1 /* $OpenBSD: auth2.c,v 1.122 2010/08/31 09:58:37 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 28 #include <sys/types.h> 29 #include <sys/stat.h> 30 #include <sys/uio.h> 31 32 #include <fcntl.h> 33 #include <pwd.h> 34 #include <stdarg.h> 35 #include <string.h> 36 #include <unistd.h> 37 38 #include "atomicio.h" 39 #include "xmalloc.h" 40 #include "ssh2.h" 41 #include "packet.h" 42 #include "log.h" 43 #include "buffer.h" 44 #include "servconf.h" 45 #include "compat.h" 46 #include "key.h" 47 #include "hostfile.h" 48 #include "auth.h" 49 #include "dispatch.h" 50 #include "pathnames.h" 51 #include "buffer.h" 52 #include "canohost.h" 53 54 #ifdef GSSAPI 55 #include "ssh-gss.h" 56 #endif 57 #include "monitor_wrap.h" 58 59 /* import */ 60 extern ServerOptions options; 61 extern u_char *session_id2; 62 extern u_int session_id2_len; 63 extern Buffer loginmsg; 64 65 /* methods */ 66 67 extern Authmethod method_none; 68 extern Authmethod method_pubkey; 69 extern Authmethod method_passwd; 70 extern Authmethod method_kbdint; 71 extern Authmethod method_hostbased; 72 #ifdef GSSAPI 73 extern Authmethod method_gssapi; 74 #endif 75 #ifdef JPAKE 76 extern Authmethod method_jpake; 77 #endif 78 79 static int log_flag = 0; 80 81 82 Authmethod *authmethods[] = { 83 &method_none, 84 &method_pubkey, 85 #ifdef GSSAPI 86 &method_gssapi, 87 #endif 88 #ifdef JPAKE 89 &method_jpake, 90 #endif 91 &method_passwd, 92 &method_kbdint, 93 &method_hostbased, 94 NULL 95 }; 96 97 /* protocol */ 98 99 static void input_service_request(int, u_int32_t, void *); 100 static void input_userauth_request(int, u_int32_t, void *); 101 102 /* helper */ 103 static Authmethod *authmethod_lookup(const char *); 104 static char *authmethods_get(void); 105 106 char * 107 auth2_read_banner(void) 108 { 109 struct stat st; 110 char *banner = NULL; 111 size_t len, n; 112 int fd; 113 114 if ((fd = open(options.banner, O_RDONLY)) == -1) 115 return (NULL); 116 if (fstat(fd, &st) == -1) { 117 close(fd); 118 return (NULL); 119 } 120 if (st.st_size > 1*1024*1024) { 121 close(fd); 122 return (NULL); 123 } 124 125 len = (size_t)st.st_size; /* truncate */ 126 banner = xmalloc(len + 1); 127 n = atomicio(read, fd, banner, len); 128 close(fd); 129 130 if (n != len) { 131 xfree(banner); 132 return (NULL); 133 } 134 banner[n] = '\0'; 135 136 return (banner); 137 } 138 139 void 140 userauth_send_banner(const char *msg) 141 { 142 if (datafellows & SSH_BUG_BANNER) 143 return; 144 145 packet_start(SSH2_MSG_USERAUTH_BANNER); 146 packet_put_cstring(msg); 147 packet_put_cstring(""); /* language, unused */ 148 packet_send(); 149 debug("%s: sent", __func__); 150 } 151 152 static void 153 userauth_banner(void) 154 { 155 char *banner = NULL; 156 157 if (options.banner == NULL || 158 strcasecmp(options.banner, "none") == 0 || 159 (datafellows & SSH_BUG_BANNER) != 0) 160 return; 161 162 if ((banner = PRIVSEP(auth2_read_banner())) == NULL) 163 goto done; 164 userauth_send_banner(banner); 165 166 done: 167 if (banner) 168 xfree(banner); 169 } 170 171 /* 172 * loop until authctxt->success == TRUE 173 */ 174 void 175 do_authentication2(Authctxt *authctxt) 176 { 177 dispatch_init(&dispatch_protocol_error); 178 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); 179 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); 180 } 181 182 /*ARGSUSED*/ 183 static void 184 input_service_request(int type, u_int32_t seq, void *ctxt) 185 { 186 Authctxt *authctxt = ctxt; 187 u_int len; 188 int acceptit = 0; 189 char *service = packet_get_cstring(&len); 190 packet_check_eom(); 191 192 if (authctxt == NULL) 193 fatal("input_service_request: no authctxt"); 194 195 if (strcmp(service, "ssh-userauth") == 0) { 196 if (!authctxt->success) { 197 acceptit = 1; 198 /* now we can handle user-auth requests */ 199 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); 200 } 201 } 202 /* XXX all other service requests are denied */ 203 204 if (acceptit) { 205 packet_start(SSH2_MSG_SERVICE_ACCEPT); 206 packet_put_cstring(service); 207 packet_send(); 208 packet_write_wait(); 209 } else { 210 debug("bad service request %s", service); 211 packet_disconnect("bad service request %s", service); 212 } 213 xfree(service); 214 } 215 216 /*ARGSUSED*/ 217 static void 218 input_userauth_request(int type, u_int32_t seq, void *ctxt) 219 { 220 Authctxt *authctxt = ctxt; 221 Authmethod *m = NULL; 222 char *user, *service, *method, *style = NULL; 223 int authenticated = 0; 224 #ifdef HAVE_LOGIN_CAP 225 login_cap_t *lc; 226 const char *from_host, *from_ip; 227 228 from_host = get_canonical_hostname(options.use_dns); 229 from_ip = get_remote_ipaddr(); 230 #endif 231 232 if (authctxt == NULL) 233 fatal("input_userauth_request: no authctxt"); 234 235 user = packet_get_cstring(NULL); 236 service = packet_get_cstring(NULL); 237 method = packet_get_cstring(NULL); 238 debug("userauth-request for user %s service %s method %s", user, service, method); 239 if (!log_flag) { 240 logit("SSH: Server;Ltype: Authname;Remote: %s-%d;Name: %s", 241 get_remote_ipaddr(), get_remote_port(), user); 242 log_flag = 1; 243 } 244 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); 245 246 if ((style = strchr(user, ':')) != NULL) 247 *style++ = 0; 248 249 if (authctxt->attempt++ == 0) { 250 /* setup auth context */ 251 authctxt->pw = PRIVSEP(getpwnamallow(user)); 252 authctxt->user = xstrdup(user); 253 if (authctxt->pw && strcmp(service, "ssh-connection")==0) { 254 authctxt->valid = 1; 255 debug2("input_userauth_request: setting up authctxt for %s", user); 256 } else { 257 logit("input_userauth_request: invalid user %s", user); 258 authctxt->pw = fakepw(); 259 #ifdef SSH_AUDIT_EVENTS 260 PRIVSEP(audit_event(SSH_INVALID_USER)); 261 #endif 262 } 263 #ifdef USE_PAM 264 if (options.use_pam) 265 PRIVSEP(start_pam(authctxt)); 266 #endif 267 setproctitle("%s%s", authctxt->valid ? user : "unknown", 268 use_privsep ? " [net]" : ""); 269 authctxt->service = xstrdup(service); 270 authctxt->style = style ? xstrdup(style) : NULL; 271 if (use_privsep) 272 mm_inform_authserv(service, style); 273 userauth_banner(); 274 } else if (strcmp(user, authctxt->user) != 0 || 275 strcmp(service, authctxt->service) != 0) { 276 packet_disconnect("Change of username or service not allowed: " 277 "(%s,%s) -> (%s,%s)", 278 authctxt->user, authctxt->service, user, service); 279 } 280 281 #ifdef HAVE_LOGIN_CAP 282 if (authctxt->pw != NULL) { 283 lc = login_getpwclass(authctxt->pw); 284 if (lc == NULL) 285 lc = login_getclassbyname(NULL, authctxt->pw); 286 if (!auth_hostok(lc, from_host, from_ip)) { 287 logit("Denied connection for %.200s from %.200s [%.200s].", 288 authctxt->pw->pw_name, from_host, from_ip); 289 packet_disconnect("Sorry, you are not allowed to connect."); 290 } 291 if (!auth_timeok(lc, time(NULL))) { 292 logit("LOGIN %.200s REFUSED (TIME) FROM %.200s", 293 authctxt->pw->pw_name, from_host); 294 packet_disconnect("Logins not available right now."); 295 } 296 login_close(lc); 297 lc = NULL; 298 } 299 #endif /* HAVE_LOGIN_CAP */ 300 301 /* reset state */ 302 auth2_challenge_stop(authctxt); 303 #ifdef JPAKE 304 auth2_jpake_stop(authctxt); 305 #endif 306 307 #ifdef GSSAPI 308 /* XXX move to auth2_gssapi_stop() */ 309 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 310 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 311 #endif 312 313 authctxt->postponed = 0; 314 315 /* try to authenticate user */ 316 m = authmethod_lookup(method); 317 if (m != NULL && authctxt->failures < options.max_authtries) { 318 debug2("input_userauth_request: try method %s", method); 319 authenticated = m->userauth(authctxt); 320 } 321 userauth_finish(authctxt, authenticated, method); 322 323 xfree(service); 324 xfree(user); 325 xfree(method); 326 } 327 328 void 329 userauth_finish(Authctxt *authctxt, int authenticated, char *method) 330 { 331 char *methods; 332 333 if (!authctxt->valid && authenticated) 334 fatal("INTERNAL ERROR: authenticated invalid user %s", 335 authctxt->user); 336 337 /* Special handling for root */ 338 if (authenticated && authctxt->pw->pw_uid == 0 && 339 !auth_root_allowed(method)) { 340 authenticated = 0; 341 #ifdef SSH_AUDIT_EVENTS 342 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); 343 #endif 344 } 345 346 #ifdef USE_PAM 347 if (options.use_pam && authenticated) { 348 if (!PRIVSEP(do_pam_account())) { 349 /* if PAM returned a message, send it to the user */ 350 if (buffer_len(&loginmsg) > 0) { 351 buffer_append(&loginmsg, "\0", 1); 352 userauth_send_banner(buffer_ptr(&loginmsg)); 353 packet_write_wait(); 354 } 355 fatal("Access denied for user %s by PAM account " 356 "configuration", authctxt->user); 357 } 358 } 359 #endif 360 361 #ifdef _UNICOS 362 if (authenticated && cray_access_denied(authctxt->user)) { 363 authenticated = 0; 364 fatal("Access denied for user %s.",authctxt->user); 365 } 366 #endif /* _UNICOS */ 367 368 /* Log before sending the reply */ 369 auth_log(authctxt, authenticated, method, " ssh2"); 370 371 if (authctxt->postponed) 372 return; 373 374 /* XXX todo: check if multiple auth methods are needed */ 375 if (authenticated == 1) { 376 /* turn off userauth */ 377 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); 378 packet_start(SSH2_MSG_USERAUTH_SUCCESS); 379 packet_send(); 380 packet_write_wait(); 381 /* now we can break out */ 382 authctxt->success = 1; 383 } else { 384 385 /* Allow initial try of "none" auth without failure penalty */ 386 if (authctxt->attempt > 1 || strcmp(method, "none") != 0) 387 authctxt->failures++; 388 if (authctxt->failures >= options.max_authtries) { 389 #ifdef SSH_AUDIT_EVENTS 390 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES)); 391 #endif 392 packet_disconnect(AUTH_FAIL_MSG, authctxt->user); 393 } 394 methods = authmethods_get(); 395 packet_start(SSH2_MSG_USERAUTH_FAILURE); 396 packet_put_cstring(methods); 397 packet_put_char(0); /* XXX partial success, unused */ 398 packet_send(); 399 packet_write_wait(); 400 xfree(methods); 401 } 402 } 403 404 static char * 405 authmethods_get(void) 406 { 407 Buffer b; 408 char *list; 409 int i; 410 411 buffer_init(&b); 412 for (i = 0; authmethods[i] != NULL; i++) { 413 if (strcmp(authmethods[i]->name, "none") == 0) 414 continue; 415 if (authmethods[i]->enabled != NULL && 416 *(authmethods[i]->enabled) != 0) { 417 if (buffer_len(&b) > 0) 418 buffer_append(&b, ",", 1); 419 buffer_append(&b, authmethods[i]->name, 420 strlen(authmethods[i]->name)); 421 } 422 } 423 buffer_append(&b, "\0", 1); 424 list = xstrdup(buffer_ptr(&b)); 425 buffer_free(&b); 426 return list; 427 } 428 429 static Authmethod * 430 authmethod_lookup(const char *name) 431 { 432 int i; 433 434 if (name != NULL) 435 for (i = 0; authmethods[i] != NULL; i++) 436 if (authmethods[i]->enabled != NULL && 437 *(authmethods[i]->enabled) != 0 && 438 strcmp(name, authmethods[i]->name) == 0) 439 return authmethods[i]; 440 debug2("Unrecognized authentication method name: %s", 441 name ? name : "NULL"); 442 return NULL; 443 } 444 445