| /* |
| * Copyright (C) 2017 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.security.keystore; |
| |
| import android.Manifest; |
| import android.annotation.NonNull; |
| import android.annotation.RequiresPermission; |
| import android.annotation.SystemApi; |
| import android.annotation.TestApi; |
| import android.content.Context; |
| import android.content.res.Resources; |
| import android.os.Build; |
| import android.security.KeyStore; |
| import android.security.keymaster.KeymasterArguments; |
| import android.security.keymaster.KeymasterCertificateChain; |
| import android.security.keymaster.KeymasterDefs; |
| import android.telephony.TelephonyManager; |
| import android.text.TextUtils; |
| import android.util.ArraySet; |
| |
| import java.io.ByteArrayInputStream; |
| import java.io.ByteArrayOutputStream; |
| import java.nio.charset.StandardCharsets; |
| import java.security.cert.CertificateFactory; |
| import java.security.cert.X509Certificate; |
| import java.util.Collection; |
| import java.util.Set; |
| |
| /** |
| * Utilities for attesting the device's hardware identifiers. |
| * |
| * @hide |
| */ |
| @SystemApi |
| @TestApi |
| public abstract class AttestationUtils { |
| private AttestationUtils() { |
| } |
| |
| /** |
| * Specifies that the device should attest its serial number. For use with |
| * {@link #attestDeviceIds}. |
| * |
| * @see #attestDeviceIds |
| */ |
| public static final int ID_TYPE_SERIAL = 1; |
| |
| /** |
| * Specifies that the device should attest its IMEIs. For use with {@link #attestDeviceIds}. |
| * |
| * @see #attestDeviceIds |
| */ |
| public static final int ID_TYPE_IMEI = 2; |
| |
| /** |
| * Specifies that the device should attest its MEIDs. For use with {@link #attestDeviceIds}. |
| * |
| * @see #attestDeviceIds |
| */ |
| public static final int ID_TYPE_MEID = 3; |
| |
| /** |
| * Specifies that the device should sign the attestation record using its device-unique |
| * attestation certificate. For use with {@link #attestDeviceIds}. |
| * |
| * @see #attestDeviceIds |
| */ |
| public static final int USE_INDIVIDUAL_ATTESTATION = 4; |
| |
| /** |
| * Creates an array of X509Certificates from the provided KeymasterCertificateChain. |
| * |
| * @hide Only called by the DevicePolicyManager. |
| */ |
| @NonNull public static X509Certificate[] parseCertificateChain( |
| final KeymasterCertificateChain kmChain) throws |
| KeyAttestationException { |
| // Extract certificate chain. |
| final Collection<byte[]> rawChain = kmChain.getCertificates(); |
| if (rawChain.size() < 2) { |
| throw new KeyAttestationException("Attestation certificate chain contained " |
| + rawChain.size() + " entries. At least two are required."); |
| } |
| final ByteArrayOutputStream concatenatedRawChain = new ByteArrayOutputStream(); |
| try { |
| for (final byte[] cert : rawChain) { |
| concatenatedRawChain.write(cert); |
| } |
| return CertificateFactory.getInstance("X.509").generateCertificates( |
| new ByteArrayInputStream(concatenatedRawChain.toByteArray())) |
| .toArray(new X509Certificate[0]); |
| } catch (Exception e) { |
| throw new KeyAttestationException("Unable to construct certificate chain", e); |
| } |
| } |
| |
| @NonNull private static KeymasterArguments prepareAttestationArgumentsForDeviceId( |
| Context context, @NonNull int[] idTypes, @NonNull byte[] attestationChallenge) throws |
| DeviceIdAttestationException { |
| // Verify that device ID attestation types are provided. |
| if (idTypes == null) { |
| throw new NullPointerException("Missing id types"); |
| } |
| |
| return prepareAttestationArguments(context, idTypes, attestationChallenge); |
| } |
| |
| /** |
| * Prepares Keymaster Arguments with attestation data. |
| * @hide should only be used by KeyChain. |
| */ |
| @NonNull public static KeymasterArguments prepareAttestationArguments(Context context, |
| @NonNull int[] idTypes, @NonNull byte[] attestationChallenge) throws |
| DeviceIdAttestationException { |
| return prepareAttestationArguments(context, idTypes,attestationChallenge, Build.BRAND); |
| } |
| |
| /** |
| * Prepares Keymaster Arguments with attestation data for misprovisioned Pixel 2 device. |
| * See http://go/keyAttestationFailure and http://b/69471841 for more info. |
| * @hide should only be used by KeyChain. |
| */ |
| @NonNull public static KeymasterArguments prepareAttestationArgumentsIfMisprovisioned( |
| Context context, @NonNull int[] idTypes, @NonNull byte[] attestationChallenge) throws |
| DeviceIdAttestationException { |
| Resources resources = context.getResources(); |
| String misprovisionedBrand = resources.getString( |
| com.android.internal.R.string.config_misprovisionedBrandValue); |
| if (!TextUtils.isEmpty(misprovisionedBrand) && !isPotentiallyMisprovisionedDevice(context)){ |
| return null; |
| } |
| return prepareAttestationArguments( |
| context, idTypes, attestationChallenge, misprovisionedBrand); |
| } |
| |
| @NonNull private static boolean isPotentiallyMisprovisionedDevice(Context context) { |
| Resources resources = context.getResources(); |
| String misprovisionedModel = resources.getString( |
| com.android.internal.R.string.config_misprovisionedDeviceModel); |
| return (Build.MODEL.equals(misprovisionedModel)); |
| } |
| |
| @NonNull private static KeymasterArguments prepareAttestationArguments(Context context, |
| @NonNull int[] idTypes, @NonNull byte[] attestationChallenge, String brand) throws |
| DeviceIdAttestationException { |
| // Check method arguments, retrieve requested device IDs and prepare attestation arguments. |
| if (attestationChallenge == null) { |
| throw new NullPointerException("Missing attestation challenge"); |
| } |
| final KeymasterArguments attestArgs = new KeymasterArguments(); |
| attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_CHALLENGE, attestationChallenge); |
| // Return early if the caller did not request any device identifiers to be included in the |
| // attestation record. |
| if (idTypes == null) { |
| return attestArgs; |
| } |
| final Set<Integer> idTypesSet = new ArraySet<>(idTypes.length); |
| for (int idType : idTypes) { |
| idTypesSet.add(idType); |
| } |
| TelephonyManager telephonyService = null; |
| if (idTypesSet.contains(ID_TYPE_IMEI) || idTypesSet.contains(ID_TYPE_MEID)) { |
| telephonyService = (TelephonyManager) context.getSystemService( |
| Context.TELEPHONY_SERVICE); |
| if (telephonyService == null) { |
| throw new DeviceIdAttestationException("Unable to access telephony service"); |
| } |
| } |
| for (final Integer idType : idTypesSet) { |
| switch (idType) { |
| case ID_TYPE_SERIAL: |
| attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_SERIAL, |
| Build.getSerial().getBytes(StandardCharsets.UTF_8)); |
| break; |
| case ID_TYPE_IMEI: { |
| final String imei = telephonyService.getImei(0); |
| if (imei == null) { |
| throw new DeviceIdAttestationException("Unable to retrieve IMEI"); |
| } |
| attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_IMEI, |
| imei.getBytes(StandardCharsets.UTF_8)); |
| break; |
| } |
| case ID_TYPE_MEID: { |
| final String meid = telephonyService.getMeid(0); |
| if (meid == null) { |
| throw new DeviceIdAttestationException("Unable to retrieve MEID"); |
| } |
| attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_MEID, |
| meid.getBytes(StandardCharsets.UTF_8)); |
| break; |
| } |
| case USE_INDIVIDUAL_ATTESTATION: { |
| attestArgs.addBoolean(KeymasterDefs.KM_TAG_DEVICE_UNIQUE_ATTESTATION); |
| break; |
| } |
| default: |
| throw new IllegalArgumentException("Unknown device ID type " + idType); |
| } |
| } |
| attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_BRAND, |
| brand.getBytes(StandardCharsets.UTF_8)); |
| attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_DEVICE, |
| Build.DEVICE.getBytes(StandardCharsets.UTF_8)); |
| attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_PRODUCT, |
| Build.PRODUCT.getBytes(StandardCharsets.UTF_8)); |
| attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_MANUFACTURER, |
| Build.MANUFACTURER.getBytes(StandardCharsets.UTF_8)); |
| attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_MODEL, |
| Build.MODEL.getBytes(StandardCharsets.UTF_8)); |
| return attestArgs; |
| } |
| |
| /** |
| * Performs attestation of the device's identifiers. This method returns a certificate chain |
| * whose first element contains the requested device identifiers in an extension. The device's |
| * manufacturer, model, brand, device and product are always also included in the attestation. |
| * If the device supports attestation in secure hardware, the chain will be rooted at a |
| * trustworthy CA key. Otherwise, the chain will be rooted at an untrusted certificate. See |
| * <a href="https://developer.android.com/training/articles/security-key-attestation.html"> |
| * Key Attestation</a> for the format of the certificate extension. |
| * <p> |
| * Attestation will only be successful when all of the following are true: |
| * 1) The device has been set up to support device identifier attestation at the factory. |
| * 2) The user has not permanently disabled device identifier attestation. |
| * 3) You have permission to access the device identifiers you are requesting attestation for. |
| * <p> |
| * For privacy reasons, you cannot distinguish between (1) and (2). If attestation is |
| * unsuccessful, the device may not support it in general or the user may have permanently |
| * disabled it. |
| * |
| * @param context the context to use for retrieving device identifiers. |
| * @param idTypes the types of device identifiers to attest. |
| * @param attestationChallenge a blob to include in the certificate alongside the device |
| * identifiers. |
| * |
| * @return a certificate chain containing the requested device identifiers in the first element |
| * |
| * @exception SecurityException if you are not permitted to obtain an attestation of the |
| * device's identifiers. |
| * @exception DeviceIdAttestationException if the attestation operation fails. |
| */ |
| @RequiresPermission(Manifest.permission.READ_PRIVILEGED_PHONE_STATE) |
| @NonNull public static X509Certificate[] attestDeviceIds(Context context, |
| @NonNull int[] idTypes, @NonNull byte[] attestationChallenge) throws |
| DeviceIdAttestationException { |
| final KeymasterArguments attestArgs = prepareAttestationArgumentsForDeviceId( |
| context, idTypes, attestationChallenge); |
| |
| // Perform attestation. |
| final KeymasterCertificateChain outChain = new KeymasterCertificateChain(); |
| final int errorCode = KeyStore.getInstance().attestDeviceIds(attestArgs, outChain); |
| if (errorCode != KeyStore.NO_ERROR) { |
| throw new DeviceIdAttestationException("Unable to perform attestation", |
| KeyStore.getKeyStoreException(errorCode)); |
| } |
| |
| try { |
| return parseCertificateChain(outChain); |
| } catch (KeyAttestationException e) { |
| throw new DeviceIdAttestationException(e.getMessage(), e); |
| } |
| } |
| |
| /** |
| * Returns true if the attestation chain provided is a valid key attestation chain. |
| * @hide |
| */ |
| public static boolean isChainValid(KeymasterCertificateChain chain) { |
| return chain != null && chain.getCertificates().size() >= 2; |
| } |
| } |