how to install CA certificate programmatically on Android without user interaction

Question

I'm trying to install certificates without prompting the user. I know this is not good practice, but that's what PM wants.

Using KeyChain.createInstallIntent(), I can get Android to launch the certificate installation dialog by calling startActivity. However, when I pass the intent to sendBroadcast, nothing happens. Maybe the platform doesn't support this for security reasons?

String CERT_FILE = Environment.getExternalStorageDirectory() + "/test/IAT.crt";
Intent intent = KeyChain.createInstallIntent();
try {
    FileInputStream certIs = new FileInputStream(CERT_FILE);
    byte [] cert = new byte[(int)certFile.length()];
    certIs.read(cert);
    X509Certificate x509 = X509Certificate.getInstance(cert);
    intent.putExtra(KeyChain.EXTRA_CERTIFICATE, x509.getEncoded()); 
    intent.putExtra(KeyChain.EXTRA_NAME, "IAT Cert");
    EapActivity.this.startActivityForResult(intent, 0);  // this works but shows UI
    EapActivity.this.sendBroadcast(intent);  // this doesn't install cert
} catch (IOException e) {

Answer 1

You can only install certificates silently if you have system privileges. Showing up a confirmation dialog is intentional, since trusting certificates can have serious consequences -- Android could happily open phishing sites without a warning, etc. That said, the dialog in ICS/JB is pretty bad -- it doesn't tell you what certificate you are installing and who issued it, just that it's a CA certificate, which is kind of obvious.

So, either use the public KeyChain API and use startActivity() to get the confirmation dialog, or pre-provision devices before handling them to users.

Update: In Android 4.4, DevicePolicyManager has a hidden API (installCaCert) that allows you to install certificates silently. You need the MANAGE_CA_CERTIFICATES permission, which is signature|system, so still not doable for user-installed apps.

Answer 2

Using KeyChain.createInstallIntent(), I can get Android to launch the certificate installation dialog by calling startActivity. However, when I pass the intent to sendBroadcast, nothing happens.

Few if any Intent objects that you would pass to startActivity() would work with sendBroadcast(). They are independent channels of the quasi-message bus that is the Intent system.

Answer 3

For non-system app developers - the simple answer is it can not be done without user interaction.

For System App developers, I found the following solution, NB you must run the app with the system user id and sign the app with the system key or the service will reject your attempts to install the certificate.

Step 1 - Create interface

Create a new package in your project: android.security, then copy IKeyChainService.aidl into this package.

Step 2 - Bind to service and install certificate

The Activity gives an example of how to install a CA certificate:

public class KeyChainTest extends Activity {

    private final Object mServiceLock = new Object();
    private IKeyChainService mService;
    private boolean mIsBoundService =false;

    private ServiceConnection mServiceConnection = new ServiceConnection() {
        @Override public void onServiceConnected(ComponentName name, 
                                                    IBinder service) {
            synchronized (mServiceLock) {
                mService = IKeyChainService.Stub.asInterface(service);
                mServiceLock.notifyAll();
                try {

                    byte[] result = YOUR_CA_CERT_AS_BYTE_ARRAY

                    //The next line actually installs the certificate
                    mService.installCaCertificate(result);

                } catch (Exception e) {
                    //EXception handling goes here
                }
            }
        }

        @Override public void onServiceDisconnected(ComponentName name) {
            synchronized (mServiceLock) {
                mService = null;
            }
        }
    };

    private void bindService() {
        mIsBoundService = bindService(new Intent(IKeyChainService.class.getName()),
                mServiceConnection,
                Context.BIND_AUTO_CREATE);
    }

    private void unbindServices() {
        if (mIsBoundService) {
            unbindService(mServiceConnection);
            mIsBoundService = false;
        }
    }

    @Override public void onDestroy () {
        unbindServices();
    }


    @Override
    protected void onStart() {
        super.onStart();
        // Bind to KeyChainService
        bindService();
    }
}

I hope this helps someone - it took me a long time to work it out :)

Answer 4

This thread is a bit dated already, nevertheless since I stumbled upon the same issue and couldn't find any "out of the box" solution for Android O or later, I thought I'd share what I came up with and which worked well for me when trying to install Certificates (CA and others) to the Android Trusted credentials "User" store:

// Supply context, e.g. from "Context context = getApplicationContext();"
// String fileName points to the file holding the certificate to be installed. pem/der/pfx tested.
RandomAccessFile file = new RandomAccessFile(fileName, "r");
byte[] certificateBytes = new byte[(int)file.length()];
file.read(certificateBytes);

Class<?> keyChainConnectionClass = Objects.requireNonNull(context.getClassLoader()).loadClass("android.security.KeyChain$KeyChainConnection");
Class<?> iKeyChainServiceClass  = Objects.requireNonNull(context.getClassLoader()).loadClass("android.security.IKeyChainService");

Method keyChainBindMethod = KeyChain.class.getMethod("bind", Context.class);
Method keyChainConnectionGetServiceMethod = keyChainConnectionClass.getMethod("getService");
Object keyChainConnectionObject = keyChainBindMethod.invoke(null, context);
Object iKeyChainServiceObject = keyChainConnectionGetServiceMethod.invoke(keyChainConnectionObject);

Method installCaCertificate = iKeyChainServiceClass.getDeclaredMethod("installCaCertificate", byte[].class);
installCaCertificate.invoke(iKeyChainServiceObject, certificateBytes);

Note that if you want to silently install a certificate this way, your app needs to be a system app, i.e. it needs to have

android:sharedUserId="android.uid.system"

declared in it's manifest.

Cheers!

Answer 5

If you have root privilege, you could copy the certs file to /data/misc/user/0/cacerts-added/

Answer 6

Based on the @ospider's answer, i managed to succesfully install the cert like this way:

adb shell mkdir -p /data/misc/user/0/cacerts-added
adb push certificate.cer /data/misc/user/0/cacerts-added/807e3b02.0

# Maybe these two lines are not strictly necessary...
adb shell chmod 644 /data/misc/user/0/cacerts-added/807e3b02.0
adb shell chown system:system /data/misc/user/0/cacerts-added/807e3b02.0

I got the name of the copied file (807e3b02.0) by installing manually the cert i wanted to automate and seeing how Android saved it (whith adb shell ls -l /data/misc/user/0/cacerts-added/)

---

Hope this help.

Regards.

Answer 7

Only a system user application can silently install a CA certificate. On Lollipop though, Google introduced silent certificate management API through DevicePolicyManager, but you would either have to be Android-for-Work profile owner or device owner.