Python IOError : Not a gzipped file (Gzip and Blowfish Encrypt/Compress) 错误

Question

我在使用 python 的内置库 gzip 时遇到了一些问题。浏览了几乎所有其他有关它的堆栈问题，但似乎都没有用。

我的问题是，当我尝试解压缩时，我得到了 IOError

我得到:

Traceback (most recent call last):
File "mymodule.py", line 61, in
  return gz.read()
File "/usr/lib/python2.7/gzip.py", line 245,
  readself._read(readsize)
File "/usr/lib/python2.7/gzip.py", line 287, in
  _readself._read_gzip_header()
File "/usr/lib/python2.7/gzip.py", line 181, in
  _read_gzip_header
raise IOError, 'Not a gzipped file'IOError: Not a gzipped file

这是我通过网络发送它的代码，我为什么这样做可能没有意义，但它通常在 while 循环和内存效率中，我只是简化了它。

buffer = cStringIO.StringIO(output) #output is from a subprocess call
small_buffer = cStringIO.StringIO()
small_string = buffer.read() #need a string to write to buffer 
gzip_obj = gzip.GzipFile(fileobj=small_buffer,compresslevel=6, mode='wb')
gzip_obj.write(small_string)
compressed_str = small_buffer.getvalue()

blowfish = Blowfish.new('abcd', Blowfish.MODE_ECB)
remainder = '|'*(8 - (len(compressed_str) % 8))
compressed_str += remainder
encrypted = blowfish.encrypt(compressed_str)
#i send it over smb, then retrieve it later

然后这是检索它的代码:

#buffer is a cStringIO object filled with data from  retrieval
decrypter = Blowfish.new('abcd', Blowfish.MODE_ECB)
value = buffer.getvalue()
decrypted = decrypter.decrypt(value)
buff = cStringIO.StringIO(decrypted)
buff.seek(0)
gz = gzip.GzipFile(fileobj=buff)
return gz.read()

问题来了

返回 gz.read()

Answer 1

编辑: 我认为...您忘记在解压缩之前移除填充。下面的代码对我有用，如果我不删除填充，也会出现同样的错误。

编辑 2: 填充规范:我认为您进行填充的方式要求您传递填充的大小，因为我假设加密算法可以使用管道性格也。根据RFC 3852, Section 6.3 ，您应该使用所需填充字节数的二进制表示形式(不是 ASCII 数字)进行填充。我更新了下面的代码来解释规范。

import gzip
import cStringIO
from Crypto.Cipher import Blowfish

#gzip and encrypt
small_buffer = cStringIO.StringIO()
small_string = "test data"
with gzip.GzipFile(fileobj=small_buffer,compresslevel=6, mode='wb') as gzip_obj:
    gzip_obj.write(small_string)
compressed_str = small_buffer.getvalue()
blowfish = Blowfish.new('better than bad')
#remainder = '|'*(8 - (len(compressed_str) % 8))
pad_bytes = 8 - (len(compressed_str) % 8)
padding = chr(pad_bytes)*pad_bytes
compressed_str += padding
encrypted = blowfish.encrypt(compressed_str)
print("encrypted: {}".format(encrypted))



#decrypt and ungzip (pretending to be in a separate space here)
value = encrypted
blowfish = Blowfish.new('better than bad')
decrypted = blowfish.decrypt(value)
buff = cStringIO.StringIO(decrypted)
buff.seek(-1,2) #move to the last byte
pad_bytes = ord(buff.read(1)) #get the size of the padding from the last byte
buff.truncate(len(buff.getvalue()) - pad_bytes) #probably a better way to do this.
buff.seek(0)
with gzip.GzipFile(fileobj=buff) as gz:
    back_home = gz.read()
print("back home: {}".format(back_home))