BUGFIX: Support reading/writing unaligned metadata directories.

Washi1337 · Feb 26, 2024 · af2e49d · af2e49d
1 parent 2bae91a
commit af2e49d
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Showing 7 changed files with 36 additions and 7 deletions.
diff --git a/src/AsmResolver.PE/DotNet/Metadata/Metadata.cs b/src/AsmResolver.PE/DotNet/Metadata/Metadata.cs
@@ -188,9 +188,11 @@ protected virtual void WriteStreamHeaders(IBinaryStreamWriter writer, MetadataSt
                 var header = headers[i];
                 writer.WriteUInt32(header.Offset);
                 writer.WriteUInt32(header.Size);
+
+                ulong nameOffset = writer.Offset;
                 writer.WriteAsciiString(header.Name);
                 writer.WriteByte(0);
-                writer.Align(4);
+                writer.AlignRelative(4, nameOffset);
             }
         }
 

diff --git a/src/AsmResolver.PE/DotNet/Metadata/MetadataStreamHeader.cs b/src/AsmResolver.PE/DotNet/Metadata/MetadataStreamHeader.cs
@@ -60,7 +60,7 @@ public static MetadataStreamHeader FromReader(ref BinaryStreamReader reader)
             uint offset = reader.ReadUInt32();
             uint size = reader.ReadUInt32();
             string name = reader.ReadAsciiString();
-            reader.Align(4);
+            reader.AlignRelative(4);
             return new MetadataStreamHeader(offset, size, name);
         }
 

diff --git a/src/AsmResolver/IO/IBinaryStreamWriter.cs b/src/AsmResolver/IO/IBinaryStreamWriter.cs
@@ -201,10 +201,18 @@ public static void WriteAsciiString(this IBinaryStreamWriter writer, string valu
         /// </summary>
         /// <param name="writer">The writer to align.</param>
         /// <param name="align">The boundary to use.</param>
-        public static void Align(this IBinaryStreamWriter writer, uint align)
+        public static void Align(this IBinaryStreamWriter writer, uint align) => writer.AlignRelative(align, 0);
+
+        /// <summary>
+        /// Aligns the writer to a specified boundary, relative to the provided start offset..
+        /// </summary>
+        /// <param name="writer">The writer to align.</param>
+        /// <param name="align">The boundary to use.</param>
+        /// <param name="startOffset">The starting offset to consider the alignment boundaries from.</param>
+        public static void AlignRelative(this IBinaryStreamWriter writer, uint align, ulong startOffset)
         {
-            ulong currentPosition = writer.Offset;
-            writer.WriteZeroes((int) (currentPosition.Align(align) - writer.Offset));
+            ulong currentPosition = writer.Offset - startOffset;
+            writer.WriteZeroes((int) (currentPosition.Align(align) - currentPosition));
         }
 
         /// <summary>

diff --git a/test/AsmResolver.PE.Tests/DotNet/Metadata/MetadataTest.cs b/test/AsmResolver.PE.Tests/DotNet/Metadata/MetadataTest.cs
@@ -34,7 +34,17 @@ public void CorrectStreamHeaders()
             var peImage = PEImage.FromBytes(Properties.Resources.HelloWorld);
             var metadata = peImage.DotNetDirectory!.Metadata!;
 
-            var expectedNames = new[] {"#~", "#Strings", "#US", "#GUID", "#Blob"};
+            string[] expectedNames = new[] {"#~", "#Strings", "#US", "#GUID", "#Blob"};
+            Assert.Equal(expectedNames, metadata.Streams.Select(s => s.Name));
+        }
+
+        [Fact]
+        public void CorrectStreamHeadersUnalignedMetadataDirectory()
+        {
+            var peImage = PEImage.FromBytes(Properties.Resources.HelloWorld_UnalignedMetadata);
+            var metadata = peImage.DotNetDirectory!.Metadata!;
+
+            string[] expectedNames = new[] {"#~", "#Strings", "#US", "#GUID", "#Blob"};
             Assert.Equal(expectedNames, metadata.Streams.Select(s => s.Name));
         }
 
@@ -188,6 +198,5 @@ public void SelectFirstUserStringsStreamInEnCMetadata()
         {
             AssertCorrectStreamIsSelected<UserStringsStream>(Properties.Resources.HelloWorld_DoubleUserStringsStream_EnC, true);
         }
-
     }
 }
diff --git a/test/AsmResolver.PE.Tests/Properties/Resources.Designer.cs b/test/AsmResolver.PE.Tests/Properties/Resources.Designer.cs
diff --git a/test/AsmResolver.PE.Tests/Properties/Resources.resx b/test/AsmResolver.PE.Tests/Properties/Resources.resx
@@ -72,6 +72,9 @@
     <data name="HelloWorld_ReadyToRun" type="System.Resources.ResXFileRef, System.Windows.Forms">
         <value>..\Resources\HelloWorld.ReadyToRun.dll;System.Byte[], mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
     </data>
+    <data name="HelloWorld_UnalignedMetadata" type="System.Resources.ResXFileRef, System.Windows.Forms">
+        <value>..\Resources\HelloWorld.UnalignedMetadata.exe;System.Byte[], mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+    </data>
     <data name="HelloWorldPortablePdb" type="System.Resources.ResXFileRef, System.Windows.Forms">
         <value>..\Resources\HelloWorld.pdb;System.Byte[], mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
     </data>

diff --git a/test/AsmResolver.PE.Tests/Resources/HelloWorld.UnalignedMetadata.exe b/test/AsmResolver.PE.Tests/Resources/HelloWorld.UnalignedMetadata.exe