解决IOU struct.error

问题现象：生成IOU License的时候出现struct.error

[root@192_168_160_202 IOU]# ./crack.py
    *********************************************************************
    Cisco IOU License Generator - Kal 2011, python port of 2006 C version
    hostid=a8c0caa0, hostname=192_168_160_202, ioukey=a8c0ce23L
    Traceback (most recent call last):
      File "./crack.py", line 18, in <module>
        md5input=iouPad1 + iouPad2 + struct.pack('!i', ioukey) + iouPad1
    struct.error: integer out of range for 'i' format code

分析：可能是由于不同机器算出来的值不一样，转换整数的时候溢出。超出'i'的范围那就换类型，用I，l或L可能就行了（具体见后面说明）。

原先第18行是这样的：

md5input=iouPad1 + iouPad2 + struct.pack('!i', ioukey) + iouPad1

现在将i改成L

md5input=iouPad1 + iouPad2 + struct.pack('!L', ioukey) + iouPad1

测试成功：

[root@192_168_160_202 IOU]# ./crack.py
    *********************************************************************
    Cisco IOU License Generator - Kal 2011, python port of 2006 C version
    hostid=a8c0caa0, hostname=192_168_160_202, ioukey=a8c0ce23L
    Add the following text to ~/.iourc:
    [license]
    192_168_160_202 = 0c3838fa36b12ed4;
    You can disable the phone home feature with something like:
     echo '127.0.0.127 xml.cisco.com' >> /etc/hosts

说明：
函数的用法是这样的：struct.pack(format, data)
    The optional first format char indicates byte order, size and alignment:
     @: native order, size & alignment (default)
     =: native order, std. size & alignment
     <: little-endian, std. size & alignment
     >: big-endian, std. size & alignment
     !: same as >
   
    The remaining chars indicate types of args and must match exactly;
    these can be preceded by a decimal repeat count:
     x: pad byte (no data); c:char; b:signed byte; B:unsigned byte;
     h:short; H:unsigned short; i:int; I:unsigned int;
     l:long; L:unsigned long; f:float; d:double.
    Special cases (preceding decimal count indicates length):
     s:string (array of char); p: pascal string (with count byte).
    Special case (only available in native format):
     P:an integer type that is wide enough to hold a pointer.
    Special case (not in native mode unless 'long long' in platform C):
     q:long long; Q:unsigned long long
    Whitespace between formats is ignored.

有时将hostname改短一点也能成功，但不推荐。