rngrd

commit ca878129a100bb5848fbb4bae61aa5a574e9588d
parent b2513c79c1e5e7f2ef5c91adc7f133a862ebc124
Author: Vincent Forest <vincent.forest@meso-star.com>
Date:   Wed, 11 Oct 2023 17:18:49 +0200

Make generated binaries safer and more robust

Define the CFLAGS_HARDENED and LDFLAGS_HARDENED macros, which list
compiler and linker options that activate various hardening features
aimed at increasing the security and robustness of generated binaries.

The link editor options have all been available since at least ld 2.25.
So you don't have to worry about compatibility issues.

The compiler options are in fact some of those that will be enabled by
the -fhardened option to be introduced in GCC 14. In the following, we
list them and indicate the version of GCC from which they are documented
in the manual, i.e. from which version of GCC they would appear to be
available:

  -D_FORTIFY_SOURCE [GCC 5.5]
  -fcf-protection options [GCC 8.5]
  -fstack-protector-strong [GCC 6.5]
  -fstack-clash-protection [GCC 8.5]
  -ftrivial-auto-var-init [GCC 12.3]

The latter, -ftrivial-auto-var-init, is too recent. To avoid any
compatibility problems, we haven't activated it yet.

Diffstat:
M
Makefile
 | 
12
++++++------
M
config.mk
 | 
20
++++++++++++++------

2 files changed, 20 insertions(+), 12 deletions(-)
diff --git a/Makefile b/Makefile
@@ -47,7 +47,7 @@ build_library: .config $(DEP)
 $(DEP) $(OBJ): config.mk
 
 $(LIBNAME_SHARED): $(OBJ)
-	$(CC) $(CFLAGS) $(DPDC_CFLAGS) -o $@ $(OBJ) $(LDFLAGS) $(SOFLAGS) $(DPDC_LIBS)
+	$(CC) $(CFLAGS_SO) $(DPDC_CFLAGS) -o $@ $(OBJ) $(LDFLAGS_SO) $(DPDC_LIBS)
 
 $(LIBNAME_STATIC): librngrd.o
 	$(AR) -rc $@ $?
@@ -76,10 +76,10 @@ librngrd.o: $(OBJ)
 
 .SUFFIXES: .c .d .o
 .c.d:
-	@$(CC) $(CFLAGS) $(DPDC_CFLAGS) -MM -MT "$(@:.d=.o) $@" $< -MF $@
+	@$(CC) $(CFLAGS_SO) $(DPDC_CFLAGS) -MM -MT "$(@:.d=.o) $@" $< -MF $@
 
 .c.o:
-	$(CC) $(CFLAGS) $(DPDC_CFLAGS) -DRNGRD_SHARED_BUILD -c $< -o $@
+	$(CC) $(CFLAGS_SO) $(DPDC_CFLAGS) -DRNGRD_SHARED_BUILD -c $< -o $@
 
 ################################################################################
 # Installation
@@ -158,11 +158,11 @@ clean_test:
 	rm -f test_rngrd src/test_rngrd.o
 
 $(TEST_DEP): config.mk rngrd-local.pc
-	@$(CC) $(CFLAGS) $(RSYS_CFLAGS) $(RNGRD_CFLAGS) \
+	@$(CC) $(CFLAGS_EXE) $(RSYS_CFLAGS) $(RNGRD_CFLAGS) \
 	-MM -MT "$(@:.d=.o) $@" $(@:.d=.c) -MF $@
 
 src/test_rngrd.o: config.mk rngrd-local.pc
-	$(CC) $(CFLAGS) $(RSYS_CFLAGS) $(RNGRD_CFLAGS) -c $(@:.o=.c) -o $@
+	$(CC) $(CFLAGS_EXE) $(RSYS_CFLAGS) $(RNGRD_CFLAGS) -c $(@:.o=.c) -o $@
 
 test_rngrd: src/test_rngrd.o config.mk rngrd-local.pc $(LIBNAME)
-	$(CC) -o $@ src/$@.o $(RSYS_LIBS) $(RNGRD_LIBS)
+	$(CC) $(CFLAGS_EXE) -o $@ src/$@.o $(LDFLAGS_EXE) $(RSYS_LIBS) $(RNGRD_LIBS)
diff --git a/config.mk b/config.mk
@@ -83,26 +83,34 @@ WFLAGS =\
  -Wmissing-prototypes\
  -Wshadow
 
+CFLAGS_HARDENED =\
+ -D_FORTIFY_SOURCES=2\
+ -fcf-protection=full\
+ -fstack-clash-protection\
+ -fstack-protector-strong
+
 CFLAGS_COMMON =\
  -std=c89\
  -pedantic\
- -fPIC\
  -fvisibility=hidden\
  -fstrict-aliasing\
+ $(CFLAGS_HARDENED)\
  $(WFLAGS)
 
 CFLAGS_RELEASE = -O2 -DNDEBUG $(CFLAGS_COMMON)
 CFLAGS_DEBUG = -g $(CFLAGS_COMMON)
-CFLAGS = $(CFLAGS_$(BUILD_TYPE))
+CFLAGS_SO = $(CFLAGS_$(BUILD_TYPE)) -fPIC
+CFLAGS_EXE = $(CFLAGS_$(BUILD_TYPE)) -fPIE
 
 ################################################################################
 # Linker options
 ################################################################################
-SOFLAGS = -shared -Wl,--no-undefined
+LDFLAGS_HARDENED = -Wl,-z,relro,-z,now
+LDFLAGS_DEBUG = $(LDFLAGS_HARDENED)
+LDFLAGS_RELEASE = -s $(LDFLAGS_HARDENED)
 
-LDFLAGS_DEBUG =
-LDFLAGS_RELEASE = -s
-LDFLAGS = $(LDFLAGS_$(BUILD_TYPE))
+LDFLAGS_SO = $(LDFLAGS_$(BUILD_TYPE)) -shared -Wl,--no-undefined
+LDFLAGS_EXE = $(LDFLAGS_$(BUILD_TYPE)) -pie
 
 OCPFLAGS_DEBUG = --localize-hidden
 OCPFLAGS_RELEASE = --localize-hidden --strip-unneeded