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security: Add max_length to zlib.decompress in uworker_io.py to prevent decompression bomb DoS #5334

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security: Add max_length to zlib.decompress in uworker_io.py to prevent decompression bomb DoS #5334

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13 changes: 10 additions & 3 deletions src/clusterfuzz/_internal/bot/tasks/utasks/uworker_io.py
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,11 @@
import uuid
import zlib

# Maximum decompressed size for uworker messages (256 MB).
# Prevents a malicious or compromised uworker from causing an OOM
# on the trusted tworker via a zlib decompression bomb.
_MAX_UWORKER_MSG_SIZE = 256 * 1024 * 1024

from google.cloud import ndb
from google.cloud.datastore_v1.types import entity as entity_pb2
from google.cloud.ndb import model
Expand Down Expand Up @@ -126,7 +131,7 @@ def download_and_deserialize_uworker_input(
download URL."""
data = storage.download_signed_url(uworker_input_download_url)
try:
data = zlib.decompress(data)
data = zlib.decompress(data, max_length=_MAX_UWORKER_MSG_SIZE)
except zlib.error:
# This is for backward compatiblity during the merge.
# TOOD(metzman): Remove backward compatibility efforts when every
Expand Down Expand Up @@ -167,7 +172,8 @@ def download_input_based_on_output_url(
input_url = uworker_output_path_to_input_path(output_url)
data = storage.read_data(input_url)
try:
serialized_uworker_input = zlib.decompress(data)
serialized_uworker_input = zlib.decompress(
data, max_length=_MAX_UWORKER_MSG_SIZE)
except zlib.error:
# For backwards compatability support uncompressed.
serialized_uworker_input = data
Expand All @@ -181,7 +187,8 @@ def download_and_deserialize_uworker_output(
"""Downloads and deserializes uworker output."""
data = storage.read_data(output_url)
try:
serialized_uworker_output = zlib.decompress(data)
serialized_uworker_output = zlib.decompress(
data, max_length=_MAX_UWORKER_MSG_SIZE)
except zlib.error:
# For backwards compatability support uncompressed.
serialized_uworker_output = data
Expand Down