lib/qcopy-acl.c

   1 /* Copy access control list from one file to another.  -*- coding: utf-8 -*-
   2
   3    Copyright (C) 2002-2003, 2005-2024 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation, either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.
  17
  18    Written by Paul Eggert, Andreas Grünbacher, and Bruno Haible.  */
  19
  20 #include <config.h>
  21
  22 #include "acl.h"
  23
  24 #include "acl-internal.h"
  25
  26 #if USE_XATTR
  27
  28 # include <attr/libattr.h>
  29
  30 /* Returns 1 if NAME is the name of an extended attribute that is related
  31    to permissions, i.e. ACLs.  Returns 0 otherwise.  */
  32
  33 static int
  34 is_attr_permissions (const char *name, struct error_context *ctx)
  35 {
  36   return attr_copy_action (name, ctx) == ATTR_ACTION_PERMISSIONS;
  37 }
  38
  39 #endif  /* USE_XATTR */
  40
  41 /* Copy access control lists from one file to another. If SOURCE_DESC is
  42    a valid file descriptor, use file descriptor operations, else use
  43    filename based operations on SRC_NAME. Likewise for DEST_DESC and
  44    DST_NAME.
  45    If access control lists are not available, fchmod the target file to
  46    MODE.  Also sets the non-permission bits of the destination file
  47    (S_ISUID, S_ISGID, S_ISVTX) to those from MODE if any are set.
  48    Return 0 if successful.
  49    Return -2 and set errno for an error relating to the source file.
  50    Return -1 and set errno for an error relating to the destination file.  */
  51
  52 int
  53 qcopy_acl (const char *src_name, int source_desc, const char *dst_name,
  54            int dest_desc, mode_t mode)
  55 {
  56   int ret;
  57
  58 #ifdef USE_XATTR
  59   /* in case no ACLs present and also to set higher mode bits
  60      we chmod before setting ACLs as doing it after could overwrite them
  61      (especially true for NFSv4, posix ACL has that ugly "mask" hack that
  62      nobody understands) */
  63   ret = chmod_or_fchmod (dst_name, dest_desc, mode);
  64   /* Rather than fiddling with acls one by one, we just copy the whole ACL xattrs
  65      (Posix or NFSv4). Of course, that won't address ACLs conversion
  66      (i.e. posix <-> nfs4) but we can't do it anyway, so for now, we don't care
  67      Functions attr_copy_* return 0 in case we copied something OR nothing
  68      to copy */
  69   if (ret == 0)
  70     ret = source_desc <= 0 || dest_desc <= 0
  71       ? attr_copy_file (src_name, dst_name, is_attr_permissions, NULL)
  72       : attr_copy_fd (src_name, source_desc, dst_name, dest_desc,
  73                       is_attr_permissions, NULL);
  74 #else
  75   /* no XATTR, so we proceed the old dusty way */
  76   struct permission_context ctx;
  77
  78   ret = get_permissions (src_name, source_desc, mode, &ctx);
  79   if (ret != 0)
  80     return -2;
  81   ret = set_permissions (&ctx, dst_name, dest_desc);
  82   free_permission_context (&ctx);
  83 #endif
  84   return ret;
  85 }