[PATCH] Add compiler defenses flags

[PATCH] Add compiler defenses flags

[Mateusz Grzonka]

It is essential to avoid buffer overflows and similar bugs as much as
possible.

According to Intel rules we are obligated to verify certain
compiler flags, so it will be much easier if they are added to the
Makefile.

Add gcc flags for prevention of buffer overflows, format string vulnerabilities,
stack protection to prevent stack overwrites and aslr enablement through -fPIE.
Also make the flags configurable.

The changes were verified on gcc versions 7.5, 8.3, 9.2, 10 and 12.2.

Signed-off-by: Mateusz Grzonka <mateusz.grzonka@intel.com>
---
 Makefile | 41 +++++++++++++++++++++++++++++------------
 1 file changed, 29 insertions(+), 12 deletions(-)

diff --git a/Makefile b/Makefile
index 5eac1a4e..b3aa36f6 100644
--- a/Makefile
+++ b/Makefile
@@ -30,7 +30,7 @@
 
 # define "CXFLAGS" to give extra flags to CC.
 # e.g.  make CXFLAGS=-O to optimise
-CXFLAGS ?=-O2
+CXFLAGS ?=-O2 -D_FORTIFY_SOURCE=2
 TCC = tcc
 UCLIBC_GCC = $(shell for nm in i386-uclibc-linux-gcc i386-uclibc-gcc; do which $$nm > /dev/null && { echo $$nm ; exit; } ; done; echo false No uclibc found )
 #DIET_GCC = diet gcc
@@ -50,14 +50,30 @@ ifeq ($(origin CC),default)
 CC := $(CROSS_COMPILE)gcc
 endif
 CXFLAGS ?= -ggdb
-CWFLAGS = -Wall -Werror -Wstrict-prototypes -Wextra -Wno-unused-parameter
+CWFLAGS ?= -Wall -Werror -Wstrict-prototypes -Wextra -Wno-unused-parameter -Wformat -Wformat-security -Werror=format-security -fstack-protector-strong -fPIE -Warray-bounds
 ifdef WARN_UNUSED
-CWFLAGS += -Wp,-D_FORTIFY_SOURCE=2 -O3
+CWFLAGS += -Wp -O3
 endif
 
-FALLTHROUGH := $(shell gcc -v --help 2>&1 | grep "implicit-fallthrough" | wc -l)
-ifneq "$(FALLTHROUGH)"  "0"
-CWFLAGS += -Wimplicit-fallthrough=0
+ifeq ($(origin FALLTHROUGH), undefined)
+	FALLTHROUGH := $(shell gcc -Q --help=warnings 2>&1 | grep "implicit-fallthrough" | wc -l)
+	ifneq "$(FALLTHROUGH)"  "0"
+	CWFLAGS += -Wimplicit-fallthrough=0
+	endif
+endif
+
+ifeq ($(origin FORMATOVERFLOW), undefined)
+	FORMATOVERFLOW := $(shell gcc -Q --help=warnings 2>&1 | grep "format-overflow" | wc -l)
+	ifneq "$(FORMATOVERFLOW)"  "0"
+	CWFLAGS += -Wformat-overflow
+	endif
+endif
+
+ifeq ($(origin STRINGOPOVERFLOW), undefined)
+	STRINGOPOVERFLOW := $(shell gcc -Q --help=warnings 2>&1 | grep "stringop-overflow" | wc -l)
+	ifneq "$(STRINGOPOVERFLOW)"  "0"
+	CWFLAGS += -Wstringop-overflow
+	endif
 endif
 
 ifdef DEBIAN
@@ -116,10 +132,12 @@ CFLAGS += -DUSE_PTHREADS
 MON_LDFLAGS += -pthread
 endif
 
+LDFLAGS = -Wl,-z,now,-z,noexecstack
+
 # If you want a static binary, you might uncomment these
-# LDFLAGS = -static
+# LDFLAGS += -static
 # STRIP = -s
-LDLIBS = -ldl
+LDLIBS = -ldl -pie
 
 # To explicitly disable libudev, set -DNO_LIBUDEV in CXFLAGS
 ifeq (, $(findstring -DNO_LIBUDEV,  $(CXFLAGS)))
@@ -209,14 +227,13 @@ mdadm.Os : $(SRCS) $(INCL)
 	$(CC) -o mdadm.Os $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) -DHAVE_STDINT_H -Os $(SRCS) $(LDLIBS)
 
 mdadm.O2 : $(SRCS) $(INCL) mdmon.O2
-	$(CC) -o mdadm.O2 $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) -DHAVE_STDINT_H -O2 -D_FORTIFY_SOURCE=2 $(SRCS) $(LDLIBS)
+	$(CC) -o mdadm.O2 $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) -DHAVE_STDINT_H -O2 $(SRCS) $(LDLIBS)
 
 mdmon.O2 : $(MON_SRCS) $(INCL) mdmon.h
-	$(CC) -o mdmon.O2 $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) $(MON_LDFLAGS) -DHAVE_STDINT_H -O2 -D_FORTIFY_SOURCE=2 $(MON_SRCS) $(LDLIBS)
+	$(CC) -o mdmon.O2 $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) $(MON_LDFLAGS) -DHAVE_STDINT_H -O2 $(MON_SRCS) $(LDLIBS)
 
-# use '-z now' to guarantee no dynamic linker interactions with the monitor thread
 mdmon : $(MON_OBJS) | check_rundir
-	$(CC) $(CFLAGS) $(LDFLAGS) $(MON_LDFLAGS) -Wl,-z,now -o mdmon $(MON_OBJS) $(LDLIBS)
+	$(CC) $(CFLAGS) $(LDFLAGS) $(MON_LDFLAGS) -o mdmon $(MON_OBJS) $(LDLIBS)
 msg.o: msg.c msg.h
 
 test_stripe : restripe.c xmalloc.o mdadm.h
-- 
2.26.2

Re: [PATCH] Add compiler defenses flags

[Jes Sorensen]

On 7/17/23 09:19, Mateusz Grzonka wrote:
> It is essential to avoid buffer overflows and similar bugs as much as
> possible.
> 
> According to Intel rules we are obligated to verify certain
> compiler flags, so it will be much easier if they are added to the
> Makefile.
> 
> Add gcc flags for prevention of buffer overflows, format string vulnerabilities,
> stack protection to prevent stack overwrites and aslr enablement through -fPIE.
> Also make the flags configurable.
> 
> The changes were verified on gcc versions 7.5, 8.3, 9.2, 10 and 12.2.
> 
> Signed-off-by: Mateusz Grzonka <mateusz.grzonka@intel.com>

Seems reasonable and fairly broad testing, so applied!

Thanks,
Jes