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authorGravatar Matt Weber <matthew.weber@rockwellcollins.com>2018-09-17 16:21:49 -0500
committerGravatar Peter Korsgaard <peter@korsgaard.com>2018-10-20 12:50:29 +0200
commit7484c1c3b8065d6f2f5a67607e9917ecfea022eb (patch)
treea1394dde3ab8673adc197327bb2550bdea133a8b
parentc5a7c287de4a3108d8aaf965731ef7978a903875 (diff)
downloadbuildroot-7484c1c3b8065d6f2f5a67607e9917ecfea022eb.tar.gz
buildroot-7484c1c3b8065d6f2f5a67607e9917ecfea022eb.tar.bz2
toolchain/toolchain-wrapper: add BR2_RELRO_
The RELRO/PIE flags are currently passed via CFLAGS/LDFLAGS and this patch proposes moving them to the toolchain wrapper. (1) The flags should _always_ be passed, without leaving the possibility for any package to ignore them. I.e, when BR2_RELRO_FULL=y is used in a build, all executables should be built PIE. Passing those options through the wrapper ensures they are used during the build of all packages. (2) Some options are incompatible with -fPIE. For example, when building object files for a shared libraries, -fPIC is used, and -fPIE shouldn't be used in combination with -fPIE. Similarly, -r or -static are directly incompatible as they are different link time behaviors then the intent of PIE. Passing those options through the wrapper allows to add some "smart" logic to only pass -fPIE/-pie when relevant. (3) Some toolchain, kernel and bootloader packages may want to explicitly disable PIE in a build where the rest of the userspace has intentionally enabled it. The wrapper provides an option to key on the -fno-pie/-no-pie and bypass the appending of RELRO flags. The current Kernel and U-boot source trees include this option. https://github.com/torvalds/linux/commit/8438ee76b004ef66d125ade64c91fc128047d244 https://github.com/u-boot/u-boot/commit/6ace36e19a8cfdd16ce7c02625edf36864897bf5 If using PIE with a older Kernel and/or U-boot version, a backport of these changes might be required. However this patchset also uses the __KERNEL__ and __UBOOT__ defines as a way to disable PIE. NOTE: The current implementation via CFLAGS/LDFLAGS has caused some build time failures as the conditional logic doesn't yet exist in Buildroot: https://bugs.busybox.net/show_bug.cgi?id=11206 https://bugs.busybox.net/show_bug.cgi?id=11321 Good summary of the most common build failures related to enabling pie: https://wiki.ubuntu.com/SecurityTeam/PIE [Peter: minor cleanups] Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com> Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
-rw-r--r--package/Makefile.in11
-rw-r--r--toolchain/toolchain-wrapper.c82
-rw-r--r--toolchain/toolchain-wrapper.mk6
3 files changed, 86 insertions, 13 deletions
diff --git a/package/Makefile.in b/package/Makefile.in
index abfdb819cf..cd2148270a 100644
--- a/package/Makefile.in
+++ b/package/Makefile.in
@@ -141,9 +141,6 @@ ifeq ($(BR2_DEBUG_3),y)
TARGET_DEBUGGING = -g3
endif
-TARGET_CFLAGS_RELRO = -Wl,-z,relro
-TARGET_CFLAGS_RELRO_FULL = -Wl,-z,now $(TARGET_CFLAGS_RELRO)
-
TARGET_LDFLAGS = $(call qstrip,$(BR2_TARGET_LDFLAGS))
ifeq ($(BR2_SSP_REGULAR),y)
@@ -154,14 +151,6 @@ else ifeq ($(BR2_SSP_ALL),y)
TARGET_HARDENED += -fstack-protector-all
endif
-ifeq ($(BR2_RELRO_PARTIAL),y)
-TARGET_HARDENED += $(TARGET_CFLAGS_RELRO)
-TARGET_LDFLAGS += $(TARGET_CFLAGS_RELRO)
-else ifeq ($(BR2_RELRO_FULL),y)
-TARGET_HARDENED += -fPIE $(TARGET_CFLAGS_RELRO_FULL)
-TARGET_LDFLAGS += -pie $(TARGET_CFLAGS_RELRO_FULL)
-endif
-
ifeq ($(BR2_FORTIFY_SOURCE_1),y)
TARGET_HARDENED += -D_FORTIFY_SOURCE=1
else ifeq ($(BR2_FORTIFY_SOURCE_2),y)
diff --git a/toolchain/toolchain-wrapper.c b/toolchain/toolchain-wrapper.c
index c5eb813dd0..c73a0cc079 100644
--- a/toolchain/toolchain-wrapper.c
+++ b/toolchain/toolchain-wrapper.c
@@ -49,8 +49,12 @@ static char _date_[sizeof("-D__DATE__=\"MMM DD YYYY\"")];
* -D__TIME__=
* -D__DATE__=
* -Wno-builtin-macro-redefined
+ * -Wl,-z,now
+ * -Wl,-z,relro
+ * -fPIE
+ * -pie
*/
-#define EXCLUSIVE_ARGS 6
+#define EXCLUSIVE_ARGS 10
static char *predef_args[] = {
#ifdef BR_CCACHE
@@ -236,7 +240,7 @@ int main(int argc, char **argv)
char *env_debug;
char *paranoid_wrapper;
int paranoid;
- int ret, i, count = 0, debug;
+ int ret, i, count = 0, debug, found_shared = 0;
/* Calculate the relative paths */
basename = strrchr(progpath, '/');
@@ -363,6 +367,80 @@ int main(int argc, char **argv)
*cur++ = "-Wno-builtin-macro-redefined";
}
+#ifdef BR2_RELRO_FULL
+ /* Patterned after Fedora/Gentoo hardening approaches.
+ * https://fedoraproject.org/wiki/Changes/Harden_All_Packages
+ * https://wiki.gentoo.org/wiki/Hardened/Toolchain#Position_Independent_Executables_.28PIEs.29
+ *
+ * A few checks are added to allow disabling of PIE
+ * 1) -fno-pie and -no-pie are used by other distros to disable PIE in
+ * cases where the compiler enables it by default. The logic below
+ * maintains that behavior.
+ * Ref: https://wiki.ubuntu.com/SecurityTeam/PIE
+ * 2) A check for -fno-PIE has been used in older Linux Kernel builds
+ * in a similar way to -fno-pie or -no-pie.
+ * 3) A check is added for Kernel and U-boot defines
+ * (-D__KERNEL__ and -D__UBOOT__).
+ */
+ for (i = 1; i < argc; i++) {
+ /* Apply all incompatible link flag and disable checks first */
+ if (!strcmp(argv[i], "-r") ||
+ !strcmp(argv[i], "-Wl,-r") ||
+ !strcmp(argv[i], "-static") ||
+ !strcmp(argv[i], "-D__KERNEL__") ||
+ !strcmp(argv[i], "-D__UBOOT__") ||
+ !strcmp(argv[i], "-fno-pie") ||
+ !strcmp(argv[i], "-fno-PIE") ||
+ !strcmp(argv[i], "-no-pie"))
+ break;
+ /* Record that shared was present which disables -pie but don't
+ * break out of loop as a check needs to occur that possibly
+ * still allows -fPIE to be set
+ */
+ if (!strcmp(argv[i], "-shared"))
+ found_shared = 1;
+ }
+
+ if (i == argc) {
+ /* Compile and link condition checking have been kept split
+ * between these two loops, as there maybe already are valid
+ * compile flags set for position independence. In that case
+ * the wrapper just adds the -pie for link.
+ */
+ for (i = 1; i < argc; i++) {
+ if (!strcmp(argv[i], "-fpie") ||
+ !strcmp(argv[i], "-fPIE") ||
+ !strcmp(argv[i], "-fpic") ||
+ !strcmp(argv[i], "-fPIC"))
+ break;
+ }
+ /* Both args below can be set at compile/link time
+ * and are ignored correctly when not used
+ */
+ if(i == argc)
+ *cur++ = "-fPIE";
+
+ if (!found_shared)
+ *cur++ = "-pie";
+ }
+#endif
+ /* Are we building the Linux Kernel or U-Boot? */
+ for (i = 1; i < argc; i++) {
+ if (!strcmp(argv[i], "-D__KERNEL__") ||
+ !strcmp(argv[i], "-D__UBOOT__"))
+ break;
+ }
+ if (i == argc) {
+ /* https://wiki.gentoo.org/wiki/Hardened/Toolchain#Mark_Read-Only_Appropriate_Sections */
+#ifdef BR2_RELRO_PARTIAL
+ *cur++ = "-Wl,-z,relro";
+#endif
+#ifdef BR2_RELRO_FULL
+ *cur++ = "-Wl,-z,now";
+ *cur++ = "-Wl,-z,relro";
+#endif
+ }
+
paranoid_wrapper = getenv("BR_COMPILER_PARANOID_UNSAFE_PATH");
if (paranoid_wrapper && strlen(paranoid_wrapper) > 0)
paranoid = 1;
diff --git a/toolchain/toolchain-wrapper.mk b/toolchain/toolchain-wrapper.mk
index b8074efc3c..99d303975c 100644
--- a/toolchain/toolchain-wrapper.mk
+++ b/toolchain/toolchain-wrapper.mk
@@ -45,6 +45,12 @@ ifeq ($(BR2_CCACHE_USE_BASEDIR),y)
TOOLCHAIN_WRAPPER_ARGS += -DBR_CCACHE_BASEDIR='"$(BASE_DIR)"'
endif
+ifeq ($(BR2_RELRO_PARTIAL),y)
+TOOLCHAIN_WRAPPER_ARGS += -DBR2_RELRO_PARTIAL
+else ifeq ($(BR2_RELRO_FULL),y)
+TOOLCHAIN_WRAPPER_ARGS += -DBR2_RELRO_FULL
+endif
+
define TOOLCHAIN_WRAPPER_BUILD
$(HOSTCC) $(HOST_CFLAGS) $(TOOLCHAIN_WRAPPER_ARGS) \
-s -Wl,--hash-style=$(TOOLCHAIN_WRAPPER_HASH_STYLE) \