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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
#include "FontVisibilityProvider.h"
#include "gfxTypes.h"
#include "gfxFontEntry.h"
#include "gfxPlatformFontList.h"
#include "SharedFontList.h"
#include "nsPresContext.h"
#include "nsRFPService.h"
#include "mozilla/StaticPrefs_layout.h"
#include "mozilla/ContentBlockingAllowList.h"
#include "mozilla/dom/OffscreenCanvas.h"
#include "mozilla/dom/Document.h"
#include "mozilla/dom/OffscreenCanvas.h"
using namespace mozilla;
void FontVisibilityProvider::ReportBlockedFontFamily(
const gfxFontFamily& aFamily) const {
nsCString msg;
FormatBlockedFontFamilyMessage(msg, aFamily.Name(), aFamily.Visibility());
ReportBlockedFontFamily(msg);
}
void FontVisibilityProvider::ReportBlockedFontFamily(
const fontlist::Family& aFamily) const {
auto* fontList = gfxPlatformFontList::PlatformFontList()->SharedFontList();
const nsCString& name = aFamily.DisplayName().AsString(fontList);
nsCString msg;
FormatBlockedFontFamilyMessage(msg, name, aFamily.Visibility());
ReportBlockedFontFamily(msg);
}
void FontVisibilityProvider::FormatBlockedFontFamilyMessage(
nsCString& aMsg, const nsCString& aFamily,
FontVisibility aVisibility) const {
aMsg.AppendPrintf(
"Request for font \"%s\" blocked at visibility level %d (requires "
"%d)\n",
aFamily.get(), int(GetFontVisibility()), int(aVisibility));
}
FontVisibility FontVisibilityProvider::ComputeFontVisibility() const {
/*
* Expected behavior in order of precedence:
* 1 If offscreen canvas, attempt to inherit the visibility
* 2 Chrome Rules give User Level (3)
* 3 RFP gives Highest Level (1 aka Base)
* 4 An RFPTarget of Base gives Base Level (1)
* 5 An RFPTarget of LangPack gives LangPack Level (2)
* 6 The value of the Standard Font Visibility Pref
*
* If the ETP toggle is disabled (aka
* ContentBlockingAllowList::Check is true), it will only override 4-6,
* not rules 2 or 3.
*/
// Rule 1: If the visibility should be inherited, return that value.
if (Maybe<FontVisibility> maybeVis = MaybeInheritFontVisibility()) {
return *maybeVis;
}
// Rule 2: Allow all font access for privileged contexts, including
// chrome and devtools contexts.
if (IsChrome()) {
return FontVisibility::User;
}
// Is this a private browsing context?
bool isPrivate = IsPrivateBrowsing();
int32_t level;
// Rule 4
if (ShouldResistFingerprinting(RFPTarget::FontVisibilityBaseSystem)) {
// Rule 3: Check RFP pref
// This is inside Rule 4 in case this document is exempted from RFP.
// But if it is not exempted, and RFP is enabled, we return immediately
// to prevent the override below from occurring.
if (nsRFPService::IsRFPPrefEnabled(isPrivate)) {
return FontVisibility::Base;
}
level = int32_t(FontVisibility::Base);
}
// Rule 5
else if (ShouldResistFingerprinting(RFPTarget::FontVisibilityLangPack)) {
level = int32_t(FontVisibility::LangPack);
}
// Rule 6
else {
level = StaticPrefs::layout_css_font_visibility();
}
nsICookieJarSettings* cookieJarSettings = GetCookieJarSettings();
// Override Rules 4-6 Only: Determine if the user has exempted the
// domain from tracking protections, if so, use the default value.
if (level != StaticPrefs::layout_css_font_visibility() &&
ContentBlockingAllowList::Check(cookieJarSettings)) {
level = StaticPrefs::layout_css_font_visibility();
}
// Clamp result to the valid range of levels.
level = std::clamp(level, int32_t(FontVisibility::Base),
int32_t(FontVisibility::User));
return FontVisibility(level);
}
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