How to Decrypt EncryptedAssertion using System.Cryptography

Question

The Identity provider is encrypting the Saml Assertion using the functions of component pro

Dim encryptedSamlAssertion As New EncryptedAssertion(samlAssertion, encryptingCert, New System.Security.Cryptography.Xml.EncryptionMethod(SamlKeyAlgorithm.Aes256Cbc))

At the Service Provider I am trying to Decrypt the assertion. But I cannot use component pro. I have to use System.Security.Cryptography

• X509Certificate is used for encrypting and decryption
• Aes256Cbc is the Encryption Algorithm

Please help in providing me some more information on how can I achieve Decryption of SamlAssertions using X509Certificate and Aes256Cbc Algorithm

Answer 1

private class Saml2SSOSecurityTokenResolver : SecurityTokenResolver
{
    List<SecurityToken> _tokens;

    public Saml2SSOSecurityTokenResolver(List<SecurityToken> tokens)
    {
        _tokens = tokens;
    }
    protected override bool TryResolveSecurityKeyCore(System.IdentityModel.Tokens.SecurityKeyIdentifierClause keyIdentifierClause, out System.IdentityModel.Tokens.SecurityKey key)
    {
        var token = _tokens[0] as X509SecurityToken;

        var myCert = token.Certificate;

        key = null;

        var ekec = keyIdentifierClause as EncryptedKeyIdentifierClause;

        if (ekec != null)
        {
            if (ekec.EncryptionMethod == "http://www.w3.org/2001/04/xmlenc#rsa-1_5")
            {
                var encKey = ekec.GetEncryptedKey();
                var rsa = myCert.PrivateKey as RSACryptoServiceProvider;
                var decKey = rsa.Decrypt(encKey, false);
                key = new InMemorySymmetricSecurityKey(decKey);
                return true;
            }

            var data = ekec.GetEncryptedKey();
            var id = ekec.EncryptingKeyIdentifier;
        }

        return true;
    }

    protected override bool TryResolveTokenCore(System.IdentityModel.Tokens.SecurityKeyIdentifierClause keyIdentifierClause, out System.IdentityModel.Tokens.SecurityToken token)
    {
        throw new NotImplementedException();
    }

    protected override bool TryResolveTokenCore(System.IdentityModel.Tokens.SecurityKeyIdentifier keyIdentifier, out System.IdentityModel.Tokens.SecurityToken token)
    {
        throw new NotImplementedException();
    }
}