PrivateKeyUsagePeriod.cs

using System;
using System.Diagnostics.CodeAnalysis;
using System.Formats.Asn1;
using System.Text;
using Waher.Content.Xml;
 
namespace NeuroAccess.Nfc.TravelDocuments.Security.Properties.CertificateExtensions
{
    public class PrivateKeyUsagePeriod : SecurityObject
    {
        private DateTimeOffset? notBefore = null;
        private DateTimeOffset? notAfter = null;
        protected bool configured = false;
 
        public override string Oid => "2.5.29.16";
 
        public override bool IsConfigured => this.configured;
 
        public override bool Configure(Vector SecurityInfo)
        {
            if (SecurityInfo.LastElementNested is not Vector UsagePeriod)
                return false;
 
            int c = UsagePeriod.Length;
 
            if (c > 0)
            {
                if (!TryParseGeneralizedTime(UsagePeriod[0], out DateTimeOffset? NotBefore))
                    return false;
 
                this.notBefore = NotBefore;
 
                if (c > 1)
                {
                    if (!TryParseGeneralizedTime(UsagePeriod[1], out DateTimeOffset? NotAfter))
                        return false;
 
                    this.notAfter = NotAfter;
                }
            }
 
            this.configured = true;
 
            return true;
        }
 
        public static bool TryParseGeneralizedTime(object? Data,
            [NotNullWhen(true)] out DateTimeOffset? Result)
        {
            if (Data is DateTimeOffset Timestamp)
            {
                Result = Timestamp;
                return true;
            }
 
            if (Data is byte[] Bin && Bin.Length > 0 && (Bin[0] & 0x80) != 0 &&
                Bin.Length == Bin[1] + 2)
            {
                Bin = (byte[])Bin.Clone();
                Bin[0] = (byte)UniversalTagNumber.IA5String;
                AsnReader Reader = new(Bin, AsnEncodingRules.DER);
                string s = Reader.ReadCharacterString((UniversalTagNumber)Bin[0]);
 
                if (s.Length > 12)
                {
                    StringBuilder sb = new();
 
                    sb.Append(s[..4]);
                    sb.Append('-');
                    sb.Append(s.AsSpan(4, 2));
                    sb.Append('-');
                    sb.Append(s.AsSpan(6, 2));
                    sb.Append('T');
                    sb.Append(s.AsSpan(8, 2));
                    sb.Append(':');
                    sb.Append(s.AsSpan(10, 2));
                    sb.Append(':');
                    sb.Append(s[12..]);
 
                    if (XML.TryParse(sb.ToString(), out Timestamp))
                    {
                        Result = Timestamp;
                        return true;
                    }
                }
            }
 
            Result = null;
            return false;
        }
 
        public DateTimeOffset? NotBefore => this.notBefore;
 
        public DateTimeOffset? NotAfter => this.notAfter;
    }
}