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Commit 27faa572 authored by lucaslin's avatar lucaslin Committed by Lucas Lin
Browse files

Sanitize VPN label to prevent HTML injection 

This commit will try to sanitize the content of VpnDialog. This
commit creates a function which will try to sanitize the VPN
label, if the sanitized VPN label is different from the original
one, which means the VPN label might contain HTML tag or the VPN
label violates the words restriction(may contain some wording
which will mislead the user). For this kind of case, show the
package name instead of the VPN label to prevent misleading the
user.

The malicious VPN app might be able to add a large number of line
breaks with HTML in order to hide the system-displayed text from
the user in the connection request dialog. Thus, sanitizing the
content of the dialog is needed.

Bug: 204554636
Test: atest VpnDialogsTests
Change-Id: I8eb890fd2e5797d8d6ab5b12f9c628bc9616081d
parent 9e283d5e

packages/VpnDialogs/Android.bp

+6 −1
Original line number Diff line number Diff line
@@ -23,10 +23,15 @@ package { 
    default_applicable_licenses: ["frameworks_base_license"],

}



android_library {

    name: "VpnDialogsLib",

    srcs: ["src/**/*.java"],

}



android_app {

    name: "VpnDialogs",

    certificate: "platform",

    privileged: true,

    srcs: ["src/**/*.java"],

    static_libs: ["VpnDialogsLib"],

    platform_apis: true,

}

packages/VpnDialogs/res/values/strings.xml

+29 −0
Original line number Diff line number Diff line
@@ -100,4 +100,33 @@ 
         without any consequences. [CHAR LIMIT=20] -->

    <string name="dismiss">Dismiss</string>



    <!-- Malicious VPN apps may provide very long labels or cunning HTML to trick the system dialogs

         into displaying what they want. The system will attempt to sanitize the label, and if the

         label is deemed dangerous, then this string is used instead. The first argument is the

         first 30 characters of the label, and the second argument is the package name of the app.

         Example : Normally a VPN app may be called "My VPN app" in which case the dialog will read

         "My VPN app wants to set up a VPN connection...". If the label is very long, then, this

         will be used to show "VerylongVPNlabel… (com.my.vpn.app) wants to set up a VPN

         connection...". For this case, the code will refer to sanitized_vpn_label_with_ellipsis.

    -->

    <string name="sanitized_vpn_label_with_ellipsis">

        <xliff:g id="sanitized_vpn_label_with_ellipsis" example="My VPN app">%1$s</xliff:g>… (

        <xliff:g id="sanitized_vpn_label_with_ellipsis" example="com.my.vpn.app">%2$s</xliff:g>)

    </string>



    <!-- Malicious VPN apps may provide very long labels or cunning HTML to trick the system dialogs

         into displaying what they want. The system will attempt to sanitize the label, and if the

         label is deemed dangerous, then this string is used instead. The first argument is the

         label, and the second argument is the package name of the app.

         Example : Normally a VPN app may be called "My VPN app" in which case the dialog will read

         "My VPN app wants to set up a VPN connection...". If the VPN label contains HTML tag but

         the length is not very long, the dialog will show "VpnLabelWith&lt;br&gt;HtmlTag

         (com.my.vpn.app) wants to set up a VPN connection...". For this case, the code will refer

         to sanitized_vpn_label.

    -->

    <string name="sanitized_vpn_label">

        <xliff:g id="sanitized_vpn_label" example="My VPN app">%1$s</xliff:g> (

        <xliff:g id="sanitized_vpn_label" example="com.my.vpn.app">%2$s</xliff:g>)

    </string>



</resources>

packages/VpnDialogs/src/com/android/vpndialogs/ConfirmDialog.java

+56 −5
Original line number Diff line number Diff line
@@ -33,6 +33,7 @@ import android.view.View; 
import android.widget.Button;

import android.widget.TextView;



import com.android.internal.annotations.VisibleForTesting;

import com.android.internal.app.AlertActivity;

import com.android.internal.net.VpnConfig;
@@ -40,12 +41,19 @@ public class ConfirmDialog extends AlertActivity 
        implements DialogInterface.OnClickListener, ImageGetter {

    private static final String TAG = "VpnConfirm";



    // Usually the label represents the app name, 150 code points might be enough to display the app

    // name, and 150 code points won't cover the warning message from VpnDialog.

    @VisibleForTesting

    static final int MAX_VPN_LABEL_LENGTH = 150;



    @VpnManager.VpnType private final int mVpnType;



    private String mPackage;



    private VpnManager mVm;



    private View mView;



    public ConfirmDialog() {

        this(VpnManager.TYPE_VPN_SERVICE);

    }
@@ -54,6 +62,43 @@ public class ConfirmDialog extends AlertActivity 
        mVpnType = vpnType;

    }



    /**

     * This function will use the string resource to combine the VPN label and the package name.

     *

     * If the VPN label violates the length restriction, the first 30 code points of VPN label and

     * the package name will be returned. Or return the VPN label and the package name directly if

     * the VPN label doesn't violate the length restriction.

     *

     * The result will be something like,

     * - ThisIsAVeryLongVpnAppNameWhich... (com.vpn.app)

     *   if the VPN label violates the length restriction.

     * or

     * - VpnLabelWith&lt;br&gt;HtmlTag (com.vpn.app)

     *   if the VPN label doesn't violate the length restriction.

     *

     */

    private String getSimplifiedLabel(String vpnLabel, String packageName) {

        if (vpnLabel.codePointCount(0, vpnLabel.length()) > 30) {

            return getString(R.string.sanitized_vpn_label_with_ellipsis,

                    vpnLabel.substring(0, vpnLabel.offsetByCodePoints(0, 30)),

                            packageName);

        }



        return getString(R.string.sanitized_vpn_label, vpnLabel, packageName);

    }



    @VisibleForTesting

    protected String getSanitizedVpnLabel(String vpnLabel, String packageName) {

        final String sanitizedVpnLabel = Html.escapeHtml(vpnLabel);

        final boolean exceedMaxVpnLabelLength = sanitizedVpnLabel.codePointCount(0,

                sanitizedVpnLabel.length()) > MAX_VPN_LABEL_LENGTH;

        if (exceedMaxVpnLabelLength || !vpnLabel.equals(sanitizedVpnLabel)) {

            return getSimplifiedLabel(sanitizedVpnLabel, packageName);

        }



        return sanitizedVpnLabel;

    }



    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
@@ -75,15 +120,16 @@ public class ConfirmDialog extends AlertActivity 
            finish();

            return;

        }

        View view = View.inflate(this, R.layout.confirm, null);

        ((TextView) view.findViewById(R.id.warning)).setText(

                Html.fromHtml(getString(R.string.warning, getVpnLabel()),

                        this, null /* tagHandler */));

        mView = View.inflate(this, R.layout.confirm, null);

        ((TextView) mView.findViewById(R.id.warning)).setText(

                Html.fromHtml(getString(R.string.warning, getSanitizedVpnLabel(

                        getVpnLabel().toString(), mPackage)),

                        this /* imageGetter */, null /* tagHandler */));

        mAlertParams.mTitle = getText(R.string.prompt);

        mAlertParams.mPositiveButtonText = getText(android.R.string.ok);

        mAlertParams.mPositiveButtonListener = this;

        mAlertParams.mNegativeButtonText = getText(android.R.string.cancel);

        mAlertParams.mView = view;

        mAlertParams.mView = mView;

        setupAlert();



        getWindow().setCloseOnTouchOutside(false);
@@ -92,6 +138,11 @@ public class ConfirmDialog extends AlertActivity 
        button.setFilterTouchesWhenObscured(true);

    }



    @VisibleForTesting

    public CharSequence getWarningText() {

        return ((TextView) mView.findViewById(R.id.warning)).getText();

    }



    private CharSequence getVpnLabel() {

        try {

            return VpnConfig.getVpnLabel(this, mPackage);

packages/VpnDialogs/tests/Android.bp

0 → 100644
+36 −0
Original line number Diff line number Diff line 
// Copyright 2022, The Android Open Source Project

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.



package {

    default_applicable_licenses: ["frameworks_base_license"],

}



android_test {

    name: "VpnDialogsTests",

    // Use platform certificate because the test will invoke a hidden API.

    // (e.g. VpnManager#prepareVpn()).

    certificate: "platform",

    libs: [

        "android.test.runner",

        "android.test.base",

    ],

    static_libs: [

        "androidx.test.core",

        "androidx.test.rules",

        "androidx.test.ext.junit",

        "mockito-target-minus-junit4",

        "VpnDialogsLib",

    ],

    srcs: ["src/**/*.java"],

}

packages/VpnDialogs/tests/AndroidManifest.xml

0 → 100644
+31 −0
Original line number Diff line number Diff line 
<?xml version="1.0" encoding="utf-8"?>

<!--

/*

 * Copyright (C) 2022 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

-->

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

          xmlns:tools="http://schemas.android.com/tools"

          package="com.android.vpndialogs.tests">



    <application android:debuggable="true">

        <uses-library android:name="android.test.runner" />

        <activity android:name="com.android.vpndialogs.VpnDialogTest$InstrumentedConfirmDialog"/>

    </application>

    <instrumentation android:name="androidx.test.runner.AndroidJUnitRunner"

                     android:targetPackage="com.android.vpndialogs.tests"

                     android:label="Vpn dialog tests">

    </instrumentation>

</manifest>