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