From 319c003b7b71cc232683b3048c4622ef528fa11e Mon Sep 17 00:00:00 2001
From: Jeremy Powell <jeremy@visionaid.com>
Date: Fri, 6 Dec 2024 11:41:13 +1300
Subject: [PATCH] Limit V3 compund files to 2 GB

---
 OpenMcdf.Tests/OpenMcdf.Tests.csproj |  1 +
 OpenMcdf.Tests/RootStorageTests.cs   | 23 ++++++++++++++++++++++-
 OpenMcdf/RootContext.cs              |  5 +++++
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/OpenMcdf.Tests/OpenMcdf.Tests.csproj b/OpenMcdf.Tests/OpenMcdf.Tests.csproj
index 648240d..105120a 100644
--- a/OpenMcdf.Tests/OpenMcdf.Tests.csproj
+++ b/OpenMcdf.Tests/OpenMcdf.Tests.csproj
@@ -20,6 +20,7 @@
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
+    <PackageReference Include="Microsoft.IO.RecyclableMemoryStream" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" />
     <PackageReference Include="MSTest" />
   </ItemGroup>
diff --git a/OpenMcdf.Tests/RootStorageTests.cs b/OpenMcdf.Tests/RootStorageTests.cs
index 521eca8..f6350ed 100644
--- a/OpenMcdf.Tests/RootStorageTests.cs
+++ b/OpenMcdf.Tests/RootStorageTests.cs
@@ -1,4 +1,6 @@
-namespace OpenMcdf.Tests;
+using Microsoft.IO;
+
+namespace OpenMcdf.Tests;
 
 [TestClass]
 public sealed class RootStorageTests
@@ -231,4 +233,23 @@ public void DeleteTrimsBaseStream(bool consolidate)
 
         Assert.IsTrue(originalLength > newLength);
     }
+
+    [TestMethod]
+    [DoNotParallelize] // High memory usage
+    public void V3ThrowsIOExceptionAt2GB()
+    {
+        const long MaxStreamLength = 2L * 1024 * 1024 * 1024;
+
+        RecyclableMemoryStreamManager manager = new();
+        using RecyclableMemoryStream baseStream = new(manager);
+        baseStream.Capacity64 = MaxStreamLength;
+
+        using var rootStorage = RootStorage.Create(baseStream, Version.V3);
+        using CfbStream stream = rootStorage.CreateStream("Test");
+        byte[] buffer = TestData.CreateByteArray(1024 * 1024);
+        while (baseStream.Length + buffer.Length <= MaxStreamLength)
+            stream.Write(buffer, 0, buffer.Length);
+
+        Assert.ThrowsException<IOException>(() => stream.Write(buffer, 0, buffer.Length));
+    }
 }
diff --git a/OpenMcdf/RootContext.cs b/OpenMcdf/RootContext.cs
index b066534..0898897 100644
--- a/OpenMcdf/RootContext.cs
+++ b/OpenMcdf/RootContext.cs
@@ -16,6 +16,8 @@ enum IOContextFlags
 /// </summary>
 internal sealed class RootContext : ContextBase, IDisposable
 {
+    const long MaximumV3StreamLength = 2147483648;
+
     readonly IOContextFlags contextFlags;
     readonly CfbBinaryWriter? writer;
     readonly TransactedStream? transactedStream;
@@ -185,6 +187,9 @@ public void Flush()
 
     public void ExtendStreamLength(long length)
     {
+        if (Version is Version.V3 && length > MaximumV3StreamLength)
+            throw new IOException("V3 compound files are limited to 2 GB.");
+
         if (Length < length)
             Length = length;
     }