OSS-Fuzz initial integration (#1030)

* OSS-Fuzz initial integration

---------

Co-authored-by: bcapuano <[email protected]>

dev/fuzzing/build.sh

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+cd "$SRC"/XlsxWriter
+pip3 install .
+
+# Build fuzzers in $OUT
+for fuzzer in $(find dev/fuzzing -name '*_fuzzer.py');do
+  compile_python_fuzzer "$fuzzer"
+done
+zip -q $OUT/xlsx_fuzzer_seed_corpus.zip $SRC/corpus/*

dev/fuzzing/corpus/test_corpus

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+=IF(A1 > B1, A1 * 1.5, B1 * 2)

dev/fuzzing/fuzz_helpers.py

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+import io
+import tempfile
+import atheris
+import contextlib
+from typing import List, Set, Dict, Tuple, Any
+
+
+class EnhancedFuzzedDataProvider(atheris.FuzzedDataProvider):
+    def ConsumeRandomBytes(self) -> bytes:
+        return self.ConsumeBytes(self.ConsumeIntInRange(0, self.remaining_bytes()))
+
+    def ConsumeRandomString(self) -> str:
+        return self.ConsumeUnicodeNoSurrogates(self.ConsumeIntInRange(0, self.remaining_bytes()))
+
+    def ConsumeRemainingString(self) -> str:
+        return self.ConsumeUnicodeNoSurrogates(self.remaining_bytes())
+
+    def ConsumeRemainingBytes(self) -> bytes:
+        return self.ConsumeBytes(self.remaining_bytes())
+
+    @contextlib.contextmanager
+    def ConsumeMemoryFile(self, all_data: bool = False, as_bytes: bool = True) -> io.BytesIO:
+        if all_data:
+            file_data = self.ConsumeRemainingBytes() if as_bytes else self.ConsumeRemainingString()
+        else:
+            file_data = self.ConsumeRandomBytes() if as_bytes else self.ConsumeRandomString()
+
+        file = io.BytesIO(file_data) if as_bytes else io.StringIO(file_data)
+        yield file
+        file.close()
+
+    @contextlib.contextmanager
+    def ConsumeTemporaryFile(self, suffix: str, all_data: bool = False, as_bytes: bool = True) -> str:
+        if all_data:
+            file_data = self.ConsumeRemainingBytes() if as_bytes else self.ConsumeRemainingString()
+        else:
+            file_data = self.ConsumeRandomBytes() if as_bytes else self.ConsumeRandomString()
+
+        mode = 'w+b' if as_bytes else 'w+'
+        tfile = tempfile.NamedTemporaryFile(mode=mode, suffix=suffix)
+        tfile.write(file_data)
+        tfile.seek(0)
+        tfile.flush()
+        yield tfile.name
+        tfile.close()

dev/fuzzing/xlsx_fuzzer.py

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+from enum import Enum
+
+import atheris
+import sys
+from io import BytesIO
+
+from fuzz_helpers import EnhancedFuzzedDataProvider
+import struct
+
+with atheris.instrument_imports(include=['xlsxwriter']):
+    import xlsxwriter
+    import xlsxwriter.worksheet
+    from xlsxwriter.exceptions import XlsxWriterException
+
+
+class FuncChoice(Enum):
+    WRITE_STRING = 0
+    WRITE_NUMBER = 1
+    WRITE_FORMULA = 2
+
+
+choices = [FuncChoice.WRITE_STRING, FuncChoice.WRITE_NUMBER, FuncChoice.WRITE_FORMULA]
+
+
+def TestOneInput(data):
+    fdp = EnhancedFuzzedDataProvider(data)
+
+    try:
+        out = BytesIO()
+        with xlsxwriter.Workbook(out) as wb:
+            ws = wb.add_worksheet()
+
+            data = fdp.ConsumeRandomString()
+            func_choice = fdp.PickValueInList(choices)
+
+            for row in range(fdp.ConsumeIntInRange(0, 10)):
+                for col in range(fdp.ConsumeIntInRange(0, 10)):
+                    if func_choice is FuncChoice.WRITE_STRING:
+                        ws.write_string(row, col, data)
+                    elif func_choice is FuncChoice.WRITE_NUMBER:
+                        ws.write_number(row, col, data)
+                    else:
+                        ws.write_formula(row, col, data)
+    except (XlsxWriterException, struct.error):
+        return -1
+    except TypeError as e:
+        if 'must be real number' in str(e):
+            return -1
+        raise e
+
+
+def main():
+    atheris.Setup(sys.argv, TestOneInput)
+    atheris.Fuzz()
+
+
+if __name__ == "__main__":
+    main()