diff options
Diffstat (limited to '')
| -rw-r--r-- | toolkit/components/resistfingerprinting/nsRFPService.cpp | 1461 |
1 files changed, 1461 insertions, 0 deletions
diff --git a/toolkit/components/resistfingerprinting/nsRFPService.cpp b/toolkit/components/resistfingerprinting/nsRFPService.cpp new file mode 100644 index 0000000000..42dca79e25 --- /dev/null +++ b/toolkit/components/resistfingerprinting/nsRFPService.cpp @@ -0,0 +1,1461 @@ +/* -*- 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 http://mozilla.org/MPL/2.0/. */ + +#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. + if (MOZ_UNLIKELY(aResolutionUSec <= 0)) { // ??? Bug 1718066 + 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: + // https://developer.mozilla.org/en-US/docs/Web/API/NavigatorID/userAgent + // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/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 + // >= 120 (bug 1806690), but Android RFP will need to continue spoofing 109 + // 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; +} |