pyyaml: add emitter fuzzer (#9689)

Signed-off-by: David Korczynski <david@adalogics.com>

Signed-off-by: David Korczynski <david@adalogics.com>

projects/pyyaml/fuzz_emitter.py

@@ -0,0 +1,45 @@
+#!/usr/bin/python3
+# Copyright 2023 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.
+"""Targets primarily code in lib/yaml/emitter.py. """
+import sys
+import atheris
+
+import io
+import yaml
+
+def TestOneInput(data):
+  try:
+    events = list(yaml.parse(io.BytesIO(data)))
+  except yaml.YAMLError:
+    return
+  except RecursionError:
+    return
+  try:
+    output = yaml.emit(events)
+  except yaml.emitter.EmitterError:
+    return
+  except RecursionError:
+    return
+
+  # At this point the output should be good to parse cleanly.
+  yaml.parse(output)
+
+def main():
+  atheris.instrument_all()
+  atheris.Setup(sys.argv, TestOneInput)
+  atheris.Fuzz()
+
+if __name__ == "__main__":
+  main()