ConfigUpdateInstallReceiver.java revision 0967a9edfc29fe601c9242648b93448d710b7a97
1/* 2 * Copyright (C) 2012 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 17package com.android.server.updates; 18 19import android.content.BroadcastReceiver; 20import android.content.ContentResolver; 21import android.content.Context; 22import android.content.Intent; 23import android.provider.Settings; 24import android.os.FileUtils; 25import android.util.Base64; 26import android.util.EventLog; 27import android.util.Slog; 28 29import com.android.server.EventLogTags; 30 31import java.io.ByteArrayInputStream; 32import java.io.File; 33import java.io.FileNotFoundException; 34import java.io.FileOutputStream; 35import java.io.InputStream; 36import java.io.IOException; 37import java.security.cert.Certificate; 38import java.security.cert.CertificateException; 39import java.security.cert.CertificateFactory; 40import java.security.cert.X509Certificate; 41import java.security.MessageDigest; 42import java.security.NoSuchAlgorithmException; 43import java.security.Signature; 44import java.security.SignatureException; 45 46import libcore.io.IoUtils; 47 48public class ConfigUpdateInstallReceiver extends BroadcastReceiver { 49 50 private static final String TAG = "ConfigUpdateInstallReceiver"; 51 52 private static final String EXTRA_CONTENT_PATH = "CONTENT_PATH"; 53 private static final String EXTRA_REQUIRED_HASH = "REQUIRED_HASH"; 54 private static final String EXTRA_SIGNATURE = "SIGNATURE"; 55 private static final String EXTRA_VERSION_NUMBER = "VERSION"; 56 57 private static final String UPDATE_CERTIFICATE_KEY = "config_update_certificate"; 58 59 private final File updateDir; 60 private final File updateContent; 61 private final File updateVersion; 62 63 public ConfigUpdateInstallReceiver(String updateDir, String updateContentPath, 64 String updateMetadataPath, String updateVersionPath) { 65 this.updateDir = new File(updateDir); 66 this.updateContent = new File(updateDir, updateContentPath); 67 File updateMetadataDir = new File(updateDir, updateMetadataPath); 68 this.updateVersion = new File(updateMetadataDir, updateVersionPath); 69 } 70 71 @Override 72 public void onReceive(final Context context, final Intent intent) { 73 new Thread() { 74 @Override 75 public void run() { 76 try { 77 // get the certificate from Settings.Secure 78 X509Certificate cert = getCert(context.getContentResolver()); 79 // get the content path from the extras 80 String altContent = getAltContent(intent); 81 // get the version from the extras 82 int altVersion = getVersionFromIntent(intent); 83 // get the previous value from the extras 84 String altRequiredHash = getRequiredHashFromIntent(intent); 85 // get the signature from the extras 86 String altSig = getSignatureFromIntent(intent); 87 // get the version currently being used 88 int currentVersion = getCurrentVersion(); 89 // get the hash of the currently used value 90 String currentHash = getCurrentHash(getCurrentContent()); 91 if (!verifyVersion(currentVersion, altVersion)) { 92 Slog.i(TAG, "Not installing, new version is <= current version"); 93 } else if (!verifyPreviousHash(currentHash, altRequiredHash)) { 94 EventLog.writeEvent(EventLogTags.CONFIG_INSTALL_FAILED, 95 "Current hash did not match required value"); 96 } else if (!verifySignature(altContent, altVersion, altRequiredHash, altSig, 97 cert)) { 98 EventLog.writeEvent(EventLogTags.CONFIG_INSTALL_FAILED, 99 "Signature did not verify"); 100 } else { 101 // install the new content 102 Slog.i(TAG, "Found new update, installing..."); 103 install(altContent, altVersion); 104 Slog.i(TAG, "Installation successful"); 105 } 106 } catch (Exception e) { 107 Slog.e(TAG, "Could not update content!", e); 108 // keep the error message <= 100 chars 109 String errMsg = e.toString(); 110 if (errMsg.length() > 100) { 111 errMsg = errMsg.substring(0, 99); 112 } 113 EventLog.writeEvent(EventLogTags.CONFIG_INSTALL_FAILED, errMsg); 114 } 115 } 116 }.start(); 117 } 118 119 private X509Certificate getCert(ContentResolver cr) { 120 // get the cert from settings 121 String cert = Settings.Secure.getString(cr, UPDATE_CERTIFICATE_KEY); 122 // convert it into a real certificate 123 try { 124 byte[] derCert = Base64.decode(cert.getBytes(), Base64.DEFAULT); 125 InputStream istream = new ByteArrayInputStream(derCert); 126 CertificateFactory cf = CertificateFactory.getInstance("X.509"); 127 return (X509Certificate) cf.generateCertificate(istream); 128 } catch (CertificateException e) { 129 throw new IllegalStateException("Got malformed certificate from settings, ignoring", e); 130 } 131 } 132 133 private String getContentFromIntent(Intent i) { 134 String extraValue = i.getStringExtra(EXTRA_CONTENT_PATH); 135 if (extraValue == null) { 136 throw new IllegalStateException("Missing required content path, ignoring."); 137 } 138 return extraValue; 139 } 140 141 private int getVersionFromIntent(Intent i) throws NumberFormatException { 142 String extraValue = i.getStringExtra(EXTRA_VERSION_NUMBER); 143 if (extraValue == null) { 144 throw new IllegalStateException("Missing required version number, ignoring."); 145 } 146 return Integer.parseInt(extraValue.trim()); 147 } 148 149 private String getRequiredHashFromIntent(Intent i) { 150 String extraValue = i.getStringExtra(EXTRA_REQUIRED_HASH); 151 if (extraValue == null) { 152 throw new IllegalStateException("Missing required previous hash, ignoring."); 153 } 154 return extraValue.trim(); 155 } 156 157 private String getSignatureFromIntent(Intent i) { 158 String extraValue = i.getStringExtra(EXTRA_SIGNATURE); 159 if (extraValue == null) { 160 throw new IllegalStateException("Missing required signature, ignoring."); 161 } 162 return extraValue.trim(); 163 } 164 165 private int getCurrentVersion() throws NumberFormatException { 166 try { 167 String strVersion = IoUtils.readFileAsString(updateVersion.getCanonicalPath()).trim(); 168 return Integer.parseInt(strVersion); 169 } catch (IOException e) { 170 Slog.i(TAG, "Couldn't find current metadata, assuming first update", e); 171 return 0; 172 } 173 } 174 175 private String getAltContent(Intent i) throws IOException { 176 String contents = IoUtils.readFileAsString(getContentFromIntent(i)); 177 return contents.trim(); 178 } 179 180 private String getCurrentContent() { 181 try { 182 return IoUtils.readFileAsString(updateContent.getCanonicalPath()).trim(); 183 } catch (IOException e) { 184 Slog.i(TAG, "Failed to read current content, assuming first update!", e); 185 return null; 186 } 187 } 188 189 private static String getCurrentHash(String content) { 190 if (content == null) { 191 return "0"; 192 } 193 try { 194 MessageDigest dgst = MessageDigest.getInstance("SHA512"); 195 byte[] encoded = content.getBytes(); 196 byte[] fingerprint = dgst.digest(encoded); 197 return IntegralToString.bytesToHexString(fingerprint, false); 198 } catch (NoSuchAlgorithmException e) { 199 throw new AssertionError(e); 200 } 201 } 202 203 private boolean verifyVersion(int current, int alternative) { 204 return (current < alternative); 205 } 206 207 private boolean verifyPreviousHash(String current, String required) { 208 // this is an optional value- if the required field is NONE then we ignore it 209 if (required.equals("NONE")) { 210 return true; 211 } 212 // otherwise, verify that we match correctly 213 return current.equals(required); 214 } 215 216 private boolean verifySignature(String content, int version, String requiredPrevious, 217 String signature, X509Certificate cert) throws Exception { 218 Signature signer = Signature.getInstance("SHA512withRSA"); 219 signer.initVerify(cert); 220 signer.update(content.getBytes()); 221 signer.update(Long.toString(version).getBytes()); 222 signer.update(requiredPrevious.getBytes()); 223 return signer.verify(Base64.decode(signature.getBytes(), Base64.DEFAULT)); 224 } 225 226 private void writeUpdate(File dir, File file, String content) { 227 FileOutputStream out = null; 228 File tmp = null; 229 try { 230 // create the temporary file 231 tmp = File.createTempFile("journal", "", dir); 232 // create the parents for the destination file 233 File parent = file.getParentFile(); 234 parent.mkdirs(); 235 // check that they were created correctly 236 if (!parent.exists()) { 237 throw new IOException("Failed to create directory " + parent.getCanonicalPath()); 238 } 239 // mark tmp -rw-r--r-- 240 tmp.setReadable(true, false); 241 // write to it 242 out = new FileOutputStream(tmp); 243 out.write(content.getBytes()); 244 // sync to disk 245 out.getFD().sync(); 246 // atomic rename 247 if (!tmp.renameTo(file)) { 248 throw new IOException("Failed to atomically rename " + file.getCanonicalPath()); 249 } 250 } catch (IOException e) { 251 Slog.e(TAG, "Failed to write update", e); 252 } finally { 253 if (tmp != null) { 254 tmp.delete(); 255 } 256 IoUtils.closeQuietly(out); 257 } 258 } 259 260 private void install(String content, int version) { 261 writeUpdate(updateDir, updateContent, content); 262 writeUpdate(updateDir, updateVersion, Long.toString(version)); 263 } 264} 265