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Add detection for recursive decompression bombs #52

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Add detection for recursive decompression bombs #52

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19 changes: 18 additions & 1 deletion src/extractcode/extract.py
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@

from commoncode import fileutils
from commoncode import ignore
from commoncode import hash

import extractcode # NOQA
import extractcode.archive
Expand Down Expand Up @@ -86,6 +87,7 @@ def extract(
recurse=False,
replace_originals=False,
ignore_pattern=(),
known_archive_hashes=set()
):
"""
Walk and extract any archives found at ``location`` (either a file or
Expand Down Expand Up @@ -121,6 +123,7 @@ def extract(
kinds=kinds,
recurse=recurse,
ignore_pattern=ignore_pattern,
known_archive_hashes=known_archive_hashes
)

processed_events = []
Expand Down Expand Up @@ -151,6 +154,7 @@ def extract_files(
kinds=extractcode.default_kinds,
recurse=False,
ignore_pattern=(),
known_archive_hashes=set()
):
"""
Extract the files found at `location`.
Expand Down Expand Up @@ -190,7 +194,7 @@ def extract_files(
if not recurse and extractcode.is_extraction_path(loc):
if TRACE:
logger.debug(
'extract:walk not recurse: skipped file: %(loc)r' % locals())
'extract:walk: not recurse: skipped file: %(loc)r' % locals())
continue

if not extractcode.archive.should_extract(
Expand All @@ -203,6 +207,14 @@ def extract_files(
'extract:walk: skipped file: not should_extract: %(loc)r' % locals())
continue

file_hash = hash.sha256(loc)

if known_archive_hashes and file_hash in known_archive_hashes:
if TRACE:
logger.debug(
'extract:walk: skipped file: decompression bomb detected: %(loc)r' % locals())
continue

target = join(abspath(top), extractcode.get_extraction_path(loc))
if TRACE:
logger.debug('extract:target: %(target)r' % locals())
Expand All @@ -220,11 +232,16 @@ def extract_files(
if recurse:
if TRACE:
logger.debug('extract:walk: recursing on target: %(target)r' % locals())

kah = set(known_archive_hashes)
kah.add(file_hash)

for xevent in extract(
location=target,
kinds=kinds,
recurse=recurse,
ignore_pattern=ignore_pattern,
known_archive_hashes=kah
):
if TRACE:
logger.debug('extract:walk:recurse:extraction event: %(xevent)r' % locals())
Expand Down
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