Merge "Fix SntpClient 2036 issue (2/2)"

package android.net;

import android.compat.annotation.UnsupportedAppUsage;

import android.net.sntp.Duration64;

import android.net.sntp.Timestamp64;

import android.os.SystemClock;

import android.util.Log;

import android.util.Slog;

import com.android.internal.annotations.VisibleForTesting;

import com.android.internal.util.TrafficStatsConstants;

import java.net.DatagramSocket;

import java.net.InetAddress;

import java.net.UnknownHostException;

import java.security.NoSuchAlgorithmException;

import java.security.SecureRandom;

import java.time.Duration;

import java.time.Instant;

import java.util.Arrays;

import java.util.Objects;

import java.util.Random;

import java.util.function.Supplier;

/**

    private static final int NTP_STRATUM_DEATH = 0;

    private static final int NTP_STRATUM_MAX = 15;

    // Number of seconds between Jan 1, 1900 and Jan 1, 1970

    // 70 years plus 17 leap days

    private static final long OFFSET_1900_TO_1970 = ((365L * 70L) + 17L) * 24L * 60L * 60L;

    // The source of the current system clock time, replaceable for testing.

    private final Supplier<Instant> mSystemTimeSupplier;

    private final Random mRandom;

    // The last offset calculated from an NTP server response

    private long mClockOffset;

    @UnsupportedAppUsage

    public SntpClient() {

        this(Instant::now);

        this(Instant::now, defaultRandom());

    }

    @VisibleForTesting

    public SntpClient(Supplier<Instant> systemTimeSupplier) {

    public SntpClient(Supplier<Instant> systemTimeSupplier, Random random) {

        mSystemTimeSupplier = Objects.requireNonNull(systemTimeSupplier);

        mRandom = Objects.requireNonNull(random);

    }

    /**

            // get current time and write it to the request packet

            final Instant requestTime = mSystemTimeSupplier.get();

            final long requestTimestamp = requestTime.toEpochMilli();

            final Timestamp64 requestTimestamp = Timestamp64.fromInstant(requestTime);

            final Timestamp64 randomizedRequestTimestamp =

                    requestTimestamp.randomizeSubMillis(mRandom);

            final long requestTicks = SystemClock.elapsedRealtime();

            writeTimeStamp(buffer, TRANSMIT_TIME_OFFSET, requestTimestamp);

            writeTimeStamp(buffer, TRANSMIT_TIME_OFFSET, randomizedRequestTimestamp);

            socket.send(request);

            socket.receive(response);

            final long responseTicks = SystemClock.elapsedRealtime();

            final Instant responseTime = requestTime.plusMillis(responseTicks - requestTicks);

            final long responseTimestamp = responseTime.toEpochMilli();

            final Timestamp64 responseTimestamp = Timestamp64.fromInstant(responseTime);

            // extract the results

            final byte leap = (byte) ((buffer[0] >> 6) & 0x3);

            final byte mode = (byte) (buffer[0] & 0x7);

            final int stratum = (int) (buffer[1] & 0xff);

            final long originateTimestamp = readTimeStamp(buffer, ORIGINATE_TIME_OFFSET);

            final long receiveTimestamp = readTimeStamp(buffer, RECEIVE_TIME_OFFSET);

            final long transmitTimestamp = readTimeStamp(buffer, TRANSMIT_TIME_OFFSET);

            final long referenceTimestamp = readTimeStamp(buffer, REFERENCE_TIME_OFFSET);

            final Timestamp64 referenceTimestamp = readTimeStamp(buffer, REFERENCE_TIME_OFFSET);

            final Timestamp64 originateTimestamp = readTimeStamp(buffer, ORIGINATE_TIME_OFFSET);

            final Timestamp64 receiveTimestamp = readTimeStamp(buffer, RECEIVE_TIME_OFFSET);

            final Timestamp64 transmitTimestamp = readTimeStamp(buffer, TRANSMIT_TIME_OFFSET);

            /* Do validation according to RFC */

            // TODO: validate originateTime == requestTime.

            checkValidServerReply(leap, mode, stratum, transmitTimestamp, referenceTimestamp);

            checkValidServerReply(leap, mode, stratum, transmitTimestamp, referenceTimestamp,

                    randomizedRequestTimestamp, originateTimestamp);

            long roundTripTimeMillis = responseTicks - requestTicks

                    - (transmitTimestamp - receiveTimestamp);

            long totalTransactionDurationMillis = responseTicks - requestTicks;

            long serverDurationMillis =

                    Duration64.between(receiveTimestamp, transmitTimestamp).toDuration().toMillis();

            long roundTripTimeMillis = totalTransactionDurationMillis - serverDurationMillis;

            Duration clockOffsetDuration = calculateClockOffset(requestTimestamp,

                    receiveTimestamp, transmitTimestamp, responseTimestamp);

    /** Performs the NTP clock offset calculation. */

    @VisibleForTesting

    public static Duration calculateClockOffset(long clientRequestTimestamp,

            long serverReceiveTimestamp, long serverTransmitTimestamp,

            long clientResponseTimestamp) {

        // receiveTime = originateTime + transit + skew

        // responseTime = transmitTime + transit - skew

        // clockOffset = ((receiveTime - originateTime) + (transmitTime - responseTime))/2

        //             = ((originateTime + transit + skew - originateTime) +

        //                (transmitTime - (transmitTime + transit - skew)))/2

        //             = ((transit + skew) + (transmitTime - transmitTime - transit + skew))/2

        //             = (transit + skew - transit + skew)/2

        //             = (2 * skew)/2 = skew

        long clockOffsetMillis = ((serverReceiveTimestamp - clientRequestTimestamp)

                + (serverTransmitTimestamp - clientResponseTimestamp)) / 2;

        return Duration.ofMillis(clockOffsetMillis);

    public static Duration calculateClockOffset(Timestamp64 clientRequestTimestamp,

            Timestamp64 serverReceiveTimestamp, Timestamp64 serverTransmitTimestamp,

            Timestamp64 clientResponseTimestamp) {

        // According to RFC4330:

        // t is the system clock offset (the adjustment we are trying to find)

        // t = ((T2 - T1) + (T3 - T4)) / 2

        //

        // Which is:

        // t = (([server]receiveTimestamp - [client]requestTimestamp)

        //       + ([server]transmitTimestamp - [client]responseTimestamp)) / 2

        //

        // See the NTP spec and tests: the numeric types used are deliberate:

        // + Duration64.between() uses 64-bit arithmetic (32-bit for the seconds).

        // + plus() / dividedBy() use Duration, which isn't the double precision floating point

        //   used in NTPv4, but is good enough.

        return Duration64.between(clientRequestTimestamp, serverReceiveTimestamp)

                .plus(Duration64.between(clientResponseTimestamp, serverTransmitTimestamp))

                .dividedBy(2);

    }

    @Deprecated

    }

    private static void checkValidServerReply(

            byte leap, byte mode, int stratum, long transmitTime, long referenceTime)

            throws InvalidServerReplyException {

            byte leap, byte mode, int stratum, Timestamp64 transmitTimestamp,

            Timestamp64 referenceTimestamp, Timestamp64 randomizedRequestTimestamp,

            Timestamp64 originateTimestamp) throws InvalidServerReplyException {

        if (leap == NTP_LEAP_NOSYNC) {

            throw new InvalidServerReplyException("unsynchronized server");

        }

        if ((stratum == NTP_STRATUM_DEATH) || (stratum > NTP_STRATUM_MAX)) {

            throw new InvalidServerReplyException("untrusted stratum: " + stratum);

        }

        if (transmitTime == 0) {

            throw new InvalidServerReplyException("zero transmitTime");

        if (!randomizedRequestTimestamp.equals(originateTimestamp)) {

            throw new InvalidServerReplyException(

                    "originateTimestamp != randomizedRequestTimestamp");

        }

        if (transmitTimestamp.equals(Timestamp64.ZERO)) {

            throw new InvalidServerReplyException("zero transmitTimestamp");

        }

        if (referenceTime == 0) {

            throw new InvalidServerReplyException("zero reference timestamp");

        if (referenceTimestamp.equals(Timestamp64.ZERO)) {

            throw new InvalidServerReplyException("zero referenceTimestamp");

        }

    }

    /**

     * Reads an unsigned 32 bit big endian number from the given offset in the buffer.

     */

    private long read32(byte[] buffer, int offset) {

        byte b0 = buffer[offset];

        byte b1 = buffer[offset+1];

        byte b2 = buffer[offset+2];

        byte b3 = buffer[offset+3];

        // convert signed bytes to unsigned values

        int i0 = ((b0 & 0x80) == 0x80 ? (b0 & 0x7F) + 0x80 : b0);

        int i1 = ((b1 & 0x80) == 0x80 ? (b1 & 0x7F) + 0x80 : b1);

        int i2 = ((b2 & 0x80) == 0x80 ? (b2 & 0x7F) + 0x80 : b2);

        int i3 = ((b3 & 0x80) == 0x80 ? (b3 & 0x7F) + 0x80 : b3);

        return ((long)i0 << 24) + ((long)i1 << 16) + ((long)i2 << 8) + (long)i3;

    private long readUnsigned32(byte[] buffer, int offset) {

        int i0 = buffer[offset++] & 0xFF;

        int i1 = buffer[offset++] & 0xFF;

        int i2 = buffer[offset++] & 0xFF;

        int i3 = buffer[offset] & 0xFF;

        int bits = (i0 << 24) | (i1 << 16) | (i2 << 8) | i3;

        return bits & 0xFFFF_FFFFL;

    }

    /**

     * Reads the NTP time stamp at the given offset in the buffer and returns

     * it as a system time (milliseconds since January 1, 1970).

     * Reads the NTP time stamp from the given offset in the buffer.

     */

    private long readTimeStamp(byte[] buffer, int offset) {

        long seconds = read32(buffer, offset);

        long fraction = read32(buffer, offset + 4);

        // Special case: zero means zero.

        if (seconds == 0 && fraction == 0) {

            return 0;

        }

        return ((seconds - OFFSET_1900_TO_1970) * 1000) + ((fraction * 1000L) / 0x100000000L);

    private Timestamp64 readTimeStamp(byte[] buffer, int offset) {

        long seconds = readUnsigned32(buffer, offset);

        int fractionBits = (int) readUnsigned32(buffer, offset + 4);

        return Timestamp64.fromComponents(seconds, fractionBits);

    }

    /**

     * Writes system time (milliseconds since January 1, 1970) as an NTP time stamp

     * at the given offset in the buffer.

     * Writes the NTP time stamp at the given offset in the buffer.

     */

    private void writeTimeStamp(byte[] buffer, int offset, long time) {

        // Special case: zero means zero.

        if (time == 0) {

            Arrays.fill(buffer, offset, offset + 8, (byte) 0x00);

            return;

        }

        long seconds = time / 1000L;

        long milliseconds = time - seconds * 1000L;

        seconds += OFFSET_1900_TO_1970;

    private void writeTimeStamp(byte[] buffer, int offset, Timestamp64 timestamp) {

        long seconds = timestamp.getEraSeconds();

        // write seconds in big endian format

        buffer[offset++] = (byte)(seconds >> 24);

        buffer[offset++] = (byte)(seconds >> 16);

        buffer[offset++] = (byte)(seconds >> 8);

        buffer[offset++] = (byte)(seconds >> 0);

        buffer[offset++] = (byte) (seconds >>> 24);

        buffer[offset++] = (byte) (seconds >>> 16);

        buffer[offset++] = (byte) (seconds >>> 8);

        buffer[offset++] = (byte) (seconds);

        long fraction = milliseconds * 0x100000000L / 1000L;

        int fractionBits = timestamp.getFractionBits();

        // write fraction in big endian format

        buffer[offset++] = (byte)(fraction >> 24);

        buffer[offset++] = (byte)(fraction >> 16);

        buffer[offset++] = (byte)(fraction >> 8);

        // low order bits should be random data

        buffer[offset++] = (byte)(Math.random() * 255.0);

        buffer[offset++] = (byte) (fractionBits >>> 24);

        buffer[offset++] = (byte) (fractionBits >>> 16);

        buffer[offset++] = (byte) (fractionBits >>> 8);

        buffer[offset] = (byte) (fractionBits);

    }

    private static Random defaultRandom() {

        Random random;

        try {

            random = SecureRandom.getInstanceStrong();

        } catch (NoSuchAlgorithmException e) {

            // This should never happen.

            Slog.wtf(TAG, "Unable to access SecureRandom", e);

            random = new Random(System.currentTimeMillis());

        }

        return random;

    }

}

import java.time.LocalDateTime;

import java.time.ZoneOffset;

import java.util.Arrays;

import java.util.Random;

import java.util.function.Supplier;

@RunWith(AndroidJUnit4.class)

    private SntpClient mClient;

    private Network mNetwork;

    private Supplier<Instant> mSystemTimeSupplier;

    private Random mRandom;

    @SuppressWarnings("unchecked")

    @Before

        // A mock network has NETID_UNSET, which allows the test to run, with a loopback server,

        // even w/o external networking.

        mNetwork = mock(Network.class, CALLS_REAL_METHODS);

        mRandom = mock(Random.class);

        mSystemTimeSupplier = mock(Supplier.class);

        mClient = new SntpClient(mSystemTimeSupplier);

        // Returning zero means the "randomized" bottom bits of the clients transmit timestamp /

        // server's originate timestamp will be zeros.

        when(mRandom.nextInt()).thenReturn(0);

        mClient = new SntpClient(mSystemTimeSupplier, mRandom);

    }

    /** Tests when the client and server are in ERA0. b/199481251. */

            long simulatedClientElapsedTimeMillis = totalElapsedTimeMillis;

            // Create some symmetrical timestamps.

            long clientRequestTimestamp =

                    clientTime.minusMillis(simulatedClientElapsedTimeMillis / 2).toEpochMilli();

            long clientResponseTimestamp =

                    clientTime.plusMillis(simulatedClientElapsedTimeMillis / 2).toEpochMilli();

            long serverReceiveTimestamp =

                    serverTime.minusMillis(simulatedServerElapsedTimeMillis / 2).toEpochMilli();

            long serverTransmitTimestamp =

                    serverTime.plusMillis(simulatedServerElapsedTimeMillis / 2).toEpochMilli();

            Timestamp64 clientRequestTimestamp = Timestamp64.fromInstant(

                    clientTime.minusMillis(simulatedClientElapsedTimeMillis / 2));

            Timestamp64 clientResponseTimestamp = Timestamp64.fromInstant(

                    clientTime.plusMillis(simulatedClientElapsedTimeMillis / 2));

            Timestamp64 serverReceiveTimestamp = Timestamp64.fromInstant(

                    serverTime.minusMillis(simulatedServerElapsedTimeMillis / 2));

            Timestamp64 serverTransmitTimestamp = Timestamp64.fromInstant(

                    serverTime.plusMillis(simulatedServerElapsedTimeMillis / 2));

            Duration actualOffset = SntpClient.calculateClockOffset(

                    clientRequestTimestamp, serverReceiveTimestamp,

/*

 * Copyright (C) 2021 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package android.net.sntp;

import java.util.Random;

class PredictableRandom extends Random {

    private int[] mIntSequence = new int[] { 1 };

    private int mIntPos = 0;

    public void setIntSequence(int[] intSequence) {

        this.mIntSequence = intSequence;

    }

    @Override

    public int nextInt() {

        int value = mIntSequence[mIntPos++];

        mIntPos %= mIntSequence.length;

        return value;

    }

}

import org.junit.Test;

import java.time.Instant;

import java.util.HashSet;

import java.util.Random;

import java.util.Set;

public class Timestamp64Test {

                actualNanos == expectedNanos || actualNanos == expectedNanos - 1);

    }

    @Test

    public void testMillisRandomizationConstant() {

        // Mathematically, we can say that to represent 1000 different values, we need 10 binary

        // digits (2^10 = 1024). The same is true whether we're dealing with integers or fractions.

        // Unfortunately, for fractions those 1024 values do not correspond to discrete decimal

        // values. Discrete millisecond values as fractions (e.g. 0.001 - 0.999) cannot be

        // represented exactly except where the value can also be represented as some combination of

        // powers of -2. When we convert back and forth, we truncate, so millisecond decimal

        // fraction N represented as a binary fraction will always be equal to or lower than N. If

        // we are truncating correctly it will never be as low as (N-0.001). N -> [N-0.001, N].

        // We need to keep 10 bits to hold millis (inaccurately, since there are numbers that

        // cannot be represented exactly), leaving us able to randomize the remaining 22 bits of the

        // fraction part without significantly affecting the number represented.

        assertEquals(22, Timestamp64.SUB_MILLIS_BITS_TO_RANDOMIZE);

        // Brute force proof that randomization logic will keep the timestamp within the range

        // [N-0.001, N] where x is in milliseconds.

        int smallFractionRandomizedLow = 0;

        int smallFractionRandomizedHigh = 0b00000000_00111111_11111111_11111111;

        int largeFractionRandomizedLow = 0b11111111_11000000_00000000_00000000;

        int largeFractionRandomizedHigh = 0b11111111_11111111_11111111_11111111;

        long smallLowNanos = Timestamp64.fromComponents(

                0, smallFractionRandomizedLow).toInstant(0).getNano();

        long smallHighNanos = Timestamp64.fromComponents(

                0, smallFractionRandomizedHigh).toInstant(0).getNano();

        long smallDelta = smallHighNanos - smallLowNanos;

        long millisInNanos = 1_000_000_000 / 1_000;

        assertTrue(smallDelta >= 0 && smallDelta < millisInNanos);

        long largeLowNanos = Timestamp64.fromComponents(

                0, largeFractionRandomizedLow).toInstant(0).getNano();

        long largeHighNanos = Timestamp64.fromComponents(

                0, largeFractionRandomizedHigh).toInstant(0).getNano();

        long largeDelta = largeHighNanos - largeLowNanos;

        assertTrue(largeDelta >= 0 && largeDelta < millisInNanos);

        PredictableRandom random = new PredictableRandom();

        random.setIntSequence(new int[] { 0xFFFF_FFFF });

        Timestamp64 zero = Timestamp64.fromComponents(0, 0);

        Timestamp64 zeroWithFractionRandomized = zero.randomizeSubMillis(random);

        assertEquals(zero.getEraSeconds(), zeroWithFractionRandomized.getEraSeconds());

        assertEquals(smallFractionRandomizedHigh, zeroWithFractionRandomized.getFractionBits());

    }

    @Test

    public void testRandomizeLowestBits() {

        Random random = new Random(1);

        {

            int fractionBits = 0;

            expectIllegalArgumentException(

                    () -> Timestamp64.randomizeLowestBits(random, fractionBits, -1));

            expectIllegalArgumentException(

                    () -> Timestamp64.randomizeLowestBits(random, fractionBits, 0));

            expectIllegalArgumentException(

                    () -> Timestamp64.randomizeLowestBits(random, fractionBits, Integer.SIZE));

            expectIllegalArgumentException(

                    () -> Timestamp64.randomizeLowestBits(random, fractionBits, Integer.SIZE + 1));

        }

        // Check the behavior looks correct from a probabilistic point of view.

        for (int input : new int[] { 0, 0xFFFFFFFF }) {

            for (int bitCount = 1; bitCount < Integer.SIZE; bitCount++) {

                int upperBitMask = 0xFFFFFFFF << bitCount;

                int expectedUpperBits = input & upperBitMask;

                Set<Integer> values = new HashSet<>();

                values.add(input);

                int trials = 100;

                for (int i = 0; i < trials; i++) {

                    int outputFractionBits =

                            Timestamp64.randomizeLowestBits(random, input, bitCount);

                    // Record the output value for later analysis.

                    values.add(outputFractionBits);

                    // Check upper bits did not change.

                    assertEquals(expectedUpperBits, outputFractionBits & upperBitMask);

                }

                // It's possible to be more rigorous here, perhaps with a histogram. As bitCount

                // rises, values.size() quickly trend towards the value of trials + 1. For now, this

                // mostly just guards against a no-op implementation.

                assertTrue(bitCount + ":" + values.size(), values.size() > 1);

            }

        }

    }

    private static void expectIllegalArgumentException(Runnable r) {

        try {

            r.run();