fix(printing): update print preview handling for Dao scheme and enhance CSP for cross-scheme compatibility

Author: moonrailgun

src/patches/chrome/browser/resources/pdf/pdf_internal_plugin_wrapper.ts.patch

@@ -0,0 +1,31 @@
+diff --git a/chrome/browser/resources/pdf/pdf_internal_plugin_wrapper.ts b/chrome/browser/resources/pdf/pdf_internal_plugin_wrapper.ts
+index 0f221c0532..c0c8dd2941 100644
+--- a/chrome/browser/resources/pdf/pdf_internal_plugin_wrapper.ts
++++ b/chrome/browser/resources/pdf/pdf_internal_plugin_wrapper.ts
+@@ -20,9 +20,15 @@ const plugin = document.querySelector<InProcessPdfPluginElement>('embed')!;
+ 
+ const srcUrl = new URL(plugin.src);
+ let parentOrigin = srcUrl.origin;
++const printPreviewParentOrigins = ['chrome://print', 'dao://print'];
+ if (parentOrigin === 'chrome-untrusted://print') {
+   // Within Print Preview, the source origin differs from the parent origin.
+-  parentOrigin = 'chrome://print';
++  const ancestorOrigin = window.location.ancestorOrigins.length > 0 ?
++      window.location.ancestorOrigins[0]! :
++      '';
++  parentOrigin = printPreviewParentOrigins.includes(ancestorOrigin) ?
++      ancestorOrigin :
++      'chrome://print';
+ }
+ 
+ // Plugin-to-parent message handlers. All messages are passed through, but some
+@@ -93,7 +99,8 @@ channel.port1.onmessage = e => {
+       // Snoop on "viewport" message to support real RTL scrolling in Print
+       // Preview.
+       // TODO(crbug.com/40737077): Support real RTL scrolling in the PDF viewer.
+-      if (parentOrigin === 'chrome://print' && e.data.layoutOptions) {
++      if (printPreviewParentOrigins.includes(parentOrigin) &&
++          e.data.layoutOptions) {
+         switch (e.data.layoutOptions.direction) {
+           case 1:
+             document.dir = 'rtl';

src/patches/chrome/browser/resources/pdf/pdf_scripting_api.ts.patch

@@ -0,0 +1,14 @@
+diff --git a/chrome/browser/resources/pdf/pdf_scripting_api.ts b/chrome/browser/resources/pdf/pdf_scripting_api.ts
+index 7e6a5a553d..d0f2e4f0a8 100644
+--- a/chrome/browser/resources/pdf/pdf_scripting_api.ts
++++ b/chrome/browser/resources/pdf/pdf_scripting_api.ts
+@@ -97,7 +97,8 @@ export class PdfScriptingApi {
+     window.addEventListener('message', event => {
+       if (event.origin !==
+               'chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai' &&
+-          event.origin !== 'chrome://print') {
++          event.origin !== 'chrome://print' &&
++          event.origin !== 'dao://print') {
+         console.error(
+             'Received message that was not from the extension: ' + event);
+         return;

src/patches/chrome/browser/resources/print_preview/ui/plugin_proxy.ts.patch

@@ -0,0 +1,13 @@
+diff --git a/chrome/browser/resources/print_preview/ui/plugin_proxy.ts b/chrome/browser/resources/print_preview/ui/plugin_proxy.ts
+index afbf6c857e..fcdbe21516 100644
+--- a/chrome/browser/resources/print_preview/ui/plugin_proxy.ts
++++ b/chrome/browser/resources/print_preview/ui/plugin_proxy.ts
+@@ -85,7 +85,7 @@ export class PluginProxyImpl implements PluginProxy {
+     assert(!this.plugin_);
+     const srcUrl = this.getPreviewUrl_(previewUid, index);
+     this.plugin_ = pdfCreateOutOfProcessPlugin(
+-        srcUrl, 'chrome://print/pdf/index_print.html');
++        srcUrl, 'dao://print/pdf/index_print.html');
+     this.plugin_.classList.add('preview-area-plugin');
+     // NOTE: The plugin's 'id' field must be set to 'pdf-viewer' since
+     // chrome/renderer/printing/print_render_frame_helper.cc actually

src/patches/chrome/renderer/chrome_content_renderer_client.cc.patch

@@ -0,0 +1,15 @@
+diff --git a/chrome/renderer/chrome_content_renderer_client.cc b/chrome/renderer/chrome_content_renderer_client.cc
+index dcc6684123..a1b9be928a 100644
+--- a/chrome/renderer/chrome_content_renderer_client.cc
++++ b/chrome/renderer/chrome_content_renderer_client.cc
+@@ -305,7 +305,9 @@ namespace {
+ 
+ #if BUILDFLAG(ENABLE_PDF)
+ std::vector<url::Origin> GetAdditionalPdfInternalPluginAllowedOrigins() {
+-  return {url::Origin::Create(GURL(chrome::kChromeUIPrintURL))};
++  return {url::Origin::Create(GURL(chrome::kChromeUIPrintURL)),
++          url::Origin::Create(
++              GURL("dao://print/"))};
+ }
+ #endif  // BUILDFLAG(ENABLE_PDF)
+ 

src/patches/components/printing/resources/print_header_footer_template_page.html.patch

@@ -0,0 +1,12 @@
+diff --git a/components/printing/resources/print_header_footer_template_page.html b/components/printing/resources/print_header_footer_template_page.html
+index 5eaabb5798..8488d3dedd 100644
+--- a/components/printing/resources/print_header_footer_template_page.html
++++ b/components/printing/resources/print_header_footer_template_page.html
+@@ -1,7 +1,6 @@
+ <!doctype html>
+ <html>
+ <head>
+-<link rel="stylesheet" href="chrome://resources/css/text_defaults.css">
+ <style>
+   body {
+     display: flex;

src/patches/content/browser/webui/web_ui_data_source_impl.cc.patch

@@ -1,8 +1,67 @@
 diff --git a/content/browser/webui/web_ui_data_source_impl.cc b/content/browser/webui/web_ui_data_source_impl.cc
-index 8dd7796aab..d915b82723 100644
+index 07cdf7dde6..98b3f8e052 100644
 --- a/content/browser/webui/web_ui_data_source_impl.cc
 +++ b/content/browser/webui/web_ui_data_source_impl.cc
-@@ -340,6 +340,7 @@ void WebUIDataSourceImpl::AddFrameAncestor(const GURL& frame_ancestor) {
+@@ -133,6 +133,45 @@ void GetDataResourceBytesOnWorkerThreadFromDisk(
+ }
+ #endif  // BUILDFLAG(LOAD_WEBUI_FROM_DISK)
+ 
++// Dao Browser: kChromeUIScheme is renamed from "chrome" to "dao". Many
++// upstream Chromium WebUIs hard-code "chrome://..." source-list tokens in
++// their CSP strings (e.g. `script-src chrome://resources chrome://webui-test
++// 'self';`). Rather than patching every such WebUI, mirror every
++// "chrome://X" token in a CSP value to also include the matching "dao://X"
++// token (and vice versa), so loads from either scheme are allowed regardless
++// of which one the caller spelled. This is paired with the URLDataSource
++// patch that serves both schemes from the same data source.
++std::string MirrorChromeAndDaoSchemesInCsp(const std::string& value) {
++  static constexpr const char* kPrefixPairs[][2] = {
++      {"chrome://", "dao://"},
++      {"dao://", "chrome://"},
++  };
++  std::string result = value;
++  for (const auto& pair : kPrefixPairs) {
++    const std::string from_prefix = pair[0];
++    const std::string to_prefix = pair[1];
++    size_t scan_pos = 0;
++    while ((scan_pos = result.find(from_prefix, scan_pos)) !=
++           std::string::npos) {
++      size_t end = result.find_first_of(" \t;", scan_pos);
++      if (end == std::string::npos) {
++        end = result.size();
++      }
++      const std::string from_token = result.substr(scan_pos, end - scan_pos);
++      const std::string to_token =
++          to_prefix + from_token.substr(from_prefix.size());
++      if (result.find(to_token) == std::string::npos) {
++        const std::string insertion = " " + to_token;
++        result.insert(end, insertion);
++        scan_pos = end + insertion.size();
++      } else {
++        scan_pos = end;
++      }
++    }
++  }
++  return result;
++}
++
+ }  // namespace
+ 
+ // Internal class to hide the fact that WebUIDataSourceImpl implements
+@@ -318,7 +357,11 @@ bool WebUIDataSourceImpl::IsWebUIDataSourceImpl() const {
+ void WebUIDataSourceImpl::OverrideContentSecurityPolicy(
+     network::mojom::CSPDirectiveName directive,
+     const std::string& value) {
+-  csp_overrides_.insert_or_assign(directive, value);
++  // Dao Browser: rewrite the CSP value so any hard-coded "chrome://..." or
++  // "dao://..." source-list token is mirrored to the other scheme. See
++  // MirrorChromeAndDaoSchemesInCsp() above for rationale.
++  csp_overrides_.insert_or_assign(directive,
++                                  MirrorChromeAndDaoSchemesInCsp(value));
+ }
+ 
+ void WebUIDataSourceImpl::OverrideCrossOriginOpenerPolicy(
+@@ -350,6 +393,7 @@ void WebUIDataSourceImpl::AddFrameAncestor(const GURL& frame_ancestor) {
    // Do not allow a wildcard to be a frame ancestor or it will allow any website
    // to embed the WebUI.
    CHECK(frame_ancestor.SchemeIs(kChromeUIScheme) ||

src/patches/pdf/pdf_view_web_plugin.cc.patch

@@ -0,0 +1,34 @@
+diff --git a/pdf/pdf_view_web_plugin.cc b/pdf/pdf_view_web_plugin.cc
+index 1f1e8cb39d..205760c727 100644
+--- a/pdf/pdf_view_web_plugin.cc
++++ b/pdf/pdf_view_web_plugin.cc
+@@ -152,6 +152,9 @@ constexpr std::string_view kChromeExtensionHost =
+ // Print Preview base URL.
+ constexpr std::string_view kChromePrintHost = "chrome://print/";
+ 
++// Dao Browser Print Preview base URL.
++constexpr std::string_view kDaoPrintHost = "dao://print/";
++
+ // Untrusted Print Preview base URL.
+ constexpr std::string_view kChromeUntrustedPrintHost =
+     "chrome-untrusted://print/";
+@@ -244,6 +247,10 @@ bool IsPrintPreviewUrl(std::string_view url) {
+   return base::StartsWith(url, kChromeUntrustedPrintHost);
+ }
+ 
++bool IsPrintPreviewEmbedderOrigin(std::string_view origin) {
++  return origin == kChromePrintHost || origin == kDaoPrintHost;
++}
++
+ int ExtractPrintPreviewPageIndex(std::string_view src_url) {
+   // Sample `src_url` format: chrome-untrusted://print/id/page_index/print.pdf
+   // The page_index is zero-based, but can be negative with special meanings.
+@@ -573,7 +580,7 @@ bool PdfViewWebPlugin::InitializeCommon() {
+   // This is enforced before creating the plugin (see
+   // `pdf::CreateInternalPlugin()`), so we just `CHECK` for defense-in-depth.
+   const std::string& embedder_origin = client_->GetEmbedderOriginString();
+-  is_print_preview_ = (embedder_origin == kChromePrintHost);
++  is_print_preview_ = IsPrintPreviewEmbedderOrigin(embedder_origin);
+   CHECK(IsPrintPreview() || embedder_origin == kChromeExtensionHost);
+ 
+   full_frame_ = params->full_frame;