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browsercache_simple: Code for 0 length stream in cache file, only seen in Mac

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This commit is contained in:
Jim Miller 2025-09-08 21:41:11 -05:00
parent 354a5708ce
commit df586e9bb7
1 changed files with 28 additions and 16 deletions
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44
fanficfare/browsercache/browsercache_simple.py
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@ -38,8 +38,8 @@ class SimpleCacheException(BrowserCacheException):
SIMPLE_EOF = struct.Struct('<QLLLL') # magic_number, flags, crc32, stream_size, padding
SIMPLE_EOF_SIZE = SIMPLE_EOF.size
FLAG_HAS_SHA256 = 2
ENTRY_MAGIC_NUMBER = 0xfcfb6d1ba7725c30
EOF_MAGIC_NUMBER = 0xf4fa6f45970d41d8
ENTRY_MAGIC_NUMBER = 0xfcfb6d1ba7725c30 # 305c 72a7 1b6d fbfc
EOF_MAGIC_NUMBER = 0xf4fa6f45970d41d8 # d841 0d97 456f faf4
THE_REAL_INDEX_MAGIC_NUMBER = 0x656e74657220796f
class SimpleCache(BaseChromiumCache):
@ -163,6 +163,12 @@ def _validate_entry_file(path):
def _read_entry_file(path,entry_file):
"""Validate that a file is a cache entry file, return the URL (key) if valid"""
# read from path into SimpleFileHeader, use key_length field to determine size of key, return key as byte string
key = _read_entry_file_key(entry_file)
if _key_hash(key) != os.path.basename(path).split('_')[0]:
return None # key in file does not match the hash, something is wrong
return key.decode('utf-8')
def _read_entry_file_key(entry_file):
shformat = struct.Struct('<QLLLL')
shformat_size = shformat.size
data = entry_file.read(shformat_size)
@ -170,23 +176,28 @@ def _read_entry_file(path,entry_file):
if magic != ENTRY_MAGIC_NUMBER:
return None # path is not a cache entry file, wrong magic number
key = entry_file.read(key_length)
if _key_hash(key) != os.path.basename(path).split('_')[0]:
return None # key in file does not match the hash, something is wrong
return key.decode('utf-8')
return key
def _skip_to_start_of_stream(entry_file):
"""Assuming reader is at end of a stream back up to beginning of stream, returning size of data in stream"""
entry_file.seek(-SIMPLE_EOF_SIZE, os.SEEK_CUR)
start_eof_header = entry_file.tell()
data = entry_file.read(SIMPLE_EOF_SIZE)
(magic, flags, crc32, stream_size, padding) = SIMPLE_EOF.unpack(data)
# logger.debug((magic, flags, crc32, stream_size, padding))
if magic != EOF_MAGIC_NUMBER:
raise SimpleCacheException("Supposed cache entry file did not end with EOF header with correct magic "
"number: '%s'" % entry_file.name)
seek_back = stream_size + SIMPLE_EOF_SIZE
if flags & FLAG_HAS_SHA256:
seek_back += 32
entry_file.seek(-seek_back, os.SEEK_CUR)
if stream_size == 0:
logger.debug(">>>Stream size == 0")
entry_file.seek(0, os.SEEK_SET)
_read_entry_file_key(entry_file)
stream_size = start_eof_header - entry_file.tell()
else:
seek_back = stream_size + SIMPLE_EOF_SIZE
if flags & FLAG_HAS_SHA256:
seek_back += 32
entry_file.seek(-seek_back, os.SEEK_CUR)
return stream_size
@ -199,8 +210,8 @@ def _get_data_from_entry_file(path):
def _read_data_from_entry(entry_file):
""" Read the contents portion (stream 1 data) from the instance's cache entry. Return a byte string """
entry_file.seek(0, os.SEEK_END)
_skip_to_start_of_stream(entry_file)
stream_size = _skip_to_start_of_stream(entry_file)
_skip_to_start_of_stream(entry_file) # skip to start of LAST stream
stream_size = _skip_to_start_of_stream(entry_file) # to start of FIRST stream
ret = entry_file.read(stream_size)
return ret
@ -233,8 +244,9 @@ def _read_meta_headers(entry_file):
# uint32 info_size, uint32 flags, uint32 extra_flags, uint64 request_time, uint64 response_time, uint64 orig_response_time, uint32 header_size
PRE_META_HEADER = struct.Struct('<LLL')
predata = entry_file.read(PRE_META_HEADER.size)
logger.debug(predata)
logger.debug(PRE_META_HEADER.unpack(predata))
# logger.debug("predata:")
# logger.debug(predata)
# logger.debug(PRE_META_HEADER.unpack(predata))
extra_flags = PRE_META_HEADER.unpack(predata)[2]
RESPONSE_EXTRA_INFO_HAS_ORIGINAL_RESPONSE_TIME = 1 << 2
if ((extra_flags & RESPONSE_EXTRA_INFO_HAS_ORIGINAL_RESPONSE_TIME) != 0):
@ -245,8 +257,8 @@ def _read_meta_headers(entry_file):
META_HEADER = struct.Struct('<QQL')
data = entry_file.read(META_HEADER.size)
logger.debug(data)
logger.debug(META_HEADER.unpack(data))
# logger.debug(data)
# logger.debug(META_HEADER.unpack(data))
(request_time, response_time) = META_HEADER.unpack(data)[:2]
# not using original_response_time at this time.
header_size = META_HEADER.unpack(data)[-1]