PIE is required for full address space layout optimization (ASLR) and
there is little to no benefit from ASLR without it since global ELF
tables (GOT/PLT) and application code are at known locations.
A wrapper script is required in order to pass the correct flags for
executables without changing the flags for libraries. It adds `-pie`
when linking (no `-c` switch) if `-static` or `-shared` are not passed,
and `-fPIE` whenever `-fPIC` is not already there. This technique comes
from the Debian hardening wrappers.
Position independent code is expensive on i686, so it's only enabled by
default on x86_64 where the cost is negligible. It can be enabled on a
package-by-package basis on i686. The same cost already exists for any
code in a dynamic library.
The hardening-wrapper package also enforces the chosen hardening flags
even when build systems aren't using CFLAGS / CXXFLAGS / LDFLAGS from
the environment. It would need to be moved from [community] to [core].
---
archbuild.in | 5 +++--
makechrootpkg.in | 12 +++++++++++-
2 files changed, 14 insertions(+), 3 deletions(-)
diff --git a/archbuild.in b/archbuild.in
index ae2f511..419ae5b 100644
--- a/archbuild.in
+++ b/archbuild.in
@@ -2,7 +2,7 @@
m4_include(lib/common.sh)
-base_packages=(base-devel)
+base_packages=(base-devel hardening-wrapper)
makechrootpkg_args=(-c -n)
cmd="${0##*/}"
@@ -67,11 +67,12 @@ if ${clean_first} || [[ ! -d "${chroots}/${repo}-${arch}" ]]; then
"${base_packages[@]}" || abort
else
lock 9 "${chroots}/${repo}-${arch}/root.lock" "Locking clean chroot"
+ # upgrade and install any new packages from base_packages
arch-nspawn \
-C "@pkgdatadir@/pacman-${repo}.conf" \
-M "@pkgdatadir@/makepkg-${arch}.conf" \
"${chroots}/${repo}-${arch}/root" \
- pacman -Syu --noconfirm || abort
+ pacman -Syu --noconfirm --needed "${base_packages[@]}" || abort
fi
msg "Building in chroot for [${repo}] (${arch})..."
diff --git a/makechrootpkg.in b/makechrootpkg.in
index 97c7780..ad804fc 100644
--- a/makechrootpkg.in
+++ b/makechrootpkg.in
@@ -320,7 +320,17 @@ _chrootbuild() {
exit 1
fi
- sudo -u nobody makepkg $makepkg_args || exit 1
+ # enforced compiler hardening flags (can be overriden in a PKGBUILD)
+ export HARDENING_BINDNOW=0 HARDENING_FORTIFY=2 HARDENING_RELRO=1
+ export HARDENING_STACK_CHECK=0 HARDENING_STACK_PROTECTOR=2
+ . /etc/makepkg.conf
+ if [[ $CARCH = i686 ]]; then
+ export HARDENING_PIE=0
+ else
+ export HARDENING_PIE=1
+ fi
+
+ sudo -E -u nobody makepkg $makepkg_args || exit 1
if $run_namcap; then
pacman -S --needed --noconfirm namcap
--
2.0.2