openssh/auth1.c

   1 /*
   2  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   3  *                    All rights reserved
   4  *
   5  * As far as I am concerned, the code I have written for this software
   6  * can be used freely for any purpose.  Any derived versions of this
   7  * software must be clearly marked as such, and if the derived work is
   8  * incompatible with the protocol description in the RFC file, it must be
   9  * called by a name other than "ssh" or "Secure Shell".
  10  */
  11
  12 #include "includes.h"
  13 RCSID("$OpenBSD: auth1.c,v 1.44 2002/09/26 11:38:43 markus Exp $");
  14
  15 #include "xmalloc.h"
  16 #include "rsa.h"
  17 #include "ssh1.h"
  18 #include "dispatch.h"
  19 #include "packet.h"
  20 #include "buffer.h"
  21 #include "mpaux.h"
  22 #include "log.h"
  23 #include "servconf.h"
  24 #include "compat.h"
  25 #include "auth.h"
  26 #include "channels.h"
  27 #include "session.h"
  28 #include "uidswap.h"
  29 #include "monitor_wrap.h"
  30
  31 /* import */
  32 extern ServerOptions options;
  33 extern Authmethod method_gssapi;
  34
  35
  36
  37 #ifdef GSSAPI
  38 #ifdef GSI
  39 #include "globus_gss_assist.h"
  40 #endif
  41
  42 int     userauth_gssapi(Authctxt *authctxt);
  43
  44 void
  45 auth1_gss_protocol_error(int type, u_int32_t plen, void *ctxt)
  46 {
  47   Authctxt *authctxt = ctxt;
  48   /* Other side told us to abort, dont need to tell him */
  49   /* maybe we can us some other method. */
  50   if (type == SSH_MSG_AUTH_GSSAPI_ABORT) {
  51       log("auth1: GSSAPI aborting");
  52       dispatch_set(SSH_MSG_AUTH_GSSAPI_TOKEN, NULL);
  53       authctxt->success = 1; /* get out of loop*/
  54       return;
  55   }
  56
  57   log("auth1: protocol error: type %d plen %d", type, plen);
  58   packet_disconnect("Protocol error during GSSAPI authentication: "
  59           "Unknown packet type %d", type);
  60 }
  61
  62 #ifdef GSI
  63 int
  64 gsi_gridmap(char *subject_name, char **mapped_name)
  65 {
  66     return(globus_gss_assist_gridmap(subject_name, mapped_name) == 0);
  67 }
  68 #endif
  69
  70 /*
  71  * SSH1 GSSAPI clients may send us a user name of the form:
  72  *
  73  *   (1) username:x:SSL Subject Name
  74  *     or
  75  *   (2) username:i:SSL Subject Name
  76  *     or
  77  *   (3) username
  78  *
  79  *  if case 1, then uname is an explicit name (ssh -l uname). Keep this
  80  *  name always, rewrite the user parameter to be just uname. We'll pull
  81  *  the GSSAPI idenity out and deal with (or skip it) later.
  82  *
  83  *  if case 2, then uname is implicit (user didn't use the -l option), so
  84  *  use the default gridmap mapping and replace uname with whatever
  85  *  the gridmap maps to. If the gridmap mapping fails, drop down
  86  *  to just uname
  87  *
  88  *  if case 3, then leave it be.
  89  *
  90  *  This function may return the original pointer to the orginal string,
  91  *  the original pointer to a modified string, or a completely new pointer.
  92  */
  93 static char *
  94 ssh1_gssapi_parse_userstring(char *userstring)
  95 {
  96   char name_type = '\0';        /* explicit 'x' or implicit 'i' */
  97   char *ssl_subject_name = NULL;
  98   char *delim = NULL;
  99
 100   debug("Looking at username '%s' for gssapi-ssleay type name", userstring);
 101   if((delim = strchr(userstring, ':')) != NULL) {
 102       /* Parse and split into components */
 103       ssl_subject_name = strchr(delim + 1, ':');
 104
 105       if (ssl_subject_name) {
 106         /* Successful parse, split into components */
 107         *delim = '\0';
 108         name_type = *(delim + 1);
 109         *ssl_subject_name = '\0';
 110         ssl_subject_name++;
 111
 112         debug("Name parsed. type = '%c'. ssl subject name is \"%s\"",
 113               name_type, ssl_subject_name);
 114
 115       } else {
 116
 117         debug("Don't understand name format. Letting it pass.");
 118       }
 119   }
 120
 121 #ifdef GSI
 122   if(ssl_subject_name) {
 123     char *gridmapped_name = NULL;
 124     switch (name_type) {
 125     case 'x':
 126       debug("explicit name given, using %s as username", userstring);
 127       break;
 128
 129     case 'i':
 130       /* gridmap check */
 131       debug("implicit name given. gridmapping '%s'", ssl_subject_name);
 132
 133       PRIVSEP(gsi_gridmap(ssl_subject_name, &gridmapped_name));
 134       if (gridmapped_name && gridmapped_name[0] != '\0') {
 135         userstring = gridmapped_name;
 136         debug("I gridmapped and got %s", userstring);
 137
 138       } else {
 139         debug("I gridmapped and got null, reverting to %s", userstring);
 140       }
 141       break;
 142
 143     default:
 144       debug("Unknown name type '%c'. Ignoring.", name_type);
 145       break;
 146     }
 147   } else {
 148     debug("didn't find any :'s so I assume it's just a user name");
 149   }
 150 #endif /* GSI */
 151
 152   return userstring;
 153 }
 154 #endif
 155
 156 /*
 157  * convert ssh auth msg type into description
 158  */
 159 static char *
 160 get_authname(int type)
 161 {
 162         static char buf[1024];
 163         switch (type) {
 164         case SSH_CMSG_AUTH_PASSWORD:
 165                 return "password";
 166         case SSH_CMSG_AUTH_RSA:
 167                 return "rsa";
 168         case SSH_CMSG_AUTH_RHOSTS_RSA:
 169                 return "rhosts-rsa";
 170         case SSH_CMSG_AUTH_RHOSTS:
 171                 return "rhosts";
 172         case SSH_CMSG_AUTH_TIS:
 173         case SSH_CMSG_AUTH_TIS_RESPONSE:
 174                 return "challenge-response";
 175 #if defined(KRB4) || defined(KRB5)
 176         case SSH_CMSG_AUTH_KERBEROS:
 177                 return "kerberos";
 178 #endif
 179 #if defined(GSSAPI)
 180         case SSH_CMSG_AUTH_GSSAPI:
 181                 return "gssapi";
 182 #endif
 183         }
 184         snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
 185         return buf;
 186 }
 187
 188 /*
 189  * read packets, try to authenticate the user and
 190  * return only if authentication is successful
 191  */
 192 static void
 193 do_authloop(Authctxt *authctxt)
 194 {
 195         int authenticated = 0;
 196         u_int bits;
 197         Key *client_host_key;
 198         BIGNUM *n;
 199         char *client_user, *password;
 200         char info[1024];
 201         u_int dlen;
 202         u_int ulen;
 203         int type = 0;
 204         struct passwd *pw = authctxt->pw;
 205
 206         debug("Attempting authentication for %s%.100s.",
 207             authctxt->valid ? "" : "illegal user ", authctxt->user);
 208
 209         /* If the user has no password, accept authentication immediately. */
 210         if (options.password_authentication &&
 211 #if defined(KRB4) || defined(KRB5)
 212             (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
 213 #endif
 214             PRIVSEP(auth_password(authctxt, ""))) {
 215                 auth_log(authctxt, 1, "without authentication", "");
 216                 return;
 217         }
 218
 219         /* Indicate that authentication is needed. */
 220         packet_start(SSH_SMSG_FAILURE);
 221         packet_send();
 222         packet_write_wait();
 223
 224         client_user = NULL;
 225
 226         for (;;) {
 227                 /* default to fail */
 228                 authenticated = 0;
 229
 230                 info[0] = '\0';
 231
 232                 /* Get a packet from the client. */
 233                 type = packet_read();
 234
 235                 /* Process the packet. */
 236                 switch (type) {
 237
 238 #if defined(KRB4) || defined(KRB5)
 239                 case SSH_CMSG_AUTH_KERBEROS:
 240                         if (!options.kerberos_authentication) {
 241                                 verbose("Kerberos authentication disabled.");
 242                         } else {
 243                                 char *kdata = packet_get_string(&dlen);
 244                                 packet_check_eom();
 245
 246                                 if (kdata[0] == 4) { /* KRB_PROT_VERSION */
 247 #ifdef KRB4
 248                                         KTEXT_ST tkt, reply;
 249                                         tkt.length = dlen;
 250                                         if (tkt.length < MAX_KTXT_LEN)
 251                                                 memcpy(tkt.dat, kdata, tkt.length);
 252
 253                                         if (PRIVSEP(auth_krb4(authctxt, &tkt,
 254                                             &client_user, &reply))) {
 255                                                 authenticated = 1;
 256                                                 snprintf(info, sizeof(info),
 257                                                     " tktuser %.100s",
 258                                                     client_user);
 259
 260                                                 packet_start(
 261                                                     SSH_SMSG_AUTH_KERBEROS_RESPONSE);
 262                                                 packet_put_string((char *)
 263                                                     reply.dat, reply.length);
 264                                                 packet_send();
 265                                                 packet_write_wait();
 266                                         }
 267 #endif /* KRB4 */
 268                                 } else {
 269 #ifdef KRB5
 270                                         krb5_data tkt, reply;
 271                                         tkt.length = dlen;
 272                                         tkt.data = kdata;
 273
 274                                         if (PRIVSEP(auth_krb5(authctxt, &tkt,
 275                                             &client_user, &reply))) {
 276                                                 authenticated = 1;
 277                                                 snprintf(info, sizeof(info),
 278                                                     " tktuser %.100s",
 279                                                     client_user);
 280
 281                                                 /* Send response to client */
 282                                                 packet_start(
 283                                                     SSH_SMSG_AUTH_KERBEROS_RESPONSE);
 284                                                 packet_put_string((char *)
 285                                                     reply.data, reply.length);
 286                                                 packet_send();
 287                                                 packet_write_wait();
 288
 289                                                 if (reply.length)
 290                                                         xfree(reply.data);
 291                                         }
 292 #endif /* KRB5 */
 293                                 }
 294                                 xfree(kdata);
 295                         }
 296                         break;
 297 #endif /* KRB4 || KRB5 */
 298
 299 #ifdef GSSAPI
 300                 case SSH_CMSG_AUTH_GSSAPI:
 301                         if (!options.gss_authentication) {
 302                                 verbose("GSSAPI authentication disabled.");
 303                                 break;
 304                         }
 305                         /*
 306                         * GSSAPI was first added to ssh1 in ssh-1.2.27, and
 307                         * was added to the SecurtCRT product. In order
 308                         * to continue operating with these, we will add
 309                         * the equivelent GSSAPI support to SSH1.
 310                         * Will use the gssapi routines from the ssh2 as
 311                         * they are almost identical. But they use dispatch
 312                         * so we need to setup the dispatch tables here
 313                         * auth1.c for use only by the gssapi code.
 314                         * Since we already have the packet, we will call
 315                         * userauth_gssapi then start the dispatch loop.
 316                         */
 317                         if (!authctxt->valid) {
 318                         packet_disconnect("Authentication rejected for invalid user");
 319                         }
 320                         dispatch_init(&auth1_gss_protocol_error);
 321                         method_gssapi.userauth(authctxt);
 322                         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
 323                         if (authctxt->postponed) { /* failed, try other methods */
 324                                 authctxt->success = 0;
 325                                 authctxt->postponed = 0;
 326                                 break;
 327                         }
 328                         authenticated = 1;
 329                         break;
 330 #endif /* GSSAPI */
 331
 332 #if defined(AFS) || defined(KRB5)
 333                         /* XXX - punt on backward compatibility here. */
 334                 case SSH_CMSG_HAVE_KERBEROS_TGT:
 335                         packet_send_debug("Kerberos TGT passing disabled before authentication.");
 336                         break;
 337 #ifdef AFS
 338                 case SSH_CMSG_HAVE_AFS_TOKEN:
 339                         packet_send_debug("AFS token passing disabled before authentication.");
 340                         break;
 341 #endif /* AFS */
 342 #endif /* AFS || KRB5 */
 343
 344                 case SSH_CMSG_AUTH_RHOSTS:
 345                         if (!options.rhosts_authentication) {
 346                                 verbose("Rhosts authentication disabled.");
 347                                 break;
 348                         }
 349                         /*
 350                          * Get client user name.  Note that we just have to
 351                          * trust the client; this is one reason why rhosts
 352                          * authentication is insecure. (Another is
 353                          * IP-spoofing on a local network.)
 354                          */
 355                         client_user = packet_get_string(&ulen);
 356                         packet_check_eom();
 357
 358                         /* Try to authenticate using /etc/hosts.equiv and .rhosts. */
 359                         authenticated = auth_rhosts(pw, client_user);
 360
 361                         snprintf(info, sizeof info, " ruser %.100s", client_user);
 362                         break;
 363
 364                 case SSH_CMSG_AUTH_RHOSTS_RSA:
 365                         if (!options.rhosts_rsa_authentication) {
 366                                 verbose("Rhosts with RSA authentication disabled.");
 367                                 break;
 368                         }
 369                         /*
 370                          * Get client user name.  Note that we just have to
 371                          * trust the client; root on the client machine can
 372                          * claim to be any user.
 373                          */
 374                         client_user = packet_get_string(&ulen);
 375
 376                         /* Get the client host key. */
 377                         client_host_key = key_new(KEY_RSA1);
 378                         bits = packet_get_int();
 379                         packet_get_bignum(client_host_key->rsa->e);
 380                         packet_get_bignum(client_host_key->rsa->n);
 381
 382                         if (bits != BN_num_bits(client_host_key->rsa->n))
 383                                 verbose("Warning: keysize mismatch for client_host_key: "
 384                                     "actual %d, announced %d",
 385                                     BN_num_bits(client_host_key->rsa->n), bits);
 386                         packet_check_eom();
 387
 388                         authenticated = auth_rhosts_rsa(pw, client_user,
 389                             client_host_key);
 390                         key_free(client_host_key);
 391
 392                         snprintf(info, sizeof info, " ruser %.100s", client_user);
 393                         break;
 394
 395                 case SSH_CMSG_AUTH_RSA:
 396                         if (!options.rsa_authentication) {
 397                                 verbose("RSA authentication disabled.");
 398                                 break;
 399                         }
 400                         /* RSA authentication requested. */
 401                         if ((n = BN_new()) == NULL)
 402                                 fatal("do_authloop: BN_new failed");
 403                         packet_get_bignum(n);
 404                         packet_check_eom();
 405                         authenticated = auth_rsa(pw, n);
 406                         BN_clear_free(n);
 407                         break;
 408
 409                 case SSH_CMSG_AUTH_PASSWORD:
 410                         if (!options.password_authentication) {
 411                                 verbose("Password authentication disabled.");
 412                                 break;
 413                         }
 414                         /*
 415                          * Read user password.  It is in plain text, but was
 416                          * transmitted over the encrypted channel so it is
 417                          * not visible to an outside observer.
 418                          */
 419                         password = packet_get_string(&dlen);
 420                         packet_check_eom();
 421
 422                         /* Try authentication with the password. */
 423                         authenticated = PRIVSEP(auth_password(authctxt, password));
 424
 425                         memset(password, 0, strlen(password));
 426                         xfree(password);
 427                         break;
 428
 429                 case SSH_CMSG_AUTH_TIS:
 430                         debug("rcvd SSH_CMSG_AUTH_TIS");
 431                         if (options.challenge_response_authentication == 1) {
 432                                 char *challenge = get_challenge(authctxt);
 433                                 if (challenge != NULL) {
 434                                         debug("sending challenge '%s'", challenge);
 435                                         packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
 436                                         packet_put_cstring(challenge);
 437                                         xfree(challenge);
 438                                         packet_send();
 439                                         packet_write_wait();
 440                                         continue;
 441                                 }
 442                         }
 443                         break;
 444                 case SSH_CMSG_AUTH_TIS_RESPONSE:
 445                         debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
 446                         if (options.challenge_response_authentication == 1) {
 447                                 char *response = packet_get_string(&dlen);
 448                                 debug("got response '%s'", response);
 449                                 packet_check_eom();
 450                                 authenticated = verify_response(authctxt, response);
 451                                 memset(response, 'r', dlen);
 452                                 xfree(response);
 453                         }
 454                         break;
 455
 456                 default:
 457                         /*
 458                          * Any unknown messages will be ignored (and failure
 459                          * returned) during authentication.
 460                          */
 461                         log("Unknown message during authentication: type %d", type);
 462                         break;
 463                 }
 464 #ifdef BSD_AUTH
 465                 if (authctxt->as) {
 466                         auth_close(authctxt->as);
 467                         authctxt->as = NULL;
 468                 }
 469 #endif
 470                 if (!authctxt->valid && authenticated)
 471                         fatal("INTERNAL ERROR: authenticated invalid user %s",
 472                             authctxt->user);
 473
 474 #ifdef _UNICOS
 475                 if (type == SSH_CMSG_AUTH_PASSWORD && !authenticated)
 476                         cray_login_failure(authctxt->user, IA_UDBERR);
 477                 if (authenticated && cray_access_denied(authctxt->user)) {
 478                         authenticated = 0;
 479                         fatal("Access denied for user %s.",authctxt->user);
 480                 }
 481 #endif /* _UNICOS */
 482
 483 #ifdef HAVE_CYGWIN
 484                 if (authenticated &&
 485                     !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) {
 486                         packet_disconnect("Authentication rejected for uid %d.",
 487                         pw == NULL ? -1 : pw->pw_uid);
 488                         authenticated = 0;
 489                 }
 490 #else
 491                 /* Special handling for root */
 492                 if (!use_privsep &&
 493                     authenticated && authctxt->pw->pw_uid == 0 &&
 494                     !auth_root_allowed(get_authname(type)))
 495                         authenticated = 0;
 496 #endif
 497 #ifdef USE_PAM
 498                 if (!use_privsep && authenticated &&
 499                     !do_pam_account(pw->pw_name, client_user))
 500                         authenticated = 0;
 501 #endif
 502
 503                 /* Log before sending the reply */
 504                 auth_log(authctxt, authenticated, get_authname(type), info);
 505
 506                 if (client_user != NULL) {
 507                         xfree(client_user);
 508                         client_user = NULL;
 509                 }
 510
 511                 if (authenticated)
 512                         return;
 513
 514                 if (authctxt->failures++ > AUTH_FAIL_MAX) {
 515                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 516                 }
 517
 518                 packet_start(SSH_SMSG_FAILURE);
 519                 packet_send();
 520                 packet_write_wait();
 521         }
 522 }
 523
 524 /*
 525  * Performs authentication of an incoming connection.  Session key has already
 526  * been exchanged and encryption is enabled.
 527  */
 528 Authctxt *
 529 do_authentication(void)
 530 {
 531         Authctxt *authctxt;
 532         u_int ulen;
 533         char *user, *style = NULL;
 534
 535         /* Get the name of the user that we wish to log in as. */
 536         packet_read_expect(SSH_CMSG_USER);
 537
 538         /* Get the user name. */
 539         user = packet_get_string(&ulen);
 540         packet_check_eom();
 541
 542 #ifdef GSSAPI
 543         /* Parse GSSAPI identity from userstring */
 544         user = ssh1_gssapi_parse_userstring(user);
 545 #endif /* GSSAPI */
 546
 547         if ((style = strchr(user, ':')) != NULL)
 548                 *style++ = '\0';
 549
 550 #ifdef KRB5
 551         /* XXX - SSH.com Kerberos v5 braindeath. */
 552         if ((datafellows & SSH_BUG_K5USER) &&
 553             options.kerberos_authentication) {
 554                 char *p;
 555                 if ((p = strchr(user, '@')) != NULL)
 556                         *p = '\0';
 557         }
 558 #endif
 559
 560         authctxt = authctxt_new();
 561         authctxt->user = user;
 562         authctxt->style = style;
 563
 564         /* Verify that the user is a valid user. */
 565         if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
 566                 authctxt->valid = 1;
 567         else
 568                 debug("do_authentication: illegal user %s", user);
 569
 570         setproctitle("%s%s", authctxt->pw ? user : "unknown",
 571             use_privsep ? " [net]" : "");
 572
 573 #ifdef USE_PAM
 574         PRIVSEP(start_pam(authctxt->pw == NULL ? "NOUSER" : user));
 575 #endif
 576
 577         /*
 578          * If we are not running as root, the user must have the same uid as
 579          * the server. (Unless you are running Windows)
 580          */
 581 #ifndef HAVE_CYGWIN
 582         if (!use_privsep && getuid() != 0 && authctxt->pw &&
 583             authctxt->pw->pw_uid != getuid())
 584                 packet_disconnect("Cannot change user when server not running as root.");
 585 #endif
 586
 587         /*
 588          * Loop until the user has been authenticated or the connection is
 589          * closed, do_authloop() returns only if authentication is successful
 590          */
 591         do_authloop(authctxt);
 592
 593         /* The user has been authenticated and accepted. */
 594         packet_start(SSH_SMSG_SUCCESS);
 595         packet_send();
 596         packet_write_wait();
 597
 598         return (authctxt);
 599 }