LibWeb: Add a basic content filter (ad blocking!) :^)

This patch adds a global (per-process) filter list to LibWeb that is
used to filter all outgoing resource load requests.

Basically we check the URL against a list of filter patterns and if
it's a match for any one of them, we immediately fail the load.

The filter list is a simple text file:

    ~/.config/BrowserContentFilters.txt

It's one filter per line and they are simple glob filters for now,
with implicit asterisks (*) at the start and end of the line.

Applications/Browser/main.cpp

@@ -43,6 +43,7 @@
 #include <LibGUI/TabWidget.h>
 #include <LibGUI/Window.h>
 #include <LibGfx/Bitmap.h>
+#include <LibWeb/Loader/ContentFilter.h>
 #include <LibWeb/Loader/ResourceLoader.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -132,6 +133,17 @@ int main(int argc, char** argv)
     auto m_config = Core::ConfigFile::get_for_app("Browser");
     Browser::g_home_url = m_config->read_entry("Preferences", "Home", "about:blank");
 
+    auto ad_filter_list_or_error = Core::File::open(String::formatted("{}/BrowserContentFilters.txt", Core::StandardPaths::config_directory()), Core::IODevice::ReadOnly);
+    if (!ad_filter_list_or_error.is_error()) {
+        auto& ad_filter_list = *ad_filter_list_or_error.value();
+        while (!ad_filter_list.eof()) {
+            auto line = ad_filter_list.read_line();
+            if (line.is_empty())
+                continue;
+            Web::ContentFilter::the().add_pattern(line);
+        }
+    }
+
     bool bookmarksbar_enabled = true;
     auto bookmarks_bar = Browser::BookmarksBarWidget::construct(Browser::bookmarks_file_path(), bookmarksbar_enabled);
 

Libraries/LibWeb/CMakeLists.txt

@@ -177,6 +177,7 @@ set(SOURCES
     Layout/TreeBuilder.cpp
     Layout/WidgetBox.cpp
     LayoutTreeModel.cpp
+    Loader/ContentFilter.cpp
     Loader/FrameLoader.cpp
     Loader/ImageLoader.cpp
     Loader/ImageResource.cpp

Libraries/LibWeb/Loader/ContentFilter.cpp

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/StringBuilder.h>
+#include <LibWeb/Loader/ContentFilter.h>
+
+namespace Web {
+
+ContentFilter& ContentFilter::the()
+{
+    static ContentFilter* filter = new ContentFilter;
+    return *filter;
+}
+
+ContentFilter::ContentFilter()
+{
+}
+
+ContentFilter::~ContentFilter()
+{
+}
+
+bool ContentFilter::is_filtered(const URL& url) const
+{
+    auto url_string = url.to_string();
+
+    for (auto& pattern : m_patterns) {
+        if (url_string.matches(pattern.text, CaseSensitivity::CaseSensitive))
+            return true;
+    }
+    return false;
+}
+
+void ContentFilter::add_pattern(const String& pattern)
+{
+    StringBuilder builder;
+    if (!pattern.starts_with('*'))
+        builder.append('*');
+    builder.append(pattern);
+    if (!pattern.ends_with('*'))
+        builder.append('*');
+    m_patterns.empend(builder.to_string());
+}
+
+}

Libraries/LibWeb/Loader/ContentFilter.h

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/URL.h>
+#include <AK/Vector.h>
+
+namespace Web {
+
+class ContentFilter {
+public:
+    static ContentFilter& the();
+
+    bool is_filtered(const URL&) const;
+    void add_pattern(const String&);
+
+private:
+    ContentFilter();
+    ~ContentFilter();
+
+    struct Pattern {
+        String text;
+    };
+    Vector<Pattern> m_patterns;
+};
+
+}

Libraries/LibWeb/Loader/ResourceLoader.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,6 +31,7 @@
 #include <LibCore/File.h>
 #include <LibProtocol/Client.h>
 #include <LibProtocol/Download.h>
+#include <LibWeb/Loader/ContentFilter.h>
 #include <LibWeb/Loader/LoadRequest.h>
 #include <LibWeb/Loader/Resource.h>
 #include <LibWeb/Loader/ResourceLoader.h>
@@ -110,11 +111,18 @@ RefPtr<Resource> ResourceLoader::load_resource(Resource::Type type, const LoadRe
 void ResourceLoader::load(const LoadRequest& request, Function<void(ReadonlyBytes, const HashMap<String, String, CaseInsensitiveStringTraits>& response_headers)> success_callback, Function<void(const String&)> error_callback)
 {
     auto& url = request.url();
+
     if (is_port_blocked(url.port())) {
         dbg() << "ResourceLoader::load: Error: blocked port " << url.port() << " for URL: " << url;
         return;
     }
 
+    if (ContentFilter::the().is_filtered(url)) {
+        dbgln("\033[32;1mResourceLoader::load: URL was filtered! {}\033[0m", url);
+        error_callback("URL was filtered");
+        return;
+    }
+
     if (url.protocol() == "about") {
         dbg() << "Loading about: URL " << url;
         deferred_invoke([success_callback = move(success_callback)](auto&) {