Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2017 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package android.security.keystore; |
| 18 | |
| 19 | import android.Manifest; |
| 20 | import android.annotation.NonNull; |
| 21 | import android.annotation.RequiresPermission; |
| 22 | import android.annotation.SystemApi; |
| 23 | import android.annotation.TestApi; |
| 24 | import android.content.Context; |
| 25 | import android.os.Build; |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 26 | import android.security.KeyStore; |
| 27 | import android.security.KeyStoreException; |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 28 | import android.security.keymaster.KeymasterArguments; |
| 29 | import android.security.keymaster.KeymasterCertificateChain; |
| 30 | import android.security.keymaster.KeymasterDefs; |
| 31 | import android.telephony.TelephonyManager; |
| 32 | import android.util.ArraySet; |
| 33 | |
| 34 | import java.io.ByteArrayInputStream; |
| 35 | import java.io.ByteArrayOutputStream; |
| 36 | import java.nio.charset.StandardCharsets; |
| 37 | import java.security.cert.CertificateFactory; |
| 38 | import java.security.cert.X509Certificate; |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 39 | import java.util.Collection; |
| 40 | import java.util.Set; |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 41 | |
| 42 | /** |
| 43 | * Utilities for attesting the device's hardware identifiers. |
| 44 | * |
| 45 | * @hide |
| 46 | */ |
| 47 | @SystemApi |
| 48 | @TestApi |
| 49 | public abstract class AttestationUtils { |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 50 | private AttestationUtils() { |
| 51 | } |
| 52 | |
| 53 | /** |
| 54 | * Specifies that the device should attest its serial number. For use with |
| 55 | * {@link #attestDeviceIds}. |
| 56 | * |
| 57 | * @see #attestDeviceIds |
| 58 | */ |
| 59 | public static final int ID_TYPE_SERIAL = 1; |
| 60 | |
| 61 | /** |
| 62 | * Specifies that the device should attest its IMEIs. For use with {@link #attestDeviceIds}. |
| 63 | * |
| 64 | * @see #attestDeviceIds |
| 65 | */ |
| 66 | public static final int ID_TYPE_IMEI = 2; |
| 67 | |
| 68 | /** |
| 69 | * Specifies that the device should attest its MEIDs. For use with {@link #attestDeviceIds}. |
| 70 | * |
| 71 | * @see #attestDeviceIds |
| 72 | */ |
| 73 | public static final int ID_TYPE_MEID = 3; |
| 74 | |
| 75 | /** |
Eran Messeri | a173064 | 2017-12-11 17:48:47 +0000 | [diff] [blame] | 76 | * Creates an array of X509Certificates from the provided KeymasterCertificateChain. |
| 77 | * |
| 78 | * @hide Only called by the DevicePolicyManager. |
| 79 | */ |
| 80 | @NonNull public static X509Certificate[] parseCertificateChain( |
| 81 | final KeymasterCertificateChain kmChain) throws |
| 82 | KeyAttestationException { |
| 83 | // Extract certificate chain. |
| 84 | final Collection<byte[]> rawChain = kmChain.getCertificates(); |
| 85 | if (rawChain.size() < 2) { |
| 86 | throw new KeyAttestationException("Attestation certificate chain contained " |
| 87 | + rawChain.size() + " entries. At least two are required."); |
| 88 | } |
| 89 | final ByteArrayOutputStream concatenatedRawChain = new ByteArrayOutputStream(); |
| 90 | try { |
| 91 | for (final byte[] cert : rawChain) { |
| 92 | concatenatedRawChain.write(cert); |
| 93 | } |
| 94 | return CertificateFactory.getInstance("X.509").generateCertificates( |
| 95 | new ByteArrayInputStream(concatenatedRawChain.toByteArray())) |
| 96 | .toArray(new X509Certificate[0]); |
| 97 | } catch (Exception e) { |
| 98 | throw new KeyAttestationException("Unable to construct certificate chain", e); |
| 99 | } |
| 100 | } |
| 101 | |
Eran Messeri | 94d5676 | 2017-12-21 20:50:54 +0000 | [diff] [blame] | 102 | @NonNull private static KeymasterArguments prepareAttestationArgumentsForDeviceId( |
| 103 | Context context, @NonNull int[] idTypes, @NonNull byte[] attestationChallenge) throws |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 104 | DeviceIdAttestationException { |
Eran Messeri | 94d5676 | 2017-12-21 20:50:54 +0000 | [diff] [blame] | 105 | // Verify that device ID attestation types are provided. |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 106 | if (idTypes == null) { |
| 107 | throw new NullPointerException("Missing id types"); |
| 108 | } |
Eran Messeri | 94d5676 | 2017-12-21 20:50:54 +0000 | [diff] [blame] | 109 | |
| 110 | return prepareAttestationArguments(context, idTypes, attestationChallenge); |
| 111 | } |
| 112 | |
| 113 | /** |
| 114 | * Prepares Keymaster Arguments with attestation data. |
| 115 | * @hide should only be used by KeyChain. |
| 116 | */ |
| 117 | @NonNull public static KeymasterArguments prepareAttestationArguments(Context context, |
| 118 | @NonNull int[] idTypes, @NonNull byte[] attestationChallenge) throws |
| 119 | DeviceIdAttestationException { |
| 120 | // Check method arguments, retrieve requested device IDs and prepare attestation arguments. |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 121 | if (attestationChallenge == null) { |
| 122 | throw new NullPointerException("Missing attestation challenge"); |
| 123 | } |
| 124 | final KeymasterArguments attestArgs = new KeymasterArguments(); |
| 125 | attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_CHALLENGE, attestationChallenge); |
Eran Messeri | 94d5676 | 2017-12-21 20:50:54 +0000 | [diff] [blame] | 126 | // Return early if the caller did not request any device identifiers to be included in the |
| 127 | // attestation record. |
| 128 | if (idTypes == null) { |
| 129 | return attestArgs; |
| 130 | } |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 131 | final Set<Integer> idTypesSet = new ArraySet<>(idTypes.length); |
| 132 | for (int idType : idTypes) { |
| 133 | idTypesSet.add(idType); |
| 134 | } |
| 135 | TelephonyManager telephonyService = null; |
| 136 | if (idTypesSet.contains(ID_TYPE_IMEI) || idTypesSet.contains(ID_TYPE_MEID)) { |
| 137 | telephonyService = (TelephonyManager) context.getSystemService( |
| 138 | Context.TELEPHONY_SERVICE); |
| 139 | if (telephonyService == null) { |
| 140 | throw new DeviceIdAttestationException("Unable to access telephony service"); |
| 141 | } |
| 142 | } |
| 143 | for (final Integer idType : idTypesSet) { |
| 144 | switch (idType) { |
| 145 | case ID_TYPE_SERIAL: |
| 146 | attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_SERIAL, |
| 147 | Build.getSerial().getBytes(StandardCharsets.UTF_8)); |
| 148 | break; |
| 149 | case ID_TYPE_IMEI: { |
| 150 | final String imei = telephonyService.getImei(0); |
| 151 | if (imei == null) { |
| 152 | throw new DeviceIdAttestationException("Unable to retrieve IMEI"); |
| 153 | } |
| 154 | attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_IMEI, |
| 155 | imei.getBytes(StandardCharsets.UTF_8)); |
| 156 | break; |
| 157 | } |
| 158 | case ID_TYPE_MEID: { |
Eran Messeri | 52dcedc | 2018-04-12 14:06:59 +0100 | [diff] [blame] | 159 | final String meid = telephonyService.getMeid(0); |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 160 | if (meid == null) { |
| 161 | throw new DeviceIdAttestationException("Unable to retrieve MEID"); |
| 162 | } |
| 163 | attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_MEID, |
| 164 | meid.getBytes(StandardCharsets.UTF_8)); |
| 165 | break; |
| 166 | } |
| 167 | default: |
| 168 | throw new IllegalArgumentException("Unknown device ID type " + idType); |
| 169 | } |
| 170 | } |
| 171 | attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_BRAND, |
| 172 | Build.BRAND.getBytes(StandardCharsets.UTF_8)); |
| 173 | attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_DEVICE, |
| 174 | Build.DEVICE.getBytes(StandardCharsets.UTF_8)); |
| 175 | attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_PRODUCT, |
| 176 | Build.PRODUCT.getBytes(StandardCharsets.UTF_8)); |
Bartosz Fabianowski | ad60c06 | 2017-03-20 13:59:51 +0100 | [diff] [blame] | 177 | attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_MANUFACTURER, |
| 178 | Build.MANUFACTURER.getBytes(StandardCharsets.UTF_8)); |
| 179 | attestArgs.addBytes(KeymasterDefs.KM_TAG_ATTESTATION_ID_MODEL, |
| 180 | Build.MODEL.getBytes(StandardCharsets.UTF_8)); |
Eran Messeri | 94d5676 | 2017-12-21 20:50:54 +0000 | [diff] [blame] | 181 | return attestArgs; |
| 182 | } |
| 183 | |
| 184 | /** |
| 185 | * Performs attestation of the device's identifiers. This method returns a certificate chain |
| 186 | * whose first element contains the requested device identifiers in an extension. The device's |
| 187 | * manufacturer, model, brand, device and product are always also included in the attestation. |
| 188 | * If the device supports attestation in secure hardware, the chain will be rooted at a |
| 189 | * trustworthy CA key. Otherwise, the chain will be rooted at an untrusted certificate. See |
| 190 | * <a href="https://developer.android.com/training/articles/security-key-attestation.html"> |
| 191 | * Key Attestation</a> for the format of the certificate extension. |
| 192 | * <p> |
| 193 | * Attestation will only be successful when all of the following are true: |
| 194 | * 1) The device has been set up to support device identifier attestation at the factory. |
| 195 | * 2) The user has not permanently disabled device identifier attestation. |
| 196 | * 3) You have permission to access the device identifiers you are requesting attestation for. |
| 197 | * <p> |
| 198 | * For privacy reasons, you cannot distinguish between (1) and (2). If attestation is |
| 199 | * unsuccessful, the device may not support it in general or the user may have permanently |
| 200 | * disabled it. |
| 201 | * |
| 202 | * @param context the context to use for retrieving device identifiers. |
| 203 | * @param idTypes the types of device identifiers to attest. |
| 204 | * @param attestationChallenge a blob to include in the certificate alongside the device |
| 205 | * identifiers. |
| 206 | * |
| 207 | * @return a certificate chain containing the requested device identifiers in the first element |
| 208 | * |
| 209 | * @exception SecurityException if you are not permitted to obtain an attestation of the |
| 210 | * device's identifiers. |
| 211 | * @exception DeviceIdAttestationException if the attestation operation fails. |
| 212 | */ |
| 213 | @RequiresPermission(Manifest.permission.READ_PRIVILEGED_PHONE_STATE) |
| 214 | @NonNull public static X509Certificate[] attestDeviceIds(Context context, |
| 215 | @NonNull int[] idTypes, @NonNull byte[] attestationChallenge) throws |
| 216 | DeviceIdAttestationException { |
| 217 | final KeymasterArguments attestArgs = prepareAttestationArgumentsForDeviceId( |
| 218 | context, idTypes, attestationChallenge); |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 219 | |
Bartosz Fabianowski | 237f4b36 | 2017-04-24 13:57:46 +0200 | [diff] [blame] | 220 | // Perform attestation. |
| 221 | final KeymasterCertificateChain outChain = new KeymasterCertificateChain(); |
| 222 | final int errorCode = KeyStore.getInstance().attestDeviceIds(attestArgs, outChain); |
| 223 | if (errorCode != KeyStore.NO_ERROR) { |
| 224 | throw new DeviceIdAttestationException("Unable to perform attestation", |
| 225 | KeyStore.getKeyStoreException(errorCode)); |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 226 | } |
Bartosz Fabianowski | 237f4b36 | 2017-04-24 13:57:46 +0200 | [diff] [blame] | 227 | |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 228 | try { |
Eran Messeri | a173064 | 2017-12-11 17:48:47 +0000 | [diff] [blame] | 229 | return parseCertificateChain(outChain); |
| 230 | } catch (KeyAttestationException e) { |
| 231 | throw new DeviceIdAttestationException(e.getMessage(), e); |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 232 | } |
| 233 | } |
Eran Messeri | a173064 | 2017-12-11 17:48:47 +0000 | [diff] [blame] | 234 | |
| 235 | /** |
| 236 | * Returns true if the attestation chain provided is a valid key attestation chain. |
| 237 | * @hide |
| 238 | */ |
| 239 | public static boolean isChainValid(KeymasterCertificateChain chain) { |
| 240 | return chain != null && chain.getCertificates().size() >= 2; |
| 241 | } |
Bartosz Fabianowski | 92e8cfd | 2017-01-23 17:40:47 +0100 | [diff] [blame] | 242 | } |