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ROB: Raise proper error on infinite loop when reading objects #3169

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Mar 7, 2025
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ROB: Raise proper error on infinite loop when reading objects #3169

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8 changes: 8 additions & 0 deletions pypdf/_reader.py
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,7 @@
Iterable,
List,
Optional,
Set,
Tuple,
Type,
Union,
Expand Down Expand Up @@ -133,6 +134,7 @@ def __init__(
self._validated_root: Optional[DictionaryObject] = None

self._initialize_stream(stream)
self._known_objects: Set[Tuple[int, int]] = set()

self._override_encryption = False
self._encryption: Optional[Encryption] = None
Expand Down Expand Up @@ -447,7 +449,13 @@ def get_object(
)
if self.strict:
assert generation == indirect_reference.generation

current_object = (indirect_reference.idnum, indirect_reference.generation)
if current_object in self._known_objects:
raise PdfReadError(f"Detected loop with self reference for {indirect_reference!r}.")
self._known_objects.add(current_object)
retval = read_object(self.stream, self) # type: ignore
self._known_objects.remove(current_object)

# override encryption is used for the /Encrypt dictionary
if not self._override_encryption and self._encryption is not None:
Expand Down
12 changes: 12 additions & 0 deletions tests/test_reader.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1806,3 +1806,15 @@ def test_issue2886(caplog):

with pytest.raises(PdfReadError, match="Unexpected empty line in Xref table."):
_ = PdfReader(BytesIO(get_data_from_url(url, name=name)))


@pytest.mark.enable_socket
def test_infinite_loop_for_length_value():
"""Tests for #3112"""
url = "https://github.com/user-attachments/files/19106009/Special.n.15.du.jeudi.22.fevrier.2024.pdf"
name = "issue3112.pdf"

reader = PdfReader(BytesIO(get_data_from_url(url, name=name)))
writer = PdfWriter()
with pytest.raises(PdfReadError, match=r"^Detected loop with self reference for IndirectObject\(165, 0, \d+\)\.$"):
writer.add_page(reader.pages[0])
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