# Copyright 1999-2021 Gentoo Authors # Distributed under the terms of the GNU General Public License v2 # @ECLASS: pax-utils.eclass # @MAINTAINER: # The Gentoo Linux Hardened Team <hardened@gentoo.org> # @AUTHOR: # Author: Kevin F. Quinn <kevquinn@gentoo.org> # Author: Anthony G. Basile <blueness@gentoo.org> # @SUPPORTED_EAPIS: 5 6 7 8 # @BLURB: functions to provide PaX markings for hardened kernels # @DESCRIPTION: # # 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. # Legacy PT_PAX markings no longer supported. # # To control what markings are made, set PAX_MARKINGS in /etc/portage/make.conf # to contain either "PT", "XT" or "none". The default is none case ${EAPI:-0} in 5|6|7|8) ;; *) die "${ECLASS}: EAPI ${EAPI:-0} not supported" ;; esac if [[ -z ${_PAX_UTILS_ECLASS} ]]; then _PAX_UTILS_ECLASS=1 # @ECLASS_VARIABLE: PAX_MARKINGS # @DESCRIPTION: # Control which markings are made: # PT = PT_PAX markings, XT = XATTR_PAX markings # Default to none markings. PAX_MARKINGS=${PAX_MARKINGS:="none"} # @FUNCTION: pax-mark # @USAGE: <flags> <ELF files> # @RETURN: Shell true if we succeed, shell false otherwise # @DESCRIPTION: # Marks <ELF files> with provided PaX <flags> # # Flags are passed directly to the utilities unchanged. # # @CODE # 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 # @CODE # # Default flags are 'PeMRS', which are the most restrictive settings. Refer # to https://pax.grsecurity.net/ 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@gentoo.org 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="${1//[!zPpEeMmRrSs]}" [[ "${flags}" ]] || return 0 shift # 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 "$@"; do # First try paxctl if type -p paxctl >/dev/null; then einfo "PT_PAX marking -${flags} ${f} with paxctl" # We try modifying the existing PT_PAX_FLAGS header. paxctl -q${flags} "${f}" >/dev/null 2>&1 && continue # We no longer try to create/convert a PT_PAX_FLAGS header, bug #590422 # paxctl -qC${flags} "${f}" >/dev/null 2>&1 && continue # paxctl -qc${flags} "${f}" >/dev/null 2>&1 && continue fi # Next try paxctl-ng -> this will not create/convert any program headers. if type -p paxctl-ng >/dev/null && paxctl-ng -L ; then einfo "PT_PAX marking -${flags} ${f} with paxctl-ng" flags="${flags//z}" [[ ${dodefault} == "yes" ]] && paxctl-ng -L -z "${f}" >/dev/null 2>&1 [[ "${flags}" ]] || continue paxctl-ng -L -${flags} "${f}" >/dev/null 2>&1 && continue fi # 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}." ret=1 fi done fi if has XT ${PAX_MARKINGS}; then # Uncomment to list all files to be marked # _pax_list_files einfo "$@" flags="${flags//z}" for f in "$@"; 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} "${f}" >/dev/null 2>&1 && continue fi # Next try setfattr. if type -p setfattr >/dev/null; then [[ "${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 fi # We failed to set XATTR_PAX flags. if [[ ${PAX_MARKINGS} != "none" ]]; then elog "Failed to set XATTR_PAX markings -${flags} ${f}." ret=1 fi done fi # [[ ${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 # @DESCRIPTION: # 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. # @EXAMPLE: # 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 # @DESCRIPTION: # 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 } # INTERNAL FUNCTIONS # ------------------ # # 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). # @FUNCTION: _pax_list_files # @INTERNAL # @USAGE: <command to display items> [items] # @DESCRIPTION: # Display a list of things, one per line, indented a bit, using the # display command in $1. _pax_list_files() { local f cmd cmd=$1 shift for f in "$@"; do ${cmd} " ${f}" done } fi