2 // System.Net.ServicePointManager
5 // Lawrence Pit (loz@cable.a2000.nl)
6 // Gonzalo Paniagua Javier (gonzalo@novell.com)
8 // Copyright (c) 2003-2010 Novell, Inc (http://www.novell.com)
12 // Permission is hereby granted, free of charge, to any person obtaining
13 // a copy of this software and associated documentation files (the
14 // "Software"), to deal in the Software without restriction, including
15 // without limitation the rights to use, copy, modify, merge, publish,
16 // distribute, sublicense, and/or sell copies of the Software, and to
17 // permit persons to whom the Software is furnished to do so, subject to
18 // the following conditions:
20 // The above copyright notice and this permission notice shall be
21 // included in all copies or substantial portions of the Software.
23 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
24 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
25 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
26 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
27 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
28 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
29 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
33 using System.Collections;
34 using System.Collections.Specialized;
35 using System.Configuration;
36 using System.Net.Configuration;
37 using System.Security.Cryptography.X509Certificates;
39 using System.Globalization;
40 using System.Net.Security;
42 using System.Text.RegularExpressions;
44 using Mono.Security.Cryptography;
45 using Mono.Security.X509.Extensions;
46 using Mono.Security.Protocol.Tls;
47 using MSX = Mono.Security.X509;
52 // A service point manager manages service points (duh!).
53 // A service point maintains a list of connections (per scheme + authority).
54 // According to HttpWebRequest.ConnectionGroupName each connection group
55 // creates additional connections. therefor, a service point has a hashtable
56 // of connection groups where each value is a list of connections.
58 // when we need to make an HttpWebRequest, we need to do the following:
59 // 1. find service point, given Uri and Proxy
60 // 2. find connection group, given service point and group name
61 // 3. find free connection in connection group, or create one (if ok due to limits)
62 // 4. lease connection
64 // 6. when finished, return connection
71 internal class ServicePointManager {
73 public class ServicePointManager {
76 Uri uri; // schema/host/port
79 public SPKey (Uri uri, bool use_connect) {
81 this.use_connect = use_connect;
88 public bool UseConnect {
89 get { return use_connect; }
92 public override int GetHashCode () {
93 return uri.GetHashCode () + ((use_connect) ? 1 : 0);
96 public override bool Equals (object obj) {
97 SPKey other = obj as SPKey;
102 return (uri.Equals (other.uri) && other.use_connect == use_connect);
106 private static HybridDictionary servicePoints = new HybridDictionary ();
110 private static ICertificatePolicy policy = new DefaultCertificatePolicy ();
111 private static int defaultConnectionLimit = DefaultPersistentConnectionLimit;
112 private static int maxServicePointIdleTime = 900000; // 15 minutes
113 private static int maxServicePoints = 0;
114 private static bool _checkCRL = false;
115 private static SecurityProtocolType _securityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls;
118 static bool expectContinue = false;
120 static bool expectContinue = true;
122 static bool useNagle;
123 static RemoteCertificateValidationCallback server_cert_cb;
124 static bool tcp_keepalive;
125 static int tcp_keepalive_time;
126 static int tcp_keepalive_interval;
130 public const int DefaultNonPersistentConnectionLimit = 4;
131 public const int DefaultPersistentConnectionLimit = 2;
134 const string configKey = "system.net/connectionManagement";
135 static ConnectionManagementData manager;
138 static ServicePointManager ()
141 #if CONFIGURATION_DEP
142 object cfg = ConfigurationManager.GetSection (configKey);
143 ConnectionManagementSection s = cfg as ConnectionManagementSection;
145 manager = new ConnectionManagementData (null);
146 foreach (ConnectionManagementElement e in s.ConnectionManagement)
147 manager.Add (e.Address, e.MaxConnection);
149 defaultConnectionLimit = (int) manager.GetMaxConnections ("*");
153 manager = (ConnectionManagementData) ConfigurationSettings.GetConfig (configKey);
154 if (manager != null) {
155 defaultConnectionLimit = (int) manager.GetMaxConnections ("*");
161 private ServicePointManager ()
167 [Obsolete ("Use ServerCertificateValidationCallback instead", false)]
168 public static ICertificatePolicy CertificatePolicy {
169 get { return policy; }
170 set { policy = value; }
174 // we need it for SslClientStream
177 [MonoTODO("CRL checks not implemented")]
180 static bool CheckCertificateRevocationList {
181 get { return _checkCRL; }
182 set { _checkCRL = false; } // TODO - don't yet accept true
185 public static int DefaultConnectionLimit {
186 get { return defaultConnectionLimit; }
189 throw new ArgumentOutOfRangeException ("value");
191 defaultConnectionLimit = value;
195 static Exception GetMustImplement ()
197 return new NotImplementedException ();
201 public static int DnsRefreshTimeout
204 throw GetMustImplement ();
207 throw GetMustImplement ();
212 public static bool EnableDnsRoundRobin
215 throw GetMustImplement ();
218 throw GetMustImplement ();
222 public static int MaxServicePointIdleTime {
224 return maxServicePointIdleTime;
227 if (value < -2 || value > Int32.MaxValue)
228 throw new ArgumentOutOfRangeException ("value");
229 maxServicePointIdleTime = value;
233 public static int MaxServicePoints {
235 return maxServicePoints;
239 throw new ArgumentException ("value");
241 maxServicePoints = value;
242 RecycleServicePoints ();
247 // we need it for SslClientStream
252 static SecurityProtocolType SecurityProtocol {
253 get { return _securityProtocol; }
254 set { _securityProtocol = value; }
257 public static RemoteCertificateValidationCallback ServerCertificateValidationCallback
260 return server_cert_cb;
263 server_cert_cb = value;
267 public static bool Expect100Continue {
268 get { return expectContinue; }
269 set { expectContinue = value; }
272 public static bool UseNagleAlgorithm {
273 get { return useNagle; }
274 set { useNagle = value; }
278 public static void SetTcpKeepAlive (bool enabled, int keepAliveTime, int keepAliveInterval)
281 if (keepAliveTime <= 0)
282 throw new ArgumentOutOfRangeException ("keepAliveTime", "Must be greater than 0");
283 if (keepAliveInterval <= 0)
284 throw new ArgumentOutOfRangeException ("keepAliveInterval", "Must be greater than 0");
287 tcp_keepalive = enabled;
288 tcp_keepalive_time = keepAliveTime;
289 tcp_keepalive_interval = keepAliveInterval;
292 public static ServicePoint FindServicePoint (Uri address)
294 return FindServicePoint (address, GlobalProxySelection.Select);
297 public static ServicePoint FindServicePoint (string uriString, IWebProxy proxy)
299 return FindServicePoint (new Uri(uriString), proxy);
302 public static ServicePoint FindServicePoint (Uri address, IWebProxy proxy)
305 throw new ArgumentNullException ("address");
307 RecycleServicePoints ();
309 bool usesProxy = false;
310 bool useConnect = false;
311 if (proxy != null && !proxy.IsBypassed(address)) {
313 bool isSecure = address.Scheme == "https";
314 address = proxy.GetProxy (address);
315 if (address.Scheme != "http" && !isSecure)
316 throw new NotSupportedException ("Proxy scheme not supported.");
318 if (isSecure && address.Scheme == "http")
322 address = new Uri (address.Scheme + "://" + address.Authority);
324 ServicePoint sp = null;
325 lock (servicePoints) {
326 SPKey key = new SPKey (address, useConnect);
327 sp = servicePoints [key] as ServicePoint;
331 if (maxServicePoints > 0 && servicePoints.Count >= maxServicePoints)
332 throw new InvalidOperationException ("maximum number of service points reached");
334 string addr = address.ToString ();
336 int limit = defaultConnectionLimit;
338 int limit = (int) manager.GetMaxConnections (addr);
340 sp = new ServicePoint (address, limit, maxServicePointIdleTime);
341 sp.Expect100Continue = expectContinue;
342 sp.UseNagleAlgorithm = useNagle;
343 sp.UsesProxy = usesProxy;
344 sp.UseConnect = useConnect;
345 sp.SetTcpKeepAlive (tcp_keepalive, tcp_keepalive_time, tcp_keepalive_interval);
346 servicePoints.Add (key, sp);
354 internal static void RecycleServicePoints ()
356 ArrayList toRemove = new ArrayList ();
357 lock (servicePoints) {
358 IDictionaryEnumerator e = servicePoints.GetEnumerator ();
359 while (e.MoveNext ()) {
360 ServicePoint sp = (ServicePoint) e.Value;
361 if (sp.AvailableForRecycling) {
362 toRemove.Add (e.Key);
366 for (int i = 0; i < toRemove.Count; i++)
367 servicePoints.Remove (toRemove [i]);
369 if (maxServicePoints == 0 || servicePoints.Count <= maxServicePoints)
372 // get rid of the ones with the longest idle time
373 SortedList list = new SortedList (servicePoints.Count);
374 e = servicePoints.GetEnumerator ();
375 while (e.MoveNext ()) {
376 ServicePoint sp = (ServicePoint) e.Value;
377 if (sp.CurrentConnections == 0) {
378 while (list.ContainsKey (sp.IdleSince))
379 sp.IdleSince = sp.IdleSince.AddMilliseconds (1);
380 list.Add (sp.IdleSince, sp.Address);
384 for (int i = 0; i < list.Count && servicePoints.Count > maxServicePoints; i++)
385 servicePoints.Remove (list.GetByIndex (i));
388 #if MOONLIGHT && SECURITY_DEP
389 internal class ChainValidationHelper {
392 public ChainValidationHelper (object sender)
394 this.sender = sender;
397 // no need to check certificates since we are either
398 // (a) loading from the site of origin (and we accepted its certificate to load from it)
399 // (b) loading from a cross-domain site and we downloaded the policy file using the browser stack
400 // i.e. the certificate was accepted (or the policy would not be valid)
401 internal ValidationResult ValidateChain (Mono.Security.X509.X509CertificateCollection certs)
403 return new ValidationResult (true, false, 0);
407 internal class ChainValidationHelper {
410 static bool is_macosx = System.IO.File.Exists (MSX.OSX509Certificates.SecurityLibrary);
411 static X509RevocationMode revocation_mode;
414 static readonly Converter<Mono.Security.X509.X509CertificateCollection, bool> monodroidCallback;
417 static ChainValidationHelper ()
420 monodroidCallback = (Converter<Mono.Security.X509.X509CertificateCollection, bool>)
421 Delegate.CreateDelegate (typeof(Converter<Mono.Security.X509.X509CertificateCollection, bool>),
422 Type.GetType ("Android.Runtime.AndroidEnvironment, Mono.Android", true)
423 .GetMethod ("TrustEvaluateSsl",
424 System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic));
427 revocation_mode = X509RevocationMode.NoCheck;
429 string str = Environment.GetEnvironmentVariable ("MONO_X509_REVOCATION_MODE");
430 if (String.IsNullOrEmpty (str))
432 revocation_mode = (X509RevocationMode) Enum.Parse (typeof (X509RevocationMode), str, true);
438 public ChainValidationHelper (object sender)
440 this.sender = sender;
445 if (host == null && sender is HttpWebRequest)
446 host = ((HttpWebRequest) sender).Address.Host;
450 set { host = value; }
453 // Used when the obsolete ICertificatePolicy is set to DefaultCertificatePolicy
454 // and the new ServerCertificateValidationCallback is not null
455 internal ValidationResult ValidateChain (Mono.Security.X509.X509CertificateCollection certs)
457 // user_denied is true if the user callback is called and returns false
458 bool user_denied = false;
459 if (certs == null || certs.Count == 0)
462 ICertificatePolicy policy = ServicePointManager.CertificatePolicy;
463 RemoteCertificateValidationCallback cb = ServicePointManager.ServerCertificateValidationCallback;
465 X509Certificate2 leaf = new X509Certificate2 (certs [0].RawData);
466 int status11 = 0; // Error code passed to the obsolete ICertificatePolicy callback
467 SslPolicyErrors errors = 0;
468 X509Chain chain = null;
470 chain = new X509Chain ();
471 chain.ChainPolicy = new X509ChainPolicy ();
472 chain.ChainPolicy.RevocationMode = revocation_mode;
473 for (int i = 1; i < certs.Count; i++) {
474 X509Certificate2 c2 = new X509Certificate2 (certs [i].RawData);
475 chain.ChainPolicy.ExtraStore.Add (c2);
479 if (!chain.Build (leaf))
480 errors |= GetErrorsFromChain (chain);
481 } catch (Exception e) {
482 Console.Error.WriteLine ("ERROR building certificate chain: {0}", e);
483 Console.Error.WriteLine ("Please, report this problem to the Mono team");
484 errors |= SslPolicyErrors.RemoteCertificateChainErrors;
487 if (!CheckCertificateUsage (leaf)) {
488 errors |= SslPolicyErrors.RemoteCertificateChainErrors;
489 status11 = -2146762490; //CERT_E_PURPOSE 0x800B0106
492 if (!CheckServerIdentity (certs [0], Host)) {
493 errors |= SslPolicyErrors.RemoteCertificateNameMismatch;
494 status11 = -2146762481; // CERT_E_CN_NO_MATCH 0x800B010F
498 // No certificate root found means no mozroots or monotouch
502 // Attempt to use OSX certificates
503 // Ideally we should return the SecTrustResult
504 MSX.OSX509Certificates.SecTrustResult trustResult = MSX.OSX509Certificates.SecTrustResult.Deny;
506 trustResult = MSX.OSX509Certificates.TrustEvaluateSsl (certs);
507 // We could use the other values of trustResult to pass this extra information
508 // to the .NET 2 callback for values like SecTrustResult.Confirm
509 result = (trustResult == MSX.OSX509Certificates.SecTrustResult.Proceed ||
510 trustResult == MSX.OSX509Certificates.SecTrustResult.Unspecified);
515 // Clear error status if the OS told us to trust the certificate
520 // callback and DefaultCertificatePolicy needs this since 'result' is not specified
521 status11 = (int) trustResult;
522 errors |= SslPolicyErrors.RemoteCertificateChainErrors;
529 result = monodroidCallback (certs);
536 if (policy != null && (!(policy is DefaultCertificatePolicy) || cb == null)) {
537 ServicePoint sp = null;
538 HttpWebRequest req = sender as HttpWebRequest;
540 sp = req.ServicePointNoLock;
541 if (status11 == 0 && errors != 0)
542 status11 = GetStatusFromChain (chain);
545 result = policy.CheckValidationResult (sp, leaf, req, status11);
546 user_denied = !result && !(policy is DefaultCertificatePolicy);
548 // If there's a 2.0 callback, it takes precedence
550 result = cb (sender, leaf, chain, errors);
551 user_denied = !result;
553 return new ValidationResult (result, user_denied, status11);
556 static int GetStatusFromChain (X509Chain chain)
559 foreach (var status in chain.ChainStatus) {
560 X509ChainStatusFlags flags = status.Status;
561 if (flags == X509ChainStatusFlags.NoError)
565 if ((flags & X509ChainStatusFlags.NotTimeValid) != 0) result = 0x800B0101;
566 // CERT_E_VALIDITYPERIODNESTING
567 else if ((flags & X509ChainStatusFlags.NotTimeNested) != 0) result = 0x800B0102;
569 else if ((flags & X509ChainStatusFlags.Revoked) != 0) result = 0x800B010C;
570 // TRUST_E_CERT_SIGNATURE
571 else if ((flags & X509ChainStatusFlags.NotSignatureValid) != 0) result = 0x80096004;
572 // CERT_E_WRONG_USAGE
573 else if ((flags & X509ChainStatusFlags.NotValidForUsage) != 0) result = 0x800B0110;
574 // CERT_E_UNTRUSTEDROOT
575 else if ((flags & X509ChainStatusFlags.UntrustedRoot) != 0) result = 0x800B0109;
576 // CRYPT_E_NO_REVOCATION_CHECK
577 else if ((flags & X509ChainStatusFlags.RevocationStatusUnknown) != 0) result = 0x80092012;
579 else if ((flags & X509ChainStatusFlags.Cyclic) != 0) result = 0x800B010A;
580 // TRUST_E_FAIL - generic
581 else if ((flags & X509ChainStatusFlags.InvalidExtension) != 0) result = 0x800B010B;
582 // CERT_E_UNTRUSTEDROOT
583 else if ((flags & X509ChainStatusFlags.InvalidPolicyConstraints) != 0) result = 0x800B010D;
584 // TRUST_E_BASIC_CONSTRAINTS
585 else if ((flags & X509ChainStatusFlags.InvalidBasicConstraints) != 0) result = 0x80096019;
586 // CERT_E_INVALID_NAME
587 else if ((flags & X509ChainStatusFlags.InvalidNameConstraints) != 0) result = 0x800B0114;
588 // CERT_E_INVALID_NAME
589 else if ((flags & X509ChainStatusFlags.HasNotSupportedNameConstraint) != 0) result = 0x800B0114;
590 // CERT_E_INVALID_NAME
591 else if ((flags & X509ChainStatusFlags.HasNotDefinedNameConstraint) != 0) result = 0x800B0114;
592 // CERT_E_INVALID_NAME
593 else if ((flags & X509ChainStatusFlags.HasNotPermittedNameConstraint) != 0) result = 0x800B0114;
594 // CERT_E_INVALID_NAME
595 else if ((flags & X509ChainStatusFlags.HasExcludedNameConstraint) != 0) result = 0x800B0114;
597 else if ((flags & X509ChainStatusFlags.PartialChain) != 0) result = 0x800B010A;
599 else if ((flags & X509ChainStatusFlags.CtlNotTimeValid) != 0) result = 0x800B0101;
600 // TRUST_E_CERT_SIGNATURE
601 else if ((flags & X509ChainStatusFlags.CtlNotSignatureValid) != 0) result = 0x80096004;
602 // CERT_E_WRONG_USAGE
603 else if ((flags & X509ChainStatusFlags.CtlNotValidForUsage) != 0) result = 0x800B0110;
604 // CRYPT_E_NO_REVOCATION_CHECK
605 else if ((flags & X509ChainStatusFlags.OfflineRevocation) != 0) result = 0x80092012;
606 // CERT_E_ISSUERCHAINING
607 else if ((flags & X509ChainStatusFlags.NoIssuanceChainPolicy) != 0) result = 0x800B0107;
608 else result = 0x800B010B; // TRUST_E_FAIL - generic
610 break; // Exit the loop on the first error
615 static SslPolicyErrors GetErrorsFromChain (X509Chain chain)
617 SslPolicyErrors errors = SslPolicyErrors.None;
618 foreach (var status in chain.ChainStatus) {
619 if (status.Status == X509ChainStatusFlags.NoError)
621 errors |= SslPolicyErrors.RemoteCertificateChainErrors;
627 static X509KeyUsageFlags s_flags = X509KeyUsageFlags.DigitalSignature |
628 X509KeyUsageFlags.KeyAgreement |
629 X509KeyUsageFlags.KeyEncipherment;
630 // Adapted to System 2.0+ from TlsServerCertificate.cs
631 //------------------------------
632 // Note: this method only works for RSA certificates
633 // DH certificates requires some changes - does anyone use one ?
634 static bool CheckCertificateUsage (X509Certificate2 cert)
637 // certificate extensions are required for this
638 // we "must" accept older certificates without proofs
639 if (cert.Version < 3)
642 X509KeyUsageExtension kux = (cert.Extensions ["2.5.29.15"] as X509KeyUsageExtension);
643 X509EnhancedKeyUsageExtension eku = (cert.Extensions ["2.5.29.37"] as X509EnhancedKeyUsageExtension);
644 if (kux != null && eku != null) {
645 // RFC3280 states that when both KeyUsageExtension and
646 // ExtendedKeyUsageExtension are present then BOTH should
648 if ((kux.KeyUsages & s_flags) == 0)
650 return eku.EnhancedKeyUsages ["1.3.6.1.5.5.7.3.1"] != null ||
651 eku.EnhancedKeyUsages ["2.16.840.1.113730.4.1"] != null;
652 } else if (kux != null) {
653 return ((kux.KeyUsages & s_flags) != 0);
654 } else if (eku != null) {
655 // Server Authentication (1.3.6.1.5.5.7.3.1) or
656 // Netscape Server Gated Crypto (2.16.840.1.113730.4)
657 return eku.EnhancedKeyUsages ["1.3.6.1.5.5.7.3.1"] != null ||
658 eku.EnhancedKeyUsages ["2.16.840.1.113730.4.1"] != null;
661 // last chance - try with older (deprecated) Netscape extensions
662 X509Extension ext = cert.Extensions ["2.16.840.1.113730.1.1"];
664 string text = ext.NetscapeCertType (false);
665 return text.IndexOf ("SSL Server Authentication", StringComparison.Ordinal) != -1;
668 } catch (Exception e) {
669 Console.Error.WriteLine ("ERROR processing certificate: {0}", e);
670 Console.Error.WriteLine ("Please, report this problem to the Mono team");
675 // RFC2818 - HTTP Over TLS, Section 3.1
676 // http://www.ietf.org/rfc/rfc2818.txt
678 // 1. if present MUST use subjectAltName dNSName as identity
679 // 1.1. if multiples entries a match of any one is acceptable
680 // 1.2. wildcard * is acceptable
681 // 2. URI may be an IP address -> subjectAltName.iPAddress
682 // 2.1. exact match is required
683 // 3. Use of the most specific Common Name (CN=) in the Subject
684 // 3.1 Existing practice but DEPRECATED
685 static bool CheckServerIdentity (Mono.Security.X509.X509Certificate cert, string targetHost)
688 Mono.Security.X509.X509Extension ext = cert.Extensions ["2.5.29.17"];
691 SubjectAltNameExtension subjectAltName = new SubjectAltNameExtension (ext);
692 // 1.1 - multiple dNSName
693 foreach (string dns in subjectAltName.DNSNames) {
694 // 1.2 TODO - wildcard support
695 if (Match (targetHost, dns))
699 foreach (string ip in subjectAltName.IPAddresses) {
700 // 2.1. Exact match required
701 if (ip == targetHost)
705 // 3. Common Name (CN=)
706 return CheckDomainName (cert.SubjectName, targetHost);
707 } catch (Exception e) {
708 Console.Error.WriteLine ("ERROR processing certificate: {0}", e);
709 Console.Error.WriteLine ("Please, report this problem to the Mono team");
714 static bool CheckDomainName (string subjectName, string targetHost)
716 string domainName = String.Empty;
717 Regex search = new Regex(@"CN\s*=\s*([^,]*)");
718 MatchCollection elements = search.Matches(subjectName);
719 if (elements.Count == 1) {
720 if (elements[0].Success)
721 domainName = elements[0].Groups[1].Value.ToString();
724 return Match (targetHost, domainName);
727 // ensure the pattern is valid wrt to RFC2595 and RFC2818
728 // http://www.ietf.org/rfc/rfc2595.txt
729 // http://www.ietf.org/rfc/rfc2818.txt
730 static bool Match (string hostname, string pattern)
732 // check if this is a pattern
733 int index = pattern.IndexOf ('*');
735 // not a pattern, do a direct case-insensitive comparison
736 return (String.Compare (hostname, pattern, true, CultureInfo.InvariantCulture) == 0);
739 // check pattern validity
740 // A "*" wildcard character MAY be used as the left-most name component in the certificate.
742 // unless this is the last char (valid)
743 if (index != pattern.Length - 1) {
744 // then the next char must be a dot .'.
745 if (pattern [index + 1] != '.')
749 // only one (A) wildcard is supported
750 int i2 = pattern.IndexOf ('*', index + 1);
754 // match the end of the pattern
755 string end = pattern.Substring (index + 1);
756 int length = hostname.Length - end.Length;
757 // no point to check a pattern that is longer than the hostname
761 if (String.Compare (hostname, length, end, 0, end.Length, true, CultureInfo.InvariantCulture) != 0)
764 // special case, we start with the wildcard
766 // ensure we hostname non-matched part (start) doesn't contain a dot
767 int i3 = hostname.IndexOf ('.');
768 return ((i3 == -1) || (i3 >= (hostname.Length - end.Length)));
771 // match the start of the pattern
772 string start = pattern.Substring (0, index);
773 return (String.Compare (hostname, 0, start, 0, start.Length, true, CultureInfo.InvariantCulture) == 0);