1 /* $OpenBSD: auth2.c,v 1.120 2008/11/04 08:22:12 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 "xmalloc.h" 39 #include "canohost.h" 40 #include "atomicio.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 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 Authmethod *authmethods[] = { 80 &method_none, 81 &method_pubkey, 82 #ifdef GSSAPI 83 &method_gssapi, 84 #endif 85 #ifdef JPAKE 86 &method_jpake, 87 #endif 88 &method_passwd, 89 &method_kbdint, 90 &method_hostbased, 91 NULL 92 }; 93 94 /* protocol */ 95 96 static void input_service_request(int, u_int32_t, void *); 97 static void input_userauth_request(int, u_int32_t, void *); 98 99 /* helper */ 100 static Authmethod *authmethod_lookup(const char *); 101 static char *authmethods_get(void); 102 103 char * 104 auth2_read_banner(void) 105 { 106 struct stat st; 107 char *banner = NULL; 108 size_t len, n; 109 int fd; 110 111 if ((fd = open(options.banner, O_RDONLY)) == -1) 112 return (NULL); 113 if (fstat(fd, &st) == -1) { 114 close(fd); 115 return (NULL); 116 } 117 if (st.st_size > 1*1024*1024) { 118 close(fd); 119 return (NULL); 120 } 121 122 len = (size_t)st.st_size; /* truncate */ 123 banner = xmalloc(len + 1); 124 n = atomicio(read, fd, banner, len); 125 close(fd); 126 127 if (n != len) { 128 xfree(banner); 129 return (NULL); 130 } 131 banner[n] = '\0'; 132 133 return (banner); 134 } 135 136 void 137 userauth_send_banner(const char *msg) 138 { 139 if (datafellows & SSH_BUG_BANNER) 140 return; 141 142 packet_start(SSH2_MSG_USERAUTH_BANNER); 143 packet_put_cstring(msg); 144 packet_put_cstring(""); /* language, unused */ 145 packet_send(); 146 debug("%s: sent", __func__); 147 } 148 149 static void 150 userauth_banner(void) 151 { 152 char *banner = NULL; 153 154 if (options.banner == NULL || 155 strcasecmp(options.banner, "none") == 0 || 156 (datafellows & SSH_BUG_BANNER) != 0) 157 return; 158 159 if ((banner = PRIVSEP(auth2_read_banner())) == NULL) 160 goto done; 161 userauth_send_banner(banner); 162 163 done: 164 if (banner) 165 xfree(banner); 166 } 167 168 /* 169 * loop until authctxt->success == TRUE 170 */ 171 void 172 do_authentication2(Authctxt *authctxt) 173 { 174 dispatch_init(&dispatch_protocol_error); 175 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); 176 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); 177 } 178 179 /*ARGSUSED*/ 180 static void 181 input_service_request(int type, u_int32_t seq, void *ctxt) 182 { 183 Authctxt *authctxt = ctxt; 184 u_int len; 185 int acceptit = 0; 186 char *service = packet_get_string(&len); 187 packet_check_eom(); 188 189 if (authctxt == NULL) 190 fatal("input_service_request: no authctxt"); 191 192 if (strcmp(service, "ssh-userauth") == 0) { 193 if (!authctxt->success) { 194 acceptit = 1; 195 /* now we can handle user-auth requests */ 196 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); 197 } 198 } 199 /* XXX all other service requests are denied */ 200 201 if (acceptit) { 202 packet_start(SSH2_MSG_SERVICE_ACCEPT); 203 packet_put_cstring(service); 204 packet_send(); 205 packet_write_wait(); 206 } else { 207 debug("bad service request %s", service); 208 packet_disconnect("bad service request %s", service); 209 } 210 xfree(service); 211 } 212 213 /*ARGSUSED*/ 214 static void 215 input_userauth_request(int type, u_int32_t seq, void *ctxt) 216 { 217 Authctxt *authctxt = ctxt; 218 Authmethod *m = NULL; 219 char *user, *service, *method, *style = NULL; 220 int authenticated = 0; 221 #ifdef HAVE_LOGIN_CAP 222 login_cap_t *lc; 223 const char *from_host, *from_ip; 224 225 from_host = get_canonical_hostname(options.use_dns); 226 from_ip = get_remote_ipaddr(); 227 #endif 228 229 if (authctxt == NULL) 230 fatal("input_userauth_request: no authctxt"); 231 232 user = packet_get_string(NULL); 233 service = packet_get_string(NULL); 234 method = packet_get_string(NULL); 235 debug("userauth-request for user %s service %s method %s", user, service, method); 236 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); 237 238 if ((style = strchr(user, ':')) != NULL) 239 *style++ = 0; 240 241 if (authctxt->attempt++ == 0) { 242 /* setup auth context */ 243 authctxt->pw = PRIVSEP(getpwnamallow(user)); 244 authctxt->user = xstrdup(user); 245 if (authctxt->pw && strcmp(service, "ssh-connection")==0) { 246 authctxt->valid = 1; 247 debug2("input_userauth_request: setting up authctxt for %s", user); 248 } else { 249 logit("input_userauth_request: invalid user %s", user); 250 authctxt->pw = fakepw(); 251 #ifdef SSH_AUDIT_EVENTS 252 PRIVSEP(audit_event(SSH_INVALID_USER)); 253 #endif 254 } 255 #ifdef USE_PAM 256 if (options.use_pam) 257 PRIVSEP(start_pam(authctxt)); 258 #endif 259 setproctitle("%s%s", authctxt->valid ? user : "unknown", 260 use_privsep ? " [net]" : ""); 261 authctxt->service = xstrdup(service); 262 authctxt->style = style ? xstrdup(style) : NULL; 263 if (use_privsep) 264 mm_inform_authserv(service, style); 265 userauth_banner(); 266 } else if (strcmp(user, authctxt->user) != 0 || 267 strcmp(service, authctxt->service) != 0) { 268 packet_disconnect("Change of username or service not allowed: " 269 "(%s,%s) -> (%s,%s)", 270 authctxt->user, authctxt->service, user, service); 271 } 272 273 #ifdef HAVE_LOGIN_CAP 274 if (authctxt->pw != NULL) { 275 lc = login_getpwclass(authctxt->pw); 276 if (lc == NULL) 277 lc = login_getclassbyname(NULL, authctxt->pw); 278 if (!auth_hostok(lc, from_host, from_ip)) { 279 logit("Denied connection for %.200s from %.200s [%.200s].", 280 authctxt->pw->pw_name, from_host, from_ip); 281 packet_disconnect("Sorry, you are not allowed to connect."); 282 } 283 if (!auth_timeok(lc, time(NULL))) { 284 logit("LOGIN %.200s REFUSED (TIME) FROM %.200s", 285 authctxt->pw->pw_name, from_host); 286 packet_disconnect("Logins not available right now."); 287 } 288 login_close(lc); 289 lc = NULL; 290 } 291 #endif /* HAVE_LOGIN_CAP */ 292 293 /* reset state */ 294 auth2_challenge_stop(authctxt); 295 #ifdef JPAKE 296 auth2_jpake_stop(authctxt); 297 #endif 298 299 #ifdef GSSAPI 300 /* XXX move to auth2_gssapi_stop() */ 301 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 302 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 303 #endif 304 305 authctxt->postponed = 0; 306 307 /* try to authenticate user */ 308 m = authmethod_lookup(method); 309 if (m != NULL && authctxt->failures < options.max_authtries) { 310 debug2("input_userauth_request: try method %s", method); 311 authenticated = m->userauth(authctxt); 312 } 313 userauth_finish(authctxt, authenticated, method); 314 315 xfree(service); 316 xfree(user); 317 xfree(method); 318 } 319 320 void 321 userauth_finish(Authctxt *authctxt, int authenticated, char *method) 322 { 323 char *methods; 324 325 if (!authctxt->valid && authenticated) 326 fatal("INTERNAL ERROR: authenticated invalid user %s", 327 authctxt->user); 328 329 /* Special handling for root */ 330 if (authenticated && authctxt->pw->pw_uid == 0 && 331 !auth_root_allowed(method)) { 332 authenticated = 0; 333 #ifdef SSH_AUDIT_EVENTS 334 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); 335 #endif 336 } 337 338 #ifdef USE_PAM 339 if (options.use_pam && authenticated) { 340 if (!PRIVSEP(do_pam_account())) { 341 /* if PAM returned a message, send it to the user */ 342 if (buffer_len(&loginmsg) > 0) { 343 buffer_append(&loginmsg, "\0", 1); 344 userauth_send_banner(buffer_ptr(&loginmsg)); 345 packet_write_wait(); 346 } 347 fatal("Access denied for user %s by PAM account " 348 "configuration", authctxt->user); 349 } 350 } 351 #endif 352 353 #ifdef _UNICOS 354 if (authenticated && cray_access_denied(authctxt->user)) { 355 authenticated = 0; 356 fatal("Access denied for user %s.",authctxt->user); 357 } 358 #endif /* _UNICOS */ 359 360 /* Log before sending the reply */ 361 auth_log(authctxt, authenticated, method, " ssh2"); 362 363 if (authctxt->postponed) 364 return; 365 366 /* XXX todo: check if multiple auth methods are needed */ 367 if (authenticated == 1) { 368 /* turn off userauth */ 369 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); 370 packet_start(SSH2_MSG_USERAUTH_SUCCESS); 371 packet_send(); 372 packet_write_wait(); 373 /* now we can break out */ 374 authctxt->success = 1; 375 } else { 376 377 /* Allow initial try of "none" auth without failure penalty */ 378 if (authctxt->attempt > 1 || strcmp(method, "none") != 0) 379 authctxt->failures++; 380 if (authctxt->failures >= options.max_authtries) { 381 #ifdef SSH_AUDIT_EVENTS 382 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES)); 383 #endif 384 packet_disconnect(AUTH_FAIL_MSG, authctxt->user); 385 } 386 methods = authmethods_get(); 387 packet_start(SSH2_MSG_USERAUTH_FAILURE); 388 packet_put_cstring(methods); 389 packet_put_char(0); /* XXX partial success, unused */ 390 packet_send(); 391 packet_write_wait(); 392 xfree(methods); 393 } 394 } 395 396 static char * 397 authmethods_get(void) 398 { 399 Buffer b; 400 char *list; 401 int i; 402 403 buffer_init(&b); 404 for (i = 0; authmethods[i] != NULL; i++) { 405 if (strcmp(authmethods[i]->name, "none") == 0) 406 continue; 407 if (authmethods[i]->enabled != NULL && 408 *(authmethods[i]->enabled) != 0) { 409 if (buffer_len(&b) > 0) 410 buffer_append(&b, ",", 1); 411 buffer_append(&b, authmethods[i]->name, 412 strlen(authmethods[i]->name)); 413 } 414 } 415 buffer_append(&b, "\0", 1); 416 list = xstrdup(buffer_ptr(&b)); 417 buffer_free(&b); 418 return list; 419 } 420 421 static Authmethod * 422 authmethod_lookup(const char *name) 423 { 424 int i; 425 426 if (name != NULL) 427 for (i = 0; authmethods[i] != NULL; i++) 428 if (authmethods[i]->enabled != NULL && 429 *(authmethods[i]->enabled) != 0 && 430 strcmp(name, authmethods[i]->name) == 0) 431 return authmethods[i]; 432 debug2("Unrecognized authentication method name: %s", 433 name ? name : "NULL"); 434 return NULL; 435 } 436 437