CODEWITHSUNDEEP
c#phpopensslrsarsacryptoserviceprovider
theringostarrs
theringostarrs

Reputation: 12390

Veryifying RSA signature using openssl_public_decrypt failing for .NET signed string

I am attempting to use X509Certificate2 and RSACryptoServiceProvider together with PHP OpenSSL commands to implement two-way mutual security.

It all seems to be fine sending a message from PHP to C#, RSACryptoServiceProvider on the .NET server can decrypt the message using it's own private key and verify the signature using the PHP server's public key.

But going the other way, .NET to PHP, is causing trouble using 'openssl_public_decrypt' to verify the signature of the .NET server. It just returns false. 'openssl_private_decrypt' works fine to decrypt the encrypted data with the PHP server's private key.

I created the RSA (2048)self-signed certificates for both servers using openssl (.key and .crt) and then created a .pfx to use as private key in .NET code.

I am wondering what is the problem here. I am using the default settings for the encryption/decryption on both the .NET and PHP servers. Are the encryption/decryption mechanisms not the same on the case when you have encrypted something with a .pfx? Or does openssl_public_decrypt expect a different encryption from what RSACryptoServiceProvider gives you?

Any help would be great, as I'm not really sure where the issue lies.

Upvotes: 0

Views: 804

Answers (1)

user1469439
user1469439

Reputation:

openssl_public_decrypt is pretty anal about the format of the public key and doesn't support as many padding schemes as openssl_private_decrypt does.

My recommendation: Use phpseclib, a pure PHP RSA implementation. An example:

<?php
include('Crypt/RSA.php');

$rsa = new Crypt_RSA();
$rsa->loadKey('...'); // public key

$plaintext = '...';

$rsa->setEncryptionMode(CRYPT_RSA_ENCRYPTION_PKCS1);
$ciphertext = $rsa->encrypt($plaintext);

$rsa->loadKey('...'); // private key
echo $rsa->decrypt($ciphertext);
?>

It supports a ton more key formats than OpenSSL does, from XML Signature formatted keys, to PuTTY keys, etc.

Upvotes: 2

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