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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
#include "nsRFPService.h"
#include <algorithm>
#include <cfloat>
#include <cinttypes>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <new>
#include <type_traits>
#include <utility>
#include "MainThreadUtils.h"
#include "ScopedNSSTypes.h"
#include "mozilla/ArrayIterator.h"
#include "mozilla/Assertions.h"
#include "mozilla/Atomics.h"
#include "mozilla/Casting.h"
#include "mozilla/ClearOnShutdown.h"
#include "mozilla/HashFunctions.h"
#include "mozilla/HelperMacros.h"
#include "mozilla/Likely.h"
#include "mozilla/Logging.h"
#include "mozilla/MacroForEach.h"
#include "mozilla/OriginAttributes.h"
#include "mozilla/Preferences.h"
#include "mozilla/RefPtr.h"
#include "mozilla/Services.h"
#include "mozilla/StaticPrefs_javascript.h"
#include "mozilla/StaticPrefs_network.h"
#include "mozilla/StaticPrefs_privacy.h"
#include "mozilla/StaticPtr.h"
#include "mozilla/TextEvents.h"
#include "mozilla/dom/Document.h"
#include "mozilla/dom/Element.h"
#include "mozilla/dom/KeyboardEventBinding.h"
#include "mozilla/fallible.h"
#include "mozilla/XorShift128PlusRNG.h"
#include "nsBaseHashtable.h"
#include "nsComponentManagerUtils.h"
#include "nsCOMPtr.h"
#include "nsContentUtils.h"
#include "nsCoord.h"
#include "nsTHashMap.h"
#include "nsDebug.h"
#include "nsError.h"
#include "nsHashKeys.h"
#include "nsJSUtils.h"
#include "nsLiteralString.h"
#include "nsPrintfCString.h"
#include "nsServiceManagerUtils.h"
#include "nsString.h"
#include "nsStringFlags.h"
#include "nsTArray.h"
#include "nsTLiteralString.h"
#include "nsTPromiseFlatString.h"
#include "nsTStringRepr.h"
#include "nsXPCOM.h"
#include "nsICookieJarSettings.h"
#include "nsICryptoHash.h"
#include "nsIGlobalObject.h"
#include "nsIObserverService.h"
#include "nsIRandomGenerator.h"
#include "nsIUserIdleService.h"
#include "nsIXULAppInfo.h"
#include "nscore.h"
#include "prenv.h"
#include "prtime.h"
#include "xpcpublic.h"
#include "js/Date.h"
using namespace mozilla;
static mozilla::LazyLogModule gResistFingerprintingLog(
"nsResistFingerprinting");
#define RESIST_FINGERPRINTING_PREF "privacy.resistFingerprinting"
#define RESIST_FINGERPRINTING_PBMODE_PREF "privacy.resistFingerprinting.pbmode"
#define RESIST_FINGERPRINTINGPROTECTION_PREF "privacy.fingerprintingProtection"
#define RESIST_FINGERPRINTINGPROTECTION_PBMODE_PREF \
"privacy.fingerprintingProtection.pbmode"
#define RESIST_FINGERPRINTINGPROTECTION_OVERRIDE_PREF \
"privacy.fingerprintingProtection.overrides"
#define RFP_TIMER_UNCONDITIONAL_VALUE 20
#define PROFILE_INITIALIZED_TOPIC "profile-initial-state"
#define LAST_PB_SESSION_EXITED_TOPIC "last-pb-context-exited"
static constexpr uint32_t kVideoFramesPerSec = 30;
static constexpr uint32_t kVideoDroppedRatio = 5;
#define RFP_DEFAULT_SPOOFING_KEYBOARD_LANG KeyboardLang::EN
#define RFP_DEFAULT_SPOOFING_KEYBOARD_REGION KeyboardRegion::US
// Fingerprinting protections that are enabled by default. This can be
// overridden using the privacy.fingerprintingProtection.overrides pref.
const uint32_t kDefaultFingerintingProtections =
uint32_t(RFPTarget::CanvasRandomization);
// ============================================================================
// ============================================================================
// ============================================================================
// Structural Stuff & Pref Observing
NS_IMPL_ISUPPORTS(nsRFPService, nsIObserver)
static StaticRefPtr<nsRFPService> sRFPService;
static bool sInitialized = false;
// Actually enabled fingerprinting protections.
static Atomic<uint32_t> sEnabledFingerintingProtections;
/* static */
nsRFPService* nsRFPService::GetOrCreate() {
if (!sInitialized) {
sRFPService = new nsRFPService();
nsresult rv = sRFPService->Init();
if (NS_FAILED(rv)) {
sRFPService = nullptr;
return nullptr;
}
ClearOnShutdown(&sRFPService);
sInitialized = true;
}
return sRFPService;
}
static const char* gCallbackPrefs[] = {
RESIST_FINGERPRINTING_PREF,
RESIST_FINGERPRINTING_PBMODE_PREF,
RESIST_FINGERPRINTINGPROTECTION_PREF,
RESIST_FINGERPRINTINGPROTECTION_PBMODE_PREF,
RESIST_FINGERPRINTINGPROTECTION_OVERRIDE_PREF,
nullptr,
};
nsresult nsRFPService::Init() {
MOZ_ASSERT(NS_IsMainThread());
nsresult rv;
nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
NS_ENSURE_TRUE(obs, NS_ERROR_NOT_AVAILABLE);
rv = obs->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
NS_ENSURE_SUCCESS(rv, rv);
if (XRE_IsParentProcess()) {
rv = obs->AddObserver(this, LAST_PB_SESSION_EXITED_TOPIC, false);
NS_ENSURE_SUCCESS(rv, rv);
rv = obs->AddObserver(this, OBSERVER_TOPIC_IDLE_DAILY, false);
NS_ENSURE_SUCCESS(rv, rv);
}
#if defined(XP_WIN)
rv = obs->AddObserver(this, PROFILE_INITIALIZED_TOPIC, false);
NS_ENSURE_SUCCESS(rv, rv);
#endif
Preferences::RegisterCallbacks(nsRFPService::PrefChanged, gCallbackPrefs,
this);
// We backup the original TZ value here.
const char* tzValue = PR_GetEnv("TZ");
if (tzValue != nullptr) {
mInitialTZValue = nsCString(tzValue);
}
// Call Update here to cache the values of the prefs and set the timezone.
UpdateRFPPref();
UpdateFPPOverrideList();
return rv;
}
/* static */
bool nsRFPService::IsRFPEnabledFor(RFPTarget aTarget) {
if (StaticPrefs::privacy_resistFingerprinting_DoNotUseDirectly() ||
StaticPrefs::privacy_resistFingerprinting_pbmode_DoNotUseDirectly()) {
return true;
}
if (StaticPrefs::privacy_fingerprintingProtection_DoNotUseDirectly() ||
StaticPrefs::privacy_fingerprintingProtection_pbmode_DoNotUseDirectly()) {
if (aTarget == RFPTarget::IsAlwaysEnabledForPrecompute) {
return true;
}
// All not yet explicitly defined targets are disabled by default (no
// fingerprinting protection).
if (aTarget == RFPTarget::Unknown) {
return false;
}
return sEnabledFingerintingProtections & uint32_t(aTarget);
}
return false;
}
// This function updates every fingerprinting item necessary except
// timing-related
void nsRFPService::UpdateRFPPref() {
MOZ_ASSERT(NS_IsMainThread());
bool resistFingerprinting = nsContentUtils::ShouldResistFingerprinting();
JS::SetReduceMicrosecondTimePrecisionCallback(
nsRFPService::ReduceTimePrecisionAsUSecsWrapper);
// The JavaScript engine can already set the timezone per realm/global,
// but we think there are still other users of libc that rely
// on the TZ environment variable.
if (!StaticPrefs::privacy_resistFingerprinting_testing_setTZtoUTC()) {
return;
}
if (resistFingerprinting) {
PR_SetEnv("TZ=UTC");
} else if (sInitialized) {
// We will not touch the TZ value if 'privacy.resistFingerprinting' is false
// during the time of initialization.
if (!mInitialTZValue.IsEmpty()) {
nsAutoCString tzValue = "TZ="_ns + mInitialTZValue;
static char* tz = nullptr;
// If the tz has been set before, we free it first since it will be
// allocated a new value later.
if (tz != nullptr) {
free(tz);
}
// PR_SetEnv() needs the input string been leaked intentionally, so
// we copy it here.
tz = ToNewCString(tzValue, mozilla::fallible);
if (tz != nullptr) {
PR_SetEnv(tz);
}
} else {
#if defined(XP_WIN)
// For Windows, we reset the TZ to an empty string. This will make Windows
// to use its system timezone.
PR_SetEnv("TZ=");
#else
// For POSIX like system, we reset the TZ to the /etc/localtime, which is
// the system timezone.
PR_SetEnv("TZ=:/etc/localtime");
#endif
}
}
// If and only if the time zone was changed above, propagate the change to the
// <time.h> functions and the JS runtime.
if (resistFingerprinting || sInitialized) {
// localtime_r (and other functions) may not call tzset, so do this here
// after changing TZ to ensure all <time.h> functions use the new time zone.
#if defined(XP_WIN)
_tzset();
#else
tzset();
#endif
nsJSUtils::ResetTimeZone();
}
}
void nsRFPService::UpdateFPPOverrideList() {
nsAutoString targetOverrides;
nsresult rv = Preferences::GetString(
RESIST_FINGERPRINTINGPROTECTION_OVERRIDE_PREF, targetOverrides);
if (!NS_SUCCEEDED(rv) || targetOverrides.IsEmpty()) {
MOZ_LOG(gResistFingerprintingLog, LogLevel::Warning,
("Could not map any values"));
return;
}
uint32_t enabled = kDefaultFingerintingProtections;
for (const nsAString& each : targetOverrides.Split(',')) {
Maybe<RFPTarget> mappedValue =
nsRFPService::TextToRFPTarget(Substring(each, 1, each.Length() - 1));
if (mappedValue.isSome()) {
RFPTarget target = mappedValue.value();
if (target == RFPTarget::IsAlwaysEnabledForPrecompute ||
target == RFPTarget::Unknown) {
MOZ_LOG(gResistFingerprintingLog, LogLevel::Warning,
("RFPTarget::%s is not a valid value",
NS_ConvertUTF16toUTF8(each).get()));
} else if (each[0] == '+') {
enabled |= uint32_t(target);
MOZ_LOG(gResistFingerprintingLog, LogLevel::Warning,
("Mapped value %s (0x%08x), to an addition, now we have 0x%08x",
NS_ConvertUTF16toUTF8(each).get(), unsigned(target), enabled));
} else if (each[0] == '-') {
enabled &= ~uint32_t(target);
MOZ_LOG(
gResistFingerprintingLog, LogLevel::Warning,
("Mapped value %s (0x%08x) to a subtraction, now we have 0x%08x",
NS_ConvertUTF16toUTF8(each).get(), unsigned(target), enabled));
} else {
MOZ_LOG(gResistFingerprintingLog, LogLevel::Warning,
("Mapped value %s (0x%08x) to an RFPTarget Enum, but the first "
"character wasn't + or -",
NS_ConvertUTF16toUTF8(each).get(), unsigned(target)));
}
} else {
MOZ_LOG(gResistFingerprintingLog, LogLevel::Warning,
("Could not map the value %s to an RFPTarget Enum",
NS_ConvertUTF16toUTF8(each).get()));
}
}
sEnabledFingerintingProtections = enabled;
}
/* static */
Maybe<RFPTarget> nsRFPService::TextToRFPTarget(const nsAString& aText) {
#define ITEM_VALUE(name, value) \
if (aText.EqualsLiteral(#name)) { \
return Some(RFPTarget::name); \
}
#include "RFPTargets.inc"
#undef ITEM_VALUE
return Nothing();
}
void nsRFPService::StartShutdown() {
MOZ_ASSERT(NS_IsMainThread());
nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
if (obs) {
obs->RemoveObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID);
if (XRE_IsParentProcess()) {
obs->RemoveObserver(this, LAST_PB_SESSION_EXITED_TOPIC);
obs->RemoveObserver(this, OBSERVER_TOPIC_IDLE_DAILY);
}
}
Preferences::UnregisterCallbacks(nsRFPService::PrefChanged, gCallbackPrefs,
this);
}
// static
void nsRFPService::PrefChanged(const char* aPref, void* aSelf) {
static_cast<nsRFPService*>(aSelf)->PrefChanged(aPref);
}
void nsRFPService::PrefChanged(const char* aPref) {
nsDependentCString pref(aPref);
if (pref.EqualsLiteral(RESIST_FINGERPRINTINGPROTECTION_OVERRIDE_PREF)) {
UpdateFPPOverrideList();
} else {
UpdateRFPPref();
#if defined(XP_WIN)
if (StaticPrefs::privacy_resistFingerprinting_testing_setTZtoUTC() &&
!XRE_IsE10sParentProcess()) {
// Windows does not follow POSIX. Updates to the TZ environment variable
// are not reflected immediately on that platform as they are on UNIX
// systems without this call.
_tzset();
}
#endif
}
}
NS_IMETHODIMP
nsRFPService::Observe(nsISupports* aObject, const char* aTopic,
const char16_t* aMessage) {
if (strcmp(NS_XPCOM_SHUTDOWN_OBSERVER_ID, aTopic) == 0) {
StartShutdown();
}
#if defined(XP_WIN)
else if (!strcmp(PROFILE_INITIALIZED_TOPIC, aTopic)) {
// If we're e10s, then we don't need to run this, since the child process
// will simply inherit the environment variable from the parent process, in
// which case it's unnecessary to call _tzset().
if (XRE_IsParentProcess() && !XRE_IsE10sParentProcess()) {
// Windows does not follow POSIX. Updates to the TZ environment variable
// are not reflected immediately on that platform as they are on UNIX
// systems without this call.
_tzset();
}
nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
NS_ENSURE_TRUE(obs, NS_ERROR_NOT_AVAILABLE);
nsresult rv = obs->RemoveObserver(this, PROFILE_INITIALIZED_TOPIC);
NS_ENSURE_SUCCESS(rv, rv);
}
#endif
if (strcmp(LAST_PB_SESSION_EXITED_TOPIC, aTopic) == 0) {
// Clear the private session key when the private session ends so that we
// can generate a new key for the new private session.
ClearSessionKey(true);
}
if (!strcmp(OBSERVER_TOPIC_IDLE_DAILY, aTopic)) {
if (StaticPrefs::
privacy_resistFingerprinting_randomization_daily_reset_enabled()) {
ClearSessionKey(false);
}
if (StaticPrefs::
privacy_resistFingerprinting_randomization_daily_reset_private_enabled()) {
ClearSessionKey(true);
}
}
return NS_OK;
}
// ============================================================================
// ============================================================================
// ============================================================================
// Reduce Timer Precision Stuff
constexpr double RFP_TIME_ATOM_MS = 16.667; // 60Hz, 1000/60 but rounded.
/*
In RFP RAF always runs at 60Hz, so we're ~0.02% off of 1000/60 here.
```js
extra_frames_per_frame = 16.667 / (1000/60) - 1 // 0.00028
sec_per_extra_frame = 1 / (extra_frames_per_frame * 60) // 833.33
min_per_extra_frame = sec_per_extra_frame / 60 // 13.89
```
We expect an extra frame every ~14 minutes, which is enough to be smooth.
16.67 would be ~1.4 minutes, which is OK, but is more noticable.
Put another way, if this is the only unacceptable hitch you have across 14
minutes, I'm impressed, and we might revisit this.
*/
/* static */
double nsRFPService::TimerResolution(RTPCallerType aRTPCallerType) {
double prefValue = StaticPrefs::
privacy_resistFingerprinting_reduceTimerPrecision_microseconds();
if (aRTPCallerType == RTPCallerType::ResistFingerprinting) {
return std::max(RFP_TIME_ATOM_MS * 1000.0, prefValue);
}
return prefValue;
}
/**
* The purpose of this function is to deterministicly generate a random midpoint
* between a lower clamped value and an upper clamped value. Assuming a clamping
* resolution of 100, here is an example:
*
* |---------------------------------------|--------------------------|
* lower clamped value (e.g. 300) | upper clamped value (400)
* random midpoint (e.g. 360)
*
* If our actual timestamp (e.g. 325) is below the midpoint, we keep it clamped
* downwards. If it were equal to or above the midpoint (e.g. 365) we would
* round it upwards to the largest clamped value (in this example: 400).
*
* The question is: does time go backwards?
*
* The midpoint is deterministicly random and generated from three components:
* a secret seed, a per-timeline (context) 'mix-in', and a clamped time.
*
* When comparing times across different seed values: time may go backwards.
* For a clamped time of 300, one seed may generate a midpoint of 305 and
* another 395. So comparing an (actual) timestamp of 325 and 351 could see the
* 325 clamped up to 400 and the 351 clamped down to 300. The seed is
* per-process, so this case occurs when one can compare timestamps
* cross-process. This is uncommon (because we don't have site isolation.) The
* circumstances this could occur are BroadcastChannel, Storage Notification,
* and in theory (but not yet implemented) SharedWorker. This should be an
* exhaustive list (at time of comment writing!).
*
* Aside from cross-process communication, derived timestamps across different
* time origins may go backwards. (Specifically, derived means adding two
* timestamps together to get an (approximate) absolute time.)
* Assume a page and a worker. If one calls performance.now() in the page and
* then triggers a call to performance.now() in the worker, the following
* invariant should hold true:
* page.performance.timeOrigin + page.performance.now() <
* worker.performance.timeOrigin + worker.performance.now()
*
* We break this invariant.
*
* The 'Context Mix-in' is a securely generated random seed that is unique for
* each timeline that starts over at zero. It is needed to ensure that the
* sequence of midpoints (as calculated by the secret seed and clamped time)
* does not repeat. In RelativeTimeline.h, we define a 'RelativeTimeline' class
* that can be inherited by any object that has a relative timeline. The most
* obvious examples are Documents and Workers. An attacker could let time go
* forward and observe (roughly) where the random midpoints fall. Then they
* create a new object, time starts back over at zero, and they know
* (approximately) where the random midpoints are.
*
* When the timestamp given is a non-relative timestamp (e.g. it is relative to
* the unix epoch) it is not possible to replay a sequence of random values.
* Thus, providing a zero context pointer is an indicator that the timestamp
* given is absolute and does not need any additional randomness.
*
* @param aClampedTimeUSec [in] The clamped input time in microseconds.
* @param aResolutionUSec [in] The current resolution for clamping in
* microseconds.
* @param aMidpointOut [out] The midpoint, in microseconds, between [0,
* aResolutionUSec].
* @param aContextMixin [in] An opaque random value for relative
* timestamps. 0 for absolute timestamps
* @param aSecretSeed [in] TESTING ONLY. When provided, the current seed
* will be replaced with this value.
* @return A nsresult indicating success of failure. If the
* function failed, nothing is written to aMidpointOut
*/
/* static */
nsresult nsRFPService::RandomMidpoint(long long aClampedTimeUSec,
long long aResolutionUSec,
int64_t aContextMixin,
long long* aMidpointOut,
uint8_t* aSecretSeed /* = nullptr */) {
nsresult rv;
const int kSeedSize = 16;
static Atomic<uint8_t*> sSecretMidpointSeed;
if (MOZ_UNLIKELY(!aMidpointOut)) {
return NS_ERROR_INVALID_ARG;
}
/*
* Below, we will use three different values to seed a fairly simple random
* number generator. On the first run we initiate the secret seed, which
* is mixed in with the time epoch and the context mix in to seed the RNG.
*
* This isn't the most secure method of generating a random midpoint but is
* reasonably performant and should be sufficient for our purposes.
*/
// If we don't have a seed, we need to get one.
if (MOZ_UNLIKELY(!sSecretMidpointSeed)) {
nsCOMPtr<nsIRandomGenerator> randomGenerator =
do_GetService("@mozilla.org/security/random-generator;1", &rv);
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
}
uint8_t* temp = nullptr;
rv = randomGenerator->GenerateRandomBytes(kSeedSize, &temp);
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
}
if (MOZ_UNLIKELY(!sSecretMidpointSeed.compareExchange(nullptr, temp))) {
// Some other thread initted this first, never mind!
delete[] temp;
}
}
// sSecretMidpointSeed is now set, and invariant. The contents of the buffer
// it points to is also invariant, _unless_ this function is called with a
// non-null |aSecretSeed|.
uint8_t* seed = sSecretMidpointSeed;
MOZ_RELEASE_ASSERT(seed);
// If someone has passed in the testing-only parameter, replace our seed with
// it. We do _not_ re-allocate the buffer, since that can lead to UAF below.
// The math could still be racy if the caller supplies a new secret seed while
// some other thread is calling this function, but since this is arcane
// test-only functionality that is used in only one test-case presently, we
// put the burden of using this particular footgun properly on the test code.
if (MOZ_UNLIKELY(aSecretSeed != nullptr)) {
memcpy(seed, aSecretSeed, kSeedSize);
}
// Seed and create our random number generator.
non_crypto::XorShift128PlusRNG rng(aContextMixin ^ *(uint64_t*)(seed),
aClampedTimeUSec ^ *(uint64_t*)(seed + 8));
// Retrieve the output midpoint value.
return NS_ERROR_FAILURE;
}
*aMidpointOut = rng.next() % aResolutionUSec;
return NS_OK;
}
/**
* Given a precision value, this function will reduce a given input time to the
* nearest multiple of that precision.
*
* It will check if it is appropriate to clamp the input time according to the
* values of the given TimerPrecisionType. Note that if one desires a minimum
* precision for Resist Fingerprinting, it is the caller's responsibility to
* provide the correct value. This means you should pass TimerResolution(),
* which enforces a minimum value on the precision based on preferences.
*
* It ensures the given precision value is greater than zero, if it is not it
* returns the input time.
*
* While the correct thing to pass is TimerResolution() we expose it as an
* argument for testing purposes only.
*
* @param aTime [in] The input time to be clamped.
* @param aTimeScale [in] The units the input time is in (Seconds,
* Milliseconds, or Microseconds).
* @param aResolutionUSec [in] The precision (in microseconds) to clamp to.
* @param aContextMixin [in] An opaque random value for relative timestamps.
* 0 for absolute timestamps
* @return If clamping is appropriate, the clamped value of the
* input, otherwise the input.
*/
/* static */
double nsRFPService::ReduceTimePrecisionImpl(double aTime, TimeScale aTimeScale,
double aResolutionUSec,
int64_t aContextMixin,
TimerPrecisionType aType) {
if (aType == TimerPrecisionType::DangerouslyNone) {
return aTime;
}
// This boolean will serve as a flag indicating we are clamping the time
// unconditionally. We do this when timer reduction preference is off; but we
// still want to apply 20us clamping to al timestamps to avoid leaking
// nano-second precision.
bool unconditionalClamping = false;
if (aType == UnconditionalAKAHighRes || aResolutionUSec <= 0) {
unconditionalClamping = true;
aResolutionUSec = RFP_TIMER_UNCONDITIONAL_VALUE; // 20 microseconds
aContextMixin = 0; // Just clarifies our logging statement at the end,
// otherwise unused
}
// Increase the time as needed until it is in microseconds.
// Note that a double can hold up to 2**53 with integer precision. This gives
// us only until June 5, 2255 in time-since-the-epoch with integer precision.
// So we will be losing microseconds precision after that date.
// We think this is okay, and we codify it in some tests.
double timeScaled = aTime * (1000000 / aTimeScale);
// Cut off anything less than a microsecond.
long long timeAsInt = timeScaled;
// If we have a blank context mixin, this indicates we (should) have an
// absolute timestamp. We check the time, and if it less than a unix timestamp
// about 10 years in the past, we output to the log and, in debug builds,
// assert. This is an error case we want to understand and fix: we must have
// given a relative timestamp with a mixin of 0 which is incorrect. Anyone
// running a debug build _probably_ has an accurate clock, and if they don't,
// they'll hopefully find this message and understand why things are crashing.
const long long kFeb282008 = 1204233985000;
if (aContextMixin == 0 && timeAsInt < kFeb282008 && !unconditionalClamping &&
aType != TimerPrecisionType::RFP) {
nsAutoCString type;
TypeToText(aType, type);
MOZ_LOG(
gResistFingerprintingLog, LogLevel::Error,
("About to assert. aTime=%lli<%lli aContextMixin=%" PRId64 " aType=%s",
timeAsInt, kFeb282008, aContextMixin, type.get()));
MOZ_ASSERT(
false,
"ReduceTimePrecisionImpl was given a relative time "
"with an empty context mix-in (or your clock is 10+ years off.) "
"Run this with MOZ_LOG=nsResistFingerprinting:1 to get more details.");
}
// Cast the resolution (in microseconds) to an int.
long long resolutionAsInt = aResolutionUSec;
// Perform the clamping.
// We do a cast back to double to perform the division with doubles, then
// floor the result and the rest occurs with integer precision. This is
// because it gives consistency above and below zero. Above zero, performing
// the division in integers truncates decimals, taking the result closer to
// zero (a floor). Below zero, performing the division in integers truncates
// decimals, taking the result closer to zero (a ceil). The impact of this is
// that comparing two clamped values that should be related by a constant
// (e.g. 10s) that are across the zero barrier will no longer work. We need to
// round consistently towards positive infinity or negative infinity (we chose
// negative.) This can't be done with a truncation, it must be done with
// floor.
long long clamped =
floor(double(timeAsInt) / resolutionAsInt) * resolutionAsInt;
long long midpoint = 0;
long long clampedAndJittered = clamped;
if (!unconditionalClamping &&
StaticPrefs::privacy_resistFingerprinting_reduceTimerPrecision_jitter()) {
if (!NS_FAILED(RandomMidpoint(clamped, resolutionAsInt, aContextMixin,
&midpoint)) &&
timeAsInt >= clamped + midpoint) {
clampedAndJittered += resolutionAsInt;
}
}
// Cast it back to a double and reduce it to the correct units.
double ret = double(clampedAndJittered) / (1000000.0 / double(aTimeScale));
MOZ_LOG(
gResistFingerprintingLog, LogLevel::Verbose,
("Given: (%.*f, Scaled: %.*f, Converted: %lli), Rounding %s with (%lli, "
"Originally %.*f), "
"Intermediate: (%lli), Clamped: (%lli) Jitter: (%i Context: %" PRId64
" Midpoint: %lli) "
"Final: (%lli Converted: %.*f)",
DBL_DIG - 1, aTime, DBL_DIG - 1, timeScaled, timeAsInt,
(unconditionalClamping ? "unconditionally" : "normally"),
resolutionAsInt, DBL_DIG - 1, aResolutionUSec,
(long long)floor(double(timeAsInt) / resolutionAsInt), clamped,
StaticPrefs::privacy_resistFingerprinting_reduceTimerPrecision_jitter(),
aContextMixin, midpoint, clampedAndJittered, DBL_DIG - 1, ret));
return ret;
}
/* static */
double nsRFPService::ReduceTimePrecisionAsUSecs(double aTime,
int64_t aContextMixin,
RTPCallerType aRTPCallerType) {
const auto type = GetTimerPrecisionType(aRTPCallerType);
return nsRFPService::ReduceTimePrecisionImpl(aTime, MicroSeconds,
TimerResolution(aRTPCallerType),
aContextMixin, type);
}
/* static */
double nsRFPService::ReduceTimePrecisionAsMSecs(double aTime,
int64_t aContextMixin,
RTPCallerType aRTPCallerType) {
const auto type = GetTimerPrecisionType(aRTPCallerType);
return nsRFPService::ReduceTimePrecisionImpl(aTime, MilliSeconds,
TimerResolution(aRTPCallerType),
aContextMixin, type);
}
/* static */
double nsRFPService::ReduceTimePrecisionAsMSecsRFPOnly(
double aTime, int64_t aContextMixin, RTPCallerType aRTPCallerType) {
return nsRFPService::ReduceTimePrecisionImpl(
aTime, MilliSeconds, TimerResolution(aRTPCallerType), aContextMixin,
GetTimerPrecisionTypeRFPOnly(aRTPCallerType));
}
/* static */
double nsRFPService::ReduceTimePrecisionAsSecs(double aTime,
int64_t aContextMixin,
RTPCallerType aRTPCallerType) {
const auto type = GetTimerPrecisionType(aRTPCallerType);
return nsRFPService::ReduceTimePrecisionImpl(
aTime, Seconds, TimerResolution(aRTPCallerType), aContextMixin, type);
}
/* static */
double nsRFPService::ReduceTimePrecisionAsSecsRFPOnly(
double aTime, int64_t aContextMixin, RTPCallerType aRTPCallerType) {
return nsRFPService::ReduceTimePrecisionImpl(
aTime, Seconds, TimerResolution(aRTPCallerType), aContextMixin,
GetTimerPrecisionTypeRFPOnly(aRTPCallerType));
}
/* static */
double nsRFPService::ReduceTimePrecisionAsUSecsWrapper(
double aTime, bool aShouldResistFingerprinting, JSContext* aCx) {
MOZ_ASSERT(aCx);
nsCOMPtr<nsIGlobalObject> global = xpc::CurrentNativeGlobal(aCx);
MOZ_ASSERT(global);
RTPCallerType callerType;
if (aShouldResistFingerprinting) {
callerType = RTPCallerType::ResistFingerprinting;
} else if (global->CrossOriginIsolated()) {
callerType = RTPCallerType::CrossOriginIsolated;
} else {
callerType = RTPCallerType::Normal;
}
return nsRFPService::ReduceTimePrecisionImpl(
aTime, MicroSeconds, TimerResolution(callerType),
0, /* For absolute timestamps (all the JS engine does), supply zero
context mixin */
GetTimerPrecisionType(callerType));
}
/* static */
TimerPrecisionType nsRFPService::GetTimerPrecisionType(
RTPCallerType aRTPCallerType) {
if (aRTPCallerType == RTPCallerType::SystemPrincipal) {
return DangerouslyNone;
}
if (aRTPCallerType == RTPCallerType::ResistFingerprinting) {
return RFP;
}
if (StaticPrefs::privacy_reduceTimerPrecision() &&
aRTPCallerType == RTPCallerType::CrossOriginIsolated) {
return UnconditionalAKAHighRes;
}
if (StaticPrefs::privacy_reduceTimerPrecision()) {
return Normal;
}
if (StaticPrefs::privacy_reduceTimerPrecision_unconditional()) {
return UnconditionalAKAHighRes;
}
return DangerouslyNone;
}
/* static */
TimerPrecisionType nsRFPService::GetTimerPrecisionTypeRFPOnly(
RTPCallerType aRTPCallerType) {
if (aRTPCallerType == RTPCallerType::ResistFingerprinting) {
return RFP;
}
if (StaticPrefs::privacy_reduceTimerPrecision_unconditional() &&
aRTPCallerType != RTPCallerType::SystemPrincipal) {
return UnconditionalAKAHighRes;
}
return DangerouslyNone;
}
/* static */
void nsRFPService::TypeToText(TimerPrecisionType aType, nsACString& aText) {
switch (aType) {
case TimerPrecisionType::DangerouslyNone:
aText.AssignLiteral("DangerouslyNone");
return;
case TimerPrecisionType::Normal:
aText.AssignLiteral("Normal");
return;
case TimerPrecisionType::RFP:
aText.AssignLiteral("RFP");
return;
case TimerPrecisionType::UnconditionalAKAHighRes:
aText.AssignLiteral("UnconditionalAKAHighRes");
return;
default:
MOZ_ASSERT(false, "Shouldn't go here");
aText.AssignLiteral("Unknown Enum Value");
return;
}
}
// ============================================================================
// ============================================================================
// ============================================================================
// Video Statistics Spoofing
/* static */
uint32_t nsRFPService::CalculateTargetVideoResolution(uint32_t aVideoQuality) {
return aVideoQuality * NSToIntCeil(aVideoQuality * 16 / 9.0);
}
/* static */
uint32_t nsRFPService::GetSpoofedTotalFrames(double aTime) {
double precision =
TimerResolution(RTPCallerType::ResistFingerprinting) / 1000 / 1000;
double time = floor(aTime / precision) * precision;
return NSToIntFloor(time * kVideoFramesPerSec);
}
/* static */
uint32_t nsRFPService::GetSpoofedDroppedFrames(double aTime, uint32_t aWidth,
uint32_t aHeight) {
uint32_t targetRes = CalculateTargetVideoResolution(
StaticPrefs::privacy_resistFingerprinting_target_video_res());
// The video resolution is less than or equal to the target resolution, we
// report a zero dropped rate for this case.
if (targetRes >= aWidth * aHeight) {
return 0;
}
double precision =
TimerResolution(RTPCallerType::ResistFingerprinting) / 1000 / 1000;
double time = floor(aTime / precision) * precision;
// Bound the dropped ratio from 0 to 100.
uint32_t boundedDroppedRatio = std::min(kVideoDroppedRatio, 100U);
return NSToIntFloor(time * kVideoFramesPerSec *
(boundedDroppedRatio / 100.0));
}
/* static */
uint32_t nsRFPService::GetSpoofedPresentedFrames(double aTime, uint32_t aWidth,
uint32_t aHeight) {
uint32_t targetRes = CalculateTargetVideoResolution(
StaticPrefs::privacy_resistFingerprinting_target_video_res());
// The target resolution is greater than the current resolution. For this
// case, there will be no dropped frames, so we report total frames directly.
if (targetRes >= aWidth * aHeight) {
return GetSpoofedTotalFrames(aTime);
}
double precision =
TimerResolution(RTPCallerType::ResistFingerprinting) / 1000 / 1000;
double time = floor(aTime / precision) * precision;
// Bound the dropped ratio from 0 to 100.
uint32_t boundedDroppedRatio = std::min(kVideoDroppedRatio, 100U);
return NSToIntFloor(time * kVideoFramesPerSec *
((100 - boundedDroppedRatio) / 100.0));
}
// ============================================================================
// ============================================================================
// ============================================================================
// User-Agent/Version Stuff
static const char* GetSpoofedVersion() {
#ifdef ANDROID
// Return Desktop's ESR version.
// When Android RFP returns an ESR version >= 120, we can remove the "rv:109"
// spoofing in GetSpoofedUserAgent() below and stop #including
// StaticPrefs_network.h.
return "115.0";
#else
return MOZILLA_UAVERSION;
#endif
}
/* static */
void nsRFPService::GetSpoofedUserAgent(nsACString& userAgent,
bool isForHTTPHeader) {
// This function generates the spoofed value of User Agent.
// We spoof the values of the platform and Firefox version, which could be
// used as fingerprinting sources to identify individuals.
// Reference of the format of User Agent:
// These magic numbers are the lengths of the UA string literals below.
// Assume three-digit Firefox version numbers so we have room to grow.
size_t preallocatedLength =
13 +
(isForHTTPHeader ? mozilla::ArrayLength(SPOOFED_HTTP_UA_OS)
: mozilla::ArrayLength(SPOOFED_UA_OS)) -
1 + 5 + 3 + 10 + mozilla::ArrayLength(LEGACY_UA_GECKO_TRAIL) - 1 + 9 + 3 +
2;
userAgent.SetCapacity(preallocatedLength);
const char* spoofedVersion = GetSpoofedVersion();
// "Mozilla/5.0 (%s; rv:%d.0) Gecko/%d Firefox/%d.0"
userAgent.AssignLiteral("Mozilla/5.0 (");
if (isForHTTPHeader) {
userAgent.AppendLiteral(SPOOFED_HTTP_UA_OS);
} else {
userAgent.AppendLiteral(SPOOFED_UA_OS);
}
userAgent.AppendLiteral("; rv:");
// Desktop Firefox (regular and RFP) won't need to spoof "rv:109" in versions
// as long as Android's GetSpoofedVersion() returns a version < 120 above.
uint32_t forceRV = mozilla::StaticPrefs::network_http_useragent_forceRVOnly();
if (forceRV) {
userAgent.Append(nsPrintfCString("%u.0", forceRV));
} else {
userAgent.Append(spoofedVersion);
}
userAgent.AppendLiteral(") Gecko/");
#if defined(ANDROID)
userAgent.Append(spoofedVersion);
#else
userAgent.AppendLiteral(LEGACY_UA_GECKO_TRAIL);
#endif
userAgent.AppendLiteral(" Firefox/");
userAgent.Append(spoofedVersion);
MOZ_ASSERT(userAgent.Length() <= preallocatedLength);
}
// ============================================================================
// ============================================================================
// ============================================================================
// Keyboard Spoofing Stuff
nsTHashMap<KeyboardHashKey, const SpoofingKeyboardCode*>*
nsRFPService::sSpoofingKeyboardCodes = nullptr;
KeyboardHashKey::KeyboardHashKey(const KeyboardLangs aLang,
const KeyboardRegions aRegion,
const KeyNameIndexType aKeyIdx,
const nsAString& aKey)
: mLang(aLang), mRegion(aRegion), mKeyIdx(aKeyIdx), mKey(aKey) {}
KeyboardHashKey::KeyboardHashKey(KeyTypePointer aOther)
: mLang(aOther->mLang),
mRegion(aOther->mRegion),
mKeyIdx(aOther->mKeyIdx),
mKey(aOther->mKey) {}
KeyboardHashKey::KeyboardHashKey(KeyboardHashKey&& aOther) noexcept
: PLDHashEntryHdr(std::move(aOther)),
mLang(std::move(aOther.mLang)),
mRegion(std::move(aOther.mRegion)),
mKeyIdx(std::move(aOther.mKeyIdx)),
mKey(std::move(aOther.mKey)) {}
KeyboardHashKey::~KeyboardHashKey() = default;
bool KeyboardHashKey::KeyEquals(KeyTypePointer aOther) const {
return mLang == aOther->mLang && mRegion == aOther->mRegion &&
mKeyIdx == aOther->mKeyIdx && mKey == aOther->mKey;
}
KeyboardHashKey::KeyTypePointer KeyboardHashKey::KeyToPointer(KeyType aKey) {
return &aKey;
}
PLDHashNumber KeyboardHashKey::HashKey(KeyTypePointer aKey) {
PLDHashNumber hash = mozilla::HashString(aKey->mKey);
return mozilla::AddToHash(hash, aKey->mRegion, aKey->mKeyIdx, aKey->mLang);
}
/* static */
void nsRFPService::MaybeCreateSpoofingKeyCodes(const KeyboardLangs aLang,
const KeyboardRegions aRegion) {
if (sSpoofingKeyboardCodes == nullptr) {
sSpoofingKeyboardCodes =
new nsTHashMap<KeyboardHashKey, const SpoofingKeyboardCode*>();
}
if (KeyboardLang::EN == aLang) {
switch (aRegion) {
case KeyboardRegion::US:
MaybeCreateSpoofingKeyCodesForEnUS();
break;
}
}
}
/* static */
void nsRFPService::MaybeCreateSpoofingKeyCodesForEnUS() {
MOZ_ASSERT(sSpoofingKeyboardCodes);
static bool sInitialized = false;
const KeyboardLangs lang = KeyboardLang::EN;
const KeyboardRegions reg = KeyboardRegion::US;
if (sInitialized) {
return;
}
static const SpoofingKeyboardInfo spoofingKeyboardInfoTable[] = {
#define KEY(key_, _codeNameIdx, _keyCode, _modifier) \
{NS_LITERAL_STRING_FROM_CSTRING(key_), \
KEY_NAME_INDEX_USE_STRING, \
{CODE_NAME_INDEX_##_codeNameIdx, _keyCode, _modifier}},
#define CONTROL(keyNameIdx_, _codeNameIdx, _keyCode) \
{u""_ns, \
KEY_NAME_INDEX_##keyNameIdx_, \
{CODE_NAME_INDEX_##_codeNameIdx, _keyCode, MODIFIER_NONE}},
#include "KeyCodeConsensus_En_US.h"
#undef CONTROL
#undef KEY
};
for (const auto& keyboardInfo : spoofingKeyboardInfoTable) {
KeyboardHashKey key(lang, reg, keyboardInfo.mKeyIdx, keyboardInfo.mKey);
MOZ_ASSERT(!sSpoofingKeyboardCodes->Contains(key),
"Double-defining key code; fix your KeyCodeConsensus file");
sSpoofingKeyboardCodes->InsertOrUpdate(key, &keyboardInfo.mSpoofingCode);
}
sInitialized = true;
}
/* static */
void nsRFPService::GetKeyboardLangAndRegion(const nsAString& aLanguage,
KeyboardLangs& aLocale,
KeyboardRegions& aRegion) {
nsAutoString langStr;
nsAutoString regionStr;
uint32_t partNum = 0;
for (const nsAString& part : aLanguage.Split('-')) {
if (partNum == 0) {
langStr = part;
} else {
regionStr = part;
break;
}
partNum++;
}
// We test each language here as well as the region. There are some cases that
// only the language is given, we will use the default region code when this
// happens. The default region should depend on the given language.
if (langStr.EqualsLiteral(RFP_KEYBOARD_LANG_STRING_EN)) {
aLocale = KeyboardLang::EN;
// Give default values first.
aRegion = KeyboardRegion::US;
if (regionStr.EqualsLiteral(RFP_KEYBOARD_REGION_STRING_US)) {
aRegion = KeyboardRegion::US;
}
} else {
// There is no spoofed keyboard locale for the given language. We use the
// default one in this case.
aLocale = RFP_DEFAULT_SPOOFING_KEYBOARD_LANG;
aRegion = RFP_DEFAULT_SPOOFING_KEYBOARD_REGION;
}
}
/* static */
bool nsRFPService::GetSpoofedKeyCodeInfo(
const dom::Document* aDoc, const WidgetKeyboardEvent* aKeyboardEvent,
SpoofingKeyboardCode& aOut) {
MOZ_ASSERT(aKeyboardEvent);
KeyboardLangs keyboardLang = RFP_DEFAULT_SPOOFING_KEYBOARD_LANG;
KeyboardRegions keyboardRegion = RFP_DEFAULT_SPOOFING_KEYBOARD_REGION;
// If the document is given, we use the content language which is get from the
// document. Otherwise, we use the default one.
if (aDoc != nullptr) {
nsAutoString language;
aDoc->GetContentLanguage(language);
// If the content-langauge is not given, we try to get langauge from the
// HTML lang attribute.
if (language.IsEmpty()) {
dom::Element* elm = aDoc->GetHtmlElement();
if (elm != nullptr) {
elm->GetLang(language);
}
}
// If two or more languages are given, per HTML5 spec, we should consider
// it as 'unknown'. So we use the default one.
if (!language.IsEmpty() && !language.Contains(char16_t(','))) {
language.StripWhitespace();
GetKeyboardLangAndRegion(language, keyboardLang, keyboardRegion);
}
}
MaybeCreateSpoofingKeyCodes(keyboardLang, keyboardRegion);
KeyNameIndex keyIdx = aKeyboardEvent->mKeyNameIndex;
nsAutoString keyName;
if (keyIdx == KEY_NAME_INDEX_USE_STRING) {
keyName = aKeyboardEvent->mKeyValue;
}
KeyboardHashKey key(keyboardLang, keyboardRegion, keyIdx, keyName);
const SpoofingKeyboardCode* keyboardCode = sSpoofingKeyboardCodes->Get(key);
if (keyboardCode != nullptr) {
aOut = *keyboardCode;
return true;
}
return false;
}
/* static */
bool nsRFPService::GetSpoofedModifierStates(
const dom::Document* aDoc, const WidgetKeyboardEvent* aKeyboardEvent,
const Modifiers aModifier, bool& aOut) {
MOZ_ASSERT(aKeyboardEvent);
// For modifier or control keys, we don't need to hide its modifier states.
if (aKeyboardEvent->mKeyNameIndex != KEY_NAME_INDEX_USE_STRING) {
return false;
}
// We will spoof the modifer state for Alt, Shift, and AltGraph.
// We don't spoof the Control key, because it is often used
// for command key combinations in web apps.
if ((aModifier & (MODIFIER_ALT | MODIFIER_SHIFT | MODIFIER_ALTGRAPH)) != 0) {
SpoofingKeyboardCode keyCodeInfo;
if (GetSpoofedKeyCodeInfo(aDoc, aKeyboardEvent, keyCodeInfo)) {
aOut = ((keyCodeInfo.mModifierStates & aModifier) != 0);
return true;
}
}
return false;
}
/* static */
bool nsRFPService::GetSpoofedCode(const dom::Document* aDoc,
const WidgetKeyboardEvent* aKeyboardEvent,
nsAString& aOut) {
MOZ_ASSERT(aKeyboardEvent);
SpoofingKeyboardCode keyCodeInfo;
if (!GetSpoofedKeyCodeInfo(aDoc, aKeyboardEvent, keyCodeInfo)) {
return false;
}
WidgetKeyboardEvent::GetDOMCodeName(keyCodeInfo.mCode, aOut);
// We need to change the 'Left' with 'Right' if the location indicates
// it's a right key.
if (aKeyboardEvent->mLocation ==
dom::KeyboardEvent_Binding::DOM_KEY_LOCATION_RIGHT &&
StringEndsWith(aOut, u"Left"_ns)) {
aOut.ReplaceLiteral(aOut.Length() - 4, 4, u"Right");
}
return true;
}
/* static */
bool nsRFPService::GetSpoofedKeyCode(const dom::Document* aDoc,
const WidgetKeyboardEvent* aKeyboardEvent,
uint32_t& aOut) {
MOZ_ASSERT(aKeyboardEvent);
SpoofingKeyboardCode keyCodeInfo;
if (GetSpoofedKeyCodeInfo(aDoc, aKeyboardEvent, keyCodeInfo)) {
aOut = keyCodeInfo.mKeyCode;
return true;
}
return false;
}
// ============================================================================
// ============================================================================
// ============================================================================
// Randomization Stuff
nsresult nsRFPService::EnsureSessionKey(bool aIsPrivate) {
MOZ_ASSERT(XRE_IsParentProcess());
MOZ_LOG(gResistFingerprintingLog, LogLevel::Info,
("Ensure the session key for %s browsing session\n",
aIsPrivate ? "private" : "normal"));
if (!StaticPrefs::privacy_resistFingerprinting_randomization_enabled()) {
return NS_ERROR_NOT_AVAILABLE;
}
Maybe<nsID>& sessionKey =
aIsPrivate ? mPrivateBrowsingSessionKey : mBrowsingSessionKey;
// The key has been generated, bail out earlier.
if (sessionKey) {
MOZ_LOG(
gResistFingerprintingLog, LogLevel::Info,
("The %s session key exists: %s\n", aIsPrivate ? "private" : "normal",
sessionKey.ref().ToString().get()));
return NS_OK;
}
sessionKey.emplace(nsID::GenerateUUID());
MOZ_LOG(gResistFingerprintingLog, LogLevel::Debug,
("Generated %s session key: %s\n", aIsPrivate ? "private" : "normal",
sessionKey.ref().ToString().get()));
return NS_OK;
}
void nsRFPService::ClearSessionKey(bool aIsPrivate) {
MOZ_ASSERT(XRE_IsParentProcess());
Maybe<nsID>& sessionKey =
aIsPrivate ? mPrivateBrowsingSessionKey : mBrowsingSessionKey;
sessionKey.reset();
}
// static
Maybe<nsTArray<uint8_t>> nsRFPService::GenerateKey(nsIURI* aTopLevelURI,
bool aIsPrivate) {
MOZ_ASSERT(XRE_IsParentProcess());
MOZ_ASSERT(aTopLevelURI);
MOZ_LOG(gResistFingerprintingLog, LogLevel::Debug,
("Generating %s randomization key for top-level URI: %s\n",
aIsPrivate ? "private" : "normal",
aTopLevelURI->GetSpecOrDefault().get()));
RefPtr<nsRFPService> service = GetOrCreate();
if (NS_FAILED(service->EnsureSessionKey(aIsPrivate))) {
return Nothing();
}
// Return nothing if fingerprinting resistance is disabled or fingerprinting
// resistance is exempted from the normal windows. Note that we still need to
// generate the key for exempted domains because there could be unexempted
// sub-documents that need the key.
if (!nsContentUtils::ShouldResistFingerprinting(
"Coarse Efficiency Check", RFPTarget::CanvasRandomization) ||
(!aIsPrivate &&
StaticPrefs::privacy_resistFingerprinting_testGranularityMask() &
0x02 /* NonPBMExemptMask */)) {
return Nothing();
}
const nsID& sessionKey = aIsPrivate
? service->mPrivateBrowsingSessionKey.ref()
: service->mBrowsingSessionKey.ref();
auto sessionKeyStr = sessionKey.ToString();
// Using the OriginAttributes to get the site from the top-level URI. The site
// is composed of scheme, host, and port.
OriginAttributes attrs;
attrs.SetPartitionKey(aTopLevelURI);
// Generate the key by using the hMAC. The key is based on the session key and
// the partitionKey, i.e. top-level site.
HMAC hmac;
nsresult rv = hmac.Begin(
SEC_OID_SHA256,
Span(reinterpret_cast<const uint8_t*>(sessionKeyStr.get()), NSID_LENGTH));
if (NS_WARN_IF(NS_FAILED(rv))) {
return Nothing();
}
NS_ConvertUTF16toUTF8 topLevelSite(attrs.mPartitionKey);
rv = hmac.Update(reinterpret_cast<const uint8_t*>(topLevelSite.get()),
topLevelSite.Length());
if (NS_WARN_IF(NS_FAILED(rv))) {
return Nothing();
}
Maybe<nsTArray<uint8_t>> key;
key.emplace();
rv = hmac.End(key.ref());
if (NS_WARN_IF(NS_FAILED(rv))) {
return Nothing();
}
return key;
}
// static
nsresult nsRFPService::GenerateCanvasKeyFromImageData(
nsICookieJarSettings* aCookieJarSettings, uint8_t* aImageData,
uint32_t aSize, nsTArray<uint8_t>& aCanvasKey) {
NS_ENSURE_ARG_POINTER(aCookieJarSettings);
nsTArray<uint8_t> randomKey;
nsresult rv =
aCookieJarSettings->GetFingerprintingRandomizationKey(randomKey);
// There is no random key for this cookieJarSettings. This means that the
// randomization is disabled. So, we can bail out from here without doing
// anything.
if (NS_FAILED(rv)) {
return NS_ERROR_FAILURE;
}
// Generate the key for randomizing the canvas data using hMAC. The key is
// based on the random key of the document and the canvas data itself. So,
// different canvas would have different keys.
HMAC hmac;
rv = hmac.Begin(SEC_OID_SHA256, Span(randomKey));
NS_ENSURE_SUCCESS(rv, rv);
rv = hmac.Update(aImageData, aSize);
NS_ENSURE_SUCCESS(rv, rv);
rv = hmac.End(aCanvasKey);
NS_ENSURE_SUCCESS(rv, rv);
return NS_OK;
}
// static
nsresult nsRFPService::RandomizePixels(nsICookieJarSettings* aCookieJarSettings,
uint8_t* aData, uint32_t aSize,
gfx::SurfaceFormat aSurfaceFormat) {
NS_ENSURE_ARG_POINTER(aData);
if (!aCookieJarSettings) {
return NS_OK;
}
if (aSize == 0) {
return NS_OK;
}
nsTArray<uint8_t> canvasKey;
nsresult rv = GenerateCanvasKeyFromImageData(aCookieJarSettings, aData, aSize,
canvasKey);
NS_ENSURE_SUCCESS(rv, rv);
// Calculate the number of pixels based on the given data size. One pixel uses
// 4 bytes that contains ARGB information.
uint32_t pixelCnt = aSize / 4;
// Generate random values that will decide the RGB channel and the pixel
// position that we are going to introduce the noises. The channel and
// position are predictable to ensure we have a consistant result with the
// same canvas in the same browsing session.
// Seed and create the first random number generator which will be used to
// select RGB channel and the pixel position. The seed is the first half of
// the canvas key.
non_crypto::XorShift128PlusRNG rng1(
*reinterpret_cast<uint64_t*>(canvasKey.Elements()),
*reinterpret_cast<uint64_t*>(canvasKey.Elements() + 8));
// Use the last 8 bits as the number of noises.
uint8_t rnd3 = canvasKey.LastElement();
// Clear the last 8 bits.
canvasKey.ReplaceElementAt(canvasKey.Length() - 1, 0);
// Use the remaining 120 bits to seed and create the second random number
// generator. The random number will be used to decided the noise bit that
// will be added to the lowest order bit of the channel of the pixel.
non_crypto::XorShift128PlusRNG rng2(
*reinterpret_cast<uint64_t*>(canvasKey.Elements() + 16),
*reinterpret_cast<uint64_t*>(canvasKey.Elements() + 24));
// Ensure at least 16 random changes may occur.
uint8_t numNoises = std::clamp<uint8_t>(rnd3, 15, 255);
for (uint8_t i = 0; i <= numNoises; i++) {
// Choose which RGB channel to add a noise. The pixel data is in either
// the BGRA or the ARGB format depending on the endianess. To choose the
// color channel we need to add the offset according the endianess.
uint32_t channel;
if (aSurfaceFormat == gfx::SurfaceFormat::B8G8R8A8) {
channel = rng1.next() % 3;
} else if (aSurfaceFormat == gfx::SurfaceFormat::A8R8G8B8) {
channel = rng1.next() % 3 + 1;
} else {
return NS_ERROR_INVALID_ARG;
}
uint32_t idx = 4 * (rng1.next() % pixelCnt) + channel;
uint8_t bit = rng2.next();
aData[idx] = aData[idx] ^ (bit & 0x1);
}
return NS_OK;
}