2626
2727using System ;
2828using System . IO ;
29+ using System . Net ;
30+ using System . Linq ;
2931using System . Text ;
3032using System . Threading ;
3133using System . Threading . Tasks ;
3234using System . Collections . Generic ;
3335
34- using Heijden . DNS ;
36+ using DnsClient ;
3537
3638using Org . BouncyCastle . Crypto ;
3739
@@ -42,49 +44,57 @@ namespace DkimVerifierExample
4244{
4345 class DkimPublicKeyLocator : DkimPublicKeyLocatorBase
4446 {
47+ static readonly char [ ] ColonDelimeter = new char [ ] { ':' } ;
4548 readonly Dictionary < string , AsymmetricKeyParameter > cache ;
46- readonly Resolver resolver ;
49+ readonly LookupClient dnsClient ;
4750
4851 public DkimPublicKeyLocator ( )
4952 {
5053 cache = new Dictionary < string , AsymmetricKeyParameter > ( ) ;
5154
52- resolver = new Resolver ( "8.8.8.8" ) {
53- TransportType = TransportType . Udp ,
55+ var options = new LookupClientOptions ( IPAddress . Parse ( "8.8.8.8" ) ) {
5456 UseCache = true ,
5557 Retries = 3
5658 } ;
59+
60+ dnsClient = new LookupClient ( options ) ;
5761 }
5862
59- AsymmetricKeyParameter DnsLookup ( string domain , string selector , CancellationToken cancellationToken )
63+ AsymmetricKeyParameter GetPublicKey ( string query , IDnsQueryResponse response )
6064 {
61- var query = selector + "._domainkey." + domain ;
62-
63- // checked if we've already fetched this key
64- if ( cache . TryGetValue ( query , out var pubkey ) )
65- return pubkey ;
66-
67- // make a DNS query
68- var response = resolver . Query ( query , QType . TXT ) ;
6965 var builder = new StringBuilder ( ) ;
7066
7167 // combine the TXT records into 1 string buffer
72- foreach ( var record in response . RecordsTXT ) {
73- foreach ( var text in record . TXT )
68+ foreach ( var record in response . Answers . TxtRecords ( ) ) {
69+ foreach ( var text in record . Text )
7470 builder . Append ( text ) ;
7571 }
7672
7773 var txt = builder . ToString ( ) ;
7874
79- pubkey = GetPublicKey ( txt ) ;
75+ var pubkey = GetPublicKey ( txt ) ;
8076 cache . Add ( query , pubkey ) ;
8177
8278 return pubkey ;
8379 }
8480
81+ AsymmetricKeyParameter DnsLookup ( string domain , string selector , CancellationToken cancellationToken )
82+ {
83+ var query = selector + "._domainkey." + domain ;
84+
85+ // checked if we've already fetched this key
86+ if ( cache . TryGetValue ( query , out var pubkey ) )
87+ return pubkey ;
88+
89+ // make a DNS query
90+ var response = dnsClient . Query ( query , QueryType . TXT , QueryClass . IN ) ;
91+
92+ return GetPublicKey ( query , response ) ;
93+ }
94+
8595 public override AsymmetricKeyParameter LocatePublicKey ( string methods , string domain , string selector , CancellationToken cancellationToken = default ( CancellationToken ) )
8696 {
87- var methodList = methods . Split ( new char [ ] { ':' } , StringSplitOptions . RemoveEmptyEntries ) ;
97+ var methodList = methods . Split ( ColonDelimeter , StringSplitOptions . RemoveEmptyEntries ) ;
8898 for ( int i = 0 ; i < methodList . Length ; i ++ ) {
8999 if ( methodList [ i ] == "dns/txt" )
90100 return DnsLookup ( domain , selector , cancellationToken ) ;
@@ -93,9 +103,29 @@ AsymmetricKeyParameter DnsLookup (string domain, string selector, CancellationTo
93103 throw new NotSupportedException ( string . Format ( "{0} does not include any suported lookup methods." , methods ) ) ;
94104 }
95105
106+ async Task < AsymmetricKeyParameter > DnsLookupAsync ( string domain , string selector , CancellationToken cancellationToken )
107+ {
108+ var query = selector + "._domainkey." + domain ;
109+
110+ // checked if we've already fetched this key
111+ if ( cache . TryGetValue ( query , out var pubkey ) )
112+ return pubkey ;
113+
114+ // make a DNS query
115+ var response = await dnsClient . QueryAsync ( query , QueryType . TXT , QueryClass . IN , cancellationToken ) . ConfigureAwait ( false ) ;
116+
117+ return GetPublicKey ( query , response ) ;
118+ }
119+
96120 public override Task < AsymmetricKeyParameter > LocatePublicKeyAsync ( string methods , string domain , string selector , CancellationToken cancellationToken = default ( CancellationToken ) )
97121 {
98- throw new NotImplementedException ( "Asynchronous DKIM public key lookup is not implemented in this sample." ) ;
122+ var methodList = methods . Split ( ColonDelimeter , StringSplitOptions . RemoveEmptyEntries ) ;
123+ for ( int i = 0 ; i < methodList . Length ; i ++ ) {
124+ if ( methodList [ i ] == "dns/txt" )
125+ return DnsLookupAsync ( domain , selector , cancellationToken ) ;
126+ }
127+
128+ throw new NotSupportedException ( string . Format ( "{0} does not include any suported lookup methods." , methods ) ) ;
99129 }
100130 }
101131
0 commit comments