Add Presence FastAdvertisement.
Bug: 219768328
Test: atest NearbyUnitTests
Change-Id: Ia346b2e82682ca4afdbbb0cd69f2e81571946a04
(cherry picked from commit 486cd228c5d0d24857ef959444d026ba2dec8a33)
Merged-In: Ia346b2e82682ca4afdbbb0cd69f2e81571946a04
diff --git a/nearby/service/java/com/android/server/nearby/presence/FastAdvertisement.java b/nearby/service/java/com/android/server/nearby/presence/FastAdvertisement.java
new file mode 100644
index 0000000..e4df673
--- /dev/null
+++ b/nearby/service/java/com/android/server/nearby/presence/FastAdvertisement.java
@@ -0,0 +1,203 @@
+/*
+ * Copyright (C) 2022 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 com.android.server.nearby.presence;
+
+import android.annotation.Nullable;
+import android.nearby.BroadcastRequest;
+import android.nearby.PresenceBroadcastRequest;
+import android.nearby.PresenceCredential;
+
+import com.android.internal.util.Preconditions;
+
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+
+/**
+ * A Nearby Presence advertisement to be advertised on BT4.2 devices.
+ *
+ * <p>Serializable between Java object and bytes formats. Java object is used at the upper scanning
+ * and advertising interface as an abstraction of the actual bytes. Bytes format is used at the
+ * underlying BLE and mDNS stacks, which do necessary slicing and merging based on advertising
+ * capacities.
+ */
+// The fast advertisement is defined in the format below:
+// Header (1 byte) | salt (2 bytes) | identity (14 bytes) | tx_power (1 byte) | actions (1~ bytes)
+// The header contains:
+// version (3 bits) | provision_mode_flag (1 bit) | identity_type (3 bits) |
+// extended_advertisement_mode (1 bit)
+public class FastAdvertisement {
+
+ private static final int FAST_ADVERTISEMENT_MAX_LENGTH = 24;
+
+ static final byte INVALID_TX_POWER = (byte) 0xFF;
+
+ static final int HEADER_LENGTH = 1;
+
+ static final int SALT_LENGTH = 2;
+
+ static final int IDENTITY_LENGTH = 14;
+
+ static final int TX_POWER_LENGTH = 1;
+
+ private static final int MAX_ACTION_COUNT = 6;
+
+ /**
+ * Creates a {@link FastAdvertisement} from a Presence Broadcast Request.
+ */
+ public static FastAdvertisement createFromRequest(PresenceBroadcastRequest request) {
+ byte[] salt = request.getSalt();
+ byte[] identity = request.getCredential().getMetadataEncryptionKey();
+ List<Integer> actions = request.getActions();
+ Preconditions.checkArgument(
+ salt.length == SALT_LENGTH,
+ "FastAdvertisement's salt does not match correct length");
+ Preconditions.checkArgument(
+ identity.length == IDENTITY_LENGTH,
+ "FastAdvertisement's identity does not match correct length");
+ Preconditions.checkArgument(
+ !actions.isEmpty(), "FastAdvertisement must contain at least one action");
+ Preconditions.checkArgument(
+ actions.size() <= MAX_ACTION_COUNT,
+ "FastAdvertisement advertised actions cannot exceed max count " + MAX_ACTION_COUNT);
+
+ return new FastAdvertisement(
+ request.getCredential().getIdentityType(),
+ identity,
+ salt,
+ actions,
+ (byte) request.getTxPower());
+ }
+
+ /** Serialize an {@link FastAdvertisement} object into bytes. */
+ public byte[] toBytes() {
+ ByteBuffer buffer = ByteBuffer.allocate(getLength());
+
+ buffer.put(FastAdvertisementUtils.constructHeader(getVersion(), mIdentityType));
+ buffer.put(mSalt);
+ buffer.put(getIdentity());
+
+ buffer.put(mTxPower == null ? INVALID_TX_POWER : mTxPower);
+ for (int action : mActions) {
+ buffer.put((byte) action);
+ }
+ return buffer.array();
+ }
+
+ private final int mLength;
+
+ private final int mLtvFieldCount;
+
+ @PresenceCredential.IdentityType private final int mIdentityType;
+
+ private final byte[] mIdentity;
+
+ private final byte[] mSalt;
+
+ private final List<Integer> mActions;
+
+ @Nullable
+ private final Byte mTxPower;
+
+ FastAdvertisement(
+ @PresenceCredential.IdentityType int identityType,
+ byte[] identity,
+ byte[] salt,
+ List<Integer> actions,
+ @Nullable Byte txPower) {
+ this.mIdentityType = identityType;
+ this.mIdentity = identity;
+ this.mSalt = salt;
+ this.mActions = actions;
+ this.mTxPower = txPower;
+ int ltvFieldCount = 3;
+ int length =
+ HEADER_LENGTH // header
+ + identity.length
+ + salt.length
+ + actions.size();
+ length += TX_POWER_LENGTH;
+ if (txPower != null) { // TX power
+ ltvFieldCount += 1;
+ }
+ this.mLength = length;
+ this.mLtvFieldCount = ltvFieldCount;
+ Preconditions.checkArgument(
+ length <= FAST_ADVERTISEMENT_MAX_LENGTH,
+ "FastAdvertisement exceeds maximum length");
+ }
+
+ /** Returns the version in the advertisement. */
+ @BroadcastRequest.BroadcastVersion
+ public int getVersion() {
+ return BroadcastRequest.PRESENCE_VERSION_V0;
+ }
+
+ /** Returns the identity type in the advertisement. */
+ @PresenceCredential.IdentityType
+ public int getIdentityType() {
+ return mIdentityType;
+ }
+
+ /** Returns the identity bytes in the advertisement. */
+ public byte[] getIdentity() {
+ return mIdentity.clone();
+ }
+
+ /** Returns the salt of the advertisement. */
+ public byte[] getSalt() {
+ return mSalt.clone();
+ }
+
+ /** Returns the actions in the advertisement. */
+ public List<Integer> getActions() {
+ return new ArrayList<>(mActions);
+ }
+
+ /** Returns the adjusted TX Power in the advertisement. Null if not available. */
+ @Nullable
+ public Byte getTxPower() {
+ return mTxPower;
+ }
+
+ /** Returns the length of the advertisement. */
+ public int getLength() {
+ return mLength;
+ }
+
+ /** Returns the count of LTV fields in the advertisement. */
+ public int getLtvFieldCount() {
+ return mLtvFieldCount;
+ }
+
+ @Override
+ public String toString() {
+ return String.format(
+ "FastAdvertisement:<VERSION: %s, length: %s, ltvFieldCount: %s, identityType: %s,"
+ + " identity: %s, salt: %s, actions: %s, txPower: %s",
+ getVersion(),
+ getLength(),
+ getLtvFieldCount(),
+ getIdentityType(),
+ Arrays.toString(getIdentity()),
+ Arrays.toString(getSalt()),
+ getActions(),
+ getTxPower());
+ }
+}
diff --git a/nearby/service/java/com/android/server/nearby/presence/FastAdvertisementUtils.java b/nearby/service/java/com/android/server/nearby/presence/FastAdvertisementUtils.java
new file mode 100644
index 0000000..ab0a246
--- /dev/null
+++ b/nearby/service/java/com/android/server/nearby/presence/FastAdvertisementUtils.java
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2022 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 com.android.server.nearby.presence;
+
+import android.nearby.BroadcastRequest;
+
+/**
+ * Provides serialization and deserialization util methods for {@link FastAdvertisement}.
+ */
+public final class FastAdvertisementUtils {
+
+ private static final int VERSION_MASK = 0b11100000;
+
+ private static final int IDENTITY_TYPE_MASK = 0b00001110;
+
+ /**
+ * Constructs the header of a {@link FastAdvertisement}.
+ */
+ public static byte constructHeader(@BroadcastRequest.BroadcastVersion int version,
+ int identityType) {
+ return (byte) (((version << 5) & VERSION_MASK) | ((identityType << 1)
+ & IDENTITY_TYPE_MASK));
+ }
+
+ private FastAdvertisementUtils() {}
+}
diff --git a/nearby/tests/unit/src/com/android/server/nearby/presence/FastAdvertisementTest.java b/nearby/tests/unit/src/com/android/server/nearby/presence/FastAdvertisementTest.java
new file mode 100644
index 0000000..19fbbc1
--- /dev/null
+++ b/nearby/tests/unit/src/com/android/server/nearby/presence/FastAdvertisementTest.java
@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2022 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 com.android.server.nearby.presence;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import android.nearby.BroadcastRequest;
+import android.nearby.PresenceBroadcastRequest;
+import android.nearby.PresenceCredential;
+import android.nearby.PrivateCredential;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Collections;
+
+/**
+ * Unit test for {@link FastAdvertisement}.
+ */
+public class FastAdvertisementTest {
+
+ private static final int IDENTITY_TYPE = PresenceCredential.IDENTITY_TYPE_PRIVATE;
+ private static final byte[] IDENTITY = new byte[]{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
+ private static final int MEDIUM_TYPE_BLE = 0;
+ private static final byte[] SALT = {2, 3};
+ private static final byte TX_POWER = 4;
+ private static final int PRESENCE_ACTION = 123;
+ private static final byte[] SECRET_ID = new byte[]{1, 2, 3, 4};
+ private static final byte[] AUTHENTICITY_KEY = new byte[]{12, 13, 14};
+ private static final byte[] EXPECTED_ADV_BYTES =
+ new byte[]{2, 2, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 4, 123};
+
+ private PresenceBroadcastRequest.Builder mBuilder;
+ private PrivateCredential mCredential;
+
+ @Before
+ public void setUp() {
+ mCredential =
+ new PrivateCredential.Builder(SECRET_ID, AUTHENTICITY_KEY)
+ .setIdentityType(PresenceCredential.IDENTITY_TYPE_PRIVATE)
+ .setMetadataEncryptionKey(IDENTITY)
+ .build();
+ mBuilder =
+ new PresenceBroadcastRequest.Builder(Collections.singletonList(MEDIUM_TYPE_BLE),
+ SALT)
+ .setTxPower(TX_POWER)
+ .setCredential(mCredential)
+ .setVersion(BroadcastRequest.PRESENCE_VERSION_V0)
+ .addAction(PRESENCE_ACTION);
+ }
+
+ @Test
+ public void testFastAdvertisementCreateFromRequest() {
+ FastAdvertisement originalAdvertisement = FastAdvertisement.createFromRequest(
+ mBuilder.build());
+
+ assertThat(originalAdvertisement.getActions()).containsExactly(PRESENCE_ACTION);
+ assertThat(originalAdvertisement.getIdentity()).isEqualTo(IDENTITY);
+ assertThat(originalAdvertisement.getIdentityType()).isEqualTo(IDENTITY_TYPE);
+ assertThat(originalAdvertisement.getLtvFieldCount()).isEqualTo(4);
+ assertThat(originalAdvertisement.getLength()).isEqualTo(19);
+ assertThat(originalAdvertisement.getVersion()).isEqualTo(
+ BroadcastRequest.PRESENCE_VERSION_V0);
+ assertThat(originalAdvertisement.getSalt()).isEqualTo(SALT);
+ }
+
+ @Test
+ public void testFastAdvertisementSerialization() {
+ FastAdvertisement originalAdvertisement = FastAdvertisement.createFromRequest(
+ mBuilder.build());
+ byte[] bytes = originalAdvertisement.toBytes();
+
+ assertThat(bytes).hasLength(originalAdvertisement.getLength());
+ assertThat(bytes).isEqualTo(EXPECTED_ADV_BYTES);
+ }
+}