Added fuzzer to be run with OSS-Fuzz

.github/workflows/main.yml

@@ -0,0 +1,26 @@
+name: CIFuzz
+on: [pull_request]
+jobs:
+  Fuzzing:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Build Fuzzers
+      id: build
+      uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@master
+      with:
+        oss-fuzz-project-name: 'jsonschema'
+        dry-run: false
+      continue-on-error: true
+    - name: Run Fuzzers
+      if: steps.build.outcome == 'success'
+      uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@master
+      with:
+        oss-fuzz-project-name: 'jsonschema'
+        fuzz-seconds: 30
+        dry-run: false
+    - name: Upload Crash
+      uses: actions/upload-artifact@v1
+      if: failure() && steps.build.outcome == 'success'
+      with:
+        name: artifacts
+        path: ./out/artifacts

jsonschema/tests/fuzz_validate.py

@@ -0,0 +1,39 @@
+import sys
+
+from hypothesis import given
+from hypothesis import strategies as st
+import atheris
+
+import jsonschema
+
+PRIM = st.one_of(
+    st.booleans(),
+    st.integers(min_value=-(2 ** 63), max_value=2 ** 63 - 1),
+    st.floats(allow_nan=False, allow_infinity=False),
+    st.text(),
+)
+DICT = st.recursive(
+    base=st.dictionaries(st.text(), PRIM),
+    extend=lambda inner: st.dictionaries(st.text(), inner),
+)
+
+
+@given(obj1=DICT, obj2=DICT)
+def test_schemas(obj1, obj2):
+    try:
+        jsonschema.validate(instance=obj1, schema=obj2)
+    except jsonschema.exceptions.ValidationError:
+        None
+    except jsonschema.exceptions.SchemaError:
+        None
+
+
+def main():
+    atheris.Setup(sys.argv,
+                  test_schemas.hypothesis.fuzz_one_input,
+                  enable_python_coverage=True)
+    atheris.Fuzz()
+
+
+if __name__ == "__main__":
+    main()