fuzz: add basic fuzz testing target.

fuzz-pack-headers.c provides a fuzzing entry point compatible with
libFuzzer (and possibly other fuzzing engines).

Signed-off-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/.gitignore b/.gitignore
index 9d1363a1ebce8432c15f610aa7af9520e3e2bb12..87a28b3115f1412b3ad3a202c97cafd91dc7a8ee 100644 (file)
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,5 @@
+/fuzz_corpora
+/fuzz-pack-headers
 /GIT-BUILD-OPTIONS
 /GIT-CFLAGS
 /GIT-LDFLAGS

diff --git a/Makefile b/Makefile
index 13e1c5247824d8db94126cb91d35df57440c9384..7f5a19b8ab52188393c590a1ac98910372cd6dfa 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -590,6 +590,8 @@ XDIFF_OBJS =
 VCSSVN_OBJS =
 GENERATED_H =
 EXTRA_CPPFLAGS =
+FUZZ_OBJS =
+FUZZ_PROGRAMS =
 LIB_OBJS =
 PROGRAM_OBJS =
 PROGRAMS =
@@ -682,6 +684,13 @@ SCRIPTS = $(SCRIPT_SH_INS) \
 
 ETAGS_TARGET = TAGS
 
+FUZZ_OBJS += fuzz-pack-headers.o
+
+# Always build fuzz objects even if not testing, to prevent bit-rot.
+all:: $(FUZZ_OBJS)
+
+FUZZ_PROGRAMS += $(patsubst %.o,%,$(FUZZ_OBJS))
+
 # Empty...
 EXTRA_PROGRAMS =
 
@@ -2250,6 +2259,7 @@ TEST_OBJS := $(patsubst %$X,%.o,$(TEST_PROGRAMS)) $(patsubst %,t/helper/%,$(TEST
 OBJECTS := $(LIB_OBJS) $(BUILTIN_OBJS) $(PROGRAM_OBJS) $(TEST_OBJS) \
        $(XDIFF_OBJS) \
        $(VCSSVN_OBJS) \
+       $(FUZZ_OBJS) \
        common-main.o \
        git.o
 ifndef NO_CURL
@@ -2937,6 +2947,7 @@ clean: profile-clean coverage-clean cocciclean
        $(RM) $(LIB_FILE) $(XDIFF_LIB) $(VCSSVN_LIB)
        $(RM) $(ALL_PROGRAMS) $(SCRIPT_LIB) $(BUILT_INS) git$X
        $(RM) $(TEST_PROGRAMS) $(NO_INSTALL)
+       $(RM) $(FUZZ_PROGRAMS)
        $(RM) -r bin-wrappers $(dep_dirs)
        $(RM) -r po/build/
        $(RM) *.pyc *.pyo */*.pyc */*.pyo command-list.h $(ETAGS_TARGET) tags cscope*
@@ -3061,3 +3072,24 @@ cover_db: coverage-report
 cover_db_html: cover_db
        cover -report html -outputdir cover_db_html cover_db
 
+
+### Fuzz testing
+#
+# Building fuzz targets generally requires a special set of compiler flags that
+# are not necessarily appropriate for general builds, and that vary greatly
+# depending on the compiler version used.
+#
+# An example command to build against libFuzzer from LLVM 4.0.0:
+#
+# make CC=clang CXX=clang++ \
+#      CFLAGS="-fsanitize-coverage=trace-pc-guard -fsanitize=address" \
+#      LIB_FUZZING_ENGINE=/usr/lib/llvm-4.0/lib/libFuzzer.a \
+#      fuzz-all
+#
+.PHONY: fuzz-all
+
+$(FUZZ_PROGRAMS): all
+       $(QUIET_LINK)$(CXX) $(CFLAGS) $(LIB_OBJS) $(BUILTIN_OBJS) \
+               $(XDIFF_OBJS) $(EXTLIBS) git.o $@.o $(LIB_FUZZING_ENGINE) -o $@
+
+fuzz-all: $(FUZZ_PROGRAMS)

diff --git a/fuzz-pack-headers.c b/fuzz-pack-headers.c
new file mode 100644 (file)
index 0000000..99da1d0
--- /dev/null
+++ b/fuzz-pack-headers.c
@@ -0,0 +1,14 @@
+#include "packfile.h"
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
+{
+       enum object_type type;
+       unsigned long len;
+
+       unpack_object_header_buffer((const unsigned char *)data,
+                                   (unsigned long)size, &type, &len);
+
+       return 0;
+}