nixpkgs/pkgs/build-support/cc-wrapper/add-hardening.sh

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declare -a hardeningCFlags=()
declare -A hardeningEnableMap=()
# Intentionally word-split in case 'NIX_HARDENING_ENABLE' is defined in Nix. The
# array expansion also prevents undefined variables from causing trouble with
# `set -u`.
for flag in ${NIX_HARDENING_ENABLE_@suffixSalt@-}; do
hardeningEnableMap["$flag"]=1
done
# Remove unsupported flags.
for flag in @hardening_unsupported_flags@; do
unset -v "hardeningEnableMap[$flag]"
done
if (( "${NIX_DEBUG:-0}" >= 1 )); then
declare -a allHardeningFlags=(fortify stackprotector pie pic strictoverflow format)
declare -A hardeningDisableMap=()
# Determine which flags were effectively disabled so we can report below.
for flag in "${allHardeningFlags[@]}"; do
if [[ -z "${hardeningEnableMap[$flag]-}" ]]; then
hardeningDisableMap["$flag"]=1
fi
done
printf 'HARDENING: disabled flags:' >&2
(( "${#hardeningDisableMap[@]}" )) && printf ' %q' "${!hardeningDisableMap[@]}" >&2
echo >&2
if (( "${#hardeningEnableMap[@]}" )); then
echo 'HARDENING: Is active (not completely disabled with "all" flag)' >&2;
fi
fi
for flag in "${!hardeningEnableMap[@]}"; do
case $flag in
fortify)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling fortify >&2; fi
hardeningCFlags+=('-O2' '-D_FORTIFY_SOURCE=2')
;;
stackprotector)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling stackprotector >&2; fi
hardeningCFlags+=('-fstack-protector-strong' '--param' 'ssp-buffer-size=4')
;;
pie)
# NB: we do not use `+=` here, because PIE flags must occur before any PIC flags
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling CFlags -fPIE >&2; fi
hardeningCFlags=('-fPIE' "${hardeningCFlags[@]}")
if [[ ! (" $* " =~ " -shared " || " $* " =~ " -static ") ]]; then
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling LDFlags -pie >&2; fi
hardeningCFlags=('-pie' "${hardeningCFlags[@]}")
fi
;;
pic)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling pic >&2; fi
hardeningCFlags+=('-fPIC')
;;
strictoverflow)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling strictoverflow >&2; fi
hardeningCFlags+=('-fno-strict-overflow')
;;
format)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling format >&2; fi
hardeningCFlags+=('-Wformat' '-Wformat-security' '-Werror=format-security')
;;
*)
# Ignore unsupported. Checked in Nix that at least *some*
# tool supports each flag.
;;
esac
done