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cc-wrapper: add fortify flags after invocation args, not before

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this splits hardeningCFlags into hardeningCFlagsAfter and
hardeningCFlagsBefore (where most flags still remain) to allow
us to *append* `-D_FORTIFY_SOURCE=` values to the command-line,
forcing our choice of fortify level and avoiding potential
redefinition warnings/errors through use of `-U_FORTIFY_SOURCE`
This commit is contained in:
Robert Scott 2023-07-30 12:25:02 +01:00
parent bb1bf988bc
commit 658ab4b45b
2 changed files with 18 additions and 13 deletions
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27
pkgs/build-support/cc-wrapper/add-hardening.sh
View File

@ -1,4 +1,5 @@
declare -a hardeningCFlags=()
declare -a hardeningCFlagsAfter=()
declare -a hardeningCFlagsBefore=()
declare -A hardeningEnableMap=()
@ -48,15 +49,19 @@ for flag in "${!hardeningEnableMap[@]}"; do
fortify | fortify3)
# Use -U_FORTIFY_SOURCE to avoid warnings on toolchains that explicitly
# set -D_FORTIFY_SOURCE=0 (like 'clang -fsanitize=address').
hardeningCFlags+=('-O2' '-U_FORTIFY_SOURCE')
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
hardeningCFlags+=('-D_FORTIFY_SOURCE=2')
hardeningCFlagsAfter+=('-D_FORTIFY_SOURCE=2')
;;
fortify3)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling fortify3 >&2; fi
hardeningCFlags+=('-D_FORTIFY_SOURCE=3')
hardeningCFlagsAfter+=('-D_FORTIFY_SOURCE=3')
;;
*)
# Ignore unsupported.
@ -65,20 +70,20 @@ for flag in "${!hardeningEnableMap[@]}"; do
;;
stackprotector)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling stackprotector >&2; fi
hardeningCFlags+=('-fstack-protector-strong' '--param' 'ssp-buffer-size=4')
hardeningCFlagsBefore+=('-fstack-protector-strong' '--param' 'ssp-buffer-size=4')
;;
pie)
# NB: we do not use `+=` here, because PIE flags must occur before any PIC flags
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling CFlags -fPIE >&2; fi
hardeningCFlags=('-fPIE' "${hardeningCFlags[@]}")
hardeningCFlagsBefore=('-fPIE' "${hardeningCFlagsBefore[@]}")
if [[ ! (" ${params[*]} " =~ " -shared " || " ${params[*]} " =~ " -static ") ]]; then
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling LDFlags -pie >&2; fi
hardeningCFlags=('-pie' "${hardeningCFlags[@]}")
hardeningCFlagsBefore=('-pie' "${hardeningCFlagsBefore[@]}")
fi
;;
pic)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling pic >&2; fi
hardeningCFlags+=('-fPIC')
hardeningCFlagsBefore+=('-fPIC')
;;
strictoverflow)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling strictoverflow >&2; fi
@ -89,14 +94,14 @@ for flag in "${!hardeningEnableMap[@]}"; do
#
# See: https://github.com/llvm/llvm-project/blob/llvmorg-16.0.6/clang/lib/Driver/ToolChains/Clang.cpp#L6315
#
hardeningCFlags+=('-fwrapv')
hardeningCFlagsBefore+=('-fwrapv')
else
hardeningCFlags+=('-fno-strict-overflow')
hardeningCFlagsBefore+=('-fno-strict-overflow')
fi
;;
format)
if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling format >&2; fi
hardeningCFlags+=('-Wformat' '-Wformat-security' '-Werror=format-security')
hardeningCFlagsBefore+=('-Wformat' '-Wformat-security' '-Werror=format-security')
;;
*)
# Ignore unsupported. Checked in Nix that at least *some*

4
pkgs/build-support/cc-wrapper/cc-wrapper.sh
View File

@ -171,8 +171,8 @@ fi
source @out@/nix-support/add-hardening.sh
# Add the flags for the C compiler proper.
extraAfter=($NIX_CFLAGS_COMPILE_@suffixSalt@)
extraBefore=(${hardeningCFlags[@]+"${hardeningCFlags[@]}"} $NIX_CFLAGS_COMPILE_BEFORE_@suffixSalt@)
extraAfter=(${hardeningCFlagsAfter[@]+"${hardeningCFlagsAfter[@]}"} $NIX_CFLAGS_COMPILE_@suffixSalt@)
extraBefore=(${hardeningCFlagsBefore[@]+"${hardeningCFlagsBefore[@]}"} $NIX_CFLAGS_COMPILE_BEFORE_@suffixSalt@)
if [ "$dontLink" != 1 ]; then