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# 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 1.12 2011/07/02 17:03:51 blueness Exp $ |
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# @ECLASS: pax-utils.eclass |
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# @MAINTAINER: |
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# Maintained by |
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# The Gentoo Linux Hardened Team <hardened@gentoo.org> |
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# Original Author |
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# Kevin F. Quinn <kevquinn@gentoo.org> |
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# Modifications for bug #365825, @ ECLASS markup |
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# 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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|
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inherit eutils |
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|
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# Default to PT markings. |
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PAX_MARKINGS=${PAX_MARKINGS:="PT"} |
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|
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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 && hasq PT ${PAX_MARKINGS}; then |
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# Try paxctl, the upstream supported tool. |
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elog "PT PaX marking -${flags}" |
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_pax_list_files elog "$@" |
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for f in "$@"; 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 && [[ ${PAX_MARKINGS} != "none" ]]; then |
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# Try scanelf, the Gentoo swiss-army knife ELF utility |
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# Currently this sets PT if it can, no option to control what it does. |
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elog "Fallback PaX marking -${flags}" |
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_pax_list_files elog "$@" |
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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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|
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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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|
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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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|
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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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|
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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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