如何使用ctypes解码smb proto - from_buffer_copy方法？

Question

当我尝试使用ctypes - from_buffer_copy解码SMB HEADER时，它出现错误。我已经定义了一个字段（32字节），为什么python显示我ValueError：缓冲区大小太小（32而不是至少40字节）？

代码实验室：Mac OS X的64位
代码实验室：Linux的

# python2.7 smbproto.py 
Traceback (most recent call last): 
    File "smbproto.py", line 77, in <module> 
    SMB_HEADER(data) 
    File "smbproto.py", line 39, in __new__ 
    return self.from_buffer_copy(buffer) 
ValueError: Buffer size too small (32 instead of at least 40 bytes) 

代码在这里。

#!/usr/bin/python 
# -*- coding: utf-8 -*- 

from ctypes import * 
import logging 


logging.basicConfig(level=logging.INFO) 
log = logging.getLogger(__file__) 


class SMB_HEADER(Structure): 

    _fields_ = [ 
    ("server_component", c_uint32), 
    ("smb_command", c_uint8), 
    ("error_class", c_uint8), 
    ("reserved1", c_uint8), 
    ("error_code", c_uint16), 
    ("flags", c_uint8), 
    ("flags2", c_uint16), 
    ("process_id_high", c_uint16), 
    ("signature", c_uint64), 
    ("reserved2", c_uint16), 
    ("tree_id", c_uint16), 
    ("process_id", c_uint16), 
    ("user_id", c_uint16), 
    ("multiplex_id", c_uint16) 
    ] 

    def __new__(self, buffer=None): 
    return self.from_buffer_copy(buffer) 

    def __init__(self, buffer): 
    print("%04x" % self.server_component) 
    print("%01x" % self.smb_command) 
    print("%01x" % self.error_class) 
    print("%01x" % self.reserved1) 
    print("%02x" % self.error_code) 
    print("%01x" % self.flags) 
    print("%02x" % self.flags2) 
    print("%02x" % self.process_id_high) 
    print("%08x" % self.signature) 
    print("%02x" % self.reserved2) 
    print("%02x" % self.tree_id) 
    print("%02x" % self.process_id) 
    print("%02x" % self.user_id) 
    print("%02x" % self.multiplex_id) 


if __name__ == '__main__': 
    data = (
     '\xffSMB' # server_component 
     's'   # smb_command 
     '\x00'  # error_class 
     '\x00'  # reserved1 
     '\x00\x00' # error code 
     '\x98'  # flags 
     '\x01 '  # flags2 
     '\x00\x00' # process_id_high 
     '\x00\x00\x00\x00\x00\x00\x00\x00' # signature 
     '\x00\x00' # reserved2 
     '\x00\x00' # tree_id 
     '/K'  # process_id 
     '\x00\x10' # user_id 
     '\xc5^'  # multiplex_id 
    ) 
    SMB_HEADER(data) 

Answer 1

你有太多你的头结构：

SMB_Header 
    { 
    UCHAR Protocol[4]; 
    UCHAR Command; 
    SMB_ERROR Status; 
    UCHAR Flags; 
    USHORT Flags2; 
    USHORT PIDHigh; 
    UCHAR SecurityFeatures[8]; 
    USHORT Reserved; 
    USHORT TID; 
    USHORT PIDLow; 
    USHORT UID; 
    USHORT MID; 
    }