Clearing up invalid entries when SyncStorageEngine starts
Any app with permission WRITE_SYNC_SETTINGS could write sync settings
for authorities or accounts that are not valid. This results in invalid
data being persisted to disk which can effectively lead to a DOS style
attack. Clearing such entries on boot will make sure that a reboot fixes
any such issues.
Test: cts-tradefed run cts-dev -m CtsSyncContentHostTestCases
Bug: 35028827
Change-Id: I9e206a42508e3cba65d7523bf47fff743f47dcb2
Merged-In: I9e206a42508e3cba65d7523bf47fff743f47dcb2
(cherry picked from commit 042a478b73c3b7f7cd73f5bb1af657cfe07d0571)
diff --git a/services/core/java/com/android/server/content/SyncStorageEngine.java b/services/core/java/com/android/server/content/SyncStorageEngine.java
index 6adb37e..af52c6a 100644
--- a/services/core/java/com/android/server/content/SyncStorageEngine.java
+++ b/services/core/java/com/android/server/content/SyncStorageEngine.java
@@ -18,6 +18,7 @@
import android.accounts.Account;
import android.accounts.AccountAndUser;
+import android.accounts.AccountManager;
import android.content.ComponentName;
import android.content.ContentResolver;
import android.content.Context;
@@ -26,6 +27,7 @@
import android.content.SyncInfo;
import android.content.SyncRequest;
import android.content.SyncStatusInfo;
+import android.content.pm.PackageManager;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
@@ -404,6 +406,49 @@
public void onSyncRequest(EndPoint info, int reason, Bundle extras);
}
+ /**
+ * Validator that maintains a lazy cache of accounts and providers to tell if an authority or
+ * account is valid.
+ */
+ private static class AccountAuthorityValidator {
+ final private AccountManager mAccountManager;
+ final private PackageManager mPackageManager;
+ final private SparseArray<Account[]> mAccountsCache;
+ final private SparseArray<ArrayMap<String, Boolean>> mProvidersPerUserCache;
+
+ AccountAuthorityValidator(Context context) {
+ mAccountManager = context.getSystemService(AccountManager.class);
+ mPackageManager = context.getPackageManager();
+ mAccountsCache = new SparseArray<>();
+ mProvidersPerUserCache = new SparseArray<>();
+ }
+
+ // An account is valid if an installed authenticator has previously created that account
+ // on the device
+ boolean isAccountValid(Account account, int userId) {
+ Account[] accountsForUser = mAccountsCache.get(userId);
+ if (accountsForUser == null) {
+ accountsForUser = mAccountManager.getAccountsAsUser(userId);
+ mAccountsCache.put(userId, accountsForUser);
+ }
+ return ArrayUtils.contains(accountsForUser, account);
+ }
+
+ // An authority is only valid if it has a content provider installed on the system
+ boolean isAuthorityValid(String authority, int userId) {
+ ArrayMap<String, Boolean> authorityMap = mProvidersPerUserCache.get(userId);
+ if (authorityMap == null) {
+ authorityMap = new ArrayMap<>();
+ mProvidersPerUserCache.put(userId, authorityMap);
+ }
+ if (!authorityMap.containsKey(authority)) {
+ authorityMap.put(authority,
+ mPackageManager.resolveContentProviderAsUser(authority, 0, userId) != null);
+ }
+ return authorityMap.get(authority);
+ }
+ }
+
// Primary list of all syncable authorities. Also our global lock.
private final SparseArray<AuthorityInfo> mAuthorities =
new SparseArray<AuthorityInfo>();
@@ -1862,12 +1907,13 @@
eventType = parser.next();
AuthorityInfo authority = null;
PeriodicSync periodicSync = null;
+ AccountAuthorityValidator validator = new AccountAuthorityValidator(mContext);
do {
if (eventType == XmlPullParser.START_TAG) {
tagName = parser.getName();
if (parser.getDepth() == 2) {
if ("authority".equals(tagName)) {
- authority = parseAuthority(parser, version);
+ authority = parseAuthority(parser, version, validator);
periodicSync = null;
if (authority != null) {
if (authority.ident > highestAuthorityId) {
@@ -2000,7 +2046,8 @@
mMasterSyncAutomatically.put(userId, listen);
}
- private AuthorityInfo parseAuthority(XmlPullParser parser, int version) {
+ private AuthorityInfo parseAuthority(XmlPullParser parser, int version,
+ AccountAuthorityValidator validator) {
AuthorityInfo authority = null;
int id = -1;
try {
@@ -2045,12 +2092,22 @@
info = new EndPoint(
new Account(accountName, accountType),
authorityName, userId);
+ if (validator.isAccountValid(info.account, userId)
+ && validator.isAuthorityValid(authorityName, userId)) {
+ authority = getOrCreateAuthorityLocked(info, id, false);
+ } else {
+ EventLog.writeEvent(0x534e4554, "35028827", -1,
+ "account:" + info.account + " provider:" + authorityName + " user:"
+ + userId);
+ }
} else {
info = new EndPoint(
new ComponentName(packageName, className),
userId);
+ authority = getOrCreateAuthorityLocked(info, id, false);
}
- authority = getOrCreateAuthorityLocked(info, id, false);
+ }
+ if (authority != null) {
// If the version is 0 then we are upgrading from a file format that did not
// know about periodic syncs. In that case don't clear the list since we
// want the default, which is a daily periodic sync.
@@ -2059,8 +2116,6 @@
if (version > 0) {
authority.periodicSyncs.clear();
}
- }
- if (authority != null) {
authority.enabled = enabled == null || Boolean.parseBoolean(enabled);
if ("unknown".equals(syncable)) {
authority.syncable = -1;