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Commit a7f61451 authored by Susi Kharraz-Post's avatar Susi Kharraz-Post
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Fast follow-on unit tests for HashedStringCache 

Unit tests for HashedStringCache that was commited in earlier CL
ag/6867725 . This is testing the various inputs and expected outputs.
Testing also revealed some vulnerability for invalid input so added
validation in the code under test.

Bug: b/129870147
Test: This is the test file
Change-Id: I7387f808df87a869f81339cd4aea99b23dfc06bd
parent 0454f3b8

core/java/android/util/HashedStringCache.java

+10 −5
Original line number Diff line number Diff line
@@ -22,6 +22,8 @@ import android.os.Environment; 
import android.os.storage.StorageManager;

import android.text.TextUtils;



import com.android.internal.annotations.VisibleForTesting;



import java.io.File;

import java.nio.charset.Charset;

import java.security.MessageDigest;
@@ -32,7 +34,6 @@ import java.security.SecureRandom; 
 * HashedStringCache provides hashing functionality with an underlying LRUCache and expiring salt.

 * Salt and expiration time are being stored under the tag passed in by the calling package --

 * intended usage is the calling package name.

 * TODO: Add unit tests b/129870147

 * @hide

 */

public class HashedStringCache {
@@ -40,9 +41,12 @@ public class HashedStringCache { 
    private static final Charset UTF_8 = Charset.forName("UTF-8");

    private static final int HASH_CACHE_SIZE = 100;

    private static final int HASH_LENGTH = 8;

    private static final String HASH_SALT = "_hash_salt";

    private static final String HASH_SALT_DATE = "_hash_salt_date";

    private static final String HASH_SALT_GEN = "_hash_salt_gen";

    @VisibleForTesting

    static final String HASH_SALT = "_hash_salt";

    @VisibleForTesting

    static final String HASH_SALT_DATE = "_hash_salt_date";

    @VisibleForTesting

    static final String HASH_SALT_GEN = "_hash_salt_gen";

    // For privacy we need to rotate the salt regularly

    private static final long DAYS_TO_MILLIS = 1000 * 60 * 60 * 24;

    private static final int MAX_SALT_DAYS = 100;
@@ -94,7 +98,8 @@ public class HashedStringCache { 
     */

    public HashResult hashString(Context context, String tag, String clearText,

            int saltExpirationDays) {

        if (TextUtils.isEmpty(clearText) || saltExpirationDays == -1) {

        if (saltExpirationDays == -1 || context == null

                || TextUtils.isEmpty(clearText) || TextUtils.isEmpty(tag)) {

            return null;

        }

core/tests/coretests/src/android/util/HashedStringCacheTest.java

0 → 100644
+189 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2019 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 android.util;



import static org.hamcrest.CoreMatchers.is;

import static org.hamcrest.CoreMatchers.not;

import static org.hamcrest.CoreMatchers.notNullValue;

import static org.hamcrest.CoreMatchers.nullValue;

import static org.hamcrest.MatcherAssert.assertThat;



import android.content.Context;

import android.content.SharedPreferences;

import android.os.Environment;

import android.os.storage.StorageManager;



import androidx.test.InstrumentationRegistry;



import org.junit.Before;

import org.junit.Test;



import java.io.File;





/**

 * Unit tests for {@link HashedStringCache}.

 */

public class HashedStringCacheTest {

    private static final String TAG = "HashedStringCacheTest";

    private Context mContext;

    private static final String TEST_STRING = "test_string";



    @Before

    public void setup() {

        mContext = null;

        mContext = InstrumentationRegistry.getContext();

        clearSharedPreferences();

    }



    @Test

    public void testInstanceNotNull() {

        HashedStringCache cache = HashedStringCache.getInstance();

        assertThat(cache, is(notNullValue()));

    }



    @Test

    public void testInstanceMatchesOnSecondCall() {

        HashedStringCache cache = HashedStringCache.getInstance();

        assertThat(HashedStringCache.getInstance(), is(cache));

    }



    @Test

    public void testHashedStringNotOriginalString() {

        HashedStringCache cache = HashedStringCache.getInstance();

        HashedStringCache.HashResult cachedResult =

                cache.hashString(mContext, TAG, TEST_STRING, 7);

        assertThat(cachedResult.hashedString, is(not(TEST_STRING)));

    }



    @Test

    public void testThatMultipleCallsResultInSameHash() {

        HashedStringCache cache = HashedStringCache.getInstance();

        HashedStringCache.HashResult cachedResult =

                cache.hashString(mContext, TAG, TEST_STRING, 7);

        HashedStringCache.HashResult cachedResult2 =

                cache.hashString(mContext, TAG, TEST_STRING, 7);

        assertThat(cachedResult2.hashedString, is(cachedResult.hashedString));

    }



    @Test

    public void testThatZeroDaysResultsInNewHash() {

        HashedStringCache cache = HashedStringCache.getInstance();

        HashedStringCache.HashResult cachedResult =

                cache.hashString(mContext, TAG, TEST_STRING, 7);

        HashedStringCache.HashResult cachedResult2 =

                cache.hashString(mContext, TAG, TEST_STRING, 0);

        assertThat(cachedResult2.hashedString, is(not(cachedResult.hashedString)));

    }



    @Test

    public void testThatNegativeDaysResultsInNewHash() {

        HashedStringCache cache = HashedStringCache.getInstance();

        HashedStringCache.HashResult cachedResult =

                cache.hashString(mContext, TAG, TEST_STRING, 7);

        HashedStringCache.HashResult cachedResult2 =

                cache.hashString(mContext, TAG, TEST_STRING, -10);

        assertThat(cachedResult2.hashedString, is(not(cachedResult.hashedString)));

    }



    @Test

    public void testThatDaysGreater365ResultsInSameResult() {

        HashedStringCache cache = HashedStringCache.getInstance();

        HashedStringCache.HashResult cachedResult =

                cache.hashString(mContext, TAG, TEST_STRING, 7);

        HashedStringCache.HashResult cachedResult2 =

                cache.hashString(mContext, TAG, TEST_STRING, 400);

        assertThat(cachedResult2.hashedString, is(cachedResult.hashedString));

    }



    /**

     * -1 is treated as a special input to short-circuit out of doing the hashing to give us

     * the option to turn this feature off if need be while incurring as little computational cost

     * as possible.

     */

    @Test

    public void testMinusOneResultsInNull() {

        HashedStringCache cache = HashedStringCache.getInstance();

        HashedStringCache.HashResult cachedResult =

                cache.hashString(mContext, TAG, TEST_STRING, -1);

        assertThat(cachedResult, is(nullValue()));

    }



    @Test

    public void testEmptyStringInput() {

        HashedStringCache cache = HashedStringCache.getInstance();

        HashedStringCache.HashResult cachedResult =

                cache.hashString(mContext, TAG, "", -1);

        assertThat(cachedResult, is(nullValue()));

    }



    @Test

    public void testNullInput() {

        HashedStringCache cache = HashedStringCache.getInstance();

        HashedStringCache.HashResult cachedResult =

                cache.hashString(mContext, TAG, null, -1);

        assertThat(cachedResult, is(nullValue()));

    }



    @Test

    public void testEmptyStringTag() {

        HashedStringCache cache = HashedStringCache.getInstance();

        HashedStringCache.HashResult cachedResult =

                cache.hashString(mContext, "", TEST_STRING, -1);

        assertThat(cachedResult, is(nullValue()));

    }



    @Test

    public void testNullTag() {

        HashedStringCache cache = HashedStringCache.getInstance();

        HashedStringCache.HashResult cachedResult =

                cache.hashString(mContext, null, TEST_STRING, -1);

        assertThat(cachedResult, is(nullValue()));

    }



    @Test

    public void testNullContext() {

        HashedStringCache cache = HashedStringCache.getInstance();

        HashedStringCache.HashResult cachedResult =

                cache.hashString(null, TAG, TEST_STRING, -1);

        assertThat(cachedResult, is(nullValue()));

    }



    private void clearSharedPreferences() {

        SharedPreferences preferences = getTestSharedPreferences(mContext);

        preferences.edit()

                .remove(TAG + HashedStringCache.HASH_SALT)

                .remove(TAG + HashedStringCache.HASH_SALT_DATE)

                .remove(TAG + HashedStringCache.HASH_SALT_GEN).apply();

    }



    /**

     * Android:ui doesn't have persistent preferences, so need to fall back on this hack originally

     * from ChooserActivity.java

     * @param context

     * @return

     */

    private SharedPreferences getTestSharedPreferences(Context context) {

        final File prefsFile = new File(new File(

                Environment.getDataUserCePackageDirectory(

                        StorageManager.UUID_PRIVATE_INTERNAL,

                        context.getUserId(), context.getPackageName()),

                "shared_prefs"),

                "hashed_cache_test.xml");

        return context.getSharedPreferences(prefsFile, Context.MODE_PRIVATE);

    }

}