Harden assembly timestamp handling

SacsStandardBase/Base/Utils/AssemblyUtil.cs

@@ -1,62 +1,84 @@
-using System;
+using System;
 using System.IO;
 using System.Reflection;
-using System.Runtime.InteropServices;
 
 namespace Sarand.Net.Standard.Base.Utils
 {
-	//=======================================================================
 	public static class AssemblyUtil
 	{
-		//-------------------------------------------------------------------
-		#region Gets the build date and time (by reading the COFF header)
-		// http://msdn.microsoft.com/en-us/library/ms680313
+		// --- Definitions ---
 
-		struct _IMAGE_FILE_HEADER
-		{
-#pragma warning disable CS0649
-			public ushort Machine;
-			public ushort NumberOfSections;
-			public uint TimeDateStamp;
-			public uint PointerToSymbolTable;
-			public uint NumberOfSymbols;
-			public ushort SizeOfOptionalHeader;
-			public ushort Characteristics;
-#pragma warning restore CS0649
-		};
+		private const Int32 DosHeaderPeOffsetPosition = 0x3c;
+		private const UInt32 PeSignature = 0x00004550;
+		private const Int32 CoffTimeDateStampPosition = 8;
+
+		// --- Build Information ---
+
+		/// <summary>
+		/// Gets the UTC date and time represented by the assembly's PE/COFF timestamp.
+		/// </summary>
+		/// <remarks>
+		/// Deterministic builds may not store the physical build time in this field.
+		/// Use <see cref="TryGetBuildDateTime(Assembly, out DateTime)"/> when the caller
+		/// needs to distinguish an unavailable timestamp from <see cref="DateTime.MinValue"/>.
+		/// </remarks>
 
 		public static DateTime GetBuildDateTime(this Assembly assembly)
 		{
-			var path = assembly.Location;
-			if (File.Exists(path))
-			{
-				var buffer = new byte[Math.Max(Marshal.SizeOf(typeof(_IMAGE_FILE_HEADER)), 4)];
-				using (var fileStream = new FileStream(path, FileMode.Open, FileAccess.Read))
-				{
-					fileStream.Position = 0x3C;
-					fileStream.Read(buffer, 0, 4);
-					fileStream.Position = BitConverter.ToUInt32(buffer, 0); // COFF header offset
-					fileStream.Read(buffer, 0, 4); // "PE\0\0"
-					fileStream.Read(buffer, 0, buffer.Length);
-				}
-				var pinnedBuffer = GCHandle.Alloc(buffer, GCHandleType.Pinned);
-				try
-				{
-					var coffHeader = (_IMAGE_FILE_HEADER)Marshal.PtrToStructure(pinnedBuffer.AddrOfPinnedObject(), typeof(_IMAGE_FILE_HEADER));
-					DateTime buildDate = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
-					return buildDate.AddSeconds(coffHeader.TimeDateStamp);
-					//return TimeZoneInfo.Local.ToLocalTime(new DateTime(1970, 1, 1) + new TimeSpan(coffHeader.TimeDateStamp * TimeSpan.TicksPerSecond));
-				}
-				finally
-				{
-					pinnedBuffer.Free();
-				}
-			}
-			return new DateTime();
+			return TryGetBuildDateTime(assembly, out DateTime buildDateTime)
+				? buildDateTime
+				: DateTime.MinValue;
 		}
-		#endregion
 
-		//-------------------------------------------------------------------
+		/// <summary>
+		/// Tries to get the UTC date and time represented by the assembly's PE/COFF timestamp.
+		/// </summary>
+		public static Boolean TryGetBuildDateTime(this Assembly assembly, out DateTime buildDateTime)
+		{
+			ArgumentNullException.ThrowIfNull(assembly);
+
+			if (String.IsNullOrEmpty(assembly.Location))
+			{
+				buildDateTime = DateTime.MinValue;
+				return false;
+			}
+
+			return TryGetBuildDateTime(assembly.Location, out buildDateTime);
+		}
+
+		// --- PE Header Parsing ---
+
+		internal static Boolean TryGetBuildDateTime(String assemblyPath, out DateTime buildDateTime)
+		{
+			buildDateTime = DateTime.MinValue;
+
+			try
+			{
+				using FileStream fileStream = new FileStream(assemblyPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
+				using BinaryReader reader = new BinaryReader(fileStream);
+
+				fileStream.Position = DosHeaderPeOffsetPosition;
+				UInt32 coffHeaderOffset = reader.ReadUInt32();
+				fileStream.Position = coffHeaderOffset;
+				if (reader.ReadUInt32() != PeSignature)
+				{
+					return false;
+				}
+
+				fileStream.Position = coffHeaderOffset + CoffTimeDateStampPosition;
+				UInt32 timeDateStamp = reader.ReadUInt32();
+				buildDateTime = DateTime.UnixEpoch.AddSeconds(timeDateStamp);
+				return true;
+			}
+			catch (Exception exception) when (exception is IOException
+				or UnauthorizedAccessException
+				or ArgumentException
+				or NotSupportedException)
+			{
+				return false;
+			}
+		}
+
+		// --- The End ---
 	}
-	//=======================================================================
 }