fix(asar): correct archive tree lookups and fail loudly on unreadable input

InsertFile resolved the grandparent node instead of the parent.
Reads no longer create phantom directories in the header.
Bound symlink traversal and skip reparse points when crawling.
Locked or unreadable files now abort packing instead of being dropped.
Read headers and integrity blocks with a full-read loop.
Assert the header keeps its size before overwriting the placeholder.
Validate Pickle buffer sizes, payload overflow and negative lengths.
Check CreateSymbolicLink and external tool exit codes.
Drop unused Pickle accessors, TransformedFile and FilesystemFilesAndLinks.Links.

AsarSharp/Utils/Extensions.cs

@@ -5,8 +5,30 @@ using System.Text;
 
 namespace AsarSharp.Utils
 {
-    internal static class Extensions
+    public static class Extensions
     {
+        /// <summary>
+        /// Fills <paramref name="count"/> bytes. Stream.Read may legally return fewer than
+        /// asked for; treating a short read as EOF corrupts header parsing and block hashes.
+        /// Returns the bytes actually read, which is less than count only at end of stream.
+        /// </summary>
+        public static int ReadFull(this Stream stream, byte[] buffer, int offset, int count)
+        {
+            int total = 0;
+            while (total < count)
+            {
+                int read = stream.Read(buffer, offset + total, count - total);
+                if (read <= 0)
+                {
+                    break;
+                }
+
+                total += read;
+            }
+
+            return total;
+        }
+
         /// <summary>
         /// Compute path relative to <paramref name="relativeTo"/>.
         /// Fast common-case (path is inside relativeTo): plain prefix-strip.
@@ -170,19 +192,7 @@ namespace AsarSharp.Utils
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
                 return;
 
-            var process = new System.Diagnostics.Process
-            {
-                StartInfo = new System.Diagnostics.ProcessStartInfo
-                {
-                    FileName = "chmod",
-                    Arguments = $"{permission} \"{filePath}\"",
-                    UseShellExecute = false,
-                    RedirectStandardOutput = true,
-                    CreateNoWindow = true
-                }
-            };
-            process.Start();
-            process.WaitForExit();
+            RunTool("chmod", $"{permission} \"{filePath}\"");
         }
 
 
@@ -190,32 +200,41 @@ namespace AsarSharp.Utils
         {
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
             {
-                NativeMethods.CreateSymbolicLink(linkPath, linkTarget,
+                bool success = NativeMethods.CreateSymbolicLink(linkPath, linkTarget,
                     Directory.Exists(linkTarget)
                         ? NativeMethods.SymLinkFlag.Directory
                         : NativeMethods.SymLinkFlag.File);
+                if (!success)
+                    throw new System.ComponentModel.Win32Exception(Marshal.GetLastWin32Error());
                 return;
             }
 
-            var process = new System.Diagnostics.Process
-            {
-                StartInfo = new System.Diagnostics.ProcessStartInfo
-                {
-                    FileName = "ln",
-                    Arguments = $"-s \"{linkTarget}\" \"{linkPath}\"",
-                    UseShellExecute = false,
-                    RedirectStandardOutput = true,
-                    CreateNoWindow = true
-                }
-            };
-            process.Start();
-            process.WaitForExit();
+            RunTool("ln", $"-s \"{linkTarget}\" \"{linkPath}\"");
         }
 
-
         public static bool IsWindowsPlatform()
         {
-            return Environment.OSVersion.Platform == PlatformID.Win32NT;
+            return RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
+        }
+
+        private static void RunTool(string fileName, string arguments)
+        {
+            using (var process = new System.Diagnostics.Process
+                   {
+                       StartInfo = new System.Diagnostics.ProcessStartInfo
+                       {
+                           FileName = fileName,
+                           Arguments = arguments,
+                           UseShellExecute = false,
+                           CreateNoWindow = true
+                       }
+                   })
+            {
+                process.Start();
+                process.WaitForExit();
+                if (process.ExitCode != 0)
+                    throw new InvalidOperationException($"Tool {fileName} failed with exit code {process.ExitCode}.");
+            }
         }
     }
 }