core/java/android/os/RecoverySystem.java - platform/frameworks/base - Git at Google

 /*
  * Copyright (C) 2010 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.os;

 import java.io.ByteArrayInputStream;
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.FileWriter;
 import java.io.IOException;
 import java.io.RandomAccessFile;
 import java.security.GeneralSecurityException;
 import java.security.PublicKey;
 import java.security.Signature;
 import java.security.SignatureException;
 import java.security.cert.Certificate;
 import java.security.cert.CertificateFactory;
 import java.security.cert.X509Certificate;
 import java.util.Collection;
 import java.util.Enumeration;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipFile;

 import android.content.Context;
 import android.util.Log;

 import org.apache.harmony.security.asn1.BerInputStream;
 import org.apache.harmony.security.pkcs7.ContentInfo;
 import org.apache.harmony.security.pkcs7.SignedData;
 import org.apache.harmony.security.pkcs7.SignerInfo;
 import org.apache.harmony.security.provider.cert.X509CertImpl;

 /**
  * RecoverySystem contains methods for interacting with the Android
  * recovery system (the separate partition that can be used to install
  * system updates, wipe user data, etc.)
  */
 public class RecoverySystem {
     private static final String TAG = "RecoverySystem";

     /**
      * Default location of zip file containing public keys (X509
      * certs) authorized to sign OTA updates.
      */
     private static final File DEFAULT_KEYSTORE =
         new File("/system/etc/security/otacerts.zip");

     /** Send progress to listeners no more often than this (in ms). */
     private static final long PUBLISH_PROGRESS_INTERVAL_MS = 500;

     /** Used to communicate with recovery.  See bootable/recovery/recovery.c. */
     private static File RECOVERY_DIR = new File("/cache/recovery");
     private static File COMMAND_FILE = new File(RECOVERY_DIR, "command");
     private static File LOG_FILE = new File(RECOVERY_DIR, "log");

     // Length limits for reading files.
     private static int LOG_FILE_MAX_LENGTH = 64 * 1024;

     /**
      * Interface definition for a callback to be invoked regularly as
      * verification proceeds.
      */
     public interface ProgressListener {
         /**
          * Called periodically as the verification progresses.
          *
          * @param progress  the approximate percentage of the
          *        verification that has been completed, ranging from 0
          *        to 100 (inclusive).
          */
         public void onProgress(int progress);
     }

     /** @return the set of certs that can be used to sign an OTA package. */
     private static HashSet<Certificate> getTrustedCerts(File keystore)
         throws IOException, GeneralSecurityException {
         HashSet<Certificate> trusted = new HashSet<Certificate>();
         if (keystore == null) {
             keystore = DEFAULT_KEYSTORE;
         }
         ZipFile zip = new ZipFile(keystore);
         try {
             CertificateFactory cf = CertificateFactory.getInstance("X.509");
             Enumeration<? extends ZipEntry> entries = zip.entries();
             while (entries.hasMoreElements()) {
                 ZipEntry entry = entries.nextElement();
                 trusted.add(cf.generateCertificate(zip.getInputStream(entry)));
             }
         } finally {
             zip.close();
         }
         return trusted;
     }

     /**
      * Verify the cryptographic signature of a system update package
      * before installing it.  Note that the package is also verified
      * separately by the installer once the device is rebooted into
      * the recovery system.  This function will return only if the
      * package was successfully verified; otherwise it will throw an
      * exception.
      *
      * Verification of a package can take significant time, so this
      * function should not be called from a UI thread.  Interrupting
      * the thread while this function is in progress will result in a
      * SecurityException being thrown (and the thread's interrupt flag
      * will be cleared).
      *
      * @param packageFile  the package to be verified
      * @param listener     an object to receive periodic progress
      * updates as verification proceeds.  May be null.
      * @param deviceCertsZipFile  the zip file of certificates whose
      * public keys we will accept.  Verification succeeds if the
      * package is signed by the private key corresponding to any
      * public key in this file.  May be null to use the system default
      * file (currently "/system/etc/security/otacerts.zip").
      *
      * @throws IOException if there were any errors reading the
      * package or certs files.
      * @throws GeneralSecurityException if verification failed
      */
     public static void verifyPackage(File packageFile,
                                      ProgressListener listener,
                                      File deviceCertsZipFile)
         throws IOException, GeneralSecurityException {
         long fileLen = packageFile.length();

         RandomAccessFile raf = new RandomAccessFile(packageFile, "r");
         try {
             int lastPercent = 0;
             long lastPublishTime = System.currentTimeMillis();
             if (listener != null) {
                 listener.onProgress(lastPercent);
             }

             raf.seek(fileLen - 6);
             byte[] footer = new byte[6];
             raf.readFully(footer);

             if (footer[2] != (byte)0xff || footer[3] != (byte)0xff) {
                 throw new SignatureException("no signature in file (no footer)");
             }

             int commentSize = (footer[4] & 0xff) | ((footer[5] & 0xff) << 8);
             int signatureStart = (footer[0] & 0xff) | ((footer[1] & 0xff) << 8);
             Log.v(TAG, String.format("comment size %d; signature start %d",
                                      commentSize, signatureStart));

             byte[] eocd = new byte[commentSize + 22];
             raf.seek(fileLen - (commentSize + 22));
             raf.readFully(eocd);

             // Check that we have found the start of the
             // end-of-central-directory record.
             if (eocd[0] != (byte)0x50 || eocd[1] != (byte)0x4b ||
                 eocd[2] != (byte)0x05 || eocd[3] != (byte)0x06) {
                 throw new SignatureException("no signature in file (bad footer)");
             }

             for (int i = 4; i < eocd.length-3; ++i) {
                 if (eocd[i  ] == (byte)0x50 && eocd[i+1] == (byte)0x4b &&
                     eocd[i+2] == (byte)0x05 && eocd[i+3] == (byte)0x06) {
                     throw new SignatureException("EOCD marker found after start of EOCD");
                 }
             }

             // The following code is largely copied from
             // JarUtils.verifySignature().  We could just *call* that
             // method here if that function didn't read the entire
             // input (ie, the whole OTA package) into memory just to
             // compute its message digest.

             BerInputStream bis = new BerInputStream(
                 new ByteArrayInputStream(eocd, commentSize+22-signatureStart, signatureStart));
             ContentInfo info = (ContentInfo)ContentInfo.ASN1.decode(bis);
             SignedData signedData = info.getSignedData();
             if (signedData == null) {
                 throw new IOException("signedData is null");
             }
             Collection encCerts = signedData.getCertificates();
             if (encCerts.isEmpty()) {
                 throw new IOException("encCerts is empty");
             }
             // Take the first certificate from the signature (packages
             // should contain only one).
             Iterator it = encCerts.iterator();
             X509Certificate cert = null;
             if (it.hasNext()) {
                 cert = new X509CertImpl((org.apache.harmony.security.x509.Certificate)it.next());
             } else {
                 throw new SignatureException("signature contains no certificates");
             }

             List sigInfos = signedData.getSignerInfos();
             SignerInfo sigInfo;
             if (!sigInfos.isEmpty()) {
                 sigInfo = (SignerInfo)sigInfos.get(0);
             } else {
                 throw new IOException("no signer infos!");
             }

             // Check that the public key of the certificate contained
             // in the package equals one of our trusted public keys.

             HashSet<Certificate> trusted = getTrustedCerts(
                 deviceCertsZipFile == null ? DEFAULT_KEYSTORE : deviceCertsZipFile);

             PublicKey signatureKey = cert.getPublicKey();
             boolean verified = false;
             for (Certificate c : trusted) {
                 if (c.getPublicKey().equals(signatureKey)) {
                     verified = true;
                     break;
                 }
             }
             if (!verified) {
                 throw new SignatureException("signature doesn't match any trusted key");
             }

             // The signature cert matches a trusted key.  Now verify that
             // the digest in the cert matches the actual file data.

             // The verifier in recovery *only* handles SHA1withRSA
             // signatures.  SignApk.java always uses SHA1withRSA, no
             // matter what the cert says to use.  Ignore
             // cert.getSigAlgName(), and instead use whatever
             // algorithm is used by the signature (which should be
             // SHA1withRSA).

             String da = sigInfo.getdigestAlgorithm();
             String dea = sigInfo.getDigestEncryptionAlgorithm();
             String alg = null;
             if (da == null || dea == null) {
                 // fall back to the cert algorithm if the sig one
                 // doesn't look right.
                 alg = cert.getSigAlgName();
             } else {
                 alg = da + "with" + dea;
             }
             Signature sig = Signature.getInstance(alg);
             sig.initVerify(cert);

             // The signature covers all of the OTA package except the
             // archive comment and its 2-byte length.
             long toRead = fileLen - commentSize - 2;
             long soFar = 0;
             raf.seek(0);
             byte[] buffer = new byte[4096];
             boolean interrupted = false;
             while (soFar < toRead) {
                 interrupted = Thread.interrupted();
                 if (interrupted) break;
                 int size = buffer.length;
                 if (soFar + size > toRead) {
                     size = (int)(toRead - soFar);
                 }
                 int read = raf.read(buffer, 0, size);
                 sig.update(buffer, 0, read);
                 soFar += read;

                 if (listener != null) {
                     long now = System.currentTimeMillis();
                     int p = (int)(soFar * 100 / toRead);
                     if (p > lastPercent &&
                         now - lastPublishTime > PUBLISH_PROGRESS_INTERVAL_MS) {
                         lastPercent = p;
                         lastPublishTime = now;
                         listener.onProgress(lastPercent);
                     }
                 }
             }
             if (listener != null) {
                 listener.onProgress(100);
             }

             if (interrupted) {
                 throw new SignatureException("verification was interrupted");
             }

             if (!sig.verify(sigInfo.getEncryptedDigest())) {
                 throw new SignatureException("signature digest verification failed");
             }
         } finally {
             raf.close();
         }
     }

     /**
      * Reboots the device in order to install the given update
      * package.
      * Requires the {@link android.Manifest.permission#REBOOT}
      * and {@link android.Manifest.permission#ACCESS_CACHE_FILESYSTEM}
      * permissions.
      *
      * @param context      the Context to use
      * @param packageFile  the update package to install.  Currently
      * must be on the /cache or /data partitions.
      *
      * @throws IOException  if writing the recovery command file
      * fails, or if the reboot itself fails.
      */
     public static void installPackage(Context context, File packageFile)
         throws IOException {
         String filename = packageFile.getCanonicalPath();

         if (filename.startsWith("/cache/")) {
             filename = "CACHE:" + filename.substring(7);
         } else if (filename.startsWith("/data/")) {
             filename = "DATA:" + filename.substring(6);
         } else {
             throw new IllegalArgumentException(
                 "Must start with /cache or /data: " + filename);
         }
         Log.w(TAG, "!!! REBOOTING TO INSTALL " + filename + " !!!");
         String arg = "--update_package=" + filename;
         bootCommand(context, arg);
     }

     /**
      * Reboots the device and wipes the user data partition.  This is
      * sometimes called a "factory reset", which is something of a
      * misnomer because the system partition is not restored to its
      * factory state.
      * Requires the {@link android.Manifest.permission#REBOOT}
      * and {@link android.Manifest.permission#ACCESS_CACHE_FILESYSTEM}
      * permissions.
      *
      * @param context  the Context to use
      *
      * @throws IOException  if writing the recovery command file
      * fails, or if the reboot itself fails.
      */
     public static void rebootWipeUserData(Context context)
         throws IOException {
         bootCommand(context, "--wipe_data");
     }

     /**
      * Reboot into the recovery system to wipe the /data partition and toggle
      * Encrypted File Systems on/off.
      * @param extras to add to the RECOVERY_COMPLETED intent after rebooting.
      * @throws IOException if something goes wrong.
      *
      * @hide
      */
     public static void rebootToggleEFS(Context context, boolean efsEnabled)
         throws IOException {
         if (efsEnabled) {
             bootCommand(context, "--set_encrypted_filesystem=on");
         } else {
             bootCommand(context, "--set_encrypted_filesystem=off");
         }
     }

     /**
      * Reboot into the recovery system with the supplied argument.
      * @param arg to pass to the recovery utility.
      * @throws IOException if something goes wrong.
      */
     private static void bootCommand(Context context, String arg) throws IOException {
         RECOVERY_DIR.mkdirs();  // In case we need it
         COMMAND_FILE.delete();  // In case it's not writable
         LOG_FILE.delete();

         FileWriter command = new FileWriter(COMMAND_FILE);
         try {
             command.write(arg);
             command.write("\n");
         } finally {
             command.close();
         }

         // Having written the command file, go ahead and reboot
         PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
         pm.reboot("recovery");

         throw new IOException("Reboot failed (no permissions?)");
     }

     /**
      * Called after booting to process and remove recovery-related files.
      * @return the log file from recovery, or null if none was found.
      *
      * @hide
      */
     public static String handleAftermath() {
         // Record the tail of the LOG_FILE
         String log = null;
         try {
             log = FileUtils.readTextFile(LOG_FILE, -LOG_FILE_MAX_LENGTH, "...\n");
         } catch (FileNotFoundException e) {
             Log.i(TAG, "No recovery log file");
         } catch (IOException e) {
             Log.e(TAG, "Error reading recovery log", e);
         }

         // Delete everything in RECOVERY_DIR
         String[] names = RECOVERY_DIR.list();
         for (int i = 0; names != null && i < names.length; i++) {
             File f = new File(RECOVERY_DIR, names[i]);
             if (!f.delete()) {
                 Log.e(TAG, "Can't delete: " + f);
             } else {
                 Log.i(TAG, "Deleted: " + f);
             }
         }

         return log;
     }

     private void RecoverySystem() { }  // Do not instantiate
 }
	/*
	* Copyright (C) 2010 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.os;

	import java.io.ByteArrayInputStream;
	import java.io.File;
	import java.io.FileNotFoundException;
	import java.io.FileWriter;
	import java.io.IOException;
	import java.io.RandomAccessFile;
	import java.security.GeneralSecurityException;
	import java.security.PublicKey;
	import java.security.Signature;
	import java.security.SignatureException;
	import java.security.cert.Certificate;
	import java.security.cert.CertificateFactory;
	import java.security.cert.X509Certificate;
	import java.util.Collection;
	import java.util.Enumeration;
	import java.util.HashSet;
	import java.util.Iterator;
	import java.util.List;
	import java.util.zip.ZipEntry;
	import java.util.zip.ZipFile;

	import android.content.Context;
	import android.util.Log;

	import org.apache.harmony.security.asn1.BerInputStream;
	import org.apache.harmony.security.pkcs7.ContentInfo;
	import org.apache.harmony.security.pkcs7.SignedData;
	import org.apache.harmony.security.pkcs7.SignerInfo;
	import org.apache.harmony.security.provider.cert.X509CertImpl;

	/**
	* RecoverySystem contains methods for interacting with the Android
	* recovery system (the separate partition that can be used to install
	* system updates, wipe user data, etc.)
	*/
	public class RecoverySystem {
	private static final String TAG = "RecoverySystem";

	/**
	* Default location of zip file containing public keys (X509
	* certs) authorized to sign OTA updates.
	*/
	private static final File DEFAULT_KEYSTORE =
	new File("/system/etc/security/otacerts.zip");

	/** Send progress to listeners no more often than this (in ms). */
	private static final long PUBLISH_PROGRESS_INTERVAL_MS = 500;

	/** Used to communicate with recovery. See bootable/recovery/recovery.c. */
	private static File RECOVERY_DIR = new File("/cache/recovery");
	private static File COMMAND_FILE = new File(RECOVERY_DIR, "command");
	private static File LOG_FILE = new File(RECOVERY_DIR, "log");

	// Length limits for reading files.
	private static int LOG_FILE_MAX_LENGTH = 64 * 1024;

	/**
	* Interface definition for a callback to be invoked regularly as
	* verification proceeds.
	*/
	public interface ProgressListener {
	/**
	* Called periodically as the verification progresses.
	*
	* @param progress the approximate percentage of the
	* verification that has been completed, ranging from 0
	* to 100 (inclusive).
	*/
	public void onProgress(int progress);
	}

	/** @return the set of certs that can be used to sign an OTA package. */
	private static HashSet<Certificate> getTrustedCerts(File keystore)
	throws IOException, GeneralSecurityException {
	HashSet<Certificate> trusted = new HashSet<Certificate>();
	if (keystore == null) {
	keystore = DEFAULT_KEYSTORE;
	}
	ZipFile zip = new ZipFile(keystore);
	try {
	CertificateFactory cf = CertificateFactory.getInstance("X.509");
	Enumeration<? extends ZipEntry> entries = zip.entries();
	while (entries.hasMoreElements()) {
	ZipEntry entry = entries.nextElement();
	trusted.add(cf.generateCertificate(zip.getInputStream(entry)));
	}
	} finally {
	zip.close();
	}
	return trusted;
	}

	/**
	* Verify the cryptographic signature of a system update package
	* before installing it. Note that the package is also verified
	* separately by the installer once the device is rebooted into
	* the recovery system. This function will return only if the
	* package was successfully verified; otherwise it will throw an
	* exception.
	*
	* Verification of a package can take significant time, so this
	* function should not be called from a UI thread. Interrupting
	* the thread while this function is in progress will result in a
	* SecurityException being thrown (and the thread's interrupt flag
	* will be cleared).
	*
	* @param packageFile the package to be verified
	* @param listener an object to receive periodic progress
	* updates as verification proceeds. May be null.
	* @param deviceCertsZipFile the zip file of certificates whose
	* public keys we will accept. Verification succeeds if the
	* package is signed by the private key corresponding to any
	* public key in this file. May be null to use the system default
	* file (currently "/system/etc/security/otacerts.zip").
	*
	* @throws IOException if there were any errors reading the
	* package or certs files.
	* @throws GeneralSecurityException if verification failed
	*/
	public static void verifyPackage(File packageFile,
	ProgressListener listener,
	File deviceCertsZipFile)
	throws IOException, GeneralSecurityException {
	long fileLen = packageFile.length();

	RandomAccessFile raf = new RandomAccessFile(packageFile, "r");
	try {
	int lastPercent = 0;
	long lastPublishTime = System.currentTimeMillis();
	if (listener != null) {
	listener.onProgress(lastPercent);
	}

	raf.seek(fileLen - 6);
	byte[] footer = new byte[6];
	raf.readFully(footer);

	if (footer[2] != (byte)0xff \|\| footer[3] != (byte)0xff) {
	throw new SignatureException("no signature in file (no footer)");
	}

	int commentSize = (footer[4] & 0xff) \| ((footer[5] & 0xff) << 8);
	int signatureStart = (footer[0] & 0xff) \| ((footer[1] & 0xff) << 8);
	Log.v(TAG, String.format("comment size %d; signature start %d",
	commentSize, signatureStart));

	byte[] eocd = new byte[commentSize + 22];
	raf.seek(fileLen - (commentSize + 22));
	raf.readFully(eocd);

	// Check that we have found the start of the
	// end-of-central-directory record.
	if (eocd[0] != (byte)0x50 \|\| eocd[1] != (byte)0x4b \|\|
	eocd[2] != (byte)0x05 \|\| eocd[3] != (byte)0x06) {
	throw new SignatureException("no signature in file (bad footer)");
	}

	for (int i = 4; i < eocd.length-3; ++i) {
	if (eocd[i ] == (byte)0x50 && eocd[i+1] == (byte)0x4b &&
	eocd[i+2] == (byte)0x05 && eocd[i+3] == (byte)0x06) {
	throw new SignatureException("EOCD marker found after start of EOCD");
	}
	}

	// The following code is largely copied from
	// JarUtils.verifySignature(). We could just call that
	// method here if that function didn't read the entire
	// input (ie, the whole OTA package) into memory just to
	// compute its message digest.

	BerInputStream bis = new BerInputStream(
	new ByteArrayInputStream(eocd, commentSize+22-signatureStart, signatureStart));
	ContentInfo info = (ContentInfo)ContentInfo.ASN1.decode(bis);
	SignedData signedData = info.getSignedData();
	if (signedData == null) {
	throw new IOException("signedData is null");
	}
	Collection encCerts = signedData.getCertificates();
	if (encCerts.isEmpty()) {
	throw new IOException("encCerts is empty");
	}
	// Take the first certificate from the signature (packages
	// should contain only one).
	Iterator it = encCerts.iterator();
	X509Certificate cert = null;
	if (it.hasNext()) {
	cert = new X509CertImpl((org.apache.harmony.security.x509.Certificate)it.next());
	} else {
	throw new SignatureException("signature contains no certificates");
	}

	List sigInfos = signedData.getSignerInfos();
	SignerInfo sigInfo;
	if (!sigInfos.isEmpty()) {
	sigInfo = (SignerInfo)sigInfos.get(0);
	} else {
	throw new IOException("no signer infos!");
	}

	// Check that the public key of the certificate contained
	// in the package equals one of our trusted public keys.

	HashSet<Certificate> trusted = getTrustedCerts(
	deviceCertsZipFile == null ? DEFAULT_KEYSTORE : deviceCertsZipFile);

	PublicKey signatureKey = cert.getPublicKey();
	boolean verified = false;
	for (Certificate c : trusted) {
	if (c.getPublicKey().equals(signatureKey)) {
	verified = true;
	break;
	}
	}
	if (!verified) {
	throw new SignatureException("signature doesn't match any trusted key");
	}

	// The signature cert matches a trusted key. Now verify that
	// the digest in the cert matches the actual file data.

	// The verifier in recovery only handles SHA1withRSA
	// signatures. SignApk.java always uses SHA1withRSA, no
	// matter what the cert says to use. Ignore
	// cert.getSigAlgName(), and instead use whatever
	// algorithm is used by the signature (which should be
	// SHA1withRSA).

	String da = sigInfo.getdigestAlgorithm();
	String dea = sigInfo.getDigestEncryptionAlgorithm();
	String alg = null;
	if (da == null \|\| dea == null) {
	// fall back to the cert algorithm if the sig one
	// doesn't look right.
	alg = cert.getSigAlgName();
	} else {
	alg = da + "with" + dea;
	}
	Signature sig = Signature.getInstance(alg);
	sig.initVerify(cert);

	// The signature covers all of the OTA package except the
	// archive comment and its 2-byte length.
	long toRead = fileLen - commentSize - 2;
	long soFar = 0;
	raf.seek(0);
	byte[] buffer = new byte[4096];
	boolean interrupted = false;
	while (soFar < toRead) {
	interrupted = Thread.interrupted();
	if (interrupted) break;
	int size = buffer.length;
	if (soFar + size > toRead) {
	size = (int)(toRead - soFar);
	}
	int read = raf.read(buffer, 0, size);
	sig.update(buffer, 0, read);
	soFar += read;

	if (listener != null) {
	long now = System.currentTimeMillis();
	int p = (int)(soFar * 100 / toRead);
	if (p > lastPercent &&
	now - lastPublishTime > PUBLISH_PROGRESS_INTERVAL_MS) {
	lastPercent = p;
	lastPublishTime = now;
	listener.onProgress(lastPercent);
	}
	}
	}
	if (listener != null) {
	listener.onProgress(100);
	}

	if (interrupted) {
	throw new SignatureException("verification was interrupted");
	}

	if (!sig.verify(sigInfo.getEncryptedDigest())) {
	throw new SignatureException("signature digest verification failed");
	}
	} finally {
	raf.close();
	}
	}

	/**
	* Reboots the device in order to install the given update
	* package.
	* Requires the {@link android.Manifest.permission#REBOOT}
	* and {@link android.Manifest.permission#ACCESS_CACHE_FILESYSTEM}
	* permissions.
	*
	* @param context the Context to use
	* @param packageFile the update package to install. Currently
	* must be on the /cache or /data partitions.
	*
	* @throws IOException if writing the recovery command file
	* fails, or if the reboot itself fails.
	*/
	public static void installPackage(Context context, File packageFile)
	throws IOException {
	String filename = packageFile.getCanonicalPath();

	if (filename.startsWith("/cache/")) {
	filename = "CACHE:" + filename.substring(7);
	} else if (filename.startsWith("/data/")) {
	filename = "DATA:" + filename.substring(6);
	} else {
	throw new IllegalArgumentException(
	"Must start with /cache or /data: " + filename);
	}
	Log.w(TAG, "!!! REBOOTING TO INSTALL " + filename + " !!!");
	String arg = "--update_package=" + filename;
	bootCommand(context, arg);
	}

	/**
	* Reboots the device and wipes the user data partition. This is
	* sometimes called a "factory reset", which is something of a
	* misnomer because the system partition is not restored to its
	* factory state.
	* Requires the {@link android.Manifest.permission#REBOOT}
	* and {@link android.Manifest.permission#ACCESS_CACHE_FILESYSTEM}
	* permissions.
	*
	* @param context the Context to use
	*
	* @throws IOException if writing the recovery command file
	* fails, or if the reboot itself fails.
	*/
	public static void rebootWipeUserData(Context context)
	throws IOException {
	bootCommand(context, "--wipe_data");
	}

	/**
	* Reboot into the recovery system to wipe the /data partition and toggle
	* Encrypted File Systems on/off.
	* @param extras to add to the RECOVERY_COMPLETED intent after rebooting.
	* @throws IOException if something goes wrong.
	*
	* @hide
	*/
	public static void rebootToggleEFS(Context context, boolean efsEnabled)
	throws IOException {
	if (efsEnabled) {
	bootCommand(context, "--set_encrypted_filesystem=on");
	} else {
	bootCommand(context, "--set_encrypted_filesystem=off");
	}
	}

	/**
	* Reboot into the recovery system with the supplied argument.
	* @param arg to pass to the recovery utility.
	* @throws IOException if something goes wrong.
	*/
	private static void bootCommand(Context context, String arg) throws IOException {
	RECOVERY_DIR.mkdirs(); // In case we need it
	COMMAND_FILE.delete(); // In case it's not writable
	LOG_FILE.delete();

	FileWriter command = new FileWriter(COMMAND_FILE);
	try {
	command.write(arg);
	command.write("\n");
	} finally {
	command.close();
	}

	// Having written the command file, go ahead and reboot
	PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
	pm.reboot("recovery");

	throw new IOException("Reboot failed (no permissions?)");
	}

	/**
	* Called after booting to process and remove recovery-related files.
	* @return the log file from recovery, or null if none was found.
	*
	* @hide
	*/
	public static String handleAftermath() {
	// Record the tail of the LOG_FILE
	String log = null;
	try {
	log = FileUtils.readTextFile(LOG_FILE, -LOG_FILE_MAX_LENGTH, "...\n");
	} catch (FileNotFoundException e) {
	Log.i(TAG, "No recovery log file");
	} catch (IOException e) {
	Log.e(TAG, "Error reading recovery log", e);
	}

	// Delete everything in RECOVERY_DIR
	String[] names = RECOVERY_DIR.list();
	for (int i = 0; names != null && i < names.length; i++) {
	File f = new File(RECOVERY_DIR, names[i]);
	if (!f.delete()) {
	Log.e(TAG, "Can't delete: " + f);
	} else {
	Log.i(TAG, "Deleted: " + f);
	}
	}

	return log;
	}

	private void RecoverySystem() { } // Do not instantiate
	}