Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web/Security/Cryptography/MachineKeyDataProtectorFactory.cs

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+//------------------------------------------------------------------------------
+// <copyright file="MachineKeyDataProtectorFactory.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+//------------------------------------------------------------------------------
+
+namespace System.Web.Security.Cryptography {
+    using System;
+    using System.Security.Cryptography;
+    using System.Web.Configuration;
+
+    // Can create DataProtector instances from a given <machineKey> element
+
+    internal sealed class MachineKeyDataProtectorFactory : IDataProtectorFactory {
+
+        private static readonly Purpose _creationTestingPurpose = new Purpose("test-1", "test-2", "test-3");
+
+        private Func<Purpose, DataProtector> _dataProtectorFactory;
+        private readonly MachineKeySection _machineKeySection;
+
+        public MachineKeyDataProtectorFactory(MachineKeySection machineKeySection) {
+            _machineKeySection = machineKeySection;
+        }
+
+        public DataProtector GetDataProtector(Purpose purpose) {
+            if (_dataProtectorFactory == null) {
+                _dataProtectorFactory = GetDataProtectorFactory();
+            }
+            return _dataProtectorFactory(purpose);
+        }
+
+        private Func<Purpose, DataProtector> GetDataProtectorFactory() {
+            string applicationName = _machineKeySection.ApplicationName;
+            string dataProtectorTypeName = _machineKeySection.DataProtectorType;
+
+            Func<Purpose, DataProtector> factory = purpose => {
+                // Since the custom implementation might depend on the impersonated
+                // identity, we must instantiate it under app-level impersonation.
+                using (new ApplicationImpersonationContext()) {
+                    return DataProtector.Create(dataProtectorTypeName, applicationName, purpose.PrimaryPurpose, purpose.SpecificPurposes);
+                }
+            };
+
+            // Invoke the factory once to make sure there aren't any configuration errors.
+            Exception factoryCreationException = null;
+            try {
+                DataProtector dataProtector = factory(_creationTestingPurpose);
+                if (dataProtector != null) {
+                    IDisposable disposable = dataProtector as IDisposable;
+                    if (disposable != null) {
+                        disposable.Dispose();
+                    }
+                    return factory; // we know at this point the factory is good
+                }
+            }
+            catch (Exception ex) {
+                factoryCreationException = ex;
+            }
+
+            // If we reached this point, there was a failure:
+            // the factory returned null, threw, or did something else unexpected.
+            throw ConfigUtil.MakeConfigurationErrorsException(
+                message: SR.GetString(SR.MachineKeyDataProtectorFactory_FactoryCreationFailed),
+                innerException: factoryCreationException, // can be null
+                configProperty: _machineKeySection.ElementInformation.Properties["dataProtectorType"]);
+        }
+
+    }
+}