "xmalloc.h"
  32 #include "log.h"
  33 #include "dispatch.h"
  34 #include "servconf.h"
  35 #include "compat.h"
  36 #include "packet.h"
  37 #include "monitor_wrap.h"
  38
  39 #include "ssh-gss.h"
  40
  41 extern ServerOptions options;
  42 unsigned char ssh1_key_digest[16];
  43
  44 static int
  45 userauth_external(Authctxt *authctxt)
  46 {
  47         packet_check_eom();
  48
  49         return(PRIVSEP(ssh_gssapi_userok(authctxt->user)));
  50 }
  51
  52 static void ssh_gssapi_userauth_error(Gssctxt *ctxt);
  53 static void input_gssapi_token(int type, u_int32_t plen, void *ctxt);
  54 static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt);
  55 static void input_gssapi_errtok(int, u_int32_t, void *);
  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(Authctxt *authctxt)
  62 {
  63         gss_OID_desc    oid= {0,NULL};
  64         Gssctxt         *ctxt = NULL;
  65         int             mechs;
  66         gss_OID_set     supported;
  67         int             present;
  68         OM_uint32       ms;
  69         u_int           len;
  70         char *          doid = NULL;
  71
  72         if (!authctxt->valid || authctxt->user == NULL)
  73                 return 0;
  74
  75         if (datafellows & SSH_OLD_GSSAPI) {
  76                 debug("Early drafts of GSSAPI userauth not supported");
  77                 return 0;
  78         }
  79
  80         mechs=packet_get_int();
  81         if (mechs==0) {
  82                 debug("Mechanism negotiation is not supported");
  83                 return 0;
  84         }
  85
  86         ssh_gssapi_supported_oids(&supported);
  87         do {
  88                 mechs--;
  89
  90                 if (doid)
  91                         xfree(doid);
  92
  93                 debug("Trying to get OID string");
  94                 doid = packet_get_string(&len);
  95                 debug("Got string");
  96
  97                 if (doid[0]!=0x06 || doid[1]!=len-2) {
  98                         log("Mechanism OID received using the old encoding form");
  99                         oid.elements = doid;
 100                         oid.length = len;
 101                 } else {
 102                         oid.elements = doid + 2;
 103                         oid.length   = len - 2;
 104                 }
 105                 gss_test_oid_set_member(&ms, &oid, supported, &present);
 106         } while (mechs>0 && !present);
 107
 108         if (!present) {
 109                 xfree(doid);
 110                 return(0);
 111         }
 112
 113         if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt,&oid)))) {
 114                 ssh_gssapi_userauth_error(ctxt);
 115                 return(0);
 116         }
 117
 118         authctxt->methoddata=(void *)ctxt;
 119
 120         /* Send SSH_MSG_USERAUTH_GSSAPI_RESPONSE */
 121
 122         if (!compat20) {
 123
 124         packet_start(SSH_SMSG_AUTH_GSSAPI_RESPONSE);
 125         packet_put_string(oid.elements,oid.length);
 126
 127         } else {
 128
 129         packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
 130
 131         /* Just return whatever they sent */
 132         packet_put_string(doid,len);
 133
 134         } /* !compat20 */
 135
 136         packet_send();
 137         packet_write_wait();
 138         xfree(doid);
 139
 140         if (!compat20)
 141         dispatch_set(SSH_MSG_AUTH_GSSAPI_TOKEN,
 142                                 &input_gssapi_token);
 143         else
 144         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN,
 145                      &input_gssapi_token);
 146         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK,
 147                      &input_gssapi_errtok);
 148         authctxt->postponed = 1;
 149
 150         return 0;
 151 }
 152
 153 static void
 154 input_gssapi_token(int type, u_int32_t plen, void *ctxt)
 155 {
 156         Authctxt *authctxt = ctxt;
 157         Gssctxt *gssctxt;
 158         gss_buffer_desc send_tok,recv_tok;
 159         OM_uint32 maj_status, min_status;
 160         u_int len;
 161
 162         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 163                 fatal("No authentication or GSSAPI context");
 164
 165         gssctxt=authctxt->methoddata;
 166         recv_tok.value=packet_get_string(&len);
 167         recv_tok.length=len; /* u_int vs. size_t */
 168
 169         maj_status=PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 170                                                  &send_tok, NULL));
 171         packet_check_eom();
 172
 173         if (GSS_ERROR(maj_status)) {
 174                 ssh_gssapi_userauth_error(gssctxt);
 175                 if (send_tok.length != 0) {
 176                     if (!compat20)
 177                         packet_start(SSH_MSG_AUTH_GSSAPI_TOKEN);
 178                     else
 179                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
 180                         packet_put_string(send_tok.value,send_tok.length);
 181                         packet_send();
 182                         packet_write_wait();
 183                 }
 184                 authctxt->postponed = 0;
 185                 dispatch_set(SSH_MSG_AUTH_GSSAPI_TOKEN, NULL);
 186                 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 187                 userauth_finish(authctxt, 0, "gssapi");
 188         } else {
 189                 if (send_tok.length != 0) {
 190                     if (!compat20)
 191                         packet_start(SSH_MSG_AUTH_GSSAPI_TOKEN);
 192                     else
 193                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
 194                         packet_put_string(send_tok.value,send_tok.length);
 195                         packet_send();
 196                         packet_write_wait();
 197                 }
 198                 if (maj_status == GSS_S_COMPLETE) {
 199                         dispatch_set(SSH_MSG_AUTH_GSSAPI_TOKEN, NULL);
 200                         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN,NULL);
 201                         if (!compat20)
 202                         input_gssapi_exchange_complete(0, 0, ctxt);
 203                         else
 204                         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
 205                                      &input_gssapi_exchange_complete);
 206                 }
 207         }
 208
 209         gss_release_buffer(&min_status, &send_tok);
 210 }
 211
 212 static void
 213 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
 214 {
 215         Authctxt *authctxt = ctxt;
 216         Gssctxt *gssctxt;
 217         gss_buffer_desc send_tok,recv_tok;
 218         OM_uint32 maj_status;
 219
 220         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 221                 fatal("No authentication or GSSAPI context");
 222
 223         gssctxt=authctxt->methoddata;
 224         recv_tok.value=packet_get_string(&recv_tok.length);
 225
 226         /* Push the error token into GSSAPI to see what it says */
 227         maj_status=PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 228                                                  &send_tok, NULL));
 229         packet_check_eom();
 230
 231         /* We can't return anything to the client, even if we wanted to */
 232         dispatch_set(SSH_MSG_AUTH_GSSAPI_TOKEN, NULL);
 233         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 234         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK,NULL);
 235
 236         /* The client will have already moved on to the next auth */
 237
 238 }
 239
 240 /* This is called when the client thinks we've completed authentication.
 241  * It should only be enabled in the dispatch handler by the function above,
 242  * which only enables it once the GSSAPI exchange is complete.
 243  */
 244
 245 static void
 246 input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt)
 247 {
 248         Authctxt *authctxt = ctxt;
 249         Gssctxt *gssctxt;
 250         int authenticated;
 251
 252         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 253                 fatal("No authentication or GSSAPI context");
 254
 255         if ((strcmp(authctxt->user, "") == 0) && (authctxt->pw == NULL)) {
 256             char *lname = NULL;
 257             PRIVSEP(ssh_gssapi_localname(&lname));
 258             if (lname && lname[0] != '\0') {
 259                 xfree(authctxt->user);
 260                 authctxt->user = lname;
 261                 debug("set username to %s from gssapi context", lname);
 262                 authctxt->pw = PRIVSEP(getpwnamallow(authctxt->user));
 263             } else {
 264                 debug("failed to set username from gssapi context");
 265             }
 266         }
 267         if (authctxt->pw) {
 268 #ifdef USE_PAM
 269             PRIVSEP(start_pam(authctxt->pw->pw_name));
 270 #endif
 271         } else {
 272             authctxt->valid = 0;
 273             authenticated = 0;
 274             goto finish;
 275         }
 276
 277         gssctxt=authctxt->methoddata;
 278
 279         /* ssh1 needs to exchange the hash of the keys */
 280         if (!compat20) {
 281
 282                 OM_uint32 min_status;
 283                 gss_buffer_desc dummy, msg_tok;
 284
 285                 /* ssh1 wraps the keys, in the monitor */
 286
 287                 dummy.value=malloc(sizeof(ssh1_key_digest));
 288                 memcpy(dummy.value,ssh1_key_digest,sizeof(ssh1_key_digest));
 289                 dummy.length=sizeof(ssh1_key_digest);
 290                 if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(gssctxt,&dummy,&msg_tok))))
 291                     fatal("Couldn't wrap keys");
 292
 293                 packet_start(SSH_SMSG_AUTH_GSSAPI_HASH);
 294                 packet_put_string((char *)msg_tok.value,msg_tok.length);
 295                 packet_send();
 296                 packet_write_wait();
 297                 gss_release_buffer(&min_status,&msg_tok);
 298         }
 299
 300
 301         /* We don't need to check the status, because the stored credentials
 302          * which userok uses are only populated once the context init step
 303          * has returned complete.
 304          */
 305
 306         authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 307
 308 finish:
 309         authctxt->postponed = 0;
 310         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 311         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 312         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 313         userauth_finish(authctxt, authenticated, "gssapi");
 314 }
 315
 316 static void ssh_gssapi_userauth_error(Gssctxt *ctxt) {
 317         char *errstr;
 318         OM_uint32 maj,min;
 319
 320         errstr=PRIVSEP(ssh_gssapi_last_error(ctxt,&maj,&min));
 321         if (errstr) {
 322             if (!compat20) {
 323                 packet_send_debug(errstr);
 324             } else {
 325                 packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERROR);
 326                 packet_put_int(maj);
 327                 packet_put_int(min);
 328                 packet_put_cstring(errstr);
 329                 packet_put_cstring("");
 330                 packet_send();
 331                 packet_write_wait();
 332                 xfree(errstr);
 333             }
 334         }
 335 }
 336
 337 Authmethod method_external = {
 338         "external-keyx",
 339         userauth_external,
 340         &options.gss_authentication
 341 };
 342
 343 Authmethod method_gssapi = {
 344         "gssapi",
 345         userauth_gssapi,
 346         &options.gss_authentication
 347 };
 348
 349 #endif /* GSSAPI */