[android-security-discuss] Issue in accessing content provider which is protected by custom permission

[senthilnathan subramanian]

I have a content provider class implemented as a static Java library, and 
App-A is linking to the library and storing the data in the provider. 
 App-A is defining the content provider in its manifest as below with 
custom read and write permission. Everything is fine with App-A.

APP-A Manifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android";
    package="com.example.Arithmetic.app">
    
    <uses-sdk
        android:minSdkVersion="16"
        android:targetSdkVersion="23" />
 
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
       

        <activity android:name=".MyArithmeticActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <permission 
android:name="com.example.database.MyContentProvider.READ"
              
           android:label= "MyContentProvider_READ_label"
           android:protectionLevel="normal"/>

        <permission 
android:name="com.example.database.MyContentProvider.WRITE"
            
         android:label= "MyContentProvider_WRITE_label"
         android:protectionLevel="normal"/>

        <provider android:name="com.example.database.MyContentProvider"     
         
        android:authorities="com.example.database.MyContentProvider"
        android:enabled="true"
            android:exported="true"
        android:grantUriPermissions="true"
        android:protectionLevel="normal"
        android:readPermission="com.example.database.MyContentProvider.READ"
        
android:writePermission="com.example.database.MyContentProvider.WRITE"
        >
    </application>
</manifest>
 

And in App-B, I want to access the content provider 
(com.example.database.MyContentProvider) so I have included that custom 
permission in the App-B manifest as below.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android";
    package="com.equation.android.helloword"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="16"
        android:targetSdkVersion="23" />

    <uses-permission 
android:name="com.example.database.MyContentProvider.READ"/>
    <uses-permission 
android:name="com.example.database.MyContentProvider.WRITE"/>    

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

        <activity
            android:name="com.equation.android.helloword.MainActivity"
            android:label="@string/title_activity_main" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
     </application>
   
</manifest>


But when App-B access content provider, below security exception was thrown 
at run time. What I am doing wrong?, just for testing, if I change the 
permission of the content provider to any of the system defined permission 
(e.g android.permission.READ_USER_DICTIONARY) like below App-B able to 
access the provider using android.permission.READ_USER_DICTIONARY 
permission, Similarly if App-A don't define any permission for the content 
provider, App-B is able to access the provider (expected obviously), so why 
App-B is NOT able to access provider when its protected by custom 
permission. 

  <provider android:name="com.example.database.MyContentProvider"           
   
        android:authorities="com.example.database.MyContentProvider"
        android:enabled="true"
            android:exported="true"
        android:grantUriPermissions="true"
        android:protectionLevel="normal"
        android:readPermission="android.permission.READ_USER_DICTIONARY"
        android:writePermission="android.permission.READ_USER_DICTIONARY"
        >

Exception I get from App-B when its accessing content provider is below.

01-01 02:20:14.381  4594  4594 E AndroidRuntime: FATAL EXCEPTION: main
01-01 02:20:14.381  4594  4594 E AndroidRuntime: Process: 
com.equation.android.helloword, PID: 4594
01-01 02:20:14.381  4594  4594 E AndroidRuntime: 
java.lang.SecurityException: Permission Denial: opening provider 
com.example.database.MyContentProvider from ProcessR
ecord{734d867 4594:com.equation.android.helloword/u0a88} (pid=4594, 
uid=10088) requires com.example.database.MyContentProvider.READ or 
com.example.database.MyContentProvider.WRITE

MY development environment is Android M, SDK version 23.

Regards,
Senthil.

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