JavaScript AES解密代码转Python后报错：如何解决base64编码字符串无效的问题？

javascript aes解密代码转换为python代码报错问题分析

本文将针对一个将javascript aes解密代码转换为python代码后报错的问题进行分析。原始javascript代码使用crypto库进行aes-128-cbc解密，而转换后的python代码则使用pycryptodome库（crypto.cipher模块）。报错信息提示binascii.error: invalid base64-encoded string: number of data characters (1053) cannot be 1 more than a multiple of 4，表明输入的base64编码字符串无效。

javascript代码如下：

const crypto = require('crypto')
function m(e) {
    return crypto.createhash('md5').update(e).digest()
}
let o = 'ydsecret://query/key/b*rgygvywfnbwpmbazg*wt7sioup2t0c9whmzn39j^dadazhanxvgccy6vyfwnhl'
let n = 'ydsecret://query/iv/c@lze2yzhtz2cygaxksvfsb7y4qwhjitppz0nqp87fbej!iv6v^6fvi2wn@bypj4'
function decode(t) {
    if(!t)
        return null;
    const a = buffer.alloc(16, m(o))
        , r = buffer.alloc(16, m(n))
        , i = crypto.createdecipheriv('aes-128-cbc', a, r);
    let s = i.update(t, 'base64', 'utf-8');
    return s += i.final('utf-8'),
    s
}
let t = 'z21kd9zk1ke6ugku2ccwu4n6elnvodt0yggi0y3g-v0b9syqg8l9d6uernozyohqnydl2efznym6trc_xs-zktftk4hb6jp8xwcznh0avc8qitquiiu_4wkkxjlipvmvfkvjaazzax6vetpkr2fdkfot_jgbm2grsvj3r40autidlimeng8hc0zh4ww7utwutt3oo_zpxg0bsq9wepsab75-chkigkf9htipecl2bl84sbd1xdffczpkkqhecyss0jloxoqp2ltavxrrg58hp1q5uigzz_oo2-jmd-t1r4es40drcaq5bjms62m2vjf8d6ojtoh9jtfnwgzd3cxyn-pd7-tghmynejekfxtayxzpjlfqtrcyde3szuylenkqsl8wrra1hm-1ntfib-blcwadrbynnpp5_54aq_-gbsq8bb_9yex5ovzdb4_ry_spvvuunb39iplmhcdcnjod3ngiidbl9suz-9npjbx05zyrdpmfpal424qdoaxevqnvoh8jqfpzvqahmzu4mjg0sicdwfh7gp1zqgrbxd3esjt_ibinl3gict2xvuhh_nubcelktec6xbqedrqkpunmpzxjhjcvslhtcmsw0s9f0445ho9kt2qzydmbc3fs0oahputfu77gzpqn7sgiqh8vlixicutfvvop-1c-vu5qjfubln2-s5por9fgyg6rt6ioe_pgmwwj-cc00zum7fybfarktr4d3rk57r72qpxn4ja86zscammdg-m5z31rqh_v7echj8kna3go3ywkck4vtswowrfhis5rtz6ekrgc3skfkbb5vp8wop_84mybtgnbmj4cczhtq2hcoxrjf4def6ydt2ubxyv4btvgx9yx3ub4gx0ik5kyvfma6b_lnkrwk331wjuxkqtbgyiuwkr8j5qtvbmirvaa7aa19z4xmieaqbcuq5p4i9fcelthbrjd9yocouhk4u27xxywjjxcjotvzg7zwtiv76fhdeqlgawvjj7ww4nfgjhqc6aka_2afxa4c_lavvzgfukl3xscl7pfkxp6ghjcgkesrr80pt1gffw2xi8x4ejjnm_prsuz'

console.log(decode(t))

对应的python代码：

import hashlib
from Crypto.Cipher import AES
import base64

def m(e):
    return hashlib.md5(e.encode()).digest()

def decode(t):
    if not t:
        return None
    o = 'ydsecret://query/key/B*RGygVywfNBwpmBaZg*WT7SIOUP2T0C9WHMZN39j^DAdaZhAnxvGcCY6VYFwnHl'
    n = 'ydsecret://query/iv/C@lZe2YzHtZ2CYgaXKSVfsb7Y4QWHjITPPZ0nQp87fBeJ!Iv6v^6fvi2WN@bYpJ4'
    a = m(o)
    r = m(n)
    i = AES.new(a, AES.MODE_CBC, r)
    s = i.decrypt(base64.b64decode(t)).decode('utf-8')
    return s

t = 'Z21kD9ZK1ke6ugku2ccWu4n6eLnvoDT0YgGi0y3g-v0B9sYqg8L9D6UERNozYOHqnYdl2efZNyM6Trc_xS-zKtfTK4hb6JP8XwCzNh0avc8qItQUiIU_4wKKXJlIpvMvfKvJaaZzaX6VEtpkr2FdkfoT_Jgbm2GRSVj3r40autIdlImENG8hC0ZH4ww7utwuTt3Oo_ZpXg0BSq9wePSAB75-ChkiGKF9HTIPeCl2bl84SBD1XDfFCZpkKQhecYSs0JLoXOqP2ltavxRrg58Hp1q5uIgZZ_Oo2-Jmd-t1r4es40drcAq5bjmS62M2VJF8D6ojtOh9JTfNwgzD3CxYn-Pd7-TgHMyNEJEkFXTAyxzpjlFqtrCYDE3SZUYlENkqsL8Wrra1hM-1nTfiB-BLcWAdRBynNpP5_54aq_-GBsq8bB_9yEX5ovzDB4_Ry_spVVuUnb39iplMHCdCnjOD3ngiIDbl9SUz-9npjBX05ZYRdPmFPAl424qdoaxeVqnVoH8jQFPZVqaHMzu4mJg0SICDWFH7GP1zqGRbXd3ESjT_iBInl3gICt2XVuhh_nubcELkTEC6xbqEDRQkPUNMpzXJHjcvsLHtcmSW0S9F0445ho9kT2qZYdMBC3Fs0OaHpUtFu77gZpQn7sGiqh8VliXIcUtfvvop-1c-Vu5QjfUbLn2-s5POR9fGYG6rt6ioe_PGmwWj-Cc00zUM7FybfarKTr4D3Rk57R72qpXN4Ja86ZsCAMmDG-m5z31RQh_V7echJ8Kna3Go3yWKCK4vtSwOWrFhiS5RTz6EkrGc3SkFKbb5vp8Wop_84myBtgnBmj4CczhTq2HcOxrJf4def6yDt2uBxyv4bTVGx9Yx3uB4Gx0iK5kYvfma6B_LnkRWk331wjuXKQtBGYIuWkR8J5QtvBmIRVaa7AA19Z4xMIEAqbcuQ5p4I9FCElthBrJd9YOcouHK4U27xxYWJJXcJoTvzG7zWtiV76fHDeQLgAWvJJ7ww4NFgjhqc6AKA_2afxa4c_lAvVZgFuKL3XSCL7PfKxp6GhjcGKeSRr80PT1gfFw2xi8X4ejjNm_prsUZ'

print(decode(t))

错误原因在于t变量的值并非标准的base64编码字符串，其长度为1053，不是4的倍数，导致base64.b64decode(t)函数报错。需要检查t变量的值是否正确，确保其为有效的base64编码字符串。