TypeError with crypto.Decipher using aes-256-cbc-hmac-sha1 algorithm

[benbuckman]

(Also posted on StackOverflow - http://stackoverflow.com/questions/23527007 - but this seems like a bug, so belongs here.)

I'm trying to use the aes-256-cbc-hmac-sha1 algorithm with the crypto module.

Here's a code snippet showing what I'm trying to do:

// adapted from http://stackoverflow.com/a/6046913
var crypto = require('crypto');
var data = "I am the clear text data";
console.log('Original cleartext: ' + data);

// //// WORKS
// var algorithm = 'aes-128-cbc';
// var keyBuffer = crypto.randomBytes(16);
// var ivBuffer = crypto.randomBytes(16);

// DOES NOT WORK
var algorithm = 'aes-256-cbc-hmac-sha1';
var keyBuffer = crypto.randomBytes(32);
var ivBuffer = crypto.randomBytes(16);

// var algorithm = 'aes-256-cfb8';       // ok
// var keyBuffer = crypto.randomBytes(32);
// var ivBuffer = crypto.randomBytes(16);

// var algorithm = 'aes-128-cbc-hmac-sha1'; // fail
// var keyBuffer = crypto.randomBytes(16);
// var ivBuffer = crypto.randomBytes(16);

var clearEncoding = 'utf8';
var cipherEncoding = 'hex';

var cipher = crypto.createCipheriv(algorithm, keyBuffer, ivBuffer);
var cipherChunks = [];
cipherChunks.push(cipher.update(data, clearEncoding, cipherEncoding));
cipherChunks.push(cipher.final(cipherEncoding));

console.log('ciphertext', cipherChunks.join(''));

var decipher = crypto.createDecipheriv(algorithm, keyBuffer, ivBuffer);
var plainChunks = [];

//// all at once
// var encrypted = cipherChunks.join('');
// plainChunks.push(decipher.update(encrypted, cipherEncoding, clearEncoding));

//// in pieces
for (var i = 0; i < cipherChunks.length;i++) {
  plainChunks.push(decipher.update(cipherChunks[i], cipherEncoding, clearEncoding));
}
plainChunks.push(decipher.final(clearEncoding));

// var pt = plainChunks.join('');

var pt = '';
for (i = 0; i < plainChunks.length; i++) pt += plainChunks[i].toString(clearEncoding);

console.log("UTF8 plaintext deciphered: " + pt);
console.log('GOOD with ' + algorithm + '?', pt === data);

The algorithms without an included HMAC work, but the HMAC ones don't. It fails on the decipher.update step. Full output:

Original cleartext: I am the clear text data
ciphertext 364ddcface495bcc4e7c8c895443143a632a98d0942b8c844d53db7d770fabca

crypto.js:279
  var ret = this._binding.update(data, inputEncoding);
                          ^
TypeError: error:00000000:lib(0):func(0):reason(0)
    at Decipheriv.Cipher.update (crypto.js:279:27)
    at Object.<anonymous> (../../code/../app/crypto-example.js:44:29)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:906:3

I can't find any examples of this algorithm, so maybe I'm just doing something wrong. But the way it works with 'aes-256-cfb8', but not with 'aes-256-cbc-hmac-sha1', suggests there's a bug.

Thank you!

[KiNgMaR]

Encryption (sort of) works, but since 'aes-256-cbc-hmac-sha1' is a (composite) AEAD cipher, it's necessary to extract the authentication tag after encryption and provide it again before decryption.

I implemented this for GCM (a non-composite AEAD mode) in pull request #6317. However the OpenSSL API used there does not work for composite ciphers. I investigated it back in the day and arrived at the conclusion that it was not possible to do given the possibilities of the exposed OpenSSL crypto API. I will recheck and make sure I didn't miss anything!

[thiagodelgado111]

@KiNgMaR, could you help me understand how we'd implement this?