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 1.47 2003/02/06 21:22:42 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
  34 #ifdef GSSAPI
  35 #ifdef GSI
  36 #include "globus_gss_assist.h"
  37 #endif
  38
  39 extern Authmethod method_gssapi;
  40
  41 int     userauth_gssapi(Authctxt *authctxt);
  42
  43 void
  44 auth1_gss_protocol_error(int type, u_int32_t plen, void *ctxt)
  45 {
  46   Authctxt *authctxt = ctxt;
  47   /* Other side told us to abort, dont need to tell him */
  48   /* maybe we can use some other method. */
  49   if (type == SSH_MSG_AUTH_GSSAPI_ABORT) {
  50       log("auth1: GSSAPI aborting");
  51       dispatch_set(SSH_MSG_AUTH_GSSAPI_TOKEN, NULL);
  52       authctxt->success = 1; /* get out of loop*/
  53       return;
  54   }
  55
  56   log("auth1: protocol error: type %d plen %d", type, plen);
  57   packet_disconnect("Protocol error during GSSAPI authentication: "
  58           "Unknown packet type %d", type);
  59 }
  60
  61 #ifdef GSI
  62 int
  63 gsi_gridmap(char *subject_name, char **mapped_name)
  64 {
  65 #ifdef GLOBUS_GSI_GSS_ASSIST_MODULE
  66     if (globus_module_activate(GLOBUS_GSI_GSS_ASSIST_MODULE) != 0) {
  67         return 0;
  68     }
  69 #endif
  70     return(globus_gss_assist_gridmap(subject_name, mapped_name) == 0);
  71 }
  72 #endif
  73
  74 /*
  75  * SSH1 GSSAPI clients may send us a user name of the form:
  76  *
  77  *   (1) username:x:SSL Subject Name
  78  *     or
  79  *   (2) username:i:SSL Subject Name
  80  *     or
  81  *   (3) username
  82  *
  83  *  if case 1, then uname is an explicit name (ssh -l uname). Keep this
  84  *  name always, rewrite the user parameter to be just uname. We'll pull
  85  *  the GSSAPI idenity out and deal with (or skip it) later.
  86  *
  87  *  if case 2, then uname is implicit (user didn't use the -l option), so
  88  *  use the default gridmap mapping and replace uname with whatever
  89  *  the gridmap maps to. If the gridmap mapping fails, drop down
  90  *  to just uname
  91  *
  92  *  if case 3, then leave it be.
  93  *
  94  *  This function may return the original pointer to the orginal string,
  95  *  the original pointer to a modified string, or a completely new pointer.
  96  */
  97 static char *
  98 ssh1_gssapi_parse_userstring(char *userstring)
  99 {
 100   char name_type = '\0';        /* explicit 'x' or implicit 'i' */
 101   char *ssl_subject_name = NULL;
 102   char *delim = NULL;
 103
 104   debug("Looking at username '%s' for gssapi-ssleay type name", userstring);
 105   if((delim = strchr(userstring, ':')) != NULL) {
 106       /* Parse and split into components */
 107       ssl_subject_name = strchr(delim + 1, ':');
 108
 109       if (ssl_subject_name) {
 110         /* Successful parse, split into components */
 111         *delim = '\0';
 112         name_type = *(delim + 1);
 113         *ssl_subject_name = '\0';
 114         ssl_subject_name++;
 115
 116         debug("Name parsed. type = '%c'. ssl subject name is \"%s\"",
 117               name_type, ssl_subject_name);
 118
 119       } else {
 120
 121         debug("Don't understand name format. Letting it pass.");
 122       }
 123   }
 124
 125 #ifdef GSI
 126   if(ssl_subject_name) {
 127     char *gridmapped_name = NULL;
 128     switch (name_type) {
 129     case 'x':
 130       debug("explicit name given, using %s as username", userstring);
 131       break;
 132
 133     case 'i':
 134       /* gridmap check */
 135       debug("implicit name given. gridmapping '%s'", ssl_subject_name);
 136
 137       PRIVSEP(gsi_gridmap(ssl_subject_name, &gridmapped_name));
 138       if (gridmapped_name && gridmapped_name[0] != '\0') {
 139         userstring = gridmapped_name;
 140         debug("I gridmapped and got %s", userstring);
 141
 142       } else {
 143         debug("I gridmapped and got null, reverting to %s", userstring);
 144       }
 145       break;
 146
 147     default:
 148       debug("Unknown name type '%c'. Ignoring.", name_type);
 149       break;
 150     }
 151   } else {
 152     debug("didn't find any :'s so I assume it's just a user name");
 153   }
 154 #endif /* GSI */
 155
 156   return userstring;
 157 }
 158 #endif
 159
 160 /*
 161  * convert ssh auth msg type into description
 162  */
 163 static char *
 164 get_authname(int type)
 165 {
 166         static char buf[1024];
 167         switch (type) {
 168         case SSH_CMSG_AUTH_PASSWORD:
 169                 return "password";
 170         case SSH_CMSG_AUTH_RSA:
 171                 return "rsa";
 172         case SSH_CMSG_AUTH_RHOSTS_RSA:
 173                 return "rhosts-rsa";
 174         case SSH_CMSG_AUTH_RHOSTS:
 175                 return "rhosts";
 176         case SSH_CMSG_AUTH_TIS:
 177         case SSH_CMSG_AUTH_TIS_RESPONSE:
 178                 return "challenge-response";
 179 #if defined(KRB4) || defined(KRB5)
 180         case SSH_CMSG_AUTH_KERBEROS:
 181                 return "kerberos";
 182 #endif
 183 #if defined(GSSAPI)
 184         case SSH_CMSG_AUTH_GSSAPI:
 185                 return "gssapi";
 186 #endif
 187         }
 188         snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
 189         return buf;
 190 }
 191
 192 /*
 193  * read packets, try to authenticate the user and
 194  * return only if authentication is successful
 195  */
 196 static void
 197 do_authloop(Authctxt *authctxt)
 198 {
 199         int authenticated = 0;
 200         u_int bits;
 201         Key *client_host_key;
 202         BIGNUM *n;
 203         char *client_user, *password;
 204         char info[1024];
 205         u_int dlen;
 206         u_int ulen;
 207         int type = 0;
 208         struct passwd *pw = authctxt->pw;
 209
 210         debug("Attempting authentication for %s%.100s.",
 211             authctxt->valid ? "" : "illegal user ", authctxt->user);
 212
 213         /* If the user has no password, accept authentication immediately. */
 214         if (options.password_authentication &&
 215 #if defined(KRB4) || defined(KRB5)
 216             (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
 217 #endif
 218             PRIVSEP(auth_password(authctxt, ""))) {
 219                 auth_log(authctxt, 1, "without authentication", "");
 220                 return;
 221         }
 222
 223         /* Indicate that authentication is needed. */
 224         packet_start(SSH_SMSG_FAILURE);
 225         packet_send();
 226         packet_write_wait();
 227
 228         client_user = NULL;
 229
 230         for (;;) {
 231                 /* default to fail */
 232                 authenticated = 0;
 233
 234                 info[0] = '\0';
 235
 236                 /* Get a packet from the client. */
 237                 type = packet_read();
 238
 239                 /* Process the packet. */
 240                 switch (type) {
 241
 242 #if defined(KRB4) || defined(KRB5)
 243                 case SSH_CMSG_AUTH_KERBEROS:
 244                         if (!options.kerberos_authentication) {
 245                                 verbose("Kerberos authentication disabled.");
 246                         } else {
 247                                 char *kdata = packet_get_string(&dlen);
 248                                 packet_check_eom();
 249
 250                                 if (kdata[0] == 4) { /* KRB_PROT_VERSION */
 251 #ifdef KRB4
 252                                         KTEXT_ST tkt, reply;
 253                                         tkt.length = dlen;
 254                                         if (tkt.length < MAX_KTXT_LEN)
 255                                                 memcpy(tkt.dat, kdata, tkt.length);
 256
 257                                         if (PRIVSEP(auth_krb4(authctxt, &tkt,
 258                                             &client_user, &reply))) {
 259                                                 authenticated = 1;
 260                                                 snprintf(info, sizeof(info),
 261                                                     " tktuser %.100s",
 262                                                     client_user);
 263
 264                                                 packet_start(
 265                                                     SSH_SMSG_AUTH_KERBEROS_RESPONSE);
 266                                                 packet_put_string((char *)
 267                                                     reply.dat, reply.length);
 268                                                 packet_send();
 269                                                 packet_write_wait();
 270                                         }
 271 #endif /* KRB4 */
 272                                 } else {
 273 #ifdef KRB5
 274                                         krb5_data tkt, reply;
 275                                         tkt.length = dlen;
 276                                         tkt.data = kdata;
 277
 278                                         if (PRIVSEP(auth_krb5(authctxt, &tkt,
 279                                             &client_user, &reply))) {
 280                                                 authenticated = 1;
 281                                                 snprintf(info, sizeof(info),
 282                                                     " tktuser %.100s",
 283                                                     client_user);
 284
 285                                                 /* Send response to client */
 286                                                 packet_start(
 287                                                     SSH_SMSG_AUTH_KERBEROS_RESPONSE);
 288                                                 packet_put_string((char *)
 289                                                     reply.data, reply.length);
 290                                                 packet_send();
 291                                                 packet_write_wait();
 292
 293                                                 if (reply.length)
 294                                                         xfree(reply.data);
 295                                         }
 296 #endif /* KRB5 */
 297                                 }
 298                                 xfree(kdata);
 299                         }
 300                         break;
 301 #endif /* KRB4 || KRB5 */
 302
 303 #ifdef GSSAPI
 304                 case SSH_CMSG_AUTH_GSSAPI:
 305                         if (!options.gss_authentication) {
 306                                 verbose("GSSAPI authentication disabled.");
 307                                 break;
 308                         }
 309                         /*
 310                         * GSSAPI was first added to ssh1 in ssh-1.2.27, and
 311                         * was added to the SecurtCRT product. In order
 312                         * to continue operating with these, we will add
 313                         * the equivelent GSSAPI support to SSH1.
 314                         * Will use the gssapi routines from the ssh2 as
 315                         * they are almost identical. But they use dispatch
 316                         * so we need to setup the dispatch tables here
 317                         * auth1.c for use only by the gssapi code.
 318                         * Since we already have the packet, we will call
 319                         * userauth_gssapi then start the dispatch loop.
 320                         */
 321                         if (!authctxt->valid) {
 322                         packet_disconnect("Authentication rejected for invalid user");
 323                         }
 324                         dispatch_init(&auth1_gss_protocol_error);
 325                         method_gssapi.userauth(authctxt);
 326                         if (!authctxt->postponed) { /* failed before starting dispatch */
 327                                 authctxt->success = 0;
 328                                 authctxt->postponed = 0;
 329                                 break;
 330                         }
 331                         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
 332                         if (authctxt->postponed) { /* failed, try other methods */
 333                                 authctxt->success = 0;
 334                                 authctxt->postponed = 0;
 335                                 break;
 336                         }
 337                         authenticated = 1;
 338                         break;
 339 #endif /* GSSAPI */
 340
 341 #if defined(AFS) || defined(KRB5)
 342                         /* XXX - punt on backward compatibility here. */
 343                 case SSH_CMSG_HAVE_KERBEROS_TGT:
 344                         packet_send_debug("Kerberos TGT passing disabled before authentication.");
 345                         break;
 346 #ifdef AFS
 347                 case SSH_CMSG_HAVE_AFS_TOKEN:
 348                         packet_send_debug("AFS token passing disabled before authentication.");
 349                         break;
 350 #endif /* AFS */
 351 #endif /* AFS || KRB5 */
 352
 353                 case SSH_CMSG_AUTH_RHOSTS:
 354                         if (!options.rhosts_authentication) {
 355                                 verbose("Rhosts authentication disabled.");
 356                                 break;
 357                         }
 358                         /*
 359                          * Get client user name.  Note that we just have to
 360                          * trust the client; this is one reason why rhosts
 361                          * authentication is insecure. (Another is
 362                          * IP-spoofing on a local network.)
 363                          */
 364                         client_user = packet_get_string(&ulen);
 365                         packet_check_eom();
 366
 367                         /* Try to authenticate using /etc/hosts.equiv and .rhosts. */
 368                         authenticated = auth_rhosts(pw, client_user);
 369
 370                         snprintf(info, sizeof info, " ruser %.100s", client_user);
 371                         break;
 372
 373                 case SSH_CMSG_AUTH_RHOSTS_RSA:
 374                         if (!options.rhosts_rsa_authentication) {
 375                                 verbose("Rhosts with RSA authentication disabled.");
 376                                 break;
 377                         }
 378                         /*
 379                          * Get client user name.  Note that we just have to
 380                          * trust the client; root on the client machine can
 381                          * claim to be any user.
 382                          */
 383                         client_user = packet_get_string(&ulen);
 384
 385                         /* Get the client host key. */
 386                         client_host_key = key_new(KEY_RSA1);
 387                         bits = packet_get_int();
 388                         packet_get_bignum(client_host_key->rsa->e);
 389                         packet_get_bignum(client_host_key->rsa->n);
 390
 391                         if (bits != BN_num_bits(client_host_key->rsa->n))
 392                                 verbose("Warning: keysize mismatch for client_host_key: "
 393                                     "actual %d, announced %d",
 394                                     BN_num_bits(client_host_key->rsa->n), bits);
 395                         packet_check_eom();
 396
 397                         authenticated = auth_rhosts_rsa(pw, client_user,
 398                             client_host_key);
 399                         key_free(client_host_key);
 400
 401                         snprintf(info, sizeof info, " ruser %.100s", client_user);
 402                         break;
 403
 404                 case SSH_CMSG_AUTH_RSA:
 405                         if (!options.rsa_authentication) {
 406                                 verbose("RSA authentication disabled.");
 407                                 break;
 408                         }
 409                         /* RSA authentication requested. */
 410                         if ((n = BN_new()) == NULL)
 411                                 fatal("do_authloop: BN_new failed");
 412                         packet_get_bignum(n);
 413                         packet_check_eom();
 414                         authenticated = auth_rsa(pw, n);
 415                         BN_clear_free(n);
 416                         break;
 417
 418                 case SSH_CMSG_AUTH_PASSWORD:
 419                         if (!options.password_authentication) {
 420                                 verbose("Password authentication disabled.");
 421                                 break;
 422                         }
 423                         /*
 424                          * Read user password.  It is in plain text, but was
 425                          * transmitted over the encrypted channel so it is
 426                          * not visible to an outside observer.
 427                          */
 428                         password = packet_get_string(&dlen);
 429                         packet_check_eom();
 430
 431                         /* Try authentication with the password. */
 432                         authenticated = PRIVSEP(auth_password(authctxt, password));
 433
 434                         memset(password, 0, strlen(password));
 435                         xfree(password);
 436                         break;
 437
 438                 case SSH_CMSG_AUTH_TIS:
 439                         debug("rcvd SSH_CMSG_AUTH_TIS");
 440                         if (options.challenge_response_authentication == 1) {
 441                                 char *challenge = get_challenge(authctxt);
 442                                 if (challenge != NULL) {
 443                                         debug("sending challenge '%s'", challenge);
 444                                         packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
 445                                         packet_put_cstring(challenge);
 446                                         xfree(challenge);
 447                                         packet_send();
 448                                         packet_write_wait();
 449                                         continue;
 450                                 }
 451                         }
 452                         break;
 453                 case SSH_CMSG_AUTH_TIS_RESPONSE:
 454                         debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
 455                         if (options.challenge_response_authentication == 1) {
 456                                 char *response = packet_get_string(&dlen);
 457                                 packet_check_eom();
 458                                 authenticated = verify_response(authctxt, response);
 459                                 memset(response, 'r', dlen);
 460                                 xfree(response);
 461                         }
 462                         break;
 463
 464                 default:
 465                         /*
 466                          * Any unknown messages will be ignored (and failure
 467                          * returned) during authentication.
 468                          */
 469                         log("Unknown message during authentication: type %d", type);
 470                         break;
 471                 }
 472 #ifdef BSD_AUTH
 473                 if (authctxt->as) {
 474                         auth_close(authctxt->as);
 475                         authctxt->as = NULL;
 476                 }
 477 #endif
 478                 if (!authctxt->valid && authenticated)
 479                         fatal("INTERNAL ERROR: authenticated invalid user %s",
 480                             authctxt->user);
 481
 482 #ifdef _UNICOS
 483                 if (type == SSH_CMSG_AUTH_PASSWORD && !authenticated)
 484                         cray_login_failure(authctxt->user, IA_UDBERR);
 485                 if (authenticated && cray_access_denied(authctxt->user)) {
 486                         authenticated = 0;
 487                         fatal("Access denied for user %s.",authctxt->user);
 488                 }
 489 #endif /* _UNICOS */
 490
 491 #ifdef HAVE_CYGWIN
 492                 if (authenticated &&
 493                     !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) {
 494                         packet_disconnect("Authentication rejected for uid %d.",
 495                         pw == NULL ? -1 : pw->pw_uid);
 496                         authenticated = 0;
 497                 }
 498 #else
 499                 /* Special handling for root */
 500                 if (authenticated && authctxt->pw->pw_uid == 0 &&
 501                     !auth_root_allowed(get_authname(type)))
 502                         authenticated = 0;
 503 #endif
 504 #ifdef USE_PAM
 505                 if (!use_privsep && authenticated &&
 506                     !do_pam_account(pw->pw_name, client_user))
 507                         authenticated = 0;
 508 #endif
 509
 510                 /* Log before sending the reply */
 511                 auth_log(authctxt, authenticated, get_authname(type), info);
 512
 513                 if (client_user != NULL) {
 514                         xfree(client_user);
 515                         client_user = NULL;
 516                 }
 517
 518                 if (authenticated)
 519                         return;
 520
 521                 if (authctxt->failures++ > AUTH_FAIL_MAX) {
 522                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 523                 }
 524
 525                 packet_start(SSH_SMSG_FAILURE);
 526                 packet_send();
 527                 packet_write_wait();
 528         }
 529 }
 530
 531 /*
 532  * Performs authentication of an incoming connection.  Session key has already
 533  * been exchanged and encryption is enabled.
 534  */
 535 Authctxt *
 536 do_authentication(void)
 537 {
 538         Authctxt *authctxt;
 539         u_int ulen;
 540         char *user, *style = NULL;
 541
 542         /* Get the name of the user that we wish to log in as. */
 543         packet_read_expect(SSH_CMSG_USER);
 544
 545         /* Get the user name. */
 546         user = packet_get_string(&ulen);
 547         packet_check_eom();
 548
 549 #ifdef GSSAPI
 550         /* Parse GSSAPI identity from userstring */
 551         user = ssh1_gssapi_parse_userstring(user);
 552 #endif /* GSSAPI */
 553
 554         if ((style = strchr(user, ':')) != NULL)
 555                 *style++ = '\0';
 556
 557 #ifdef KRB5
 558         /* XXX - SSH.com Kerberos v5 braindeath. */
 559         if ((datafellows & SSH_BUG_K5USER) &&
 560             options.kerberos_authentication) {
 561                 char *p;
 562                 if ((p = strchr(user, '@')) != NULL)
 563                         *p = '\0';
 564         }
 565 #endif
 566
 567         authctxt = authctxt_new();
 568         authctxt->user = user;
 569         authctxt->style = style;
 570
 571         /* Verify that the user is a valid user. */
 572         if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
 573                 authctxt->valid = 1;
 574         else
 575                 debug("do_authentication: illegal user %s", user);
 576
 577         setproctitle("%s%s", authctxt->pw ? user : "unknown",
 578             use_privsep ? " [net]" : "");
 579
 580 #ifdef USE_PAM
 581         PRIVSEP(start_pam(authctxt->pw == NULL ? "NOUSER" : user));
 582 #endif
 583
 584         /*
 585          * If we are not running as root, the user must have the same uid as
 586          * the server. (Unless you are running Windows)
 587          */
 588 #ifndef HAVE_CYGWIN
 589         if (!use_privsep && getuid() != 0 && authctxt->pw &&
 590             authctxt->pw->pw_uid != getuid())
 591                 packet_disconnect("Cannot change user when server not running as root.");
 592 #endif
 593
 594         /*
 595          * Loop until the user has been authenticated or the connection is
 596          * closed, do_authloop() returns only if authentication is successful
 597          */
 598         do_authloop(authctxt);
 599
 600         /* The user has been authenticated and accepted. */
 601         packet_start(SSH_SMSG_SUCCESS);
 602         packet_send();
 603         packet_write_wait();
 604
 605         return (authctxt);
 606 }