Rename "delay" to "timeout" in the SoftwareRateLimiter (3602f27b) · Commits · e / os / android_frameworks_base

services/core/java/com/android/server/locksettings/LockSettingsService.java

+1 −1

Original line number	Diff line number	Diff line
		@@ -2387,7 +2387,7 @@ public class LockSettingsService extends ILockSettings.Stub {
		case SoftwareRateLimiterResult.CONTINUE_TO_HARDWARE:
		break;
		case SoftwareRateLimiterResult.RATE_LIMITED:
		return VerifyCredentialResponse.fromTimeout(res.remainingDelay);
		return VerifyCredentialResponse.fromTimeout(res.timeout);
		case SoftwareRateLimiterResult.CREDENTIAL_TOO_SHORT:
		return VerifyCredentialResponse.credTooShort();
		case SoftwareRateLimiterResult.DUPLICATE_WRONG_GUESS:

services/core/java/com/android/server/locksettings/SoftwareRateLimiter.java

+30 −33

Original line number	Diff line number	Diff line
		@@ -84,10 +84,10 @@ class SoftwareRateLimiter {
		@VisibleForTesting static final Duration SAVED_WRONG_GUESS_TIMEOUT = Duration.ofMinutes(5);

		/**
		* A table that maps the number of (real) failures to the delay that is enforced after that
		* A table that maps the number of (real) failures to the timeout that is enforced after that
		* number of (real) failures. Out-of-bounds indices default to not allowed.
		*/
		private static final Duration[] DELAY_TABLE =
		private static final Duration[] TIMEOUT_TABLE =
		new Duration[] {
		/* 0 */ Duration.ZERO,
		/* 1 */ Duration.ZERO,
		@@ -115,7 +115,7 @@ class SoftwareRateLimiter {

		/**
		* Whether the software rate-limiter is actually in enforcing mode. In non-enforcing mode all
		* delays are considered to be zero, and "duplicate wrong guess" results are not returned.
		* timeouts are considered to be zero, and "duplicate wrong guess" results are not returned.
		*/
		private final boolean mEnforcing;

		@@ -129,7 +129,7 @@ class SoftwareRateLimiter {
		/**
		* The number of failed attempts since the last successful attempt, not counting attempts
		* that never reached the real credential check for a reason such as detection of a
		* duplicate wrong guess, credential too short, delay still remaining, etc.
		* duplicate wrong guess, credential too short, timeout still remaining, etc.
		*/
		public int numFailures;

		@@ -205,7 +205,7 @@ class SoftwareRateLimiter {
		// For LSKF-based synthetic password protectors the only persistent
		// software rate-limiter state is the failure counter.
		// timeSinceBootOfLastFailure is just set to zero, so effectively the
		// delay resets to its original value (for the current failure count)
		// timeout resets to its original value (for the current failure count)
		// upon reboot. That matches what typical hardware rate-limiter
		// implementations do; they typically do not have access to a trusted
		// real-time clock that runs without the device being powered on.
		@@ -214,30 +214,26 @@ class SoftwareRateLimiter {
		return new RateLimiterState(readFailureCounter(id), guess);
		});

		// Check for remaining delay. Note that the case of a positive remaining delay normally
		// won't be reached, since reportFailure() will have returned the delay when the last guess
		// was made, causing the lock screen to block inputs for that amount of time. But checking
		// for it is still needed to cover any cases where a guess gets made anyway, for example
		// following a reboot which causes the lock screen to "forget" the delay.
		final Duration delay;
		// Check for remaining timeout. Note that the case of a positive remaining timeout normally
		// won't be reached, since reportFailure() will have returned the timeout when the last
		// guess was made, causing the lock screen to block inputs for that amount of time. But
		// checking for it is still needed to cover any cases where a guess gets made anyway, for
		// example following a reboot which causes the lock screen to "forget" the timeout.
		final Duration originalTimeout;
		if (mEnforcing) {
		if (state.numFailures >= DELAY_TABLE.length \|\| state.numFailures < 0) {
		if (state.numFailures >= TIMEOUT_TABLE.length \|\| state.numFailures < 0) {
		Slogf.e(TAG, "No more guesses allowed; numFailures=%d", state.numFailures);
		return SoftwareRateLimiterResult.noMoreGuesses();
		}
		delay = DELAY_TABLE[state.numFailures];
		originalTimeout = TIMEOUT_TABLE[state.numFailures];
		} else {
		delay = Duration.ZERO;
		originalTimeout = Duration.ZERO;
		}
		final Duration now = mInjector.getTimeSinceBoot();
		final Duration remainingDelay = state.timeSinceBootOfLastFailure.plus(delay).minus(now);
		if (remainingDelay.isPositive()) {
		Slogf.e(
		TAG,
		"Rate-limited; numFailures=%d, remainingDelay=%s",
		state.numFailures,
		remainingDelay);
		return SoftwareRateLimiterResult.rateLimited(remainingDelay);
		final Duration timeout = state.timeSinceBootOfLastFailure.plus(originalTimeout).minus(now);
		if (timeout.isPositive()) {
		Slogf.e(TAG, "Rate-limited; numFailures=%d, timeout=%s", state.numFailures, timeout);
		return SoftwareRateLimiterResult.rateLimited(timeout);
		}

		// Check for duplicate wrong guess.
		@@ -309,7 +305,7 @@ class SoftwareRateLimiter {
		* @param guess the LSKF that was attempted
		* @param isCertainlyWrongGuess true if it's certain that the failure was caused by the guess
		* being wrong, as opposed to e.g. a transient hardware glitch
		* @return the delay until when the next guess will be allowed
		* @return the remaining timeout until when the next guess will be allowed
		*/
		synchronized Duration reportFailure(
		LskfIdentifier id, LockscreenCredential guess, boolean isCertainlyWrongGuess) {
		@@ -325,10 +321,11 @@ class SoftwareRateLimiter {
		// Increment the failure counter regardless of whether the failure is a certainly wrong
		// guess or not. A generic failure might still be caused by a wrong guess. Gatekeeper only
		// ever returns generic failures, and some Weaver implementations prefer THROTTLE to
		// INCORRECT_KEY once the delay becomes nonzero. Instead of making the software rate-limiter
		// ineffective on all such devices, still apply it. This does mean that correct guesses that
		// encountered an error will be rate-limited. However, by design the rate-limiter kicks in
		// gradually anyway, so there will be a chance for the user to try again.
		// INCORRECT_KEY once the timeout becomes nonzero. Instead of making the software
		// rate-limiter ineffective on all such devices, still apply it. This does mean that correct
		// guesses that encountered an error will be rate-limited. However, by design the
		// rate-limiter kicks in gradually anyway, so there will be a chance for the user to try
		// again.
		state.numFailures++;
		state.timeSinceBootOfLastFailure = mInjector.getTimeSinceBoot();

		@@ -364,12 +361,12 @@ class SoftwareRateLimiter {
		if (!mEnforcing) {
		return Duration.ZERO;
		}
		if (state.numFailures >= DELAY_TABLE.length \|\| state.numFailures < 0) {
		if (state.numFailures >= TIMEOUT_TABLE.length \|\| state.numFailures < 0) {
		// In this case actually no more guesses are allowed, but currently there is no way to
		// convey that information. For now just report the final delay again.
		return DELAY_TABLE[DELAY_TABLE.length - 1];
		// convey that information. For now just report the final timeout again.
		return TIMEOUT_TABLE[TIMEOUT_TABLE.length - 1];
		}
		return DELAY_TABLE[state.numFailures];
		return TIMEOUT_TABLE[state.numFailures];
		}

		private static int getStatsCredentialType(LockscreenCredential firstGuess) {
		@@ -478,8 +475,8 @@ class SoftwareRateLimiter {

		// Only for unit tests.
		@VisibleForTesting
		Duration[] getDelayTable() {
		return DELAY_TABLE;
		Duration[] getTimeoutTable() {
		return TIMEOUT_TABLE;
		}

		synchronized void dump(IndentingPrintWriter pw) {

services/core/java/com/android/server/locksettings/SoftwareRateLimiterResult.java

+5 −5

Original line number	Diff line number	Diff line
		@@ -54,15 +54,15 @@ class SoftwareRateLimiterResult {
		* preliminary validation done before <em>before</em> the rate-limit check does not have access
		* to the timeout yet, so none is reported for {@link #CREDENTIAL_TOO_SHORT} either.
		*/
		@Nullable public final Duration remainingDelay;
		@Nullable public final Duration timeout;

		// Pre-allocate a CONTINUE_TO_HARDWARE result since it is the most common case.
		private static final SoftwareRateLimiterResult CONTINUE_TO_HARDWARE_RESULT =
		new SoftwareRateLimiterResult(CONTINUE_TO_HARDWARE, null);

		private SoftwareRateLimiterResult(@Code int resultCode, Duration remainingDelay) {
		private SoftwareRateLimiterResult(@Code int resultCode, Duration timeout) {
		this.code = resultCode;
		this.remainingDelay = remainingDelay;
		this.timeout = timeout;
		}

		static SoftwareRateLimiterResult credentialTooShort() {
		@@ -73,8 +73,8 @@ class SoftwareRateLimiterResult {
		return new SoftwareRateLimiterResult(NO_MORE_GUESSES, null);
		}

		static SoftwareRateLimiterResult rateLimited(@NonNull Duration remainingDelay) {
		return new SoftwareRateLimiterResult(RATE_LIMITED, remainingDelay);
		static SoftwareRateLimiterResult rateLimited(@NonNull Duration timeout) {
		return new SoftwareRateLimiterResult(RATE_LIMITED, timeout);
		}

		static SoftwareRateLimiterResult duplicateWrongGuess() {

services/tests/servicestests/src/com/android/server/locksettings/LockSettingsServiceTests.java

+1 −1

Original line number	Diff line number	Diff line
		@@ -761,7 +761,7 @@ public class LockSettingsServiceTests extends BaseLockSettingsServiceTests {

		// Tests that if verifyCredential is passed a correct guess but it fails due to Weaver reporting
		// a status of THROTTLE (which is the expected status when there is a remaining rate-limiting
		// delay in Weaver), then LockSettingsService does not block the same guess from being
		// timeout in Weaver), then LockSettingsService does not block the same guess from being
		// re-attempted and in particular does not reject it as a duplicate wrong guess.
		@Test
		@EnableFlags(android.security.Flags.FLAG_SOFTWARE_RATELIMITER)

services/tests/servicestests/src/com/android/server/locksettings/SoftwareRateLimiterTest.java

+26 −25

Original line number	Diff line number	Diff line
		@@ -64,43 +64,44 @@ public class SoftwareRateLimiterTest {
		public void testRateLimitSchedule() {
		mRateLimiter = new SoftwareRateLimiter(mInjector);
		final LskfIdentifier id = new LskfIdentifier(10, 1000);
		final Duration[] delayTable = mRateLimiter.getDelayTable();
		final Duration[] timeoutTable = mRateLimiter.getTimeoutTable();

		for (int i = 0; i < delayTable.length; i++) {
		for (int i = 0; i < timeoutTable.length; i++) {
		final LockscreenCredential guess = newPassword("password" + i);
		Duration expectedDelay = delayTable[i];
		if (!expectedDelay.isZero()) {
		verifyRateLimited(id, guess, expectedDelay);
		Duration expectedTimeout = timeoutTable[i];
		if (!expectedTimeout.isZero()) {
		verifyRateLimited(id, guess, expectedTimeout);
		mInjector.advanceTime(Duration.ofSeconds(1));
		verifyRateLimited(id, guess, expectedDelay.minus(Duration.ofSeconds(1)));
		mInjector.advanceTime(expectedDelay.minus(Duration.ofMillis(1001)));
		verifyRateLimited(id, guess, expectedTimeout.minus(Duration.ofSeconds(1)));
		mInjector.advanceTime(expectedTimeout.minus(Duration.ofMillis(1001)));
		verifyRateLimited(id, guess, Duration.ofMillis(1));
		mInjector.advanceTime(Duration.ofMillis(1));
		}
		verifyUniqueWrongGuess(id, guess, delayTable[Math.min(i + 1, delayTable.length - 1)]);
		verifyUniqueWrongGuess(
		id, guess, timeoutTable[Math.min(i + 1, timeoutTable.length - 1)]);
		verifyFailureCounter(id, i + 1);
		}
		verifyNoMoreGuesses(id, newPassword("password"));
		}

		// This test re-instantiates the SoftwareRateLimiter, like what happens after a reboot, after
		// there have already been a certain number of wrong guesses. It verifies that the delay for the
		// current number of wrong guesses is reset to its original value and starts counting down from
		// the new instantiation time.
		// there have already been a certain number of wrong guesses. It verifies that the timeout for
		// the current number of wrong guesses is reset to its original value and starts counting down
		// from the new instantiation time.
		@Test
		public void testExistingDelayResetsOnReinstantiation() {
		public void testExistingTimeoutResetsOnReinstantiation() {
		final LskfIdentifier id = new LskfIdentifier(10, 1000);
		final LockscreenCredential guess = newPassword("password");
		final Duration[] delayTable = mRateLimiter.getDelayTable();
		final int numWrongGuesses = delayTable.length - 1;
		final Duration expectedDelay = delayTable[numWrongGuesses];
		final Duration[] timeoutTable = mRateLimiter.getTimeoutTable();
		final int numWrongGuesses = timeoutTable.length - 1;
		final Duration expectedTimeout = timeoutTable[numWrongGuesses];

		mInjector.setTime(Duration.ofSeconds(10));
		mInjector.writeFailureCounter(id, numWrongGuesses);
		mRateLimiter = new SoftwareRateLimiter(mInjector);

		mInjector.setTime(Duration.ofSeconds(1));
		verifyRateLimited(id, guess, expectedDelay.minus(Duration.ofSeconds(1)));
		verifyRateLimited(id, guess, expectedTimeout.minus(Duration.ofSeconds(1)));
		}

		@Test
		@@ -194,7 +195,7 @@ public class SoftwareRateLimiterTest {

		for (int i = 0; i < n; i++) {
		verifyUniqueWrongGuess(id, newPassword("password" + i));
		mInjector.advanceTime(Duration.ofDays(1)); // Advance past any delay
		mInjector.advanceTime(Duration.ofDays(1)); // Advance past any timeout
		}
		SoftwareRateLimiterResult result = mRateLimiter.apply(id, newPassword("password0"));
		assertThat(result.code).isEqualTo(expectedResultCode);
		@@ -206,7 +207,7 @@ public class SoftwareRateLimiterTest {

		for (int i = 0; i < SoftwareRateLimiter.MAX_SAVED_WRONG_GUESSES; i++) {
		verifyUniqueWrongGuess(id, newPassword("password" + i));
		mInjector.advanceTime(Duration.ofDays(1)); // Advance past any delay
		mInjector.advanceTime(Duration.ofDays(1)); // Advance past any timeout
		}
		// The list of saved guesses should now be full. Try the oldest one, which should cause it
		// to be moved to the front of the list.
		@@ -214,7 +215,7 @@ public class SoftwareRateLimiterTest {

		// Try a new guess. Then verify that it caused the eviction of password1, not password0.
		verifyUniqueWrongGuess(id, newPassword("passwordN"));
		mInjector.advanceTime(Duration.ofDays(1)); // Advance past any delay
		mInjector.advanceTime(Duration.ofDays(1)); // Advance past any timeout
		verifyDuplicateWrongGuess(id, newPassword("password0"));
		verifyUniqueWrongGuess(id, newPassword("password1"));
		}
		@@ -496,10 +497,10 @@ public class SoftwareRateLimiterTest {
		}

		private void verifyRateLimited(
		LskfIdentifier id, LockscreenCredential guess, Duration expectedRemainingDelay) {
		LskfIdentifier id, LockscreenCredential guess, Duration expectedTimeout) {
		SoftwareRateLimiterResult result = mRateLimiter.apply(id, guess);
		assertThat(result.code).isEqualTo(RATE_LIMITED);
		assertThat(result.remainingDelay).isEqualTo(expectedRemainingDelay);
		assertThat(result.timeout).isEqualTo(expectedTimeout);
		}

		// Verifies that the rate-limiter returns a status of DUPLICATE_WRONG_GUESS for the given guess.
		@@ -516,14 +517,14 @@ public class SoftwareRateLimiterTest {
		mRateLimiter.reportFailure(id, guess, /* isCertainlyWrongGuess= */ true);
		}

		// Same as above but also verifies the next delay reported by reportFailure().
		// Same as above but also verifies the next timeout reported by reportFailure().
		private void verifyUniqueWrongGuess(
		LskfIdentifier id, LockscreenCredential guess, Duration expectedNextDelay) {
		LskfIdentifier id, LockscreenCredential guess, Duration expectedNextTimeout) {
		SoftwareRateLimiterResult result = mRateLimiter.apply(id, guess);
		assertThat(result.code).isEqualTo(CONTINUE_TO_HARDWARE);
		Duration nextDelay =
		Duration nextTimeout =
		mRateLimiter.reportFailure(id, guess, /* isCertainlyWrongGuess= */ true);
		assertThat(nextDelay).isEqualTo(expectedNextDelay);
		assertThat(nextTimeout).isEqualTo(expectedNextTimeout);
		}

		private void verifyFailureCounter(LskfIdentifier id, int expectedValue) {