Implementing verification of PROFILE_SELF_TRUSTED. (beff3729) · Commits · e / os / android_frameworks_base

services/core/java/com/android/server/security/AttestationVerificationManagerService.java

+18 −2

Original line number	Diff line number	Diff line
		@@ -16,6 +16,8 @@

		package com.android.server.security;

		import static android.security.attestationverification.AttestationVerificationManager.PROFILE_SELF_TRUSTED;
		import static android.security.attestationverification.AttestationVerificationManager.RESULT_FAILURE;
		import static android.security.attestationverification.AttestationVerificationManager.RESULT_UNKNOWN;

		import android.content.Context;
		@@ -76,10 +78,24 @@ public class AttestationVerificationManagerService extends SystemService {
		private void verifyAttestationForAllVerifiers(
		AttestationProfile profile, int localBindingType, Bundle requirements,
		byte[] attestation, AndroidFuture<IVerificationResult> resultCallback) {
		// TODO(b/201696614): Implement
		IVerificationResult result = new IVerificationResult();
		result.resultCode = RESULT_UNKNOWN;
		// TODO(b/201696614): Implement
		result.token = null;
		switch (profile.getAttestationProfileId()) {
		case PROFILE_SELF_TRUSTED:
		Slog.d(TAG, "Verifying Self trusted profile.");
		try {
		result.resultCode =
		AttestationVerificationSelfTrustedVerifierForTesting.getInstance()
		.verifyAttestation(localBindingType, requirements, attestation);
		} catch (Throwable t) {
		result.resultCode = RESULT_FAILURE;
		}
		break;
		default:
		Slog.d(TAG, "No profile found, defaulting.");
		result.resultCode = RESULT_UNKNOWN;
		}
		resultCallback.complete(result);
		}

services/core/java/com/android/server/security/AttestationVerificationSelfTrustedVerifierForTesting.java

0 → 100644

+224 −0

Original line number	Diff line number	Diff line
		/*
		* 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.security;

		import static android.security.attestationverification.AttestationVerificationManager.PARAM_CHALLENGE;
		import static android.security.attestationverification.AttestationVerificationManager.RESULT_FAILURE;
		import static android.security.attestationverification.AttestationVerificationManager.RESULT_SUCCESS;
		import static android.security.attestationverification.AttestationVerificationManager.TYPE_CHALLENGE;

		import android.annotation.NonNull;
		import android.os.Build;
		import android.os.Bundle;
		import android.security.keystore.KeyGenParameterSpec;
		import android.security.keystore.KeyProperties;
		import android.util.Log;
		import android.util.Slog;

		import com.android.internal.org.bouncycastle.asn1.ASN1InputStream;
		import com.android.internal.org.bouncycastle.asn1.ASN1ObjectIdentifier;
		import com.android.internal.org.bouncycastle.asn1.ASN1OctetString;
		import com.android.internal.org.bouncycastle.asn1.ASN1Sequence;
		import com.android.internal.org.bouncycastle.asn1.x509.Certificate;

		import java.io.ByteArrayInputStream;
		import java.io.IOException;
		import java.security.KeyPairGenerator;
		import java.security.KeyStore;
		import java.security.cert.CertPath;
		import java.security.cert.CertPathValidator;
		import java.security.cert.CertificateEncodingException;
		import java.security.cert.CertificateException;
		import java.security.cert.CertificateFactory;
		import java.security.cert.PKIXParameters;
		import java.security.cert.TrustAnchor;
		import java.security.cert.X509Certificate;
		import java.util.ArrayList;
		import java.util.Arrays;
		import java.util.Collections;
		import java.util.List;
		import java.util.Set;

		/**
		* Verifies {@code PROFILE_SELF_TRUSTED} attestations.
		*
		* Verifies that the attesting environment can create an attestation with the same root certificate
		* as the verifying device with a matching attestation challenge. Skips CRL revocations checking
		* so this verifier can work in a hermetic test environment.
		*
		* This verifier profile is intended to be used only for testing.
		*/
		class AttestationVerificationSelfTrustedVerifierForTesting {
		private static final String TAG = "AVF";
		private static final boolean DEBUG = Build.IS_DEBUGGABLE && Log.isLoggable(TAG, Log.VERBOSE);

		// The OID for the extension Android Keymint puts into device-generated certificates.
		private static final String ANDROID_KEYMINT_KEY_DESCRIPTION_EXTENSION_OID =
		"1.3.6.1.4.1.11129.2.1.17";

		// ASN.1 sequence index values for the Android Keymint extension.
		private static final int ATTESTATION_CHALLENGE_INDEX = 4;

		private static final String ANDROID_KEYSTORE = "AndroidKeyStore";
		private static final String GOLDEN_ALIAS =
		AttestationVerificationSelfTrustedVerifierForTesting.class.getCanonicalName()
		+ ".Golden";

		private static volatile AttestationVerificationSelfTrustedVerifierForTesting
		sAttestationVerificationSelfTrustedVerifier = null;

		private final CertificateFactory mCertificateFactory;
		private final CertPathValidator mCertPathValidator;
		private final KeyStore mAndroidKeyStore;
		private X509Certificate mGoldenRootCert;

		static AttestationVerificationSelfTrustedVerifierForTesting getInstance()
		throws Exception {
		if (sAttestationVerificationSelfTrustedVerifier == null) {
		synchronized (AttestationVerificationSelfTrustedVerifierForTesting.class) {
		if (sAttestationVerificationSelfTrustedVerifier == null) {
		sAttestationVerificationSelfTrustedVerifier =
		new AttestationVerificationSelfTrustedVerifierForTesting();
		}
		}
		}
		return sAttestationVerificationSelfTrustedVerifier;
		}

		private static void debugVerboseLog(String str, Throwable t) {
		if (DEBUG) {
		Slog.v(TAG, str, t);
		}
		}

		private static void debugVerboseLog(String str) {
		if (DEBUG) {
		Slog.v(TAG, str);
		}
		}

		private AttestationVerificationSelfTrustedVerifierForTesting() throws Exception {
		mCertificateFactory = CertificateFactory.getInstance("X.509");
		mCertPathValidator = CertPathValidator.getInstance("PKIX");
		mAndroidKeyStore = KeyStore.getInstance(ANDROID_KEYSTORE);
		mAndroidKeyStore.load(null);
		if (!mAndroidKeyStore.containsAlias(GOLDEN_ALIAS)) {
		KeyPairGenerator kpg =
		KeyPairGenerator.getInstance(KeyProperties.KEY_ALGORITHM_EC, ANDROID_KEYSTORE);
		KeyGenParameterSpec parameterSpec = new KeyGenParameterSpec.Builder(
		GOLDEN_ALIAS, KeyProperties.PURPOSE_SIGN \| KeyProperties.PURPOSE_VERIFY)
		.setAttestationChallenge(GOLDEN_ALIAS.getBytes())
		.setDigests(KeyProperties.DIGEST_SHA256, KeyProperties.DIGEST_SHA512).build();
		kpg.initialize(parameterSpec);
		kpg.generateKeyPair();
		}

		X509Certificate[] goldenCerts = (X509Certificate[])
		((KeyStore.PrivateKeyEntry) mAndroidKeyStore.getEntry(GOLDEN_ALIAS, null))
		.getCertificateChain();
		mGoldenRootCert = goldenCerts[goldenCerts.length - 1];
		}

		int verifyAttestation(
		int localBindingType, @NonNull Bundle requirements, @NonNull byte[] attestation) {
		List<X509Certificate> certificates = new ArrayList<>();
		ByteArrayInputStream bis = new ByteArrayInputStream(attestation);
		try {
		while (bis.available() > 0) {
		certificates.add((X509Certificate) mCertificateFactory.generateCertificate(bis));
		}
		} catch (CertificateException e) {
		debugVerboseLog("Unable to parse certificates from attestation", e);
		return RESULT_FAILURE;
		}

		if (localBindingType == TYPE_CHALLENGE
		&& validateRequirements(requirements)
		&& checkLeafChallenge(requirements, certificates)
		&& verifyCertificateChain(certificates)) {
		return RESULT_SUCCESS;
		}

		return RESULT_FAILURE;
		}

		private boolean verifyCertificateChain(List<X509Certificate> certificates) {
		if (certificates.size() < 2) {
		debugVerboseLog("Certificate chain less than 2 in size.");
		return false;
		}

		try {
		CertPath certificatePath = mCertificateFactory.generateCertPath(certificates);
		PKIXParameters validationParams = new PKIXParameters(getTrustAnchors());
		// Skipping revocation checking because we want this to work in a hermetic test
		// environment.
		validationParams.setRevocationEnabled(false);
		mCertPathValidator.validate(certificatePath, validationParams);
		} catch (Throwable t) {
		debugVerboseLog("Invalid certificate chain", t);
		return false;
		}

		return true;
		}

		private Set<TrustAnchor> getTrustAnchors() {
		return Collections.singleton(new TrustAnchor(mGoldenRootCert, null));
		}

		private boolean validateRequirements(Bundle requirements) {
		if (requirements.size() != 1) {
		debugVerboseLog("Requirements does not contain exactly 1 key.");
		return false;
		}
		if (!requirements.containsKey(PARAM_CHALLENGE)) {
		debugVerboseLog("Requirements does not contain key: " + PARAM_CHALLENGE);
		return false;
		}
		return true;
		}

		private boolean checkLeafChallenge(Bundle requirements, List<X509Certificate> certificates) {
		// Verify challenge
		byte[] challenge;
		try {
		challenge = getChallengeFromCert(certificates.get(0));
		} catch (Throwable t) {
		debugVerboseLog("Unable to parse challenge from certificate.", t);
		return false;
		}

		if (Arrays.equals(requirements.getByteArray(PARAM_CHALLENGE), challenge)) {
		return true;
		} else {
		debugVerboseLog("Self-Trusted validation failed; challenge mismatch.");
		return false;
		}
		}

		private byte[] getChallengeFromCert(@NonNull X509Certificate x509Certificate)
		throws CertificateEncodingException, IOException {
		Certificate certificate = Certificate.getInstance(
		new ASN1InputStream(x509Certificate.getEncoded()).readObject());
		ASN1Sequence keyAttributes = (ASN1Sequence) certificate.getTBSCertificate().getExtensions()
		.getExtensionParsedValue(
		new ASN1ObjectIdentifier(ANDROID_KEYMINT_KEY_DESCRIPTION_EXTENSION_OID));
		return ((ASN1OctetString) keyAttributes.getObjectAt(ATTESTATION_CHALLENGE_INDEX))
		.getOctets();
		}
		}

tests/AttestationVerificationTest/src/android/security/attestationverification/SystemAttestationVerificationTest.kt

+137 −5

Original line number	Diff line number	Diff line
		@@ -11,10 +11,20 @@ import org.junit.Rule
		import org.junit.Test
		import org.junit.runner.RunWith
		import com.google.common.truth.Truth.assertThat
		import android.security.attestationverification.AttestationVerificationManager.PARAM_CHALLENGE
		import android.security.attestationverification.AttestationVerificationManager.PROFILE_PEER_DEVICE
		import android.security.attestationverification.AttestationVerificationManager.PROFILE_SELF_TRUSTED
		import android.security.attestationverification.AttestationVerificationManager.TYPE_PUBLIC_KEY
		import android.security.attestationverification.AttestationVerificationManager.RESULT_FAILURE
		import android.security.attestationverification.AttestationVerificationManager.RESULT_SUCCESS
		import android.security.attestationverification.AttestationVerificationManager.RESULT_UNKNOWN
		import android.security.attestationverification.AttestationVerificationManager.TYPE_PUBLIC_KEY
		import android.security.attestationverification.AttestationVerificationManager.TYPE_CHALLENGE
		import android.security.keystore.KeyGenParameterSpec
		import android.security.keystore.KeyProperties
		import java.lang.IllegalArgumentException
		import java.io.ByteArrayOutputStream
		import java.security.KeyPairGenerator
		import java.security.KeyStore
		import java.time.Duration
		import java.util.concurrent.CompletableFuture
		import java.util.concurrent.TimeUnit
		@@ -23,25 +33,26 @@ import java.util.concurrent.TimeUnit
		@SmallTest
		@RunWith(AndroidJUnit4::class)
		class SystemAttestationVerificationTest {

		@get:Rule
		val rule = ActivityScenarioRule(TestActivity::class.java)

		private lateinit var activity: Activity
		private lateinit var avm: AttestationVerificationManager
		private lateinit var androidKeystore: KeyStore

		@Before
		fun setup() {
		rule.getScenario().onActivity {
		avm = it.getSystemService(AttestationVerificationManager::class.java)
		activity = it
		androidKeystore = KeyStore.getInstance(ANDROID_KEYSTORE).apply { load(null) }
		}
		}

		@Test
		fun verifyAttestation_returnsUnknown() {
		val future = CompletableFuture<Int>()
		val profile = AttestationProfile(PROFILE_SELF_TRUSTED)
		val profile = AttestationProfile(PROFILE_PEER_DEVICE)
		avm.verifyAttestation(profile, TYPE_PUBLIC_KEY, Bundle(), ByteArray(0),
		activity.mainExecutor) { result, _ ->
		future.complete(result)
		@@ -51,9 +62,82 @@ class SystemAttestationVerificationTest {
		}

		@Test
		fun verifyToken_returnsUnknown() {
		fun verifyAttestation_returnsFailureWithEmptyAttestation() {
		val future = CompletableFuture<Int>()
		val profile = AttestationProfile(PROFILE_SELF_TRUSTED)
		avm.verifyAttestation(profile, TYPE_CHALLENGE, Bundle(), ByteArray(0),
		activity.mainExecutor) { result, _ ->
		future.complete(result)
		}

		assertThat(future.getSoon()).isEqualTo(RESULT_FAILURE)
		}

		@Test
		fun verifyAttestation_returnsFailureWithEmptyRequirements() {
		val future = CompletableFuture<Int>()
		val selfTrusted = TestSelfTrustedAttestation("test", "challengeStr")
		avm.verifyAttestation(selfTrusted.profile, selfTrusted.localBindingType,
		Bundle(), selfTrusted.attestation, activity.mainExecutor) { result, _ ->
		future.complete(result)
		}
		assertThat(future.getSoon()).isEqualTo(RESULT_FAILURE)
		}

		@Test
		fun verifyAttestation_returnsFailureWithWrongBindingType() {
		val future = CompletableFuture<Int>()
		val selfTrusted = TestSelfTrustedAttestation("test", "challengeStr")
		avm.verifyAttestation(selfTrusted.profile, TYPE_PUBLIC_KEY,
		selfTrusted.requirements, selfTrusted.attestation, activity.mainExecutor) { result, _ ->
		future.complete(result)
		}
		assertThat(future.getSoon()).isEqualTo(RESULT_FAILURE)
		}

		@Test
		fun verifyAttestation_returnsFailureWithWrongRequirements() {
		val future = CompletableFuture<Int>()
		val selfTrusted = TestSelfTrustedAttestation("test", "challengeStr")
		val wrongKeyRequirements = Bundle()
		wrongKeyRequirements.putByteArray(
		"wrongBindingKey", "challengeStr".encodeToByteArray())
		avm.verifyAttestation(selfTrusted.profile, selfTrusted.localBindingType,
		wrongKeyRequirements, selfTrusted.attestation, activity.mainExecutor) { result, _ ->
		future.complete(result)
		}
		assertThat(future.getSoon()).isEqualTo(RESULT_FAILURE)
		}

		@Test
		fun verifyAttestation_returnsFailureWithWrongChallenge() {
		val future = CompletableFuture<Int>()
		val selfTrusted = TestSelfTrustedAttestation("test", "challengeStr")
		val wrongChallengeRequirements = Bundle()
		wrongChallengeRequirements.putByteArray(PARAM_CHALLENGE, "wrong".encodeToByteArray())
		avm.verifyAttestation(selfTrusted.profile, selfTrusted.localBindingType,
		wrongChallengeRequirements, selfTrusted.attestation, activity.mainExecutor) {
		result, _ -> future.complete(result)
		}
		assertThat(future.getSoon()).isEqualTo(RESULT_FAILURE)
		}

		// TODO(b/216144791): Add more failure tests for PROFILE_SELF_TRUSTED.
		@Test
		fun verifyAttestation_returnsSuccess() {
		val future = CompletableFuture<Int>()
		val selfTrusted = TestSelfTrustedAttestation("test", "challengeStr")
		avm.verifyAttestation(selfTrusted.profile, selfTrusted.localBindingType,
		selfTrusted.requirements, selfTrusted.attestation, activity.mainExecutor) { result, _ ->
		future.complete(result)
		}
		assertThat(future.getSoon()).isEqualTo(RESULT_SUCCESS)
		}

		@Test
		fun verifyToken_returnsUnknown() {
		val future = CompletableFuture<Int>()
		val profile = AttestationProfile(PROFILE_PEER_DEVICE)
		avm.verifyAttestation(profile, TYPE_PUBLIC_KEY, Bundle(), ByteArray(0),
		activity.mainExecutor) { _, token ->
		val result = avm.verifyToken(profile, TYPE_PUBLIC_KEY, Bundle(), token, null)
		@@ -66,7 +150,7 @@ class SystemAttestationVerificationTest {
		@Test
		fun verifyToken_tooBigMaxAgeThrows() {
		val future = CompletableFuture<VerificationToken>()
		val profile = AttestationProfile(PROFILE_SELF_TRUSTED)
		val profile = AttestationProfile(PROFILE_PEER_DEVICE)
		avm.verifyAttestation(profile, TYPE_PUBLIC_KEY, Bundle(), ByteArray(0),
		activity.mainExecutor) { _, token ->
		future.complete(token)
		@@ -87,4 +171,52 @@ class SystemAttestationVerificationTest {
		super.onCreate(savedInstanceState)
		}
		}

		inner class TestSelfTrustedAttestation(val alias: String, val challenge: String) {
		val profile = AttestationProfile(PROFILE_SELF_TRUSTED)
		val localBindingType = TYPE_CHALLENGE
		val requirements: Bundle
		val attestation: ByteArray

		init {
		val challengeByteArray = challenge.encodeToByteArray()
		generateAndStoreKey(alias, challengeByteArray)
		attestation = generateCertificatesByteArray(alias)
		requirements = Bundle()
		requirements.putByteArray(PARAM_CHALLENGE, challengeByteArray)
		}

		private fun generateAndStoreKey(alias: String, challenge: ByteArray) {
		val kpg: KeyPairGenerator = KeyPairGenerator.getInstance(
		KeyProperties.KEY_ALGORITHM_EC,
		ANDROID_KEYSTORE
		)
		val parameterSpec: KeyGenParameterSpec = KeyGenParameterSpec.Builder(
		alias,
		KeyProperties.PURPOSE_SIGN or KeyProperties.PURPOSE_VERIFY
		).run {
		// a challenge results in a generated attestation
		setAttestationChallenge(challenge)
		setDigests(KeyProperties.DIGEST_SHA256, KeyProperties.DIGEST_SHA512)
		build()
		}
		kpg.initialize(parameterSpec)
		kpg.generateKeyPair()
		}

		private fun generateCertificatesByteArray(alias: String): ByteArray {
		val pkEntry = androidKeystore.getEntry(alias, null) as KeyStore.PrivateKeyEntry
		val certs = pkEntry.certificateChain
		val bos = ByteArrayOutputStream()
		certs.forEach {
		bos.write(it.encoded)
		}
		return bos.toByteArray()
		}
		}

		companion object {
		private const val TAG = "AVFTEST"
		private const val ANDROID_KEYSTORE = "AndroidKeyStore"
		}
		}