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pam_winbind.c

/* pam_winbind module

   Copyright Andrew Tridgell <tridge@samba.org> 2000
   Copyright Tim Potter <tpot@samba.org> 2000
   Copyright Andrew Bartlett <abartlet@samba.org> 2002

   largely based on pam_userdb by Christian Gafton <gafton@redhat.com> 
   also contains large slabs of code from pam_unix by Elliot Lee <sopwith@redhat.com>
   (see copyright below for full details)
*/

#include "pam_winbind.h"

/* prototypes from common.c */
void init_request(struct winbindd_request *req,int rq_type);
int write_sock(void *buffer, int count);
int read_reply(struct winbindd_response *response);

/* data tokens */

#define MAX_PASSWD_TRIES      3

/* some syslogging */
static void _pam_log(int err, const char *format, ...)
{
      va_list args;

      va_start(args, format);
      openlog(MODULE_NAME, LOG_CONS|LOG_PID, LOG_AUTH);
      vsyslog(err, format, args);
      va_end(args);
      closelog();
}

static int _pam_parse(int argc, const char **argv)
{
      int ctrl;
      /* step through arguments */
      for (ctrl = 0; argc-- > 0; ++argv) {

            /* generic options */
            
            if (!strcmp(*argv,"debug"))
                  ctrl |= WINBIND_DEBUG_ARG;
            else if (!strcasecmp(*argv, "use_authtok"))
                  ctrl |= WINBIND_USE_AUTHTOK_ARG;
            else if (!strcasecmp(*argv, "use_first_pass"))
                  ctrl |= WINBIND_TRY_FIRST_PASS_ARG;
            else if (!strcasecmp(*argv, "try_first_pass"))
                  ctrl |= WINBIND_USE_FIRST_PASS_ARG;
            else if (!strcasecmp(*argv, "unknown_ok"))
                  ctrl |= WINBIND_UNKNOWN_OK_ARG;
            else {
                  _pam_log(LOG_ERR, "pam_parse: unknown option; %s", *argv);
            }
      }
      
      return ctrl;
}

/* --- authentication management functions --- */

/* Attempt a conversation */

static int converse(pam_handle_t *pamh, int nargs,
                struct pam_message **message,
                struct pam_response **response)
{
    int retval;
    struct pam_conv *conv;

    retval = pam_get_item(pamh, PAM_CONV, (const void **) &conv ) ;
    if (retval == PAM_SUCCESS) {
      retval = conv->conv(nargs, (const struct pam_message **)message,
                      response, conv->appdata_ptr);
    }
      
    return retval; /* propagate error status */
}


int _make_remark(pam_handle_t * pamh, int type, char *text)
{
      int retval = PAM_SUCCESS;

      struct pam_message *pmsg[1], msg[1];
      struct pam_response *resp;
      
      pmsg[0] = &msg[0];
      msg[0].msg = text;
      msg[0].msg_style = type;
      
      resp = NULL;
      retval = converse(pamh, 1, pmsg, &resp);
      
      if (resp) {
            _pam_drop_reply(resp, 1);
      }
      return retval;
}

static int winbind_request(enum winbindd_cmd req_type,
                           struct winbindd_request *request,
                           struct winbindd_response *response)
{
      /* Fill in request and send down pipe */
      init_request(request, req_type);
      
      if (write_sock(request, sizeof(*request)) == -1) {
            _pam_log(LOG_ERR, "write to socket failed!");
            return PAM_SERVICE_ERR;
      }
      
      /* Wait for reply */
      if (read_reply(response) == -1) {
            _pam_log(LOG_ERR, "read from socket failed!");
            return PAM_SERVICE_ERR;
      }

      /* Copy reply data from socket */
      if (response->result != WINBINDD_OK) {
            if (response->data.auth.pam_error != PAM_SUCCESS) {
                  _pam_log(LOG_ERR, "request failed, PAM error was %d, NT error was %s", 
                         response->data.auth.pam_error,
                         response->data.auth.nt_status_string);
                  return response->data.auth.pam_error;
            } else {
                  _pam_log(LOG_ERR, "request failed, but PAM error 0!");
                  return PAM_SERVICE_ERR;
            }
      }
      
      return PAM_SUCCESS;
}

/* talk to winbindd */
static int winbind_auth_request(char *user, char *pass, int ctrl)
{
      struct winbindd_request request;
      struct winbindd_response response;
      int retval;

      ZERO_STRUCT(request);

      strncpy(request.data.auth.user, user, 
                sizeof(request.data.auth.user)-1);

      strncpy(request.data.auth.pass, pass, 
                sizeof(request.data.auth.pass)-1);
      
        retval = winbind_request(WINBINDD_PAM_AUTH, &request, &response);

      switch (retval) {
      case PAM_AUTH_ERR:
            /* incorrect password */
            _pam_log(LOG_WARNING, "user `%s' denied access (incorrect password)", user);
            return retval;
      case PAM_USER_UNKNOWN:
            /* the user does not exist */
            if (ctrl & WINBIND_DEBUG_ARG)
                  _pam_log(LOG_NOTICE, "user `%s' not found",
                         user);
            if (ctrl & WINBIND_UNKNOWN_OK_ARG) {
                  return PAM_IGNORE;
            }      
            return retval;
      case PAM_SUCCESS:
            /* Otherwise, the authentication looked good */
            _pam_log(LOG_NOTICE, "user '%s' granted acces", user);
            return retval;
      default:
            /* we don't know anything about this return value */
            _pam_log(LOG_ERR, "internal module error (retval = %d, user = `%s'",
                   retval, user);
            return retval;
      }
     /* should not be reached */
}

/* talk to winbindd */
static int winbind_chauthtok_request(const char *user, const char *oldpass,
                                     const char *newpass)
{
      struct winbindd_request request;
      struct winbindd_response response;

      ZERO_STRUCT(request);

        if (request.data.chauthtok.user == NULL) return -2;

      strncpy(request.data.chauthtok.user, user, 
                sizeof(request.data.chauthtok.user) - 1);

        if (oldpass != NULL) {
            strncpy(request.data.chauthtok.oldpass, oldpass, 
                    sizeof(request.data.chauthtok.oldpass) - 1);
        } else {
            request.data.chauthtok.oldpass[0] = '\0';
        }
      
        if (newpass != NULL) {
            strncpy(request.data.chauthtok.newpass, newpass, 
                    sizeof(request.data.chauthtok.newpass) - 1);
        } else {
            request.data.chauthtok.newpass[0] = '\0';
        }
      
        return winbind_request(WINBINDD_PAM_CHAUTHTOK, &request, &response);
}

/*
 * Checks if a user has an account
 *
 * return values:
 *     1  = User not found
 *     0  = OK
 *    -1  = System error
 */
static int valid_user(char *user)
{
      if (getpwnam(user)) return 0;
      return 1;
}

static char *_pam_delete(register char *xx)
{
    _pam_overwrite(xx);
    _pam_drop(xx);
    return NULL;
}

/*
 * obtain a password from the user
 */

int _winbind_read_password(pam_handle_t * pamh
                  ,unsigned int ctrl
                  ,char *comment
                  ,char *prompt1
                  ,char *prompt2
                  ,char **pass)
{
      int authtok_flag;
      int retval;
      char *item;
      char *token;

      /*
       * make sure nothing inappropriate gets returned
       */

      *pass = token = NULL;

      /*
       * which authentication token are we getting?
       */

      authtok_flag = on(WINBIND__OLD_PASSWORD, ctrl) ? PAM_OLDAUTHTOK : PAM_AUTHTOK;

      /*
       * should we obtain the password from a PAM item ?
       */

      if (on(WINBIND_TRY_FIRST_PASS_ARG, ctrl) || on(WINBIND_USE_FIRST_PASS_ARG, ctrl)) {
            retval = pam_get_item(pamh, authtok_flag, (const void **) &item);
            if (retval != PAM_SUCCESS) {
                  /* very strange. */
                  _pam_log(LOG_ALERT, 
                         "pam_get_item returned error to unix-read-password"
                      );
                  return retval;
            } else if (item != NULL) {    /* we have a password! */
                  *pass = item;
                  item = NULL;
                  return PAM_SUCCESS;
            } else if (on(WINBIND_USE_FIRST_PASS_ARG, ctrl)) {
                  return PAM_AUTHTOK_RECOVER_ERR;           /* didn't work */
            } else if (on(WINBIND_USE_AUTHTOK_ARG, ctrl)
                     && off(WINBIND__OLD_PASSWORD, ctrl)) {
                  return PAM_AUTHTOK_RECOVER_ERR;
            }
      }
      /*
       * getting here implies we will have to get the password from the
       * user directly.
       */

      {
            struct pam_message msg[3], *pmsg[3];
            struct pam_response *resp;
            int i, replies;

            /* prepare to converse */

            if (comment != NULL) {
                  pmsg[0] = &msg[0];
                  msg[0].msg_style = PAM_TEXT_INFO;
                  msg[0].msg = comment;
                  i = 1;
            } else {
                  i = 0;
            }

            pmsg[i] = &msg[i];
            msg[i].msg_style = PAM_PROMPT_ECHO_OFF;
            msg[i++].msg = prompt1;
            replies = 1;

            if (prompt2 != NULL) {
                  pmsg[i] = &msg[i];
                  msg[i].msg_style = PAM_PROMPT_ECHO_OFF;
                  msg[i++].msg = prompt2;
                  ++replies;
            }
            /* so call the conversation expecting i responses */
            resp = NULL;
            retval = converse(pamh, i, pmsg, &resp);

            if (resp != NULL) {

                  /* interpret the response */

                  if (retval == PAM_SUCCESS) {  /* a good conversation */

                        token = x_strdup(resp[i - replies].resp);
                        if (token != NULL) {
                              if (replies == 2) {

                                    /* verify that password entered correctly */
                                    if (!resp[i - 1].resp
                                        || strcmp(token, resp[i - 1].resp)) {
                                          _pam_delete(token);     /* mistyped */
                                          retval = PAM_AUTHTOK_RECOVER_ERR;
                                          _make_remark(pamh                                               ,PAM_ERROR_MSG, MISTYPED_PASS);
                                    }
                              }
                        } else {
                              _pam_log(LOG_NOTICE
                                     ,"could not recover authentication token");
                        }

                  }
                  /*
                   * tidy up the conversation (resp_retcode) is ignored
                   * -- what is it for anyway? AGM
                   */

                  _pam_drop_reply(resp, i);

            } else {
                  retval = (retval == PAM_SUCCESS)
                      ? PAM_AUTHTOK_RECOVER_ERR : retval;
            }
      }

      if (retval != PAM_SUCCESS) {
            if (on(WINBIND_DEBUG_ARG, ctrl))
                  _pam_log(LOG_DEBUG,
                           "unable to obtain a password");
            return retval;
      }
      /* 'token' is the entered password */

      /* we store this password as an item */
      
      retval = pam_set_item(pamh, authtok_flag, token);
      _pam_delete(token);     /* clean it up */
      if (retval != PAM_SUCCESS
          || (retval = pam_get_item(pamh, authtok_flag
                              ,(const void **) &item))
          != PAM_SUCCESS) {
            
            _pam_log(LOG_CRIT, "error manipulating password");
            return retval;
            
      }

      *pass = item;
      item = NULL;            /* break link to password */

      return PAM_SUCCESS;
}

PAM_EXTERN
int pam_sm_authenticate(pam_handle_t *pamh, int flags,
                  int argc, const char **argv)
{
     char *username;
     char *password;
     int retval = PAM_AUTH_ERR;
    
     /* parse arguments */
     int ctrl = _pam_parse(argc, argv);

     /* Get the username */
     retval = pam_get_user(pamh, (const char **)&username, NULL);
     if ((retval != PAM_SUCCESS) || (!username)) {
        if (ctrl & WINBIND_DEBUG_ARG)
            _pam_log(LOG_DEBUG,"can not get the username");
        return PAM_SERVICE_ERR;
     }
     
     retval = _winbind_read_password(pamh, ctrl, NULL, 
                             "Password: ", NULL,
                             &password);
     
     if (retval != PAM_SUCCESS) {
       _pam_log(LOG_ERR, "Could not retrive user's password");
       return PAM_AUTHTOK_ERR;
     }
     
     if (ctrl & WINBIND_DEBUG_ARG) {

           /* Let's not give too much away in the log file */

#ifdef DEBUG_PASSWORD
       _pam_log(LOG_INFO, "Verify user `%s' with password `%s'",
              username, password);
#else
       _pam_log(LOG_INFO, "Verify user `%s'", username);
#endif
     }

     /* Now use the username to look up password */
     return winbind_auth_request(username, password, ctrl);
}

PAM_EXTERN
int pam_sm_setcred(pam_handle_t *pamh, int flags,
               int argc, const char **argv)
{
    return PAM_SUCCESS;
}

/*
 * Account management. We want to verify that the account exists 
 * before returning PAM_SUCCESS
 */
PAM_EXTERN
int pam_sm_acct_mgmt(pam_handle_t *pamh, int flags,
               int argc, const char **argv)
{
    char *username;
    int retval = PAM_USER_UNKNOWN;

    /* parse arguments */
    int ctrl = _pam_parse(argc, argv);

    /* Get the username */
    retval = pam_get_user(pamh, (const char **)&username, NULL);
    if ((retval != PAM_SUCCESS) || (!username)) {
      if (ctrl & WINBIND_DEBUG_ARG)
          _pam_log(LOG_DEBUG,"can not get the username");
      return PAM_SERVICE_ERR;
    }

    /* Verify the username */
    retval = valid_user(username);
    switch (retval) {
      case -1:
          /* some sort of system error. The log was already printed */
          return PAM_SERVICE_ERR;
      case 1:
          /* the user does not exist */
          if (ctrl & WINBIND_DEBUG_ARG)
            _pam_log(LOG_NOTICE, "user `%s' not found",
                   username);
          if (ctrl & WINBIND_UNKNOWN_OK_ARG)
            return PAM_IGNORE;
          return PAM_USER_UNKNOWN;
      case 0:
          /* Otherwise, the authentication looked good */
          _pam_log(LOG_NOTICE, "user '%s' granted acces", username);
          return PAM_SUCCESS;
      default:
          /* we don't know anything about this return value */
          _pam_log(LOG_ERR, "internal module error (retval = %d, user = `%s'",
                 retval, username);
          return PAM_SERVICE_ERR;
    }
    
    /* should not be reached */
    return PAM_IGNORE;
}

PAM_EXTERN int pam_sm_open_session(pam_handle_t *pamh, int flags,
                            int argc, const char **argv)
{
      /* parse arguments */
      int ctrl = _pam_parse(argc, argv);
      if (ctrl & WINBIND_DEBUG_ARG)
            _pam_log(LOG_DEBUG,"libpam_winbind:pam_sm_open_session handler");
      return PAM_SUCCESS;
}

PAM_EXTERN int pam_sm_close_session(pam_handle_t *pamh, int flags,
                            int argc, const char **argv)
{
      /* parse arguments */
      int ctrl = _pam_parse(argc, argv);
      if (ctrl & WINBIND_DEBUG_ARG)
            _pam_log(LOG_DEBUG,"libpam_winbind:pam_sm_close_session handler");
      return PAM_SUCCESS;
}

PAM_EXTERN int pam_sm_chauthtok(pam_handle_t * pamh, int flags,
                        int argc, const char **argv)
{
      unsigned int lctrl;
      int retval;
      unsigned int ctrl = _pam_parse(argc, argv);

      /* <DO NOT free() THESE> */
      char *user;
      char *pass_old, *pass_new;
      /* </DO NOT free() THESE> */

      char *Announce;
      
      int retry = 0;

      /*
       * First get the name of a user
       */
      retval = pam_get_user(pamh, (const char **)&user, "Username: ");
      if (retval == PAM_SUCCESS) {
            if (user == NULL) {
                  _pam_log(LOG_ERR, "username was NULL!");
                  return PAM_USER_UNKNOWN;
            }
            if (retval == PAM_SUCCESS && on(WINBIND_DEBUG_ARG, ctrl))
                  _pam_log(LOG_DEBUG, "username [%s] obtained",
                         user);
      } else {
            if (on(WINBIND_DEBUG_ARG, ctrl))
                  _pam_log(LOG_DEBUG,
                         "password - could not identify user");
            return retval;
      }

      /*
       * obtain and verify the current password (OLDAUTHTOK) for
       * the user.
       */

      if (flags & PAM_PRELIM_CHECK) {
            
            /* instruct user what is happening */
#define greeting "Changing password for "
            Announce = (char *) malloc(sizeof(greeting) + strlen(user));
            if (Announce == NULL) {
            _pam_log(LOG_CRIT, 
                   "password - out of memory");
            return PAM_BUF_ERR;
            }
            (void) strcpy(Announce, greeting);
            (void) strcpy(Announce + sizeof(greeting) - 1, user);
#undef greeting
            
            lctrl = ctrl | WINBIND__OLD_PASSWORD;
            retval = _winbind_read_password(pamh, lctrl
                                    ,Announce
                                    ,"(current) NT password: "
                                    ,NULL
                                    ,&pass_old);
            free(Announce);
            
            if (retval != PAM_SUCCESS) {
                  _pam_log(LOG_NOTICE
                         ,"password - (old) token not obtained");
                  return retval;
            }
            /* verify that this is the password for this user */
            
            retval = winbind_auth_request(user, pass_old, ctrl);
            
            if (retval != PAM_ACCT_EXPIRED 
                && retval != PAM_NEW_AUTHTOK_REQD 
                && retval != PAM_SUCCESS) {
                  pass_old = NULL;
                  return retval;
            }
            
            retval = pam_set_item(pamh, PAM_OLDAUTHTOK, (const void *) pass_old);
            pass_old = NULL;
            if (retval != PAM_SUCCESS) {
                  _pam_log(LOG_CRIT, 
                         "failed to set PAM_OLDAUTHTOK");
            }
      } else if (flags & PAM_UPDATE_AUTHTOK) {
      
            /*
             * obtain the proposed password
             */
            
            /*
             * get the old token back. 
             */
            
            retval = pam_get_item(pamh, PAM_OLDAUTHTOK
                              ,(const void **) &pass_old);
            
            if (retval != PAM_SUCCESS) {
                  _pam_log(LOG_NOTICE, "user not authenticated");
                  return retval;
            }
            
            lctrl = ctrl;
            
            if (on(WINBIND_USE_AUTHTOK_ARG, lctrl)) {
                  ctrl = WINBIND_USE_FIRST_PASS_ARG | lctrl;
            }
            retry = 0;
            retval = PAM_AUTHTOK_ERR;
            while ((retval != PAM_SUCCESS) && (retry++ < MAX_PASSWD_TRIES)) {
                  /*
                   * use_authtok is to force the use of a previously entered
                   * password -- needed for pluggable password strength checking
                   */
                  
                  retval = _winbind_read_password(pamh, lctrl
                                          ,NULL
                                          ,"Enter new NT password: "
                                          ,"Retype new NT password: "
                                          ,&pass_new);
                  
                  if (retval != PAM_SUCCESS) {
                        if (on(WINBIND_DEBUG_ARG, ctrl)) {
                              _pam_log(LOG_ALERT
                                     ,"password - new password not obtained");
                        }
                        pass_old = NULL;/* tidy up */
                        return retval;
                  }

                  /*
                   * At this point we know who the user is and what they
                   * propose as their new password. Verify that the new
                   * password is acceptable.
                   */
                  
                  if (pass_new[0] == '\0') {/* "\0" password = NULL */
                        pass_new = NULL;
                  }
            }
            
            /*
             * By reaching here we have approved the passwords and must now
             * rebuild the password database file.
             */

            retval = winbind_chauthtok_request(user, pass_old, pass_new);
            _pam_overwrite(pass_new);
            _pam_overwrite(pass_old);
            pass_old = pass_new = NULL;
      } else {
            retval = PAM_SERVICE_ERR;
      }
      
      return retval;
}

#ifdef PAM_STATIC

/* static module data */

struct pam_module _pam_winbind_modstruct = {
     MODULE_NAME,
     pam_sm_authenticate,
     pam_sm_setcred,
     pam_sm_acct_mgmt,
     NULL,
     NULL,
     pam_sm_chauthtok
};

#endif

/*
 * Copyright (c) Andrew Tridgell  <tridge@samba.org>   2000
 * Copyright (c) Tim Potter       <tpot@samba.org>     2000
 * Copyright (c) Andrew Bartlettt <abartlet@samba.org> 2002
 * Copyright (c) Jan RÍkorajski 1999.
 * Copyright (c) Andrew G. Morgan 1996-8.
 * Copyright (c) Alex O. Yuriev, 1996.
 * Copyright (c) Cristian Gafton 1996.
 * Copyright (C) Elliot Lee <sopwith@redhat.com> 1996, Red Hat Software. 
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, and the entire permission notice in its entirety,
 *    including the disclaimer of warranties.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 *
 * ALTERNATIVELY, this product may be distributed under the terms of
 * the GNU Public License, in which case the provisions of the GPL are
 * required INSTEAD OF the above restrictions.  (This clause is
 * necessary due to a potential bad interaction between the GPL and
 * the restrictions contained in a BSD-style copyright.)
 *
 * THIS SOFTWARE IS PROVIDED `AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

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