X509Certificate2 Handling of RSASSA-PSS certificates

[asant57]

Description

System.Security.Cryptography.X509Certificates.X509Certificate2 can load an RSASSA-PSS certificate from bytes (i.e. the X509Certificate2(byte[] rawData) constructor) but is unable to create the X509Certificate2 object with the static function CreateFromPem(ReadOnlySpan certPem, ReadOnlySpan keyPem).

Reproduction Steps

class RSASSATester
{
public static string RSASSAPSSPrivateKeyPem => @"-----BEGIN PRIVATE KEY-----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-----END PRIVATE KEY-----";

    public static string RSARSSAPSSCertPem => @"-----BEGIN CERTIFICATE-----
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-----END CERTIFICATE-----";

    static string CertBytesHex => "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";

    static void Main(string[] args)
    {
        Console.WriteLine("Hello, World!");

        var t1 = new System.Security.Cryptography.X509Certificates.X509Certificate2(StringtoBytes(CertBytesHex));

        var cert = System.Security.Cryptography.X509Certificates.X509Certificate2.CreateFromPem(RSARSSAPSSCertPem, RSASSAPSSPrivateKeyPem);
    }

    public static byte[] StringtoBytes(string hex)
    {
        if (hex == null)
            return null;

        if (hex.Length == 0)
        {
            return new byte[0];
        }

        return Enumerable.Range(0, hex.Length).Where(x => x % 2 == 0).Select(x => Convert.ToByte(hex.Substring(x, 2), 16)).ToArray();

    }
}

Expected behavior

The expected behavior is for X509Certificate2.CreateFromPem to properly return the X509Certificate2 object for an RSASSA-PSS certificate.

Actual behavior

The X509Certificate2.CreateFromPem() function returns the following CryptographicException: "System.Security.Cryptography.CryptographicException: ''1.2.840.113549.1.1.10' is not a known key algorithm.'"

Regression?

No response

Known Workarounds

No response

Configuration

This has been tested and verified at .NET 5, 7, and 8

Other information

The Certificate present has been created solely for this purpose and is not used for any other purpose thus the key is a "safe" key.

[vcsjones]

A more distilled version of this problem is that RSA.ImportPkcs8PrivateKey cannot handle PKCS#8 RSA keys that have an ObjectIdentifier of 1.2.840.113549.1.1.10 (RSASSA-PSS).

The RSAKeyFormatHelper here:

runtime/src/libraries/Common/src/System/Security/Cryptography/RSAKeyFormatHelper.cs

Lines 13 to 16 in 0fb0188

	private static readonly string[] s_validOids =
	{
	Oids.Rsa,
	};

Does not handle the RSA-PSS OID.

I do not think it is quite as simple of "Add that OID to the array". We would still need to teach the RSA PKCS#8 handler to know what to do with RSASSA-PSS-params if they are present.

[vcsjones]

How exactly to fix this is probably worth some point of consideration. @bartonjs can probably remember things better here, but my memory is that RSA-PSS keys are not really encouraged anymore. PSS-ness is a property of the signature, not the key.

Having PSS parameters on the key is intended to restrict how signatures are produced, but we don't really have a good path for doing that. We could just ignore the parameters, but I could understand that not being an ideal implicit decision.