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import zlib
from ..rfc7516 import JsonWebEncryption
from ..rfc7516 import JWEZipAlgorithm
GZIP_HEAD = bytes([120, 156])
MAX_SIZE = 250 * 1024
class DeflateZipAlgorithm(JWEZipAlgorithm):
name = "DEF"
description = "DEFLATE"
def compress(self, s: bytes) -> bytes:
"""Compress bytes data with DEFLATE algorithm."""
data = zlib.compress(s)
# https://datatracker.ietf.org/doc/html/rfc1951
# since DEF is always gzip, we can drop gzip headers and tail
return data[2:-4]
def decompress(self, s: bytes) -> bytes:
"""Decompress DEFLATE bytes data."""
if s.startswith(GZIP_HEAD):
decompressor = zlib.decompressobj()
else:
decompressor = zlib.decompressobj(-zlib.MAX_WBITS)
value = decompressor.decompress(s, MAX_SIZE)
if decompressor.unconsumed_tail:
raise ValueError(f"Decompressed string exceeds {MAX_SIZE} bytes")
return value
def register_jwe_rfc7518():
JsonWebEncryption.register_algorithm(DeflateZipAlgorithm())
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