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