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 2007 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 #pragma ident "%Z%%M% %I% %E% SMI" 20 21 #include "xmalloc.h" 22 #include "rsa.h" 23 #include "ssh1.h" 24 #include "packet.h" 25 #include "buffer.h" 26 #include "mpaux.h" 27 #include "log.h" 28 #include "servconf.h" 29 #include "compat.h" 30 #include "auth.h" 31 #include "channels.h" 32 #include "session.h" 33 #include "uidswap.h" 34 35 #ifdef HAVE_BSM 36 #include "bsmaudit.h" 37 extern adt_session_data_t *ah; 38 #endif /* HAVE_BSM */ 39 40 /* import */ 41 extern ServerOptions options; 42 43 /* 44 * convert ssh auth msg type into description 45 */ 46 static char * 47 get_authname(int type) 48 { 49 static char buf[1024]; 50 switch (type) { 51 case SSH_CMSG_AUTH_PASSWORD: 52 return "password"; 53 case SSH_CMSG_AUTH_RSA: 54 return "rsa"; 55 case SSH_CMSG_AUTH_RHOSTS_RSA: 56 return "rhosts-rsa"; 57 case SSH_CMSG_AUTH_RHOSTS: 58 return "rhosts"; 59 case SSH_CMSG_AUTH_TIS: 60 case SSH_CMSG_AUTH_TIS_RESPONSE: 61 return "challenge-response"; 62 #if defined(KRB4) || defined(KRB5) 63 case SSH_CMSG_AUTH_KERBEROS: 64 return "kerberos"; 65 #endif 66 } 67 snprintf(buf, sizeof buf, "bad-auth-msg-%d", type); 68 return buf; 69 } 70 71 /* 72 * read packets, try to authenticate the user and 73 * return only if authentication is successful 74 */ 75 static void 76 do_authloop(Authctxt *authctxt) 77 { 78 int authenticated = 0; 79 u_int bits; 80 Key *client_host_key; 81 BIGNUM *n; 82 char *client_user, *password; 83 char info[1024]; 84 u_int dlen; 85 u_int ulen; 86 int type = 0; 87 struct passwd *pw = authctxt->pw; 88 89 debug("Attempting authentication for %s%.100s.", 90 authctxt->valid ? "" : "illegal user ", authctxt->user); 91 92 /* If the user has no password, accept authentication immediately. */ 93 if (options.password_authentication && 94 #if defined(KRB4) || defined(KRB5) 95 (!options.kerberos_authentication || options.kerberos_or_local_passwd) && 96 #endif 97 auth_password(authctxt, "")) { 98 auth_log(authctxt, 1, "without authentication", ""); 99 return; 100 } 101 102 /* Indicate that authentication is needed. */ 103 packet_start(SSH_SMSG_FAILURE); 104 packet_send(); 105 packet_write_wait(); 106 107 client_user = NULL; 108 109 for ( ;; ) { 110 /* default to fail */ 111 authenticated = 0; 112 113 info[0] = '\0'; 114 115 /* Get a packet from the client. */ 116 authctxt->v1_auth_type = type = packet_read(); 117 authctxt->v1_auth_name = get_authname(type); 118 119 authctxt->attempt++; 120 121 /* Process the packet. */ 122 switch (type) { 123 124 #if defined(KRB4) || defined(KRB5) 125 case SSH_CMSG_AUTH_KERBEROS: 126 if (!options.kerberos_authentication) { 127 verbose("Kerberos authentication disabled."); 128 } else { 129 char *kdata = packet_get_string(&dlen); 130 packet_check_eom(); 131 132 if (kdata[0] == 4) { /* KRB_PROT_VERSION */ 133 #ifdef KRB4 134 KTEXT_ST tkt, reply; 135 tkt.length = dlen; 136 if (tkt.length < MAX_KTXT_LEN) 137 memcpy(tkt.dat, kdata, tkt.length); 138 139 if (auth_krb4(authctxt, &tkt, 140 &client_user, &reply)) { 141 authenticated = 1; 142 snprintf(info, sizeof(info), 143 " tktuser %.100s", 144 client_user); 145 146 packet_start( 147 SSH_SMSG_AUTH_KERBEROS_RESPONSE); 148 packet_put_string((char *) 149 reply.dat, reply.length); 150 packet_send(); 151 packet_write_wait(); 152 } 153 #endif /* KRB4 */ 154 } else { 155 #ifdef KRB5 156 krb5_data tkt, reply; 157 tkt.length = dlen; 158 tkt.data = kdata; 159 160 if (auth_krb5(authctxt, &tkt, 161 &client_user, &reply)) { 162 authenticated = 1; 163 snprintf(info, sizeof(info), 164 " tktuser %.100s", 165 client_user); 166 167 /* Send response to client */ 168 packet_start( 169 SSH_SMSG_AUTH_KERBEROS_RESPONSE); 170 packet_put_string((char *) 171 reply.data, reply.length); 172 packet_send(); 173 packet_write_wait(); 174 175 if (reply.length) 176 xfree(reply.data); 177 } 178 #endif /* KRB5 */ 179 } 180 xfree(kdata); 181 } 182 break; 183 #endif /* KRB4 || KRB5 */ 184 185 #if defined(AFS) || defined(KRB5) 186 /* XXX - punt on backward compatibility here. */ 187 case SSH_CMSG_HAVE_KERBEROS_TGT: 188 packet_send_debug("Kerberos TGT passing disabled before authentication."); 189 break; 190 #ifdef AFS 191 case SSH_CMSG_HAVE_AFS_TOKEN: 192 packet_send_debug("AFS token passing disabled before authentication."); 193 break; 194 #endif /* AFS */ 195 #endif /* AFS || KRB5 */ 196 197 case SSH_CMSG_AUTH_RHOSTS: 198 if (!options.rhosts_authentication) { 199 verbose("Rhosts authentication disabled."); 200 break; 201 } 202 /* 203 * Get client user name. Note that we just have to 204 * trust the client; this is one reason why rhosts 205 * authentication is insecure. (Another is 206 * IP-spoofing on a local network.) 207 */ 208 client_user = packet_get_string(&ulen); 209 packet_check_eom(); 210 211 /* Try to authenticate using /etc/hosts.equiv and .rhosts. */ 212 authenticated = auth_rhosts(pw, client_user); 213 214 snprintf(info, sizeof info, " ruser %.100s", client_user); 215 break; 216 217 case SSH_CMSG_AUTH_RHOSTS_RSA: 218 if (!options.rhosts_rsa_authentication) { 219 verbose("Rhosts with RSA authentication disabled."); 220 break; 221 } 222 /* 223 * Get client user name. Note that we just have to 224 * trust the client; root on the client machine can 225 * claim to be any user. 226 */ 227 client_user = packet_get_string(&ulen); 228 229 /* Get the client host key. */ 230 client_host_key = key_new(KEY_RSA1); 231 bits = packet_get_int(); 232 packet_get_bignum(client_host_key->rsa->e); 233 packet_get_bignum(client_host_key->rsa->n); 234 235 if (bits != BN_num_bits(client_host_key->rsa->n)) 236 verbose("Warning: keysize mismatch for client_host_key: " 237 "actual %d, announced %d", 238 BN_num_bits(client_host_key->rsa->n), bits); 239 packet_check_eom(); 240 241 authenticated = auth_rhosts_rsa(pw, client_user, 242 client_host_key); 243 key_free(client_host_key); 244 245 snprintf(info, sizeof info, " ruser %.100s", client_user); 246 break; 247 248 case SSH_CMSG_AUTH_RSA: 249 if (!options.rsa_authentication) { 250 verbose("RSA authentication disabled."); 251 break; 252 } 253 /* RSA authentication requested. */ 254 if ((n = BN_new()) == NULL) 255 fatal("do_authloop: BN_new failed"); 256 packet_get_bignum(n); 257 packet_check_eom(); 258 authenticated = auth_rsa(pw, n); 259 BN_clear_free(n); 260 break; 261 262 case SSH_CMSG_AUTH_PASSWORD: 263 authctxt->init_attempt++; 264 265 if (!options.password_authentication) { 266 verbose("Password authentication disabled."); 267 break; 268 } 269 /* 270 * Read user password. It is in plain text, but was 271 * transmitted over the encrypted channel so it is 272 * not visible to an outside observer. 273 */ 274 password = packet_get_string(&dlen); 275 packet_check_eom(); 276 277 /* Try authentication with the password. */ 278 if (authctxt->init_failures < 279 options.max_init_auth_tries) 280 authenticated = 281 auth_password(authctxt, password); 282 283 memset(password, 0, strlen(password)); 284 xfree(password); 285 break; 286 287 case SSH_CMSG_AUTH_TIS: 288 debug("rcvd SSH_CMSG_AUTH_TIS"); 289 if (options.challenge_response_authentication == 1) { 290 char *challenge = get_challenge(authctxt); 291 if (challenge != NULL) { 292 debug("sending challenge '%s'", challenge); 293 packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); 294 packet_put_cstring(challenge); 295 xfree(challenge); 296 packet_send(); 297 packet_write_wait(); 298 continue; 299 } 300 } 301 break; 302 case SSH_CMSG_AUTH_TIS_RESPONSE: 303 debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); 304 if (options.challenge_response_authentication == 1) { 305 char *response = packet_get_string(&dlen); 306 debug("got response '%s'", response); 307 packet_check_eom(); 308 authenticated = verify_response(authctxt, response); 309 memset(response, 'r', dlen); 310 xfree(response); 311 } 312 break; 313 314 default: 315 /* 316 * Any unknown messages will be ignored (and failure 317 * returned) during authentication. 318 */ 319 log("Unknown message during authentication: type %d", type); 320 break; 321 } 322 #ifdef BSD_AUTH 323 if (authctxt->as) { 324 auth_close(authctxt->as); 325 authctxt->as = NULL; 326 } 327 #endif 328 if (!authctxt->valid && authenticated) { 329 authenticated = 0; 330 log("Ignoring authenticated invalid user %s", 331 authctxt->user); 332 } 333 334 #ifdef _UNICOS 335 if (type == SSH_CMSG_AUTH_PASSWORD && !authenticated) 336 cray_login_failure(authctxt->user, IA_UDBERR); 337 if (authenticated && cray_access_denied(authctxt->user)) { 338 authenticated = 0; 339 fatal("Access denied for user %s.",authctxt->user); 340 } 341 #endif /* _UNICOS */ 342 343 #ifdef HAVE_CYGWIN 344 if (authenticated && 345 !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) { 346 packet_disconnect("Authentication rejected for uid %d.", 347 pw == NULL ? -1 : pw->pw_uid); 348 authenticated = 0; 349 } 350 #else 351 /* Special handling for root */ 352 if (authenticated && authctxt->pw->pw_uid == 0 && 353 !auth_root_allowed(get_authname(type))) 354 authenticated = 0; 355 #endif 356 #ifdef USE_PAM 357 if (authenticated && type != SSH_CMSG_AUTH_PASSWORD) 358 authenticated = do_pam_non_initial_userauth(authctxt); 359 else if (authenticated && !AUTHPAM_DONE(authctxt)) 360 authenticated = 0; 361 362 if (!authenticated) 363 authctxt->pam_retval = AUTHPAM_ERROR(authctxt, 364 PAM_PERM_DENIED); 365 #endif /* USE_PAM */ 366 367 /* Log before sending the reply */ 368 auth_log(authctxt, authenticated, get_authname(type), info); 369 370 if (client_user != NULL) { 371 xfree(client_user); 372 client_user = NULL; 373 } 374 375 if (authenticated) 376 return; 377 378 if (type == SSH_CMSG_AUTH_PASSWORD) 379 authctxt->init_failures++; 380 381 if (authctxt->failures++ > options.max_auth_tries) { 382 #ifdef HAVE_BSM 383 fatal_remove_cleanup(audit_failed_login_cleanup, 384 authctxt); 385 audit_sshd_login_failure(&ah, PAM_MAXTRIES); 386 #endif /* HAVE_BSM */ 387 packet_disconnect(AUTH_FAIL_MSG, authctxt->user); 388 } 389 390 packet_start(SSH_SMSG_FAILURE); 391 packet_send(); 392 packet_write_wait(); 393 } 394 } 395 396 /* 397 * Performs authentication of an incoming connection. Session key has already 398 * been exchanged and encryption is enabled. 399 */ 400 Authctxt * 401 do_authentication(void) 402 { 403 Authctxt *authctxt; 404 u_int ulen; 405 char *user, *style = NULL; 406 407 /* Get the name of the user that we wish to log in as. */ 408 packet_read_expect(SSH_CMSG_USER); 409 410 /* Get the user name. */ 411 user = packet_get_string(&ulen); 412 packet_check_eom(); 413 414 if ((style = strchr(user, ':')) != NULL) 415 *style++ = '\0'; 416 417 #ifdef KRB5 418 /* XXX - SSH.com Kerberos v5 braindeath. */ 419 if ((datafellows & SSH_BUG_K5USER) && 420 options.kerberos_authentication) { 421 char *p; 422 if ((p = strchr(user, '@')) != NULL) 423 *p = '\0'; 424 } 425 #endif 426 427 authctxt = authctxt_new(); 428 authctxt->user = user; 429 authctxt->style = style; 430 431 #ifdef HAVE_BSM 432 fatal_add_cleanup(audit_failed_login_cleanup, authctxt); 433 #endif /* HAVE_BSM */ 434 435 /* Verify that the user is a valid user. */ 436 if ((authctxt->pw = getpwnamallow(user)) != NULL) { 437 authctxt->valid = 1; 438 } else { 439 authctxt->valid = 0; 440 debug("do_authentication: illegal user %s", user); 441 } 442 443 setproctitle("%s", authctxt->pw ? user : "unknown"); 444 445 /* 446 * If we are not running as root, the user must have the same uid as 447 * the server. (Unless you are running Windows) 448 */ 449 #ifndef HAVE_CYGWIN 450 if (getuid() != 0 && authctxt->pw && 451 authctxt->pw->pw_uid != getuid()) 452 packet_disconnect("Cannot change user when server not running as root."); 453 #endif 454 455 /* 456 * Loop until the user has been authenticated or the connection is 457 * closed, do_authloop() returns only if authentication is successful 458 */ 459 do_authloop(authctxt); 460 461 /* The user has been authenticated and accepted. */ 462 packet_start(SSH_SMSG_SUCCESS); 463 packet_send(); 464 packet_write_wait(); 465 466 return (authctxt); 467 } 468