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Commit f70e351d authored by Oli Lan's avatar Oli Lan
Browse files

Prevent exfiltration of system files via avatar picker. 

This adds mitigations to prevent system files being exfiltrated
via the settings content provider when a content URI is provided
as a chosen user image.

The mitigations are:

1) Copy the image to a new URI rather than the existing takePictureUri
prior to cropping.

2) Only allow a system handler to respond to the CROP intent.

This is a fixed version of ag/17003629, to address b/239513606.

Bug: 187702830
Test: build and check functionality
Merged-In: I15e15ad88b768a5b679de32c5429d921d850a3cb
Change-Id: I98eea867f926c508456ec9bc654e24eeeffa0e54
parent b9bafa0d

src/com/android/settings/users/EditUserPhotoController.java

+30 −13
Original line number Diff line number Diff line
@@ -21,7 +21,9 @@ import android.content.ClipData; 
import android.content.ContentResolver;

import android.content.Context;

import android.content.Intent;

import android.content.pm.ActivityInfo;

import android.content.pm.PackageManager;

import android.content.pm.ResolveInfo;

import android.database.Cursor;

import android.graphics.Bitmap;

import android.graphics.Bitmap.Config;
@@ -77,6 +79,7 @@ public class EditUserPhotoController { 
    private static final int REQUEST_CODE_TAKE_PHOTO   = 1002;

    private static final int REQUEST_CODE_CROP_PHOTO   = 1003;



    private static final String PRE_CROP_PICTURE_FILE_NAME = "PreCropEditUserPhoto.jpg";

    private static final String CROP_PICTURE_FILE_NAME = "CropEditUserPhoto.jpg";

    private static final String TAKE_PICTURE_FILE_NAME = "TakeEditUserPhoto2.jpg";

    private static final String NEW_USER_PHOTO_FILE_NAME = "NewUserPhoto.png";
@@ -87,6 +90,7 @@ public class EditUserPhotoController { 
    private final Fragment mFragment;

    private final ImageView mImageView;



    private final Uri mPreCropPictureUri;

    private final Uri mCropPictureUri;

    private final Uri mTakePictureUri;
@@ -98,6 +102,8 @@ public class EditUserPhotoController { 
        mContext = view.getContext();

        mFragment = fragment;

        mImageView = view;



        mPreCropPictureUri = createTempImageUri(mContext, PRE_CROP_PICTURE_FILE_NAME, !waiting);

        mCropPictureUri = createTempImageUri(mContext, CROP_PICTURE_FILE_NAME, !waiting);

        mTakePictureUri = createTempImageUri(mContext, TAKE_PICTURE_FILE_NAME, !waiting);

        mPhotoSize = getPhotoSize(mContext);
@@ -132,7 +138,7 @@ public class EditUserPhotoController { 
            case REQUEST_CODE_TAKE_PHOTO:

            case REQUEST_CODE_CHOOSE_PHOTO:

                if (mTakePictureUri.equals(pictureUri)) {

                    cropPhoto();

                    cropPhoto(pictureUri);

                } else {

                    copyAndCropPhoto(pictureUri);

                }
@@ -241,7 +247,7 @@ public class EditUserPhotoController { 
            protected Void doInBackground(Void... params) {

                final ContentResolver cr = mContext.getContentResolver();

                try (InputStream in = cr.openInputStream(pictureUri);

                        OutputStream out = cr.openOutputStream(mTakePictureUri)) {

                        OutputStream out = cr.openOutputStream(mPreCropPictureUri)) {

                    Streams.copy(in, out);

                } catch (IOException e) {

                    Log.w(TAG, "Failed to copy photo", e);
@@ -252,27 +258,38 @@ public class EditUserPhotoController { 
            @Override

            protected void onPostExecute(Void result) {

                if (!mFragment.isAdded()) return;

                cropPhoto();

                cropPhoto(mPreCropPictureUri);

            }

        }.execute();

    }



    private void cropPhoto() {

    private void cropPhoto(final Uri pictureUri) {

        // TODO: Use a public intent, when there is one.

        Intent intent = new Intent("com.android.camera.action.CROP");

        intent.setDataAndType(mTakePictureUri, "image/*");

        intent.setDataAndType(pictureUri, "image/*");

        appendOutputExtra(intent, mCropPictureUri);

        appendCropExtras(intent);

        if (intent.resolveActivity(mContext.getPackageManager()) != null) {

        try {

            StrictMode.disableDeathOnFileUriExposure();

                mFragment.startActivityForResult(intent, REQUEST_CODE_CROP_PHOTO);

            if (startSystemActivityForResult(intent, REQUEST_CODE_CROP_PHOTO)) {

                return;

            }

        } finally {

            StrictMode.enableDeathOnFileUriExposure();

        }

        } else {

        onPhotoCropped(mTakePictureUri, false);

    }



    private boolean startSystemActivityForResult(Intent intent, int code) {

        List<ResolveInfo> resolveInfos = mContext.getPackageManager()

                .queryIntentActivities(intent, PackageManager.MATCH_SYSTEM_ONLY);

        if (resolveInfos.isEmpty()) {

            Log.w(TAG, "No system package activity could be found for code " + code);

            return false;

        }

        intent.setPackage(resolveInfos.get(0).activityInfo.packageName);

        mFragment.startActivityForResult(intent, code);

        return true;

    }



    private void appendOutputExtra(Intent intent, Uri pictureUri) {