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Use protectionLevel signature for security

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This commit is contained in:
Dominik Schürmann 2015-08-26 21:37:32 +02:00
parent e87693d989
commit 73cedf858b
2 changed files with 11 additions and 163 deletions
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10
Privileged-F-Droid/src/main/AndroidManifest.xml
View File

@ -11,6 +11,14 @@
android:name="android.permission.DELETE_PACKAGES"
tools:ignore="ProtectedPermissions" />
<!--
Only apps signed with the same key can use this permission!
Never presented to the user due to the protectionLevel.
-->
<permission
android:name="org.fdroid.fdroid.privileged.USE_SERVICE"
android:protectionLevel="signature" />
<application
android:allowBackup="false"
android:icon="@drawable/ic_launcher"
@ -22,7 +30,7 @@
android:enabled="true"
android:exported="true"
android:process=":fdroid_privileged"
tools:ignore="ExportedService">
android:permission="org.fdroid.fdroid.privileged.USE_SERVICE">
<intent-filter>
<action android:name="org.fdroid.fdroid.privileged.IPrivilegedService" />
</intent-filter>

164
Privileged-F-Droid/src/main/java/org/fdroid/fdroid/privileged/PrivilegedService.java
View File

@ -19,40 +19,25 @@
package org.fdroid.fdroid.privileged;
import android.annotation.SuppressLint;
import android.app.Service;
import android.content.Intent;
import android.content.pm.IPackageDeleteObserver;
import android.content.pm.IPackageInstallObserver;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.content.pm.Signature;
import android.net.Uri;
import android.os.Binder;
import android.os.IBinder;
import android.os.RemoteException;
import android.util.Log;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.lang.reflect.Method;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
/**
* This service provides an API via AIDL IPC for the main F-Droid app to install/delete packages.
* <p/>
* Security:
* Binding only works when,...
* - packageName is "org.fdroid.fdroid"
* - signature is equal or BuildConfig.DEBUG
*/
public class PrivilegedService extends Service {
public static final String TAG = "PrivilegedFDroid";
private static final String F_DROID_PACKAGE = "org.fdroid.fdroid";
private Method mInstallMethod;
private Method mDeleteMethod;
@ -119,16 +104,12 @@ public class PrivilegedService extends Service {
@Override
public void installPackage(Uri packageURI, int flags, String installerPackageName,
IPrivilegedCallback callback) {
if (isAllowed()) {
installPackageImpl(packageURI, flags, installerPackageName, callback);
}
installPackageImpl(packageURI, flags, installerPackageName, callback);
}
@Override
public void deletePackage(String packageName, int flags, IPrivilegedCallback callback) {
if (isAllowed()) {
deletePackageImpl(packageName, flags, callback);
}
deletePackageImpl(packageName, flags, callback);
}
};
@ -137,111 +118,6 @@ public class PrivilegedService extends Service {
return mBinder;
}
private boolean isAllowed() {
// Check that binding app is allowed to use this API
try {
barrierPackageName();
barrierPackageCertificate();
} catch (WrongPackageCertificateException e) {
Log.e(TAG, "package certificate is not allowed!", e);
return false;
} catch (WrongPackageNameException e) {
Log.e(TAG, "package name is not allowed!", e);
return false;
}
return true;
}
/**
* Checks if process that binds to this service (i.e. the package name corresponding to the
* process) is allowed. Only returns when package name is allowed!
*
* @throws WrongPackageNameException
*/
private void barrierPackageName() throws WrongPackageNameException {
int uid = Binder.getCallingUid();
String[] callingPackages = getPackageManager().getPackagesForUid(uid);
// is calling package allowed to use this service?
for (String currentPkg : callingPackages) {
if (F_DROID_PACKAGE.equals(currentPkg)) {
return;
}
}
throw new WrongPackageNameException("package name is not allowed");
}
private void barrierPackageCertificate() throws WrongPackageCertificateException {
String packageName = getCurrentCallingPackage();
byte[] packageCertificate;
try {
packageCertificate = getPackageCertificate(packageName);
} catch (PackageManager.NameNotFoundException e) {
throw new WrongPackageCertificateException(e.getMessage());
}
MessageDigest md;
try {
md = MessageDigest.getInstance("SHA-512");
} catch (NoSuchAlgorithmException e) {
throw new WrongPackageCertificateException("SHA-512 not available!");
}
byte[] hash = md.digest(packageCertificate);
Log.d(TAG, "hash:" + getHex(hash));
Log.d(TAG, "F_DROID_CERT_SHA512:" + BuildConfig.F_DROID_CERT_SHA512);
if (getHex(hash).equals(BuildConfig.F_DROID_CERT_SHA512)
|| BuildConfig.DEBUG) {
return;
}
throw new WrongPackageCertificateException("certificate not allowed!");
}
private byte[] getPackageCertificate(String packageName) throws PackageManager.NameNotFoundException {
// we do check the byte array of *all* signatures
@SuppressLint("PackageManagerGetSignatures")
PackageInfo pkgInfo = getPackageManager().getPackageInfo(packageName, PackageManager.GET_SIGNATURES);
// NOTE: Silly Android API naming: Signatures are actually certificates
Signature[] certificates = pkgInfo.signatures;
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
for (Signature cert : certificates) {
try {
outputStream.write(cert.toByteArray());
} catch (IOException e) {
throw new RuntimeException("Should not happen! Writing ByteArrayOutputStream to concat certificates failed");
}
}
// Even if an apk has several certificates, these certificates should never change
// Google Play does not allow the introduction of new certificates into an existing apk
// Also see this attack: http://stackoverflow.com/a/10567852
return outputStream.toByteArray();
}
/**
* Returns package name associated with the UID, which is assigned to the process that sent you the
* current transaction that is being processed :)
*
* @return package name
*/
protected String getCurrentCallingPackage() {
String[] callingPackages = getPackageManager().getPackagesForUid(Binder.getCallingUid());
// NOTE: No support for sharedUserIds
// callingPackages contains more than one entry when sharedUserId has been used
// No plans to support sharedUserIds due to many bugs connected to them:
// http://java-hamster.blogspot.de/2010/05/androids-shareduserid.html
return callingPackages[0];
}
@Override
public void onCreate() {
super.onCreate();
@ -266,40 +142,4 @@ public class PrivilegedService extends Service {
}
}
private String getHex(byte[] byteData) {
StringBuilder hexString = new StringBuilder();
for (byte aByteData : byteData) {
String hex = Integer.toHexString(0xff & aByteData);
if (hex.length() == 1) {
hexString.append('0');
}
hexString.append(hex);
}
return hexString.toString();
}
public static class WrongPackageCertificateException extends Exception {
private static final long serialVersionUID = -1294642703122196028L;
public WrongPackageCertificateException(String message) {
super(message);
}
}
public static class WrongPackageNameException extends Exception {
private static final long serialVersionUID = -2294642703111196028L;
public WrongPackageNameException(String message) {
super(message);
}
}
public static class AndroidNotCompatibleException extends Exception {
private static final long serialVersionUID = -3294642703111196028L;
public AndroidNotCompatibleException(String message) {
super(message);
}
}
}