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 1.35 2002/02/03 17:53:25 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 "misc.h"
  29 #include "uidswap.h"
  30
  31 #ifdef GSSAPI
  32 int     userauth_gssapi(Authctxt *authctxt);
  33 char *  gssapi_parse_userstring(char *userstring);
  34 #endif
  35
  36 /* import */
  37 extern ServerOptions options;
  38
  39 #ifdef GSSAPI
  40 void
  41 auth1_gss_protocol_error(int type, u_int32_t plen, void *ctxt)
  42 {
  43   Authctxt *authctxt = ctxt;
  44   /* Other side told us to abort, dont need to tell him */
  45   /* maybe we can us some other method. */
  46   if (type == SSH_MSG_AUTH_GSSAPI_ABORT) {
  47       log("auth1: GSSAPI aborting");
  48       dispatch_set(SSH_MSG_AUTH_GSSAPI_TOKEN, NULL);
  49       authctxt->success = 1; /* get out of loop*/
  50       return;
  51   }
  52
  53   log("auth1: protocol error: type %d plen %d", type, plen);
  54   packet_disconnect("Protocol error during GSSAPI authentication: "
  55           "Unknown packet type %d", type);
  56 }
  57 #endif
  58
  59 /*
  60  * convert ssh auth msg type into description
  61  */
  62 static char *
  63 get_authname(int type)
  64 {
  65         static char buf[1024];
  66         switch (type) {
  67         case SSH_CMSG_AUTH_PASSWORD:
  68                 return "password";
  69         case SSH_CMSG_AUTH_RSA:
  70                 return "rsa";
  71         case SSH_CMSG_AUTH_RHOSTS_RSA:
  72                 return "rhosts-rsa";
  73         case SSH_CMSG_AUTH_RHOSTS:
  74                 return "rhosts";
  75         case SSH_CMSG_AUTH_TIS:
  76         case SSH_CMSG_AUTH_TIS_RESPONSE:
  77                 return "challenge-response";
  78 #if defined(KRB4) || defined(KRB5)
  79         case SSH_CMSG_AUTH_KERBEROS:
  80                 return "kerberos";
  81 #endif
  82 #if defined(GSSAPI)
  83         case SSH_CMSG_AUTH_GSSAPI:
  84                 return "gssapi";
  85 #endif
  86         }
  87         snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
  88         return buf;
  89 }
  90
  91 /*
  92  * read packets, try to authenticate the user and
  93  * return only if authentication is successful
  94  */
  95 static void
  96 do_authloop(Authctxt *authctxt)
  97 {
  98         int authenticated = 0;
  99         u_int bits;
 100         Key *client_host_key;
 101         BIGNUM *n;
 102         char *client_user, *password;
 103         char info[1024];
 104         u_int dlen;
 105         u_int ulen;
 106         int type = 0;
 107         struct passwd *pw = authctxt->pw;
 108
 109         debug("Attempting authentication for %s%.100s.",
 110             authctxt->valid ? "" : "illegal user ", authctxt->user);
 111
 112         /* If the user has no password, accept authentication immediately. */
 113         if (options.password_authentication &&
 114 #if defined(KRB4) || defined(KRB5)
 115             (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
 116 #endif
 117 #ifdef USE_PAM
 118             auth_pam_password(pw, "")) {
 119 #elif defined(HAVE_OSF_SIA)
 120             0) {
 121 #else
 122             auth_password(authctxt, "")) {
 123 #endif
 124                 auth_log(authctxt, 1, "without authentication", "");
 125                 return;
 126         }
 127
 128         /* Indicate that authentication is needed. */
 129         packet_start(SSH_SMSG_FAILURE);
 130         packet_send();
 131         packet_write_wait();
 132
 133         client_user = NULL;
 134
 135         for (;;) {
 136                 /* default to fail */
 137                 authenticated = 0;
 138
 139                 info[0] = '\0';
 140
 141                 /* Get a packet from the client. */
 142                 type = packet_read();
 143
 144                 /* Process the packet. */
 145                 switch (type) {
 146
 147 #if defined(KRB4) || defined(KRB5)
 148                 case SSH_CMSG_AUTH_KERBEROS:
 149                         if (!options.kerberos_authentication) {
 150                                 verbose("Kerberos authentication disabled.");
 151                         } else {
 152                                 char *kdata = packet_get_string(&dlen);
 153                                 packet_check_eom();
 154
 155                                 if (kdata[0] == 4) { /* KRB_PROT_VERSION */
 156 #ifdef KRB4
 157                                         KTEXT_ST tkt;
 158
 159                                         tkt.length = dlen;
 160                                         if (tkt.length < MAX_KTXT_LEN)
 161                                                 memcpy(tkt.dat, kdata, tkt.length);
 162
 163                                         if (auth_krb4(authctxt, &tkt, &client_user)) {
 164                                                 authenticated = 1;
 165                                                 snprintf(info, sizeof(info),
 166                                                     " tktuser %.100s",
 167                                                     client_user);
 168                                         }
 169 #endif /* KRB4 */
 170                                 } else {
 171 #ifdef KRB5
 172                                         krb5_data tkt;
 173                                         tkt.length = dlen;
 174                                         tkt.data = kdata;
 175
 176                                         if (auth_krb5(authctxt, &tkt, &client_user)) {
 177                                                 authenticated = 1;
 178                                                 snprintf(info, sizeof(info),
 179                                                     " tktuser %.100s",
 180                                                     client_user);
 181                                         }
 182 #endif /* KRB5 */
 183                                 }
 184                                 xfree(kdata);
 185                         }
 186                         break;
 187 #endif /* KRB4 || KRB5 */
 188
 189 #ifdef GSSAPI
 190                 case SSH_CMSG_AUTH_GSSAPI:
 191                         if (!options.gss_authentication) {
 192                                 verbose("GSSAPI authentication disabled.");
 193                                 break;
 194                         }
 195                         /*
 196                         * GSSAPI was first added to ssh1 in ssh-1.2.27, and
 197                         * was added to the SecurtCRT product. In order
 198                         * to continue operating with these, we will add
 199                         * the equivelent GSSAPI support to SSH1.
 200                         * Will use the gssapi routines from the ssh2 as
 201                         * they are almost identical. But they use dispatch
 202                         * so we need to setup the dispatch tables here
 203                         * auth1.c for use only by the gssapi code.
 204                         * Since we already have the packet, we will call
 205                         * userauth_gssapi then start the dispatch loop.
 206                         */
 207                         if (!authctxt->valid) {
 208                         packet_disconnect("Authentication rejected for invalid user");
 209                         }
 210                         dispatch_init(&auth1_gss_protocol_error);
 211                         userauth_gssapi(authctxt);
 212                         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
 213                         if (authctxt->postponed) { /* failed, try other methods */
 214                                 authctxt->success = 0;
 215                                 authctxt->postponed = 0;
 216                                 break;
 217                         }
 218                         do_authenticated(authctxt);
 219                         /* will only return if authenticated */
 220                         authenticated = 1;
 221                         break;
 222 #endif /* GSSAPI */
 223
 224 #if defined(AFS) || defined(KRB5)
 225                         /* XXX - punt on backward compatibility here. */
 226                 case SSH_CMSG_HAVE_KERBEROS_TGT:
 227                         packet_send_debug("Kerberos TGT passing disabled before authentication.");
 228                         break;
 229 #ifdef AFS
 230                 case SSH_CMSG_HAVE_AFS_TOKEN:
 231                         packet_send_debug("AFS token passing disabled before authentication.");
 232                         break;
 233 #endif /* AFS */
 234 #endif /* AFS || KRB5 */
 235
 236                 case SSH_CMSG_AUTH_RHOSTS:
 237                         if (!options.rhosts_authentication) {
 238                                 verbose("Rhosts authentication disabled.");
 239                                 break;
 240                         }
 241                         /*
 242                          * Get client user name.  Note that we just have to
 243                          * trust the client; this is one reason why rhosts
 244                          * authentication is insecure. (Another is
 245                          * IP-spoofing on a local network.)
 246                          */
 247                         client_user = packet_get_string(&ulen);
 248                         packet_check_eom();
 249
 250                         /* Try to authenticate using /etc/hosts.equiv and .rhosts. */
 251                         authenticated = auth_rhosts(pw, client_user);
 252
 253                         snprintf(info, sizeof info, " ruser %.100s", client_user);
 254                         break;
 255
 256                 case SSH_CMSG_AUTH_RHOSTS_RSA:
 257                         if (!options.rhosts_rsa_authentication) {
 258                                 verbose("Rhosts with RSA authentication disabled.");
 259                                 break;
 260                         }
 261                         /*
 262                          * Get client user name.  Note that we just have to
 263                          * trust the client; root on the client machine can
 264                          * claim to be any user.
 265                          */
 266                         client_user = packet_get_string(&ulen);
 267
 268                         /* Get the client host key. */
 269                         client_host_key = key_new(KEY_RSA1);
 270                         bits = packet_get_int();
 271                         packet_get_bignum(client_host_key->rsa->e);
 272                         packet_get_bignum(client_host_key->rsa->n);
 273
 274                         if (bits != BN_num_bits(client_host_key->rsa->n))
 275                                 verbose("Warning: keysize mismatch for client_host_key: "
 276                                     "actual %d, announced %d",
 277                                      BN_num_bits(client_host_key->rsa->n), bits);
 278                         packet_check_eom();
 279
 280                         authenticated = auth_rhosts_rsa(pw, client_user,
 281                             client_host_key);
 282                         key_free(client_host_key);
 283
 284                         snprintf(info, sizeof info, " ruser %.100s", client_user);
 285                         break;
 286
 287                 case SSH_CMSG_AUTH_RSA:
 288                         if (!options.rsa_authentication) {
 289                                 verbose("RSA authentication disabled.");
 290                                 break;
 291                         }
 292                         /* RSA authentication requested. */
 293                         if ((n = BN_new()) == NULL)
 294                                 fatal("do_authloop: BN_new failed");
 295                         packet_get_bignum(n);
 296                         packet_check_eom();
 297                         authenticated = auth_rsa(pw, n);
 298                         BN_clear_free(n);
 299                         break;
 300
 301                 case SSH_CMSG_AUTH_PASSWORD:
 302                         if (!options.password_authentication) {
 303                                 verbose("Password authentication disabled.");
 304                                 break;
 305                         }
 306                         /*
 307                          * Read user password.  It is in plain text, but was
 308                          * transmitted over the encrypted channel so it is
 309                          * not visible to an outside observer.
 310                          */
 311                         password = packet_get_string(&dlen);
 312                         packet_check_eom();
 313
 314 #ifdef USE_PAM
 315                         /* Do PAM auth with password */
 316                         authenticated = auth_pam_password(pw, password);
 317 #elif defined(HAVE_OSF_SIA)
 318                         /* Do SIA auth with password */
 319                         authenticated = auth_sia_password(authctxt->user,
 320                             password);
 321 #else /* !USE_PAM && !HAVE_OSF_SIA */
 322                         /* Try authentication with the password. */
 323                         authenticated = auth_password(authctxt, password);
 324 #endif /* USE_PAM */
 325
 326                         memset(password, 0, strlen(password));
 327                         xfree(password);
 328                         break;
 329
 330                 case SSH_CMSG_AUTH_TIS:
 331                         debug("rcvd SSH_CMSG_AUTH_TIS");
 332                         if (options.challenge_response_authentication == 1) {
 333                                 char *challenge = get_challenge(authctxt);
 334                                 if (challenge != NULL) {
 335                                         debug("sending challenge '%s'", challenge);
 336                                         packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
 337                                         packet_put_cstring(challenge);
 338                                         xfree(challenge);
 339                                         packet_send();
 340                                         packet_write_wait();
 341                                         continue;
 342                                 }
 343                         }
 344                         break;
 345                 case SSH_CMSG_AUTH_TIS_RESPONSE:
 346                         debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
 347                         if (options.challenge_response_authentication == 1) {
 348                                 char *response = packet_get_string(&dlen);
 349                                 debug("got response '%s'", response);
 350                                 packet_check_eom();
 351                                 authenticated = verify_response(authctxt, response);
 352                                 memset(response, 'r', dlen);
 353                                 xfree(response);
 354                         }
 355                         break;
 356
 357                 default:
 358                         /*
 359                          * Any unknown messages will be ignored (and failure
 360                          * returned) during authentication.
 361                          */
 362                         log("Unknown message during authentication: type %d", type);
 363                         break;
 364                 }
 365 #ifdef BSD_AUTH
 366                 if (authctxt->as) {
 367                         auth_close(authctxt->as);
 368                         authctxt->as = NULL;
 369                 }
 370 #endif
 371                 if (!authctxt->valid && authenticated)
 372                         fatal("INTERNAL ERROR: authenticated invalid user %s",
 373                             authctxt->user);
 374
 375 #ifdef HAVE_CYGWIN
 376                 if (authenticated &&
 377                     !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) {
 378                         packet_disconnect("Authentication rejected for uid %d.",
 379                         pw == NULL ? -1 : pw->pw_uid);
 380                         authenticated = 0;
 381                 }
 382 #else
 383                 /* Special handling for root */
 384                 if (authenticated && authctxt->pw->pw_uid == 0 &&
 385                     !auth_root_allowed(get_authname(type)))
 386                         authenticated = 0;
 387 #endif
 388 #ifdef USE_PAM
 389                 if (authenticated && !do_pam_account(pw->pw_name, client_user))
 390                         authenticated = 0;
 391 #endif
 392
 393                 /* Log before sending the reply */
 394                 auth_log(authctxt, authenticated, get_authname(type), info);
 395
 396                 if (client_user != NULL) {
 397                         xfree(client_user);
 398                         client_user = NULL;
 399                 }
 400
 401                 if (authenticated)
 402                         return;
 403
 404                 if (authctxt->failures++ > AUTH_FAIL_MAX) {
 405 #ifdef WITH_AIXAUTHENTICATE
 406                         loginfailed(authctxt->user,
 407                             get_canonical_hostname(options.verify_reverse_mapping),
 408                             "ssh");
 409 #endif /* WITH_AIXAUTHENTICATE */
 410                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 411                 }
 412
 413                 packet_start(SSH_SMSG_FAILURE);
 414                 packet_send();
 415                 packet_write_wait();
 416         }
 417 }
 418
 419 /*
 420  * Performs authentication of an incoming connection.  Session key has already
 421  * been exchanged and encryption is enabled.
 422  */
 423 void
 424 do_authentication(void)
 425 {
 426         Authctxt *authctxt;
 427         struct passwd *pw;
 428         u_int ulen;
 429         char *p, *user, *style = NULL;
 430
 431         /* Get the name of the user that we wish to log in as. */
 432         packet_read_expect(SSH_CMSG_USER);
 433
 434         /* Get the user name. */
 435         user = packet_get_string(&ulen);
 436         packet_check_eom();
 437
 438 /*modified by binhe*/
 439 #ifndef GSSAPI
 440   /* GSSAPI clients may legitimately send long names (see below) */
 441
 442   if (strlen(user) > 255)
 443     do_authentication_fail_loop();
 444
 445 #else /* GSSAPI */
 446
 447   /* Parse GSSAPI identity from userstring */
 448   user = gssapi_parse_userstring(user);
 449
 450 #endif /* GSSAPI */
 451 /*end of modification*/
 452
 453         if ((style = strchr(user, ':')) != NULL)
 454                 *style++ = '\0';
 455
 456         /* XXX - SSH.com Kerberos v5 braindeath. */
 457         if ((p = strchr(user, '@')) != NULL)
 458                 *p = '\0';
 459
 460         authctxt = authctxt_new();
 461         authctxt->user = user;
 462         authctxt->style = style;
 463
 464         /* Verify that the user is a valid user. */
 465         pw = getpwnam(user);
 466         if (pw && allowed_user(pw)) {
 467                 authctxt->valid = 1;
 468                 pw = pwcopy(pw);
 469         } else {
 470                 debug("do_authentication: illegal user %s", user);
 471                 pw = NULL;
 472         }
 473         authctxt->pw = pw;
 474
 475         setproctitle("%s", pw ? user : "unknown");
 476
 477 #ifdef USE_PAM
 478         start_pam(pw == NULL ? "NOUSER" : user);
 479 #endif
 480
 481         /*
 482          * If we are not running as root, the user must have the same uid as
 483          * the server. (Unless you are running Windows)
 484          */
 485 #ifndef HAVE_CYGWIN
 486         if (getuid() != 0 && pw && pw->pw_uid != getuid())
 487                 packet_disconnect("Cannot change user when server not running as root.");
 488 #endif
 489
 490         /*
 491          * Loop until the user has been authenticated or the connection is
 492          * closed, do_authloop() returns only if authentication is successful
 493          */
 494         do_authloop(authctxt);
 495
 496         /* The user has been authenticated and accepted. */
 497         packet_start(SSH_SMSG_SUCCESS);
 498         packet_send();
 499         packet_write_wait();
 500
 501         /* Perform session preparation. */
 502         do_authenticated(authctxt);
 503 }