diff options
Diffstat (limited to 'Lib/zipfile/__init__.py')
| -rw-r--r-- | Lib/zipfile/__init__.py | 48 |
1 files changed, 34 insertions, 14 deletions
diff --git a/Lib/zipfile/__init__.py b/Lib/zipfile/__init__.py index 894b4d37233..18caeb3e04a 100644 --- a/Lib/zipfile/__init__.py +++ b/Lib/zipfile/__init__.py @@ -234,8 +234,19 @@ class _Extra(bytes): def _check_zipfile(fp): try: - if _EndRecData(fp): - return True # file has correct magic number + endrec = _EndRecData(fp) + if endrec: + if endrec[_ECD_ENTRIES_TOTAL] == 0 and endrec[_ECD_SIZE] == 0 and endrec[_ECD_OFFSET] == 0: + return True # Empty zipfiles are still zipfiles + elif endrec[_ECD_DISK_NUMBER] == endrec[_ECD_DISK_START]: + # Central directory is on the same disk + fp.seek(sum(_handle_prepended_data(endrec))) + if endrec[_ECD_SIZE] >= sizeCentralDir: + data = fp.read(sizeCentralDir) # CD is where we expect it to be + if len(data) == sizeCentralDir: + centdir = struct.unpack(structCentralDir, data) # CD is the right size + if centdir[_CD_SIGNATURE] == stringCentralDir: + return True # First central directory entry has correct magic number except OSError: pass return False @@ -258,6 +269,22 @@ def is_zipfile(filename): pass return result +def _handle_prepended_data(endrec, debug=0): + size_cd = endrec[_ECD_SIZE] # bytes in central directory + offset_cd = endrec[_ECD_OFFSET] # offset of central directory + + # "concat" is zero, unless zip was concatenated to another file + concat = endrec[_ECD_LOCATION] - size_cd - offset_cd + if endrec[_ECD_SIGNATURE] == stringEndArchive64: + # If Zip64 extension structures are present, account for them + concat -= (sizeEndCentDir64 + sizeEndCentDir64Locator) + + if debug > 2: + inferred = concat + offset_cd + print("given, inferred, offset", offset_cd, inferred, concat) + + return offset_cd, concat + def _EndRecData64(fpin, offset, endrec): """ Read the ZIP64 end-of-archive records and use that to update endrec @@ -1501,28 +1528,21 @@ class ZipFile: raise BadZipFile("File is not a zip file") if self.debug > 1: print(endrec) - size_cd = endrec[_ECD_SIZE] # bytes in central directory - offset_cd = endrec[_ECD_OFFSET] # offset of central directory self._comment = endrec[_ECD_COMMENT] # archive comment - # "concat" is zero, unless zip was concatenated to another file - concat = endrec[_ECD_LOCATION] - size_cd - offset_cd - if endrec[_ECD_SIGNATURE] == stringEndArchive64: - # If Zip64 extension structures are present, account for them - concat -= (sizeEndCentDir64 + sizeEndCentDir64Locator) + offset_cd, concat = _handle_prepended_data(endrec, self.debug) + + # self.start_dir: Position of start of central directory + self.start_dir = offset_cd + concat # store the offset to the beginning of data for the # .data_offset property self._data_offset = concat - if self.debug > 2: - inferred = concat + offset_cd - print("given, inferred, offset", offset_cd, inferred, concat) - # self.start_dir: Position of start of central directory - self.start_dir = offset_cd + concat if self.start_dir < 0: raise BadZipFile("Bad offset for central directory") fp.seek(self.start_dir, 0) + size_cd = endrec[_ECD_SIZE] data = fp.read(size_cd) fp = io.BytesIO(data) total = 0 |