crypto/openssh/auth-pam.c

   1 /*
   2  * Copyright (c) 2000 Damien Miller.  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
  27 #ifdef USE_PAM
  28 #include "xmalloc.h"
  29 #include "log.h"
  30 #include "auth.h"
  31 #include "auth-options.h"
  32 #include "auth-pam.h"
  33 #include "servconf.h"
  34 #include "canohost.h"
  35 #include "readpass.h"
  36
  37 extern char *__progname;
  38
  39 extern int use_privsep;
  40
  41 RCSID("$Id: auth-pam.c,v 1.54 2002/07/28 20:24:08 stevesk Exp $");
  42 RCSID("$FreeBSD: src/crypto/openssh/auth-pam.c,v 1.2.2.4 2003/02/03 17:31:06 des Exp $");
  43
  44 #define NEW_AUTHTOK_MSG \
  45         "Warning: Your password has expired, please change it now."
  46 #define NEW_AUTHTOK_MSG_PRIVSEP \
  47         "Your password has expired, the session cannot proceed."
  48
  49 static int do_pam_conversation(int num_msg, const struct pam_message **msg,
  50         struct pam_response **resp, void *appdata_ptr);
  51
  52 /* module-local variables */
  53 static struct pam_conv conv = {
  54         (int (*)())do_pam_conversation,
  55         NULL
  56 };
  57 static char *__pam_msg = NULL;
  58 static pam_handle_t *__pamh = NULL;
  59 static const char *__pampasswd = NULL;
  60
  61 /* states for do_pam_conversation() */
  62 enum { INITIAL_LOGIN, OTHER } pamstate = INITIAL_LOGIN;
  63 /* remember whether pam_acct_mgmt() returned PAM_NEW_AUTHTOK_REQD */
  64 static int password_change_required = 0;
  65 /* remember whether the last pam_authenticate() succeeded or not */
  66 static int was_authenticated = 0;
  67
  68 /* Remember what has been initialised */
  69 static int session_opened = 0;
  70 static int creds_set = 0;
  71
  72 /* accessor which allows us to switch conversation structs according to
  73  * the authentication method being used */
  74 void do_pam_set_conv(struct pam_conv *conv)
  75 {
  76         pam_set_item(__pamh, PAM_CONV, conv);
  77 }
  78
  79 /* start an authentication run */
  80 int do_pam_authenticate(int flags)
  81 {
  82         int retval = pam_authenticate(__pamh, flags);
  83         was_authenticated = (retval == PAM_SUCCESS);
  84         return retval;
  85 }
  86
  87 /*
  88  * PAM conversation function.
  89  * There are two states this can run in.
  90  *
  91  * INITIAL_LOGIN mode simply feeds the password from the client into
  92  * PAM in response to PAM_PROMPT_ECHO_OFF, and collects output
  93  * messages with into __pam_msg.  This is used during initial
  94  * authentication to bypass the normal PAM password prompt.
  95  *
  96  * OTHER mode handles PAM_PROMPT_ECHO_OFF with read_passphrase()
  97  * and outputs messages to stderr. This mode is used if pam_chauthtok()
  98  * is called to update expired passwords.
  99  */
 100 static int do_pam_conversation(int num_msg, const struct pam_message **msg,
 101         struct pam_response **resp, void *appdata_ptr)
 102 {
 103         struct pam_response *reply;
 104         int count;
 105         char buf[1024];
 106
 107         /* PAM will free this later */
 108         reply = xmalloc(num_msg * sizeof(*reply));
 109
 110         for (count = 0; count < num_msg; count++) {
 111                 if (pamstate == INITIAL_LOGIN) {
 112                         /*
 113                          * We can't use stdio yet, queue messages for
 114                          * printing later
 115                          */
 116                         switch(PAM_MSG_MEMBER(msg, count, msg_style)) {
 117                         case PAM_PROMPT_ECHO_ON:
 118                                 xfree(reply);
 119                                 return PAM_CONV_ERR;
 120                         case PAM_PROMPT_ECHO_OFF:
 121                                 if (__pampasswd == NULL) {
 122                                         xfree(reply);
 123                                         return PAM_CONV_ERR;
 124                                 }
 125                                 reply[count].resp = xstrdup(__pampasswd);
 126                                 reply[count].resp_retcode = PAM_SUCCESS;
 127                                 break;
 128                         case PAM_ERROR_MSG:
 129                         case PAM_TEXT_INFO:
 130                                 if (PAM_MSG_MEMBER(msg, count, msg) != NULL) {
 131                                         message_cat(&__pam_msg,
 132                                             PAM_MSG_MEMBER(msg, count, msg));
 133                                 }
 134                                 reply[count].resp = xstrdup("");
 135                                 reply[count].resp_retcode = PAM_SUCCESS;
 136                                 break;
 137                         default:
 138                                 xfree(reply);
 139                                 return PAM_CONV_ERR;
 140                         }
 141                 } else {
 142                         /*
 143                          * stdio is connected, so interact directly
 144                          */
 145                         switch(PAM_MSG_MEMBER(msg, count, msg_style)) {
 146                         case PAM_PROMPT_ECHO_ON:
 147                                 fputs(PAM_MSG_MEMBER(msg, count, msg), stderr);
 148                                 fgets(buf, sizeof(buf), stdin);
 149                                 reply[count].resp = xstrdup(buf);
 150                                 reply[count].resp_retcode = PAM_SUCCESS;
 151                                 break;
 152                         case PAM_PROMPT_ECHO_OFF:
 153                                 reply[count].resp =
 154                                     read_passphrase(PAM_MSG_MEMBER(msg, count,
 155                                         msg), RP_ALLOW_STDIN);
 156                                 reply[count].resp_retcode = PAM_SUCCESS;
 157                                 break;
 158                         case PAM_ERROR_MSG:
 159                         case PAM_TEXT_INFO:
 160                                 if (PAM_MSG_MEMBER(msg, count, msg) != NULL)
 161                                         fprintf(stderr, "%s\n",
 162                                             PAM_MSG_MEMBER(msg, count, msg));
 163                                 reply[count].resp = xstrdup("");
 164                                 reply[count].resp_retcode = PAM_SUCCESS;
 165                                 break;
 166                         default:
 167                                 xfree(reply);
 168                                 return PAM_CONV_ERR;
 169                         }
 170                 }
 171         }
 172
 173         *resp = reply;
 174
 175         return PAM_SUCCESS;
 176 }
 177
 178 /* Called at exit to cleanly shutdown PAM */
 179 void do_pam_cleanup_proc(void *context)
 180 {
 181         int pam_retval = PAM_SUCCESS;
 182
 183         if (__pamh && session_opened) {
 184                 pam_retval = pam_close_session(__pamh, 0);
 185                 if (pam_retval != PAM_SUCCESS)
 186                         log("Cannot close PAM session[%d]: %.200s",
 187                             pam_retval, PAM_STRERROR(__pamh, pam_retval));
 188         }
 189
 190         if (__pamh && creds_set) {
 191                 pam_retval = pam_setcred(__pamh, PAM_DELETE_CRED);
 192                 if (pam_retval != PAM_SUCCESS)
 193                         debug("Cannot delete credentials[%d]: %.200s",
 194                             pam_retval, PAM_STRERROR(__pamh, pam_retval));
 195         }
 196
 197         if (__pamh) {
 198                 pam_retval = pam_end(__pamh, pam_retval);
 199                 if (pam_retval != PAM_SUCCESS)
 200                         log("Cannot release PAM authentication[%d]: %.200s",
 201                             pam_retval, PAM_STRERROR(__pamh, pam_retval));
 202         }
 203 }
 204
 205 /* Attempt password authentation using PAM */
 206 int auth_pam_password(Authctxt *authctxt, const char *password)
 207 {
 208         extern ServerOptions options;
 209         int pam_retval;
 210         struct passwd *pw = authctxt->pw;
 211
 212         do_pam_set_conv(&conv);
 213
 214         /* deny if no user. */
 215         if (pw == NULL)
 216                 return 0;
 217         if (pw->pw_uid == 0 && options.permit_root_login == PERMIT_NO_PASSWD)
 218                 return 0;
 219         if (*password == '\0' && options.permit_empty_passwd == 0)
 220                 return 0;
 221
 222         __pampasswd = password;
 223
 224         pamstate = INITIAL_LOGIN;
 225         pam_retval = do_pam_authenticate(
 226             options.permit_empty_passwd == 0 ? PAM_DISALLOW_NULL_AUTHTOK : 0);
 227         if (pam_retval == PAM_SUCCESS) {
 228                 debug("PAM Password authentication accepted for "
 229                     "user \"%.100s\"", pw->pw_name);
 230                 return 1;
 231         } else {
 232                 debug("PAM Password authentication for \"%.100s\" "
 233                     "failed[%d]: %s", pw->pw_name, pam_retval,
 234                     PAM_STRERROR(__pamh, pam_retval));
 235                 return 0;
 236         }
 237 }
 238
 239 /* Do account management using PAM */
 240 int do_pam_account(char *username, char *remote_user)
 241 {
 242         int pam_retval;
 243
 244         do_pam_set_conv(&conv);
 245
 246         if (remote_user) {
 247                 debug("PAM setting ruser to \"%.200s\"", remote_user);
 248                 pam_retval = pam_set_item(__pamh, PAM_RUSER, remote_user);
 249                 if (pam_retval != PAM_SUCCESS)
 250                         fatal("PAM set ruser failed[%d]: %.200s", pam_retval,
 251                             PAM_STRERROR(__pamh, pam_retval));
 252         }
 253
 254         pam_retval = pam_acct_mgmt(__pamh, 0);
 255         debug2("pam_acct_mgmt() = %d", pam_retval);
 256         switch (pam_retval) {
 257                 case PAM_SUCCESS:
 258                         /* This is what we want */
 259                         break;
 260 #if 0
 261                 case PAM_NEW_AUTHTOK_REQD:
 262                         message_cat(&__pam_msg, use_privsep ?
 263                             NEW_AUTHTOK_MSG_PRIVSEP : NEW_AUTHTOK_MSG);
 264                         /* flag that password change is necessary */
 265                         password_change_required = 1;
 266                         /* disallow other functionality for now */
 267                         no_port_forwarding_flag |= 2;
 268                         no_agent_forwarding_flag |= 2;
 269                         no_x11_forwarding_flag |= 2;
 270                         break;
 271 #endif
 272                 default:
 273                         log("PAM rejected by account configuration[%d]: "
 274                             "%.200s", pam_retval, PAM_STRERROR(__pamh,
 275                             pam_retval));
 276                         return(0);
 277         }
 278
 279         return(1);
 280 }
 281
 282 /* Do PAM-specific session initialisation */
 283 void do_pam_session(char *username, const char *ttyname)
 284 {
 285         int pam_retval;
 286
 287         do_pam_set_conv(&conv);
 288
 289         if (ttyname != NULL) {
 290                 debug("PAM setting tty to \"%.200s\"", ttyname);
 291                 pam_retval = pam_set_item(__pamh, PAM_TTY, ttyname);
 292                 if (pam_retval != PAM_SUCCESS)
 293                         fatal("PAM set tty failed[%d]: %.200s",
 294                             pam_retval, PAM_STRERROR(__pamh, pam_retval));
 295         }
 296
 297         pam_retval = pam_open_session(__pamh, 0);
 298         if (pam_retval != PAM_SUCCESS)
 299                 fatal("PAM session setup failed[%d]: %.200s",
 300                     pam_retval, PAM_STRERROR(__pamh, pam_retval));
 301
 302         session_opened = 1;
 303 }
 304
 305 /* Set PAM credentials */
 306 void do_pam_setcred(int init)
 307 {
 308         int pam_retval;
 309
 310         if (__pamh == NULL)
 311                 return;
 312
 313         do_pam_set_conv(&conv);
 314
 315         debug("PAM establishing creds");
 316         pam_retval = pam_setcred(__pamh,
 317             init ? PAM_ESTABLISH_CRED : PAM_REINITIALIZE_CRED);
 318         if (pam_retval != PAM_SUCCESS) {
 319                 if (was_authenticated)
 320                         fatal("PAM setcred failed[%d]: %.200s",
 321                             pam_retval, PAM_STRERROR(__pamh, pam_retval));
 322                 else
 323                         debug("PAM setcred failed[%d]: %.200s",
 324                             pam_retval, PAM_STRERROR(__pamh, pam_retval));
 325         } else
 326                 creds_set = 1;
 327 }
 328
 329 /* accessor function for file scope static variable */
 330 int is_pam_password_change_required(void)
 331 {
 332         return password_change_required;
 333 }
 334
 335 /*
 336  * Have user change authentication token if pam_acct_mgmt() indicated
 337  * it was expired.  This needs to be called after an interactive
 338  * session is established and the user's pty is connected to
 339  * stdin/stdout/stderr.
 340  */
 341 void do_pam_chauthtok(void)
 342 {
 343         int pam_retval;
 344
 345         do_pam_set_conv(&conv);
 346
 347         if (password_change_required) {
 348                 if (use_privsep)
 349                         fatal("Password changing is currently unsupported"
 350                             " with privilege separation");
 351                 pamstate = OTHER;
 352                 pam_retval = pam_chauthtok(__pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
 353                 if (pam_retval != PAM_SUCCESS)
 354                         fatal("PAM pam_chauthtok failed[%d]: %.200s",
 355                             pam_retval, PAM_STRERROR(__pamh, pam_retval));
 356 #if 0
 357                 /* XXX: This would need to be done in the parent process,
 358                  * but there's currently no way to pass such request. */
 359                 no_port_forwarding_flag &= ~2;
 360                 no_agent_forwarding_flag &= ~2;
 361                 no_x11_forwarding_flag &= ~2;
 362                 if (!no_port_forwarding_flag && options.allow_tcp_forwarding)
 363                         channel_permit_all_opens();
 364 #endif
 365         }
 366 }
 367
 368 /* Cleanly shutdown PAM */
 369 void finish_pam(void)
 370 {
 371         do_pam_cleanup_proc(NULL);
 372         fatal_remove_cleanup(&do_pam_cleanup_proc, NULL);
 373 }
 374
 375 /* Start PAM authentication for specified account */
 376 void start_pam(const char *user)
 377 {
 378         int pam_retval;
 379         extern ServerOptions options;
 380         extern u_int utmp_len;
 381         const char *rhost;
 382
 383         debug("Starting up PAM with username \"%.200s\"", user);
 384
 385         pam_retval = pam_start(SSHD_PAM_SERVICE, user, &conv, &__pamh);
 386
 387         if (pam_retval != PAM_SUCCESS)
 388                 fatal("PAM initialisation failed[%d]: %.200s",
 389                     pam_retval, PAM_STRERROR(__pamh, pam_retval));
 390
 391         rhost = get_remote_name_or_ip(utmp_len, options.verify_reverse_mapping);
 392         debug("PAM setting rhost to \"%.200s\"", rhost);
 393
 394         pam_retval = pam_set_item(__pamh, PAM_RHOST, rhost);
 395         if (pam_retval != PAM_SUCCESS)
 396                 fatal("PAM set rhost failed[%d]: %.200s", pam_retval,
 397                     PAM_STRERROR(__pamh, pam_retval));
 398 #ifdef PAM_TTY_KLUDGE
 399         /*
 400          * Some PAM modules (e.g. pam_time) require a TTY to operate,
 401          * and will fail in various stupid ways if they don't get one.
 402          * sshd doesn't set the tty until too late in the auth process and may
 403          * not even need one (for tty-less connections)
 404          * Kludge: Set a fake PAM_TTY
 405          */
 406         pam_retval = pam_set_item(__pamh, PAM_TTY, "NODEVssh");
 407         if (pam_retval != PAM_SUCCESS)
 408                 fatal("PAM set tty failed[%d]: %.200s",
 409                     pam_retval, PAM_STRERROR(__pamh, pam_retval));
 410 #endif /* PAM_TTY_KLUDGE */
 411
 412         fatal_add_cleanup(&do_pam_cleanup_proc, NULL);
 413 }
 414
 415 /* Return list of PAM environment strings */
 416 char **fetch_pam_environment(void)
 417 {
 418 #ifdef HAVE_PAM_GETENVLIST
 419         return(pam_getenvlist(__pamh));
 420 #else /* HAVE_PAM_GETENVLIST */
 421         return(NULL);
 422 #endif /* HAVE_PAM_GETENVLIST */
 423 }
 424
 425 void free_pam_environment(char **env)
 426 {
 427         int i;
 428
 429         if (env != NULL) {
 430                 for (i = 0; env[i] != NULL; i++)
 431                         xfree(env[i]);
 432         }
 433 }
 434
 435 /* Print any messages that have been generated during authentication */
 436 /* or account checking to stderr */
 437 void print_pam_messages(void)
 438 {
 439         if (__pam_msg != NULL)
 440                 fputs(__pam_msg, stderr);
 441 }
 442
 443 /* Append a message to buffer */
 444 void message_cat(char **p, const char *a)
 445 {
 446         char *cp;
 447         size_t new_len;
 448
 449         new_len = strlen(a);
 450
 451         if (*p) {
 452                 size_t len = strlen(*p);
 453
 454                 *p = xrealloc(*p, new_len + len + 2);
 455                 cp = *p + len;
 456         } else
 457                 *p = cp = xmalloc(new_len + 2);
 458
 459         memcpy(cp, a, new_len);
 460         cp[new_len] = '\n';
 461         cp[new_len + 1] = '\0';
 462 }
 463
 464 #endif /* USE_PAM */