Verify Google Lens OCR downloads before unpack

src/ui/Logic/Download/GoogleLensOcrDownloadService.cs

@@ -4,6 +4,7 @@
 using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
+using Nikse.SubtitleEdit.UiLogic;
 
 namespace Nikse.SubtitleEdit.Logic.Download;
 
@@ -18,35 +19,121 @@ public class GoogleLensOcrDownloadService(HttpClient httpClient) : IGoogleLensOc
 {
     //private const string WindowsUrl = "https://github.com/timminator/chrome-lens-py/releases/download/v3.3.0/Chrome-Lens-CLI-v3.3.0.7z";
     private const string WindowsUrl = "https://github.com/timminator/Chrome-Lens-OCR/releases/download/v3.4.0/Chrome-Lens-OCR-v3.4.0.7z";
+    private const string WindowsSha256 = "201685c3a3857515360174ab1e470c0f6d1e35fd90ece76deb74c277d17df085";
     private const string LinuxUrl = "https://github.com/timminator/Chrome-Lens-OCR/releases/download/v3.4.0/Chrome-Lens-OCR-v3.4.0-Linux.7z";
+    private const string LinuxSha256 = "661348e20c12e4e43df061189bb90c46eff07ec25835532c52f6dcb1ce9d6d42";
+
+    internal readonly record struct DownloadInfo(string Url, string Sha256);
 
     public async Task DownloadGoogleLensOcrStandalone(string destinationFileName, IProgress<float>? progress, CancellationToken cancellationToken)
     {
-        await DownloadHelper.DownloadFileAsync(httpClient, GetUrl(), destinationFileName, progress, cancellationToken);
+        await DownloadAndVerifyFileAsync(httpClient, GetDownload(), destinationFileName, progress, cancellationToken);
     }
 
     public async Task DownloadGoogleLensOcrStandalone(Stream stream, IProgress<float>? progress, CancellationToken cancellationToken)
     {
-        await DownloadHelper.DownloadFileAsync(httpClient, GetUrl(), stream, progress, cancellationToken);
+        var download = GetDownload();
+        await DownloadHelper.DownloadFileAsync(httpClient, download.Url, stream, progress, cancellationToken);
+        await VerifyStreamAsync(stream, download.Sha256, cancellationToken);
     }
 
-    private string GetUrl()
+    internal static async Task DownloadAndVerifyFileAsync(
+        HttpClient client,
+        DownloadInfo download,
+        string destinationFileName,
+        IProgress<float>? progress,
+        CancellationToken cancellationToken)
     {
-        if (OperatingSystem.IsWindows())
+        try
         {
-            return WindowsUrl;
-        }
+            await DownloadHelper.DownloadFileAsync(
+                client,
+                download.Url,
+                destinationFileName,
+                progress,
+                cancellationToken);
 
-        if (OperatingSystem.IsLinux())
+            await using var stream = File.OpenRead(destinationFileName);
+            var actual = await Sha256Util.ComputeSha256Async(stream, cancellationToken);
+            if (!string.Equals(download.Sha256, actual, StringComparison.OrdinalIgnoreCase))
+            {
+                throw new IOException(
+                    $"Google Lens OCR download failed integrity check (expected SHA-256 {download.Sha256}, got {actual}).");
+            }
+        }
+        catch
         {
-            if (RuntimeInformation.ProcessArchitecture == Architecture.Arm64)
+            try
+            {
+                if (File.Exists(destinationFileName))
+                {
+                    File.Delete(destinationFileName);
+                }
+            }
+            catch
             {
-                throw new PlatformNotSupportedException("Google Lens OCR is not available for Linux ARM64.");
+                // Preserve the original download/integrity error; cleanup is best-effort.
             }
 
-            return LinuxUrl;
+            throw;
+        }
+    }
+
+    internal static async Task VerifyStreamAsync(
+        Stream stream,
+        string expectedSha256,
+        CancellationToken cancellationToken)
+    {
+        if (!stream.CanRead || !stream.CanSeek)
+        {
+            throw new InvalidOperationException("Google Lens OCR integrity verification requires a readable, seekable stream.");
+        }
+
+        string actual;
+        stream.Position = 0;
+        try
+        {
+            actual = await Sha256Util.ComputeSha256Async(stream, cancellationToken);
+        }
+        finally
+        {
+            stream.Position = 0;
+        }
+
+        if (!string.Equals(expectedSha256, actual, StringComparison.OrdinalIgnoreCase))
+        {
+            throw new IOException(
+                $"Google Lens OCR download failed integrity check (expected SHA-256 {expectedSha256}, got {actual}).");
+        }
+    }
+
+    private static DownloadInfo GetDownload()
+    {
+        if (OperatingSystem.IsWindows())
+        {
+            return ResolveWindowsDownload();
+        }
+
+        if (OperatingSystem.IsLinux())
+        {
+            return ResolveLinuxDownload(RuntimeInformation.ProcessArchitecture);
         }
 
         throw new PlatformNotSupportedException("Google Lens OCR does not support this platform");
     }
+
+    internal static DownloadInfo ResolveWindowsDownload()
+    {
+        return new DownloadInfo(WindowsUrl, WindowsSha256);
+    }
+
+    internal static DownloadInfo ResolveLinuxDownload(Architecture architecture)
+    {
+        if (architecture == Architecture.Arm64)
+        {
+            throw new PlatformNotSupportedException("Google Lens OCR is not available for Linux ARM64.");
+        }
+
+        return new DownloadInfo(LinuxUrl, LinuxSha256);
+    }
 }

tests/UI/Logic/Download/GoogleLensOcrDownloadServiceTests.cs

@@ -0,0 +1,89 @@
+using System.Net;
+using System.Runtime.InteropServices;
+using System.Security.Cryptography;
+using System.Text;
+using Nikse.SubtitleEdit.Logic.Download;
+
+namespace UITests.Logic.Download;
+
+public class GoogleLensOcrDownloadServiceTests
+{
+    [Fact]
+    public void ResolveWindowsDownload_PinsOfficialArchiveDigest()
+    {
+        var download = GoogleLensOcrDownloadService.ResolveWindowsDownload();
+
+        Assert.Equal(
+            "https://github.com/timminator/Chrome-Lens-OCR/releases/download/v3.4.0/Chrome-Lens-OCR-v3.4.0.7z",
+            download.Url);
+        Assert.Equal("201685c3a3857515360174ab1e470c0f6d1e35fd90ece76deb74c277d17df085", download.Sha256);
+    }
+
+    [Fact]
+    public void ResolveLinuxDownload_X64_PinsOfficialArchiveDigest()
+    {
+        var download = GoogleLensOcrDownloadService.ResolveLinuxDownload(Architecture.X64);
+
+        Assert.Equal(
+            "https://github.com/timminator/Chrome-Lens-OCR/releases/download/v3.4.0/Chrome-Lens-OCR-v3.4.0-Linux.7z",
+            download.Url);
+        Assert.Equal("661348e20c12e4e43df061189bb90c46eff07ec25835532c52f6dcb1ce9d6d42", download.Sha256);
+    }
+
+    [Fact]
+    public void ResolveLinuxDownload_Arm64_RemainsUnsupported()
+    {
+        Assert.Throws<PlatformNotSupportedException>(() =>
+            GoogleLensOcrDownloadService.ResolveLinuxDownload(Architecture.Arm64));
+    }
+
+    [Fact]
+    public async Task DownloadAndVerifyFileAsync_TamperedPayload_RejectsAndDeletesFile()
+    {
+        var expectedPayload = Encoding.ASCII.GetBytes("expected");
+        var expected = Convert.ToHexString(SHA256.HashData(expectedPayload)).ToLowerInvariant();
+        var download = new GoogleLensOcrDownloadService.DownloadInfo("https://example.test/google-lens.7z", expected);
+        var fileName = Path.Combine(Path.GetTempPath(), Guid.NewGuid() + ".7z");
+
+        using var httpClient = new HttpClient(new StaticResponseHandler(Encoding.ASCII.GetBytes("tampered")));
+
+        await Assert.ThrowsAsync<IOException>(() =>
+            GoogleLensOcrDownloadService.DownloadAndVerifyFileAsync(
+                httpClient,
+                download,
+                fileName,
+                progress: null,
+                TestContext.Current.CancellationToken));
+
+        Assert.False(File.Exists(fileName));
+    }
+
+    [Fact]
+    public async Task VerifyStreamAsync_TamperedPayload_RewindsStream()
+    {
+        var expectedPayload = Encoding.ASCII.GetBytes("expected");
+        var expected = Convert.ToHexString(SHA256.HashData(expectedPayload)).ToLowerInvariant();
+        await using var stream = new MemoryStream(Encoding.ASCII.GetBytes("tampered"));
+
+        await Assert.ThrowsAsync<IOException>(() =>
+            GoogleLensOcrDownloadService.VerifyStreamAsync(
+                stream,
+                expected,
+                TestContext.Current.CancellationToken));
+
+        Assert.Equal(0, stream.Position);
+    }
+
+    private sealed class StaticResponseHandler(byte[] payload) : HttpMessageHandler
+    {
+        protected override Task<HttpResponseMessage> SendAsync(
+            HttpRequestMessage request,
+            CancellationToken cancellationToken)
+        {
+            return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+            {
+                Content = new ByteArrayContent(payload),
+            });
+        }
+    }
+}