155 lines
6 KiB
Bash
155 lines
6 KiB
Bash
# Copyright 1999-2011 Gentoo Foundation
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# Distributed under the terms of the GNU General Public License v2
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# $Header: /var/cvsroot/gentoo-x86/eclass/pax-utils.eclass,v 1.18 2012/04/06 18:03:54 blueness Exp $
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# @ECLASS: pax-utils.eclass
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# @MAINTAINER:
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# The Gentoo Linux Hardened Team <hardened@gentoo.org>
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# @AUTHOR:
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# Original Author: Kevin F. Quinn <kevquinn@gentoo.org>
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# Modifications for bug #365825, @ ECLASS markup: Anthony G. Basile <blueness@gentoo.org>
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# @BLURB: functions to provide pax markings
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# @DESCRIPTION:
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# This eclass provides support for manipulating PaX markings on ELF binaries,
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# wrapping the use of the paxctl and scanelf utilities. It decides which to
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# use depending on what is installed on the build host, preferring paxctl to
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# scanelf. If paxctl is not installed, we fall back to scanelf since it is
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# always present. However, currently scanelf doesn't do all that paxctl can.
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#
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# To control what markings are made, set PAX_MARKINGS in /etc/make.conf to
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# contain either "PT" or "none". If PAX_MARKINGS is set to "PT", and the
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# necessary utility is installed, the PT_PAX_FLAGS markings will be made. If
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# PAX_MARKINGS is set to "none", no markings will be made.
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if [[ ${___ECLASS_ONCE_PAX_UTILS} != "recur -_+^+_- spank" ]] ; then
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___ECLASS_ONCE_PAX_UTILS="recur -_+^+_- spank"
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# Default to PT markings.
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PAX_MARKINGS=${PAX_MARKINGS:="PT"}
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# @FUNCTION: pax-mark
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# @USAGE: <flags> {<ELF files>}
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# @RETURN: Shell true if we succeed, shell false otherwise
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# @DESCRIPTION:
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# Marks <ELF files> with provided PaX <flags>
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#
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# Flags are passed directly to the utilities unchanged. Possible flags at the
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# time of writing, taken from /sbin/paxctl, are:
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#
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# p: disable PAGEEXEC P: enable PAGEEXEC
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# e: disable EMUTRMAP E: enable EMUTRMAP
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# m: disable MPROTECT M: enable MPROTECT
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# r: disable RANDMMAP R: enable RANDMMAP
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# s: disable SEGMEXEC S: enable SEGMEXEC
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#
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# Default flags are 'PeMRS', which are the most restrictive settings. Refer
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# to http://pax.grsecurity.net/ for details on what these flags are all about.
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# Do not use the obsolete flag 'x'/'X' which has been deprecated.
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#
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# Please confirm any relaxation of restrictions with the Gentoo Hardened team.
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# Either ask on the gentoo-hardened mailing list, or CC/assign hardened@g.o on
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# the bug report.
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pax-mark() {
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local f flags fail=0 failures="" zero_load_alignment
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# Ignore '-' characters - in particular so that it doesn't matter if
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# the caller prefixes with -
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flags=${1//-}
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shift
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# Try paxctl, then scanelf. paxctl is preferred.
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if type -p paxctl > /dev/null && has PT ${PAX_MARKINGS}; then
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# Try paxctl, the upstream supported tool.
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einfo "PT PaX marking -${flags}"
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_pax_list_files einfo "$@"
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for f in "$@"; do
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# First, try modifying the existing PAX_FLAGS header
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paxctl -q${flags} "${f}" && continue
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# Second, try stealing the (unused under PaX) PT_GNU_STACK header
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paxctl -qc${flags} "${f}" && continue
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# Third, try pulling the base down a page, to create space and
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# insert a PT_GNU_STACK header (works on ET_EXEC)
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paxctl -qC${flags} "${f}" && continue
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#
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# prelink is masked on hardened so we wont use this method.
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# We're working on a new utiity to try to do the same safely. See
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# http://git.overlays.gentoo.org/gitweb/?p=proj/elfix.git;a=summary
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#
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# Fourth - check if it loads to 0 (probably an ET_DYN) and if so,
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# try rebasing with prelink first to give paxctl some space to
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# grow downwards into.
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#if type -p objdump > /dev/null && type -p prelink > /dev/null; then
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# zero_load_alignment=$(objdump -p "${f}" | \
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# grep -E '^[[:space:]]*LOAD[[:space:]]*off[[:space:]]*0x0+[[:space:]]' | \
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# sed -e 's/.*align\(.*\)/\1/')
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# if [[ ${zero_load_alignment} != "" ]]; then
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# prelink -r $(( 2*(${zero_load_alignment}) )) &&
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# paxctl -qC${flags} "${f}" && continue
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# fi
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#fi
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fail=1
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failures="${failures} ${f}"
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done
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elif type -p scanelf > /dev/null && [[ ${PAX_MARKINGS} != "none" ]]; then
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# Try scanelf, the Gentoo swiss-army knife ELF utility
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# Currently this sets PT if it can, no option to control what it does.
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einfo "Fallback PaX marking -${flags}"
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_pax_list_files einfo "$@"
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scanelf -Xxz ${flags} "$@"
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elif [[ ${PAX_MARKINGS} != "none" ]]; then
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# Out of options!
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failures="$*"
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fail=1
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fi
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if [[ ${fail} == 1 ]]; then
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ewarn "Failed to set PaX markings -${flags} for:"
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_pax_list_files ewarn ${failures}
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ewarn "Executables may be killed by PaX kernels."
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fi
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return ${fail}
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}
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# @FUNCTION: list-paxables
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# @USAGE: {<files>}
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# @RETURN: Subset of {<files>} which are ELF executables or shared objects
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# @DESCRIPTION:
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# Print to stdout all of the <files> that are suitable to have PaX flag
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# markings, i.e., filter out the ELF executables or shared objects from a list
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# of files. This is useful for passing wild-card lists to pax-mark, although
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# in general it is preferable for ebuilds to list precisely which ELFS are to
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# be marked. Often not all the ELF installed by a package need remarking.
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# @EXAMPLE:
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# pax-mark -m $(list-paxables ${S}/{,usr/}bin/*)
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list-paxables() {
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file "$@" 2> /dev/null | grep -E 'ELF.*(executable|shared object)' | sed -e 's/: .*$//'
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}
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# @FUNCTION: host-is-pax
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# @RETURN: Shell true if the build process is PaX enabled, shell false otherwise
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# @DESCRIPTION:
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# This is intended for use where the build process must be modified conditionally
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# depending on whether the host is PaX enabled or not. It is not intedened to
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# determine whether the final binaries need PaX markings. Note: if procfs is
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# not mounted on /proc, this returns shell false (e.g. Gentoo/FBSD).
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host-is-pax() {
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grep -qs ^PaX: /proc/self/status
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}
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# INTERNAL FUNCTIONS
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# ------------------
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#
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# These functions are for use internally by the eclass - do not use
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# them elsewhere as they are not supported (i.e. they may be removed
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# or their function may change arbitratily).
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# Display a list of things, one per line, indented a bit, using the
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# display command in $1.
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_pax_list_files() {
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local f cmd
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cmd=$1
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shift
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for f in "$@"; do
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${cmd} " ${f}"
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done
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}
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fi
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