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acl_check.c

/*
  File: acl_check.c

  Copyright (C) 1999, 2000
  Andreas Gruenbacher, <a.gruenbacher@computer.org>

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU Library General Public
  License as published by the Free Software Foundation; either
  version 2 of the License, or (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Library General Public License for more details.

  You should have received a copy of the GNU Library General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/

#include <stdio.h>
#include <errno.h>
#include <acl/libacl.h>
#include "libacl.h"


#define FAIL_CHECK(error) \
      do { return error; } while (0)

/*
  Check if an ACL is valid.

  The e_id fields of ACL entries that don't use them are ignored.

  last
      contains the index of the last valid entry found
      after acl_check returns.
  returns
      0 on success, -1 on error, or an ACL_*_ERROR value for invalid ACLs.
*/

int
acl_check(acl_t acl, int *last)
{
      acl_obj *acl_obj_p = ext2int(acl, acl);
      id_t qual = 0;
      int state = ACL_USER_OBJ;
      acl_entry_obj *entry_obj_p;
      int needs_mask = 0;

      if (!acl_obj_p)
            return -1;
      if (last)
            *last = 0;
      FOREACH_ACL_ENTRY(entry_obj_p, acl_obj_p) {
            /* Check permissions for ~(ACL_READ|ACL_WRITE|ACL_EXECUTE) */
            switch (entry_obj_p->etag) {
                  case ACL_USER_OBJ:
                        if (state == ACL_USER_OBJ) {
                              qual = 0;
                              state = ACL_USER;
                              break;
                        }
                        FAIL_CHECK(ACL_MULTI_ERROR);

                  case ACL_USER:
                        if (state != ACL_USER)
                              FAIL_CHECK(ACL_MISS_ERROR);
                        if (qualifier_obj_id(entry_obj_p->eid) < qual ||
                            qualifier_obj_id(entry_obj_p->eid) ==
                            ACL_UNDEFINED_ID)
                              FAIL_CHECK(ACL_DUPLICATE_ERROR);
                        qual = qualifier_obj_id(entry_obj_p->eid)+1;
                        needs_mask = 1;
                        break;

                  case ACL_GROUP_OBJ:
                        if (state == ACL_USER) {
                              qual = 0;
                              state = ACL_GROUP;
                              break;
                        }
                        if (state >= ACL_GROUP)
                              FAIL_CHECK(ACL_MULTI_ERROR);
                        FAIL_CHECK(ACL_MISS_ERROR);

                  case ACL_GROUP:
                        if (state != ACL_GROUP)
                              FAIL_CHECK(ACL_MISS_ERROR);
                        if (qualifier_obj_id(entry_obj_p->eid) < qual ||
                            qualifier_obj_id(entry_obj_p->eid) ==
                            ACL_UNDEFINED_ID)
                              FAIL_CHECK(ACL_DUPLICATE_ERROR);
                        qual = qualifier_obj_id(entry_obj_p->eid)+1;
                        needs_mask = 1;
                        break;

                  case ACL_MASK:
                        if (state == ACL_GROUP) {
                              state = ACL_OTHER;
                              break;
                        }
                        if (state >= ACL_OTHER)
                              FAIL_CHECK(ACL_MULTI_ERROR);
                        FAIL_CHECK(ACL_MISS_ERROR);

                  case ACL_OTHER:
                        if (state == ACL_OTHER ||
                            (state == ACL_GROUP && !needs_mask)) {
                              state = 0;
                              break;
                        }
                        FAIL_CHECK(ACL_MISS_ERROR);

                  default:
                        FAIL_CHECK(ACL_ENTRY_ERROR);
            }
            if (last)
                  (*last)++;
      }

      if (state != 0)
            FAIL_CHECK(ACL_MISS_ERROR);
      return 0;
}
#undef FAIL_CHECK


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