Go

Duplicate PHP's openssl_encrypt and openssl_random_pseudo_bytes

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Demonstrates how to duplicate PHP's openssl_encrypt function. (https://www.php.net/manual/en/function.openssl-encrypt.php) Go

    success := false

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // Duplicates thw following PHP script:

    // $text = "This is a test";
    // $passphrase = "my password";
    // $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length("AES-256-CBC"));
    // $crypted = base64_encode($iv.openssl_encrypt($text, "AES-256-CBC", $passphrase, OPENSSL_RAW_DATA, $iv));
    // echo $crypted;

    crypt := chilkat.NewCrypt2()

    text := "This is a test"
    passphrase := "my password"

    // AES is a block cipher.  The IV size for any block cipher is the size of the block, which is defined by the encryption algorithm. 
    // For AES, the block size is always 16 bytes, regardless of key size (i.e. 128-bits, 192-bits, or 256-bits).
    // Therefore, generate 16 random bytes for the IV.
    crypt.SetEncodingMode("base64")
    ivBase64 := crypt.GenRandomBytesENC(16)

    fmt.Println("Generated IV = ", *ivBase64)

    // Because we're doing AES-256-CBC, the key length must be 256-bits (i.e. 32 bytes).
    // Given that our passphrase is a us-ascii string that can be shorter or longer than 32-bytes, we need to 
    // somehow transform the passphrase to a 32-byte secret key.  We need to know what openssl_encrypt does.
    // Here's the answer from the openssl_encrypt documentation:
    // 
    // "If the passphrase is shorter than expected, it is silently padded with NUL characters; 
    // if the passphrase is longer than expected, it is silently truncated."

    // OK.... so let's pad or shorten to get a 32-byte key.
    bdKey := chilkat.NewBinData()
    bdKey.AppendString(passphrase,"utf-8")

    sz := bdKey.NumBytes()
    if sz > 32 {
        bdKey.RemoveChunk(32,sz - 32)
    } else {
        bdKey.Clear()
        bdKey.AppendPadded(passphrase,"utf-8",false,32)
    }

    // Setup for encryption.
    crypt.SetCryptAlgorithm("aes")
    crypt.SetKeyLength(256)
    crypt.SetEncodedIV(*ivBase64,"base64")
    crypt.SetEncodedKey(*bdKey.GetEncoded("base64"),"base64")

    // Encrypt and base64 encode.
    cipherText64 := crypt.EncryptStringENC(text)

    // The PHP code fragment above returns the base64 encoded bytes of the IV and the encrypted text.
    // So let's do that..
    bd := chilkat.NewBinData()
    bd.AppendEncoded(*ivBase64,"base64")
    bd.AppendEncoded(*cipherText64,"base64")
    result := bd.GetEncoded("base64")

    fmt.Println("result = ", *result)

    // Sample output:
    // dN0vS1O0cWi5BbLAAY+NTf7bs3S27xzPf11RkG47sjs=

    // Now let's decrypt from the output...

    // Setup for decryption.
    crypt.SetCryptAlgorithm("aes")
    crypt.SetKeyLength(256)
    crypt.SetEncodedKey(*bdKey.GetEncoded("base64"),"base64")

    bdResult := chilkat.NewBinData()
    bdResult.AppendEncoded(*result,"base64")
    crypt.SetEncodedIV(*bdResult.GetEncodedChunk(0,16,"base64"),"base64")

    // Remove the IV (first 16 bytes) from the result.
    bdResult.RemoveChunk(0,16)
    success = crypt.DecryptBd(bdResult)
    originalText := bdResult.GetString("utf-8")

    fmt.Println("original text = ", *originalText)

    crypt.DisposeCrypt2()
    bdKey.DisposeBinData()
    bd.DisposeBinData()
    bdResult.DisposeBinData()