1 /* $OpenBSD: auth2.c,v 1.123 2011/03/10 02:52:57 djm Exp $ */ 2 /* 3 * Copyright (c) 2000 Markus Friedl. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include "includes.h" 27 __RCSID("$FreeBSD$"); 28 29 #include <sys/types.h> 30 #include <sys/stat.h> 31 #include <sys/uio.h> 32 33 #include <fcntl.h> 34 #include <pwd.h> 35 #include <stdarg.h> 36 #include <string.h> 37 #include <unistd.h> 38 39 #include "atomicio.h" 40 #include "xmalloc.h" 41 #include "ssh2.h" 42 #include "packet.h" 43 #include "log.h" 44 #include "buffer.h" 45 #include "servconf.h" 46 #include "compat.h" 47 #include "key.h" 48 #include "hostfile.h" 49 #include "auth.h" 50 #include "dispatch.h" 51 #include "pathnames.h" 52 #include "buffer.h" 53 #include "canohost.h" 54 55 #ifdef GSSAPI 56 #include "ssh-gss.h" 57 #endif 58 #include "monitor_wrap.h" 59 60 /* import */ 61 extern ServerOptions options; 62 extern u_char *session_id2; 63 extern u_int session_id2_len; 64 extern Buffer loginmsg; 65 66 /* methods */ 67 68 extern Authmethod method_none; 69 extern Authmethod method_pubkey; 70 extern Authmethod method_passwd; 71 extern Authmethod method_kbdint; 72 extern Authmethod method_hostbased; 73 #ifdef GSSAPI 74 extern Authmethod method_gssapi; 75 #endif 76 #ifdef JPAKE 77 extern Authmethod method_jpake; 78 #endif 79 80 Authmethod *authmethods[] = { 81 &method_none, 82 &method_pubkey, 83 #ifdef GSSAPI 84 &method_gssapi, 85 #endif 86 #ifdef JPAKE 87 &method_jpake, 88 #endif 89 &method_passwd, 90 &method_kbdint, 91 &method_hostbased, 92 NULL 93 }; 94 95 /* protocol */ 96 97 static void input_service_request(int, u_int32_t, void *); 98 static void input_userauth_request(int, u_int32_t, void *); 99 100 /* helper */ 101 static Authmethod *authmethod_lookup(const char *); 102 static char *authmethods_get(void); 103 104 char * 105 auth2_read_banner(void) 106 { 107 struct stat st; 108 char *banner = NULL; 109 size_t len, n; 110 int fd; 111 112 if ((fd = open(options.banner, O_RDONLY)) == -1) 113 return (NULL); 114 if (fstat(fd, &st) == -1) { 115 close(fd); 116 return (NULL); 117 } 118 if (st.st_size > 1*1024*1024) { 119 close(fd); 120 return (NULL); 121 } 122 123 len = (size_t)st.st_size; /* truncate */ 124 banner = xmalloc(len + 1); 125 n = atomicio(read, fd, banner, len); 126 close(fd); 127 128 if (n != len) { 129 xfree(banner); 130 return (NULL); 131 } 132 banner[n] = '\0'; 133 134 return (banner); 135 } 136 137 void 138 userauth_send_banner(const char *msg) 139 { 140 if (datafellows & SSH_BUG_BANNER) 141 return; 142 143 packet_start(SSH2_MSG_USERAUTH_BANNER); 144 packet_put_cstring(msg); 145 packet_put_cstring(""); /* language, unused */ 146 packet_send(); 147 debug("%s: sent", __func__); 148 } 149 150 static void 151 userauth_banner(void) 152 { 153 char *banner = NULL; 154 155 if (options.banner == NULL || 156 strcasecmp(options.banner, "none") == 0 || 157 (datafellows & SSH_BUG_BANNER) != 0) 158 return; 159 160 if ((banner = PRIVSEP(auth2_read_banner())) == NULL) 161 goto done; 162 userauth_send_banner(banner); 163 164 done: 165 if (banner) 166 xfree(banner); 167 } 168 169 /* 170 * loop until authctxt->success == TRUE 171 */ 172 void 173 do_authentication2(Authctxt *authctxt) 174 { 175 dispatch_init(&dispatch_protocol_error); 176 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); 177 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); 178 } 179 180 /*ARGSUSED*/ 181 static void 182 input_service_request(int type, u_int32_t seq, void *ctxt) 183 { 184 Authctxt *authctxt = ctxt; 185 u_int len; 186 int acceptit = 0; 187 char *service = packet_get_cstring(&len); 188 packet_check_eom(); 189 190 if (authctxt == NULL) 191 fatal("input_service_request: no authctxt"); 192 193 if (strcmp(service, "ssh-userauth") == 0) { 194 if (!authctxt->success) { 195 acceptit = 1; 196 /* now we can handle user-auth requests */ 197 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); 198 } 199 } 200 /* XXX all other service requests are denied */ 201 202 if (acceptit) { 203 packet_start(SSH2_MSG_SERVICE_ACCEPT); 204 packet_put_cstring(service); 205 packet_send(); 206 packet_write_wait(); 207 } else { 208 debug("bad service request %s", service); 209 packet_disconnect("bad service request %s", service); 210 } 211 xfree(service); 212 } 213 214 /*ARGSUSED*/ 215 static void 216 input_userauth_request(int type, u_int32_t seq, void *ctxt) 217 { 218 Authctxt *authctxt = ctxt; 219 Authmethod *m = NULL; 220 char *user, *service, *method, *style = NULL; 221 int authenticated = 0; 222 #ifdef HAVE_LOGIN_CAP 223 login_cap_t *lc; 224 const char *from_host, *from_ip; 225 226 from_host = get_canonical_hostname(options.use_dns); 227 from_ip = get_remote_ipaddr(); 228 #endif 229 230 if (authctxt == NULL) 231 fatal("input_userauth_request: no authctxt"); 232 233 user = packet_get_cstring(NULL); 234 service = packet_get_cstring(NULL); 235 method = packet_get_cstring(NULL); 236 debug("userauth-request for user %s service %s method %s", user, service, method); 237 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); 238 239 if ((style = strchr(user, ':')) != NULL) 240 *style++ = 0; 241 242 if (authctxt->attempt++ == 0) { 243 /* setup auth context */ 244 authctxt->pw = PRIVSEP(getpwnamallow(user)); 245 authctxt->user = xstrdup(user); 246 if (authctxt->pw && strcmp(service, "ssh-connection")==0) { 247 authctxt->valid = 1; 248 debug2("input_userauth_request: setting up authctxt for %s", user); 249 } else { 250 logit("input_userauth_request: invalid user %s", user); 251 authctxt->pw = fakepw(); 252 #ifdef SSH_AUDIT_EVENTS 253 PRIVSEP(audit_event(SSH_INVALID_USER)); 254 #endif 255 } 256 #ifdef USE_PAM 257 if (options.use_pam) 258 PRIVSEP(start_pam(authctxt)); 259 #endif 260 setproctitle("%s%s", authctxt->valid ? user : "unknown", 261 use_privsep ? " [net]" : ""); 262 authctxt->service = xstrdup(service); 263 authctxt->style = style ? xstrdup(style) : NULL; 264 if (use_privsep) 265 mm_inform_authserv(service, style); 266 userauth_banner(); 267 } else if (strcmp(user, authctxt->user) != 0 || 268 strcmp(service, authctxt->service) != 0) { 269 packet_disconnect("Change of username or service not allowed: " 270 "(%s,%s) -> (%s,%s)", 271 authctxt->user, authctxt->service, user, service); 272 } 273 274 #ifdef HAVE_LOGIN_CAP 275 if (authctxt->pw != NULL) { 276 lc = login_getpwclass(authctxt->pw); 277 if (lc == NULL) 278 lc = login_getclassbyname(NULL, authctxt->pw); 279 if (!auth_hostok(lc, from_host, from_ip)) { 280 logit("Denied connection for %.200s from %.200s [%.200s].", 281 authctxt->pw->pw_name, from_host, from_ip); 282 packet_disconnect("Sorry, you are not allowed to connect."); 283 } 284 if (!auth_timeok(lc, time(NULL))) { 285 logit("LOGIN %.200s REFUSED (TIME) FROM %.200s", 286 authctxt->pw->pw_name, from_host); 287 packet_disconnect("Logins not available right now."); 288 } 289 login_close(lc); 290 lc = NULL; 291 } 292 #endif /* HAVE_LOGIN_CAP */ 293 294 /* reset state */ 295 auth2_challenge_stop(authctxt); 296 #ifdef JPAKE 297 auth2_jpake_stop(authctxt); 298 #endif 299 300 #ifdef GSSAPI 301 /* XXX move to auth2_gssapi_stop() */ 302 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 303 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 304 #endif 305 306 authctxt->postponed = 0; 307 authctxt->server_caused_failure = 0; 308 309 /* try to authenticate user */ 310 m = authmethod_lookup(method); 311 if (m != NULL && authctxt->failures < options.max_authtries) { 312 debug2("input_userauth_request: try method %s", method); 313 authenticated = m->userauth(authctxt); 314 } 315 userauth_finish(authctxt, authenticated, method); 316 317 xfree(service); 318 xfree(user); 319 xfree(method); 320 } 321 322 void 323 userauth_finish(Authctxt *authctxt, int authenticated, char *method) 324 { 325 char *methods; 326 327 if (!authctxt->valid && authenticated) 328 fatal("INTERNAL ERROR: authenticated invalid user %s", 329 authctxt->user); 330 331 /* Special handling for root */ 332 if (authenticated && authctxt->pw->pw_uid == 0 && 333 !auth_root_allowed(method)) { 334 authenticated = 0; 335 #ifdef SSH_AUDIT_EVENTS 336 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); 337 #endif 338 } 339 340 #ifdef USE_PAM 341 if (options.use_pam && authenticated) { 342 if (!PRIVSEP(do_pam_account())) { 343 /* if PAM returned a message, send it to the user */ 344 if (buffer_len(&loginmsg) > 0) { 345 buffer_append(&loginmsg, "\0", 1); 346 userauth_send_banner(buffer_ptr(&loginmsg)); 347 packet_write_wait(); 348 } 349 fatal("Access denied for user %s by PAM account " 350 "configuration", authctxt->user); 351 } 352 } 353 #endif 354 355 #ifdef _UNICOS 356 if (authenticated && cray_access_denied(authctxt->user)) { 357 authenticated = 0; 358 fatal("Access denied for user %s.",authctxt->user); 359 } 360 #endif /* _UNICOS */ 361 362 /* Log before sending the reply */ 363 auth_log(authctxt, authenticated, method, " ssh2"); 364 365 if (authctxt->postponed) 366 return; 367 368 /* XXX todo: check if multiple auth methods are needed */ 369 if (authenticated == 1) { 370 /* turn off userauth */ 371 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); 372 packet_start(SSH2_MSG_USERAUTH_SUCCESS); 373 packet_send(); 374 packet_write_wait(); 375 /* now we can break out */ 376 authctxt->success = 1; 377 } else { 378 379 /* Allow initial try of "none" auth without failure penalty */ 380 if (!authctxt->server_caused_failure && 381 (authctxt->attempt > 1 || strcmp(method, "none") != 0)) 382 authctxt->failures++; 383 if (authctxt->failures >= options.max_authtries) { 384 #ifdef SSH_AUDIT_EVENTS 385 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES)); 386 #endif 387 packet_disconnect(AUTH_FAIL_MSG, authctxt->user); 388 } 389 methods = authmethods_get(); 390 packet_start(SSH2_MSG_USERAUTH_FAILURE); 391 packet_put_cstring(methods); 392 packet_put_char(0); /* XXX partial success, unused */ 393 packet_send(); 394 packet_write_wait(); 395 xfree(methods); 396 } 397 } 398 399 static char * 400 authmethods_get(void) 401 { 402 Buffer b; 403 char *list; 404 int i; 405 406 buffer_init(&b); 407 for (i = 0; authmethods[i] != NULL; i++) { 408 if (strcmp(authmethods[i]->name, "none") == 0) 409 continue; 410 if (authmethods[i]->enabled != NULL && 411 *(authmethods[i]->enabled) != 0) { 412 if (buffer_len(&b) > 0) 413 buffer_append(&b, ",", 1); 414 buffer_append(&b, authmethods[i]->name, 415 strlen(authmethods[i]->name)); 416 } 417 } 418 buffer_append(&b, "\0", 1); 419 list = xstrdup(buffer_ptr(&b)); 420 buffer_free(&b); 421 return list; 422 } 423 424 static Authmethod * 425 authmethod_lookup(const char *name) 426 { 427 int i; 428 429 if (name != NULL) 430 for (i = 0; authmethods[i] != NULL; i++) 431 if (authmethods[i]->enabled != NULL && 432 *(authmethods[i]->enabled) != 0 && 433 strcmp(name, authmethods[i]->name) == 0) 434 return authmethods[i]; 435 debug2("Unrecognized authentication method name: %s", 436 name ? name : "NULL"); 437 return NULL; 438 } 439 440