How implement Php's openssl_encrypt method in c#?

Question

as in the title, I need to implement in my C# code the equivalent of php's openssl_encrypt method, because I need to call a service on a php page, but we work with c#. The php code is this:

    $textToEncrypt = "test";                                        
  
    $algo = "AES256";
    $iv   = openssl_random_pseudo_bytes(openssl_cipher_iv_length($algo));
    $key  = "1234567890987654"; //Not this key, but just same length
    $parametri_enc  = openssl_encrypt($textToEncrypt , $algo, $key, 0, $iv);
    $iv   = bin2hex($iv); 

I tried many thing, actually my code is:

    string textToEncrypt = "test";
    string secretCode = "1234567890987654"

    // Create sha256 hash
    SHA256 mySHA256 = SHA256Managed.Create();
    byte[] key = mySHA256.ComputeHash(Encoding.ASCII.GetBytes(secretCode));

    // Create secret IV
    byte[] iv = new byte[16];
    RandomNumberGenerator generator = RandomNumberGenerator.Create();
    generator.GetBytes(iv);

    string encryptedText = EncryptString(textToEncrypt, key, iv);

    // And I try to port also the bin2hex method
    var sb = new StringBuilder();
    foreach (byte b in iv)
    {
       sb.AppendFormat("{0:x2}", b);
    }
    var tokenBytesHex = sb.ToString();

And the method EncryptString is

public static string EncryptString(string plainText, byte[] key, byte[] iv)
{
   //Instantiate a new Aes object to perform string symmetric encryption
   Aes encryptor = Aes.Create();

   encryptor.Mode = CipherMode.CBC;

   // Set key and IV
   byte[] aesKey = new byte[32];
   Array.Copy(key, 0, aesKey, 0, 32);
   encryptor.Key = aesKey;
   encryptor.IV = iv;

   // Instantiate a new MemoryStream object to contain the encrypted bytes
   MemoryStream memoryStream = new MemoryStream();

   // Instantiate a new encryptor from our Aes object
   ICryptoTransform aesEncryptor = encryptor.CreateEncryptor();

   // Instantiate a new CryptoStream object to process the data and write it to the 
   // memory stream
   CryptoStream cryptoStream = new CryptoStream(memoryStream, aesEncryptor, CryptoStreamMode.Write);

   // Convert the plainText string into a byte array
   byte[] plainBytes = Encoding.ASCII.GetBytes(plainText);

   // Encrypt the input plaintext string
   cryptoStream.Write(plainBytes, 0, plainBytes.Length);

   // Complete the encryption process
   cryptoStream.FlushFinalBlock();

   // Convert the encrypted data from a MemoryStream to a byte array
   byte[] cipherBytes = memoryStream.ToArray();

   // Close both the MemoryStream and the CryptoStream
   memoryStream.Close();
   cryptoStream.Close();

   // Convert the encrypted byte array to a base64 encoded string
   string cipherText = Convert.ToBase64String(cipherBytes, 0, cipherBytes.Length);

   // Return the encrypted data as a string
   return cipherText;
}

I tried many variation about this porting (that I've found on internet), but without result. If I use a correct encrypted string from my code, I can call the service, so it is working. I need only to encrypt correctly that string, but until now, I've failed

Answer 1

Ok i solved my own problem. I'll share it so if anyone has the same problem, this could work. Basically I saw a decryption c# code here so I update my code in this way First, I pass my secretCode in string format instead of byte[]

So i changed my method signature in this way:

public static string EncryptString(string plainText, string secretcode, byte[] iv)

and inside I changed the way I manipulate the secretCode (passphrase in php equivalent method)

// Set key and IV
var aesKey = Encoding.ASCII.GetBytes(secretcode);

//pad key out to 32 bytes (256bits) if its too short
if (aesKey.Length < 32)
{
   var paddedkey = new byte[32];
   Buffer.BlockCopy(aesKey, 0, paddedkey, 0, aesKey.Length);
   aesKey = paddedkey;
}

So it worked! No other change, just this two small change from my previous post

Updated method

public static string EncryptString(string plainText, string secretcode, byte[] iv)
{
   // Instantiate a new Aes object to perform string symmetric encryption
   Aes encryptor = Aes.Create();

   encryptor.Mode = CipherMode.CBC;

   // Set key and IV
   var aesKey = Encoding.ASCII.GetBytes(secretcode);

   //pad key out to 32 bytes (256bits) if its too short
   if (aesKey.Length < 32)
   {
      var paddedkey = new byte[32];
      Buffer.BlockCopy(aesKey, 0, paddedkey, 0, aesKey.Length);
      aesKey = paddedkey;
   }

   encryptor.Key = aesKey;
   encryptor.IV = iv;

   // Instantiate a new MemoryStream object to contain the encrypted bytes
   MemoryStream memoryStream = new MemoryStream();

   // Instantiate a new encryptor from our Aes object
   ICryptoTransform aesEncryptor = encryptor.CreateEncryptor();

   // Instantiate a new CryptoStream object to process the data and write it to the 
   // memory stream
   CryptoStream cryptoStream = new CryptoStream(memoryStream, aesEncryptor, CryptoStreamMode.Write);

   // Convert the plainText string into a byte array
   byte[] plainBytes = Encoding.ASCII.GetBytes(plainText);

   // Encrypt the input plaintext string
   cryptoStream.Write(plainBytes, 0, plainBytes.Length);

   // Complete the encryption process
   cryptoStream.FlushFinalBlock();

   // Convert the encrypted data from a MemoryStream to a byte array
   byte[] cipherBytes = memoryStream.ToArray();

   // Close both the MemoryStream and the CryptoStream
   memoryStream.Close();
   cryptoStream.Close();

   // Convert the encrypted byte array to a base64 encoded string
   string cipherText = Convert.ToBase64String(cipherBytes, 0, cipherBytes.Length);

   // Return the encrypted data as a string
   return cipherText;
}