Developer Libraries » Trusted Intents

package info.guardianproject.trustedintents;

import android.app.Activity;

import android.content.ActivityNotFoundException;

import android.content.ComponentName;

import android.content.Context;

import android.content.Intent;

import android.content.pm.ActivityInfo;

import android.content.pm.PackageInfo;

import android.content.pm.PackageManager;

import android.content.pm.PackageManager.NameNotFoundException;

import android.content.pm.ResolveInfo;

import android.content.pm.Signature;

import android.text.TextUtils;

import java.lang.reflect.Constructor;

import java.security.cert.CertificateException;

import java.util.LinkedHashSet;

public class TrustedIntents {

    private static TrustedIntents instance;

    private static PackageManager pm;

    private final LinkedHashSet<ApkSignaturePin> pinList;

    private TrustedIntents(Context context) {

        pm = context.getPackageManager();

        this.pinList = new LinkedHashSet<ApkSignaturePin>();

    }

    public static TrustedIntents get(Context context) {

        if (instance == null)

            instance = new TrustedIntents(context);

        return instance;

    }

    /**

     * Check whether a resolved {@link Activity} is trusted.

     *

     * @param resolveInfo the one to check

     * @return whether the {@code Intent}'s receiver is trusted

     */

    public boolean isReceiverTrusted(ResolveInfo resolveInfo) {

        return isPackageNameTrusted(resolveInfo.activityInfo.packageName);

    }

    /**

     * Check whether a resolved {@link Activity} is trusted.

     *

     * @param activityInfo the one to check

     * @return whether the {@code Intent}'s receiver is trusted

     */

    public boolean isReceiverTrusted(ActivityInfo activityInfo) {

        return isPackageNameTrusted(activityInfo.packageName);

    }

    /**

     * Check an {@link Intent} is trusted based on the {@code packageName} set

     * by {@link Intent#setPackage(String)}

     *

     * @param intent the one to check

     * @return whether the {@code Intent}'s receiver is trusted

     */

    public boolean isReceiverTrusted(Intent intent) {

        if (!isIntentSane(intent))

            return false;

        String packageName = intent.getPackage();

        if (TextUtils.isEmpty(packageName)) {

            packageName = intent.getComponent().getPackageName();

        }

        return isPackageNameTrusted(packageName);

    }

    /**

     * Check whether a {@code packageName} is trusted.

     *

     * @param packageName the one to check

     * @return whether the {@code packageName} is trusted

     */

    public boolean isPackageNameTrusted(String packageName) {

        try {

            checkTrustedSigner(packageName);

        } catch (NameNotFoundException e) {

            e.printStackTrace();

            return false;

        } catch (CertificateException e) {

            return false;

        }

        return true;

    }

    /**

     * Check if an {@link Intent} is from a trusted sender.

     *

     * @param intent the {@code Intent} to check

     * @return boolean whether {@code intent} is from a trusted sender

     * @see #addTrustedSigner(Class)

     */

    public boolean isIntentFromTrustedSender(Intent intent) {

        if (!isIntentSane(intent)) {

            return false;

        }

        String packageName = intent.getPackage();

        if (TextUtils.isEmpty(packageName)) {

            packageName = intent.getComponent().getPackageName();

        }

        if (TextUtils.isEmpty(packageName)) {

            return false;

        }

        return isPackageNameTrusted(packageName);

    }

    /**

     * Returns an {@link Intent} if the sending app is signed by one of

     * the trusted signing keys as set in {@link #addTrustedSigner(Class)}.

     *

     * @returns {@code null} if there is no {@code Intent} or if the

     * sender is not trusted.

     * @see #addTrustedSigner(Class)

     */

    public Intent getIntentFromTrustedSender(Activity activity) {

        Intent intent = activity.getIntent();

        if (isIntentFromTrustedSender(intent)) {

            return intent;

        }

        return null;

    }

    private boolean isIntentSane(Intent intent) {

        if (intent == null)

            return false;

        if (TextUtils.isEmpty(intent.getPackage())) {

            ComponentName componentName = intent.getComponent();

            if (componentName == null || TextUtils.isEmpty(componentName.getPackageName())) {

                return false;

            }

        }

        return true;

    }

    /**

     * Add an APK signature that is always trusted for any packageName.

     *

     * @param cls {@link Class} of the {@link ApkSignaturePin} to trust

     * @return boolean

     * @throws {@link IllegalArgumentException} the class cannot be instantiated

     */

    public boolean addTrustedSigner(Class<? extends ApkSignaturePin> cls) {

        try {

            Constructor<? extends ApkSignaturePin> constructor = cls.getConstructor();

            return pinList.add((ApkSignaturePin) constructor.newInstance((Object[]) null));

        } catch (Exception e) {

            e.printStackTrace();

            throw new IllegalArgumentException(e);

        }

    }

    /**

     * Remove an APK signature from the trusted set.

     *

     * @param cls {@link Class} of the {@link ApkSignaturePin} to remove

     */

    public boolean removeTrustedSigner(Class<? extends ApkSignaturePin> cls) {

        for (ApkSignaturePin pin : pinList) {

            if (pin.getClass().equals(cls)) {

                return pinList.remove(pin);

            }

        }

        return false;

    }

    /**

     * Remove all {@link ApkSignaturePin}s from the trusted set.

     */

    public boolean removeAllTrustedSigners() {

        pinList.clear();

        return pinList.isEmpty();

    }

    /**

     * Check if a {@link ApkSignaturePin} is trusted.

     *

     * @param cls {@link Class} of the {@link ApkSignaturePin} to check

     */

    public boolean isTrustedSigner(Class<? extends ApkSignaturePin> cls) {

        for (ApkSignaturePin pin : pinList) {

            if (pin.getClass().equals(cls)) {

                return true;

            }

        }

        return false;

    }

    public void checkTrustedSigner(String packageName)

            throws NameNotFoundException, CertificateException {

        PackageInfo packageInfo = pm.getPackageInfo(packageName, PackageManager.GET_SIGNATURES);

        checkTrustedSigner(packageInfo.signatures);

    }

    public void checkTrustedSigner(PackageInfo packageInfo)

            throws NameNotFoundException, CertificateException {

        checkTrustedSigner(packageInfo.signatures);

    }

    public void checkTrustedSigner(Signature[] signatures)

            throws NameNotFoundException, CertificateException {

        if (signatures == null || signatures.length == 0)

            throw new CertificateException("signatures cannot be null or empty!");

        for (int i = 0; i < signatures.length; i++)

            if (signatures[i] == null || signatures[i].toByteArray().length == 0)

                throw new CertificateException("Certificates cannot be null or empty!");

        // check whether the APK signer is trusted for all apps

        for (ApkSignaturePin pin : pinList)

            if (areSignaturesEqual(signatures, pin.getSignatures()))

                return; // found a matching trusted APK signer

        throw new CertificateException("APK signatures did not match!");

    }

    public boolean areSignaturesEqual(Signature[] sigs0, Signature[] sigs1) {

        // TODO where is Android's implementation of this that I can just call?

        if (sigs0 == null || sigs1 == null)

            return false;

        if (sigs0.length == 0 || sigs1.length == 0)

            return false;

        if (sigs0.length != sigs1.length)

            return false;

        for (int i = 0; i < sigs0.length; i++)

            if (!sigs0[i].equals(sigs1[i]))

                return false;

        return true;

    }

    public void startActivity(Context context, Intent intent) throws CertificateException {

        if (!isIntentSane(intent))

            throw new ActivityNotFoundException("The intent was null or empty!");

        String packageName = intent.getPackage();

        if (TextUtils.isEmpty(packageName)) {

            packageName = intent.getComponent().getPackageName();

            intent.setPackage(packageName);

        }

        try {

            checkTrustedSigner(packageName);

        } catch (NameNotFoundException e) {

            e.printStackTrace();

            throw new ActivityNotFoundException(e.getLocalizedMessage());

        }

        context.startActivity(intent);

    }

}