Add clang's CFI instrumentation

Add --enable-cfi ./configure option to enable
LLVM/Clang's Control Flow Integrity for builds.

CFI aborts a program upon detecting certain forms of undefined behavior
that can potentially allow attackers to subvert the program’s control flow.

.travis.yml

@@ -1,15 +1,16 @@
 sudo: false
+dist: trusty
 
 language: c
 
 compiler:
   - gcc
-  - clang
+  - clang-3.8
 
 branches:
   only:
     - master
-        - develop
+    - clang-cfi
 
 env:
   - RUNTIME=libicu
@@ -26,23 +27,26 @@ addons:
       - libtool
       - gtk-doc-tools
       - gettext
-            - libidn11
       - libidn11-dev
-            - libidn2-0
       - libidn2-0-dev
-            - libicu48
       - libicu-dev
-            - libunistring0
       - libunistring-dev
       - lcov
+      - clang-3.8
+      - llvm-3.8-dev
+      - llvm-dev
 
 script:
   - ./autogen.sh
-  - ./configure && make -j4 && make check -j4
+#  CFI doesn't work out on Ubuntu 14.04 (Trusty). They dont't include LLVMgold.so for clang-3.8.
-  - ./configure --enable-runtime=$RUNTIME --enable-builtin=libicu && make clean && make -j4 && make check -j4
+#  clang-3.4 doesn't know CFI yet.
-  - ./configure --enable-runtime=$RUNTIME --enable-builtin=libidn2 && make clean && make -j4 && make check -j4
+#  The only chance with Travis-CI is to switch to docker and use Ubuntu 16.04 or whatever.
-  - ./configure --enable-runtime=$RUNTIME --enable-builtin=libidn && make clean && make -j4 && make check -j4
+#  - if [[ $CC == "gcc" ]]; then CFI=""; else CFI="--enable-cfi"; fi
-  - ./configure --enable-runtime=$RUNTIME --disable-builtin && make clean && make -j4 && make check -j4
+  - ./configure $CFI && make -j4 && make check -j4 || (cat config.log; ls -la /usr/lib/*gold*)
+  - ./configure $CFI --enable-runtime=$RUNTIME --enable-builtin=libicu && make clean && make -j4 && make check -j4
+  - ./configure $CFI --enable-runtime=$RUNTIME --enable-builtin=libidn2 && make clean && make -j4 && make check -j4
+  - ./configure $CFI --enable-runtime=$RUNTIME --enable-builtin=libidn && make clean && make -j4 && make check -j4
+  - ./configure $CFI --enable-runtime=$RUNTIME --disable-builtin && make clean && make -j4 && make check -j4
   - ./configure --enable-gtk-doc && make -j4 && make check -j4
   - make distcheck
   - if [[ $CC == "gcc" && $RUNTIME == "libicu" ]]; then ./.travis_coveralls.sh; fi

.travis_coveralls.sh

@@ -1,11 +1,12 @@
 #!/bin/bash
 
 make check-coverage-libicu
+pip install --upgrade pip
 pip install --user urllib3[secure] cpp-coveralls
 
 # Work around https://github.com/eddyxu/cpp-coveralls/issues/108 by manually
 # installing the pyOpenSSL module and injecting it into urllib3 as per
 # https://urllib3.readthedocs.io/en/latest/user-guide.html#ssl-py2
-sed -i -e '/^import sys$/a import urllib3.contrib.pyopenssl\nurllib3.contrib.pyopenssl.inject_into_urllib3()' `which coveralls`
+#sed -i -e '/^import sys$/a import urllib3.contrib.pyopenssl\nurllib3.contrib.pyopenssl.inject_into_urllib3()' `which coveralls`
 
 coveralls -t d9uGTP4NSD092kh2b85aDSsEDxatcYC6F --include src/

configure.ac

@@ -77,6 +77,23 @@ AM_PATH_PYTHON([2.7])
 
 PKG_PROG_PKG_CONFIG
 
+AC_ARG_ENABLE([cfi],
+  [AS_HELP_STRING([--enable-cfi], [Turn on clang's Control Flow Integrity (CFI) (for developers)])],
+  [
+    clang_cfi=$enableval;
+    if test "$enableval" = yes; then
+      CFLAGS=$CFLAGS" -B/usr/bin/gold -fsanitize=cfi -flto -fvisibility=default -fno-sanitize-trap=all"
+      AC_LINK_IFELSE([
+        AC_LANG_PROGRAM([], [])
+      ], [], [
+        AC_MSG_ERROR([clang 3.7+ and the 'gold' linker are required for --enable-cfi])
+      ])
+    else
+      clang_cfi=no
+    fi
+  ],
+  [clang_cfi=no])
+
 # Define these substitions here to keep all version information in one place.
 # For information on how to properly maintain the library version information,
 # refer to the libtool manual, section "Updating library version information":
@@ -287,6 +304,7 @@ AC_MSG_NOTICE([Summary of build options:
   CFlags:            ${CFLAGS} ${CPPFLAGS}
   LDFlags:           ${LDFLAGS}
   Libs:              ${LIBS}
+  CFI:               ${clang_cfi}
   Runtime:           ${enable_runtime}
   Builtin:           ${enable_builtin}
   PSL Dist File:     ${PSL_DISTFILE}

contrib/check-hard

@@ -43,6 +43,9 @@ for CC in gcc clang; do
   "--enable-runtime=libidn --enable-builtin=libidn" \
   "--disable-runtime --enable-builtin=libicu"; do
     export DISTCHECK_CONFIGURE_FLAGS="-C --cache-file=$CACHEFILE $options"
+    if test "$CC" == "clang"; then
+      export DISTCHECK_CONFIGURE_FLAGS=$DISTCHECK_CONFIGURE_FLAGS" --enable-cfi"
+    fi
     echo
     echo "  *** ./configure $DISTCHECK_CONFIGURE_FLAGS"
     ./configure $DISTCHECK_CONFIGURE_FLAGS CFLAGS="$CFLAGS" > /dev/null

fuzz/Makefile.am

@@ -1,7 +1,8 @@
 AM_CFLAGS = $(WERROR_CFLAGS) $(WARN_CFLAGS) -Wno-unused-parameter
 AM_CPPFLAGS = -I$(top_srcdir)/include -I$(srcdir) -DSRCDIR=\"$(abs_srcdir)\" -DTEST_RUN
-AM_LDFLAGS = -static
+#AM_LDFLAGS = -static
-LDADD = ../src/libpsl.la
+AM_LDFLAGS = -no-install
+LDADD = ../src/libpsl.la $(LIBICU_LIBS) $(LIBIDN_LIBS) $(LIBIDN2_LIBS)
 
 PSL_TESTS = \
  libpsl_fuzzer$(EXEEXT) \

fuzz/README.md

@@ -65,3 +65,12 @@ To work on corpora for better coverage, `cd fuzz` and use e.g.
 
 Each reproducer file should be dropped into the appropriate *.repro/
 directory.
+
+
+# Clang CFI instrumentation
+```
+CC=clang-5.0 CFLAGS="-B/usr/bin/gold -O0 -fsanitize=cfi -flto -fvisibility=default -fno-sanitize-trap=all" ./configure
+make clean
+make
+make check
+```

tests/Makefile.am

@@ -1,6 +1,7 @@
 DEFS = @DEFS@ -DSRCDIR=\"$(srcdir)\" -DPSL_FILE=\"$(PSL_FILE)\" -DPSL_TESTFILE=\"$(PSL_TESTFILE)\"
 AM_CPPFLAGS = -I$(top_srcdir)/include
 LDADD = ../src/libpsl.la
+AM_LDFLAGS = -no-install
 
 # ./configure'd with '--disable-builtin'
 # Do not call test-is-public-builtin here: it does not make sense.