//******************************************************************************************************//  InterprocessLock.cs - Gbtc////  Copyright © 2012, Grid Protection Alliance.  All Rights Reserved.////  Licensed to the Grid Protection Alliance (GPA) under one or more contributor license agreements. See//  the NOTICE file distributed with this work for additional information regarding copyright ownership.//  The GPA licenses this file to you under the MIT License (MIT), the "License"; you may//  not use this file except in compliance with the License. You may obtain a copy of the License at:////      http://www.opensource.org/licenses/MIT////  Unless agreed to in writing, the subject software distributed under the License is distributed on an//  "AS-IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. Refer to the//  License for the specific language governing permissions and limitations.////  Code Modification History://  ----------------------------------------------------------------------------------------------------//  03/21/2011 - J. Ritchie Carroll//       Generated original version of source code.//  06/30/2011 - Stephen Wills//       Applying changes from Jian (Ryan) Zuo: updated to allow unauthorized users to attempt to grant//       themselves lower than full access to existing mutexes and semaphores.//  08/12/2011 - J. Ritchie Carroll//       Modified creation methods such that locking natives are created in a synchronized fashion.//  09/21/2011 - J. Ritchie Carroll//       Added Mono implementation exception regions.//  12/14/2012 - Starlynn Danyelle Gilliam//       Modified Header.//  12/18/2013 - J. Ritchie Carroll//       Improved operational behavior.////****************************************************************************************************** using System;using System.Linq;using System.Reflection;using System.Runtime.CompilerServices;using System.Runtime.InteropServices;using System.Security.AccessControl;using System.Security.Principal;using System.Threading;using GSF.Diagnostics;using GSF.Identity;using GSF.Security.Cryptography; namespace GSF.Threading{    /// <summary>    /// Defines helper methods related to inter-process locking.    /// </summary>    public static class InterprocessLock    {        private const int MutexHash = 0;        private const int SemaphoreHash = 1;         /// <summary>        /// Gets a uniquely named inter-process <see cref="Mutex"/> associated with the running application, typically used to detect whether an instance        /// of the application is already running.        /// </summary>        /// <param name="perUser">Indicates whether to generate a different name for the <see cref="Mutex"/> dependent upon the user running the application.</param>        /// <returns>A uniquely named inter-process <see cref="Mutex"/> specific to the application; <see cref="Mutex"/> is created if it does not exist.</returns>        /// <remarks>        /// <para>        /// This function uses a hash of the assembly's GUID when creating the <see cref="Mutex"/>, if it is available. If it is not available, it uses a hash        /// of the simple name of the assembly. Although the name is hashed to help guarantee uniqueness, it is still entirely possible that another application        /// may use that name with the same hashing algorithm to generate its <see cref="Mutex"/> name. Therefore, it is best to ensure that the        /// <see cref="GuidAttribute"/> is defined in the AssemblyInfo of your application.        /// </para>        /// <para>        /// The <see cref="Mutex"/> created is "Global" meaning that it will be accessible to all active application sessions including terminal service        /// sessions. This is accomplished internally by prefixing the <see cref="Mutex"/> name with "Global\". Do not use this helper function if you need        /// to create a specifically named or non-global <see cref="Mutex"/>, such as when you need to interact with another application using a        /// <see cref="Mutex"/> that does not use this function.        /// </para>        /// </remarks>        /// <exception cref="UnauthorizedAccessException">The named mutex exists, but the user does not have the minimum needed security access rights to use it.</exception>        [MethodImpl(MethodImplOptions.Synchronized)]        public static Mutex GetNamedMutex(bool perUser = true)        {            Assembly entryAssembly = Assembly.GetEntryAssembly();            GuidAttribute attribute = (GuidAttribute)entryAssembly.GetCustomAttributes(typeof(GuidAttribute), true).FirstOrDefault();            string name = attribute?.Value ?? entryAssembly.GetName().Name;             if (perUser)                name += UserInfo.CurrentUserID;             return GetNamedMutex(name);        }         /// <summary>        /// Gets a uniquely named inter-process <see cref="Mutex"/> associated with the specified <paramref name="name"/> that identifies a source object        /// needing concurrency locking.        /// </summary>        /// <param name="name">Identifying name of source object needing concurrency locking (e.g., a path and file name).</param>        /// <returns>A uniquely named inter-process <see cref="Mutex"/> specific to <paramref name="name"/>; <see cref="Mutex"/> is created if it does not exist.</returns>        /// <remarks>        /// <para>        /// This function uses a hash of the <paramref name="name"/> when creating the <see cref="Mutex"/>, not the actual <paramref name="name"/> - this way        /// restrictions on the <paramref name="name"/> length do not need to be a user concern. All processes needing an inter-process <see cref="Mutex"/> need        /// to use this same function to ensure access to the same <see cref="Mutex"/>.        /// </para>        /// <para>        /// The <paramref name="name"/> can be a string of any length (must not be empty, null or white space) and is not case-sensitive. All hashes of the        /// <paramref name="name"/> used to create the global <see cref="Mutex"/> are first converted to lower case.        /// </para>        /// <para>        /// The <see cref="Mutex"/> created is "Global" meaning that it will be accessible to all active application sessions including terminal service        /// sessions. This is accomplished internally by prefixing the <see cref="Mutex"/> name with "Global\"; it is not necessary for the user to be        /// concerned with the length or contents of the <paramref name="name"/> in this method as long as the same <paramref name="name"/> is used for        /// each application. Do not use this helper function if you need to create a specifically named or non-global <see cref="Mutex"/>, such as when        /// you need to interact with another application using a <see cref="Mutex"/> that does not use this function.        /// </para>        /// </remarks>        /// <exception cref="ArgumentNullException">Argument <paramref name="name"/> cannot be empty, null or white space.</exception>        /// <exception cref="UnauthorizedAccessException">The named mutex exists, but the user does not have the minimum needed security access rights to use it.</exception>        [MethodImpl(MethodImplOptions.Synchronized)]        public static Mutex GetNamedMutex(string name)        {            if (string.IsNullOrWhiteSpace(name))                throw new ArgumentNullException(nameof(name), "Argument cannot be empty, null or white space.");             Mutex namedMutex;            bool mutexWasCreated;             // Create a mutex name that is specific to an object (e.g., a path and file name).            // Note that we use GetPasswordHash to create a short common name for the name parameter            // that was passed into the function - this allows the parameter to be very long, e.g.,            // a file path, and still meet minimum mutex name requirements.             // Prefix mutex name with "Global\" such that mutex will apply to all active            // application sessions in case terminal services is running.            string mutexName = "Global\\" + Cipher.GetPasswordHash(name.ToLower(), MutexHash).Replace('\\', '-'); #if MONO            // Mono Mutex implementations do not include ability to change access rules            namedMutex = new Mutex(false, mutexName, out mutexWasCreated);#else            bool doesNotExist = false;             // Attempt to open the named mutex            try            {                namedMutex = Mutex.OpenExisting(mutexName, MutexRights.Synchronize | MutexRights.Modify);            }            catch (WaitHandleCannotBeOpenedException ex)            {                Logger.SwallowException(ex, "Common Exception", "Exception expected when mutex does not already exist.");                 namedMutex = null;                doesNotExist = true;            }             // If mutex does not exist we attempt to create it            if (doesNotExist)            {                try                {                    MutexSecurity security = new MutexSecurity();                    security.AddAccessRule(new MutexAccessRule(new SecurityIdentifier(WellKnownSidType.WorldSid, null), MutexRights.Synchronize | MutexRights.Modify, AccessControlType.Allow));                    namedMutex = new Mutex(false, mutexName, out mutexWasCreated, security);                }                catch (UnauthorizedAccessException ex)                {                    Logger.SwallowException(ex, "Common Exception", "Accommodated race condition on mutex creation.");                     // Named mutex exists now but current user doesn't have full control, attempt to open with minimum needed rights                    namedMutex = Mutex.OpenExisting(mutexName, MutexRights.Synchronize | MutexRights.Modify);                }            }#endif             return namedMutex;        }         /// <summary>        /// Gets a uniquely named inter-process <see cref="Semaphore"/> associated with the running application, typically used to detect whether some number of        /// instances of the application are already running.        /// </summary>        /// <param name="perUser">Indicates whether to generate a different name for the <see cref="Semaphore"/> dependent upon the user running the application.</param>        /// <param name="maximumCount">The maximum number of requests for the semaphore that can be granted concurrently.</param>        /// <param name="initialCount">The initial number of requests for the semaphore that can be granted concurrently, or -1 to default to <paramref name="maximumCount"/>.</param>        /// <returns>A uniquely named inter-process <see cref="Semaphore"/> specific to entry assembly; <see cref="Semaphore"/> is created if it does not exist.</returns>        /// <remarks>        /// <para>        /// This function uses a hash of the assembly's GUID when creating the <see cref="Semaphore"/>, if it is available. If it is not available, it uses a hash        /// of the simple name of the assembly. Although the name is hashed to help guarantee uniqueness, it is still entirely possible that another application        /// may use that name with the same hashing algorithm to generate its <see cref="Semaphore"/> name. Therefore, it is best to ensure that the        /// <see cref="GuidAttribute"/> is defined in the AssemblyInfo of your application.        /// </para>        /// <para>        /// The <see cref="Semaphore"/> created is "Global" meaning that it will be accessible to all active application sessions including terminal service        /// sessions. This is accomplished internally by prefixing the <see cref="Semaphore"/> name with "Global\". Do not use this helper function if you need        /// to create a specifically named or non-global <see cref="Semaphore"/>, such as when you need to interact with another application using a        /// <see cref="Semaphore"/> that does not use this function.        /// </para>        /// </remarks>        /// <exception cref="UnauthorizedAccessException">The named semaphore exists, but the user does not have the minimum needed security access rights to use it.</exception>        [MethodImpl(MethodImplOptions.Synchronized)]        public static Semaphore GetNamedSemaphore(bool perUser = true, int maximumCount = 10, int initialCount = -1)        {            Assembly entryAssembly = Assembly.GetEntryAssembly();            GuidAttribute attribute = (GuidAttribute)entryAssembly.GetCustomAttributes(typeof(GuidAttribute), true).FirstOrDefault();            string name = attribute?.Value ?? entryAssembly.GetName().Name;             if (perUser)                name += UserInfo.CurrentUserID;             return GetNamedSemaphore(name, maximumCount, initialCount);        }         /// <summary>        /// Gets a uniquely named inter-process <see cref="Semaphore"/> associated with the specified <paramref name="name"/> that identifies a source object        /// needing concurrency locking.        /// </summary>        /// <param name="name">Identifying name of source object needing concurrency locking (e.g., a path and file name).</param>        /// <param name="maximumCount">The maximum number of requests for the semaphore that can be granted concurrently.</param>        /// <param name="initialCount">The initial number of requests for the semaphore that can be granted concurrently, or -1 to default to <paramref name="maximumCount"/>.</param>        /// <returns>A uniquely named inter-process <see cref="Semaphore"/> specific to <paramref name="name"/>; <see cref="Semaphore"/> is created if it does not exist.</returns>        /// <remarks>        /// <para>        /// This function uses a hash of the <paramref name="name"/> when creating the <see cref="Semaphore"/>, not the actual <paramref name="name"/> - this way        /// restrictions on the <paramref name="name"/> length do not need to be a user concern. All processes needing an inter-process <see cref="Semaphore"/> need        /// to use this same function to ensure access to the same <see cref="Semaphore"/>.        /// </para>        /// <para>        /// The <paramref name="name"/> can be a string of any length (must not be empty, null or white space) and is not case-sensitive. All hashes of the        /// <paramref name="name"/> used to create the global <see cref="Semaphore"/> are first converted to lower case.        /// </para>        /// <para>        /// The <see cref="Semaphore"/> created is "Global" meaning that it will be accessible to all active application sessions including terminal service        /// sessions. This is accomplished internally by prefixing the <see cref="Semaphore"/> name with "Global\"; it is not necessary for the user to be        /// concerned with the length or contents of the <paramref name="name"/> in this method as long as the same <paramref name="name"/> is used for        /// each application. Do not use this helper function if you need to create a specifically named or non-global <see cref="Semaphore"/>, such as when        /// you need to interact with another application using a <see cref="Semaphore"/> that does not use this function.        /// </para>        /// </remarks>        /// <exception cref="ArgumentNullException">Argument <paramref name="name"/> cannot be empty, null or white space.</exception>        /// <exception cref="UnauthorizedAccessException">The named semaphore exists, but the user does not have the minimum needed security access rights to use it.</exception>        [MethodImpl(MethodImplOptions.Synchronized)]        public static Semaphore GetNamedSemaphore(string name, int maximumCount = 10, int initialCount = -1)        {            if (string.IsNullOrWhiteSpace(name))                throw new ArgumentNullException(nameof(name), "Argument cannot be empty, null or white space.");             Semaphore namedSemaphore;            bool semaphoreWasCreated;             if (initialCount < 0)                initialCount = maximumCount;             // Create a semaphore name that is specific to an object (e.g., a path and file name).            // Note that we use GetPasswordHash to create a short common name for the name parameter            // that was passed into the function - this allows the parameter to be very long, e.g.,            // a file path, and still meet minimum semaphore name requirements.             // Prefix semaphore name with "Global\" such that semaphore will apply to all active            // application sessions in case terminal services is running. Note that this is necessary            // even though .NET documentation does not state it - IL disassembly shows direct calls            // to WinAPI OpenSemaphore and CreateSemaphore which clearly document this:            // http://msdn.microsoft.com/en-us/library/windows/desktop/ms684326(v=vs.85).aspx            string semaphoreName = "Global\\" + Cipher.GetPasswordHash(name.ToLower(), SemaphoreHash).Replace('\\', '-'); #if MONO            // Mono Semaphore implementations do not include ability to change access rules            namedSemaphore = new Semaphore(initialCount, maximumCount, semaphoreName, out semaphoreWasCreated);#else            bool doesNotExist = false;             // Attempt to open the named semaphore with minimum needed rights            try            {                namedSemaphore = Semaphore.OpenExisting(semaphoreName, SemaphoreRights.Synchronize | SemaphoreRights.Modify);            }            catch (WaitHandleCannotBeOpenedException ex)            {                Logger.SwallowException(ex, "Common Exception", "Exception expected when semaphore does not already exist.");                 namedSemaphore = null;                doesNotExist = true;            }             // If semaphore does not exist we attempt to create it            if (doesNotExist)            {                try                {                    SemaphoreSecurity security = new SemaphoreSecurity();                    security.AddAccessRule(new SemaphoreAccessRule(new SecurityIdentifier(WellKnownSidType.WorldSid, null), SemaphoreRights.Synchronize | SemaphoreRights.Modify, AccessControlType.Allow));                    namedSemaphore = new Semaphore(initialCount, maximumCount, semaphoreName, out semaphoreWasCreated, security);                }                catch (UnauthorizedAccessException ex)                {                    Logger.SwallowException(ex, "Common Exception", "Accommodated race condition on semaphore creation.");                     // Named semaphore exists now but current user doesn't have full control, attempt to open with minimum needed rights                    namedSemaphore = Semaphore.OpenExisting(semaphoreName, SemaphoreRights.Synchronize | SemaphoreRights.Modify);                }            }#endif             return namedSemaphore;        }    }}