Encrypting and Decrypting with python and nodejs

问题

I'm trying to encrypt some content in Python and decrypt it in a nodejs application.

I'm struggling to get the two AES implementations to work together though. Here is where I am at.

In node:

var crypto = require('crypto');

var password = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa';
var input = 'hello world';

var encrypt = function (input, password, callback) {
    var m = crypto.createHash('md5');
    m.update(password)
    var key = m.digest('hex');

    m = crypto.createHash('md5');
    m.update(password + key)
    var iv = m.digest('hex');

    // add padding
    while (input.length % 16 !== 0) {
        input += ' ';
    }

    var data = new Buffer(input, 'utf8').toString('binary');

    var cipher = crypto.createCipheriv('aes-256-cbc', key, iv.slice(0,16));
    var encrypted = cipher.update(data, 'binary') + cipher.final('binary');
    var encoded = new Buffer(encrypted, 'binary').toString('base64');

    callback(encoded);
};

var decrypt = function (input, password, callback) {
    // Convert urlsafe base64 to normal base64
    var input = input.replace('-', '+').replace('/', '_');
    // Convert from base64 to binary string
    var edata = new Buffer(input, 'base64').toString('binary')

    // Create key from password
    var m = crypto.createHash('md5');
    m.update(password)
    var key = m.digest('hex');

    // Create iv from password and key
    m = crypto.createHash('md5');
    m.update(password + key)
    var iv = m.digest('hex');

    // Decipher encrypted data
    var decipher = crypto.createDecipheriv('aes-256-cbc', key, iv.slice(0,16));
    var decrypted = decipher.update(edata, 'binary') + decipher.final('binary');
    var plaintext = new Buffer(decrypted, 'binary').toString('utf8');

    callback(plaintext);
};

encrypt(input, password, function (encoded) {
    console.log(encoded);
    decrypt(encoded, password, function (output) {
        console.log(output);
    });
});

This produces the output:

BXSGjDAYKeXlaRXVVJGuREKTPiiXeam8W9e96Nknt3E=
hello world 

In python

from Crypto.Cipher import AES
from hashlib import md5
import base64

password = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
input = 'hello world'

def _encrypt(data, nonce, password):
    m = md5()
    m.update(password)
    key = m.hexdigest()

    m = md5()
    m.update(password + key)
    iv = m.hexdigest()

    # pad to 16 bytes
    data = data + " " * (16 - len(data) % 16)

    aes = AES.new(key, AES.MODE_CBC, iv[:16])

    encrypted = aes.encrypt(data)
    return base64.urlsafe_b64encode(encrypted)

def _decrypt(edata, nonce, password):
    edata = base64.urlsafe_b64decode(edata)

    m = md5()
    m.update(password)
    key = m.hexdigest()

    m = md5()
    m.update(password + key)
    iv = m.hexdigest()

    aes = AES.new(key, AES.MODE_CBC, iv[:16])
    return aes.decrypt(edata)

output = _encrypt(input, "", password) 
print(output)
plaintext = _decrypt(output, "", password)
print(plaintext)

This produces the output

BXSGjDAYKeXlaRXVVJGuRA==
hello world 

Clearly they are very close, but node seems to be padding the output with something. Any ideas how I can get the two to interoperate?

回答1:

OK, I've figured it out, node uses OpenSSL which uses PKCS5 to do padding. PyCrypto doesn't handle the padding so I was doing it myself just add ' ' in both.

If I add PKCS5 padding in the python code and remove the padding in the node code, it works.

So updated working code. Node:

var crypto = require('crypto');

var password = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa';
var input = 'hello world';

var encrypt = function (input, password, callback) {
    var m = crypto.createHash('md5');
    m.update(password)
    var key = m.digest('hex');

    m = crypto.createHash('md5');
    m.update(password + key)
    var iv = m.digest('hex');

    var data = new Buffer(input, 'utf8').toString('binary');

    var cipher = crypto.createCipheriv('aes-256-cbc', key, iv.slice(0,16));

    // UPDATE: crypto changed in v0.10
    // https://github.com/joyent/node/wiki/Api-changes-between-v0.8-and-v0.10 
    var nodev = process.version.match(/^v(\d+)\.(\d+)/);
    var encrypted;

    if( nodev[1] === '0' && parseInt(nodev[2]) < 10) {
        encrypted = cipher.update(data, 'binary') + cipher.final('binary');
    } else {
        encrypted = cipher.update(data, 'utf8', 'binary') + cipher.final('binary');
    }

    var encoded = new Buffer(encrypted, 'binary').toString('base64');

    callback(encoded);
};

var decrypt = function (input, password, callback) {
    // Convert urlsafe base64 to normal base64
    var input = input.replace(/\-/g, '+').replace(/_/g, '/');
    // Convert from base64 to binary string
    var edata = new Buffer(input, 'base64').toString('binary')

    // Create key from password
    var m = crypto.createHash('md5');
    m.update(password)
    var key = m.digest('hex');

    // Create iv from password and key
    m = crypto.createHash('md5');
    m.update(password + key)
    var iv = m.digest('hex');

    // Decipher encrypted data
    var decipher = crypto.createDecipheriv('aes-256-cbc', key, iv.slice(0,16));

    // UPDATE: crypto changed in v0.10
    // https://github.com/joyent/node/wiki/Api-changes-between-v0.8-and-v0.10 
    var nodev = process.version.match(/^v(\d+)\.(\d+)/);
    var decrypted, plaintext;

    if( nodev[1] === '0' && parseInt(nodev[2]) < 10) {  
        decrypted = decipher.update(edata, 'binary') + decipher.final('binary');    
        plaintext = new Buffer(decrypted, 'binary').toString('utf8');
    } else {
        plaintext = (decipher.update(edata, 'binary', 'utf8') + decipher.final('utf8'));
    }

    callback(plaintext);
};

encrypt(input, password, function (encoded) {
    console.log(encoded);
    decrypt(encoded, password, function (output) {
        console.log(output);
    });
});

Python:

from Crypto.Cipher import AES
from hashlib import md5
import base64


password = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
input = 'hello world'

BLOCK_SIZE = 16

def pad (data):
    pad = BLOCK_SIZE - len(data) % BLOCK_SIZE
    return data + pad * chr(pad)

def unpad (padded):
    pad = ord(padded[-1])
    return padded[:-pad]

def _encrypt(data, nonce, password):
    m = md5()
    m.update(password)
    key = m.hexdigest()

    m = md5()
    m.update(password + key)
    iv = m.hexdigest()

    data = pad(data)

    aes = AES.new(key, AES.MODE_CBC, iv[:16])

    encrypted = aes.encrypt(data)
    return base64.urlsafe_b64encode(encrypted)

def _decrypt(edata, nonce, password):
    edata = base64.urlsafe_b64decode(edata)

    m = md5()
    m.update(password)
    key = m.hexdigest()

    m = md5()
    m.update(password + key)
    iv = m.hexdigest()

    aes = AES.new(key, AES.MODE_CBC, iv[:16])
    return unpad(aes.decrypt(edata))

output = _encrypt(input, "", password) 
print(output)
plaintext = _decrypt(output, "", password)
print("'" + plaintext + "'")

回答2:

Just for any one that is similar to me, who was finding a simple way to do the encryption and decryption for AES in python that is doing the same thing in node.js. The class here supports different bits of AES and both hex and base64 encoding that produces same result in node.js.

Also noted that if you are missing the package Crypto, you can simply install it by

pip install pycrypto

The code for python is as follows:

import base64
import hashlib
from Crypto.Cipher import AES

class AESCrypto(object):
    def __init__(self, algorithm, password):
        self.algorithm = filter(lambda x: not x.isdigit(), algorithm).lower()
        self.bits = int(filter(str.isdigit, algorithm))
        self.bs = 16
        if not self.algorithm == 'aes':
            raise Exception('Only AES crypto is supported')
        if not self.bits % 8 == 0:
            raise Exception('Bits of crypto must be a multiply of 8.')
        self.bytes = self.bits / 8
        self.password = password
        self.generateKeyAndIv()

    def generateKeyAndIv(self):
        last = ''
        allBytes = ''
        maxBytes = self.bytes + self.bs
        while len(allBytes) < maxBytes:
            last = hashlib.md5(last + self.password).digest()
            allBytes += last
        self.key = allBytes[:self.bytes]
        self.iv = allBytes[self.bytes:maxBytes]

    def encrypt(self, raw, outputEncoding):
        outputEncoding = outputEncoding.lower()
        raw = self._pad(raw)
        cipher = AES.new(self.key, AES.MODE_CBC, self.iv)
        encrypted = cipher.encrypt(raw)
        if outputEncoding == 'hex':
            return encrypted.encode('hex')
        elif outputEncoding == 'base64':
            return base64.b64encode(encrypted)
        else:
            raise Exception('Encoding is not supported.')

    def decrypt(self, data, inputEncoding):
        inputEncoding = inputEncoding.lower()
        if inputEncoding == 'hex':
            data = ''.join(map(chr, bytearray.fromhex(data)))
        elif inputEncoding == 'base64':
            data = base64.b64decode(data)
        cipher = AES.new(self.key, AES.MODE_CBC, self.iv)
        return self._unpad(cipher.decrypt(data))

    def _pad(self, data):
        padding = self.bs - len(data) % self.bs
        return data + padding * chr(padding)

    @staticmethod
    def _unpad(data):
        return data[0:-ord(data[-1])]

The following are examples to use the class:

Encryption Example:

password = 'some_random_password'
content = 'content_to_be_encrypted'
cipher = AESCrypto('aes192', password)
encrypted = cipher.encrypt(content, 'hex')

Decryption Example:

password = 'some_random_password'
content = 'encrypted_content'
cipher = AESCrypto('aes192', password)
decrypted = cipher.decrypt(content, 'hex')

来源：https://stackoverflow.com/questions/10548973/encrypting-and-decrypting-with-python-and-nodejs