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1# Copyright 1999-2006 Gentoo Foundation 1# Copyright 1999-2006 Gentoo Foundation
2# Distributed under the terms of the GNU General Public License v2 2# Distributed under the terms of the GNU General Public License v2
3# $Header: /var/cvsroot/gentoo-x86/eclass/pax-utils.eclass,v 1.3 2006/11/24 15:11:55 kevquinn Exp $ 3# $Header: /var/cvsroot/gentoo-x86/eclass/pax-utils.eclass,v 1.7 2007/05/07 09:24:16 kevquinn Exp $
4 4
5# Author: 5# Author:
6# Kevin F. Quinn <kevquinn@gentoo.org> 6# Kevin F. Quinn <kevquinn@gentoo.org>
7# 7#
8# This eclass provides support for manipulating PaX markings on ELF 8# This eclass provides support for manipulating PaX markings on ELF
9# binaries, wrapping the use of the chpax and paxctl utilities. 9# binaries, wrapping the use of the chpaxi, paxctl and scanelf utilities.
10# Currently it decides which to use depending on what is installed on the
11# build host; this may change in the future to use a control variable
12# (which would also mean modifying DEPEND to bring in sys-apps/paxctl etc).
13#
14#
15# CONTROL
16# -------
17#
18# To control what markings are set, assign PAX_MARKINGS in
19# /etc/make.conf to contain the strings "EI" and/or "PT".
20# If EI is present in PAX_MARKINGS (and the chpax utility
21# is present), the legacy 'chpax' style markings will be
22# set. If PT is present in PAX_MARKINGS (and the paxctl
23# utility is present), the 'paxctl' markings will be set.
24# Default is to try to do both. Set it to "NONE" to prevent
25# any markings being made.
26#
27#
28# PROVIDED FUNCTIONS
29# ------------------
30#
31#### pax-mark <flags> {<ELF files>}
32# Marks files <files> with provided PaX flags <flags>
33#
34# Please confirm any relaxation of restrictions with the
35# Gentoo Hardened team; either ask on the gentoo-hardened
36# mailing list, or CC/assign hardened@g.o on a bug.
37#
38# Flags are passed directly to the utilities unchanged. Possible
39# flags at the time of writing, taken from /sbin/paxctl, are:
40#
41# p: disable PAGEEXEC P: enable PAGEEXEC
42# e: disable EMUTRMAP E: enable EMUTRMAP
43# m: disable MPROTECT M: enable MPROTECT
44# r: disable RANDMMAP R: enable RANDMMAP
45# s: disable SEGMEXEC S: enable SEGMEXEC
46#
47# Default flags are 'PeMRS', which are the most restrictive
48# settings. Refer to http://pax.grsecurity.net/ for details
49# on what these flags are all about. There is an obsolete
50# flag 'x'/'X' which has been removed from PaX.
51#
52# If chpax is not installed, the legacy EI flags (which are
53# not strip-safe, and strictly speaking violate the ELF spec)
54# will not be set. If paxctl is not installed, it falls back
55# to scanelf. scanelf is always present, but currently doesn't
56# quite do all that paxctl can do.
57# Returns fail if one or more files could not be marked.
58#
59#
60#### list-paxables {<files>}
61# Prints to stdout all of <files> that are suitable to having PaX
62# flags (i.e. filter to just ELF files). Useful for passing wild-card
63# lists of files to pax-mark, although in general it is preferable
64# for ebuilds to list precisely which executables are to be marked.
65# Use like:
66# pax-mark -m $(list-paxables ${S}/{,usr/}bin/*)
67#
68#
69#### host-is-pax
70# Returns true if the host has a PaX-enabled kernel, false otherwise.
71# Intended for use where the build process must be modified conditionally
72# in order to satisfy PaX. Note; it is _not_ intended to indicate
73# whether the final executables should satisfy PaX - executables should
74# always be marked appropriately even if they're only going to be
75# installed on a non-PaX system.
10 76
11inherit eutils 77inherit eutils
12 78
13##### pax-mark #### 79# Default to both EI and PT markings.
14# Mark a file for PaX, with the provided flags, and log it into 80PAX_MARKINGS=${PAX_MARKINGS:="EI PT"}
15# a PaX database. Returns non-zero if flag marking failed.
16#
17# If paxctl is installed, but not chpax, then the legacy
18# EI flags (which are not strip-safe) will not be set.
19# If neither are installed, falls back to scanelf (which
20# is always present, but currently doesn't quite do all
21# that paxctl can do).
22_pax_list_files() {
23 local m cmd
24 m=$1 ; shift
25 for f in $*; do
26 ${cmd} " ${f}"
27 done
28}
29 81
82# pax-mark <flags> {<ELF files>}
30pax-mark() { 83pax-mark() {
31 local f flags fail=0 failures="" 84 local f flags fail=0 failures="" zero_load_alignment
85 # Ignore '-' characters - in particular so that it doesn't matter if
86 # the caller prefixes with -
32 flags=${1//-} 87 flags=${1//-}
33 shift 88 shift
34 if [[ -x /sbin/chpax ]]; then 89 # Try chpax, for (deprecated) EI legacy marking.
90 if type -p chpax > /dev/null && hasq EI ${PAX_MARKINGS}; then
35 einfo "Legacy EI PaX marking -${flags}" 91 elog "Legacy EI PaX marking -${flags}"
36 _pax_list_files echo $* 92 _pax_list_files elog "$@"
37 for f in $*; do 93 for f in "$@"; do
38 /sbin/chpax -${flags} ${f} && continue 94 chpax -${flags} "${f}" && continue
39 fail=1 95 fail=1
40 failures="${failures} ${f}" 96 failures="${failures} ${f}"
41 done 97 done
42 fi 98 fi
43 if [[ -x /sbin/paxctl ]]; then 99 # Try paxctl, then scanelf - paxctl takes precedence
100 # over scanelf.
101 if type -p paxctl > /dev/null && hasq PT ${PAX_MARKINGS}; then
102 # Try paxctl, the upstream supported tool.
44 einfo "PT PaX marking -${flags}" 103 elog "PT PaX marking -${flags}"
45 _pax_list_files echo $* 104 _pax_list_files elog "$@"
46 for f in $*; do 105 for f in "$@"; do
106 # First, try modifying the existing PAX_FLAGS header
47 /sbin/paxctl -q${flags} ${f} && continue 107 paxctl -q${flags} "${f}" && continue
108 # Second, try stealing the (unused under PaX) PT_GNU_STACK header
48 /sbin/paxctl -qc${flags} ${f} && continue 109 paxctl -qc${flags} "${f}" && continue
110 # Third, try pulling the base down a page, to create space and
111 # insert a PT_GNU_STACK header (works on ET_EXEC)
49 /sbin/paxctl -qC${flags} ${f} && continue 112 paxctl -qC${flags} "${f}" && continue
113 # Fourth - check if it loads to 0 (probably an ET_DYN) and if so,
114 # try rebasing with prelink first to give paxctl some space to
115 # grow downwards into.
116 if type -p objdump > /dev/null && type -p prelink > /dev/null; then
117 zero_load_alignment=$(objdump -p "${f}" | \
118 grep -E '^[[:space:]]*LOAD[[:space:]]*off[[:space:]]*0x0+[[:space:]]' | \
119 sed -e 's/.*align\(.*\)/\1/')
120 if [[ ${zero_load_alignment} != "" ]]; then
121 prelink -r $(( 2*(${zero_load_alignment}) )) &&
122 paxctl -qC${flags} "${f}" && continue
123 fi
124 fi
50 fail=1 125 fail=1
51 failures="${failures} ${f}" 126 failures="${failures} ${f}"
52 done 127 done
53 elif [[ -x /usr/bin/scanelf ]]; then 128 elif type -p scanelf > /dev/null && [[ ${PAX_MARKINGS} != "none" ]]; then
129 # Try scanelf, the Gentoo swiss-army knife ELF utility
130 # Currently this sets EI and PT if it can, no option to
131 # control what it does.
54 einfo "Fallback PaX marking -${flags}" 132 elog "Fallback PaX marking -${flags}"
55 _pax_list_files echo $* 133 _pax_list_files elog "$@"
56 /usr/bin/scanelf -Xxz ${flags} $* 134 scanelf -Xxz ${flags} "$@"
57 else 135 elif [[ ${PAX_MARKINGS} != "none" ]]; then
136 # Out of options!
58 failures="$*" 137 failures="$*"
59 fail=1 138 fail=1
60 fi 139 fi
61 if [[ ${fail} == 1 ]]; then 140 if [[ ${fail} == 1 ]]; then
62 ewarn "Failed to set PaX markings -${flags} for:" 141 ewarn "Failed to set PaX markings -${flags} for:"
64 ewarn "Executables may be killed by PaX kernels." 143 ewarn "Executables may be killed by PaX kernels."
65 fi 144 fi
66 return ${fail} 145 return ${fail}
67} 146}
68 147
148# list-paxables {<files>}
149list-paxables() {
150 file "$@" 2> /dev/null | grep -E 'ELF.*(executable|shared object)' | sed -e 's/: .*$//'
151}
152
69##### host-is-pax 153# host-is-pax
70# Indicates whether the build machine has PaX or not; intended for use 154# Note: if procfs is not on /proc, this returns False (e.g. Gentoo/FBSD).
71# where the build process must be modified conditionally in order to satisfy PaX.
72host-is-pax() { 155host-is-pax() {
73 # We need procfs to work this out. PaX is only available on Linux,
74 # so result is always false on non-linux machines (e.g. Gentoo/*BSD)
75 [[ -e /proc/self/status ]] || return 1
76 grep ^PaX: /proc/self/status > /dev/null 156 grep -qs ^PaX: /proc/self/status
77 return $?
78} 157}
158
159
160# INTERNAL FUNCTIONS
161# ------------------
162#
163# These functions are for use internally by the eclass - do not use
164# them elsewhere as they are not supported (i.e. they may be removed
165# or their function may change arbitratily).
166
167# Display a list of things, one per line, indented a bit, using the
168# display command in $1.
169_pax_list_files() {
170 local f cmd
171 cmd=$1
172 shift
173 for f in "$@"; do
174 ${cmd} " ${f}"
175 done
176}
177

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