PemDecoder.cs

using System;
using System.Collections.Generic;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Threading.Tasks;
using Waher.Content;
using Waher.Runtime.Inventory;
 
namespace Waher.Security.PKCS.Decoders
{
    public class PemDecoder : IContentDecoder
    {
        public const string ContentType = "application/pem-certificate-chain";
 
        public PemDecoder()
        {
        }
 
        public string[] ContentTypes => contentTypes;
 
        private static readonly string[] contentTypes = new string[] { ContentType };
 
        public string[] FileExtensions => new string[] { "pem" };
 
        public bool Decodes(string ContentType, out Grade Grade)
        {
            if (ContentType == PemDecoder.ContentType)
            {
                Grade = Grade.Excellent;
                return true;
            }
            else
            {
                Grade = Grade.NotAtAll;
                return false;
            }
        }
 
        public Task<ContentResponse> DecodeAsync(string ContentType, byte[] Data, Encoding Encoding,
            KeyValuePair<string, string>[] Fields, Uri BaseUri, ICodecProgress Progress)
        {
            List<X509Certificate2> Certificates = new List<X509Certificate2>();
            string s = Encoding.ASCII.GetString(Data);
            int i;
 
            while ((i = s.IndexOf("-----BEGIN CERTIFICATE-----")) >= 0)
            {
                s = s.Substring(i + 27).TrimStart();
 
                i = s.IndexOf("-----END CERTIFICATE-----");
                if (i > 0)
                {
                    byte[] Bin = Convert.FromBase64String(s.Substring(0, i).TrimEnd());
                    s = s.Substring(i + 25).TrimStart();
 
                    X509Certificate2 Certificate = new X509Certificate2(Bin);
 
                    Certificates.Add(Certificate);
                }
            }
 
            return Task.FromResult(new ContentResponse(ContentType, Certificates.ToArray(), Data));
        }
 
        public bool TryGetContentType(string FileExtension, out string ContentType)
        {
            if (string.Compare(FileExtension, "pem", true) == 0)
            {
                ContentType = PemDecoder.ContentType;
                return true;
            }
            else
            {
                ContentType = null;
                return false;
            }
        }
 
        public bool TryGetFileExtension(string ContentType, out string FileExtension)
        {
            switch (ContentType.ToLower())
            {
                case PemDecoder.ContentType:
                    FileExtension = "pem";
                    return true;
 
                default:
                    FileExtension = string.Empty;
                    return false;
            }
        }
 
    }
}