ENH: Tolerate PDF with invalid xref pointed objects (#2335)

Closes #2326

pypdf/_reader.py

@@ -573,6 +573,25 @@ def read(self, stream: StreamType) -> None:
  # non-zero-index is actually correct
  stream.seek(loc, 0) # return to where it was
 
+ # remove wrong objects (not pointing to correct structures) - cf #2326
+ if not self.strict:
+ loc = stream.tell()
+ for gen, xref_entry in self.xref.items():
+ if gen == 65535:
+ continue
+ ids = list(xref_entry.keys())
+ for id in ids:
+ stream.seek(xref_entry[id], 0)
+ try:
+ self.read_object_header(stream)
+ except ValueError:
+ logger_warning(
+ f"Ignoring wrong pointing object {id} {gen} (offset {xref_entry[id]})",
+ __name__,
+ )
+ del xref_entry[id] # we can delete the id, we are parsing ids
+ stream.seek(loc, 0) # return to where it was
+
  def _basic_validation(self, stream: StreamType) -> None:
  """Ensure file is not empty. Read at most 5 bytes."""
  stream.seek(0, os.SEEK_SET)

tests/test_reader.py

@@ -268,7 +268,9 @@ def test_get_images(src, expected_images):
  False,
  -1,
  False,
- ["startxref on same line as offset"],
+ [
+ "startxref on same line as offset",
+ ],
  ),
  (
  False,
@@ -322,11 +324,12 @@ def test_get_images_raw(
  b"%%%%EOF"
  )
  pdf_data = pdf_data % (
- pdf_data.find(b"1 0 obj"),
- pdf_data.find(b"2 0 obj"),
- pdf_data.find(b"3 0 obj"),
- pdf_data.find(b"4 0 obj"),
- pdf_data.find(b"5 0 obj"),
+ # - 1 below in the find because of the double %
+ pdf_data.find(b"1 0 obj") - 1,
+ pdf_data.find(b"2 0 obj") - 1,
+ pdf_data.find(b"3 0 obj") - 1,
+ pdf_data.find(b"4 0 obj") - 1,
+ pdf_data.find(b"5 0 obj") - 1,
  b"/Prev 0 " if with_prev_0 else b"",
  # startx_correction should be -1 due to double % at the beginning
  # inducing an error on startxref computation
@@ -593,11 +596,11 @@ def test_read_unknown_zero_pages(caplog):
  b"%%%%EOF"
  )
  pdf_data = pdf_data % (
- pdf_data.find(b"1 0 obj"),
- pdf_data.find(b"2 0 obj"),
- pdf_data.find(b"3 0 obj"),
- pdf_data.find(b"4 0 obj"),
- pdf_data.find(b"5 0 obj"),
+ pdf_data.find(b"1 0 obj") - 1,
+ pdf_data.find(b"2 0 obj") - 1,
+ pdf_data.find(b"3 0 obj") - 1,
+ pdf_data.find(b"4 0 obj") - 1,
+ pdf_data.find(b"5 0 obj") - 1,
  pdf_data.find(b"xref") - 1,
  )
  pdf_stream = io.BytesIO(pdf_data)

tests/test_workflows.py

@@ -547,7 +547,11 @@ def test_get_fields_warns(tmp_path, caplog, url, name):
  retrieved_fields = reader.get_fields(fileobj=fp)
 
  assert retrieved_fields == {}
- assert normalize_warnings(caplog.text) == ["Object 2 0 not defined."]
+ assert normalize_warnings(caplog.text) == [
+ "Ignoring wrong pointing object 1 65536 (offset 0)",
+ "Ignoring wrong pointing object 2 65536 (offset 0)",
+ "Object 2 0 not defined.",
+ ]
 
 
 @pytest.mark.enable_socket()