fix: wrap corrupt/truncated/encrypted zip read errors in PackageNotFoundError

src/docx/opc/phys_pkg.py

@@ -1,7 +1,8 @@
 """Provides a general interface to a `physical` OPC package, such as a zip file."""
 
 import os
-from zipfile import ZIP_DEFLATED, ZipFile, is_zipfile
+import zlib
+from zipfile import ZIP_DEFLATED, BadZipFile, ZipFile, is_zipfile
 
 from docx.opc.exceptions import PackageNotFoundError
 from docx.opc.packuri import CONTENT_TYPES_URI
@@ -73,14 +74,24 @@ class _ZipPkgReader(PhysPkgReader):
 
     def __init__(self, pkg_file):
         super(_ZipPkgReader, self).__init__()
-        self._zipf = ZipFile(pkg_file, "r")
+        try:
+            self._zipf = ZipFile(pkg_file, "r")
+        except BadZipFile as e:
+            raise PackageNotFoundError("Package is not a valid zip file: %s" % e) from e
 
     def blob_for(self, pack_uri):
         """Return blob corresponding to `pack_uri`.
 
         Raises |ValueError| if no matching member is present in zip archive.
+        Raises |PackageNotFoundError| if the zip entry cannot be read due to corruption,
+        truncation, or encryption.
         """
-        return self._zipf.read(pack_uri.membername)
+        try:
+            return self._zipf.read(pack_uri.membername)
+        except (BadZipFile, zlib.error, EOFError, RuntimeError) as e:
+            raise PackageNotFoundError(
+                "Package member '%s' could not be read: %s" % (pack_uri.membername, e)
+            ) from e
 
     def close(self):
         """Close the zip archive, releasing any resources it is using."""

tests/opc/test_phys_pkg.py

@@ -2,7 +2,9 @@
 
 import hashlib
 import io
-from zipfile import ZIP_DEFLATED, ZipFile
+import struct
+import zlib
+from zipfile import ZIP_DEFLATED, BadZipFile, ZipFile
 
 import pytest
 
@@ -70,6 +72,50 @@ def it_raises_when_pkg_path_is_not_a_package(self):
 
 
 class DescribeZipPkgReader:
+    def it_raises_PackageNotFoundError_when_stream_is_not_a_zip(self):
+        with pytest.raises(PackageNotFoundError, match="not a valid zip file"):
+            _ZipPkgReader(io.BytesIO(b"not a zip file"))
+
+    def it_raises_PackageNotFoundError_when_blob_has_bad_crc(self):
+        """BadZipFile (CRC mismatch) from ZipFile.read() is wrapped."""
+        # Build a zip with a large enough payload, then flip a byte in the
+        # middle of the compressed data to cause a CRC mismatch at read time.
+        buf = io.BytesIO()
+        with ZipFile(buf, "w", compression=ZIP_DEFLATED) as zf:
+            zf.writestr("[Content_Types].xml", b"<Types/>" * 50)
+        raw = bytearray(buf.getvalue())
+        sig_pos = raw.find(b"PK\x03\x04")
+        fname_len = struct.unpack_from("<H", raw, sig_pos + 26)[0]
+        extra_len = struct.unpack_from("<H", raw, sig_pos + 28)[0]
+        data_start = sig_pos + 30 + fname_len + extra_len
+        compressed_size = struct.unpack_from("<I", raw, sig_pos + 18)[0]
+        mid = data_start + compressed_size // 2
+        raw[mid] ^= 0xFF
+        reader = _ZipPkgReader(io.BytesIO(bytes(raw)))
+        pack_uri = PackURI("/[Content_Types].xml")
+        with pytest.raises(PackageNotFoundError, match="could not be read"):
+            reader.blob_for(pack_uri)
+
+    def it_raises_PackageNotFoundError_when_zlib_data_is_corrupt(self):
+        """zlib.error from ZipFile.read() is wrapped in PackageNotFoundError."""
+        # Corrupt the zlib header bytes of the compressed payload so that
+        # decompression fails with zlib.error before the CRC is checked.
+        buf = io.BytesIO()
+        with ZipFile(buf, "w", compression=ZIP_DEFLATED) as zf:
+            zf.writestr("[Content_Types].xml", b"<Types/>" * 1000)
+        raw = bytearray(buf.getvalue())
+        sig_pos = raw.find(b"PK\x03\x04")
+        fname_len = struct.unpack_from("<H", raw, sig_pos + 26)[0]
+        extra_len = struct.unpack_from("<H", raw, sig_pos + 28)[0]
+        data_start = sig_pos + 30 + fname_len + extra_len
+        # Flip the first two bytes of the zlib stream (the zlib header).
+        raw[data_start] ^= 0xFF
+        raw[data_start + 1] ^= 0xFF
+        reader = _ZipPkgReader(io.BytesIO(bytes(raw)))
+        pack_uri = PackURI("/[Content_Types].xml")
+        with pytest.raises(PackageNotFoundError, match="could not be read"):
+            reader.blob_for(pack_uri)
+
     def it_is_used_by_PhysPkgReader_when_pkg_is_a_zip(self):
         phys_reader = PhysPkgReader(zip_pkg_path)
         assert isinstance(phys_reader, _ZipPkgReader)