(chocolateyGH-121) Add hash provider

To compute hashes in files, add a hash provider that can determine
hashes of files.

src/chocolatey/chocolatey.csproj

@@ -166,6 +166,8 @@
     <Compile Include="infrastructure\commandline\InteractivePrompt.cs" />
     <Compile Include="infrastructure\commands\ICommandExecutor.cs" />
     <Compile Include="infrastructure\commands\PowershellExecutor.cs" />
+    <Compile Include="infrastructure\cryptography\IHashProvider.cs" />
+    <Compile Include="infrastructure\cryptography\Md5HashProvider.cs" />
     <Compile Include="infrastructure\guards\Ensure.cs" />
     <Compile Include="infrastructure\information\ProcessInformation.cs" />
     <Compile Include="infrastructure\logging\ChocolateyLoggers.cs" />

src/chocolatey/infrastructure.app/registration/ContainerBinding.cs

@@ -20,6 +20,7 @@ namespace chocolatey.infrastructure.app.registration
     using SimpleInjector;
     using adapters;
     using commands;
+    using cryptography;
     using events;
     using filesystem;
     using infrastructure.commands;
@@ -28,6 +29,7 @@ namespace chocolatey.infrastructure.app.registration
     using nuget;
     using services;
     using IFileSystem = filesystem.IFileSystem;
+    using IHashProvider = cryptography.IHashProvider;
 
     // ReSharper disable InconsistentNaming
 
@@ -54,6 +56,7 @@ public void RegisterComponents(Container container)
             container.Register<IShimGenerationService, ShimGenerationService>(Lifestyle.Singleton);
             container.Register<IRegistryService, RegistryService>(Lifestyle.Singleton);
             container.Register<IFilesService, FilesService>(Lifestyle.Singleton);
+            container.Register<IHashProvider, Md5HashProvider>(Lifestyle.Singleton);
             container.Register<ITemplateService, TemplateService>(Lifestyle.Singleton);
             container.Register<IChocolateyConfigSettingsService, ChocolateyConfigSettingsService>(Lifestyle.Singleton);
             container.Register<IChocolateyPackageService, ChocolateyPackageService>(Lifestyle.Singleton);

src/chocolatey/infrastructure/cryptography/IHashProvider.cs

@@ -0,0 +1,30 @@
+// Copyright © 2011 - Present RealDimensions Software, LLC
+// 
+// Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
+// 
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+namespace chocolatey.infrastructure.cryptography
+{
+    /// <summary>
+    /// A hash provider for hashing files
+    /// </summary>
+    public interface IHashProvider
+    {
+        /// <summary>
+        /// Returns a hash of the specified file path.
+        /// </summary>
+        /// <param name="filePath">The file path.</param>
+        /// <returns>A computed hash of the file, based on the contents.</returns>
+        string hash_file(string filePath);
+    }
+}

src/chocolatey/infrastructure/cryptography/Md5HashProvider.cs

@@ -0,0 +1,42 @@
+// Copyright © 2011 - Present RealDimensions Software, LLC
+// 
+// Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
+// 
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+namespace chocolatey.infrastructure.cryptography
+{
+    using System;
+    using System.Security.Cryptography;
+    using filesystem;
+
+    public sealed class Md5HashProvider : IHashProvider
+    {
+        private readonly IFileSystem _fileSystem;
+        private readonly MD5 _cryptoProvider;
+
+        public Md5HashProvider(IFileSystem fileSystem)
+        {
+            _fileSystem = fileSystem;
+            _cryptoProvider = MD5.Create();
+        }
+
+        public string hash_file(string filePath)
+        {
+            if (!_fileSystem.file_exists(filePath)) return string.Empty;
+
+            var hash = _cryptoProvider.ComputeHash(_fileSystem.read_file_bytes(filePath));
+
+            return BitConverter.ToString(hash).Replace("-", string.Empty);
+        }
+    }
+}