Android

Just a very quick entry today. The previous weekend I wasted a lot of time trying to upgrade my phone to LineageOS 16. In general I followed the upgrading guide for my phone model but when I started the adb sideload it always failed with the error: "Error applying update: 7(ErrorCode:: kInstallDeviceOpenError)". I tried Friday evening with no success, I was searching for information a couple of hours at Saturday and I finally got it working on Sunday. I think summarizing what was needed in the blog would be better, maybe it is useful for someone else.

In general the reason seems to be that tissot (my phone model, Xiaomi Mi A1) needs something special in the TWRP boot loader. Finally I got it working after reading this beautiful issue. The problem is explained by the maintainer himself in this thread. My model, unlike most of the usual A/B devices, has a weird partitioning where most partitions are not slotted (except of boot, system, modem). By default, TWRP does not expect to have any non-slotted partition in the A/B OTA package. That is why the installation fails on all TWRP packages except the one provided by the maintainer. So, if having this model, you need to download that exact TWRP image in order to upgrade the system.

After using the correct TWRP version everything went successfully and I have LineageOS 16 in my phone. The main problem was finding the issue, I needed to google a lot until I found that page which described my exact problem.

Regards!

Short entry this time to upload the OpenWeatherMapProvider APK to the blog. More than two years ago I wrote another entry about this same topic and how I needed to compile the OpenWeatherMap provider for CyanogenMod 13. Since them I have been using the same APK file in CM 13 and Lineage 14 but, it seems that it's not valid anymore in version 15.1. I have just retired my old phone and in the new one the old APK was not working (it was installed without issues but then the weather app did not detect any provider installed).

So, after knowing that there are APKs available for other providers but not for OpenWeatherMap, I repeated the same steps than in my old entry.

git clone https://github.com/LineageOS/android_packages_apps_OpenWeatherMapProvider.git
cd android_packages_apps_OpenWeatherMapProvider/
git checkout lineage-15.1
./gradlew 
./gradlew build

This time I changed to branch 15.1 although it was unnecessary (the are no differences between branches 15.1 and 16.0). I received a rebuke the previous time so here you have the debug OpenWeatherMapWeatherProvider.apk. You can compile it by yourselves if you do not trust me (I would not do it). It is nice to see my new phone smoothly working now with lineage OS 15.1.

Best regards.

Today's entry presents a keycloak integration for an android application. Keycloak is an open-source project that offers Single Sign-On and access management for modern applications and services, and it has been used before in the blog. It is based on standards (like OpenID Connect and SAML) and provides some adapters for different programming languages and application platforms. Previously any integration between a mobile application and keycloak used an embedded browser to perform the login, but now that solution is a no-go. Google started to avoid this technique and recommend custom URLs long time ago. I have almost zero experience in mobile development (sorry for that) but I wanted to test this solution by myself anyway.

The idea is simple, as a mobile program is a client-side application I decided to use a public profile (similar situation to the one in browser-side JavaScript). I think that having a password in the client is almost the same than using none, it gives no extra security. The application is going to be a java one (it is just a PoC, so using kotlin was an extra effort for me).

First creating the public keycloak client for the application is needed. The application will use a weird URL keycloak://keycloaksample/.

Starting with the android application, the custom URL should be defined in the AndroidManifest.xml, in my case for the .MainActivity.

<activity android:name=".MainActivity">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <action android:name="android.intent.action.VIEW" />
        <category android:name="android.intent.category.LAUNCHER" />
        <category android:name="android.intent.category.DEFAULT" />
        <category android:name="android.intent.category.BROWSABLE" />
        <data android:scheme="keycloak"
            android:host="keycloaksample"
            android:pathPrefix="/"/>
    </intent-filter>
</activity>

With this configuration the .MainActivity will be called when the browser receives the keycloak://keycloaksample/ URL from the SSO server. That feature will be used to use the external browser to do the login and the logout. So a button will initiate the browser which will go to the authentication URL.

    public void login(View view) {
        // "http://192.168.100.1:8080/auth/realms/master/protocol/openid-connect/auth?client_id=KeycloakSample&scope=openid&response_type=code&redirect_uri=app%3A%2F%2Fkeycloaksample%2F";
        Uri uri = new Uri.Builder().scheme(configuration.getProperty("keycloak.scheme"))
                .encodedAuthority(configuration.getProperty("keycloak.authority"))
                .appendEncodedPath("auth/realms")
                .appendPath(configuration.getProperty("keycloak.realm"))
                .appendEncodedPath("protocol/openid-connect/auth")
                .appendQueryParameter("client_id", getString(R.string.app_name))
                .appendQueryParameter("scope", "openid")
                .appendQueryParameter("response_type", "code")
                .appendQueryParameter("redirect_uri", configuration.getProperty("app.url"))
                .build();
        Intent intent = new Intent(Intent.ACTION_VIEW, uri);
        startActivity(intent);
    }

If you see, the URL is created with the application URL as the redirect_uri. The idea is the login button starts the default browser with the keycloak authentication URL (android starts the app associated to an http(s) scheme), the user performs the login with it, and after that the server redirects the browser to the application URL, which starts the activity inside our app.

Now it's the time to follow the OIDC specification an get the code returned from the server and, with it, obtain the access and refresh token. In the onCreate of the activity a LoginTask starts a thread that executes the call to the token endpoint.

    if (Intent.ACTION_VIEW.equals(intent.getAction())) {
            // check if we have to login
            Uri uri = intent.getData();
            if (uri != null) {
                String code = uri.getQueryParameter("code");
                if (code != null) {
                    new LoginTask(this,
                            new Callback() {
                                @Override
                                public void onPostExecute(MainActivity activity, TokenResponse tokenResponse) {
                                    activity.setToken(tokenResponse);
                                }
                            }
                    ).execute(code);
                }
            }
        }

The LoginTask performs the authorization_code call to convert the code into the real tokens (remember this is just plain OIDC standard).

    @Override
    protected TokenResponse doInBackground(String... strings) {
        HttpURLConnection conn = null;
        try {
            String code = strings[0];
            URL keycloak = activity.createTokenURL();
            String urlParameters = activity.createAuthorizationCodePostData(code);
            byte[] postData = urlParameters.getBytes(StandardCharsets.UTF_8);
            conn = (HttpURLConnection) keycloak.openConnection();
            conn.setDoOutput(true);
            conn.setInstanceFollowRedirects(false);
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            conn.setRequestProperty("charset", "utf-8");
            conn.setRequestProperty("Content-Length", Integer.toString(postData.length));
            conn.setUseCaches(false);
            try (DataOutputStream wr = new DataOutputStream(conn.getOutputStream())) {
                wr.write(postData);
            }
            if (conn.getResponseCode() == 200) {
                return new TokenResponse(conn.getInputStream(), activity.getSignatureKey());
            } else {
                return new TokenResponse(conn.getResponseCode() + ": " + conn.getResponseMessage());
            }
        } catch (IOException|InvalidKeySpecException|NoSuchAlgorithmException e) {
            Log.d(TAG, "Error calling keycloak", e);
            return new TokenResponse(e.getMessage());
        } finally {
            if (conn != null) {
                conn.disconnect();
            }
        }
    }

The createTokenURL and createAuthorizationCodePostData methods assign the URL and the post data that will be sent to the server to obtain the tokens.

    public URL createTokenURL() throws MalformedURLException {
        // "http://192.168.100.1:8080/auth/realms/master/protocol/openid-connect/token"
        return new URL(new Uri.Builder().scheme(configuration.getProperty("keycloak.scheme"))
                .encodedAuthority(configuration.getProperty("keycloak.authority"))
                .appendEncodedPath("auth/realms")
                .appendPath(configuration.getProperty("keycloak.realm"))
                .appendEncodedPath("protocol/openid-connect/token")
                .build().toString());
    }

    public String createAuthorizationCodePostData(String code) {
        // "grant_type=authorization_code&client_id=KeycloakSample&redirect_uri=app%3A%2F%2Fkeycloaksample%2F&code=" + code
        return new Uri.Builder()
                .appendQueryParameter("grant_type", "authorization_code")
                .appendQueryParameter("client_id", getString(R.string.app_name))
                .appendQueryParameter("redirect_uri", configuration.getProperty("app.url"))
                .appendQueryParameter("code", code)
                .build().getEncodedQuery();
    }

And finally, with the JSON data returned by the server, a TokenResponse object is created. For that I used the jjwt project which can parse the different JWT tokens returned by the server. This way the application can obtain the token information and present the user info.

    public TokenResponse(InputStream is, Key key) throws IOException {
        this.creationTime = System.currentTimeMillis() / 1000L;
        this.key = key;
        JsonReader jsonReader = new JsonReader(new InputStreamReader(is, "UTF-8"));
        jsonReader.beginObject();
        while(jsonReader.hasNext()) {
            String name = jsonReader.nextName();
            switch (name) {
                case "expires_in":
                    this.setExpiresIn(jsonReader.nextInt());
                    break;
                case "refresh_expires_in":
                    this.setRefreshExpiresIn(jsonReader.nextInt());
                    break;
                case "access_token":
                    this.setAccessToken(jsonReader.nextString());
                    break;
                case "refresh_token":
                    this.setRefreshToken(jsonReader.nextString());
                    break;
                default:
                    jsonReader.skipValue();
            }
        }
    }

    public Jws getAccessTokenClaims() {
        return accessTokenClaims;
    }

    public String getAccessToken() {
        return accessToken;
    }

    public void setAccessToken(String accessToken) {
        this.accessToken = accessToken;
        this.accessTokenClaims = Jwts.parser()
                .setSigningKey(this.key)
                .parseClaimsJws(accessToken);
    }

To fully understand the code presented, the properties file used in the app is the following (information about keycloak: url, realm key,...).

keycloak.key=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8...
keycloak.scheme=http
keycloak.authority=192.168.100.1:8080
keycloak.realm=master
app.url=keycloak://keycloaksample/

Mainly this is the idea about the custom URL technique, android can associate a weird URL with the application and normal browser login is used to perform the SSO login. After that the OIDC calls are used to get the tokens and use them. My application also exemplifies how to do the logout, refresh the token and call another web service (userinfo) using the access token. But that is just development that uses the TokenResponse object initially created in the login.

Here I present a video, first I log into the application, thanks to custom URLs the browser is used to do that. Then the token information is shown and it is used to call the OIDC userinfo endpoint (information of the user). As you see the SSO is in place and I can reach the keycloak console without login again. Then I wait the access token to expire (60 seconds) and I refresh it (refresh_token action in the OIDC token endpoint). Finally I perform the logout which is a global logout too.

Your browser doesn't support the video tag. See this entry for more information about how to see the videos in this blog. You can download the file instead.

And that is all. I wanted to test the custom URL technique in an mobile application and I decided to use android (iOS is a complete unknown for me, but I suppose the same idea can be used for that platform). The application is very simple and just uses the jjwt project out of the default android API. This is just a PoC so it can be extended and/or improved a lot (for example not using fixed URLs and keys, calling the well-known OIDC address and the JWKs certificate endpoints is a better solution). Please also take in mind that I never develop for mobile, so just use the app as an example, surely things can be done much better. The KeycloakSample application can be download from here, hope it helps to someone else.

Regards!