First attempt at a Python fuzzer.

Using the following as a guide:
https://google.github.io/oss-fuzz/getting-started/new-project-guide/python-lang/

PiperOrigin-RevId: 351239322
Change-Id: I91df8559d00f00e35ffdaec0960abe1b0a4462b1

tensorflow/security/fuzzing/BUILD

@@ -5,6 +5,7 @@
 load(
     "//tensorflow/security/fuzzing:tf_fuzzing.bzl",
     "tf_fuzz_target",
+    "tf_py_fuzz_target",
 )
 
 package(
@@ -127,3 +128,12 @@ tf_fuzz_target(
         "//tensorflow/core/platform:stringpiece",
     ],
 )
+
+tf_py_fuzz_target(
+    name = "constant_fuzz",
+    srcs = ["constant_fuzz.py"],
+    tags = ["notap"],  # Run in OSS only.
+    deps = [
+        "//tensorflow/python:constant_op",
+    ],
+)

tensorflow/security/fuzzing/constant_fuzz.py

@@ -0,0 +1,31 @@
+# Copyright 2020 The TensorFlow Authors. All Rights Reserved.
+#
+# 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.
+# ==============================================================================
+"""This is a Python API fuzzer for tf.constant."""
+import sys
+import atheris_no_libfuzzer as atheris
+from tensorflow.python.framework import constant_op
+
+
+def TestOneInput(data):
+  constant_op.constant(data)
+
+
+def main():
+  atheris.Setup(sys.argv, TestOneInput, enable_python_coverage=True)
+  atheris.Fuzz()
+
+
+if __name__ == "__main__":
+  main()

tensorflow/security/fuzzing/tf_fuzzing.bzl

@@ -79,3 +79,63 @@ def tf_fuzz_target(
         linkstatic = 1,
         **kwargs
     )
+
+# tf_py_fuzz_target is a py_test modified to include fuzzing support.
+def tf_py_fuzz_target(
+        name,
+        # Fuzzing specific arguments
+        fuzzing_dict = [],
+        corpus = [],
+        parsers = [],
+        # Reporting bugs arguments, not used in open source
+        componentid = None,
+        hotlists = [],
+        # Additional py_test control
+        data = [],
+        deps = [],
+        tags = [],
+        # Remaining py_test arguments
+        **kwargs):
+    """Specify how to build a TensorFlow Python fuzz target.
+
+    Args:
+      name: Mandatory name of the fuzzer target.
+
+      fuzzing_dict: An optional a set of dictionary files following
+        the AFL/libFuzzer dictionary syntax.
+
+      corpus: An optional set of files used as the initial test corpus
+        for the target. When doing "bazel test" in the default null-fuzzer
+        (unittest) mode, these files are automatically passed to the target
+        function.
+
+      parsers: An optional list of file extensions that the target supports.
+        Used by tools like autofuzz to reuse corpus sets across targets.
+
+      componentid: Used internally for reporting fuzz discovered bugs.
+
+      hotlists: Used internally for reporting fuzz discovered bugs.
+
+      data: Additional data dependencies passed to the underlying py_test rule.
+
+      deps: An optional list of dependencies for the code you're fuzzing.
+
+      tags: Additional tags passed to the underlying py_test rule.
+
+      **kwargs: Collects all remaining arguments and passes them to the
+        underlying py_test rule generated by the macro.
+    """
+    componentid = None
+    hotlists = None
+
+    # Fuzzers in open source must be run manually
+    tags = tags + ["manual"]
+
+    # Now, redirect to py_test
+    native.py_test(
+        name = name,
+        deps = deps,
+        data = data,
+        tags = tags,
+        **kwargs
+    )