**Issue:**
- log_target accepted arbitrary paths, allowing authenticated users to write
files as root via fail2ban (e.g., /etc/cron.d/bangui-pwned)
- fail2ban runs as root and opens files specified in log_target
**Solution:**
1. **Model layer validation:** Already existed in GlobalConfigUpdate, prevents
invalid paths before reaching service
2. **Service layer validation:** Added defensive check in update_global_config()
that validates log_target even if model validation is bypassed
3. **New validation helper:** Added validate_log_target() utility that accepts
special values (STDOUT, STDERR, SYSLOG) or paths within allowed directories
**Changes:**
- app/utils/path_utils.py: Added validate_log_target() helper
- app/services/config_service.py: Added service-layer validation before
sending command to fail2ban
- backend/tests: Fixed session_secret length issues in fixtures (min 32 chars)
- backend/tests: Added tests for valid special log targets
- Docs/Backend-Development.md: Documented log_target security requirements
**Test Coverage:**
- Model validation rejects /etc/passwd (existing test)
- Model validation accepts STDOUT, STDERR, SYSLOG special values
- Model validation accepts paths in allowed directories
- Service layer validation tested with special values
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Lukas
d476e9d611