1 /* $OpenBSD: auth2.c,v 1.119 2008/07/04 23:30:16 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 27 #include <sys/types.h> 28 #include <sys/stat.h> 29 #include <sys/uio.h> 30 31 #include <fcntl.h> 32 #include <pwd.h> 33 #include <string.h> 34 #include <stdarg.h> 35 #include <unistd.h> 36 37 #include "atomicio.h" 38 #include "xmalloc.h" 39 #include "ssh2.h" 40 #include "packet.h" 41 #include "log.h" 42 #include "buffer.h" 43 #include "servconf.h" 44 #include "compat.h" 45 #include "key.h" 46 #include "hostfile.h" 47 #include "auth.h" 48 #include "dispatch.h" 49 #include "pathnames.h" 50 #ifdef GSSAPI 51 #include "ssh-gss.h" 52 #endif 53 #include "monitor_wrap.h" 54 55 /* import */ 56 extern ServerOptions options; 57 extern u_char *session_id2; 58 extern u_int session_id2_len; 59 60 /* methods */ 61 62 extern Authmethod method_none; 63 extern Authmethod method_pubkey; 64 extern Authmethod method_passwd; 65 extern Authmethod method_kbdint; 66 extern Authmethod method_hostbased; 67 #ifdef GSSAPI 68 extern Authmethod method_gssapi; 69 #endif 70 71 Authmethod *authmethods[] = { 72 &method_none, 73 &method_pubkey, 74 #ifdef GSSAPI 75 &method_gssapi, 76 #endif 77 &method_passwd, 78 &method_kbdint, 79 &method_hostbased, 80 NULL 81 }; 82 83 /* protocol */ 84 85 static void input_service_request(int, u_int32_t, void *); 86 static void input_userauth_request(int, u_int32_t, void *); 87 88 /* helper */ 89 static Authmethod *authmethod_lookup(const char *); 90 static char *authmethods_get(void); 91 92 char * 93 auth2_read_banner(void) 94 { 95 struct stat st; 96 char *banner = NULL; 97 size_t len, n; 98 int fd; 99 100 if ((fd = open(options.banner, O_RDONLY)) == -1) 101 return (NULL); 102 if (fstat(fd, &st) == -1) { 103 close(fd); 104 return (NULL); 105 } 106 if (st.st_size > 1*1024*1024) { 107 close(fd); 108 return (NULL); 109 } 110 111 len = (size_t)st.st_size; /* truncate */ 112 banner = xmalloc(len + 1); 113 n = atomicio(read, fd, banner, len); 114 close(fd); 115 116 if (n != len) { 117 xfree(banner); 118 return (NULL); 119 } 120 banner[n] = '\0'; 121 122 return (banner); 123 } 124 125 static void 126 userauth_banner(void) 127 { 128 char *banner = NULL; 129 130 if (options.banner == NULL || 131 strcasecmp(options.banner, "none") == 0 || 132 (datafellows & SSH_BUG_BANNER) != 0) 133 return; 134 135 if ((banner = PRIVSEP(auth2_read_banner())) == NULL) 136 goto done; 137 138 packet_start(SSH2_MSG_USERAUTH_BANNER); 139 packet_put_cstring(banner); 140 packet_put_cstring(""); /* language, unused */ 141 packet_send(); 142 debug("userauth_banner: sent"); 143 done: 144 if (banner) 145 xfree(banner); 146 } 147 148 /* 149 * loop until authctxt->success == TRUE 150 */ 151 void 152 do_authentication2(Authctxt *authctxt) 153 { 154 dispatch_init(&dispatch_protocol_error); 155 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); 156 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); 157 } 158 159 /*ARGSUSED*/ 160 static void 161 input_service_request(int type, u_int32_t seq, void *ctxt) 162 { 163 Authctxt *authctxt = ctxt; 164 u_int len; 165 int acceptit = 0; 166 char *service = packet_get_string(&len); 167 packet_check_eom(); 168 169 if (authctxt == NULL) 170 fatal("input_service_request: no authctxt"); 171 172 if (strcmp(service, "ssh-userauth") == 0) { 173 if (!authctxt->success) { 174 acceptit = 1; 175 /* now we can handle user-auth requests */ 176 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); 177 } 178 } 179 /* XXX all other service requests are denied */ 180 181 if (acceptit) { 182 packet_start(SSH2_MSG_SERVICE_ACCEPT); 183 packet_put_cstring(service); 184 packet_send(); 185 packet_write_wait(); 186 } else { 187 debug("bad service request %s", service); 188 packet_disconnect("bad service request %s", service); 189 } 190 xfree(service); 191 } 192 193 /*ARGSUSED*/ 194 static void 195 input_userauth_request(int type, u_int32_t seq, void *ctxt) 196 { 197 Authctxt *authctxt = ctxt; 198 Authmethod *m = NULL; 199 char *user, *service, *method, *style = NULL; 200 int authenticated = 0; 201 202 if (authctxt == NULL) 203 fatal("input_userauth_request: no authctxt"); 204 205 user = packet_get_string(NULL); 206 service = packet_get_string(NULL); 207 method = packet_get_string(NULL); 208 debug("userauth-request for user %s service %s method %s", user, service, method); 209 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); 210 211 if ((style = strchr(user, ':')) != NULL) 212 *style++ = 0; 213 214 if (authctxt->attempt++ == 0) { 215 /* setup auth context */ 216 authctxt->pw = PRIVSEP(getpwnamallow(user)); 217 if (authctxt->pw && strcmp(service, "ssh-connection")==0) { 218 authctxt->valid = 1; 219 debug2("input_userauth_request: setting up authctxt for %s", user); 220 } else { 221 logit("input_userauth_request: invalid user %s", user); 222 authctxt->pw = fakepw(); 223 } 224 setproctitle("%s%s", authctxt->valid ? user : "unknown", 225 use_privsep ? " [net]" : ""); 226 authctxt->user = xstrdup(user); 227 authctxt->service = xstrdup(service); 228 authctxt->style = style ? xstrdup(style) : NULL; 229 if (use_privsep) 230 mm_inform_authserv(service, style); 231 userauth_banner(); 232 } else if (strcmp(user, authctxt->user) != 0 || 233 strcmp(service, authctxt->service) != 0) { 234 packet_disconnect("Change of username or service not allowed: " 235 "(%s,%s) -> (%s,%s)", 236 authctxt->user, authctxt->service, user, service); 237 } 238 /* reset state */ 239 auth2_challenge_stop(authctxt); 240 241 #ifdef GSSAPI 242 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 243 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 244 #endif 245 246 authctxt->postponed = 0; 247 248 /* try to authenticate user */ 249 m = authmethod_lookup(method); 250 if (m != NULL && authctxt->failures < options.max_authtries) { 251 debug2("input_userauth_request: try method %s", method); 252 authenticated = m->userauth(authctxt); 253 } 254 userauth_finish(authctxt, authenticated, method); 255 256 xfree(service); 257 xfree(user); 258 xfree(method); 259 } 260 261 void 262 userauth_finish(Authctxt *authctxt, int authenticated, char *method) 263 { 264 char *methods; 265 266 if (!authctxt->valid && authenticated) 267 fatal("INTERNAL ERROR: authenticated invalid user %s", 268 authctxt->user); 269 270 /* Special handling for root */ 271 if (authenticated && authctxt->pw->pw_uid == 0 && 272 !auth_root_allowed(method)) 273 authenticated = 0; 274 275 /* Log before sending the reply */ 276 auth_log(authctxt, authenticated, method, " ssh2"); 277 278 if (authctxt->postponed) 279 return; 280 281 /* XXX todo: check if multiple auth methods are needed */ 282 if (authenticated == 1) { 283 /* turn off userauth */ 284 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); 285 packet_start(SSH2_MSG_USERAUTH_SUCCESS); 286 packet_send(); 287 packet_write_wait(); 288 /* now we can break out */ 289 authctxt->success = 1; 290 } else { 291 /* Allow initial try of "none" auth without failure penalty */ 292 if (authctxt->attempt > 1 || strcmp(method, "none") != 0) 293 authctxt->failures++; 294 if (authctxt->failures >= options.max_authtries) 295 packet_disconnect(AUTH_FAIL_MSG, authctxt->user); 296 methods = authmethods_get(); 297 packet_start(SSH2_MSG_USERAUTH_FAILURE); 298 packet_put_cstring(methods); 299 packet_put_char(0); /* XXX partial success, unused */ 300 packet_send(); 301 packet_write_wait(); 302 xfree(methods); 303 } 304 } 305 306 static char * 307 authmethods_get(void) 308 { 309 Buffer b; 310 char *list; 311 int i; 312 313 buffer_init(&b); 314 for (i = 0; authmethods[i] != NULL; i++) { 315 if (strcmp(authmethods[i]->name, "none") == 0) 316 continue; 317 if (authmethods[i]->enabled != NULL && 318 *(authmethods[i]->enabled) != 0) { 319 if (buffer_len(&b) > 0) 320 buffer_append(&b, ",", 1); 321 buffer_append(&b, authmethods[i]->name, 322 strlen(authmethods[i]->name)); 323 } 324 } 325 buffer_append(&b, "\0", 1); 326 list = xstrdup(buffer_ptr(&b)); 327 buffer_free(&b); 328 return list; 329 } 330 331 static Authmethod * 332 authmethod_lookup(const char *name) 333 { 334 int i; 335 336 if (name != NULL) 337 for (i = 0; authmethods[i] != NULL; i++) 338 if (authmethods[i]->enabled != NULL && 339 *(authmethods[i]->enabled) != 0 && 340 strcmp(name, authmethods[i]->name) == 0) 341 return authmethods[i]; 342 debug2("Unrecognized authentication method name: %s", 343 name ? name : "NULL"); 344 return NULL; 345 } 346 347