From 0b9f6558cef5aa8eab2ee41e356bc928bf7ded28 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 6a1d0de0cc..1c4f9fc1ac 100644 --- a/config.mak.uname +++ b/config.mak.uname @@ -542,9 +542,11 @@ 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 53b790dafa252df2d5659c7502be5c988220693b 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 1c4f9fc1ac..cd78ed1ad0 100644 --- a/config.mak.uname +++ b/config.mak.uname @@ -540,6 +540,12 @@ 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