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[RESTRICT AUTOMERGE][SettingsProvider] key size limit for mutating settings

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Prior to targetSdk 22, apps could add random system settings keys which
opens an opportunity for OOM attacks. This CL adds a key size limit.

BUG: 239415997
Test: manual; will add cts test
Merged-In: Ic9e88c0cc3d7206c64ba5b5c7d15b50d1ffc9adc
Change-Id: Ic9e88c0cc3d7206c64ba5b5c7d15b50d1ffc9adc
(cherry picked from commit 783bcba343)
This commit is contained in:
Songchun Fan
2022-10-11 18:08:11 -07:00
committed by Song Chun Fan
parent d85a428210
commit f1831c8712
2 changed files with 126 additions and 16 deletions
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40
packages/SettingsProvider/src/com/android/providers/settings/SettingsState.java
View File

@@ -48,6 +48,7 @@ import android.util.Xml;
import android.util.proto.ProtoOutputStream;
import com.android.internal.annotations.GuardedBy;
import com.android.internal.annotations.VisibleForTesting;
import com.android.internal.util.ArrayUtils;
import com.android.server.LocalServices;
@@ -367,8 +368,8 @@ final class SettingsState {
Setting newSetting = new Setting(name, oldSetting.getValue(), null,
oldSetting.getPackageName(), oldSetting.getTag(), false,
oldSetting.getId());
int newSize = getNewMemoryUsagePerPackageLocked(newSetting.getPackageName(), oldValue,
newSetting.getValue(), oldDefaultValue, newSetting.getDefaultValue());
int newSize = getNewMemoryUsagePerPackageLocked(newSetting.getPackageName(), 0,
oldValue, newSetting.getValue(), oldDefaultValue, newSetting.getDefaultValue());
checkNewMemoryUsagePerPackageLocked(newSetting.getPackageName(), newSize);
mSettings.put(name, newSetting);
updateMemoryUsagePerPackageLocked(newSetting.getPackageName(), newSize);
@@ -396,8 +397,9 @@ final class SettingsState {
String oldDefaultValue = (oldState != null) ? oldState.defaultValue : null;
String newDefaultValue = makeDefault ? value : oldDefaultValue;
int newSize = getNewMemoryUsagePerPackageLocked(packageName, oldValue, value,
oldDefaultValue, newDefaultValue);
int newSize = getNewMemoryUsagePerPackageLocked(packageName,
oldValue == null ? name.length() : 0 /* deltaKeySize */,
oldValue, value, oldDefaultValue, newDefaultValue);
checkNewMemoryUsagePerPackageLocked(packageName, newSize);
Setting newState;
@@ -438,8 +440,12 @@ final class SettingsState {
}
Setting oldState = mSettings.remove(name);
int newSize = getNewMemoryUsagePerPackageLocked(oldState.packageName, oldState.value,
null, oldState.defaultValue, null);
if (oldState == null) {
return false;
}
int newSize = getNewMemoryUsagePerPackageLocked(oldState.packageName,
-name.length() /* deltaKeySize */,
oldState.value, null, oldState.defaultValue, null);
StatsLog.write(StatsLog.SETTING_CHANGED, name, /* value= */ "", /* newValue= */ "",
oldState.value, /* tag */ "", false, getUserIdFromKey(mKey),
@@ -462,15 +468,16 @@ final class SettingsState {
}
Setting setting = mSettings.get(name);
if (setting == null) {
return false;
}
Setting oldSetting = new Setting(setting);
String oldValue = setting.getValue();
String oldDefaultValue = setting.getDefaultValue();
String newValue = oldDefaultValue;
String newDefaultValue = oldDefaultValue;
int newSize = getNewMemoryUsagePerPackageLocked(setting.packageName, oldValue,
newValue, oldDefaultValue, newDefaultValue);
int newSize = getNewMemoryUsagePerPackageLocked(setting.packageName, 0, oldValue,
oldDefaultValue, oldDefaultValue, oldDefaultValue);
checkNewMemoryUsagePerPackageLocked(setting.packageName, newSize);
if (!setting.reset()) {
@@ -604,8 +611,8 @@ final class SettingsState {
}
@GuardedBy("mLock")
private int getNewMemoryUsagePerPackageLocked(String packageName, String oldValue,
String newValue, String oldDefaultValue, String newDefaultValue) {
private int getNewMemoryUsagePerPackageLocked(String packageName, int deltaKeySize,
String oldValue, String newValue, String oldDefaultValue, String newDefaultValue) {
if (isExemptFromMemoryUsageCap(packageName)) {
return 0;
}
@@ -614,7 +621,7 @@ final class SettingsState {
final int newValueSize = (newValue != null) ? newValue.length() : 0;
final int oldDefaultValueSize = (oldDefaultValue != null) ? oldDefaultValue.length() : 0;
final int newDefaultValueSize = (newDefaultValue != null) ? newDefaultValue.length() : 0;
final int deltaSize = newValueSize + newDefaultValueSize
final int deltaSize = deltaKeySize + newValueSize + newDefaultValueSize
- oldValueSize - oldDefaultValueSize;
return Math.max((currentSize != null) ? currentSize + deltaSize : deltaSize, 0);
}
@@ -1241,4 +1248,11 @@ final class SettingsState {
return false;
}
}
@VisibleForTesting
public int getMemoryUsage(String packageName) {
synchronized (mLock) {
return mPackageToMemoryUsage.getOrDefault(packageName, 0);
}
}
}

102
packages/SettingsProvider/test/src/com/android/providers/settings/SettingsStateTest.java
View File

@@ -186,8 +186,8 @@ public class SettingsStateTest extends AndroidTestCase {
public void testInsertSetting_memoryUsage() {
final Object lock = new Object();
final File file = new File(getContext().getCacheDir(), "setting.xml");
final String settingName = "test_setting";
final File file = new File(getContext().getCacheDir(), "setting.xml");
final String settingName = "test_setting";
SettingsState settingsState = new SettingsState(getContext(), lock, file, 1,
SettingsState.MAX_BYTES_PER_APP_PACKAGE_UNLIMITED, Looper.getMainLooper());
@@ -204,7 +204,7 @@ public class SettingsStateTest extends AndroidTestCase {
settingsState.deleteSettingLocked(settingName);
// Should not throw if usage is under the cap
settingsState.insertSettingLocked(settingName, Strings.repeat("A", 19999),
settingsState.insertSettingLocked(settingName, Strings.repeat("A", 19975),
null, false, "p1");
settingsState.deleteSettingLocked(settingName);
try {
@@ -222,5 +222,101 @@ public class SettingsStateTest extends AndroidTestCase {
assertTrue(ex.getMessage().contains("p1"));
}
assertTrue(settingsState.getSettingLocked(settingName).isNull());
try {
settingsState.insertSettingLocked(Strings.repeat("A", 20001), "",
null, false, "p1");
fail("Should throw because it exceeded per package memory usage");
} catch (IllegalStateException ex) {
assertTrue(ex.getMessage().contains("You are adding too many system settings"));
}
}
public void testMemoryUsagePerPackage() {
final Object lock = new Object();
final File file = new File(getContext().getCacheDir(), "setting.xml");
final String testPackage = "package";
SettingsState settingsState = new SettingsState(getContext(), lock, file, 1,
SettingsState.MAX_BYTES_PER_APP_PACKAGE_LIMITED, Looper.getMainLooper());
// Test inserting one key with default
final String settingName = "test_setting";
final String testKey1 = settingName;
final String testValue1 = Strings.repeat("A", 100);
settingsState.insertSettingLocked(testKey1, testValue1, null, true, testPackage);
int expectedMemUsage = testKey1.length() + testValue1.length()
+ testValue1.length() /* size for default */;
assertEquals(expectedMemUsage, settingsState.getMemoryUsage(testPackage));
// Test inserting another key
final String testKey2 = settingName + "2";
settingsState.insertSettingLocked(testKey2, testValue1, null, false, testPackage);
expectedMemUsage += testKey2.length() + testValue1.length();
assertEquals(expectedMemUsage, settingsState.getMemoryUsage(testPackage));
// Test updating first key with new default
final String testValue2 = Strings.repeat("A", 300);
settingsState.insertSettingLocked(testKey1, testValue2, null, true, testPackage);
expectedMemUsage += (testValue2.length() - testValue1.length()) * 2;
assertEquals(expectedMemUsage, settingsState.getMemoryUsage(testPackage));
// Test updating first key without new default
final String testValue3 = Strings.repeat("A", 50);
settingsState.insertSettingLocked(testKey1, testValue3, null, false, testPackage);
expectedMemUsage -= testValue2.length() - testValue3.length();
assertEquals(expectedMemUsage, settingsState.getMemoryUsage(testPackage));
// Test updating second key
settingsState.insertSettingLocked(testKey2, testValue2, null, false, testPackage);
expectedMemUsage -= testValue1.length() - testValue2.length();
assertEquals(expectedMemUsage, settingsState.getMemoryUsage(testPackage));
// Test resetting key
settingsState.resetSettingLocked(testKey1);
expectedMemUsage += testValue2.length() - testValue3.length();
assertEquals(expectedMemUsage, settingsState.getMemoryUsage(testPackage));
// Test resetting default value
settingsState.resetSettingDefaultValueLocked(testKey1);
expectedMemUsage -= testValue2.length();
assertEquals(expectedMemUsage, settingsState.getMemoryUsage(testPackage));
// Test deletion
settingsState.deleteSettingLocked(testKey2);
expectedMemUsage -= testValue2.length() + testKey2.length() /* key is deleted too */;
assertEquals(expectedMemUsage, settingsState.getMemoryUsage(testPackage));
// Test another package with a different key
final String testPackage2 = testPackage + "2";
final String testKey3 = settingName + "3";
settingsState.insertSettingLocked(testKey3, testValue1, null, true, testPackage2);
assertEquals(expectedMemUsage, settingsState.getMemoryUsage(testPackage));
final int expectedMemUsage2 = testKey3.length() + testValue1.length() * 2;
assertEquals(expectedMemUsage2, settingsState.getMemoryUsage(testPackage2));
// Test system package
settingsState.insertSettingLocked(testKey1, testValue1, null, true, "android");
assertEquals(expectedMemUsage, settingsState.getMemoryUsage(testPackage));
assertEquals(expectedMemUsage2, settingsState.getMemoryUsage(testPackage2));
assertEquals(0, settingsState.getMemoryUsage("android"));
// Test invalid value
try {
settingsState.insertSettingLocked(testKey1, Strings.repeat("A", 20001), null, false,
testPackage);
fail("Should throw because it exceeded per package memory usage");
} catch (IllegalStateException ex) {
assertTrue(ex.getMessage().contains("You are adding too many system settings"));
}
assertEquals(expectedMemUsage, settingsState.getMemoryUsage(testPackage));
// Test invalid key
try {
settingsState.insertSettingLocked(Strings.repeat("A", 20001), "", null, false,
testPackage);
fail("Should throw because it exceeded per package memory usage");
} catch (IllegalStateException ex) {
assertTrue(ex.getMessage().contains("You are adding too many system settings"));
}
assertEquals(expectedMemUsage, settingsState.getMemoryUsage(testPackage));
}
}