[pycryptodome] Additional Fuzzer (google#4339)

* initial commit

* update build script, build failing

* add necessary environment variable definitions

* build working

* programmatically get system bits

* add md5 fuzzer

* fix style

* add fuzzers for two more hash functions

* testing dynamic includes

* build working

* clean up build script

* add aes fuzzer

* patch block_common to avoid build issues

* remove comments

* update patchfile location

* move patchfile again

* apply patch from subdirectory

* remove another comment

* change state type, use same data for encryption and decryption

Author: rjotwani

projects/pycryptodome/Dockerfile

@@ -17,5 +17,6 @@
 FROM gcr.io/oss-fuzz-base/base-builder
 RUN apt-get update && apt-get install -y make autoconf automake libtool
 RUN git clone --depth 1 https://github.com/Legrandin/pycryptodome.git
-WORKDIR pycryptodome
+WORKDIR pycryptodome/src
 COPY build.sh *_fuzzer.cc $SRC/
+COPY block_common.patch $SRC/pycryptodome/src

projects/pycryptodome/block_common.patch

@@ -0,0 +1,12 @@
+diff --git a/src/block_common.c b/src/block_common.c
+index 169200a6..c6da1f85 100644
+--- a/src/block_common.c
++++ b/src/block_common.c
+@@ -106,7 +106,7 @@ EXPORT_SYM int CIPHER_START_OPERATION(const uint8_t key[], size_t key_len, CIPHE
+     if ((key == NULL) || (pResult == NULL))
+         return ERR_NULL;
+
+-    *pResult = calloc(1, sizeof(CIPHER_STATE_TYPE));
++    *pResult = (CIPHER_STATE_TYPE *) calloc(1, sizeof(CIPHER_STATE_TYPE));
+     if (NULL == *pResult)
+         return ERR_MEMORY;

projects/pycryptodome/build.sh

@@ -15,7 +15,9 @@
 #
 ################################################################################
 
-PCD_INTERNALS=(src/*.c src/libtom/*.c)
+patch block_common.c block_common.patch
+
+PCD_INTERNALS=(./*.c ./libtom/*.c)
 PCD_FLAGS=(
   "-I $SRC/pycryptodome/src"
   "-I $SRC/pycryptodome/src/libtom"
@@ -29,7 +31,7 @@ PCD_FLAGS=(
 $CC $CFLAGS \
     ${PCD_FLAGS[@]} \
     -c "${PCD_INTERNALS//'blake2.c'/}"
-ar -qc $WORK/libpycryptodome.a  *.o
+ar -qc $WORK/libpycryptodome.a *.o
 
 PCD_HASH_OPTIONS=(
   "-D HASHTYPE=md2 -D FNAME=MD2.c -D DIGEST_SIZE=16 -o $OUT/md2_fuzzer"
@@ -46,3 +48,7 @@ for ((i = 0; i < ${#PCD_HASH_OPTIONS[@]}; i++)); do
       $SRC/pcd_hash_fuzzer.cc ${PCD_HASH_OPTIONS[i]} \
       $LIB_FUZZING_ENGINE $WORK/libpycryptodome.a
 done
+
+$CXX $CXXFLAGS ${PCD_FLAGS[@]} \
+    $SRC/pcd_aes_fuzzer.cc -o $OUT/aes_fuzzer \
+    $LIB_FUZZING_ENGINE $WORK/libpycryptodome.a

projects/pycryptodome/pcd_aes_fuzzer.cc

@@ -0,0 +1,47 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "AES.c"
+#include "common.h"
+#include <fuzzer/FuzzedDataProvider.h>
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+
+  if (!size)
+    return 0;
+
+  enum KeySize { AES128 = 16, AES192 = 24, AES256 = 32, kMaxValue = AES256 };
+
+  FuzzedDataProvider stream(data, size);
+  const KeySize keySize = stream.ConsumeEnum<KeySize>();
+  if (stream.remaining_bytes() < keySize)
+    return 0;
+
+  std::vector<uint8_t> keyBuf = stream.ConsumeBytes<uint8_t>(keySize);
+  const uint8_t *key = keyBuf.data();
+
+  BlockBase *state;
+  if (AES_start_operation(key, keySize, reinterpret_cast<AES_State **>(&state)))
+    return 0;
+
+  uint8_t outEnc[size];
+  uint8_t outDec[size];
+
+  AES_encrypt(reinterpret_cast<BlockBase *>(state), data, outEnc, size);
+  AES_decrypt(reinterpret_cast<BlockBase *>(state), data, outDec, size);
+
+  AES_stop_operation(reinterpret_cast<BlockBase *>(state));
+
+  return 0;
+}