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file-has-acl: improve port to Fedora 39

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Problem reported by Ondrej Valousek in:
https://lists.gnu.org/r/bug-gnulib/2023-05/msg00078.html
* lib/file-has-acl.c: Include minmax.h.
[USE_ACL && HAVE_LINUX_XATTR_H && HAVE_LISTXATTR]: Include stdckdint.h.
(file_has_acl) [USE_ACL && HAVE_LINUX_XATTR_H && HAVE_LISTXATTR]:
If the file has NFSv4 ACLs, ignore any POSIX ACLs, for Fedora 39.
Return a bit faster when listxattr returns 0.
Don’t loop forever if an attacker is fiddling with ACLs.
* modules/file-has-acl (Depends-on): Add minmax, stdckdint.
This commit is contained in:
Paul Eggert
2023-05-15 08:40:27 -07:00
parent 29f9d848e5
commit 7357169317
3 changed files with 41 additions and 11 deletions
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13
ChangeLog
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@@ -1,3 +1,16 @@
2023-05-15 Paul Eggert <eggert@cs.ucla.edu>
file-has-acl: improve port to Fedora 39
Problem reported by Ondrej Valousek in:
https://lists.gnu.org/r/bug-gnulib/2023-05/msg00078.html
* lib/file-has-acl.c: Include minmax.h.
[USE_ACL && HAVE_LINUX_XATTR_H && HAVE_LISTXATTR]: Include stdckdint.h.
(file_has_acl) [USE_ACL && HAVE_LINUX_XATTR_H && HAVE_LISTXATTR]:
If the file has NFSv4 ACLs, ignore any POSIX ACLs, for Fedora 39.
Return a bit faster when listxattr returns 0.
Don’t loop forever if an attacker is fiddling with ACLs.
* modules/file-has-acl (Depends-on): Add minmax, stdckdint.
2023-05-15 Bruno Haible <bruno@clisp.org>
Work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82283 .

37
lib/file-has-acl.c
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@@ -29,7 +29,10 @@
#include "acl-internal.h"
#include "minmax.h"
#if USE_ACL && HAVE_LINUX_XATTR_H && HAVE_LISTXATTR
# include <stdckdint.h>
# include <string.h>
# include <arpa/inet.h>
# include <sys/xattr.h>
@@ -181,32 +184,44 @@ file_has_acl (char const *name, struct stat const *sb)
&& errno == ERANGE)
{
free (heapbuf);
listbufsize = listxattr (name, NULL, 0);
if (listbufsize < 0)
return -1;
if (SIZE_MAX < listbufsize)
ssize_t newsize = listxattr (name, NULL, 0);
if (newsize <= 0)
return newsize;
/* Grow LISTBUFSIZE to at least NEWSIZE. Grow it by a
nontrivial amount too, to defend against denial of
service by an adversary that fiddles with ACLs. */
bool overflow = ckd_add (&listbufsize, listbufsize, listbufsize >> 1);
listbufsize = MAX (listbufsize, newsize);
if (overflow || SIZE_MAX < listbufsize)
{
errno = ENOMEM;
return -1;
}
listbuf = heapbuf = malloc (listbufsize);
if (!listbuf)
return -1;
}
/* In Fedora 39, a file can have both NFSv4 and POSIX ACLs,
but if it has an NFSv4 ACL that's the one that matters.
In earlier Fedora the two types of ACLs were mutually exclusive.
Attempt to work correctly on both kinds of systems. */
bool nfsv4_acl
= 0 < listsize && have_xattr (XATTR_NAME_NFSV4_ACL, listbuf, listsize);
int ret
= (listsize < 0 ? -1
: (have_xattr (XATTR_NAME_POSIX_ACL_ACCESS, listbuf, listsize)
= (listsize <= 0 ? listsize
: (nfsv4_acl
|| have_xattr (XATTR_NAME_POSIX_ACL_ACCESS, listbuf, listsize)
|| (S_ISDIR (sb->st_mode)
&& have_xattr (XATTR_NAME_POSIX_ACL_DEFAULT,
listbuf, listsize))));
bool nfsv4_acl_but_no_posix_acl
= ret == 0 && have_xattr (XATTR_NAME_NFSV4_ACL, listbuf, listsize);
free (heapbuf);
/* If there is an NFSv4 ACL but no POSIX ACL, follow up with a
getxattr syscall to see whether the NFSv4 ACL is nontrivial. */
if (nfsv4_acl_but_no_posix_acl)
/* If there is an NFSv4 ACL, follow up with a getxattr syscall
to see whether the NFSv4 ACL is nontrivial. */
if (nfsv4_acl)
{
ret = getxattr (name, XATTR_NAME_NFSV4_ACL,
stackbuf.xattr, sizeof stackbuf.xattr);

2
modules/file-has-acl
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@@ -9,9 +9,11 @@ m4/acl.m4
Depends-on:
acl-permissions
extern-inline
minmax
free-posix
stat
stdbool
stdckdint
configure.ac:
gl_FILE_HAS_ACL