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declare -a hardeningCFlagsAfter=()
declare -a hardeningCFlagsBefore=()
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
# fortify3 implies fortify enablement - make explicit before
# we filter unsupported flags because unsupporting fortify3
# doesn't mean we should unsupport fortify too
if [[ -n "${hardeningEnableMap[fortify3]-}" ]]; then
hardeningEnableMap["fortify"]=1
fi
# Remove unsupported flags.
for flag in @hardening_unsupported_flags@; do
unset -v "hardeningEnableMap[$flag]"
# fortify being unsupported implies fortify3 is unsupported
if [[ "$flag" = 'fortify' ]] ; then
unset -v "hardeningEnableMap['fortify3']"
fi
done
# now make fortify and fortify3 mutually exclusive
if [[ -n "${hardeningEnableMap[fortify3]-}" ]]; then
unset -v "hardeningEnableMap['fortify']"
fi
if (( "${NIX_DEBUG:-0}" >= 1 )); then
declare -a allHardeningFlags=(fortify fortify3 stackprotector pie pic strictoverflow format)
declare -A hardeningDisableMap=()
# Determine which flags were effectively disabled so we can report below.
for flag in "${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 | fortify3)
# Use -U_FORTIFY_SOURCE to avoid warnings on toolchains that explicitly
# set -D_FORTIFY_SOURCE=0 (like 'clang -fsanitize=address').
hardeningCFlagsBefore+=('-O2' '-U_FORTIFY_SOURCE')
# Unset any _FORTIFY_SOURCE values the command-line may have set before
# enforcing our own value, avoiding (potentially fatal) redefinition
# warnings
hardeningCFlagsAfter+=('-U_FORTIFY_SOURCE')
case $flag in
fortify)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling fortify >&2; fi
hardeningCFlagsAfter+=('-D_FORTIFY_SOURCE=2')
;;
fortify3)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling fortify3 >&2; fi
hardeningCFlagsAfter+=('-D_FORTIFY_SOURCE=3')
;;
*)
# Ignore unsupported.
;;
esac
;;
stackprotector)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling stackprotector >&2; fi
hardeningCFlagsBefore+=('-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 (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling CFlags -fPIE >&2; fi
hardeningCFlagsBefore=('-fPIE' "${hardeningCFlagsBefore[@]}")
if [[ ! (" ${params[*]} " =~ " -shared " || " ${params[*]} " =~ " -static ") ]]; then
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling LDFlags -pie >&2; fi
hardeningCFlagsBefore=('-pie' "${hardeningCFlagsBefore[@]}")
fi
;;
pic)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling pic >&2; fi
hardeningCFlagsBefore+=('-fPIC')
;;
strictoverflow)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling strictoverflow >&2; fi
if (( @isClang@ )); then
# In Clang, -fno-strict-overflow only serves to set -fwrapv and is
# reported as an unused CLI argument if -fwrapv or -fno-wrapv is set
# explicitly, so we side step that by doing the conversion here.
#
# See: https://github.com/llvm/llvm-project/blob/llvmorg-16.0.6/clang/lib/Driver/ToolChains/Clang.cpp#L6315
#
hardeningCFlagsBefore+=('-fwrapv')
else
hardeningCFlagsBefore+=('-fno-strict-overflow')
fi
;;
format)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling format >&2; fi
hardeningCFlagsBefore+=('-Wformat' '-Wformat-security' '-Werror=format-security')
;;
*)
# Ignore unsupported. Checked in Nix that at least *some*
# tool supports each flag.
;;
esac
done
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