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 * Copyright 2008 Sun Microsystems, Inc. All rights reserved. 13 * Use is subject to license terms. 14 */ 15 16 #include "includes.h" 17 RCSID("$OpenBSD: auth1.c,v 1.44 2002/09/26 11:38:43 markus Exp $"); 18 19 #include "xmalloc.h" 20 #include "rsa.h" 21 #include "ssh1.h" 22 #include "packet.h" 23 #include "buffer.h" 24 #include "mpaux.h" 25 #include "log.h" 26 #include "servconf.h" 27 #include "compat.h" 28 #include "auth.h" 29 #include "channels.h" 30 #include "session.h" 31 #include "uidswap.h" 32 33 #ifdef HAVE_BSM 34 #include "bsmaudit.h" 35 extern adt_session_data_t *ah; 36 #endif /* HAVE_BSM */ 37 38 /* import */ 39 extern ServerOptions options; 40 41 /* 42 * convert ssh auth msg type into description 43 */ 44 static char * 45 get_authname(int type) 46 { 47 static char buf[1024]; 48 switch (type) { 49 case SSH_CMSG_AUTH_PASSWORD: 50 return "password"; 51 case SSH_CMSG_AUTH_RSA: 52 return "rsa"; 53 case SSH_CMSG_AUTH_RHOSTS_RSA: 54 return "rhosts-rsa"; 55 case SSH_CMSG_AUTH_RHOSTS: 56 return "rhosts"; 57 case SSH_CMSG_AUTH_TIS: 58 case SSH_CMSG_AUTH_TIS_RESPONSE: 59 return "challenge-response"; 60 #if defined(KRB4) || defined(KRB5) 61 case SSH_CMSG_AUTH_KERBEROS: 62 return "kerberos"; 63 #endif 64 } 65 snprintf(buf, sizeof buf, "bad-auth-msg-%d", type); 66 return buf; 67 } 68 69 /* 70 * read packets, try to authenticate the user and 71 * return only if authentication is successful 72 */ 73 static void 74 do_authloop(Authctxt *authctxt) 75 { 76 int authenticated = 0; 77 u_int bits; 78 Key *client_host_key; 79 BIGNUM *n; 80 char *client_user, *password; 81 char info[1024]; 82 u_int dlen; 83 u_int ulen; 84 int type = 0; 85 struct passwd *pw = authctxt->pw; 86 87 debug("Attempting authentication for %s%.100s.", 88 authctxt->valid ? "" : "illegal user ", authctxt->user); 89 90 /* If the user has no password, accept authentication immediately. */ 91 if (options.password_authentication && 92 #if defined(KRB4) || defined(KRB5) 93 (!options.kerberos_authentication || options.kerberos_or_local_passwd) && 94 #endif 95 auth_password(authctxt, "")) { 96 auth_log(authctxt, 1, "without authentication", ""); 97 return; 98 } 99 100 /* Indicate that authentication is needed. */ 101 packet_start(SSH_SMSG_FAILURE); 102 packet_send(); 103 packet_write_wait(); 104 105 client_user = NULL; 106 107 for ( ;; ) { 108 /* default to fail */ 109 authenticated = 0; 110 111 info[0] = '\0'; 112 113 /* Get a packet from the client. */ 114 authctxt->v1_auth_type = type = packet_read(); 115 authctxt->v1_auth_name = get_authname(type); 116 117 authctxt->attempt++; 118 119 /* Process the packet. */ 120 switch (type) { 121 122 #if defined(KRB4) || defined(KRB5) 123 case SSH_CMSG_AUTH_KERBEROS: 124 if (!options.kerberos_authentication) { 125 verbose("Kerberos authentication disabled."); 126 } else { 127 char *kdata = packet_get_string(&dlen); 128 packet_check_eom(); 129 130 if (kdata[0] == 4) { /* KRB_PROT_VERSION */ 131 #ifdef KRB4 132 KTEXT_ST tkt, reply; 133 tkt.length = dlen; 134 if (tkt.length < MAX_KTXT_LEN) 135 memcpy(tkt.dat, kdata, tkt.length); 136 137 if (auth_krb4(authctxt, &tkt, 138 &client_user, &reply)) { 139 authenticated = 1; 140 snprintf(info, sizeof(info), 141 " tktuser %.100s", 142 client_user); 143 144 packet_start( 145 SSH_SMSG_AUTH_KERBEROS_RESPONSE); 146 packet_put_string((char *) 147 reply.dat, reply.length); 148 packet_send(); 149 packet_write_wait(); 150 } 151 #endif /* KRB4 */ 152 } else { 153 #ifdef KRB5 154 krb5_data tkt, reply; 155 tkt.length = dlen; 156 tkt.data = kdata; 157 158 if (auth_krb5(authctxt, &tkt, 159 &client_user, &reply)) { 160 authenticated = 1; 161 snprintf(info, sizeof(info), 162 " tktuser %.100s", 163 client_user); 164 165 /* Send response to client */ 166 packet_start( 167 SSH_SMSG_AUTH_KERBEROS_RESPONSE); 168 packet_put_string((char *) 169 reply.data, reply.length); 170 packet_send(); 171 packet_write_wait(); 172 173 if (reply.length) 174 xfree(reply.data); 175 } 176 #endif /* KRB5 */ 177 } 178 xfree(kdata); 179 } 180 break; 181 #endif /* KRB4 || KRB5 */ 182 183 #if defined(AFS) || defined(KRB5) 184 /* XXX - punt on backward compatibility here. */ 185 case SSH_CMSG_HAVE_KERBEROS_TGT: 186 packet_send_debug("Kerberos TGT passing disabled before authentication."); 187 break; 188 #ifdef AFS 189 case SSH_CMSG_HAVE_AFS_TOKEN: 190 packet_send_debug("AFS token passing disabled before authentication."); 191 break; 192 #endif /* AFS */ 193 #endif /* AFS || KRB5 */ 194 195 case SSH_CMSG_AUTH_RHOSTS: 196 if (!options.rhosts_authentication) { 197 verbose("Rhosts authentication disabled."); 198 break; 199 } 200 /* 201 * Get client user name. Note that we just have to 202 * trust the client; this is one reason why rhosts 203 * authentication is insecure. (Another is 204 * IP-spoofing on a local network.) 205 */ 206 client_user = packet_get_string(&ulen); 207 packet_check_eom(); 208 209 /* Try to authenticate using /etc/hosts.equiv and .rhosts. */ 210 authenticated = auth_rhosts(pw, client_user); 211 212 snprintf(info, sizeof info, " ruser %.100s", client_user); 213 break; 214 215 case SSH_CMSG_AUTH_RHOSTS_RSA: 216 if (!options.rhosts_rsa_authentication) { 217 verbose("Rhosts with RSA authentication disabled."); 218 break; 219 } 220 /* 221 * Get client user name. Note that we just have to 222 * trust the client; root on the client machine can 223 * claim to be any user. 224 */ 225 client_user = packet_get_string(&ulen); 226 227 /* Get the client host key. */ 228 client_host_key = key_new(KEY_RSA1); 229 bits = packet_get_int(); 230 packet_get_bignum(client_host_key->rsa->e); 231 packet_get_bignum(client_host_key->rsa->n); 232 233 if (bits != BN_num_bits(client_host_key->rsa->n)) 234 verbose("Warning: keysize mismatch for client_host_key: " 235 "actual %d, announced %d", 236 BN_num_bits(client_host_key->rsa->n), bits); 237 packet_check_eom(); 238 239 authenticated = auth_rhosts_rsa(pw, client_user, 240 client_host_key); 241 key_free(client_host_key); 242 243 snprintf(info, sizeof info, " ruser %.100s", client_user); 244 break; 245 246 case SSH_CMSG_AUTH_RSA: 247 if (!options.rsa_authentication) { 248 verbose("RSA authentication disabled."); 249 break; 250 } 251 /* RSA authentication requested. */ 252 if ((n = BN_new()) == NULL) 253 fatal("do_authloop: BN_new failed"); 254 packet_get_bignum(n); 255 packet_check_eom(); 256 authenticated = auth_rsa(pw, n); 257 BN_clear_free(n); 258 break; 259 260 case SSH_CMSG_AUTH_PASSWORD: 261 authctxt->init_attempt++; 262 263 if (!options.password_authentication) { 264 verbose("Password authentication disabled."); 265 break; 266 } 267 /* 268 * Read user password. It is in plain text, but was 269 * transmitted over the encrypted channel so it is 270 * not visible to an outside observer. 271 */ 272 password = packet_get_string(&dlen); 273 packet_check_eom(); 274 275 /* Try authentication with the password. */ 276 if (authctxt->init_failures < 277 options.max_init_auth_tries) 278 authenticated = 279 auth_password(authctxt, password); 280 281 memset(password, 0, strlen(password)); 282 xfree(password); 283 break; 284 285 case SSH_CMSG_AUTH_TIS: 286 debug("rcvd SSH_CMSG_AUTH_TIS"); 287 if (options.challenge_response_authentication == 1) { 288 char *challenge = get_challenge(authctxt); 289 if (challenge != NULL) { 290 debug("sending challenge '%s'", challenge); 291 packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); 292 packet_put_cstring(challenge); 293 xfree(challenge); 294 packet_send(); 295 packet_write_wait(); 296 continue; 297 } 298 } 299 break; 300 case SSH_CMSG_AUTH_TIS_RESPONSE: 301 debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); 302 if (options.challenge_response_authentication == 1) { 303 char *response = packet_get_string(&dlen); 304 debug("got response '%s'", response); 305 packet_check_eom(); 306 authenticated = verify_response(authctxt, response); 307 memset(response, 'r', dlen); 308 xfree(response); 309 } 310 break; 311 312 default: 313 /* 314 * Any unknown messages will be ignored (and failure 315 * returned) during authentication. 316 */ 317 log("Unknown message during authentication: type %d", type); 318 break; 319 } 320 #ifdef BSD_AUTH 321 if (authctxt->as) { 322 auth_close(authctxt->as); 323 authctxt->as = NULL; 324 } 325 #endif 326 if (!authctxt->valid && authenticated) { 327 authenticated = 0; 328 log("Ignoring authenticated invalid user %s", 329 authctxt->user); 330 } 331 332 #ifdef _UNICOS 333 if (type == SSH_CMSG_AUTH_PASSWORD && !authenticated) 334 cray_login_failure(authctxt->user, IA_UDBERR); 335 if (authenticated && cray_access_denied(authctxt->user)) { 336 authenticated = 0; 337 fatal("Access denied for user %s.",authctxt->user); 338 } 339 #endif /* _UNICOS */ 340 341 #ifdef HAVE_CYGWIN 342 if (authenticated && 343 !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) { 344 packet_disconnect("Authentication rejected for uid %d.", 345 pw == NULL ? -1 : pw->pw_uid); 346 authenticated = 0; 347 } 348 #else 349 /* Special handling for root */ 350 if (authenticated && authctxt->pw->pw_uid == 0 && 351 !auth_root_allowed(get_authname(type))) 352 authenticated = 0; 353 #endif 354 #ifdef USE_PAM 355 if (authenticated && type != SSH_CMSG_AUTH_PASSWORD) 356 authenticated = do_pam_non_initial_userauth(authctxt); 357 else if (authenticated && !AUTHPAM_DONE(authctxt)) 358 authenticated = 0; 359 360 if (!authenticated) 361 authctxt->pam_retval = AUTHPAM_ERROR(authctxt, 362 PAM_PERM_DENIED); 363 #endif /* USE_PAM */ 364 365 /* Log before sending the reply */ 366 auth_log(authctxt, authenticated, get_authname(type), info); 367 368 if (client_user != NULL) { 369 xfree(client_user); 370 client_user = NULL; 371 } 372 373 if (authenticated) 374 return; 375 376 if (type == SSH_CMSG_AUTH_PASSWORD) 377 authctxt->init_failures++; 378 379 if (authctxt->failures++ > options.max_auth_tries) { 380 #ifdef HAVE_BSM 381 fatal_remove_cleanup(audit_failed_login_cleanup, 382 authctxt); 383 audit_sshd_login_failure(&ah, PAM_MAXTRIES, 384 authctxt->user); 385 #endif /* HAVE_BSM */ 386 packet_disconnect(AUTH_FAIL_MSG, authctxt->user); 387 } 388 389 packet_start(SSH_SMSG_FAILURE); 390 packet_send(); 391 packet_write_wait(); 392 } 393 } 394 395 /* 396 * Performs authentication of an incoming connection. Session key has already 397 * been exchanged and encryption is enabled. 398 */ 399 Authctxt * 400 do_authentication(void) 401 { 402 Authctxt *authctxt; 403 u_int ulen; 404 char *user, *style = NULL; 405 406 /* Get the name of the user that we wish to log in as. */ 407 packet_read_expect(SSH_CMSG_USER); 408 409 /* Get the user name. */ 410 user = packet_get_string(&ulen); 411 packet_check_eom(); 412 413 if ((style = strchr(user, ':')) != NULL) 414 *style++ = '\0'; 415 416 #ifdef KRB5 417 /* XXX - SSH.com Kerberos v5 braindeath. */ 418 if ((datafellows & SSH_BUG_K5USER) && 419 options.kerberos_authentication) { 420 char *p; 421 if ((p = strchr(user, '@')) != NULL) 422 *p = '\0'; 423 } 424 #endif 425 426 authctxt = authctxt_new(); 427 authctxt->user = user; 428 authctxt->style = style; 429 430 #ifdef HAVE_BSM 431 fatal_add_cleanup(audit_failed_login_cleanup, authctxt); 432 #endif /* HAVE_BSM */ 433 434 /* Verify that the user is a valid user. */ 435 if ((authctxt->pw = getpwnamallow(user)) != NULL) { 436 authctxt->valid = 1; 437 } else { 438 authctxt->valid = 0; 439 debug("do_authentication: illegal user %s", user); 440 } 441 442 setproctitle("%s", authctxt->pw ? user : "unknown"); 443 444 /* 445 * If we are not running as root, the user must have the same uid as 446 * the server. (Unless you are running Windows) 447 */ 448 #ifndef HAVE_CYGWIN 449 if (getuid() != 0 && authctxt->pw && 450 authctxt->pw->pw_uid != getuid()) 451 packet_disconnect("Cannot change user when server not running as root."); 452 #endif 453 454 /* 455 * Loop until the user has been authenticated or the connection is 456 * closed, do_authloop() returns only if authentication is successful 457 */ 458 do_authloop(authctxt); 459 460 /* The user has been authenticated and accepted. */ 461 packet_start(SSH_SMSG_SUCCESS); 462 packet_send(); 463 packet_write_wait(); 464 465 return (authctxt); 466 } 467