Catch all exceptions to verifyAttestion() in AVF (cc5a9bf9) · Commits · e / os / android_frameworks_base

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

+4 −3

Original line number	Diff line number	Diff line
		@@ -32,6 +32,7 @@ import com.android.internal.org.bouncycastle.asn1.ASN1Set;
		import com.android.internal.org.bouncycastle.asn1.ASN1TaggedObject;
		import com.android.internal.org.bouncycastle.asn1.x509.Certificate;

		import java.io.IOException;
		import java.nio.charset.StandardCharsets;
		import java.security.cert.CertificateEncodingException;
		import java.security.cert.X509Certificate;
		@@ -147,7 +148,7 @@ class AndroidKeystoreAttestationVerificationAttributes {
		@NonNull
		static AndroidKeystoreAttestationVerificationAttributes fromCertificate(
		@NonNull X509Certificate x509Certificate)
		throws Exception {
		throws CertificateEncodingException, IOException {
		return new AndroidKeystoreAttestationVerificationAttributes(x509Certificate);
		}

		@@ -281,7 +282,7 @@ class AndroidKeystoreAttestationVerificationAttributes {
		}

		private AndroidKeystoreAttestationVerificationAttributes(X509Certificate x509Certificate)
		throws Exception {
		throws CertificateEncodingException, IOException {
		Certificate certificate = Certificate.getInstance(
		new ASN1InputStream(x509Certificate.getEncoded()).readObject());
		ASN1Sequence keyAttributes = (ASN1Sequence) certificate.getTBSCertificate().getExtensions()
		@@ -380,7 +381,7 @@ class AndroidKeystoreAttestationVerificationAttributes {
		}

		private void parseAttestationApplicationId(byte [] attestationApplicationId)
		throws Exception {
		throws IOException {
		ASN1Sequence outerSequence = ASN1Sequence.getInstance(
		new ASN1InputStream(attestationApplicationId).readObject());
		Map<String, Long> packageNameVersion = new HashMap<>();

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

+154 −98

Original line number	Diff line number	Diff line
		@@ -22,8 +22,10 @@ import static android.security.attestationverification.AttestationVerificationMa
		import static android.security.attestationverification.AttestationVerificationManager.RESULT_SUCCESS;
		import static android.security.attestationverification.AttestationVerificationManager.TYPE_CHALLENGE;
		import static android.security.attestationverification.AttestationVerificationManager.TYPE_PUBLIC_KEY;
		import static android.security.attestationverification.AttestationVerificationManager.localBindingTypeToString;

		import static com.android.server.security.AndroidKeystoreAttestationVerificationAttributes.VerifiedBootState.VERIFIED;
		import static com.android.server.security.AndroidKeystoreAttestationVerificationAttributes.fromCertificate;

		import static java.nio.charset.StandardCharsets.UTF_8;

		@@ -31,6 +33,7 @@ import android.annotation.NonNull;
		import android.content.Context;
		import android.os.Build;
		import android.os.Bundle;
		import android.security.attestationverification.AttestationVerificationManager.LocalBindingType;
		import android.util.Log;
		import android.util.Slog;

		@@ -40,8 +43,10 @@ import com.android.internal.annotations.VisibleForTesting;
		import org.json.JSONObject;

		import java.io.ByteArrayInputStream;
		import java.io.IOException;
		import java.io.InputStream;
		import java.net.URL;
		import java.security.InvalidAlgorithmParameterException;
		import java.security.cert.CertPath;
		import java.security.cert.CertPathValidator;
		import java.security.cert.CertPathValidatorException;
		@@ -65,17 +70,26 @@ import java.util.Objects;
		import java.util.Set;

		/**
		* Verifies Android key attestation according to the {@code PROFILE_PEER_DEVICE} profile.
		* Verifies Android key attestation according to the
		* {@link android.security.attestationverification.AttestationVerificationManager#PROFILE_PEER_DEVICE PROFILE_PEER_DEVICE}
		* profile.
		*
		* Trust anchors are vendor-defined via the vendor_required_attestation_certificates.xml resource.
		* <p>
		* The profile is satisfied by checking all the following:
		* * TrustAnchor match
		* * Certificate validity
		* * Android OS 10 or higher
		* * Hardware backed key store
		* * Verified boot locked
		* * Remote Patch level must be within 1 year of local patch if local patch is less than 1 year old.
		* <ul>
		* <li> TrustAnchor match
		* <li> Certificate validity
		* <li> Android OS 10 or higher
		* <li> Hardware backed key store
		* <li> Verified boot locked
		* <li> Remote Patch level must be within 1 year of local patch if local patch is less than 1 year
		* old.
		* </ul>
		*
		* <p>
		* Trust anchors are vendor-defined by populating
		* {@link R.array#vendor_required_attestation_certificates} string array (defenined in
		* {@code frameworks/base/core/res/res/values/vendor_required_attestation_certificates.xml}).
		*/
		class AttestationVerificationPeerDeviceVerifier {
		private static final String TAG = "AVF";
		@@ -87,20 +101,8 @@ class AttestationVerificationPeerDeviceVerifier {
		private final boolean mRevocationEnabled;
		private final LocalDate mTestSystemDate;
		private final LocalDate mTestLocalPatchDate;
		private CertificateFactory mCertificateFactory;
		private CertPathValidator mCertPathValidator;

		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 final CertificateFactory mCertificateFactory;
		private final CertPathValidator mCertPathValidator;

		AttestationVerificationPeerDeviceVerifier(@NonNull Context context) throws Exception {
		mContext = Objects.requireNonNull(context);
		@@ -128,53 +130,71 @@ class AttestationVerificationPeerDeviceVerifier {

		/**
		* Verifies attestation for public key or challenge local binding.
		*
		* <p>
		* The attestations must be suitable for {@link java.security.cert.CertificateFactory}
		* The certificates in the attestation provided must be DER-encoded and may be supplied in
		* binary or printable (Base64) encoding. If the certificate is provided in Base64 encoding,
		* it must be bounded at the beginning by -----BEGIN CERTIFICATE-----, and must be bounded at
		* the end by -----END CERTIFICATE-----.
		* it must be bounded at the beginning by {@code -----BEGIN CERTIFICATE-----}, and must be
		* bounded at the end by {@code -----END CERTIFICATE-----}.
		*
		* @param localBindingType Only {@code TYPE_PUBLIC_KEY} and {@code TYPE_CHALLENGE} supported.
		* @param requirements Only {@code PARAM_PUBLIC_KEY} and {@code PARAM_CHALLENGE} supported.
		* @param attestation Certificates should be DER encoded with leaf certificate appended first.
		*/
		int verifyAttestation(
		int localBindingType, @NonNull Bundle requirements, @NonNull byte[] attestation) {
		int status = RESULT_FAILURE;

		@LocalBindingType int localBindingType,
		@NonNull Bundle requirements,
		@NonNull byte[] attestation) {
		if (mCertificateFactory == null) {
		debugVerboseLog("Was unable to initialize CertificateFactory onCreate.");
		return status;
		debugVerboseLog("Unable to access CertificateFactory");
		return RESULT_FAILURE;
		}

		if (mCertPathValidator == null) {
		debugVerboseLog("Was unable to initialize CertPathValidator onCreate.");
		return status;
		debugVerboseLog("Unable to access CertPathValidator");
		return RESULT_FAILURE;
		}

		// Check if the provided local binding type is supported and if the provided requirements
		// "match" the binding type.
		if (!validateAttestationParameters(localBindingType, requirements)) {
		return RESULT_FAILURE;
		}

		List<X509Certificate> certificates;
		try {
		certificates = getCertificates(attestation);
		} catch (CertificateException e) {
		debugVerboseLog("Unable to parse attestation certificates.", e);
		return status;
		// First: parse and validate the certificate chain.
		final List<X509Certificate> certificateChain = getCertificates(attestation);
		// (returns void, but throws CertificateException and other similar Exceptions)
		validateCertificateChain(certificateChain);

		final var leafCertificate = certificateChain.get(0);
		final var attestationExtension = fromCertificate(leafCertificate);

		// Second: verify if the attestation satisfies the "peer device" porfile.
		if (!checkAttestationForPeerDeviceProfile(attestationExtension)) {
		return RESULT_FAILURE;
		}

		if (certificates.isEmpty()) {
		debugVerboseLog("Attestation contains no certificates.");
		return status;
		// Third: check if the attestation satisfies local binding requirements.
		if (!checkLocalBindingRequirements(
		leafCertificate, attestationExtension, localBindingType, requirements)) {
		return RESULT_FAILURE;
		}

		X509Certificate leafNode = certificates.get(0);
		if (validateRequirements(localBindingType, requirements)
		&& validateCertificateChain(certificates)
		&& checkCertificateAttributes(leafNode, localBindingType, requirements)) {
		status = RESULT_SUCCESS;
		} else {
		status = RESULT_FAILURE;
		return RESULT_SUCCESS;
		} catch (CertificateException \| CertPathValidatorException
		\| InvalidAlgorithmParameterException \| IOException e) {
		// Catch all non-RuntimeExpceptions (all of these are thrown by either getCertificates()
		// or validateCertificateChain() or
		// AndroidKeystoreAttestationVerificationAttributes.fromCertificate())
		debugVerboseLog("Unable to parse/validate Android Attestation certificate(s)", e);
		return RESULT_FAILURE;
		} catch (RuntimeException e) {
		// Catch everyting else (RuntimeExpcetions), since we don't want to throw any exceptions
		// out of this class/method.
		debugVerboseLog("Unexpected error", e);
		return RESULT_FAILURE;
		}
		return status;
		}

		@NonNull
		@@ -189,14 +209,19 @@ class AttestationVerificationPeerDeviceVerifier {
		return certificates;
		}

		private boolean validateRequirements(int localBindingType, Bundle requirements) {
		if (requirements.size() != 1) {
		debugVerboseLog("Requirements does not contain exactly 1 key.");
		/**
		* Check if the {@code localBindingType} is supported and if the {@code requirements} contains
		* the required parameter for the given {@code @LocalBindingType}.
		*/
		private boolean validateAttestationParameters(
		@LocalBindingType int localBindingType, @NonNull Bundle requirements) {
		if (localBindingType != TYPE_PUBLIC_KEY && localBindingType != TYPE_CHALLENGE) {
		debugVerboseLog("Binding type is not supported: " + localBindingType);
		return false;
		}

		if (localBindingType != TYPE_PUBLIC_KEY && localBindingType != TYPE_CHALLENGE) {
		debugVerboseLog("Binding type is not supported: " + localBindingType);
		if (requirements.size() != 1) {
		debugVerboseLog("Requirements does not contain exactly 1 key.");
		return false;
		}

		@@ -213,13 +238,14 @@ class AttestationVerificationPeerDeviceVerifier {
		return true;
		}

		private boolean validateCertificateChain(List<X509Certificate> certificates) {
		private void validateCertificateChain(List<X509Certificate> certificates)
		throws CertificateException, CertPathValidatorException,
		InvalidAlgorithmParameterException {
		if (certificates.size() < 2) {
		debugVerboseLog("Certificate chain less than 2 in size.");
		return false;
		throw new CertificateException("Certificate chain less than 2 in size.");
		}

		try {
		CertPath certificatePath = mCertificateFactory.generateCertPath(certificates);
		PKIXParameters validationParams = new PKIXParameters(mTrustAnchors);
		if (mRevocationEnabled) {
		@@ -231,11 +257,6 @@ class AttestationVerificationPeerDeviceVerifier {
		// Do not use built-in revocation status checker.
		validationParams.setRevocationEnabled(false);
		mCertPathValidator.validate(certificatePath, validationParams);
		} catch (Throwable t) {
		debugVerboseLog("Invalid certificate chain.", t);
		return false;
		}
		return true;
		}

		private Set<TrustAnchor> getTrustAnchors() throws CertPathValidatorException {
		@@ -267,18 +288,44 @@ class AttestationVerificationPeerDeviceVerifier {
		R.array.vendor_required_attestation_certificates);
		}

		private boolean checkCertificateAttributes(
		X509Certificate leafCertificate, int localBindingType, Bundle requirements) {
		AndroidKeystoreAttestationVerificationAttributes attestationAttributes;
		try {
		attestationAttributes =
		AndroidKeystoreAttestationVerificationAttributes.fromCertificate(
		leafCertificate);
		} catch (Throwable t) {
		debugVerboseLog("Could not get ParsedAttestationAttributes from Certificate.", t);
		private boolean checkLocalBindingRequirements(
		@NonNull X509Certificate leafCertificate,
		@NonNull AndroidKeystoreAttestationVerificationAttributes attestationAttributes,
		@LocalBindingType int localBindingType,
		@NonNull Bundle requirements) {
		switch (localBindingType) {
		case TYPE_PUBLIC_KEY:
		// Verify leaf public key matches provided public key.
		final boolean publicKeyMatches = checkPublicKey(
		leafCertificate, requirements.getByteArray(PARAM_PUBLIC_KEY));
		if (!publicKeyMatches) {
		debugVerboseLog(
		"Provided public key does not match leaf certificate public key.");
		return false;
		}
		break;

		case TYPE_CHALLENGE:
		// Verify challenge matches provided challenge.
		final boolean attestationChallengeMatches = checkAttestationChallenge(
		attestationAttributes, requirements.getByteArray(PARAM_CHALLENGE));
		if (!attestationChallengeMatches) {
		debugVerboseLog(
		"Provided challenge does not match leaf certificate challenge.");
		return false;
		}
		break;

		default:
		throw new IllegalArgumentException("Unsupported local binding type "
		+ localBindingTypeToString(localBindingType));
		}

		return true;
		}

		private boolean checkAttestationForPeerDeviceProfile(
		@NonNull AndroidKeystoreAttestationVerificationAttributes attestationAttributes) {
		// Checks for support of Keymaster 4.
		if (attestationAttributes.getAttestationVersion() < 3) {
		debugVerboseLog("Attestation version is not at least 3 (Keymaster 4).");
		@@ -344,23 +391,20 @@ class AttestationVerificationPeerDeviceVerifier {
		return false;
		}

		// Verify leaf public key matches provided public key.
		if (localBindingType == TYPE_PUBLIC_KEY
		&& !Arrays.equals(requirements.getByteArray(PARAM_PUBLIC_KEY),
		leafCertificate.getPublicKey().getEncoded())) {
		debugVerboseLog("Provided public key does not match leaf certificate public key.");
		return false;
		return true;
		}

		// Verify challenge matches provided challenge.
		if (localBindingType == TYPE_CHALLENGE
		&& !Arrays.equals(requirements.getByteArray(PARAM_CHALLENGE),
		attestationAttributes.getAttestationChallenge().toByteArray())) {
		debugVerboseLog("Provided challenge does not match leaf certificate challenge.");
		return false;
		private boolean checkPublicKey(
		@NonNull Certificate certificate, @NonNull byte[] expectedPublicKey) {
		final byte[] publicKey = certificate.getPublicKey().getEncoded();
		return Arrays.equals(publicKey, expectedPublicKey);
		}

		return true;
		private boolean checkAttestationChallenge(
		@NonNull AndroidKeystoreAttestationVerificationAttributes attestationAttributes,
		@NonNull byte[] expectedChallenge) {
		final byte[] challenge = attestationAttributes.getAttestationChallenge().toByteArray();
		return Arrays.equals(challenge, expectedChallenge);
		}

		/**
		@@ -507,4 +551,16 @@ class AttestationVerificationPeerDeviceVerifier {
		R.string.vendor_required_attestation_revocation_list_url);
		}
		}

		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);
		}
		}
		}