CODEWITHSUNDEEP
node.jsswiftencryptionaesnode-crypto
anshul king
anshul king

Reputation: 568

AES256 Issue using swift 5

I am using AES256 algorithm CBC mode with pkc7 padding. I have backend in Node.js. But getting first 12 random characters.

Here is my swift code:

    func encrypt(data: Data, key: Data, iv: Data) throws -> Data? {

        // Output buffer (with padding)
        let outputLength = data.count + kCCBlockSizeAES128

        var outputBuffer = Array<UInt8>(repeating: 0,
                                        count: outputLength)
        //var outputBuffer: [UInt8] = []
        var numBytesEncrypted = 0
        let status = CCCrypt(CCOperation(kCCEncrypt),
                             CCAlgorithm(kCCAlgorithmAES),
                             CCOptions(kCCOptionPKCS7Padding),
                             Array(key),
                             kCCKeySizeAES256,
                             Array(iv),
                             Array(data),
                             data.count,
                             &outputBuffer,
                             outputLength,
                             &numBytesEncrypted)

        guard status == kCCSuccess else { return nil }

        let outputBytes = iv + outputBuffer.prefix(numBytesEncrypted)

        return Data(bytes: outputBytes)
    }

How can I do without padding? Or what should be done from backend?

enter image description here

Upvotes: 2

Views: 6574

Answers (2)

K P
K P

Reputation: 874

You can use tags before and after payload you want to share. That tag will be your headers.

like <tag>string</tag>

So if you encrypt you will get first 12 random bytes

so you need to ignore text other than between **<tag>...</tag>**

Upvotes: 1

idz
idz

Reputation: 12988

There's nothing wrong with what you posted, you probably just got some parameter incorrect somewhere between Swift and node.js.

First of all it's a good idea to check that you can decrypt locally, in the same language, whatever you encrypted. Using information from the screenshot you posted (note for the future: also post everything in text, typing in base 64 encoded data from a screenshot far more tedious than copy and paste).

In your case, in Swift, that would look like this:

import UIKit
import CommonCrypto

var key = "zewQjVQMGdoEJK0yHtLcbP3ZlHOKjERG"

// This is the ciphertext with the initialization vector prepended.
let base64String = "w93bonVuqtW22Drj4HtZ3zNtNSt+5OBMapGGHekLCFA="
var data = Data(base64Encoded: base64String)!
// Split out the initialization vector and ciphertext
var iv = data[0..<kCCBlockSizeAES128]
var ciphertext = data[kCCBlockSizeAES128..<data.count]


var outputLength = data.count
var outputBuffer = Array<UInt8>(repeating:0, count: outputLength)
var bytesDecrypted = 0

let status = CCCrypt(CCOperation(kCCDecrypt),
    CCAlgorithm(kCCAlgorithmAES),
    CCOptions(kCCOptionPKCS7Padding),
    Array(key.utf8),
    kCCKeySizeAES256,
    Array(iv),
    Array(ciphertext),
    ciphertext.count,
    &outputBuffer,
    outputLength,
    &bytesDecrypted
    )

print(String(bytes: outputBuffer.prefix(bytesDecrypted), encoding: .utf8))
// Optional("gmail.com")

Once you know that all is working well in the same language try it in the other. Now I don't know much about node.js, but going line-by-line through the Swift would lead to this:

const crypto = require('crypto')

let keyString = 'zewQjVQMGdoEJK0yHtLcbP3ZlHOKjERG'
let key = Buffer.from(keyString, 'utf8')

let base64String = 'w93bonVuqtW22Drj4HtZ3zNtNSt+5OBMapGGHekLCFA='
let ivPlusCiphertextBuffer = Buffer.from(base64String, 'base64')

// Split out the initialization vector and the ciphertext
let blockSize = 16 // Don't know how to get this in Node.js so hard-code it
let iv = ivPlusCiphertextBuffer.subarray(0, blockSize)
let ciphertext = ivPlusCiphertextBuffer.subarray(blockSize, ivPlusCiphertextBuffer.length)

let decryptor = crypto.createDecipheriv('aes-256-cbc', key, iv)
var plaintext = decryptor.update(ciphertext, 'binary', 'utf8')
plaintext += decryptor.final('utf8')

console.log(plaintext)
// gmail.com

So as long as you get the output of your Swift routines to the input of a node.js routine that looks something like my example above, you should be good to go!

Upvotes: 1

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