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, 2006-2010 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                         // if the CN=host (checked later) then we assume this is meant for SSL/TLS
 181                         // e.g. the new smtp.gmail.com certificate
 182                         return true;
 183                 }
 184
 185                 private void validateCertificates(X509CertificateCollection certificates)
 186                 {
 187                         ClientContext           context                 = (ClientContext)this.Context;
 188                         AlertDescription        description             = AlertDescription.BadCertificate;
 189
 190 #if INSIDE_SYSTEM
 191                         // This helps the linker to remove a lot of validation code that will never be used since
 192                         // System.dll will, for OSX and iOS, uses the operating system X.509 certificate validations
 193                         RemoteValidation (context, description);
 194 #else
 195                         if (context.SslStream.HaveRemoteValidation2Callback)
 196                                 RemoteValidation (context, description);
 197                         else
 198                                 LocalValidation (context, description);
 199 #endif
 200                 }
 201
 202                 void RemoteValidation (ClientContext context, AlertDescription description)
 203                 {
 204                         ValidationResult res = context.SslStream.RaiseServerCertificateValidation2 (certificates);
 205                         if (res.Trusted)
 206                                 return;
 207
 208                         long error = res.ErrorCode;
 209                         switch (error) {
 210                         case 0x800B0101:
 211                                 description = AlertDescription.CertificateExpired;
 212                                 break;
 213                         case 0x800B010A:
 214                                 description = AlertDescription.UnknownCA;
 215                                 break;
 216                         case 0x800B0109:
 217                                 description = AlertDescription.UnknownCA;
 218                                 break;
 219                         default:
 220                                 description = AlertDescription.CertificateUnknown;
 221                                 break;
 222                         }
 223                         string err = String.Format ("Invalid certificate received from server. Error code: 0x{0:x}", error);
 224                         throw new TlsException (description, err);
 225                 }
 226
 227                 void LocalValidation (ClientContext context, AlertDescription description)
 228                 {
 229                         // the leaf is the web server certificate
 230                         X509Certificate leaf = certificates [0];
 231                         X509Cert.X509Certificate cert = new X509Cert.X509Certificate (leaf.RawData);
 232
 233                         ArrayList errors = new ArrayList();
 234
 235                         // SSL specific check - not all certificates can be
 236                         // used to server-side SSL some rules applies after
 237                         // all ;-)
 238                         if (!checkCertificateUsage (leaf))
 239                         {
 240                                 // WinError.h CERT_E_PURPOSE 0x800B0106
 241                                 errors.Add ((int)-2146762490);
 242                         }
 243
 244                         // SSL specific check - does the certificate match
 245                         // the host ?
 246                         if (!checkServerIdentity (leaf))
 247                         {
 248                                 // WinError.h CERT_E_CN_NO_MATCH 0x800B010F
 249                                 errors.Add ((int)-2146762481);
 250                         }
 251
 252                         // Note: building and verifying a chain can take much time
 253                         // so we do it last (letting simple things fails first)
 254
 255                         // Note: In TLS the certificates MUST be in order (and
 256                         // optionally include the root certificate) so we're not
 257                         // building the chain using LoadCertificate (it's faster)
 258
 259                         // Note: IIS doesn't seem to send the whole certificate chain
 260                         // but only the server certificate :-( it's assuming that you
 261                         // already have this chain installed on your computer. duh!
 262                         // 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
 263
 264                         // we must remove the leaf certificate from the chain
 265                         X509CertificateCollection chain = new X509CertificateCollection (certificates);
 266                         chain.Remove (leaf);
 267                         X509Chain verify = new X509Chain (chain);
 268
 269                         bool result = false;
 270
 271                         try
 272                         {
 273                                 result = verify.Build (leaf);
 274                         }
 275                         catch (Exception)
 276                         {
 277                                 result = false;
 278                         }
 279
 280                         if (!result)
 281                         {
 282                                 switch (verify.Status)
 283                                 {
 284                                         case X509ChainStatusFlags.InvalidBasicConstraints:
 285                                                 // WinError.h TRUST_E_BASIC_CONSTRAINTS 0x80096019
 286                                                 errors.Add ((int)-2146869223);
 287                                                 break;
 288
 289                                         case X509ChainStatusFlags.NotSignatureValid:
 290                                                 // WinError.h TRUST_E_BAD_DIGEST 0x80096010
 291                                                 errors.Add ((int)-2146869232);
 292                                                 break;
 293
 294                                         case X509ChainStatusFlags.NotTimeNested:
 295                                                 // WinError.h CERT_E_VALIDITYPERIODNESTING 0x800B0102
 296                                                 errors.Add ((int)-2146762494);
 297                                                 break;
 298
 299                                         case X509ChainStatusFlags.NotTimeValid:
 300                                                 // WinError.h CERT_E_EXPIRED 0x800B0101
 301                                                 description = AlertDescription.CertificateExpired;
 302                                                 errors.Add ((int)-2146762495);
 303                                                 break;
 304
 305                                         case X509ChainStatusFlags.PartialChain:
 306                                                 // WinError.h CERT_E_CHAINING 0x800B010A
 307                                                 description = AlertDescription.UnknownCA;
 308                                                 errors.Add ((int)-2146762486);
 309                                                 break;
 310
 311                                         case X509ChainStatusFlags.UntrustedRoot:
 312                                                 // WinError.h CERT_E_UNTRUSTEDROOT 0x800B0109
 313                                                 description = AlertDescription.UnknownCA;
 314                                                 errors.Add ((int)-2146762487);
 315                                                 break;
 316
 317                                         default:
 318                                                 // unknown error
 319                                                 description = AlertDescription.CertificateUnknown;
 320                                                 errors.Add ((int)verify.Status);
 321                                                 break;
 322                                 }
 323                         }
 324
 325                         int[] certificateErrors = (int[])errors.ToArray(typeof(int));
 326
 327                         if (!context.SslStream.RaiseServerCertificateValidation(
 328                                 cert,
 329                                 certificateErrors))
 330                         {
 331                                 throw new TlsException(
 332                                         description,
 333                                         "Invalid certificate received from server.");
 334                         }
 335                 }
 336
 337                 // RFC2818 - HTTP Over TLS, Section 3.1
 338                 // http://www.ietf.org/rfc/rfc2818.txt
 339                 //
 340                 // 1.   if present MUST use subjectAltName dNSName as identity
 341                 // 1.1.         if multiples entries a match of any one is acceptable
 342                 // 1.2.         wildcard * is acceptable
 343                 // 2.   URI may be an IP address -> subjectAltName.iPAddress
 344                 // 2.1.         exact match is required
 345                 // 3.   Use of the most specific Common Name (CN=) in the Subject
 346                 // 3.1          Existing practice but DEPRECATED
 347                 private bool checkServerIdentity (X509Certificate cert)
 348                 {
 349                         ClientContext context = (ClientContext)this.Context;
 350
 351                         string targetHost = context.ClientSettings.TargetHost;
 352
 353                         X509Extension ext = cert.Extensions ["2.5.29.17"];
 354                         // 1. subjectAltName
 355                         if (ext != null)
 356                         {
 357                                 SubjectAltNameExtension subjectAltName = new SubjectAltNameExtension (ext);
 358                                 // 1.1 - multiple dNSName
 359                                 foreach (string dns in subjectAltName.DNSNames)
 360                                 {
 361                                         // 1.2 TODO - wildcard support
 362                                         if (Match (targetHost, dns))
 363                                                 return true;
 364                                 }
 365                                 // 2. ipAddress
 366                                 foreach (string ip in subjectAltName.IPAddresses)
 367                                 {
 368                                         // 2.1. Exact match required
 369                                         if (ip == targetHost)
 370                                                 return true;
 371                                 }
 372                         }
 373                         // 3. Common Name (CN=)
 374                         return checkDomainName (cert.SubjectName);
 375                 }
 376
 377                 private bool checkDomainName(string subjectName)
 378                 {
 379                         ClientContext context = (ClientContext)this.Context;
 380
 381                         string  domainName = String.Empty;
 382                         Regex search = new Regex(@"CN\s*=\s*([^,]*)");
 383
 384                         MatchCollection elements = search.Matches(subjectName);
 385
 386                         if (elements.Count == 1)
 387                         {
 388                                 if (elements[0].Success)
 389                                 {
 390                                         domainName = elements[0].Groups[1].Value.ToString();
 391                                 }
 392                         }
 393
 394                         return Match (context.ClientSettings.TargetHost, domainName);
 395                 }
 396
 397                 // ensure the pattern is valid wrt to RFC2595 and RFC2818
 398                 // http://www.ietf.org/rfc/rfc2595.txt
 399                 // http://www.ietf.org/rfc/rfc2818.txt
 400                 static bool Match (string hostname, string pattern)
 401                 {
 402                         // check if this is a pattern
 403                         int index = pattern.IndexOf ('*');
 404                         if (index == -1) {
 405                                 // not a pattern, do a direct case-insensitive comparison
 406                                 return (String.Compare (hostname, pattern, true, CultureInfo.InvariantCulture) == 0);
 407                         }
 408
 409                         // check pattern validity
 410                         // A "*" wildcard character MAY be used as the left-most name component in the certificate.
 411
 412                         // unless this is the last char (valid)
 413                         if (index != pattern.Length - 1) {
 414                                 // then the next char must be a dot .'.
 415                                 if (pattern [index + 1] != '.')
 416                                         return false;
 417                         }
 418
 419                         // only one (A) wildcard is supported
 420                         int i2 = pattern.IndexOf ('*', index + 1);
 421                         if (i2 != -1)
 422                                 return false;
 423
 424                         // match the end of the pattern
 425                         string end = pattern.Substring (index + 1);
 426                         int length = hostname.Length - end.Length;
 427                         // no point to check a pattern that is longer than the hostname
 428                         if (length <= 0)
 429                                 return false;
 430
 431                         if (String.Compare (hostname, length, end, 0, end.Length, true, CultureInfo.InvariantCulture) != 0)
 432                                 return false;
 433
 434                         // special case, we start with the wildcard
 435                         if (index == 0) {
 436                                 // ensure we hostname non-matched part (start) doesn't contain a dot
 437                                 int i3 = hostname.IndexOf ('.');
 438                                 return ((i3 == -1) || (i3 >= (hostname.Length - end.Length)));
 439                         }
 440
 441                         // match the start of the pattern
 442                         string start = pattern.Substring (0, index);
 443                         return (String.Compare (hostname, 0, start, 0, start.Length, true, CultureInfo.InvariantCulture) == 0);
 444                 }
 445
 446                 #endregion
 447         }
 448 }