ValidateCodeVerifierAgainstCodeChallenge

ValidateCodeVerifierAgainstCodeChallenge.cs

private bool ValidateCodeVerifierAgainstCodeChallenge(string codeVerifier, string codeChallenge, string codeChallengeMethod)
{
    if (codeChallengeMethod == OidcConstants.CodeChallengeMethods.Plain)
    {
        return TimeConstantComparer.IsEqual(codeVerifier.Sha256(), codeChallenge);
    }

    var codeVerifierBytes = Encoding.ASCII.GetBytes(codeVerifier);
    var hashedBytes = codeVerifierBytes.Sha256();
    var transformedCodeVerifier = Base64Url.Encode(hashedBytes);

    return TimeConstantComparer.IsEqual(transformedCodeVerifier.Sha256(), codeChallenge);
}