Question

我的问题是，我有一些带有不同索引表的编码（类似于base64）：

0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/

而不是

ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

因此，当我使用base64.b64decode()时，它会给我一个错误的结果。有没有办法在转换时设置此表（可能作为参数）？

或者我应该“转换”错误的base64字符串，我的意思是将0替换为A，将1替换为B等等...而不是使用base64decode？如果是这样，最好和最快速的解决方法是什么？

update1 ：我使用它，这有用，但看起来有点慢，而且不专业。：）

def correctbase64(str):
  dicta = [ ['0','A'], ['1','B'], ['2','C'], ['3','D'], ['4','E'], ['5','F'], ['6','G'], ['7','H'], ['8','I'], ['9','J'], ['A','K'], ['B','L'], ['C','M'], ['D','N'], ['E','O'], ['F','P'], ['G','Q'], ['H','R'], ['I','S'], ['J','T'], ['K','U'], ['L','V'], ['M','W'], ['N','X'], ['O','Y'], ['P','Z'], ['Q','a'], ['R','b'], ['S','c'], ['T','d'], ['U','e'], ['V','f'], ['W','g'], ['X','h'], ['Y','i'], ['Z','j'], ['a','k'], ['b','l'], ['c','m'], ['d','n'], ['e','o'], ['f','p'], ['g','q'], ['h','r'], ['i','s'], ['j','t'], ['k','u'], ['l','v'], ['m','w'], ['n','x'], ['o','y'], ['p','z'], ['q','0'], ['r','1'], ['s','2'], ['t','3'], ['u','4'], ['v','5'], ['w','6'], ['x','7'], ['y','8'], ['z','9'] ]
  l = list(str)
  for i in range(len(l)):
    for c in dicta:
      if l[i] == c[0]:
        l[i] = c[1]
        break
  return "".join(l)

Answer 1

这样的事情应该有用（警告：未经测试的代码;可能充满错误）：

import string

my_base64chars  = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/"
std_base64chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

s = s.translate(string.maketrans(my_base64chars, std_base64chars))
data = base64.b64decode(s)

无法使标准base64函数（或他们调用的binascii中的低级函数）使用自定义表。

Answer 2

您可以使用translate()和maketrans()：

from string import maketrans

base64fixTable = maketrans("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/", "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
def correctbase64(str):
    return str.translate(base64fixTable)

Answer 3

使用maketrans构建转换表，然后从第一个字母转换为第二个。然后base64解码。

import string
import base64
def decode(str):
    #make a translation table.
    table = string.maketrans(
      #your alphabet
      string.digits + string.uppercase + string.lowercase + "+/",
      #the original alphabet
      string.uppercase + string.lowercase + string.digits + "+/"
    )
    #translate
    str.translate(s, table)

    #finally decode
    return base64.b64decode(str)

Answer 4

这将处理错误TypeError: Incorrect padding

from string import maketrans
import base64
STANDARD_ALPHABET = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
CUSTOM_ALPHABET = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/'

def correctbase64(input):
    DECODE_TRANS = maketrans(CUSTOM_ALPHABET, STANDARD_ALPHABET)
    newStr =  input.translate(DECODE_TRANS)
    # Add '=' char at the end of the string
    newStr += '='
    return base64.b64decode(newStr)

print custom_base64decode('x/Tcw/g') # hello

Answer 5

print "Hello Reverse Engineering!\n"

import string
import base64


my_base64chars  = "WXYZlabcd3fghijko12e456789ABCDEFGHIJKL+/MNOPQRSTUVmn0pqrstuvwxyz"
std_base64chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

s = 'whatever encoded message you have that used my_base64chars index'

c = s.translate(string.maketrans(my_base64chars, std_base64chars))
data = base64.b64decode(c)
print (data)

使用不同的索引表解码base64就像字符串一样

5 个答案: