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# Copyright 1999-2015 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2
# $Id$
# @ECLASS: pax-utils.eclass
# The Gentoo Linux Hardened Team <>
# Original Author: Kevin F. Quinn <>
# Modifications for bugs #365825, #431092, #520198, @ ECLASS markup: Anthony G. Basile <>
# @BLURB: functions to provide PaX markings for hardened kernels
# This eclass provides support for manipulating PaX markings on ELF binaries,
# whether the system is using legacy PT_PAX markings or the newer XATTR_PAX.
# The eclass wraps the use of paxctl-ng, paxctl, set/getattr and scanelf utilities,
# deciding which to use depending on what's installed on the build host, and
# whether we're working with PT_PAX, XATTR_PAX or both.
# To control what markings are made, set PAX_MARKINGS in /etc/portage/make.conf
# to contain either "PT", "XT" or "none". The default is to attempt both
if [[ -z ${_PAX_UTILS_ECLASS} ]]; then
# Control which markings are made:
# PT = PT_PAX markings, XT = XATTR_PAX markings
# Default to PT markings.
# @FUNCTION: pax-mark
# @USAGE: <flags> <ELF files>
# @RETURN: Shell true if we succeed, shell false otherwise
# Marks <ELF files> with provided PaX <flags>
# Flags are passed directly to the utilities unchanged.
# p: disable PAGEEXEC P: enable PAGEEXEC
# e: disable EMUTRAMP E: enable EMUTRAMP
# m: disable MPROTECT M: enable MPROTECT
# r: disable RANDMMAP R: enable RANDMMAP
# s: disable SEGMEXEC S: enable SEGMEXEC
# Default flags are 'PeMRS', which are the most restrictive settings. Refer
# to for details on what these flags are all about.
# Please confirm any relaxation of restrictions with the Gentoo Hardened team.
# Either ask on the gentoo-hardened mailing list, or CC/assign hardened@g.o on
# the bug report.
pax-mark() {
local f # loop over paxables
local flags # pax flags
local ret=0 # overall return code of this function
# Only the actual PaX flags and z are accepted
# 1. The leading '-' is optional
# 2. -C -c only make sense for paxctl, but are unnecessary
# because we progressively do -q -qc -qC
# 3. z is allowed for the default
[[ "${flags}" ]] || return 0
# z = default. For XATTR_PAX, the default is no xattr field at all
local dodefault=""
[[ "${flags//[!z]}" ]] && dodefault="yes"
if has PT ${PAX_MARKINGS}; then
# Uncomment to list all files to be marked
# _pax_list_files einfo "$@"
for f in "$@"; do
# First try paxctl -> this might try to create/convert program headers.
if type -p paxctl >/dev/null; then
einfo "PT_PAX marking -${flags} ${f} with paxctl"
# First, try modifying the existing PAX_FLAGS header.
paxctl -q${flags} "${f}" >/dev/null 2>&1 && continue
# Second, try creating a PT_PAX header (works on ET_EXEC).
# Even though this is less safe, most exes need it. #463170
paxctl -qC${flags} "${f}" >/dev/null 2>&1 && continue
# Third, try stealing the (unused under PaX) PT_GNU_STACK header
paxctl -qc${flags} "${f}" >/dev/null 2>&1 && continue
# Next try paxctl-ng -> this will not create/convert any program headers.
if type -p paxctl-ng >/dev/null && paxctl-ng -L ; then
einfo "PT_PAX marking -${flags} ${f} with paxctl-ng"
[[ ${dodefault} == "yes" ]] && paxctl-ng -L -z "${f}" >/dev/null 2>&1
[[ "${flags}" ]] || continue
paxctl-ng -L -${flags} "${f}" >/dev/null 2>&1 && continue
# Finally fall back on scanelf.
if type -p scanelf >/dev/null && [[ ${PAX_MARKINGS} != "none" ]]; then
einfo "PT_PAX marking -${flags} ${f} with scanelf"
scanelf -Xxz ${flags} "$f" >/dev/null 2>&1
# We failed to set PT_PAX flags.
elif [[ ${PAX_MARKINGS} != "none" ]]; then
elog "Failed to set PT_PAX markings -${flags} ${f}."
if has XT ${PAX_MARKINGS}; then
# Uncomment to list all files to be marked
# _pax_list_files einfo "$@"
for f in "$@"; do
# First try paxctl-ng.
if type -p paxctl-ng >/dev/null && paxctl-ng -l ; then
einfo "XATTR_PAX marking -${flags} ${f} with paxctl-ng"
[[ ${dodefault} == "yes" ]] && paxctl-ng -d "${f}" >/dev/null 2>&1
[[ "${flags}" ]] || continue
paxctl-ng -l -${flags} "${f}" >/dev/null 2>&1 && continue
# Next try setfattr.
if type -p setfattr >/dev/null; then
[[ "${flags//[!Ee]}" ]] || flags+="e" # bug 447150
einfo "XATTR_PAX marking -${flags} ${f} with setfattr"
[[ ${dodefault} == "yes" ]] && setfattr -x "user.pax.flags" "${f}" >/dev/null 2>&1
setfattr -n "user.pax.flags" -v "${flags}" "${f}" >/dev/null 2>&1 && continue
# We failed to set XATTR_PAX flags.
if [[ ${PAX_MARKINGS} != "none" ]]; then
elog "Failed to set XATTR_PAX markings -${flags} ${f}."
# [[ ${ret} == 1 ]] && elog "Executables may be killed by PaX kernels."
return ${ret}
# @FUNCTION: list-paxables
# @USAGE: <files>
# @RETURN: Subset of <files> which are ELF executables or shared objects
# Print to stdout all of the <files> that are suitable to have PaX flag
# markings, i.e., filter out the ELF executables or shared objects from a list
# of files. This is useful for passing wild-card lists to pax-mark, although
# in general it is preferable for ebuilds to list precisely which ELFS are to
# be marked. Often not all the ELF installed by a package need remarking.
# pax-mark -m $(list-paxables ${S}/{,usr/}bin/*)
list-paxables() {
file "$@" 2> /dev/null | grep -E 'ELF.*(executable|shared object)' | sed -e 's/: .*$//'
# @FUNCTION: host-is-pax
# @RETURN: Shell true if the build process is PaX enabled, shell false otherwise
# This is intended for use where the build process must be modified conditionally
# depending on whether the host is PaX enabled or not. It is not indented to
# determine whether the final binaries need PaX markings. Note: if procfs is
# not mounted on /proc, this returns shell false (e.g. Gentoo/FreeBSD).
host-is-pax() {
grep -qs ^PaX: /proc/self/status
# ------------------
# These functions are for use internally by the eclass - do not use
# them elsewhere as they are not supported (i.e. they may be removed
# or their function may change arbitrarily).
# Display a list of things, one per line, indented a bit, using the
# display command in $1.
_pax_list_files() {
local f cmd
for f in "$@"; do
${cmd} " ${f}"