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MimeKit

ArcValidationResult Class

An ARC validation result.
Inheritance Hierarchy
SystemObject
  MimeKit.CryptographyArcValidationResult

Namespace: MimeKit.Cryptography
Assembly: MimeKit (in MimeKit.dll) Version: 4.3.0
Syntax
C#
public class ArcValidationResult

The ArcValidationResult type exposes the following members.

Constructors
 NameDescription
Public methodArcValidationResult Initialize a new instance of the ArcValidationResult class.
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Properties
 NameDescription
Public propertyCode exampleChain Get the signature validation results of the entire chain.
Public propertyChainErrors Get the chain validation errors.
Public propertyMessageSignature Get the validation results for the ARC-Message-Signature header.
Public propertySeals Get the validation results for each of the ARC-Seal headers.
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Methods
 NameDescription
Public methodEquals
(Inherited from Object)
Protected methodFinalize
(Inherited from Object)
Public methodGetHashCode
(Inherited from Object)
Public methodGetType
(Inherited from Object)
Protected methodMemberwiseClone
(Inherited from Object)
Public methodToString
(Inherited from Object)
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Remarks

Represents the results of ArcVerifier.Verify or ArcVerifier.VerifyAsync.

If no ARC headers are found on the MimeMessage, then the Chain result will be None and both MessageSignature and Seals will be null.

If ARC headers are found on the MimeMessage but could not be parsed, then the Chain result will be Fail and both MessageSignature and Seals will be null.

Example
C#
using System;
using System.IO;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Collections.Generic;

using Heijden.DNS;

using Org.BouncyCastle.Crypto;

using MimeKit;
using MimeKit.Cryptography;

namespace ArcVerifierExample
{
    // Note: By using the DkimPublicKeyLocatorBase, we avoid having to parse the DNS TXT records
    // in order to get the public key ourselves.
    class ExamplePublicKeyLocator : DkimPublicKeyLocatorBase
    {
        readonly Dictionary<string, AsymmetricKeyParameter> cache;
        readonly Resolver resolver;

        public ExamplePublicKeyLocator ()
        {
            cache = new Dictionary<string, AsymmetricKeyParameter> ();

            resolver = new Resolver ("8.8.8.8") {
                TransportType = TransportType.Udp,
                UseCache = true,
                Retries = 3
            };
        }

        AsymmetricKeyParameter DnsLookup (string domain, string selector, CancellationToken cancellationToken)
        {
            var query = selector + "._domainkey." + domain;
            AsymmetricKeyParameter pubkey;

            // checked if we've already fetched this key
            if (cache.TryGetValue (query, out pubkey))
                return pubkey;

            // make a DNS query
            var response = resolver.Query (query, QType.TXT);
            var builder = new StringBuilder ();

            // combine the TXT records into 1 string buffer
            foreach (var record in response.RecordsTXT) {
                foreach (var text in record.TXT)
                    builder.Append (text);
            }

            var txt = builder.ToString ();

            // DkimPublicKeyLocatorBase provides us with this helpful method.
            pubkey = GetPublicKey (txt);

            cache.Add (query, pubkey);

            return pubkey;
        }

        public AsymmetricKeyParameter LocatePublicKey (string methods, string domain, string selector, CancellationToken cancellationToken = default (CancellationToken))
        {
            var methodList = methods.Split (new char[] { ':' }, StringSplitOptions.RemoveEmptyEntries);
            for (int i = 0; i < methodList.Length; i++) {
                if (methodList[i] == "dns/txt")
                    return DnsLookup (domain, selector, cancellationToken);
            }

            throw new NotSupportedException (string.Format ("{0} does not include any suported lookup methods.", methods));
        }

        public Task<AsymmetricKeyParameter> LocatePublicKeyAsync (string methods, string domain, string selector, CancellationToken cancellationToken = default (CancellationToken))
        {
            return Task.Run (() => {
                return LocatePublicKey (methods, domain, selector, cancellationToken);
            }, cancellationToken);
        }
    }

    class Program
    {
        public static void Main (string[] args)
        {
            if (args.Length == 0) {
                Help ();
                return;
            }

            for (int i = 0; i < args.Length; i++) {
                if (args[i] == "--help") {
                    Help ();
                    return;
                }
            }

            var locator = new ExamplePublicKeyLocator ();
            var verifier = new ArcVerifier (locator);

            for (int i = 0; i < args.Length; i++) {
                if (!File.Exists (args[i])) {
                    Console.Error.WriteLine ("{0}: No such file.", args[i]);
                    continue;
                }

                Console.Write ("{0} -> ", args[i]);

                var message = MimeMessage.Load (args[i]);
                var result = verifier.Verify (message);

                switch (result.Chain) {
                case ArcSignatureValidationResult.None:
                    Console.WriteLine ("No ARC signatures to verify.");
                    break;
                case ArcSignatureValidationResult.Pass:
                    Console.ForegroundColor = ConsoleColor.Green;
                    Console.WriteLine ("PASS");
                    Console.ResetColor ();
                    break;
                case ArcSignatureValidationResult.Fail:
                    Console.ForegroundColor = ConsoleColor.Red;
                    Console.WriteLine ("FAIL");
                    Console.ResetColor ();
                    break;
                }
            }
        }

        static void Help ()
        {
            Console.WriteLine ("Usage is: ArcVerifier [options] [messages]");
            Console.WriteLine ();
            Console.WriteLine ("Options:");
            Console.WriteLine ("  --help               This help menu.");
        }
    }
}
See Also