mcs/class/Mono.Security/Mono.Security.Protocol.Tls.Handshake.Client/TlsServerCertificate.cs

   1 // Transport Security Layer (TLS)
   2 // Copyright (c) 2003-2004 Carlos Guzman Alvarez
   3 // Copyright (C) 2004, 2006 Novell, Inc (http://www.novell.com)
   4 //
   5 // Permission is hereby granted, free of charge, to any person obtaining
   6 // a copy of this software and associated documentation files (the
   7 // "Software"), to deal in the Software without restriction, including
   8 // without limitation the rights to use, copy, modify, merge, publish,
   9 // distribute, sublicense, and/or sell copies of the Software, and to
  10 // permit persons to whom the Software is furnished to do so, subject to
  11 // the following conditions:
  12 //
  13 // The above copyright notice and this permission notice shall be
  14 // included in all copies or substantial portions of the Software.
  15 //
  16 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  17 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  18 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  19 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  20 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  21 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  22 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  23 //
  24
  25 using System;
  26 using System.Net;
  27 using System.Collections;
  28 using System.Globalization;
  29 using System.Text.RegularExpressions;
  30 using System.Security.Cryptography;
  31 using X509Cert = System.Security.Cryptography.X509Certificates;
  32
  33 using Mono.Security.X509;
  34 using Mono.Security.X509.Extensions;
  35
  36 namespace Mono.Security.Protocol.Tls.Handshake.Client
  37 {
  38         internal class TlsServerCertificate : HandshakeMessage
  39         {
  40                 #region Fields
  41
  42                 private X509CertificateCollection certificates;
  43
  44                 #endregion
  45
  46                 #region Constructors
  47
  48                 public TlsServerCertificate(Context context, byte[] buffer)
  49                         : base(context, HandshakeType.Certificate, buffer)
  50                 {
  51                 }
  52
  53                 #endregion
  54
  55                 #region Methods
  56
  57                 public override void Update()
  58                 {
  59                         base.Update();
  60                         this.Context.ServerSettings.Certificates = this.certificates;
  61                         this.Context.ServerSettings.UpdateCertificateRSA();
  62                 }
  63
  64                 #endregion
  65
  66                 #region Protected Methods
  67
  68                 protected override void ProcessAsSsl3()
  69                 {
  70                         this.ProcessAsTls1();
  71                 }
  72
  73                 protected override void ProcessAsTls1()
  74                 {
  75                         this.certificates = new X509CertificateCollection();
  76
  77                         int readed      = 0;
  78                         int length      = this.ReadInt24();
  79
  80                         while (readed < length)
  81                         {
  82                                 // Read certificate length
  83                                 int certLength = ReadInt24();
  84
  85                                 // Increment readed
  86                                 readed += 3;
  87
  88                                 if (certLength > 0)
  89                                 {
  90                                         // Read certificate data
  91                                         byte[] buffer = this.ReadBytes(certLength);
  92
  93                                         // Create a new X509 Certificate
  94                                         X509Certificate certificate = new X509Certificate(buffer);
  95                                         certificates.Add(certificate);
  96
  97                                         readed += certLength;
  98
  99                                         DebugHelper.WriteLine(
 100                                                 String.Format("Server Certificate {0}", certificates.Count),
 101                                                 buffer);
 102                                 }
 103                         }
 104
 105                         this.validateCertificates(certificates);
 106                 }
 107
 108                 #endregion
 109
 110                 #region Private Methods
 111
 112                 // Note: this method only works for RSA certificates
 113                 // DH certificates requires some changes - does anyone use one ?
 114                 private bool checkCertificateUsage (X509Certificate cert)
 115                 {
 116                         ClientContext context = (ClientContext)this.Context;
 117
 118                         // certificate extensions are required for this
 119                         // we "must" accept older certificates without proofs
 120                         if (cert.Version < 3)
 121                                 return true;
 122
 123                         KeyUsages ku = KeyUsages.none;
 124                         switch (context.Negotiating.Cipher.ExchangeAlgorithmType)
 125                         {
 126                                 case ExchangeAlgorithmType.RsaSign:
 127                                         ku = KeyUsages.digitalSignature;
 128                                         break;
 129                                 case ExchangeAlgorithmType.RsaKeyX:
 130                                         ku = KeyUsages.keyEncipherment;
 131                                         break;
 132                                 case ExchangeAlgorithmType.DiffieHellman:
 133                                         ku = KeyUsages.keyAgreement;
 134                                         break;
 135                                 case ExchangeAlgorithmType.Fortezza:
 136                                         return false; // unsupported certificate type
 137                         }
 138
 139                         KeyUsageExtension kux = null;
 140                         ExtendedKeyUsageExtension eku = null;
 141
 142                         X509Extension xtn = cert.Extensions ["2.5.29.15"];
 143                         if (xtn != null)
 144                                 kux = new KeyUsageExtension (xtn);
 145
 146                         xtn = cert.Extensions ["2.5.29.37"];
 147                         if (xtn != null)
 148                                 eku = new ExtendedKeyUsageExtension (xtn);
 149
 150                         if ((kux != null) && (eku != null))
 151                         {
 152                                 // RFC3280 states that when both KeyUsageExtension and
 153                                 // ExtendedKeyUsageExtension are present then BOTH should
 154                                 // be valid
 155                                 if (!kux.Support (ku))
 156                                         return false;
 157                                 return (eku.KeyPurpose.Contains ("1.3.6.1.5.5.7.3.1") ||
 158                                         eku.KeyPurpose.Contains ("2.16.840.1.113730.4.1"));
 159                         }
 160                         else if (kux != null)
 161                         {
 162                                 return kux.Support (ku);
 163                         }
 164                         else if (eku != null)
 165                         {
 166                                 // Server Authentication (1.3.6.1.5.5.7.3.1) or
 167                                 // Netscape Server Gated Crypto (2.16.840.1.113730.4)
 168                                 return (eku.KeyPurpose.Contains ("1.3.6.1.5.5.7.3.1") ||
 169                                         eku.KeyPurpose.Contains ("2.16.840.1.113730.4.1"));
 170                         }
 171
 172                         // last chance - try with older (deprecated) Netscape extensions
 173                         xtn = cert.Extensions ["2.16.840.1.113730.1.1"];
 174                         if (xtn != null)
 175                         {
 176                                 NetscapeCertTypeExtension ct = new NetscapeCertTypeExtension (xtn);
 177                                 return ct.Support (NetscapeCertTypeExtension.CertTypes.SslServer);
 178                         }
 179
 180                         // certificate isn't valid for SSL server usage
 181                         return false;
 182                 }
 183
 184                 private void validateCertificates(X509CertificateCollection certificates)
 185                 {
 186                         ClientContext           context                 = (ClientContext)this.Context;
 187                         AlertDescription        description             = AlertDescription.BadCertificate;
 188
 189                         // the leaf is the web server certificate
 190                         X509Certificate leaf = certificates [0];
 191                         X509Cert.X509Certificate cert = new X509Cert.X509Certificate (leaf.RawData);
 192
 193                         ArrayList errors = new ArrayList();
 194
 195                         // SSL specific check - not all certificates can be
 196                         // used to server-side SSL some rules applies after
 197                         // all ;-)
 198                         if (!checkCertificateUsage (leaf))
 199                         {
 200                                 // WinError.h CERT_E_PURPOSE 0x800B0106
 201                                 errors.Add ((int)-2146762490);
 202                         }
 203
 204                         // SSL specific check - does the certificate match
 205                         // the host ?
 206                         if (!checkServerIdentity (leaf))
 207                         {
 208                                 // WinError.h CERT_E_CN_NO_MATCH 0x800B010F
 209                                 errors.Add ((int)-2146762481);
 210                         }
 211
 212                         // Note: building and verifying a chain can take much time
 213                         // so we do it last (letting simple things fails first)
 214
 215                         // Note: In TLS the certificates MUST be in order (and
 216                         // optionally include the root certificate) so we're not
 217                         // building the chain using LoadCertificate (it's faster)
 218
 219                         // Note: IIS doesn't seem to send the whole certificate chain
 220                         // but only the server certificate :-( it's assuming that you
 221                         // already have this chain installed on your computer. duh!
 222                         // http://groups.google.ca/groups?q=IIS+server+certificate+chain&hl=en&lr=&ie=UTF-8&oe=UTF-8&selm=85058s%24avd%241%40nnrp1.deja.com&rnum=3
 223
 224                         // we must remove the leaf certificate from the chain
 225                         X509CertificateCollection chain = new X509CertificateCollection (certificates);
 226                         chain.Remove (leaf);
 227                         X509Chain verify = new X509Chain (chain);
 228
 229                         bool result = false;
 230
 231                         try
 232                         {
 233                                 result = verify.Build (leaf);
 234                         }
 235                         catch (Exception)
 236                         {
 237                                 result = false;
 238                         }
 239
 240                         if (!result)
 241                         {
 242                                 switch (verify.Status)
 243                                 {
 244                                         case X509ChainStatusFlags.InvalidBasicConstraints:
 245                                                 // WinError.h TRUST_E_BASIC_CONSTRAINTS 0x80096019
 246                                                 errors.Add ((int)-2146869223);
 247                                                 break;
 248
 249                                         case X509ChainStatusFlags.NotSignatureValid:
 250                                                 // WinError.h TRUST_E_BAD_DIGEST 0x80096010
 251                                                 errors.Add ((int)-2146869232);
 252                                                 break;
 253
 254                                         case X509ChainStatusFlags.NotTimeNested:
 255                                                 // WinError.h CERT_E_VALIDITYPERIODNESTING 0x800B0102
 256                                                 errors.Add ((int)-2146762494);
 257                                                 break;
 258
 259                                         case X509ChainStatusFlags.NotTimeValid:
 260                                                 // WinError.h CERT_E_EXPIRED 0x800B0101
 261                                                 description = AlertDescription.CertificateExpired;
 262                                                 errors.Add ((int)-2146762495);
 263                                                 break;
 264
 265                                         case X509ChainStatusFlags.PartialChain:
 266                                                 // WinError.h CERT_E_CHAINING 0x800B010A
 267                                                 description = AlertDescription.UnknownCA;
 268                                                 errors.Add ((int)-2146762486);
 269                                                 break;
 270
 271                                         case X509ChainStatusFlags.UntrustedRoot:
 272                                                 // WinError.h CERT_E_UNTRUSTEDROOT 0x800B0109
 273                                                 description = AlertDescription.UnknownCA;
 274                                                 errors.Add ((int)-2146762487);
 275                                                 break;
 276
 277                                         default:
 278                                                 // unknown error
 279                                                 description = AlertDescription.CertificateUnknown;
 280                                                 errors.Add ((int)verify.Status);
 281                                                 break;
 282                                 }
 283                         }
 284
 285                         int[] certificateErrors = (int[])errors.ToArray(typeof(int));
 286
 287                         if (!context.SslStream.RaiseServerCertificateValidation(
 288                                 cert,
 289                                 certificateErrors))
 290                         {
 291                                 throw new TlsException(
 292                                         description,
 293                                         "Invalid certificate received form server.");
 294                         }
 295                 }
 296
 297                 // RFC2818 - HTTP Over TLS, Section 3.1
 298                 // http://www.ietf.org/rfc/rfc2818.txt
 299                 //
 300                 // 1.   if present MUST use subjectAltName dNSName as identity
 301                 // 1.1.         if multiples entries a match of any one is acceptable
 302                 // 1.2.         wildcard * is acceptable
 303                 // 2.   URI may be an IP address -> subjectAltName.iPAddress
 304                 // 2.1.         exact match is required
 305                 // 3.   Use of the most specific Common Name (CN=) in the Subject
 306                 // 3.1          Existing practice but DEPRECATED
 307                 private bool checkServerIdentity (X509Certificate cert)
 308                 {
 309                         ClientContext context = (ClientContext)this.Context;
 310
 311                         string targetHost = context.ClientSettings.TargetHost;
 312
 313                         X509Extension ext = cert.Extensions ["2.5.29.17"];
 314                         // 1. subjectAltName
 315                         if (ext != null)
 316                         {
 317                                 SubjectAltNameExtension subjectAltName = new SubjectAltNameExtension (ext);
 318                                 // 1.1 - multiple dNSName
 319                                 foreach (string dns in subjectAltName.DNSNames)
 320                                 {
 321                                         // 1.2 TODO - wildcard support
 322                                         if (dns == targetHost)
 323                                                 return true;
 324                                 }
 325                                 // 2. ipAddress
 326                                 foreach (string ip in subjectAltName.IPAddresses)
 327                                 {
 328                                         // 2.1. Exact match required
 329                                         if (ip == targetHost)
 330                                                 return true;
 331                                 }
 332                         }
 333                         // 3. Common Name (CN=)
 334                         return checkDomainName (cert.SubjectName);
 335                 }
 336
 337                 private bool checkDomainName(string subjectName)
 338                 {
 339                         ClientContext context = (ClientContext)this.Context;
 340
 341                         string  domainName = String.Empty;
 342                         Regex search = new Regex(@"CN\s*=\s*([^,]*)");
 343
 344                         MatchCollection elements = search.Matches(subjectName);
 345
 346                         if (elements.Count == 1)
 347                         {
 348                                 if (elements[0].Success)
 349                                 {
 350                                         domainName = elements[0].Groups[1].Value.ToString();
 351                                 }
 352                         }
 353
 354                         // TODO: add wildcard * support
 355                         return (String.Compare (context.ClientSettings.TargetHost, domainName, true, CultureInfo.InvariantCulture) == 0);
 356
 357                         /*
 358                          * the only document found describing this is:
 359                          * http://www.geocities.com/SiliconValley/Byte/4170/articulos/tls/autentic.htm#Autenticaci%F3n%20del%20Server
 360                          * however I don't see how this could deal with wildcards ?
 361                          * other issues
 362                          * a. there could also be many address returned
 363                          * b. Address property is obsoleted in .NET 1.1
 364                          *
 365                                                 if (domainName == String.Empty)
 366                                                 {
 367                                                         return false;
 368                                                 }
 369                                                 else
 370                                                 {
 371                                                         string targetHost = context.ClientSettings.TargetHost;
 372
 373                                                         // Check that the IP is correct
 374                                                         try
 375                                                         {
 376                                                                 IPAddress       ipHost          = Dns.Resolve(targetHost).AddressList[0];
 377                                                                 IPAddress       ipDomain        = Dns.Resolve(domainName).AddressList[0];
 378
 379                                                                 // Note: Address is obsolete in 1.1
 380                                                                 return (ipHost.Address == ipDomain.Address);
 381                                                         }
 382                                                         catch (Exception)
 383                                                         {
 384                                                                 return false;
 385                                                         }
 386                                                 }*/
 387                 }
 388
 389                 #endregion
 390         }
 391 }