From ce854a8d22d5056cc1a47a0d4d4251f93a0c667c Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Tue, 12 Apr 2016 18:59:40 -0400
Subject: Add -ftrapv to gcc-hardening ... mostly!

We know there are overflows in curve25519-donna-c32, so we'll have
to have that one be fwrapv.

Only apply the asan, ubsan, and trapv options to the code that does
not need to run in constant time.  Those options introduce branches
to the code they instrument.

(These introduced branches should never actually be taken, so it
might _still_ be constant time after all, but branch predictors are
complicated enough that I'm not really confident here. Let's aim for
safety.)

Closes 17983.
---
 configure.ac | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

(limited to 'configure.ac')

diff --git a/configure.ac b/configure.ac
index 4bdd2d3967..626be6c111 100644
--- a/configure.ac
+++ b/configure.ac
@@ -755,6 +755,11 @@ dnl use it with a build of a library.
 all_ldflags_for_check="$TOR_LDFLAGS_zlib $TOR_LDFLAGS_openssl $TOR_LDFLAGS_libevent"
 all_libs_for_check="$TOR_ZLIB_LIBS $TOR_LIB_MATH $TOR_LIBEVENT_LIBS $TOR_OPENSSL_LIBS $TOR_SYSTEMD_LIBS $TOR_LIB_WS32 $TOR_LIB_GDI $TOR_CAP_LIBS"
 
+CFLAGS_FTRAPV=
+CFLAGS_FWRAPV=
+CFLAGS_ASAN=
+CFLAGS_UBSAN=
+
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [
 #if !defined(__clang__)
 #error
@@ -777,20 +782,32 @@ m4_ifdef([AS_VAR_IF],[
     AS_VAR_POPDEF([can_link])
     AS_VAR_POPDEF([can_compile])
     TOR_CHECK_CFLAGS(-Wstack-protector)
-    TOR_CHECK_CFLAGS(-fwrapv)
     TOR_CHECK_CFLAGS(--param ssp-buffer-size=1)
     if test "$bwin32" = "false"; then
        TOR_CHECK_CFLAGS(-fPIE)
        TOR_CHECK_LDFLAGS(-pie, "$all_ldflags_for_check", "$all_libs_for_check")
     fi
+    TOR_TRY_COMPILE_WITH_CFLAGS(-ftrapv, , CFLAGS_FTRAPV="-ftrapv", /bin/true)
+    TOR_TRY_COMPILE_WITH_CFLAGS(-fwrapv, , CFLAGS_FWRAPV="-fwrapv", /bin/true)
 fi
 
 if test "x$enable_expensive_hardening" = "xyes"; then
-   TOR_CHECK_CFLAGS([-fsanitize=address])
-   TOR_CHECK_CFLAGS([-fsanitize=undefined])
+   TOR_TRY_COMPILE_WITH_CFLAGS([-fsanitize=address], , CFLAGS_ASAN="-fsanitize=address", /bin/true)
+   TOR_TRY_COMPILE_WITH_CFLAGS([-fsanitize=undefined], , CFLAGS_UBSAN="-fsanitize=undefined", /bin/true)
    TOR_CHECK_CFLAGS([-fno-omit-frame-pointer])
 fi
 
+CFLAGS_BUGTRAP="$CFLAGS_FTRAPV $CFLAGS_ASAN $CFLAGS_UBSAN"
+CFLAGS_CONSTTIME="$CFLAGS_FWRAPV"
+
+dnl These cflags add bunches of branches, and we haven't been able to
+dnl persuade ourselves that they're suitable for code that needs to be
+dnl constant time.
+AC_SUBST(CFLAGS_BUGTRAP)
+dnl These cflags are variant ones sutable for code that needs to be
+dnl constant-time.
+AC_SUBST(CFLAGS_CONSTTIME)
+
 if test "x$enable_linker_hardening" != "xno"; then
     TOR_CHECK_LDFLAGS(-z relro -z now, "$all_ldflags_for_check", "$all_libs_for_check")
 fi
-- 
cgit v1.2.3-54-g00ecf


From a3615a988ebb1181ae636d0f9111ade0f1d3f6cb Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Thu, 12 May 2016 12:54:15 -0400
Subject: Prefer builtin true.

---
 configure.ac | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

(limited to 'configure.ac')

diff --git a/configure.ac b/configure.ac
index 626be6c111..0a78a9f9c7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -787,13 +787,13 @@ m4_ifdef([AS_VAR_IF],[
        TOR_CHECK_CFLAGS(-fPIE)
        TOR_CHECK_LDFLAGS(-pie, "$all_ldflags_for_check", "$all_libs_for_check")
     fi
-    TOR_TRY_COMPILE_WITH_CFLAGS(-ftrapv, , CFLAGS_FTRAPV="-ftrapv", /bin/true)
-    TOR_TRY_COMPILE_WITH_CFLAGS(-fwrapv, , CFLAGS_FWRAPV="-fwrapv", /bin/true)
+    TOR_TRY_COMPILE_WITH_CFLAGS(-ftrapv, , CFLAGS_FTRAPV="-ftrapv", true)
+    TOR_TRY_COMPILE_WITH_CFLAGS(-fwrapv, , CFLAGS_FWRAPV="-fwrapv", true)
 fi
 
 if test "x$enable_expensive_hardening" = "xyes"; then
-   TOR_TRY_COMPILE_WITH_CFLAGS([-fsanitize=address], , CFLAGS_ASAN="-fsanitize=address", /bin/true)
-   TOR_TRY_COMPILE_WITH_CFLAGS([-fsanitize=undefined], , CFLAGS_UBSAN="-fsanitize=undefined", /bin/true)
+   TOR_TRY_COMPILE_WITH_CFLAGS([-fsanitize=address], , CFLAGS_ASAN="-fsanitize=address", true)
+   TOR_TRY_COMPILE_WITH_CFLAGS([-fsanitize=undefined], , CFLAGS_UBSAN="-fsanitize=undefined", true)
    TOR_CHECK_CFLAGS([-fno-omit-frame-pointer])
 fi
 
-- 
cgit v1.2.3-54-g00ecf