Fix URL-safe encoding of uploaded filenames

Replace the fragment marker used for unsupported filename characters with an underscore and cover upload metadata and static-file downloads.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/Yavsc.Abstract/FileSystem/AbstractFileSystemHelpers.cs

@@ -49,6 +49,7 @@ namespace Yavsc.Server.Helpers
         // Ensure this path is canonical,
         // No "dirto/./this", neither "dirt/to/that/"
         // no .. and each char must be listed as valid in constants
+        // Encode unsupported chars with '_' rather than the URL fragment marker '#'.
         public static string FilterFileName(string fileName)
         {
             if (fileName==null) return null;
@@ -57,7 +58,7 @@ namespace Yavsc.Server.Helpers
             {
                 if (ValidFileNameChars.Contains(c))
                     sb.Append(c);
-                else sb.Append("#" + ((int)c).ToString("D3"));
+                else sb.Append("_" + ((int)c).ToString("D3"));
             }
             return sb.ToString();
         }

src/test/Yavsc.Blogs.Tests/FileSystemApiTests.cs

@@ -91,8 +91,12 @@ public sealed class FileSystemApiTests : IClassFixture<BlogsWebServerFixture>
         return file.Id;
     }
 
-    [Fact]
-    public async Task Post_fs_creates_an_UploadedFile_row_owned_by_the_caller()
+    [Theory]
+    [InlineData("note.txt", "note.txt")]
+    [InlineData("INSC_E03686381_SCHNEIDER_000113378AA__Troisi\u00e8me__.PDF",
+        "INSC_E03686381_SCHNEIDER_000113378AA__Troisi_232me__.PDF")]
+    public async Task Post_fs_creates_an_UploadedFile_row_owned_by_the_caller(
+        string originalName, string storedName)
     {
         _fixture.ResetDatabase();
         // DiskQuota must be non-zero: ReceiveUserFile flags QuotaOffense
@@ -105,7 +109,7 @@ public sealed class FileSystemApiTests : IClassFixture<BlogsWebServerFixture>
         using var form = new MultipartFormDataContent();
         var fileContent = new ByteArrayContent(payload);
         fileContent.Headers.ContentType = new MediaTypeHeaderValue("text/plain");
-        form.Add(fileContent, "file", "note.txt");
+        form.Add(fileContent, "file", originalName);
 
         using var http = NewClient("alice");
         var response = await http.PostAsync("/api/v1/fs", form, TestContext.Current.CancellationToken);
@@ -117,18 +121,17 @@ public sealed class FileSystemApiTests : IClassFixture<BlogsWebServerFixture>
         var item = Assert.Single(doc.RootElement.EnumerateArray());
         var fileId = item.GetProperty("fileId").GetInt64();
         Assert.True(fileId > 0, $"Expected a positive fileId, got {fileId}. Body: {body}");
-        Assert.Equal("note.txt", item.GetProperty("fileName").GetString());
+        Assert.Equal(storedName, item.GetProperty("fileName").GetString());
         Assert.False(item.GetProperty("quotaOffense").GetBoolean());
 
         using var scope = _fixture.Services.CreateScope();
         var db = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
         var row = Assert.Single(db.UploadedFiles.Where(u => u.OwnerId == "alice"));
-        Assert.Equal("note.txt", row.Path);
+        Assert.Equal(storedName, row.Path);
         Assert.Equal("text/plain", row.ContentType);
         Assert.Equal(payload.Length, row.Length);
 
-        // The file physically landed under {BlogFilesRoot}/alice/note.txt.
-        Assert.True(File.Exists(PhysicalFile(_fixture, "alice", "note.txt")),
+        Assert.True(File.Exists(PhysicalFile(_fixture, "alice", storedName)),
             "Expected the uploaded file on disk under the owner's personal root");
     }
 

src/test/Yavsc.Blogs.Tests/FilterFileNameTests.cs

@@ -0,0 +1,76 @@
+using System.Net;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.FileProviders;
+using Yavsc.Models;
+using Yavsc.Server.Helpers;
+
+namespace Yavsc.Blogs.Tests;
+
+public sealed class FilterFileNameTests
+{
+    [Theory]
+    [InlineData("note.txt", "note.txt")]
+    [InlineData("ABC-123=_~.PDF", "ABC-123=_~.PDF")]
+    [InlineData("Troisi\u00e8me.PDF", "Troisi_232me.PDF")]
+    [InlineData("\u00e9\u00e0\u00e7.pdf", "_233_224_231.pdf")]
+    [InlineData("folder/file\\name.pdf", "folder_047file_092name.pdf")]
+    public void Filter_encodes_unsupported_characters_without_URL_fragments(
+        string originalName, string expectedName)
+    {
+        var filtered = AbstractFileSystemHelpers.FilterFileName(originalName);
+
+        Assert.Equal(expectedName, filtered);
+        Assert.DoesNotContain("#", filtered);
+        Assert.True(filtered.IsValidYavscPath());
+        Assert.Equal(filtered, AbstractFileSystemHelpers.FilterFileName(filtered));
+    }
+
+    [Fact]
+    public async Task Uploaded_accented_filename_is_accessible_through_static_files()
+    {
+        var root = Path.Combine(Path.GetTempPath(), $"yavsc-filename-{Guid.NewGuid():N}");
+        Directory.CreateDirectory(root);
+        try
+        {
+            var payload = System.Text.Encoding.UTF8.GetBytes("accented filename regression");
+            using var input = new MemoryStream(payload);
+            var file = new FormFile(input, 0, payload.Length, "file",
+                "INSC_E03686381_SCHNEIDER_000113378AA__Troisi\u00e8me__.PDF")
+            {
+                Headers = new HeaderDictionary(),
+                ContentType = "application/pdf"
+            };
+            var user = new ApplicationUser { DiskQuota = 10_000_000 };
+            var received = user.ReceiveUserFile(root, file);
+            Assert.False(received.QuotaOffense);
+            Assert.Equal("INSC_E03686381_SCHNEIDER_000113378AA__Troisi_232me__.PDF",
+                received.FileName);
+
+            using var provider = new PhysicalFileProvider(root);
+            var builder = WebApplication.CreateBuilder();
+            builder.WebHost.UseTestServer();
+            await using var app = builder.Build();
+            app.UseStaticFiles(new StaticFileOptions
+            {
+                FileProvider = provider,
+                RequestPath = "/files"
+            });
+            await app.StartAsync(TestContext.Current.CancellationToken);
+            using var http = app.GetTestClient();
+            var uri = new Uri(http.BaseAddress!, $"/files/{received.FileName}");
+            Assert.Equal(string.Empty, uri.Fragment);
+            using var response = await http.GetAsync(uri, TestContext.Current.CancellationToken);
+
+            Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+            Assert.Equal("application/pdf", response.Content.Headers.ContentType?.MediaType);
+            Assert.Equal(payload,
+                await response.Content.ReadAsByteArrayAsync(TestContext.Current.CancellationToken));
+        }
+        finally
+        {
+            Directory.Delete(root, recursive: true);
+        }
+    }
+}