mcs/class/corlib/System.Security.Policy/PolicyLevel.cs

   1 //
   2 // System.Security.Policy.PolicyLevel.cs
   3 //
   4 // Authors:
   5 //      Nick Drochak (ndrochak@gol.com)
   6 //      Duncan Mak (duncan@ximian.com)
   7 //      Sebastien Pouliot  <sebastien@ximian.com>
   8 //
   9 // (C) 2001 Nick Drochak
  10 // (C) 2003 Duncan Mak, Ximian Inc.
  11 // Portions (C) 2004 Motus Technologies Inc. (http://www.motus.com)
  12 // Copyright (C) 2004-2005 Novell, Inc (http://www.novell.com)
  13 //
  14 // Permission is hereby granted, free of charge, to any person obtaining
  15 // a copy of this software and associated documentation files (the
  16 // "Software"), to deal in the Software without restriction, including
  17 // without limitation the rights to use, copy, modify, merge, publish,
  18 // distribute, sublicense, and/or sell copies of the Software, and to
  19 // permit persons to whom the Software is furnished to do so, subject to
  20 // the following conditions:
  21 //
  22 // The above copyright notice and this permission notice shall be
  23 // included in all copies or substantial portions of the Software.
  24 //
  25 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  26 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  27 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  28 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  29 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  30 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  31 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  32 //
  33
  34 using System.Collections; // for IList
  35 using System.Globalization;
  36 using System.IO;
  37 using System.Reflection;
  38 using System.Runtime.InteropServices;
  39 using System.Security.Permissions;
  40
  41 using Mono.Xml;
  42
  43 namespace System.Security.Policy {
  44
  45         [Serializable]
  46 #if NET_2_0
  47         [ComVisible (true)]
  48 #endif
  49         public sealed class PolicyLevel {
  50
  51                 string label;
  52                 CodeGroup root_code_group;
  53                 private ArrayList full_trust_assemblies;
  54                 private ArrayList named_permission_sets;
  55                 private string _location;
  56                 private PolicyLevelType _type;
  57                 private Hashtable fullNames;
  58                 private SecurityElement xml;
  59
  60                 internal PolicyLevel (string label, PolicyLevelType type)
  61                 {
  62                         this.label = label;
  63                         _type = type;
  64                         full_trust_assemblies = new ArrayList ();
  65                         named_permission_sets = new ArrayList ();
  66                 }
  67
  68                 internal void LoadFromFile (string filename)
  69                 {
  70                         try {
  71                                 // check for policy file
  72                                 if (!File.Exists (filename)) {
  73                                         // if it doesn't exist use the default configuration (like Fx 2.0)
  74                                         // ref: http://blogs.msdn.com/shawnfa/archive/2004/04/21/117833.aspx
  75                                         string defcfg = filename + ".default";
  76                                         if (File.Exists (defcfg)) {
  77                                                 // create policy from default file
  78                                                 File.Copy (defcfg, filename);
  79                                         }
  80                                 }
  81                                 // load security policy configuration
  82                                 if (File.Exists (filename)) {
  83                                         using (StreamReader sr = File.OpenText (filename)) {
  84                                                 xml = FromString (sr.ReadToEnd ());
  85                                                 FromXml (xml);
  86                                         }
  87                                 } else {
  88                                         CreateDefaultFullTrustAssemblies ();
  89                                         CreateDefaultNamedPermissionSets ();
  90                                         CreateDefaultLevel (_type);
  91                                         Save ();
  92                                 }
  93                         }
  94                         catch {
  95                                 // this can fail in many ways including...
  96                                 // * can't lookup policy (path discovery);
  97                                 // * can't copy default file to policy
  98                                 // * can't read policy file;
  99                                 // * can't decode policy file
 100                                 // * can't save hardcoded policy to filename
 101                         }
 102                         finally {
 103                                 _location = filename;
 104                         }
 105                 }
 106
 107                 internal void LoadFromString (string xml)
 108                 {
 109                         FromXml (FromString (xml));
 110                 }
 111
 112                 private SecurityElement FromString (string xml)
 113                 {
 114                         SecurityParser parser = new SecurityParser ();
 115                         parser.LoadXml (xml);
 116                         // configuration / mscorlib / security / policy / PolicyLevel
 117                         SecurityElement configuration = parser.ToXml ();
 118                         if (configuration.Tag != "configuration")
 119                                 throw new ArgumentException (Locale.GetText ("missing <configuration> root element"));
 120                         SecurityElement mscorlib = (SecurityElement) configuration.Children [0];
 121                         if (mscorlib.Tag != "mscorlib")
 122                                 throw new ArgumentException (Locale.GetText ("missing <mscorlib> tag"));
 123                         SecurityElement security = (SecurityElement) mscorlib.Children [0];
 124                         if (security.Tag != "security")
 125                                 throw new ArgumentException (Locale.GetText ("missing <security> tag"));
 126                         SecurityElement policy = (SecurityElement) security.Children [0];
 127                         if (policy.Tag != "policy")
 128                                 throw new ArgumentException (Locale.GetText ("missing <policy> tag"));
 129                         SecurityElement policyLevel = (SecurityElement) policy.Children [0];
 130                         return policyLevel;
 131                 }
 132
 133                 // properties
 134
 135                 public IList FullTrustAssemblies {
 136                         get { return full_trust_assemblies; }
 137                 }
 138
 139                 public string Label {
 140                         get { return label; }
 141                 }
 142
 143                 public IList NamedPermissionSets {
 144                         get { return named_permission_sets; }
 145                 }
 146
 147                 public CodeGroup RootCodeGroup {
 148                         get { return root_code_group; }
 149                         set {
 150                                 if (value == null)
 151                                         throw new ArgumentNullException ("value");
 152                                 root_code_group = value;
 153                         }
 154                 }
 155
 156                 public string StoreLocation {
 157                         get { return _location; }
 158                 }
 159
 160 #if NET_2_0
 161                 [ComVisible (false)]
 162                 public PolicyLevelType Type {
 163                         get { return _type; }
 164                 }
 165 #endif
 166
 167                 // methods
 168
 169                 public void AddFullTrustAssembly (StrongName sn)
 170                 {
 171                         if (sn == null)
 172                                 throw new ArgumentNullException ("sn");
 173
 174                         StrongNameMembershipCondition snMC = new StrongNameMembershipCondition(
 175                                 sn.PublicKey, sn.Name, sn.Version);
 176
 177                         AddFullTrustAssembly (snMC);
 178                 }
 179
 180                 public void AddFullTrustAssembly (StrongNameMembershipCondition snMC)
 181                 {
 182                         if (snMC == null)
 183                                 throw new ArgumentNullException ("snMC");
 184
 185                         foreach (StrongNameMembershipCondition sn in full_trust_assemblies) {
 186                                 if (sn.Equals (snMC)) {
 187                                         throw new ArgumentException (Locale.GetText ("sn already has full trust."));
 188                                 }
 189                         }
 190                         full_trust_assemblies.Add (snMC);
 191                 }
 192
 193                 public void AddNamedPermissionSet (NamedPermissionSet permSet)
 194                 {
 195                         if (permSet == null)
 196                                 throw new ArgumentNullException ("permSet");
 197
 198                         foreach (NamedPermissionSet n in named_permission_sets) {
 199                                 if (permSet.Name == n.Name) {
 200                                         throw new ArgumentException (
 201                                                 Locale.GetText ("This NamedPermissionSet is the same an existing NamedPermissionSet."));
 202                                 }
 203                         }
 204                         named_permission_sets.Add (permSet.Copy ());
 205                 }
 206
 207                 public NamedPermissionSet ChangeNamedPermissionSet (string name, PermissionSet pSet)
 208                 {
 209                         if (name == null)
 210                                 throw new ArgumentNullException ("name");
 211                         if (pSet == null)
 212                                 throw new ArgumentNullException ("pSet");
 213                         if (DefaultPolicies.ReservedNames.IsReserved (name))
 214                                 throw new ArgumentException (Locale.GetText ("Reserved name"));
 215
 216                         foreach (NamedPermissionSet n in named_permission_sets) {
 217                                 if (name == n.Name) {
 218                                         named_permission_sets.Remove (n);
 219                                         AddNamedPermissionSet (new NamedPermissionSet (name, pSet));
 220                                         return n;
 221                                 }
 222                         }
 223                         throw new ArgumentException (Locale.GetText ("PermissionSet not found"));
 224                 }
 225
 226                 public static PolicyLevel CreateAppDomainLevel ()
 227                 {
 228                         UnionCodeGroup cg = new UnionCodeGroup (new AllMembershipCondition (), new PolicyStatement (DefaultPolicies.FullTrust));
 229                         cg.Name = "All_Code";
 230                         PolicyLevel pl = new PolicyLevel ("AppDomain", PolicyLevelType.AppDomain);
 231                         pl.RootCodeGroup = cg;
 232                         pl.Reset ();
 233                         return pl;
 234                 }
 235
 236
 237                 public void FromXml (SecurityElement e)
 238                 {
 239                         if (e == null)
 240                                 throw new ArgumentNullException ("e");
 241 // MS doesn't throw an exception for this case
 242 //                      if (e.Tag != "PolicyLevel")
 243 //                              throw new ArgumentException (Locale.GetText ("Invalid XML"));
 244
 245                         SecurityElement sc = e.SearchForChildByTag ("SecurityClasses");
 246                         if ((sc != null) && (sc.Children != null) && (sc.Children.Count > 0)) {
 247                                 fullNames = new Hashtable (sc.Children.Count);
 248                                 foreach (SecurityElement se in sc.Children) {
 249                                         fullNames.Add (se.Attributes ["Name"], se.Attributes ["Description"]);
 250                                 }
 251                         }
 252
 253                         SecurityElement fta = e.SearchForChildByTag ("FullTrustAssemblies");
 254                         if ((fta != null) && (fta.Children != null) && (fta.Children.Count > 0)) {
 255                                 full_trust_assemblies.Clear ();
 256                                 foreach (SecurityElement se in fta.Children) {
 257                                         if (se.Tag != "IMembershipCondition")
 258                                                 throw new ArgumentException (Locale.GetText ("Invalid XML"));
 259                                         string className = se.Attribute ("class");
 260                                         if (className.IndexOf ("StrongNameMembershipCondition") < 0)
 261                                                 throw new ArgumentException (Locale.GetText ("Invalid XML - must be StrongNameMembershipCondition"));
 262                                         // we directly use StrongNameMembershipCondition
 263                                         full_trust_assemblies.Add (new StrongNameMembershipCondition (se));
 264                                 }
 265                         }
 266
 267                         SecurityElement cg = e.SearchForChildByTag ("CodeGroup");
 268                         if ((cg != null) && (cg.Children != null) && (cg.Children.Count > 0)) {
 269                                 root_code_group = CodeGroup.CreateFromXml (cg, this);
 270                         } else {
 271                                 throw new ArgumentException (Locale.GetText ("Missing Root CodeGroup"));
 272                         }
 273
 274                         SecurityElement nps = e.SearchForChildByTag ("NamedPermissionSets");
 275                         if ((nps != null) && (nps.Children != null) && (nps.Children.Count > 0)) {
 276                                 named_permission_sets.Clear ();
 277                                 foreach (SecurityElement se in nps.Children) {
 278                                         NamedPermissionSet n = new NamedPermissionSet ();
 279                                         n.Resolver = this;
 280                                         n.FromXml (se);
 281                                         named_permission_sets.Add (n);
 282                                 }
 283                         }
 284                 }
 285
 286                 public NamedPermissionSet GetNamedPermissionSet (string name)
 287                 {
 288                         if (name == null)
 289                                 throw new ArgumentNullException ("name");
 290
 291                         foreach (NamedPermissionSet n in named_permission_sets) {
 292                                 if (n.Name == name)
 293                                         return (NamedPermissionSet) n.Copy ();
 294                         }
 295                         return null;
 296                 }
 297
 298                 public void Recover ()
 299                 {
 300                         if (_location == null) {
 301                                 string msg = Locale.GetText ("Only file based policies may be recovered.");
 302                                 throw new PolicyException (msg);
 303                         }
 304
 305                         string backup = _location + ".backup";
 306                         if (!File.Exists (backup)) {
 307                                 string msg = Locale.GetText ("No policy backup exists.");
 308                                 throw new PolicyException (msg);
 309                         }
 310
 311                         try {
 312                                 File.Copy (backup, _location, true);
 313                         }
 314                         catch (Exception e) {
 315                                 string msg = Locale.GetText ("Couldn't replace the policy file with it's backup.");
 316                                 throw new PolicyException (msg, e);
 317                         }
 318                 }
 319
 320                 public void RemoveFullTrustAssembly (StrongName sn)
 321                 {
 322                         if (sn == null)
 323                                 throw new ArgumentNullException ("sn");
 324
 325                         StrongNameMembershipCondition s = new StrongNameMembershipCondition (sn.PublicKey, sn.Name, sn.Version);
 326                         RemoveFullTrustAssembly (s);
 327                 }
 328
 329                 public void RemoveFullTrustAssembly (StrongNameMembershipCondition snMC)
 330                 {
 331                         if (snMC == null)
 332                                 throw new ArgumentNullException ("snMC");
 333
 334                         if (((IList) full_trust_assemblies).Contains (snMC))
 335                                 ((IList) full_trust_assemblies).Remove (snMC);
 336
 337                         else
 338                                 throw new ArgumentException (
 339                                         Locale.GetText ("sn does not have full trust."));
 340                 }
 341
 342                 public NamedPermissionSet RemoveNamedPermissionSet (NamedPermissionSet permSet)
 343                 {
 344                         if (permSet == null)
 345                                 throw new ArgumentNullException ("permSet");
 346
 347                         return RemoveNamedPermissionSet (permSet.Name);
 348                 }
 349
 350                 public NamedPermissionSet RemoveNamedPermissionSet (string name)
 351                 {
 352                         if (name == null)
 353                                 throw new ArgumentNullException ("name");
 354                         if (DefaultPolicies.ReservedNames.IsReserved (name))
 355                                 throw new ArgumentException (Locale.GetText ("Reserved name"));
 356
 357                         foreach (NamedPermissionSet nps in named_permission_sets) {
 358                                 if (name == nps.Name) {
 359                                         named_permission_sets.Remove (nps);
 360                                         return nps;
 361                                 }
 362                         }
 363                         string msg = String.Format (Locale.GetText ("Name '{0}' cannot be found."), name);
 364                         throw new ArgumentException (msg, "name");
 365                 }
 366
 367                 public void Reset ()
 368                 {
 369                         if (fullNames != null)
 370                                 fullNames.Clear ();
 371
 372                         if (_type != PolicyLevelType.AppDomain) {
 373                                 full_trust_assemblies.Clear ();
 374                                 named_permission_sets.Clear ();
 375
 376                                 // because the policy doesn't exist LoadFromFile will try to
 377                                 // 1. use the .default file if existing (like Fx 2.0 does); or
 378                                 // 2. use the hard-coded default values
 379                                 // and recreate a policy file
 380                                 if ((_location != null) && (File.Exists (_location))) {
 381                                         try {
 382                                                 File.Delete (_location);
 383                                         }
 384                                         catch {}
 385                                 }
 386                                 LoadFromFile (_location);
 387                         } else {
 388                                 CreateDefaultFullTrustAssemblies ();
 389                                 CreateDefaultNamedPermissionSets ();
 390                         }
 391                 }
 392
 393                 public PolicyStatement Resolve (Evidence evidence)
 394                 {
 395                         if (evidence == null)
 396                                 throw new ArgumentNullException ("evidence");
 397
 398                         PolicyStatement ps = root_code_group.Resolve (evidence);
 399                         return ((ps != null) ? ps : PolicyStatement.Empty ());
 400                 }
 401
 402                 public CodeGroup ResolveMatchingCodeGroups (Evidence evidence)
 403                 {
 404                         if (evidence == null)
 405                                 throw new ArgumentNullException ("evidence");
 406
 407                         CodeGroup cg = root_code_group.ResolveMatchingCodeGroups (evidence);
 408                         return ((cg != null) ? cg : null);
 409                 }
 410
 411                 public SecurityElement ToXml ()
 412                 {
 413                         Hashtable fullNames = new Hashtable ();
 414                         // only StrongNameMembershipCondition so no need to loop
 415                         if (full_trust_assemblies.Count > 0) {
 416                                 if (!fullNames.Contains ("StrongNameMembershipCondition")) {
 417                                         fullNames.Add ("StrongNameMembershipCondition", typeof (StrongNameMembershipCondition).FullName);
 418                                 }
 419                         }
 420
 421                         SecurityElement namedPSs = new SecurityElement ("NamedPermissionSets");
 422                         foreach (NamedPermissionSet nps in named_permission_sets) {
 423                                 SecurityElement se = nps.ToXml ();
 424                                 object objectClass = se.Attributes ["class"];
 425                                 if (!fullNames.Contains (objectClass)) {
 426                                         fullNames.Add (objectClass, nps.GetType ().FullName);
 427                                 }
 428                                 namedPSs.AddChild (se);
 429                         }
 430
 431                         SecurityElement fta = new SecurityElement ("FullTrustAssemblies");
 432                         foreach (StrongNameMembershipCondition snmc in full_trust_assemblies) {
 433                                 fta.AddChild (snmc.ToXml (this));
 434                         }
 435
 436                         SecurityElement security_classes = new SecurityElement ("SecurityClasses");
 437                         if (fullNames.Count > 0) {
 438                                 foreach (DictionaryEntry de in fullNames) {
 439                                         SecurityElement sc = new SecurityElement ("SecurityClass");
 440                                         sc.AddAttribute ("Name", (string)de.Key);
 441                                         sc.AddAttribute ("Description", (string)de.Value);
 442                                         security_classes.AddChild (sc);
 443                                 }
 444                         }
 445
 446                         SecurityElement element = new SecurityElement (typeof (System.Security.Policy.PolicyLevel).Name);
 447                         element.AddAttribute ("version", "1");
 448                         element.AddChild (security_classes);
 449                         element.AddChild (namedPSs);
 450                         if (root_code_group != null) {
 451                                 element.AddChild (root_code_group.ToXml (this));
 452                         }
 453                         element.AddChild (fta);
 454
 455                         return element;
 456                 }
 457
 458                 // internal stuff
 459
 460                 // NOTE: Callers are expected to check for ControlPolicy
 461                 internal void Save ()
 462                 {
 463                         if (_type == PolicyLevelType.AppDomain) {
 464                                 throw new PolicyException (Locale.GetText (
 465                                         "Can't save AppDomain PolicyLevel"));
 466                         }
 467
 468                         if (_location != null) {
 469                                 try {
 470                                         if (File.Exists (_location)) {
 471                                                 File.Copy (_location, _location + ".backup", true);
 472                                         }
 473                                 }
 474                                 catch (Exception) {
 475                                 }
 476                                 finally {
 477                                         using (StreamWriter sw = new StreamWriter (_location)) {
 478                                                 sw.Write (ToXml ().ToString ());
 479                                                 sw.Close ();
 480                                         }
 481                                 }
 482                         }
 483                 }
 484
 485                 // Hardcode defaults in case
 486                 // (a) the specified policy file doesn't exists; and
 487                 // (b) no corresponding default policy file exists
 488                 internal void CreateDefaultLevel (PolicyLevelType type)
 489                 {
 490                         PolicyStatement psu = new PolicyStatement (DefaultPolicies.FullTrust);
 491
 492                         switch (type) {
 493                         case PolicyLevelType.Machine:
 494                                 // by default all stuff is in the machine policy...
 495                                 PolicyStatement psn = new PolicyStatement (DefaultPolicies.Nothing);
 496                                 root_code_group = new UnionCodeGroup (new AllMembershipCondition (), psn);
 497                                 root_code_group.Name = "All_Code";
 498
 499                                 UnionCodeGroup myComputerZone = new UnionCodeGroup (new ZoneMembershipCondition (SecurityZone.MyComputer), psu);
 500                                 myComputerZone.Name = "My_Computer_Zone";
 501                                 // TODO: strongname code group for ECMA and MS keys
 502                                 root_code_group.AddChild (myComputerZone);
 503
 504                                 UnionCodeGroup localIntranetZone = new UnionCodeGroup (new ZoneMembershipCondition (SecurityZone.Intranet),
 505                                         new PolicyStatement (DefaultPolicies.LocalIntranet));
 506                                 localIntranetZone.Name = "LocalIntranet_Zone";
 507                                 // TODO: same site / same directory
 508                                 root_code_group.AddChild (localIntranetZone);
 509
 510                                 PolicyStatement psi = new PolicyStatement (DefaultPolicies.Internet);
 511                                 UnionCodeGroup internetZone = new UnionCodeGroup (new ZoneMembershipCondition (SecurityZone.Internet), psi);
 512                                 internetZone.Name = "Internet_Zone";
 513                                 // TODO: same site
 514                                 root_code_group.AddChild (internetZone);
 515
 516                                 UnionCodeGroup restrictedZone = new UnionCodeGroup (new ZoneMembershipCondition (SecurityZone.Untrusted), psn);
 517                                 restrictedZone.Name = "Restricted_Zone";
 518                                 root_code_group.AddChild (restrictedZone);
 519
 520                                 UnionCodeGroup trustedZone = new UnionCodeGroup (new ZoneMembershipCondition (SecurityZone.Trusted), psi);
 521                                 trustedZone.Name = "Trusted_Zone";
 522                                 // TODO: same site
 523                                 root_code_group.AddChild (trustedZone);
 524                                 break;
 525                         case PolicyLevelType.User:
 526                         case PolicyLevelType.Enterprise:
 527                         case PolicyLevelType.AppDomain:
 528                                 // while the other policies don't restrict anything
 529                                 root_code_group = new UnionCodeGroup (new AllMembershipCondition (), psu);
 530                                 root_code_group.Name = "All_Code";
 531                                 break;
 532                         }
 533                 }
 534
 535                 internal void CreateDefaultFullTrustAssemblies ()
 536                 {
 537                         // (default) assemblies that are fully trusted during policy resolution
 538                         full_trust_assemblies.Clear ();
 539                         full_trust_assemblies.Add (DefaultPolicies.FullTrustMembership ("mscorlib", DefaultPolicies.Key.Ecma));
 540                         full_trust_assemblies.Add (DefaultPolicies.FullTrustMembership ("System", DefaultPolicies.Key.Ecma));
 541                         full_trust_assemblies.Add (DefaultPolicies.FullTrustMembership ("System.Data", DefaultPolicies.Key.Ecma));
 542                         full_trust_assemblies.Add (DefaultPolicies.FullTrustMembership ("System.DirectoryServices", DefaultPolicies.Key.MsFinal));
 543                         full_trust_assemblies.Add (DefaultPolicies.FullTrustMembership ("System.Drawing", DefaultPolicies.Key.MsFinal));
 544                         full_trust_assemblies.Add (DefaultPolicies.FullTrustMembership ("System.Messaging", DefaultPolicies.Key.MsFinal));
 545                         full_trust_assemblies.Add (DefaultPolicies.FullTrustMembership ("System.ServiceProcess", DefaultPolicies.Key.MsFinal));
 546                 }
 547
 548                 internal void CreateDefaultNamedPermissionSets ()
 549                 {
 550                         named_permission_sets.Clear ();
 551                         named_permission_sets.Add (DefaultPolicies.LocalIntranet);
 552                         named_permission_sets.Add (DefaultPolicies.Internet);
 553                         named_permission_sets.Add (DefaultPolicies.SkipVerification);
 554                         named_permission_sets.Add (DefaultPolicies.Execution);
 555                         named_permission_sets.Add (DefaultPolicies.Nothing);
 556                         named_permission_sets.Add (DefaultPolicies.Everything);
 557                         named_permission_sets.Add (DefaultPolicies.FullTrust);
 558                 }
 559
 560                 internal string ResolveClassName (string className)
 561                 {
 562                         if (fullNames != null) {
 563                                 object name = fullNames [className];
 564                                 if (name != null)
 565                                         return (string) name;
 566                         }
 567                         return className;
 568                 }
 569
 570                 internal bool IsFullTrustAssembly (Assembly a)
 571                 {
 572                         AssemblyName an = a.UnprotectedGetName ();
 573                         StrongNamePublicKeyBlob snpkb = new StrongNamePublicKeyBlob (an.GetPublicKey ());
 574                         StrongNameMembershipCondition snMC = new StrongNameMembershipCondition (snpkb, an.Name, an.Version);
 575                         foreach (StrongNameMembershipCondition sn in full_trust_assemblies) {
 576                                 if (sn.Equals (snMC)) {
 577                                         return true;
 578                                 }
 579                         }
 580                         return false;
 581                 }
 582         }
 583 }