The following patch is aiming to improve & simplify ACL handling in copy-acl.c
Changes/Benefits:
* we no longer try to decode ACLs, instead we just copy the whole xattr with
ACLs
making the code simpler and faster
* side effect is support for NFSv4 acls
Disadvantages:
* it pulls in dependency on libattr. We still need dependency on libacl
because of set-acl.c which would have to be cared of separately. The
idea I have here is to confirm if it's safe to replace set_acl() with
chmod_or_fchmod() at least in Linux. It probably has something to do
with ACL inheritance.
Anyhow - with this patch copy_acl() does NOT honor inherited ACLs. It copies
ACLs to dest
file exactly - i.e. the same way the old code worked.
* we can't do any ACLs conversions, but these are not (AFAIK) being done anyway
in the
old code (the old code only worked with Posix)
The goal is for "cp -p" to preserve ACLs regardless of the type.
I tried to experiment with variety of filesystems (posix and nfs) and it seems
to me
to work exactly the way the old code worked (plus handy support for NFSv4).
Ondrej
---
lib/copy-acl.c | 31 ++++++++++++++++++++++++++++++-
m4/xattr.m4 | 43 +++++++++++++++++++++++++++++++++++++++++++
modules/acl | 1 +
3 files changed, 74 insertions(+), 1 deletion(-)
create mode 100644 m4/xattr.m4
diff --git a/lib/copy-acl.c b/lib/copy-acl.c
index 5fc42b7f6..341d1f605 100644
--- a/lib/copy-acl.c
+++ b/lib/copy-acl.c
@@ -29,6 +29,20 @@
#define _(msgid) gettext (msgid)
+#if USE_XATTR
+
+# include <attr/libattr.h>
+
+static int
+copy_attr_permissions (const char *name, struct error_context *ctx)
+{
+ int action = attr_copy_action (name, ctx);
+ return action == ATTR_ACTION_PERMISSIONS;
+}
+
+#endif /* USE_XATTR */
+
+
/* Copy access control lists from one file to another. If SOURCE_DESC is
a valid file descriptor, use file descriptor operations, else use
filename based operations on SRC_NAME. Likewise for DEST_DESC and
@@ -43,7 +57,22 @@ int
copy_acl (const char *src_name, int source_desc, const char *dst_name,
int dest_desc, mode_t mode)
{
- int ret = qcopy_acl (src_name, source_desc, dst_name, dest_desc, mode);
+ int ret;
+#ifdef USE_XATTR
+ ret = chmod_or_fchmod (dst_name, dest_desc, mode);
+ /* Rather than fiddling with acls one by one, we just copy the whole ACL
xattrs
+ * (Posix or NFSv4). Of course, that won't address ACLs conversion
+ * (i.e. posix <-> nfs4) but we can't do it anyway, so for now, we don't care
+ */
+ if(ret == 0)
+ ret = source_desc <= 0 && dest_desc <= 0
+ ? attr_copy_file (src_name, dst_name, copy_attr_permissions, NULL)
+ : attr_copy_fd (src_name, source_desc, dst_name, dest_desc,
copy_attr_permissions, NULL);
+#else
+ /* no XATTR, so we proceed the old dusty way */
+ ret = qcopy_acl (src_name, source_desc, dst_name, dest_desc, mode);
+#endif
+
switch (ret)
{
case -2:
diff --git a/m4/xattr.m4 b/m4/xattr.m4
new file mode 100644
index 000000000..5f9248939
--- /dev/null
+++ b/m4/xattr.m4
@@ -0,0 +1,43 @@
+# xattr.m4 - check for Extended Attributes (Linux)
+# serial 4
+
+# Copyright (C) 2003-2021 Free Software Foundation, Inc.
+# This file is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+# Originally written by Andreas Gruenbacher.
+
+AC_DEFUN([gl_FUNC_XATTR],
+[
+ AC_ARG_ENABLE([xattr],
+ AS_HELP_STRING([--disable-xattr],
+ [do not support extended attributes]),
+ [use_xattr=$enableval], [use_xattr=yes])
+
+ LIB_XATTR=
+ AC_SUBST([LIB_XATTR])
+
+ if test "$use_xattr" = "yes"; then
+ AC_CHECK_HEADERS([attr/error_context.h attr/libattr.h])
+ use_xattr=no
+ if test $ac_cv_header_attr_libattr_h = yes \
+ && test $ac_cv_header_attr_error_context_h = yes; then
+ xattr_saved_LIBS=$LIBS
+ AC_SEARCH_LIBS([attr_copy_file], [attr],
+ [test "$ac_cv_search_attr_copy_file" = "none required" ||
+ LIB_XATTR=$ac_cv_search_attr_copy_file])
+ AC_CHECK_FUNCS([attr_copy_file])
+ LIBS=$xattr_saved_LIBS
+ if test $ac_cv_func_attr_copy_file = yes; then
+ use_xattr=yes
+ fi
+ fi
+ if test $use_xattr = no; then
+ AC_MSG_WARN([libattr development library was not found or not usable.])
+ AC_MSG_WARN([AC_PACKAGE_NAME will be built without xattr support.])
+ fi
+ fi
+ AC_DEFINE_UNQUOTED([USE_XATTR], [`test $use_xattr != yes; echo $?`],
+ [Define if you want extended attribute support.])
+])
diff --git a/modules/acl b/modules/acl
index 1a3a14e6c..ca2239823 100644
--- a/modules/acl
+++ b/modules/acl
@@ -4,6 +4,7 @@ Access control lists of files, with diagnostics. (Unportable.)
Files:
lib/copy-acl.c
lib/set-acl.c
+m4/xattr.m4
Depends-on:
error
--
2.38.1
