Verfiy signature on linux using .net

[Marwen10]

Hello, I'm trying to validate a quote on a linux machine, and as per the documentation there is a bug for hash verification on mono that throws algorithm is not supported. By looking deeper I guess the issue comes from this function in the mono implementation of RSACryptoServiceProvider:

private string GetHashNameFromOID (string oid) 
		{
			switch (oid) {
			case "1.3.14.3.2.26":
				return "SHA1";
			case "1.2.840.113549.2.5":
				return "MD5";
			case "2.16.840.1.101.3.4.2.1":
				return "SHA256";
			case "2.16.840.1.101.3.4.2.2":
				return "SHA384";
			case "2.16.840.1.101.3.4.2.3":
				return "SHA512";
			default:
				throw new CryptographicException (oid + " is an unsupported hash algorithm for RSA signing");
			}
}

So I guess there is a mismatch from the values representing the hash algorithm passed by the Tpm2lib to this one, which causes the error. So my question is, which part of the implementation I have to change, so that the value is recognized by the mono implementation of System.Security.Cryptography

Thank you

[Marwen10]

in fact changing this method in CryptoLib.cs would make things work:

#if !TSS_USE_BCRYPT
        /// <summary>
        /// Get the CAPI name for a hash algorithm.
        /// </summary>
        /// <param name="algId"></param>
        /// <returns></returns>
        internal static string GetHashName(TpmAlgId algId)
        {
            switch (algId)
            {
                case TpmAlgId.Sha1:
                    return "1.3.14.3.2.26";
                case TpmAlgId.Sha256:
                    return "2.16.840.1.101.3.4.2.1";
                case TpmAlgId.Sha384:
                    return "2.16.840.1.101.3.4.2.2";
                case TpmAlgId.Sha512:
                    return "2.16.840.1.101.3.4.2.3";
                default:
                    Globs.Throw<ArgumentException>("Unsupported hash algorithm");
                    return "1.3.14.3.2.26";
            }
        }
#endif // !TSS_USE_BCRYPT

[amarochk]

Hi Marwen,

Since there is a full-fledged .Net framework for Linux (https://dotnet.microsoft.com/download), we do not really support Mono implementations now. But as your fix is compatible with the .Net Core framework, I've committed it.