1 /* 2 * Copyright (c) 2000 Markus Friedl. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 23 */ 24 25 #include "includes.h" 26 RCSID("$OpenBSD: auth2.c,v 1.102 2003/08/26 09:58:43 markus Exp $"); 27 RCSID("$FreeBSD$"); 28 29 #include "canohost.h" 30 #include "ssh2.h" 31 #include "xmalloc.h" 32 #include "packet.h" 33 #include "log.h" 34 #include "servconf.h" 35 #include "compat.h" 36 #include "auth.h" 37 #include "dispatch.h" 38 #include "pathnames.h" 39 #include "monitor_wrap.h" 40 41 #ifdef GSSAPI 42 #include "ssh-gss.h" 43 #endif 44 45 /* import */ 46 extern ServerOptions options; 47 extern u_char *session_id2; 48 extern u_int session_id2_len; 49 50 Authctxt *x_authctxt = NULL; 51 52 /* methods */ 53 54 extern Authmethod method_none; 55 extern Authmethod method_pubkey; 56 extern Authmethod method_passwd; 57 extern Authmethod method_kbdint; 58 extern Authmethod method_hostbased; 59 #ifdef GSSAPI 60 extern Authmethod method_gssapi; 61 #endif 62 63 Authmethod *authmethods[] = { 64 &method_none, 65 &method_pubkey, 66 #ifdef GSSAPI 67 &method_gssapi, 68 #endif 69 &method_passwd, 70 &method_kbdint, 71 &method_hostbased, 72 NULL 73 }; 74 75 /* protocol */ 76 77 static void input_service_request(int, u_int32_t, void *); 78 static void input_userauth_request(int, u_int32_t, void *); 79 80 /* helper */ 81 static Authmethod *authmethod_lookup(const char *); 82 static char *authmethods_get(void); 83 int user_key_allowed(struct passwd *, Key *); 84 int hostbased_key_allowed(struct passwd *, const char *, char *, Key *); 85 86 /* 87 * loop until authctxt->success == TRUE 88 */ 89 90 Authctxt * 91 do_authentication2(void) 92 { 93 Authctxt *authctxt = authctxt_new(); 94 95 x_authctxt = authctxt; /*XXX*/ 96 97 /* challenge-response is implemented via keyboard interactive */ 98 if (options.challenge_response_authentication) 99 options.kbd_interactive_authentication = 1; 100 101 dispatch_init(&dispatch_protocol_error); 102 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); 103 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); 104 105 return (authctxt); 106 } 107 108 static void 109 input_service_request(int type, u_int32_t seq, void *ctxt) 110 { 111 Authctxt *authctxt = ctxt; 112 u_int len; 113 int acceptit = 0; 114 char *service = packet_get_string(&len); 115 packet_check_eom(); 116 117 if (authctxt == NULL) 118 fatal("input_service_request: no authctxt"); 119 120 if (strcmp(service, "ssh-userauth") == 0) { 121 if (!authctxt->success) { 122 acceptit = 1; 123 /* now we can handle user-auth requests */ 124 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); 125 } 126 } 127 /* XXX all other service requests are denied */ 128 129 if (acceptit) { 130 packet_start(SSH2_MSG_SERVICE_ACCEPT); 131 packet_put_cstring(service); 132 packet_send(); 133 packet_write_wait(); 134 } else { 135 debug("bad service request %s", service); 136 packet_disconnect("bad service request %s", service); 137 } 138 xfree(service); 139 } 140 141 static void 142 input_userauth_request(int type, u_int32_t seq, void *ctxt) 143 { 144 Authctxt *authctxt = ctxt; 145 Authmethod *m = NULL; 146 char *user, *service, *method, *style = NULL; 147 int authenticated = 0; 148 #ifdef HAVE_LOGIN_CAP 149 login_cap_t *lc; 150 const char *from_host, *from_ip; 151 152 from_host = get_canonical_hostname(options.use_dns); 153 from_ip = get_remote_ipaddr(); 154 #endif 155 156 if (authctxt == NULL) 157 fatal("input_userauth_request: no authctxt"); 158 159 user = packet_get_string(NULL); 160 service = packet_get_string(NULL); 161 method = packet_get_string(NULL); 162 debug("userauth-request for user %s service %s method %s", user, service, method); 163 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); 164 165 if ((style = strchr(user, ':')) != NULL) 166 *style++ = 0; 167 168 if (authctxt->attempt++ == 0) { 169 /* setup auth context */ 170 authctxt->pw = PRIVSEP(getpwnamallow(user)); 171 if (authctxt->pw && strcmp(service, "ssh-connection")==0) { 172 authctxt->valid = 1; 173 debug2("input_userauth_request: setting up authctxt for %s", user); 174 #ifdef USE_PAM 175 if (options.use_pam) 176 PRIVSEP(start_pam(authctxt->pw->pw_name)); 177 #endif 178 } else { 179 logit("input_userauth_request: illegal user %s", user); 180 authctxt->pw = fakepw(); 181 #ifdef USE_PAM 182 if (options.use_pam) 183 PRIVSEP(start_pam(user)); 184 #endif 185 } 186 setproctitle("%s%s", authctxt->pw ? user : "unknown", 187 use_privsep ? " [net]" : ""); 188 authctxt->user = xstrdup(user); 189 authctxt->service = xstrdup(service); 190 authctxt->style = style ? xstrdup(style) : NULL; 191 if (use_privsep) 192 mm_inform_authserv(service, style); 193 } else if (strcmp(user, authctxt->user) != 0 || 194 strcmp(service, authctxt->service) != 0) { 195 packet_disconnect("Change of username or service not allowed: " 196 "(%s,%s) -> (%s,%s)", 197 authctxt->user, authctxt->service, user, service); 198 } 199 200 #ifdef HAVE_LOGIN_CAP 201 if (authctxt->pw != NULL) { 202 lc = login_getpwclass(authctxt->pw); 203 if (lc == NULL) 204 lc = login_getclassbyname(NULL, authctxt->pw); 205 if (!auth_hostok(lc, from_host, from_ip)) { 206 logit("Denied connection for %.200s from %.200s [%.200s].", 207 authctxt->pw->pw_name, from_host, from_ip); 208 packet_disconnect("Sorry, you are not allowed to connect."); 209 } 210 if (!auth_timeok(lc, time(NULL))) { 211 logit("LOGIN %.200s REFUSED (TIME) FROM %.200s", 212 authctxt->pw->pw_name, from_host); 213 packet_disconnect("Logins not available right now."); 214 } 215 login_close(lc); 216 lc = NULL; 217 } 218 #endif /* HAVE_LOGIN_CAP */ 219 220 /* reset state */ 221 auth2_challenge_stop(authctxt); 222 223 #ifdef GSSAPI 224 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 225 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 226 #endif 227 228 authctxt->postponed = 0; 229 230 /* try to authenticate user */ 231 m = authmethod_lookup(method); 232 if (m != NULL) { 233 debug2("input_userauth_request: try method %s", method); 234 authenticated = m->userauth(authctxt); 235 } 236 userauth_finish(authctxt, authenticated, method); 237 238 xfree(service); 239 xfree(user); 240 xfree(method); 241 } 242 243 void 244 userauth_finish(Authctxt *authctxt, int authenticated, char *method) 245 { 246 char *methods; 247 248 if (!authctxt->valid && authenticated) 249 fatal("INTERNAL ERROR: authenticated invalid user %s", 250 authctxt->user); 251 252 /* Special handling for root */ 253 if (authenticated && authctxt->pw->pw_uid == 0 && 254 !auth_root_allowed(method)) 255 authenticated = 0; 256 257 #ifdef USE_PAM 258 if (options.use_pam && authenticated && !PRIVSEP(do_pam_account())) 259 authenticated = 0; 260 #endif 261 262 #ifdef _UNICOS 263 if (authenticated && cray_access_denied(authctxt->user)) { 264 authenticated = 0; 265 fatal("Access denied for user %s.",authctxt->user); 266 } 267 #endif /* _UNICOS */ 268 269 /* Log before sending the reply */ 270 auth_log(authctxt, authenticated, method, " ssh2"); 271 272 if (authctxt->postponed) 273 return; 274 275 /* XXX todo: check if multiple auth methods are needed */ 276 if (authenticated == 1) { 277 /* turn off userauth */ 278 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); 279 packet_start(SSH2_MSG_USERAUTH_SUCCESS); 280 packet_send(); 281 packet_write_wait(); 282 /* now we can break out */ 283 authctxt->success = 1; 284 } else { 285 if (authctxt->failures++ > AUTH_FAIL_MAX) 286 packet_disconnect(AUTH_FAIL_MSG, authctxt->user); 287 methods = authmethods_get(); 288 packet_start(SSH2_MSG_USERAUTH_FAILURE); 289 packet_put_cstring(methods); 290 packet_put_char(0); /* XXX partial success, unused */ 291 packet_send(); 292 packet_write_wait(); 293 xfree(methods); 294 } 295 } 296 297 /* get current user */ 298 299 struct passwd* 300 auth_get_user(void) 301 { 302 return (x_authctxt != NULL && x_authctxt->valid) ? x_authctxt->pw : NULL; 303 } 304 305 #define DELIM "," 306 307 static char * 308 authmethods_get(void) 309 { 310 Buffer b; 311 char *list; 312 int i; 313 314 buffer_init(&b); 315 for (i = 0; authmethods[i] != NULL; i++) { 316 if (strcmp(authmethods[i]->name, "none") == 0) 317 continue; 318 if (authmethods[i]->enabled != NULL && 319 *(authmethods[i]->enabled) != 0) { 320 if (buffer_len(&b) > 0) 321 buffer_append(&b, ",", 1); 322 buffer_append(&b, authmethods[i]->name, 323 strlen(authmethods[i]->name)); 324 } 325 } 326 buffer_append(&b, "\0", 1); 327 list = xstrdup(buffer_ptr(&b)); 328 buffer_free(&b); 329 return list; 330 } 331 332 static Authmethod * 333 authmethod_lookup(const char *name) 334 { 335 int i; 336 337 if (name != NULL) 338 for (i = 0; authmethods[i] != NULL; i++) 339 if (authmethods[i]->enabled != NULL && 340 *(authmethods[i]->enabled) != 0 && 341 strcmp(name, authmethods[i]->name) == 0) 342 return authmethods[i]; 343 debug2("Unrecognized authentication method name: %s", 344 name ? name : "NULL"); 345 return NULL; 346 } 347