How to install trusted CA certificate on Android device?

147
votes

I have created my own CA certificate and now I want to install it on my Android Froyo device (HTC Desire Z), so that the device trusts my certificate.

Android stores CA certificates in its Java keystore in /system/etc/security/cacerts.bks. I copied the file to my computer, added my certificate using portecle 1.5 and pushed it back to the device.

Now, Android does not seem to reload the file automatically. I have read in several blog posts that I need to restart the device. Doing so results in the file being overwritten with the original one again.

My next try was to install the certificate from SD card by copying it and using the according option from the settings menu. The device tells me that the certificate has been installed, but apparently it does not trust the certificate. Moreover, when I try to copy the keystore to my computer, I still find the original stock cacerts.bks.

So, what is the right way to install my own root CA certificate on an Android 2.2 device as a trusted certificate? Is there a way to do it programmatically?

10
androidsslinstallationcertificate
You can assume a rooted phone here. :) – Björn Marschollek

10 Answers

127
votes

Prior to Android KitKat you have to root your device to install new certificates.

From Android KitKat (4.0) up to Nougat (7.0) it's possible and easy. I was able to install the Charles Web Debbuging Proxy cert on my un-rooted device and successfully sniff SSL traffic.

Extract from http://wiki.cacert.org/FAQ/ImportRootCert

Before Android version 4.0, with Android version Gingerbread & Froyo, there was a single read-only file ( /system/etc/security/cacerts.bks ) containing the trust store with all the CA ('system') certificates trusted by default on Android. Both system apps and all applications developed with the Android SDK use this. Use these instructions on installing CAcert certificates on Android Gingerbread, Froyo, ...

Starting from Android 4.0 (Android ICS/'Ice Cream Sandwich', Android 4.3 'Jelly Bean' & Android 4.4 'KitKat'), system trusted certificates are on the (read-only) system partition in the folder '/system/etc/security/' as individual files. However, users can now easily add their own 'user' certificates which will be stored in '/data/misc/keychain/certs-added'.

System-installed certificates can be managed on the Android device in the Settings -> Security -> Certificates -> 'System'-section, whereas the user trusted certificates are manged in the 'User'-section there. When using user trusted certificates, Android will force the user of the Android device to implement additional safety measures: the use of a PIN-code, a pattern-lock or a password to unlock the device are mandatory when user-supplied certificates are used.

Installing CAcert certificates as 'user trusted'-certificates is very easy. Installing new certificates as 'system trusted'-certificates requires more work (and requires root access), but it has the advantage of avoiding the Android lockscreen requirement.

From Android N onwards it gets a littler harder, see this extract from the Charles proxy website:

As of Android N, you need to add configuration to your app in order to have it trust the SSL certificates generated by Charles SSL Proxying. This means that you can only use SSL Proxying with apps that you control.

In order to configure your app to trust Charles, you need to add a Network Security Configuration File to your app. This file can override the system default, enabling your app to trust user installed CA certificates (e.g. the Charles Root Certificate). You can specify that this only applies in debug builds of your application, so that production builds use the default trust profile.

Add a file res/xml/network_security_config.xml to your app:

<network-security-config>    
    <debug-overrides> 
        <trust-anchors> 
            <!-- Trust user added CAs while debuggable only -->
            <certificates src="user" /> 
        </trust-anchors>    
    </debug-overrides>  
</network-security-config>

Then add a reference to this file in your app's manifest, as follows: 

<?xml version="1.0" encoding="utf-8"?> 
<manifest>
    <application android:networkSecurityConfig="@xml/network_security_config">
    </application> 
</manifest>
44
votes

I spent a lot of time trying to find an answer to this (I need Android to see StartSSL certificates). Conclusion: Android 2.1 and 2.2 allow you to import certificates, but only for use with WiFi and VPN. There is no user interface for updating the list of trusted root certificates, but there is discussion about adding that feature. It’s unclear whether there is a reliable workaround for manually updating and replacing the cacerts.bks file.

Details and links: http://www.mcbsys.com/techblog/2010/12/android-certificates/. In that post, see the link to Android bug 11231--you might want to add your vote and query to that bug.

16
votes

If you need your certificate for HTTPS connections you can add the .bks file as a raw resource to your application and extend DefaultHttpConnection so your certificates are used for HTTPS connections.

public class MyHttpClient extends DefaultHttpClient {

    private Resources _resources;

    public MyHttpClient(Resources resources) {
        _resources = resources;
    }

    @Override
    protected ClientConnectionManager createClientConnectionManager() {
        SchemeRegistry registry = new SchemeRegistry();
        registry.register(new Scheme("http", PlainSocketFactory
            .getSocketFactory(), 80));
        if (_resources != null) {
            registry.register(new Scheme("https", newSslSocketFactory(), 443));
        } else {
            registry.register(new Scheme("https", SSLSocketFactory
                .getSocketFactory(), 443));
        }
        return new SingleClientConnManager(getParams(), registry);
    }

    private SSLSocketFactory newSslSocketFactory() {
        try {
            KeyStore trusted = KeyStore.getInstance("BKS");
            InputStream in = _resources.openRawResource(R.raw.mystore);
            try {
                trusted.load(in, "pwd".toCharArray());
            } finally {
                in.close();
            }
            return new SSLSocketFactory(trusted);
        } catch (Exception e) {
            throw new AssertionError(e);
        }
    }
}
10
votes

The guide linked here will probably answer the original question without the need for programming a custom SSL connector.

Found a very detailed how-to guide on importing root certificates that actually steps you through installing trusted CA certificates on different versions of Android devices (among other devices).

Basically you'll need to:

  1. Download: the cacerts.bks file from your phone.

    adb pull /system/etc/security/cacerts.bks cacerts.bks

  2. Download the .crt file from the certifying authority you want to allow.

  3. Modify the cacerts.bks file on your computer using the BouncyCastle Provider

  4. Upload the cacerts.bks file back to your phone and reboot.

Here is a more detailed step by step to update earlier android phones: How to update HTTPS security certificate authority keystore on pre-android-4.0 device

6
votes

There is a MUCH easier solution to this than posted here, or in related threads. If you are using a webview (as I am), you can achieve this by executing a JAVASCRIPT function within it. If you are not using a webview, you might want to create a hidden one for this purpose. Here's a function that works in just about any browser (or webview) to kickoff ca installation (generally through the shared os cert repository, including on a Droid). It uses a nice trick with iFrames. Just pass the url to a .crt file to this function:

function installTrustedRootCert( rootCertUrl ){
    id = "rootCertInstaller";
    iframe = document.getElementById( id );
    if( iframe != null ) document.body.removeChild( iframe );
    iframe = document.createElement( "iframe" );
    iframe.id = id;
    iframe.style.display = "none";
    document.body.appendChild( iframe );
    iframe.src = rootCertUrl;
}

UPDATE:

The iframe trick works on Droids with API 19 and up, but older versions of the webview won't work like this. The general idea still works though - just download/open the file with a webview and then let the os take over. This may be an easier and more universal solution (in the actual java now):

 public static void installTrustedRootCert( final String certAddress ){
     WebView certWebView = new WebView( instance_ );
     certWebView.loadUrl( certAddress );
 }

Note that instance_ is a reference to the Activity. This works perfectly if you know the url to the cert. In my case, however, I resolve that dynamically with the server side software. I had to add a fair amount of additional code to intercept a redirection url and call this in a manner which did not cause a crash based on a threading complication, but I won't add all that confusion here...

3
votes

What I did to beable to use startssl certificates was quite easy. (on my rooted phone)

I copied /system/etc/security/cacerts.bks to my sdcard

Downloaded http://www.startssl.com/certs/ca.crt and http://www.startssl.com/certs/sub.class1.server.ca.crt

Went to portecle.sourceforge.net and ran portecle directly from the webpage.

Opened my cacerts.bks file from my sdcard (entered nothing when asked for a password)

Choose import in portacle and opened sub.class1.server.ca.crt, im my case it allready had the ca.crt but maybe you need to install that too.

Saved the keystore and copied it baxck to /system/etc/security/cacerts.bks (I made a backup of that file first just in case)

Rebooted my phone and now I can vist my site thats using a startssl certificate without errors.

3
votes

If you have a rooted device, you can use a Magisk Module to move User Certs to System so it will be Trusted Certificate

https://github.com/Magisk-Modules-Repo/movecert

2
votes

These steps worked for me:

  1. Install Dory Certificate Android app on your mobile device: https://play.google.com/store/apps/details?id=io.tempage.dorycert&hl=en_US
  2. Connect mobile device to laptop with USB Cable.
  3. Create root folder on Internal Phone memory, copy the certificate file in that folder and disconnect cable.
  4. Open Dory Certificate Android app, click the round [+] button and select the right Import File Certificate option.
  5. Select format, provide a name (I typed same as filename), browse the certificate file and click the [OK].
  6. Three cards will list up. I ignored the card that only had the [SIGN CSR] button and proceeded to click the [INSTALL] button on the two other cards.
  7. I refreshed the PWA web app I had opened no my mobile Chrome (it is hosted on a local IIS Web Server) and voala! No chrome warning message. The green lock was there. It was Working.

Alternatively, I found these options which I had no need to try myself but looked easy to follow:

Finally, it may not be relevant but, if you are looking to create and setup a self-signed certificate (with mkcert) for your PWA app (website) hosted on a local IIS Web server, I followed this page:

https://medium.com/@aweber01/locally-trusted-development-certificates-with-mkcert-and-iis-e09410d92031

Thanks and hope it helps!! :)

1
votes

Here's an alternate solution that actually adds your certificate to the built in list of default certificates: Trusting all certificates using HttpClient over HTTPS

However, it will only work for your application. There's no way to programmatically do it for all applications on a user's device, since that would be a security risk.

1
votes

Did you try: Settings -> Security -> Install from SD Card? – Alexander Egger Dec 20 '10 at 20:11

I'm not sure why is this not an answer already, but I just followed this advice and it worked.