From ae7985a3cb91500845b0935876c8c5c664678d65 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=C4=B0smail=20D=C3=B6nmez?= Date: Sat, 16 Jan 2016 18:59:31 +0200 Subject: [PATCH 1/2] Don't let ld strip relocations MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This is the first step for enabling ASLR (Address Space Layout Randomization) support. We want to enable ASLR for better protection against exploiting security holes in Git. The problem fixed by this commit is that `ld.exe` seems to be stripping relocations which in turn will break ASLR support. We just make sure it's not stripping the main executable entry. Signed-off-by: İsmail Dönmez Signed-off-by: Johannes Schindelin --- config.mak.uname | 2 ++ 1 file changed, 2 insertions(+) diff --git a/config.mak.uname b/config.mak.uname index e47af72e01..a4b4eb6c84 100644 --- a/config.mak.uname +++ b/config.mak.uname @@ -562,9 +562,11 @@ else prefix = /usr/ ifeq (MINGW32,$(MSYSTEM)) prefix = /mingw32 + BASIC_LDFLAGS += -Wl,--pic-executable,-e,_mainCRTStartup endif ifeq (MINGW64,$(MSYSTEM)) prefix = /mingw64 + BASIC_LDFLAGS += -Wl,--pic-executable,-e,mainCRTStartup else COMPAT_CFLAGS += -D_USE_32BIT_TIME_T BASIC_LDFLAGS += -Wl,--large-address-aware From a55a801a1b50057f1473c15edd3977cf06cf7214 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=C4=B0smail=20D=C3=B6nmez?= Date: Sat, 16 Jan 2016 19:09:34 +0200 Subject: [PATCH 2/2] Enable DEP and ASLR MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Enable DEP (Data Execution Prevention) and ASLR (Address Space Layout Randomization) support. This applies to both 32bit and 64bit builds and makes it substantially harder to exploit security holes in Git by offering a much more unpredictable attack surface. ASLR interferes with GDB's ability to set breakpoints. A similar issue holds true when compiling with -O2 (in which case single-stepping is messed up because GDB cannot map the code back to the original source code properly). Therefore we simply enable ASLR only when an optimization flag is present in the CFLAGS, using it as an indicator that the developer does not want to debug in GDB anyway. Signed-off-by: İsmail Dönmez Signed-off-by: Johannes Schindelin --- config.mak.uname | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/config.mak.uname b/config.mak.uname index a4b4eb6c84..3c00bd9133 100644 --- a/config.mak.uname +++ b/config.mak.uname @@ -560,6 +560,12 @@ else ifeq ($(shell expr "$(uname_R)" : '2\.'),2) # MSys2 prefix = /usr/ + # Enable DEP + BASIC_LDFLAGS += -Wl,--nxcompat + # Enable ASLR (unless debugging) + ifneq (,$(findstring -O,$(CFLAGS))) + BASIC_LDFLAGS += -Wl,--dynamicbase + endif ifeq (MINGW32,$(MSYSTEM)) prefix = /mingw32 BASIC_LDFLAGS += -Wl,--pic-executable,-e,_mainCRTStartup