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?
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 + "'")