Added fuzzer to be run with OSS-Fuzz

.coveragerc

@@ -2,4 +2,4 @@
 [run]
 branch = True
 source = jsonschema
-omit = */jsonschema/_reflect.py,*/jsonschema/__main__.py,*/jsonschema/benchmarks/*
+omit = */jsonschema/_reflect.py,*/jsonschema/__main__.py,*/jsonschema/benchmarks/*,*/jsonschema/tests/fuzz_validate.py

.github/workflows/fuzz.yml

@@ -0,0 +1,31 @@
+name: CIFuzz
+
+on:
+  pull_request:
+    branches:
+      - main
+
+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'
+        language: python
+      # Needed until google/oss-fuzz#4996 is merged
+      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
+    - 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 +1,47 @@
+"""
+Fuzzing setup for OSS-Fuzz.
+
+See https://github.com/google/oss-fuzz/tree/master/projects/jsonschema for the
+other half of the setup here.
+"""
+import sys
+
+from hypothesis import given, strategies
+
+import jsonschema
+
+PRIM = strategies.one_of(
+    strategies.booleans(),
+    strategies.integers(),
+    strategies.floats(allow_nan=False, allow_infinity=False),
+    strategies.text(),
+)
+DICT = strategies.recursive(
+    base=(
+        strategies.booleans()
+        | strategies.dictionaries(strategies.text(), PRIM),
+    ),
+    extend=lambda inner: strategies.dictionaries(strategies.text(), inner),
+)
+
+
+@given(obj1=DICT, obj2=DICT)
+def test_schemas(obj1, obj2):
+    try:
+        jsonschema.validate(instance=obj1, schema=obj2)
+    except jsonschema.exceptions.ValidationError:
+        pass
+    except jsonschema.exceptions.SchemaError:
+        pass
+
+
+def main():
+    atheris.Setup(sys.argv,
+                  test_schemas.hypothesis.fuzz_one_input,
+                  enable_python_coverage=True)
+    atheris.Fuzz()
+
+
+if __name__ == "__main__":
+    import atheris
+    main()