Fix E_ACCESSDENIED during download if temp is hidden

src/windows/common/wslutil.cpp

@@ -369,14 +369,45 @@ std::wstring wsl::windows::common::wslutil::DownloadFileImpl(
         Filename = Url.substr(lastSlash + 1);
     }
 
-    const auto downloadFolder =
-        winrt::Windows::Storage::StorageFolder::GetFolderFromPathAsync(std::filesystem::temp_directory_path().wstring()).get();
-
-    const auto file =
-        downloadFolder.CreateFileAsync(Filename, winrt::Windows::Storage::CreationCollisionOption::GenerateUniqueName).get();
-    auto deleteFileOnFailure = wil::scope_exit_log(WI_DIAGNOSTICS_INFO, [&] { file.DeleteAsync().get(); });
+    // GetFolderFromPathAsync won't work if the folder is hidden or system.
+    auto downloadFolderPath = std::filesystem::temp_directory_path();
+    auto filenameStem = std::filesystem::path(Filename).stem().wstring();
+    auto filenameExtension = std::filesystem::path(Filename).extension().wstring();
+    std::wstring filePath{};
+    winrt::Windows::Storage::Streams::IRandomAccessStream outputStream{};
+    for (int suffix = 1; outputStream == nullptr; suffix++)
+    {
+        if (suffix == 1)
+        {
+            filePath = (downloadFolderPath / Filename).wstring();
+        }
+        else
+        {
+            filePath = (downloadFolderPath / std::format(L"{} ({}){}", filenameStem, suffix, filenameExtension)).wstring();
+        }
+        try
+        {
+            outputStream = winrt::Windows::Storage::Streams::FileRandomAccessStream::OpenAsync(
+                               filePath,
+                               winrt::Windows::Storage::FileAccessMode::ReadWrite,
+                               winrt::Windows::Storage::StorageOpenOptions::None,
+                               winrt::Windows::Storage::Streams::FileOpenDisposition::CreateNew)
+                               .get();
+        }
+        catch (...)
+        {
+            if (wil::ResultFromCaughtException() != HRESULT_FROM_WIN32(ERROR_ALREADY_EXISTS))
+            {
+                throw;
+            }
+        }
+    }
 
-    const auto outputStream = file.OpenAsync(winrt::Windows::Storage::FileAccessMode::ReadWrite).get().GetOutputStreamAt(0);
+    auto deleteFileOnFailure = wil::scope_exit_log(WI_DIAGNOSTICS_INFO, [&] {
+        outputStream.Close();
+        std::error_code ec;
+        std::filesystem::remove(filePath, ec);
+    });
 
     // By default downloaded files are cached in %appdata%/local/packages/{package-family}/AC/InetCache .
     // Disable caching since there's no reason to keep local copies of .msixbundle files.
@@ -410,7 +441,7 @@ std::wstring wsl::windows::common::wslutil::DownloadFileImpl(
     download.get();
     deleteFileOnFailure.release();
 
-    return file.Path().c_str();
+    return filePath;
 }
 
 [[nodiscard]] HANDLE wsl::windows::common::wslutil::DuplicateHandle(_In_ HANDLE Handle, _In_ std::optional<DWORD> DesiredAccess, _In_ BOOL InheritHandle)

test/windows/UnitTests.cpp

@@ -7448,5 +7448,70 @@ Error code: Wsl/InstallDistro/WSL_E_INVALID_JSON\r\n",
         }
     }
 
+    TEST_METHOD(DownloadToHiddenSystemTempFolder)
+    {
+        // Avoid contaminating the real temp folder.
+        const auto testTempFolder = std::filesystem::temp_directory_path() / L"wsl-download-test";
+        std::filesystem::create_directories(testTempFolder);
+        auto cleanupTempFolder = wil::scope_exit_log(WI_DIAGNOSTICS_INFO, [&] {
+            std::error_code error;
+            std::filesystem::remove_all(testTempFolder, error);
+        });
+
+        const auto originalAttributes = GetFileAttributesW(testTempFolder.c_str());
+        VERIFY_IS_TRUE(originalAttributes != INVALID_FILE_ATTRIBUTES);
+        VERIFY_IS_TRUE(SetFileAttributesW(testTempFolder.c_str(), originalAttributes | FILE_ATTRIBUTE_HIDDEN | FILE_ATTRIBUTE_SYSTEM));
+
+        ScopedEnvVariable temp(L"TEMP", testTempFolder.wstring());
+        ScopedEnvVariable tmp(L"TMP", testTempFolder.wstring());
+
+        VERIFY_IS_TRUE(std::filesystem::equivalent(std::filesystem::temp_directory_path(), testTempFolder));
+
+        constexpr USHORT port = 6666;
+        const auto endpoint = std::format(L"http://127.0.0.1:{}/", port);
+        constexpr auto fileName = L"downloaded-file.bin";
+        constexpr auto fileContent = L"wsl download test content";
+        UniqueWebServer server(endpoint.c_str(), fileContent);
+
+        const auto url = endpoint + fileName;
+        const auto noProgress = [](uint64_t, uint64_t) {};
+
+        wsl::shared::retry::RetryWithTimeout<void>(
+            [&]() {
+                wil::unique_socket probe{socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)};
+                THROW_LAST_ERROR_IF(!probe);
+
+                sockaddr_in address{};
+                address.sin_family = AF_INET;
+                address.sin_port = htons(port);
+                address.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+
+                THROW_LAST_ERROR_IF(connect(probe.get(), reinterpret_cast<const sockaddr*>(&address), sizeof(address)) == SOCKET_ERROR);
+            },
+            std::chrono::milliseconds(500),
+            std::chrono::seconds(5));
+
+        const auto firstPath = wsl::windows::common::wslutil::DownloadFileImpl(url, L"", noProgress);
+
+        auto readFile = [](const std::filesystem::path& Path) {
+            std::ifstream file(Path, std::ios::binary);
+            VERIFY_IS_TRUE(file.good());
+            return std::string{std::istreambuf_iterator<char>(file), {}};
+        };
+
+        VERIFY_ARE_EQUAL(std::filesystem::path(firstPath).parent_path(), testTempFolder);
+        VERIFY_ARE_EQUAL(std::filesystem::path(firstPath).filename().wstring(), std::wstring(fileName));
+        VERIFY_IS_TRUE(std::filesystem::exists(firstPath));
+        VERIFY_ARE_EQUAL(readFile(firstPath), wsl::shared::string::WideToMultiByte(fileContent));
+
+        const auto secondPath = wsl::windows::common::wslutil::DownloadFileImpl(url, L"", noProgress);
+
+        VERIFY_ARE_EQUAL(std::filesystem::path(secondPath).parent_path(), testTempFolder);
+        VERIFY_ARE_EQUAL(std::filesystem::path(secondPath).filename().wstring(), std::wstring(L"downloaded-file (2).bin"));
+        VERIFY_IS_TRUE(std::filesystem::exists(firstPath));
+        VERIFY_IS_TRUE(std::filesystem::exists(secondPath));
+        VERIFY_ARE_EQUAL(readFile(secondPath), wsl::shared::string::WideToMultiByte(fileContent));
+    }
+
 }; // namespace UnitTests
 } // namespace UnitTests