Unable to decrypt a pdf file Using 'aes-256-cbc' algorithm in node js

Question

I am trying to decrypt a PDF file using node js,PDF file encrypted by third party using C# .

I am having a hard time because I keep getting this error:

 D:\IMP\DevOps Implementation\New folder (2)> node index1.js
internal/crypto/cipher.js:172
  const ret = this[kHandle].final();
                            ^
Error: error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt
    at Decipheriv.final (internal/crypto/cipher.js:172:29)
    at Object.AESCrypt.decrypt (D:\IMP\DevOps Implementation\New folder (2)\index1.js:12:18)
    at D:\IMP\DevOps Implementation\New folder (2)\index1.js:57:24
    at FSReqCallback.readFileAfterClose [as oncomplete] (internal/fs/read_file_context.js:63:3) {
  library: 'digital envelope routines',
  function: 'EVP_DecryptFinal_ex',
  reason: 'bad decrypt',
  code: 'ERR_OSSL_EVP_BAD_DECRYPT'
}

we are using below code for encryption(C#)

  private void FileEncrypt(string inputFile, string outputfile, string password)

        {

            byte[] salt = GenerateSalt();

            byte[] passwords = Encoding.UTF8.GetBytes(password);

            RijndaelManaged AES = new RijndaelManaged();

            AES.KeySize = 256;

            AES.BlockSize = 128;

            

            var key = new Rfc2898DeriveBytes(passwords, salt, 50000);

            AES.Key = key.GetBytes(AES.KeySize / 8);

            AES.IV = key.GetBytes(AES.BlockSize / 8);

            AES.Mode = CipherMode.CBC;

            AES.Padding = PaddingMode.Zeros;

            using (FileStream fsCrypt = new FileStream(inputFile + ".aes", FileMode.Create))

            {

                fsCrypt.Write(salt, 0, salt.Length);

                using (CryptoStream cs = new CryptoStream(fsCrypt, AES.CreateEncryptor(), CryptoStreamMode.Write))

                {

                    using (FileStream fsIn = new FileStream(inputFile, FileMode.Open))

                    {

                        byte[] buffer = new byte[1048576];

                        int read;

                        while ((read = fsIn.Read(buffer, 0, buffer.Length)) > 0)

                        {

                            cs.Write(buffer, 0, read);

                        }

                    }

                }

            }

        }

we are using below code for decryption(Node js)

AESCrypt.encrypt = function(cryptkey, iv, cleardata) {
    var encipher = crypto.createCipheriv('aes-256-cbc', cryptkey, iv);
    return Buffer.concat([
        encipher.update(cleardata),
        encipher.final()
    ]);
}

function decrypted(){
var enc;
fs.readFile('./resource/test.pdf', function (err,data) {
    if (err) {
        return console.log(err);
    }
    
    var bufferenc = new Buffer.from(data); 

    var dec = AESCrypt.decrypt(cryptkey,iv, bufferenc);    
        console.log(dec);
   // var buffer = new Buffer.from(dec);                                          
    fs.writeFileSync('./resource/decrypted.pdf',dec); 
    
});
}

Unable to decrypt a pdf file Using 'aes-256-cbc' algorithm in node js

Answer 1

You can try this code to decrypt the pdf data, it's working for me with the C# code:

const fs = require('fs');
const crypto = require("crypto");

function FileDecrypt(inputFile, outputfile, password)
{
    // Read the entire file into the buffer.
    let buffer = fs.readFileSync(inputFile);

    // Read the first eight bytes as a salt.
    let salt = buffer.slice(0,8);
    let cipherText = buffer.slice(8);

    // use key derivation function to get key and iv.
    let derivedBytes = crypto.pbkdf2Sync(password, salt, 50000, 48, "sha1");
    let key = derivedBytes.slice(0, 32);
    let iv = derivedBytes.slice(32);

    let cipher = crypto.createDecipheriv('aes-256-cbc', key, iv);
    // Switch off auto padding in this context
    cipher.setAutoPadding(false);

    let decryptedData = Buffer.concat([cipher.update(cipherText), cipher.final()]);
    fs.writeFileSync(outputfile, decryptedData);    
}

FileDecrypt("encrypted.pdf", "node-decrypted.pdf", "password");