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 1.104 2003/11/04 08:54:09 djm Exp $"); 27 28 #include "ssh2.h" 29 #include "xmalloc.h" 30 #include "packet.h" 31 #include "log.h" 32 #include "servconf.h" 33 #include "compat.h" 34 #include "auth.h" 35 #include "dispatch.h" 36 #include "pathnames.h" 37 #include "monitor_wrap.h" 38 39 #ifdef GSSAPI 40 #include "ssh-gss.h" 41 #endif 42 43 /* import */ 44 extern ServerOptions options; 45 extern u_char *session_id2; 46 extern u_int session_id2_len; 47 48 /* methods */ 49 50 extern Authmethod method_none; 51 extern Authmethod method_pubkey; 52 extern Authmethod method_passwd; 53 extern Authmethod method_kbdint; 54 extern Authmethod method_hostbased; 55 #ifdef GSSAPI 56 extern Authmethod method_gssapi; 57 #endif 58 59 Authmethod *authmethods[] = { 60 &method_none, 61 &method_pubkey, 62 #ifdef GSSAPI 63 &method_gssapi, 64 #endif 65 &method_passwd, 66 &method_kbdint, 67 &method_hostbased, 68 NULL 69 }; 70 71 /* protocol */ 72 73 static void input_service_request(int, u_int32_t, void *); 74 static void input_userauth_request(int, u_int32_t, void *); 75 76 /* helper */ 77 static Authmethod *authmethod_lookup(const char *); 78 static char *authmethods_get(void); 79 int user_key_allowed(struct passwd *, Key *); 80 81 /* 82 * loop until authctxt->success == TRUE 83 */ 84 85 void 86 do_authentication2(Authctxt *authctxt) 87 { 88 /* challenge-response is implemented via keyboard interactive */ 89 if (options.challenge_response_authentication) 90 options.kbd_interactive_authentication = 1; 91 92 dispatch_init(&dispatch_protocol_error); 93 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); 94 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); 95 } 96 97 static void 98 input_service_request(int type, u_int32_t seq, void *ctxt) 99 { 100 Authctxt *authctxt = ctxt; 101 u_int len; 102 int acceptit = 0; 103 char *service = packet_get_string(&len); 104 packet_check_eom(); 105 106 if (authctxt == NULL) 107 fatal("input_service_request: no authctxt"); 108 109 if (strcmp(service, "ssh-userauth") == 0) { 110 if (!authctxt->success) { 111 acceptit = 1; 112 /* now we can handle user-auth requests */ 113 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); 114 } 115 } 116 /* XXX all other service requests are denied */ 117 118 if (acceptit) { 119 packet_start(SSH2_MSG_SERVICE_ACCEPT); 120 packet_put_cstring(service); 121 packet_send(); 122 packet_write_wait(); 123 } else { 124 debug("bad service request %s", service); 125 packet_disconnect("bad service request %s", service); 126 } 127 xfree(service); 128 } 129 130 static void 131 input_userauth_request(int type, u_int32_t seq, void *ctxt) 132 { 133 Authctxt *authctxt = ctxt; 134 Authmethod *m = NULL; 135 char *user, *service, *method, *style = NULL; 136 int authenticated = 0; 137 138 if (authctxt == NULL) 139 fatal("input_userauth_request: no authctxt"); 140 141 user = packet_get_string(NULL); 142 service = packet_get_string(NULL); 143 method = packet_get_string(NULL); 144 debug("userauth-request for user %s service %s method %s", user, service, method); 145 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); 146 147 if ((style = strchr(user, ':')) != NULL) 148 *style++ = 0; 149 150 if (authctxt->attempt++ == 0) { 151 /* setup auth context */ 152 authctxt->pw = PRIVSEP(getpwnamallow(user)); 153 if (authctxt->pw && strcmp(service, "ssh-connection")==0) { 154 authctxt->valid = 1; 155 debug2("input_userauth_request: setting up authctxt for %s", user); 156 } else { 157 logit("input_userauth_request: illegal user %s", user); 158 authctxt->pw = fakepw(); 159 } 160 setproctitle("%s%s", authctxt->pw ? user : "unknown", 161 use_privsep ? " [net]" : ""); 162 authctxt->user = xstrdup(user); 163 authctxt->service = xstrdup(service); 164 authctxt->style = style ? xstrdup(style) : NULL; 165 if (use_privsep) 166 mm_inform_authserv(service, style); 167 } else if (strcmp(user, authctxt->user) != 0 || 168 strcmp(service, authctxt->service) != 0) { 169 packet_disconnect("Change of username or service not allowed: " 170 "(%s,%s) -> (%s,%s)", 171 authctxt->user, authctxt->service, user, service); 172 } 173 /* reset state */ 174 auth2_challenge_stop(authctxt); 175 176 #ifdef GSSAPI 177 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 178 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 179 #endif 180 181 authctxt->postponed = 0; 182 183 /* try to authenticate user */ 184 m = authmethod_lookup(method); 185 if (m != NULL) { 186 debug2("input_userauth_request: try method %s", method); 187 authenticated = m->userauth(authctxt); 188 } 189 userauth_finish(authctxt, authenticated, method); 190 191 xfree(service); 192 xfree(user); 193 xfree(method); 194 } 195 196 void 197 userauth_finish(Authctxt *authctxt, int authenticated, char *method) 198 { 199 char *methods; 200 201 if (!authctxt->valid && authenticated) 202 fatal("INTERNAL ERROR: authenticated invalid user %s", 203 authctxt->user); 204 205 /* Special handling for root */ 206 if (authenticated && authctxt->pw->pw_uid == 0 && 207 !auth_root_allowed(method)) 208 authenticated = 0; 209 210 /* Log before sending the reply */ 211 auth_log(authctxt, authenticated, method, " ssh2"); 212 213 if (authctxt->postponed) 214 return; 215 216 /* XXX todo: check if multiple auth methods are needed */ 217 if (authenticated == 1) { 218 /* turn off userauth */ 219 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); 220 packet_start(SSH2_MSG_USERAUTH_SUCCESS); 221 packet_send(); 222 packet_write_wait(); 223 /* now we can break out */ 224 authctxt->success = 1; 225 } else { 226 if (authctxt->failures++ > AUTH_FAIL_MAX) 227 packet_disconnect(AUTH_FAIL_MSG, authctxt->user); 228 methods = authmethods_get(); 229 packet_start(SSH2_MSG_USERAUTH_FAILURE); 230 packet_put_cstring(methods); 231 packet_put_char(0); /* XXX partial success, unused */ 232 packet_send(); 233 packet_write_wait(); 234 xfree(methods); 235 } 236 } 237 238 #define DELIM "," 239 240 static char * 241 authmethods_get(void) 242 { 243 Buffer b; 244 char *list; 245 int i; 246 247 buffer_init(&b); 248 for (i = 0; authmethods[i] != NULL; i++) { 249 if (strcmp(authmethods[i]->name, "none") == 0) 250 continue; 251 if (authmethods[i]->enabled != NULL && 252 *(authmethods[i]->enabled) != 0) { 253 if (buffer_len(&b) > 0) 254 buffer_append(&b, ",", 1); 255 buffer_append(&b, authmethods[i]->name, 256 strlen(authmethods[i]->name)); 257 } 258 } 259 buffer_append(&b, "\0", 1); 260 list = xstrdup(buffer_ptr(&b)); 261 buffer_free(&b); 262 return list; 263 } 264 265 static Authmethod * 266 authmethod_lookup(const char *name) 267 { 268 int i; 269 270 if (name != NULL) 271 for (i = 0; authmethods[i] != NULL; i++) 272 if (authmethods[i]->enabled != NULL && 273 *(authmethods[i]->enabled) != 0 && 274 strcmp(name, authmethods[i]->name) == 0) 275 return authmethods[i]; 276 debug2("Unrecognized authentication method name: %s", 277 name ? name : "NULL"); 278 return NULL; 279 } 280