mcs/class/referencesource/System.Web/misc/SecurityUtils.cs

   1 //------------------------------------------------------------------------------
   2 // <copyright file="SecurityUtils.cs" company="Microsoft">
   3 //     Copyright (c) Microsoft Corporation.  All rights reserved.
   4 // </copyright>
   5 //------------------------------------------------------------------------------
   6
   7 /*
   8  */
   9
  10
  11 #if Microsoft_NAMESPACE
  12     namespace System.Windows.Forms
  13 #elif DRAWING_NAMESPACE
  14     namespace System.Drawing
  15 #elif Microsoft_PUBLIC_GRAPHICS_LIBRARY
  16     namespace System.Internal
  17 #elif SYSTEM_NAMESPACE
  18     namespace System
  19 #elif SYSTEM_WEB
  20     namespace System.Web
  21 #elif SYSTEM_DATA_LINQ
  22     namespace System.Data.Linq
  23 #else
  24 namespace System.Windows.Forms
  25 #endif
  26 {
  27     using System;
  28     using System.Reflection;
  29     using System.Diagnostics.CodeAnalysis;
  30     using System.Security;
  31     using System.Security.Permissions;
  32
  33     /// <devdoc>
  34     ///     Useful methods to securely call 'dangerous' managed APIs (especially reflection).
  35     ///     See http://wiki/default.aspx/Microsoft.Projects.DotNetClient.SecurityConcernsAroundReflection
  36     ///     for more information specifically about why we need to be careful about reflection invocations.
  37     /// </devdoc>
  38     internal static class SecurityUtils {
  39
  40         private static volatile ReflectionPermission memberAccessPermission = null;
  41         private static volatile ReflectionPermission restrictedMemberAccessPermission = null;
  42
  43         private static ReflectionPermission MemberAccessPermission
  44         {
  45             get {
  46                 if (memberAccessPermission == null) {
  47                     memberAccessPermission = new ReflectionPermission(ReflectionPermissionFlag.MemberAccess);
  48                 }
  49                 return memberAccessPermission;
  50             }
  51         }
  52
  53         private static ReflectionPermission RestrictedMemberAccessPermission {
  54             get {
  55                 if (restrictedMemberAccessPermission == null) {
  56                     restrictedMemberAccessPermission = new ReflectionPermission(ReflectionPermissionFlag.RestrictedMemberAccess);
  57                 }
  58                 return restrictedMemberAccessPermission;
  59             }
  60         }
  61
  62         private static void DemandReflectionAccess(Type type) {
  63             try {
  64                 MemberAccessPermission.Demand();
  65             }
  66             catch (SecurityException) {
  67                 DemandGrantSet(type.Assembly);
  68             }
  69         }
  70
  71         [SecuritySafeCritical]
  72         private static void DemandGrantSet(Assembly assembly) {
  73             PermissionSet targetGrantSet = assembly.PermissionSet;
  74             targetGrantSet.AddPermission(RestrictedMemberAccessPermission);
  75             targetGrantSet.Demand();
  76         }
  77
  78         private static bool HasReflectionPermission(Type type) {
  79             try {
  80                 DemandReflectionAccess(type);
  81                 return true;
  82             }
  83             catch (SecurityException) {
  84             }
  85
  86             return false;
  87         }
  88
  89
  90         /// <devdoc>
  91         ///     This helper method provides safe access to Activator.CreateInstance.
  92         ///     NOTE: This overload will work only with public .ctors.
  93         /// </devdoc>
  94         internal static object SecureCreateInstance(Type type) {
  95             return SecureCreateInstance(type, null, false);
  96         }
  97
  98
  99         /// <devdoc>
 100         ///     This helper method provides safe access to Activator.CreateInstance.
 101         ///     Set allowNonPublic to true if you want non public ctors to be used.
 102         /// </devdoc>
 103         internal static object SecureCreateInstance(Type type, object[] args, bool allowNonPublic) {
 104             if (type == null) {
 105                 throw new ArgumentNullException("type");
 106             }
 107
 108             BindingFlags flags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.CreateInstance;
 109
 110             // if it's an internal type, we demand reflection permission.
 111             if (!type.IsVisible) {
 112                 DemandReflectionAccess(type);
 113             }
 114             else if (allowNonPublic && !HasReflectionPermission(type)) {
 115                 // Someone is trying to instantiate a public type in *our* assembly, but does not
 116                 // have full reflection permission. We shouldn't pass BindingFlags.NonPublic in this case.
 117                 // The reason we don't directly demand the permission here is because we don't know whether
 118                 // a public or non-public .ctor will be invoked. We want to allow the public .ctor case to
 119                 // succeed.
 120                 allowNonPublic = false;
 121             }
 122
 123             if (allowNonPublic) {
 124                 flags |= BindingFlags.NonPublic;
 125             }
 126
 127             return Activator.CreateInstance(type, flags, null, args, null);
 128         }
 129
 130 #if (!Microsoft_NAMESPACE)
 131
 132         /// <devdoc>
 133         ///     This helper method provides safe access to Activator.CreateInstance.
 134         ///     NOTE: This overload will work only with public .ctors.
 135         /// </devdoc>
 136         internal static object SecureCreateInstance(Type type, object[] args) {
 137             return SecureCreateInstance(type, args, false);
 138         }
 139
 140
 141         /// <devdoc>
 142         ///     Helper method to safely invoke a .ctor. You should prefer SecureCreateInstance to this.
 143         ///     Set allowNonPublic to true if you want non public ctors to be used.
 144         /// </devdoc>
 145         internal static object SecureConstructorInvoke(Type type, Type[] argTypes, object[] args, bool allowNonPublic) {
 146             return SecureConstructorInvoke(type, argTypes, args, allowNonPublic, BindingFlags.Default);
 147         }
 148
 149         /// <devdoc>
 150         ///     Helper method to safely invoke a .ctor. You should prefer SecureCreateInstance to this.
 151         ///     Set allowNonPublic to true if you want non public ctors to be used.
 152         ///     The 'extraFlags' parameter is used to pass in any other flags you need,
 153         ///     besides Public, NonPublic and Instance.
 154         /// </devdoc>
 155         internal static object SecureConstructorInvoke(Type type, Type[] argTypes, object[] args,
 156                                                        bool allowNonPublic, BindingFlags extraFlags) {
 157             if (type == null) {
 158                 throw new ArgumentNullException("type");
 159             }
 160
 161             // if it's an internal type, we demand reflection permission.
 162             if (!type.IsVisible) {
 163                 DemandReflectionAccess(type);
 164             }
 165             else if (allowNonPublic && !HasReflectionPermission(type)) {
 166                 // Someone is trying to invoke a ctor on a public type, but does not
 167                 // have full reflection permission. We shouldn't pass BindingFlags.NonPublic in this case.
 168                 allowNonPublic = false;
 169             }
 170
 171             BindingFlags flags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | extraFlags;
 172             if (!allowNonPublic) {
 173                 flags &= ~BindingFlags.NonPublic;
 174             }
 175
 176             ConstructorInfo ctor = type.GetConstructor(flags, null, argTypes, null);
 177             if (ctor != null) {
 178                 return ctor.Invoke(args);
 179             }
 180
 181             return null;
 182         }
 183
 184         private static bool GenericArgumentsAreVisible(MethodInfo method) {
 185             if (method.IsGenericMethod) {
 186                 Type[] parameterTypes = method.GetGenericArguments();
 187                 foreach (Type type in parameterTypes) {
 188                     if (!type.IsVisible) {
 189                         return false;
 190                     }
 191                 }
 192             }
 193             return true;
 194         }
 195
 196         /// <devdoc>
 197         ///     This helper method provides safe access to FieldInfo's GetValue method.
 198         /// </devdoc>
 199         internal static object FieldInfoGetValue(FieldInfo field, object target) {
 200             Type type = field.DeclaringType;
 201             if (type == null) {
 202                 // Type is null for Global fields.
 203                 if (!field.IsPublic) {
 204                     DemandGrantSet(field.Module.Assembly);
 205                 }
 206             } else if (!(type != null && type.IsVisible && field.IsPublic)) {
 207                 DemandReflectionAccess(type);
 208             }
 209             return field.GetValue(target);
 210         }
 211
 212         /// <devdoc>
 213         ///     This helper method provides safe access to MethodInfo's Invoke method.
 214         /// </devdoc>
 215         internal static object MethodInfoInvoke(MethodInfo method, object target, object[] args) {
 216             Type type = method.DeclaringType;
 217             if (type == null) {
 218                 // Type is null for Global methods. In this case we would need to demand grant set on
 219                 // the containing assembly for internal methods.
 220                 if (!(method.IsPublic && GenericArgumentsAreVisible(method))) {
 221                     DemandGrantSet(method.Module.Assembly);
 222                 }
 223             } else if (!(type.IsVisible && method.IsPublic && GenericArgumentsAreVisible(method))) {
 224                 // this demand is required for internal types in system.dll and its friend assemblies.
 225                 DemandReflectionAccess(type);
 226             }
 227             return method.Invoke(target, args);
 228         }
 229
 230         /// <devdoc>
 231         ///     This helper method provides safe access to ConstructorInfo's Invoke method.
 232         ///     Constructors can't be generic, so we don't check if argument types are visible
 233         /// </devdoc>
 234         internal static object ConstructorInfoInvoke(ConstructorInfo ctor, object[] args) {
 235             Type type = ctor.DeclaringType;
 236             if ((type != null) && !(type.IsVisible && ctor.IsPublic)) {
 237                 DemandReflectionAccess(type);
 238             }
 239             return ctor.Invoke(args);
 240         }
 241
 242         /// <devdoc>
 243         ///     This helper method provides safe access to Array.CreateInstance.
 244         /// </devdoc>
 245         internal static object ArrayCreateInstance(Type type, int length) {
 246             if (!type.IsVisible) {
 247                 DemandReflectionAccess(type);
 248             }
 249             return Array.CreateInstance(type, length);
 250         }
 251 #endif
 252     }
 253 }