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; }
173 [MonoTODO("CRL checks not implemented")]
174 public static bool CheckCertificateRevocationList {
175 get { return _checkCRL; }
176 set { _checkCRL = false; } // TODO - don't yet accept true
179 public static int DefaultConnectionLimit {
180 get { return defaultConnectionLimit; }
183 throw new ArgumentOutOfRangeException ("value");
185 defaultConnectionLimit = value;
189 static Exception GetMustImplement ()
191 return new NotImplementedException ();
195 public static int DnsRefreshTimeout
198 throw GetMustImplement ();
201 throw GetMustImplement ();
206 public static bool EnableDnsRoundRobin
209 throw GetMustImplement ();
212 throw GetMustImplement ();
216 public static int MaxServicePointIdleTime {
218 return maxServicePointIdleTime;
221 if (value < -2 || value > Int32.MaxValue)
222 throw new ArgumentOutOfRangeException ("value");
223 maxServicePointIdleTime = value;
227 public static int MaxServicePoints {
229 return maxServicePoints;
233 throw new ArgumentException ("value");
235 maxServicePoints = value;
236 RecycleServicePoints ();
241 // we need it for SslClientStream
246 static SecurityProtocolType SecurityProtocol {
247 get { return _securityProtocol; }
248 set { _securityProtocol = value; }
251 public static RemoteCertificateValidationCallback ServerCertificateValidationCallback
254 return server_cert_cb;
257 server_cert_cb = value;
261 public static bool Expect100Continue {
262 get { return expectContinue; }
263 set { expectContinue = value; }
266 public static bool UseNagleAlgorithm {
267 get { return useNagle; }
268 set { useNagle = value; }
272 public static void SetTcpKeepAlive (bool enabled, int keepAliveTime, int keepAliveInterval)
275 if (keepAliveTime <= 0)
276 throw new ArgumentOutOfRangeException ("keepAliveTime", "Must be greater than 0");
277 if (keepAliveInterval <= 0)
278 throw new ArgumentOutOfRangeException ("keepAliveInterval", "Must be greater than 0");
281 tcp_keepalive = enabled;
282 tcp_keepalive_time = keepAliveTime;
283 tcp_keepalive_interval = keepAliveInterval;
286 public static ServicePoint FindServicePoint (Uri address)
288 return FindServicePoint (address, GlobalProxySelection.Select);
291 public static ServicePoint FindServicePoint (string uriString, IWebProxy proxy)
293 return FindServicePoint (new Uri(uriString), proxy);
296 public static ServicePoint FindServicePoint (Uri address, IWebProxy proxy)
299 throw new ArgumentNullException ("address");
301 RecycleServicePoints ();
303 bool usesProxy = false;
304 bool useConnect = false;
305 if (proxy != null && !proxy.IsBypassed(address)) {
307 bool isSecure = address.Scheme == "https";
308 address = proxy.GetProxy (address);
309 if (address.Scheme != "http" && !isSecure)
310 throw new NotSupportedException ("Proxy scheme not supported.");
312 if (isSecure && address.Scheme == "http")
316 address = new Uri (address.Scheme + "://" + address.Authority);
318 ServicePoint sp = null;
319 lock (servicePoints) {
320 SPKey key = new SPKey (address, useConnect);
321 sp = servicePoints [key] as ServicePoint;
325 if (maxServicePoints > 0 && servicePoints.Count >= maxServicePoints)
326 throw new InvalidOperationException ("maximum number of service points reached");
328 string addr = address.ToString ();
330 int limit = defaultConnectionLimit;
332 int limit = (int) manager.GetMaxConnections (addr);
334 sp = new ServicePoint (address, limit, maxServicePointIdleTime);
335 sp.Expect100Continue = expectContinue;
336 sp.UseNagleAlgorithm = useNagle;
337 sp.UsesProxy = usesProxy;
338 sp.UseConnect = useConnect;
339 sp.SetTcpKeepAlive (tcp_keepalive, tcp_keepalive_time, tcp_keepalive_interval);
340 servicePoints.Add (key, sp);
348 internal static void RecycleServicePoints ()
350 ArrayList toRemove = new ArrayList ();
351 lock (servicePoints) {
352 IDictionaryEnumerator e = servicePoints.GetEnumerator ();
353 while (e.MoveNext ()) {
354 ServicePoint sp = (ServicePoint) e.Value;
355 if (sp.AvailableForRecycling) {
356 toRemove.Add (e.Key);
360 for (int i = 0; i < toRemove.Count; i++)
361 servicePoints.Remove (toRemove [i]);
363 if (maxServicePoints == 0 || servicePoints.Count <= maxServicePoints)
366 // get rid of the ones with the longest idle time
367 SortedList list = new SortedList (servicePoints.Count);
368 e = servicePoints.GetEnumerator ();
369 while (e.MoveNext ()) {
370 ServicePoint sp = (ServicePoint) e.Value;
371 if (sp.CurrentConnections == 0) {
372 while (list.ContainsKey (sp.IdleSince))
373 sp.IdleSince = sp.IdleSince.AddMilliseconds (1);
374 list.Add (sp.IdleSince, sp.Address);
378 for (int i = 0; i < list.Count && servicePoints.Count > maxServicePoints; i++)
379 servicePoints.Remove (list.GetByIndex (i));
382 #if MOONLIGHT && SECURITY_DEP
383 internal class ChainValidationHelper {
386 public ChainValidationHelper (object sender)
388 this.sender = sender;
391 // no need to check certificates since we are either
392 // (a) loading from the site of origin (and we accepted its certificate to load from it)
393 // (b) loading from a cross-domain site and we downloaded the policy file using the browser stack
394 // i.e. the certificate was accepted (or the policy would not be valid)
395 internal ValidationResult ValidateChain (Mono.Security.X509.X509CertificateCollection certs)
397 return new ValidationResult (true, false, 0);
401 internal class ChainValidationHelper {
404 static bool is_macosx = System.IO.File.Exists (MSX.OSX509Certificates.SecurityLibrary);
405 static X509RevocationMode revocation_mode;
408 static readonly Converter<Mono.Security.X509.X509CertificateCollection, bool> monodroidCallback;
411 static ChainValidationHelper ()
414 monodroidCallback = (Converter<Mono.Security.X509.X509CertificateCollection, bool>)
415 Delegate.CreateDelegate (typeof(Converter<Mono.Security.X509.X509CertificateCollection, bool>),
416 Type.GetType ("Android.Runtime.AndroidEnvironment, Mono.Android", true)
417 .GetMethod ("TrustEvaluateSsl",
418 System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic));
421 revocation_mode = X509RevocationMode.NoCheck;
423 string str = Environment.GetEnvironmentVariable ("MONO_X509_REVOCATION_MODE");
424 if (String.IsNullOrEmpty (str))
426 revocation_mode = (X509RevocationMode) Enum.Parse (typeof (X509RevocationMode), str, true);
432 public ChainValidationHelper (object sender)
434 this.sender = sender;
439 if (host == null && sender is HttpWebRequest)
440 host = ((HttpWebRequest) sender).Address.Host;
444 set { host = value; }
447 // Used when the obsolete ICertificatePolicy is set to DefaultCertificatePolicy
448 // and the new ServerCertificateValidationCallback is not null
449 internal ValidationResult ValidateChain (Mono.Security.X509.X509CertificateCollection certs)
451 // user_denied is true if the user callback is called and returns false
452 bool user_denied = false;
453 if (certs == null || certs.Count == 0)
456 ICertificatePolicy policy = ServicePointManager.CertificatePolicy;
457 RemoteCertificateValidationCallback cb = ServicePointManager.ServerCertificateValidationCallback;
459 X509Certificate2 leaf = new X509Certificate2 (certs [0].RawData);
460 int status11 = 0; // Error code passed to the obsolete ICertificatePolicy callback
461 SslPolicyErrors errors = 0;
462 X509Chain chain = null;
464 chain = new X509Chain ();
465 chain.ChainPolicy = new X509ChainPolicy ();
466 chain.ChainPolicy.RevocationMode = revocation_mode;
467 for (int i = 1; i < certs.Count; i++) {
468 X509Certificate2 c2 = new X509Certificate2 (certs [i].RawData);
469 chain.ChainPolicy.ExtraStore.Add (c2);
473 if (!chain.Build (leaf))
474 errors |= GetErrorsFromChain (chain);
475 } catch (Exception e) {
476 Console.Error.WriteLine ("ERROR building certificate chain: {0}", e);
477 Console.Error.WriteLine ("Please, report this problem to the Mono team");
478 errors |= SslPolicyErrors.RemoteCertificateChainErrors;
481 if (!CheckCertificateUsage (leaf)) {
482 errors |= SslPolicyErrors.RemoteCertificateChainErrors;
483 status11 = -2146762490; //CERT_E_PURPOSE 0x800B0106
486 if (!CheckServerIdentity (certs [0], Host)) {
487 errors |= SslPolicyErrors.RemoteCertificateNameMismatch;
488 status11 = -2146762481; // CERT_E_CN_NO_MATCH 0x800B010F
492 // No certificate root found means no mozroots or monotouch
496 // Attempt to use OSX certificates
497 // Ideally we should return the SecTrustResult
498 MSX.OSX509Certificates.SecTrustResult trustResult = MSX.OSX509Certificates.SecTrustResult.Deny;
500 trustResult = MSX.OSX509Certificates.TrustEvaluateSsl (certs);
501 // We could use the other values of trustResult to pass this extra information
502 // to the .NET 2 callback for values like SecTrustResult.Confirm
503 result = (trustResult == MSX.OSX509Certificates.SecTrustResult.Proceed ||
504 trustResult == MSX.OSX509Certificates.SecTrustResult.Unspecified);
509 // Clear error status if the OS told us to trust the certificate
514 // callback and DefaultCertificatePolicy needs this since 'result' is not specified
515 status11 = (int) trustResult;
516 errors |= SslPolicyErrors.RemoteCertificateChainErrors;
523 result = monodroidCallback (certs);
530 if (policy != null && (!(policy is DefaultCertificatePolicy) || cb == null)) {
531 ServicePoint sp = null;
532 HttpWebRequest req = sender as HttpWebRequest;
534 sp = req.ServicePointNoLock;
535 if (status11 == 0 && errors != 0)
536 status11 = GetStatusFromChain (chain);
539 result = policy.CheckValidationResult (sp, leaf, req, status11);
540 user_denied = !result && !(policy is DefaultCertificatePolicy);
542 // If there's a 2.0 callback, it takes precedence
544 result = cb (sender, leaf, chain, errors);
545 user_denied = !result;
547 return new ValidationResult (result, user_denied, status11);
550 static int GetStatusFromChain (X509Chain chain)
553 foreach (var status in chain.ChainStatus) {
554 X509ChainStatusFlags flags = status.Status;
555 if (flags == X509ChainStatusFlags.NoError)
559 if ((flags & X509ChainStatusFlags.NotTimeValid) != 0) result = 0x800B0101;
560 // CERT_E_VALIDITYPERIODNESTING
561 else if ((flags & X509ChainStatusFlags.NotTimeNested) != 0) result = 0x800B0102;
563 else if ((flags & X509ChainStatusFlags.Revoked) != 0) result = 0x800B010C;
564 // TRUST_E_CERT_SIGNATURE
565 else if ((flags & X509ChainStatusFlags.NotSignatureValid) != 0) result = 0x80096004;
566 // CERT_E_WRONG_USAGE
567 else if ((flags & X509ChainStatusFlags.NotValidForUsage) != 0) result = 0x800B0110;
568 // CERT_E_UNTRUSTEDROOT
569 else if ((flags & X509ChainStatusFlags.UntrustedRoot) != 0) result = 0x800B0109;
570 // CRYPT_E_NO_REVOCATION_CHECK
571 else if ((flags & X509ChainStatusFlags.RevocationStatusUnknown) != 0) result = 0x80092012;
573 else if ((flags & X509ChainStatusFlags.Cyclic) != 0) result = 0x800B010A;
574 // TRUST_E_FAIL - generic
575 else if ((flags & X509ChainStatusFlags.InvalidExtension) != 0) result = 0x800B010B;
576 // CERT_E_UNTRUSTEDROOT
577 else if ((flags & X509ChainStatusFlags.InvalidPolicyConstraints) != 0) result = 0x800B010D;
578 // TRUST_E_BASIC_CONSTRAINTS
579 else if ((flags & X509ChainStatusFlags.InvalidBasicConstraints) != 0) result = 0x80096019;
580 // CERT_E_INVALID_NAME
581 else if ((flags & X509ChainStatusFlags.InvalidNameConstraints) != 0) result = 0x800B0114;
582 // CERT_E_INVALID_NAME
583 else if ((flags & X509ChainStatusFlags.HasNotSupportedNameConstraint) != 0) result = 0x800B0114;
584 // CERT_E_INVALID_NAME
585 else if ((flags & X509ChainStatusFlags.HasNotDefinedNameConstraint) != 0) result = 0x800B0114;
586 // CERT_E_INVALID_NAME
587 else if ((flags & X509ChainStatusFlags.HasNotPermittedNameConstraint) != 0) result = 0x800B0114;
588 // CERT_E_INVALID_NAME
589 else if ((flags & X509ChainStatusFlags.HasExcludedNameConstraint) != 0) result = 0x800B0114;
591 else if ((flags & X509ChainStatusFlags.PartialChain) != 0) result = 0x800B010A;
593 else if ((flags & X509ChainStatusFlags.CtlNotTimeValid) != 0) result = 0x800B0101;
594 // TRUST_E_CERT_SIGNATURE
595 else if ((flags & X509ChainStatusFlags.CtlNotSignatureValid) != 0) result = 0x80096004;
596 // CERT_E_WRONG_USAGE
597 else if ((flags & X509ChainStatusFlags.CtlNotValidForUsage) != 0) result = 0x800B0110;
598 // CRYPT_E_NO_REVOCATION_CHECK
599 else if ((flags & X509ChainStatusFlags.OfflineRevocation) != 0) result = 0x80092012;
600 // CERT_E_ISSUERCHAINING
601 else if ((flags & X509ChainStatusFlags.NoIssuanceChainPolicy) != 0) result = 0x800B0107;
602 else result = 0x800B010B; // TRUST_E_FAIL - generic
604 break; // Exit the loop on the first error
609 static SslPolicyErrors GetErrorsFromChain (X509Chain chain)
611 SslPolicyErrors errors = SslPolicyErrors.None;
612 foreach (var status in chain.ChainStatus) {
613 if (status.Status == X509ChainStatusFlags.NoError)
615 errors |= SslPolicyErrors.RemoteCertificateChainErrors;
621 static X509KeyUsageFlags s_flags = X509KeyUsageFlags.DigitalSignature |
622 X509KeyUsageFlags.KeyAgreement |
623 X509KeyUsageFlags.KeyEncipherment;
624 // Adapted to System 2.0+ from TlsServerCertificate.cs
625 //------------------------------
626 // Note: this method only works for RSA certificates
627 // DH certificates requires some changes - does anyone use one ?
628 static bool CheckCertificateUsage (X509Certificate2 cert)
631 // certificate extensions are required for this
632 // we "must" accept older certificates without proofs
633 if (cert.Version < 3)
636 X509KeyUsageExtension kux = (cert.Extensions ["2.5.29.15"] as X509KeyUsageExtension);
637 X509EnhancedKeyUsageExtension eku = (cert.Extensions ["2.5.29.37"] as X509EnhancedKeyUsageExtension);
638 if (kux != null && eku != null) {
639 // RFC3280 states that when both KeyUsageExtension and
640 // ExtendedKeyUsageExtension are present then BOTH should
642 if ((kux.KeyUsages & s_flags) == 0)
644 return eku.EnhancedKeyUsages ["1.3.6.1.5.5.7.3.1"] != null ||
645 eku.EnhancedKeyUsages ["2.16.840.1.113730.4.1"] != null;
646 } else if (kux != null) {
647 return ((kux.KeyUsages & s_flags) != 0);
648 } else if (eku != null) {
649 // Server Authentication (1.3.6.1.5.5.7.3.1) or
650 // Netscape Server Gated Crypto (2.16.840.1.113730.4)
651 return eku.EnhancedKeyUsages ["1.3.6.1.5.5.7.3.1"] != null ||
652 eku.EnhancedKeyUsages ["2.16.840.1.113730.4.1"] != null;
655 // last chance - try with older (deprecated) Netscape extensions
656 X509Extension ext = cert.Extensions ["2.16.840.1.113730.1.1"];
658 string text = ext.NetscapeCertType (false);
659 return text.IndexOf ("SSL Server Authentication", StringComparison.Ordinal) != -1;
662 } catch (Exception e) {
663 Console.Error.WriteLine ("ERROR processing certificate: {0}", e);
664 Console.Error.WriteLine ("Please, report this problem to the Mono team");
669 // RFC2818 - HTTP Over TLS, Section 3.1
670 // http://www.ietf.org/rfc/rfc2818.txt
672 // 1. if present MUST use subjectAltName dNSName as identity
673 // 1.1. if multiples entries a match of any one is acceptable
674 // 1.2. wildcard * is acceptable
675 // 2. URI may be an IP address -> subjectAltName.iPAddress
676 // 2.1. exact match is required
677 // 3. Use of the most specific Common Name (CN=) in the Subject
678 // 3.1 Existing practice but DEPRECATED
679 static bool CheckServerIdentity (Mono.Security.X509.X509Certificate cert, string targetHost)
682 Mono.Security.X509.X509Extension ext = cert.Extensions ["2.5.29.17"];
685 SubjectAltNameExtension subjectAltName = new SubjectAltNameExtension (ext);
686 // 1.1 - multiple dNSName
687 foreach (string dns in subjectAltName.DNSNames) {
688 // 1.2 TODO - wildcard support
689 if (Match (targetHost, dns))
693 foreach (string ip in subjectAltName.IPAddresses) {
694 // 2.1. Exact match required
695 if (ip == targetHost)
699 // 3. Common Name (CN=)
700 return CheckDomainName (cert.SubjectName, targetHost);
701 } catch (Exception e) {
702 Console.Error.WriteLine ("ERROR processing certificate: {0}", e);
703 Console.Error.WriteLine ("Please, report this problem to the Mono team");
708 static bool CheckDomainName (string subjectName, string targetHost)
710 string domainName = String.Empty;
711 Regex search = new Regex(@"CN\s*=\s*([^,]*)");
712 MatchCollection elements = search.Matches(subjectName);
713 if (elements.Count == 1) {
714 if (elements[0].Success)
715 domainName = elements[0].Groups[1].Value.ToString();
718 return Match (targetHost, domainName);
721 // ensure the pattern is valid wrt to RFC2595 and RFC2818
722 // http://www.ietf.org/rfc/rfc2595.txt
723 // http://www.ietf.org/rfc/rfc2818.txt
724 static bool Match (string hostname, string pattern)
726 // check if this is a pattern
727 int index = pattern.IndexOf ('*');
729 // not a pattern, do a direct case-insensitive comparison
730 return (String.Compare (hostname, pattern, true, CultureInfo.InvariantCulture) == 0);
733 // check pattern validity
734 // A "*" wildcard character MAY be used as the left-most name component in the certificate.
736 // unless this is the last char (valid)
737 if (index != pattern.Length - 1) {
738 // then the next char must be a dot .'.
739 if (pattern [index + 1] != '.')
743 // only one (A) wildcard is supported
744 int i2 = pattern.IndexOf ('*', index + 1);
748 // match the end of the pattern
749 string end = pattern.Substring (index + 1);
750 int length = hostname.Length - end.Length;
751 // no point to check a pattern that is longer than the hostname
755 if (String.Compare (hostname, length, end, 0, end.Length, true, CultureInfo.InvariantCulture) != 0)
758 // special case, we start with the wildcard
760 // ensure we hostname non-matched part (start) doesn't contain a dot
761 int i3 = hostname.IndexOf ('.');
762 return ((i3 == -1) || (i3 >= (hostname.Length - end.Length)));
765 // match the start of the pattern
766 string start = pattern.Substring (0, index);
767 return (String.Compare (hostname, 0, start, 0, start.Length, true, CultureInfo.InvariantCulture) == 0);