pppd/session.c

   1 /*
   2  * session.c - PPP session control.
   3  *
   4  * Copyright (c) 2007 Diego Rivera. All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. The name(s) of the authors of this software must not be used to
  14  *    endorse or promote products derived from this software without
  15  *    prior written permission.
  16  *
  17  * 3. Redistributions of any form whatsoever must retain the following
  18  *    acknowledgment:
  19  *    "This product includes software developed by Paul Mackerras
  20  *     <paulus@samba.org>".
  21  *
  22  * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
  23  * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
  24  * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
  25  * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  26  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
  27  * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
  28  * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  29  *
  30  * Derived from auth.c, which is:
  31  *
  32  * Copyright (c) 1984-2000 Carnegie Mellon University. All rights reserved.
  33  *
  34  * Redistribution and use in source and binary forms, with or without
  35  * modification, are permitted provided that the following conditions
  36  * are met:
  37  *
  38  * 1. Redistributions of source code must retain the above copyright
  39  *    notice, this list of conditions and the following disclaimer.
  40  *
  41  * 2. Redistributions in binary form must reproduce the above copyright
  42  *    notice, this list of conditions and the following disclaimer in
  43  *    the documentation and/or other materials provided with the
  44  *    distribution.
  45  *
  46  * 3. The name "Carnegie Mellon University" must not be used to
  47  *    endorse or promote products derived from this software without
  48  *    prior written permission. For permission or any legal
  49  *    details, please contact
  50  *      Office of Technology Transfer
  51  *      Carnegie Mellon University
  52  *      5000 Forbes Avenue
  53  *      Pittsburgh, PA  15213-3890
  54  *      (412) 268-4387, fax: (412) 268-7395
  55  *      tech-transfer@andrew.cmu.edu
  56  *
  57  * 4. Redistributions of any form whatsoever must retain the following
  58  *    acknowledgment:
  59  *    "This product includes software developed by Computing Services
  60  *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
  61  *
  62  * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
  63  * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
  64  * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
  65  * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  66  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
  67  * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
  68  * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  69  */
  70
  71 #include <stdio.h>
  72 #include <stdlib.h>
  73 #include <string.h>
  74 #include <pwd.h>
  75 #include <crypt.h>
  76 #ifdef HAS_SHADOW
  77 #include <shadow.h>
  78 #endif
  79 #include <time.h>
  80 #include <utmp.h>
  81 #include <fcntl.h>
  82 #include <unistd.h>
  83 #include "pppd.h"
  84 #include "session.h"
  85
  86 #ifdef USE_PAM
  87 #include <security/pam_appl.h>
  88 #endif /* #ifdef USE_PAM */
  89
  90 #define SET_MSG(var, msg) if (var != NULL) { var[0] = msg; }
  91 #define COPY_STRING(s) ((s) ? strdup(s) : NULL)
  92
  93 #define SUCCESS_MSG "Session started successfully"
  94 #define ABORT_MSG "Session can't be started without a username"
  95 #define SERVICE_NAME "ppp"
  96
  97 #define SESSION_FAILED  0
  98 #define SESSION_OK      1
  99
 100 /* We have successfully started a session */
 101 static bool logged_in = 0;
 102
 103 #ifdef USE_PAM
 104 /*
 105  * Static variables used to communicate between the conversation function
 106  * and the server_login function
 107  */
 108 static const char *PAM_username;
 109 static const char *PAM_password;
 110 static int   PAM_session = 0;
 111 static pam_handle_t *pamh = NULL;
 112
 113 /* PAM conversation function
 114  * Here we assume (for now, at least) that echo on means login name, and
 115  * echo off means password.
 116  */
 117
 118 static int conversation (int num_msg,
 119 #ifndef SOL2
 120     const
 121 #endif
 122     struct pam_message **msg,
 123     struct pam_response **resp, void *appdata_ptr)
 124 {
 125     int replies = 0;
 126     struct pam_response *reply = NULL;
 127
 128     reply = malloc(sizeof(struct pam_response) * num_msg);
 129     if (!reply) return PAM_CONV_ERR;
 130
 131     for (replies = 0; replies < num_msg; replies++) {
 132         switch (msg[replies]->msg_style) {
 133             case PAM_PROMPT_ECHO_ON:
 134                 reply[replies].resp_retcode = PAM_SUCCESS;
 135                 reply[replies].resp = COPY_STRING(PAM_username);
 136                 /* PAM frees resp */
 137                 break;
 138             case PAM_PROMPT_ECHO_OFF:
 139                 reply[replies].resp_retcode = PAM_SUCCESS;
 140                 reply[replies].resp = COPY_STRING(PAM_password);
 141                 /* PAM frees resp */
 142                 break;
 143             case PAM_TEXT_INFO:
 144                 /* fall through */
 145             case PAM_ERROR_MSG:
 146                 /* ignore it, but pam still wants a NULL response... */
 147                 reply[replies].resp_retcode = PAM_SUCCESS;
 148                 reply[replies].resp = NULL;
 149                 break;
 150             default:
 151                 /* Must be an error of some sort... */
 152                 free (reply);
 153                 return PAM_CONV_ERR;
 154         }
 155     }
 156     *resp = reply;
 157     return PAM_SUCCESS;
 158 }
 159
 160 static struct pam_conv pam_conv_data = {
 161     &conversation,
 162     NULL
 163 };
 164 #endif /* #ifdef USE_PAM */
 165
 166 int
 167 session_start(flags, user, passwd, ttyName, msg)
 168     const int flags;
 169     const char *user;
 170     const char *passwd;
 171     const char *ttyName;
 172     char **msg;
 173 {
 174 #ifdef USE_PAM
 175     bool ok = 1;
 176     const char *usr;
 177     int pam_error;
 178     bool try_session = 0;
 179 #else /* #ifdef USE_PAM */
 180     struct passwd *pw;
 181 #ifdef HAS_SHADOW
 182     struct spwd *spwd;
 183     struct spwd *getspnam();
 184     long now = 0;
 185 #endif /* #ifdef HAS_SHADOW */
 186 #endif /* #ifdef USE_PAM */
 187
 188     SET_MSG(msg, SUCCESS_MSG);
 189
 190     /* If no verification is requested, then simply return an OK */
 191     if (!(SESS_ALL & flags)) {
 192         return SESSION_OK;
 193     }
 194
 195     if (user == NULL) {
 196        SET_MSG(msg, ABORT_MSG);
 197        return SESSION_FAILED;
 198     }
 199
 200 #ifdef USE_PAM
 201     /* Find the '\\' in the username */
 202     /* This needs to be fixed to support different username schemes */
 203     if ((usr = strchr(user, '\\')) == NULL)
 204         usr = user;
 205     else
 206         usr++;
 207
 208     PAM_session = 0;
 209     PAM_username = usr;
 210     PAM_password = passwd;
 211
 212     dbglog("Initializing PAM (%d) for user %s", flags, usr);
 213     pam_error = pam_start (SERVICE_NAME, usr, &pam_conv_data, &pamh);
 214     dbglog("---> PAM INIT Result = %d", pam_error);
 215     ok = (pam_error == PAM_SUCCESS);
 216
 217     if (ok) {
 218         ok = (pam_set_item(pamh, PAM_TTY, ttyName) == PAM_SUCCESS) &&
 219             (pam_set_item(pamh, PAM_RHOST, ifname) == PAM_SUCCESS);
 220     }
 221
 222     if (ok && (SESS_AUTH & flags)) {
 223         dbglog("Attempting PAM authentication");
 224         pam_error = pam_authenticate (pamh, PAM_SILENT);
 225         if (pam_error == PAM_SUCCESS) {
 226             /* PAM auth was OK */
 227             dbglog("PAM Authentication OK for %s", user);
 228         } else {
 229             /* No matter the reason, we fail because we're authenticating */
 230             ok = 0;
 231             if (pam_error == PAM_USER_UNKNOWN) {
 232                 dbglog("User unknown, failing PAM authentication");
 233                 SET_MSG(msg, "User unknown - cannot authenticate via PAM");
 234             } else {
 235                 /* Any other error means authentication was bad */
 236                 dbglog("PAM Authentication failed: %d: %s", pam_error,
 237                        pam_strerror(pamh, pam_error));
 238                 SET_MSG(msg, (char *) pam_strerror (pamh, pam_error));
 239             }
 240         }
 241     }
 242
 243     if (ok && (SESS_ACCT & flags)) {
 244         dbglog("Attempting PAM account checks");
 245         pam_error = pam_acct_mgmt (pamh, PAM_SILENT);
 246         if (pam_error == PAM_SUCCESS) {
 247             /*
 248              * PAM account was OK, set the flag which indicates that we should
 249              * try to perform the session checks.
 250              */
 251             try_session = 1;
 252             dbglog("PAM Account OK for %s", user);
 253         } else {
 254             /*
 255              * If the account checks fail, then we should not try to perform
 256              * the session check, because they don't make sense.
 257              */
 258             try_session = 0;
 259             if (pam_error == PAM_USER_UNKNOWN) {
 260                 /*
 261                  * We're checking the account, so it's ok to not have one
 262                  * because the user might come from the secrets files, or some
 263                  * other plugin.
 264                  */
 265                 dbglog("User unknown, ignoring PAM restrictions");
 266                 SET_MSG(msg, "User unknown - ignoring PAM restrictions");
 267             } else {
 268                 /* Any other error means session is rejected */
 269                 ok = 0;
 270                 dbglog("PAM Account checks failed: %d: %s", pam_error,
 271                        pam_strerror(pamh, pam_error));
 272                 SET_MSG(msg, (char *) pam_strerror (pamh, pam_error));
 273             }
 274         }
 275     }
 276
 277     if (ok && try_session && (SESS_ACCT & flags)) {
 278         /* Only open a session if the user's account was found */
 279         pam_error = pam_open_session (pamh, PAM_SILENT);
 280         if (pam_error == PAM_SUCCESS) {
 281             dbglog("PAM Session opened for user %s", user);
 282             PAM_session = 1;
 283         } else {
 284             dbglog("PAM Session denied for user %s", user);
 285             SET_MSG(msg, (char *) pam_strerror (pamh, pam_error));
 286             ok = 0;
 287         }
 288     }
 289
 290     /* This is needed because apparently the PAM stuff closes the log */
 291     reopen_log();
 292
 293     /* If our PAM checks have already failed, then we must return a failure */
 294     if (!ok) return SESSION_FAILED;
 295
 296 #else /* #ifdef USE_PAM */
 297
 298 /*
 299  * Use the non-PAM methods directly.  'pw' will remain NULL if the user
 300  * has not been authenticated using local UNIX system services.
 301  */
 302
 303     pw = NULL;
 304     if ((SESS_AUTH & flags)) {
 305         pw = getpwnam(user);
 306
 307         endpwent();
 308         /*
 309          * Here, we bail if we have no user account, because there is nothing
 310          * to verify against.
 311          */
 312         if (pw == NULL)
 313             return SESSION_FAILED;
 314
 315 #ifdef HAS_SHADOW
 316
 317         spwd = getspnam(user);
 318         endspent();
 319
 320         /*
 321          * If there is no shadow entry for the user, then we can't verify the
 322          * account.
 323          */
 324         if (spwd == NULL)
 325             return SESSION_FAILED;
 326
 327         /*
 328          * We check validity all the time, because if the password has expired,
 329          * then clearly we should not authenticate against it (if we're being
 330          * called for authentication only).  Thus, in this particular instance,
 331          * there is no real difference between using the AUTH, SESS or ACCT
 332          * flags, or combinations thereof.
 333          */
 334         now = time(NULL) / 86400L;
 335         if ((spwd->sp_expire > 0 && now >= spwd->sp_expire)
 336             || ((spwd->sp_max >= 0 && spwd->sp_max < 10000)
 337             && spwd->sp_lstchg >= 0
 338             && now >= spwd->sp_lstchg + spwd->sp_max)) {
 339             warn("Password for %s has expired", user);
 340             return SESSION_FAILED;
 341         }
 342
 343         /* We have a valid shadow entry, keep the password */
 344         pw->pw_passwd = spwd->sp_pwdp;
 345
 346 #endif /* #ifdef HAS_SHADOW */
 347
 348         /*
 349          * If no passwd, don't let them login if we're authenticating.
 350          */
 351         if (pw->pw_passwd == NULL || strlen(pw->pw_passwd) < 2
 352             || strcmp(crypt(passwd, pw->pw_passwd), pw->pw_passwd) != 0)
 353             return SESSION_FAILED;
 354     }
 355
 356 #endif /* #ifdef USE_PAM */
 357
 358     /*
 359      * Write a wtmp entry for this user.
 360      */
 361
 362     if (SESS_ACCT & flags) {
 363         if (strncmp(ttyName, "/dev/", 5) == 0)
 364             ttyName += 5;
 365         logwtmp(ttyName, user, ifname); /* Add wtmp login entry */
 366         logged_in = 1;
 367
 368 #if defined(_PATH_LASTLOG) && !defined(USE_PAM)
 369         /*
 370          * Enter the user in lastlog only if he has been authenticated using
 371          * local system services.  If he has not, then we don't know what his
 372          * UID might be, and lastlog is indexed by UID.
 373          */
 374         if (pw != NULL) {
 375             struct lastlog ll;
 376             int fd;
 377             time_t tnow;
 378
 379             if ((fd = open(_PATH_LASTLOG, O_RDWR, 0)) >= 0) {
 380                 (void)lseek(fd, (off_t)(pw->pw_uid * sizeof(ll)), SEEK_SET);
 381                 memset((void *)&ll, 0, sizeof(ll));
 382                 (void)time(&tnow);
 383                 ll.ll_time = tnow;
 384                 (void)strncpy(ll.ll_line, ttyName, sizeof(ll.ll_line));
 385                 (void)strncpy(ll.ll_host, ifname, sizeof(ll.ll_host));
 386                 (void)write(fd, (char *)&ll, sizeof(ll));
 387                 (void)close(fd);
 388             }
 389         }
 390 #endif /* _PATH_LASTLOG and not USE_PAM */
 391         info("user %s logged in on tty %s intf %s", user, ttyName, ifname);
 392     }
 393
 394     return SESSION_OK;
 395 }
 396
 397 /*
 398  * session_end - Logout the user.
 399  */
 400 void
 401 session_end(const char* ttyName)
 402 {
 403 #ifdef USE_PAM
 404     int pam_error = PAM_SUCCESS;
 405
 406     if (pamh != NULL) {
 407         if (PAM_session) pam_error = pam_close_session (pamh, PAM_SILENT);
 408         PAM_session = 0;
 409         pam_end (pamh, pam_error);
 410         pamh = NULL;
 411         /* Apparently the pam stuff does closelog(). */
 412         reopen_log();
 413     }
 414 #endif
 415     if (logged_in) {
 416         if (strncmp(ttyName, "/dev/", 5) == 0)
 417             ttyName += 5;
 418         logwtmp(ttyName, "", ""); /* Wipe out utmp logout entry */
 419         logged_in = 0;
 420     }
 421 }