private static string GenerateRandomURLSafeString(int length)
{
using var rng = new RNGCryptoServiceProvider();
var bit_count = length * 6;
var byte_count = (bit_count + 7) / 8; // rounded up
var bytes = new byte[byte_count];
rng.GetBytes(bytes);
return(Base64Util.UrlEncode(bytes));
}
/// <summary>
/// Return the paseed verifier and its challenge
/// </summary>
/// <param name="verifier">A secure random generated verifier</param>
/// <returns></returns>
public static (string verifier, string challenge) GenerateCodes(string verifier)
{
Ensure.ArgumentNotNull(verifier, nameof(verifier));
if (verifier.Length < VERIFY_MIN_LENGTH || verifier.Length > VERIFY_MAX_LENGTH)
{
throw new ArgumentException(
$"length must be between {VERIFY_MIN_LENGTH} and {VERIFY_MAX_LENGTH}",
nameof(verifier)
);
}
var challenge = Base64Util.UrlEncode(ComputeSHA256(verifier));
return(verifier, challenge);
}