Add libfuzzer integration for libsignal-protocol-c

Now building and running the tests will create a new `fuzzer` target that
fuzzes deserialization and decryption with libfuzzer. As part of ctest
this will automatically run for 2048 iterations (takes 3 seconds on my
computer) in order to ensure that the fuzzer stays up to date. The fuzzer
can be run manually in order to fuzz for more iterations.

I've run this fuzzer for ~10 million iterations on my own computer and have
not found anything yet. But, my ultimate goal with this PR is to integrate
this repository with OSSFuzz per signalapp#136.

Note that tests/fuzzing_corpus/ includes an initial corpus for fuzzing so
that the fuzzer has somewhere to start. This was seeded with a couple of
valid serialized ciphertexts but the majority of it was synthesized by the
fuzzer over time.

tests/CMakeLists.txt

@@ -108,3 +108,23 @@ add_test(test_fingerprint ${TEST_PATH}/test_fingerprint)
 add_executable(test_device_consistency test_device_consistency.c ${common_SRCS})
 target_link_libraries(test_device_consistency ${LIBS})
 add_test(test_device_consistency ${TEST_PATH}/test_device_consistency)
+
+# Build the fuzzer executable
+find_package(Check 0.9.10 REQUIRED)
+find_package(OpenSSL 1.0 REQUIRED)
+set(LIBS 
+	${CHECK_LDFLAGS}
+	${OPENSSL_LIBRARIES}
+	signal-protocol-c
+)
+add_executable(fuzzer "fuzz_target.c" "test_common_openssl.c")
+target_link_libraries(fuzzer ${LIBS})
+set_target_properties(fuzzer
+	PROPERTIES COMPILE_FLAGS "-fsanitize=fuzzer-no-link,address"
+)
+set_target_properties(fuzzer
+	PROPERTIES LINK_FLAGS "-fsanitize=fuzzer,address -z muldefs"
+)
+
+# And run it for 2048 iterations as part of the test suite (should take at most a few seconds) to ensure it works
+add_test(test_fuzzer ${TEST_PATH}/fuzzer -use_value_profile=1 -use_memmem=1 -use_cmp=1 -runs=2048)

tests/fuzz_target.c

@@ -0,0 +1,138 @@
+#include "../src/protocol.c"
+#include "../src/protocol.h"
+#include "../src/session_builder.h"
+#include "../src/session_cipher.h"
+#include "../src/signal_protocol.h"
+#include "test_common.c"
+#include "test_common.h"
+#include <assert.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
+signal_context *global_context;
+
+static signal_protocol_address alice_address = {"+14159998888", 12, 1};
+
+static signal_protocol_address bob_address = {"+14151231234", 12, 1};
+
+ec_key_pair *bob_signed_pre_key;
+int32_t bob_signed_pre_key_id;
+
+// Fuzz the decrypt routine with Data and Size
+extern int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+  int result = 0;
+
+  // Create a new context
+  result = signal_context_create(&global_context, 0);
+  assert(result == 0);
+
+  // Set up a test crypto provider using OpenSSL
+  setup_test_crypto_provider(global_context);
+
+  // Create Bob's data store
+  signal_protocol_store_context *bob_store = 0;
+  setup_test_store_context(&bob_store, global_context);
+
+  // Register Bob
+  uint32_t bob_local_registration_id = 0;
+  result = signal_protocol_identity_get_local_registration_id(
+      bob_store, &bob_local_registration_id);
+  assert(result == 0);
+
+  // Create his keys
+  ec_key_pair *bob_pre_key_pair = 0;
+  result = curve_generate_key_pair(global_context, &bob_pre_key_pair);
+  assert(result == 0);
+
+  ec_key_pair *bob_signed_pre_key_pair = 0;
+  result = curve_generate_key_pair(global_context, &bob_signed_pre_key_pair);
+  assert(result == 0);
+
+  ratchet_identity_key_pair *bob_identity_key_pair = 0;
+  result = signal_protocol_identity_get_key_pair(bob_store, &bob_identity_key_pair);
+  assert(result == 0);
+
+  signal_buffer *bob_signed_pre_key_public_serialized = 0;
+  result = ec_public_key_serialize(&bob_signed_pre_key_public_serialized,
+                              ec_key_pair_get_public(bob_signed_pre_key_pair));
+  assert(result == 0);
+
+  signal_buffer *bob_signed_pre_key_signature = 0;
+  result = curve_calculate_signature(
+      global_context, &bob_signed_pre_key_signature,
+      ratchet_identity_key_pair_get_private(bob_identity_key_pair),
+      signal_buffer_data(bob_signed_pre_key_public_serialized),
+      signal_buffer_len(bob_signed_pre_key_public_serialized));
+  assert(result == 0);
+
+  session_pre_key_bundle *bob_pre_key = 0;
+  result = session_pre_key_bundle_create(
+      &bob_pre_key, bob_local_registration_id, 
+      1,   /* device ID */
+      31337, /* pre key ID */
+      ec_key_pair_get_public(bob_pre_key_pair), 
+      22, /* signed pre key ID */
+      ec_key_pair_get_public(bob_signed_pre_key_pair),
+      signal_buffer_data(bob_signed_pre_key_signature),
+      signal_buffer_len(bob_signed_pre_key_signature),
+      ratchet_identity_key_pair_get_public(bob_identity_key_pair));
+  assert(result == 0);
+
+  // And add Bob's pre keys to his data store 
+  session_pre_key *bob_pre_key_record = 0;
+  result = session_pre_key_create(
+      &bob_pre_key_record, session_pre_key_bundle_get_pre_key_id(bob_pre_key),
+      bob_pre_key_pair);
+  assert(result == 0);
+
+  result = signal_protocol_pre_key_store_key(bob_store, bob_pre_key_record);
+  assert(result == 0);
+
+  session_signed_pre_key *bob_signed_pre_key_record = 0;
+  result = session_signed_pre_key_create(
+      &bob_signed_pre_key_record, 22, time(0), bob_signed_pre_key_pair,
+      signal_buffer_data(bob_signed_pre_key_signature),
+      signal_buffer_len(bob_signed_pre_key_signature));
+  assert(result == 0);
+
+  result = signal_protocol_signed_pre_key_store_key(bob_store,
+                                                    bob_signed_pre_key_record);
+  assert(result == 0);
+
+  session_cipher *bob_session_cipher = 0;
+  result = session_cipher_create(&bob_session_cipher, bob_store, &alice_address,
+                                 global_context);
+  assert(result == 0);
+
+  // Start of the actual fuzzing, attempt to deserialize the input data
+  pre_key_signal_message *incoming_message_bad = 0;
+  result = pre_key_signal_message_deserialize(
+      &incoming_message_bad, Data, Size, global_context);
+  if (result != 0) {
+    goto done;
+  }
+
+  // And if it deserialized okay, then decrypt it 
+  signal_buffer *plaintext = 0;
+  result = session_cipher_decrypt_pre_key_signal_message(
+      bob_session_cipher, incoming_message_bad, 0, &plaintext);
+
+  // Then free everything 
+  signal_buffer_free(plaintext);
+done:
+  session_cipher_free(bob_session_cipher);
+  SIGNAL_UNREF(incoming_message_bad);
+  SIGNAL_UNREF(bob_pre_key);
+  SIGNAL_UNREF(bob_pre_key_pair);
+  SIGNAL_UNREF(bob_signed_pre_key_pair);
+  SIGNAL_UNREF(bob_identity_key_pair);
+  SIGNAL_UNREF(bob_signed_pre_key_record);
+  SIGNAL_UNREF(bob_pre_key_record);
+  signal_buffer_free(bob_signed_pre_key_public_serialized);
+  signal_buffer_free(bob_signed_pre_key_signature);
+  signal_protocol_store_context_destroy(bob_store);
+  signal_context_destroy(global_context);
+
+  return 0;
+}

tests/fuzzing_corpus/1114fc59b3d34dc14c751ac4197e83ae806279c9

@@ -0,0 +1 @@
+�b��

tests/fuzzing_corpus/2dbfc8db8813b6a5ddd2d2213c9b5f4bc7c9bf86

@@ -0,0 +1 @@
+3!�u��$7�#�J��Lq�UpEς׫�.��N!Tl�'�����R��{���D��6|�F��f�"#1�|������&5ē���<��@@���R��{��}0

tests/fuzzing_corpus/30ac69e3dabf0406926ccdfc1cd69895fc27b225

@@ -0,0 +1 @@
+p33

tests/fuzzing_corpus/4befa5410a3f027099d8e4457031a063c04cca78

@@ -0,0 +1 @@
+p

tests/fuzzing_corpus/6c7538fa04ef67015b578f7eb47d22e10c7f257f

@@ -0,0 +1 @@
+:x

tests/fuzzing_corpus/6d143d74defecd65e92483b19d4387d582626e01

@@ -0,0 +1 @@
+>07

tests/fuzzing_corpus/8055db73d78783ce3787c1bf2a1e05ed440d1a3d

@@ -0,0 +1 @@
+��

tests/fuzzing_corpus/97a7cb37d735cfd4558c1c872f689ee721a4c72c

@@ -0,0 +1 @@
+/�

tests/fuzzing_corpus/adc83b19e793491b1c6ea0fd8b46cd9f32e592fc

@@ -0,0 +1 @@
+

tests/fuzzing_corpus/f70eaf8d76e1326bb3a7323c7902a11fc75b5b5d

@@ -0,0 +1 @@
+�������������������������������������������������������������������������������������������������������������������������*

tests/fuzzing_corpus/fabe29cae4c17ab9174674894e0c45ac1a844533

@@ -0,0 +1 @@
+1c

tests/test_common.c

@@ -3,6 +3,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <check.h>
+#include <assert.h>
 
 #include "../src/signal_protocol.h"
 #include "curve.h"
@@ -169,7 +170,7 @@ void setup_test_store_context(signal_protocol_store_context **context, signal_co
 
     signal_protocol_store_context *store_context = 0;
     result = signal_protocol_store_context_create(&store_context, global_context);
-    ck_assert_int_eq(result, 0);
+    assert(result == 0);
 
     setup_test_session_store(store_context);
     setup_test_pre_key_store(store_context);