[patch] Proposed eclass.

pax-utils.eclass (text/plain), 7.72 KB, created by Anthony Basile on 2013-02-10 01:46:01 UTC

# Copyright 1999-2012 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2
# $Header: /var/cvsroot/gentoo-x86/eclass/pax-utils.eclass,v 1.18 2012/04/06 18:03:54 blueness Exp $

# @ECLASS: pax-utils.eclass
# @MAINTAINER:
# The Gentoo Linux Hardened Team <[e-mail]>
# @AUTHOR:
# Original Author: Kevin F. Quinn <[e-mail]>
# Modifications for bug #365825, @ ECLASS markup: Anthony G. Basile <[e-mail]>
# Modifications for bug #431092: Anthony G. Basile <[e-mail]>
# @BLURB: functions to provide pax markings
# @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.
#
# 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
# PT_PAX and XATTR_PAX.

if [[ ${___ECLASS_ONCE_PAX_UTILS} != "recur -_+^+_- spank" ]] ; then
___ECLASS_ONCE_PAX_UTILS="recur -_+^+_- spank"

# Default to PT markings.
PAX_MARKINGS=${PAX_MARKINGS:="PT XT"}

# @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
#
#	p: disable PAGEEXEC		P: enable PAGEEXEC
#	e: disable EMUTRMAP		E: enable EMUTRMAP
#	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 http://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@g.o on
# the bug report.



# Sanitize out all but the actual pax flags and z 
#
# 1. The leading '-' is irrelevant since it is santized out
#
# 2. Cc only make sense for paxctl, and even there these are
#    not needed as we progressively try:
#        paxctl -q${flags}
#        paxctl -qc${flags}
#        paxctl -qC${flags}
#    So we sanitize them out.
#
# 3. z is allowed for the default
#
sanitize-flags() {


        local flags="$1"
        local clean=""

        [[ "${flags}" != "${flags/z/}" ]] && clean="${clean}z"

        [[ "${flags}" != "${flags/P/}" ]] && clean="${clean}P"
        [[ "${flags}" != "${flags/p/}" ]] && clean="${clean}p"
        [[ "${flags}" != "${flags/E/}" ]] && clean="${clean}E"
        [[ "${flags}" != "${flags/e/}" ]] && clean="${clean}e"
        [[ "${flags}" != "${flags/M/}" ]] && clean="${clean}M"
        [[ "${flags}" != "${flags/m/}" ]] && clean="${clean}m"
        [[ "${flags}" != "${flags/R/}" ]] && clean="${clean}R"
        [[ "${flags}" != "${flags/r/}" ]] && clean="${clean}r"
        [[ "${flags}" != "${flags/S/}" ]] && clean="${clean}S"
        [[ "${flags}" != "${flags/s/}" ]] && clean="${clean}s"

        echo "$clean"
}


pax-mark() {

	local f								# loop over paxables
	local flags							# pax flags
	local pt_fail=0 pt_failures=""		# record PT_PAX failures
	local xt_fail=0 xt_failures=""		# record xattr PAX marking failures
	local ret=0							# overal return code of this function

	flags="$(sanitize-flags $1)"
	shift

	if has PT ${PAX_MARKINGS}; then

		#First try paxctl -> this might try to create/convert program headers
		if type -p paxctl > /dev/null; then
			einfo "PT PaX marking -${flags} with paxctl"
			_pax_list_files einfo "$@"
			for f in "$@"; do
				# First, try modifying the existing PAX_FLAGS header
				paxctl -q${flags} "${f}" && continue
				# Second, try stealing the (unused under PaX) PT_GNU_STACK header
				paxctl -qc${flags} "${f}" && continue
				# Third, creating a PT_PAX header (works on ET_EXEC)
				paxctl -qC${flags} "${f}" && continue
				pt_fail=1
				pt_failures="${pt_failures} ${f}"
			done

		#Next try paxctl-ng -> this will not create/convert any program headers
		elif type -p paxctl-ng > /dev/null && paxctl-ng -L ; then
			einfo "PT PaX marking -${flags} with paxctl-ng"
			_pax_list_files einfo "$@"
			for f in "$@"; do
				paxctl-ng -L -${flags} "${f}" && continue
				pt_fail=1
				pt_failures="${pt_failures} ${f}"
			done

		#Finally fall back on scanelf
		elif type -p scanelf > /dev/null && [[ ${PAX_MARKINGS} != "none" ]]; then
			einfo "Fallback PaX marking -${flags} with scanelf"
			_pax_list_files einfo "$@"
			scanelf -Xxz ${flags} "$@"

		#We failed to set PT_PAX flags
		elif [[ ${PAX_MARKINGS} != "none" ]]; then
			pt_failures="$*"
			pt_fail=1
		fi

		if [[ ${pt_fail} == 1 ]]; then
			ewarn "Failed to set XT_PAX markings -${flags} for:"
			_pax_list_files ewarn ${pt_failures}
			ret=1
		fi
	fi

	if has XT ${PAX_MARKINGS}; then

		# z = default. For XATTR_PAX, the default is no xattr field at all
		local dodefault=""
		if [[ "${flags}" != "${flags/z/}" ]]; then
			flags="${flags/z/}"
			dodefault="yes"
		fi

		#First try paxctl-ng
		if type -p paxctl-ng > /dev/null && paxctl-ng -l ; then
			einfo "XT PaX marking -${flags} with paxctl-ng"
			_pax_list_files einfo "$@"
			for f in "$@"; do
				[[ ${dodefault} == "yes" ]] && paxctl-ng -d "${f}"
				paxctl-ng -l -${flags} "${f}" && continue
				xt_fail=1
				xt_failures="${tx_failures} ${f}"
			done

		#Next try setfattr
		elif type -p setfattr > /dev/null; then
			einfo "XT PaX marking -${flags} with setfattr"
			_pax_list_files einfo "$@"
			for f in "$@"; do
				[[ ${dodefault} == "yes" ]] && setfattr -x "user.pax.flags" "${f}"
				setfattr -n "user.pax.flags" -v "${flags}" "${f}" && continue
				xt_fail=1
				xt_failures="${tx_failures} ${f}"
			done

		#We failed to set PT_PAX flags
		elif [[ ${PAX_MARKINGS} != "none" ]]; then
			pt_failures="$*"
			pt_fail=1
		fi

		if [[ ${xt_fail} == 1 ]]; then
			ewarn "Failed to set XT_PAX markings -${flags} for:"
			_pax_list_files ewarn ${xt_failures}
			ret=1
		fi
	fi

	[[ ${ret} == 1 ]] && ewarn "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 intedened to
# determine whether the final binaries need PaX markings.  Note: if procfs is
# not mounted on /proc, this returns shell false (e.g. Gentoo/FBSD).
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 arbitratily).

# 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