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