1 /* 2 * Copyright 2008 Sun Microsystems, Inc. All rights reserved. 3 * Use is subject to license terms. 4 */ 5 6 #include "includes.h" 7 8 RCSID("$Id: auth2-pam.c,v 1.14 2002/06/28 16:48:12 mouring Exp $"); 9 10 #pragma ident "%Z%%M% %I% %E% SMI" 11 12 #ifdef USE_PAM 13 #include <security/pam_appl.h> 14 15 #include "ssh.h" 16 #include "ssh2.h" 17 #include "auth.h" 18 #include "auth-pam.h" 19 #include "auth-options.h" 20 #include "packet.h" 21 #include "xmalloc.h" 22 #include "dispatch.h" 23 #include "canohost.h" 24 #include "log.h" 25 #include "servconf.h" 26 #include "misc.h" 27 28 #ifdef HAVE_BSM 29 #include "bsmaudit.h" 30 #endif /* HAVE_BSM */ 31 32 extern u_int utmp_len; 33 extern ServerOptions options; 34 35 extern Authmethod method_kbdint; 36 extern Authmethod method_passwd; 37 38 #define SSHD_PAM_KBDINT_SVC "sshd-kbdint" 39 40 static int do_pam_conv_kbd_int(int num_msg, 41 struct pam_message **msg, struct pam_response **resp, 42 void *appdata_ptr); 43 static void input_userauth_info_response_pam(int type, 44 u_int32_t seqnr, 45 void *ctxt); 46 47 static struct pam_conv conv2 = { 48 do_pam_conv_kbd_int, 49 NULL, 50 }; 51 52 static void do_pam_kbdint_cleanup(pam_handle_t *pamh); 53 static void do_pam_kbdint(Authctxt *authctxt); 54 55 void 56 auth2_pam(Authctxt *authctxt) 57 { 58 if (authctxt->user == NULL) 59 fatal("auth2_pam: internal error: no user"); 60 if (authctxt->method == NULL) 61 fatal("auth2_pam: internal error: no method"); 62 63 conv2.appdata_ptr = authctxt; 64 new_start_pam(authctxt, &conv2); 65 66 authctxt->method->method_data = NULL; /* freed in the conv func */ 67 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, 68 &input_userauth_info_response_pam); 69 70 /* 71 * Since password userauth and keyboard-interactive userauth 72 * both use PAM, and since keyboard-interactive is so much 73 * better than password userauth, we should not allow the user 74 * to try password userauth after trying keyboard-interactive. 75 */ 76 if (method_passwd.enabled) 77 *method_passwd.enabled = 0; 78 79 do_pam_kbdint(authctxt); 80 81 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL); 82 } 83 84 static void 85 do_pam_kbdint(Authctxt *authctxt) 86 { 87 int retval, retval2; 88 pam_handle_t *pamh = authctxt->pam->h; 89 const char *where = "authenticating"; 90 char *text = NULL; 91 92 debug2("Calling pam_authenticate()"); 93 retval = pam_authenticate(pamh, 94 options.permit_empty_passwd ? 0 : 95 PAM_DISALLOW_NULL_AUTHTOK); 96 97 if (retval != PAM_SUCCESS) 98 goto cleanup; 99 100 debug2("kbd-int: pam_authenticate() succeeded"); 101 where = "authorizing"; 102 retval = pam_acct_mgmt(pamh, 0); 103 104 if (retval == PAM_NEW_AUTHTOK_REQD) { 105 if (authctxt->valid && authctxt->pw != NULL) { 106 /* send password expiration warning */ 107 message_cat(&text, 108 gettext("Warning: Your password has expired," 109 " please change it now.")); 110 packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST); 111 packet_put_cstring(""); /* name */ 112 packet_put_cstring(text); /* instructions */ 113 packet_put_cstring(""); /* language, unused */ 114 packet_put_int(0); 115 packet_send(); 116 packet_write_wait(); 117 debug("expiration message sent"); 118 if (text) 119 xfree(text); 120 /* 121 * wait for the response so it does not mix 122 * with the upcoming PAM conversation 123 */ 124 packet_read_expect(SSH2_MSG_USERAUTH_INFO_RESPONSE); 125 /* 126 * Can't use temporarily_use_uid() and restore_uid() 127 * here because we need (euid == 0 && ruid == pw_uid) 128 * whereas temporarily_use_uid() arranges for 129 * (suid = 0 && euid == pw_uid && ruid == pw_uid). 130 */ 131 (void) setreuid(authctxt->pw->pw_uid, -1); 132 debug2("kbd-int: changing expired password"); 133 where = "changing authentication tokens (password)"; 134 retval = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK); 135 audit_sshd_chauthtok(retval, authctxt->pw->pw_uid, 136 authctxt->pw->pw_gid); 137 (void) setreuid(0, -1); 138 } else { 139 retval = PAM_PERM_DENIED; 140 } 141 } 142 143 if (retval != PAM_SUCCESS) 144 goto cleanup; 145 146 authctxt->pam->state |= PAM_S_DONE_ACCT_MGMT; 147 148 retval = finish_userauth_do_pam(authctxt); 149 150 if (retval != PAM_SUCCESS) 151 goto cleanup; 152 153 /* 154 * PAM handle stays around so we can call pam_close_session() 155 * on it later. 156 */ 157 authctxt->method->authenticated = 1; 158 debug2("kbd-int: success (pam->state == %x)", authctxt->pam->state); 159 return; 160 161 cleanup: 162 /* 163 * Check for abandonment and cleanup. When kbdint is abandoned 164 * authctxt->pam->h is NULLed and by this point a new handle may 165 * be allocated. 166 */ 167 if (authctxt->pam->h != pamh) { 168 log("Keyboard-interactive (PAM) userauth abandoned " 169 "while %s", where); 170 if ((retval2 = pam_end(pamh, retval)) != PAM_SUCCESS) { 171 log("Cannot close PAM handle after " 172 "kbd-int userauth abandonment[%d]: %.200s", 173 retval2, PAM_STRERROR(pamh, retval2)); 174 } 175 authctxt->method->abandoned = 1; 176 177 /* 178 * Avoid double counting; these are incremented in 179 * kbdint_pam_abandon() so that they reflect the correct 180 * count when userauth_finish() is called before 181 * unwinding the dispatch_run() loop, but they are 182 * incremented again in input_userauth_request() when 183 * the loop is unwound, right here. 184 */ 185 if (authctxt->method->abandons) 186 authctxt->method->abandons--; 187 if (authctxt->method->attempts) 188 authctxt->method->attempts--; 189 } 190 else { 191 /* Save error value for pam_end() */ 192 authctxt->pam->last_pam_retval = retval; 193 log("Keyboard-interactive (PAM) userauth failed[%d] " 194 "while %s: %.200s", retval, where, 195 PAM_STRERROR(pamh, retval)); 196 /* pam handle can be reused elsewhere, so no pam_end() here */ 197 } 198 199 return; 200 } 201 202 static int 203 do_pam_conv_kbd_int(int num_msg, struct pam_message **msg, 204 struct pam_response **resp, void *appdata_ptr) 205 { 206 int i, j; 207 char *text; 208 Convctxt *conv_ctxt; 209 Authctxt *authctxt = (Authctxt *)appdata_ptr; 210 211 if (!authctxt || !authctxt->method) { 212 debug("Missing state during PAM conversation"); 213 return PAM_CONV_ERR; 214 } 215 216 conv_ctxt = xmalloc(sizeof(Convctxt)); 217 (void) memset(conv_ctxt, 0, sizeof(Convctxt)); 218 conv_ctxt->finished = 0; 219 conv_ctxt->num_received = 0; 220 conv_ctxt->num_expected = 0; 221 conv_ctxt->prompts = xmalloc(sizeof(int) * num_msg); 222 conv_ctxt->responses = xmalloc(sizeof(struct pam_response) * num_msg); 223 (void) memset(conv_ctxt->responses, 0, sizeof(struct pam_response) * num_msg); 224 225 text = NULL; 226 for (i = 0, conv_ctxt->num_expected = 0; i < num_msg; i++) { 227 int style = PAM_MSG_MEMBER(msg, i, msg_style); 228 switch (style) { 229 case PAM_PROMPT_ECHO_ON: 230 debug2("PAM echo on prompt: %s", 231 PAM_MSG_MEMBER(msg, i, msg)); 232 conv_ctxt->num_expected++; 233 break; 234 case PAM_PROMPT_ECHO_OFF: 235 debug2("PAM echo off prompt: %s", 236 PAM_MSG_MEMBER(msg, i, msg)); 237 conv_ctxt->num_expected++; 238 break; 239 case PAM_TEXT_INFO: 240 debug2("PAM text info prompt: %s", 241 PAM_MSG_MEMBER(msg, i, msg)); 242 message_cat(&text, PAM_MSG_MEMBER(msg, i, msg)); 243 break; 244 case PAM_ERROR_MSG: 245 debug2("PAM error prompt: %s", 246 PAM_MSG_MEMBER(msg, i, msg)); 247 message_cat(&text, PAM_MSG_MEMBER(msg, i, msg)); 248 break; 249 default: 250 /* Capture all these messages to be sent at once */ 251 message_cat(&text, PAM_MSG_MEMBER(msg, i, msg)); 252 break; 253 } 254 } 255 256 if (conv_ctxt->num_expected == 0 && text == NULL) { 257 xfree(conv_ctxt->prompts); 258 xfree(conv_ctxt->responses); 259 xfree(conv_ctxt); 260 return PAM_SUCCESS; 261 } 262 263 authctxt->method->method_data = (void *) conv_ctxt; 264 265 packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST); 266 packet_put_cstring(""); /* Name */ 267 packet_put_cstring(text ? text : ""); /* Instructions */ 268 packet_put_cstring(""); /* Language */ 269 packet_put_int(conv_ctxt->num_expected); 270 271 if (text) 272 xfree(text); 273 274 for (i = 0, j = 0; i < num_msg; i++) { 275 int style = PAM_MSG_MEMBER(msg, i, msg_style); 276 277 /* Skip messages which don't need a reply */ 278 if (style != PAM_PROMPT_ECHO_ON && style != PAM_PROMPT_ECHO_OFF) 279 continue; 280 281 conv_ctxt->prompts[j++] = i; 282 packet_put_cstring(PAM_MSG_MEMBER(msg, i, msg)); 283 packet_put_char(style == PAM_PROMPT_ECHO_ON); 284 } 285 packet_send(); 286 packet_write_wait(); 287 288 /* 289 * Here the dispatch_run() loop is nested. It should be unwound 290 * if keyboard-interactive userauth is abandoned (or restarted; 291 * same thing). 292 * 293 * The condition for breaking out of the nested dispatch_run() loop is 294 * ((got kbd-int info reponse) || (kbd-int abandoned)) 295 * 296 * conv_ctxt->finished is set in either of those cases. 297 * 298 * When abandonment is detected the conv_ctxt->finished is set as 299 * is conv_ctxt->abandoned, causing this function to signal 300 * userauth nested dispatch_run() loop unwinding and to return 301 * PAM_CONV_ERR; 302 */ 303 debug2("Nesting dispatch_run loop"); 304 dispatch_run(DISPATCH_BLOCK, &conv_ctxt->finished, appdata_ptr); 305 debug2("Nested dispatch_run loop exited"); 306 307 if (conv_ctxt->abandoned) { 308 authctxt->unwind_dispatch_loop = 1; 309 xfree(conv_ctxt->prompts); 310 xfree(conv_ctxt->responses); 311 xfree(conv_ctxt); 312 debug("PAM conv function returns PAM_CONV_ERR"); 313 return PAM_CONV_ERR; 314 } 315 316 if (conv_ctxt->num_received == conv_ctxt->num_expected) { 317 *resp = conv_ctxt->responses; 318 xfree(conv_ctxt->prompts); 319 xfree(conv_ctxt); 320 debug("PAM conv function returns PAM_SUCCESS"); 321 return PAM_SUCCESS; 322 } 323 324 debug("PAM conv function returns PAM_CONV_ERR"); 325 xfree(conv_ctxt->prompts); 326 xfree(conv_ctxt->responses); 327 xfree(conv_ctxt); 328 return PAM_CONV_ERR; 329 } 330 331 static void 332 input_userauth_info_response_pam(int type, u_int32_t seqnr, void *ctxt) 333 { 334 Authctxt *authctxt = ctxt; 335 Convctxt *conv_ctxt; 336 unsigned int nresp = 0, rlen = 0, i = 0; 337 char *resp; 338 339 if (authctxt == NULL) 340 fatal("input_userauth_info_response_pam: no authentication context"); 341 342 /* Check for spurious/unexpected info response */ 343 if (method_kbdint.method_data == NULL) { 344 debug("input_userauth_info_response_pam: no method context"); 345 return; 346 } 347 348 conv_ctxt = (Convctxt *) method_kbdint.method_data; 349 350 nresp = packet_get_int(); /* Number of responses. */ 351 debug("got %d responses", nresp); 352 353 354 #if 0 355 if (nresp != conv_ctxt->num_expected) 356 fatal("%s: Received incorrect number of responses " 357 "(expected %d, received %u)", __func__, 358 conv_ctxt->num_expected, nresp); 359 #endif 360 361 if (nresp > 100) 362 fatal("%s: too many replies", __func__); 363 364 for (i = 0; i < nresp && i < conv_ctxt->num_expected ; i++) { 365 int j = conv_ctxt->prompts[i]; 366 367 resp = packet_get_string(&rlen); 368 if (i < conv_ctxt->num_expected) { 369 conv_ctxt->responses[j].resp_retcode = PAM_SUCCESS; 370 conv_ctxt->responses[j].resp = xstrdup(resp); 371 conv_ctxt->num_received++; 372 } 373 xfree(resp); 374 } 375 376 if (nresp < conv_ctxt->num_expected) 377 fatal("%s: too few replies (%d < %d)", __func__, 378 nresp, conv_ctxt->num_expected); 379 380 /* XXX - This could make a covert channel... */ 381 if (nresp > conv_ctxt->num_expected) 382 debug("Ignoring additional PAM replies"); 383 384 conv_ctxt->finished = 1; 385 386 packet_check_eom(); 387 } 388 389 #if 0 390 int 391 kbdint_pam_abandon_chk(Authctxt *authctxt, Authmethod *method) 392 { 393 if (!method) 394 return 0; /* fatal(), really; it'll happen somewhere else */ 395 396 if (!method->method_data) 397 return 0; 398 399 return 1; 400 } 401 #endif 402 403 void 404 kbdint_pam_abandon(Authctxt *authctxt, Authmethod *method) 405 { 406 Convctxt *conv_ctxt; 407 408 /* 409 * But, if it ever becomes desirable and possible to support 410 * kbd-int userauth abandonment, here's what must be done. 411 */ 412 if (!method) 413 return; 414 415 if (!method->method_data) 416 return; 417 418 conv_ctxt = (Convctxt *) method->method_data; 419 420 /* dispatch_run() loop will exit */ 421 conv_ctxt->abandoned = 1; 422 conv_ctxt->finished = 1; 423 424 /* 425 * The method_data will be free in the corresponding, active 426 * conversation function 427 */ 428 method->method_data = NULL; 429 430 /* update counts that can't be updated elsewhere */ 431 method->abandons++; 432 method->attempts++; 433 434 /* Finally, we cannot re-use the current current PAM handle */ 435 authctxt->pam->h = NULL; /* Let the conv function cleanup */ 436 } 437 #endif 438