Feature Request for IDS/IPS GUI-Based Editor for Full Suricata Rule Syntax

[spidysense]

Feature Request: GUI-Based Editor for Full Suricata Rule Syntax in OPNsense
Date: August 23, 2025
To: OPNsense Development Team
Subject: Request for Enhanced GUI Support for Adding and Editing Custom Suricata Rules

Summary
I respectfully request the addition of a GUI-based editor in OPNsense to allow users to manually add and edit full Suricata rules with complete syntax support, including advanced keywords such as fileext, http.method, and pcre. This feature would enhance the usability of the Suricata IDS/IPS plugin by eliminating the need for SSH-based file editing, which is currently required for complex rule definitions.

Current Limitation
The Services > Intrusion Detection > User Defined tab in OPNsense 25.7.2 provides a form for adding custom rules, but it is limited to basic fields: Enabled, Source IP, Destination IP, SSL/Fingerprint, and Action. These fields support simple IP-based or SSL fingerprint rules but do not allow users to specify advanced Suricata keywords or protocol-specific conditions. For example, to detect .dat file exfiltration via HTTP uploads, a rule like the following is needed:

drop http $HOME_NET any -> $EXTERNAL_NET any (msg:"Blocked .dat File Exfiltration via HTTP Upload"; http.method; content:"POST"; nocase; fileext:"dat"; filestore; sid:1000010; rev:2;)

OR

drop http $HOME_NET any -> $EXTERNAL_NET any (msg:"Blocked .dat File Exfiltration via HTTP Upload"; http.method; content:"POST"; nocase; fileext:"dat"; filestore; sid:1000010; rev:2;) drop ftp $HOME_NET any -> $EXTERNAL_NET any (msg:"Blocked .dat File Exfiltration via FTP"; fileext:"dat"; filestore; sid:1000011; rev:2;) drop smtp $HOME_NET any -> $EXTERNAL_NET any (msg:"Blocked .dat File Exfiltration via SMTP"; fileext:"dat"; filestore; sid:1000012; rev:2;) drop smb $HOME_NET any -> $EXTERNAL_NET any (msg:"Blocked .dat File Exfiltration via SMB"; fileext:"dat"; filestore; sid:1000013; rev:2;) drop nfs $HOME_NET any -> $EXTERNAL_NET any (msg:"Blocked .dat File Exfiltration via NFS"; fileext:"dat"; filestore; sid:1000014; rev:2;) drop dns $HOME_NET any -> $EXTERNAL_NET any (msg:"Blocked .dat File Exfiltration via DNS Tunneling"; dns.query; content:".dat"; nocase; pcre:"/^[a-f0-9]{32,}.dat$/"; sid:1000015; rev:2;)

This requires editing /usr/local/etc/suricata/rules/custom.rules via SSH, which is inaccessible to users without CLI experience or those in restricted environments where SSH is disabled for security reasons. Additionally, the absence of a GUI-based file editor under System > Diagnostics in some installations (e.g., 25.7.2) further complicates manual rule management.

Impact

Accessibility: Users without SSH access or CLI expertise cannot implement advanced Suricata rules, limiting the IDS/IPS functionality for non-technical administrators.

Security Risks: Enabling SSH to edit configuration files introduces potential security vulnerabilities, especially in production environments where SSH is disabled.

Use Case Example: Detecting file exfiltration (e.g., .dat or .pdf files via HTTP, FTP, SMTP, SMB, NFS, or DNS) requires complex rules with fileext and protocol-specific keywords. Without GUI support, users must resort to manual file edits, increasing the risk of errors and configuration issues.

Efficiency: Manual SSH-based edits are time-consuming and error-prone, requiring validation steps (e.g., suricata -T) that are not integrated into the GUI workflow.

Proposed Solution
I propose adding a Custom Rule Editor to the OPNsense GUI, either within Services > Intrusion Detection > User Defined or as a new tab (e.g., Custom Rules).

The editor should include:

Text-Based Rule Input:
A text area for entering full Suricata rule syntax, supporting all keywords (e.g., fileext, http.method, dns.query, pcre).
Syntax highlighting or validation to catch errors (e.g., invalid SIDs, missing semicolons).


Rule Management:
Options to add, edit, delete, enable/disable, and assign SIDs to custom rules.
Ability to group rules into categories (e.g., "File Exfiltration") for organization.


Integration with Suricata:
Automatic addition of rules to /usr/local/etc/suricata/rules/custom.rules (or a similar file).
Validation button to run suricata -T and display errors within the GUI.
Option to reload Suricata after changes (equivalent to service suricata restart).


Configuration Checks:
Automatic verification of prerequisites (e.g., file-store and fileinfo enabled in suricata.yaml for fileext rules).
Warnings for undefined variables (e.g., $HOME_NET) with suggestions to configure them in Global Settings.

Benefits

User Accessibility: Enables non-technical users to leverage Suricata's full capabilities without CLI knowledge, broadening OPNsense's audience.

Security: Reduces reliance on SSH, aligning with secure configurations where SSH is disabled.
Efficiency: Streamlines rule creation and management within the familiar GUI, reducing errors and configuration time.
Flexibility: Supports advanced use cases (e.g., file exfiltration detection, custom protocol monitoring) not possible with the current User Defined form.
Consistency: Aligns with other OPNsense features (e.g., firewall rule editor) that offer robust GUI controls.

Use Case Example
To detect and block .dat file exfiltration, users need to implement rules like I posted above.

Currently, this requires SSH access to edit /usr/local/etc/suricata/rules/custom.rules and verify /usr/local/etc/suricata/suricata.yaml, which is cumbersome and inaccessible in some environments. A GUI editor would allow users to input this rule directly, validate it, and apply it without leaving the web interface.

Additional Notes

Community Support: OPNsense forum threads and GitHub issues (e.g., #8232, #3472) highlight user demand for enhanced Suricata rule management, suggesting this feature would be well-received.

Implementation Feasibility: Similar GUI-based rule editors exist in competing platforms (e.g., pfSense's Snort/Suricata interfaces), providing a model for development.

Fallback: If a full editor is resource-intensive, consider adding a System > Diagnostics > Edit File option for suricata.yaml and custom.rules to all OPNsense versions, as it's missing in some 25.7.2 installations.

Conclusion
Adding a GUI-based editor for full Suricata rule syntax would significantly enhance the usability and security of OPNsense's IDS/IPS functionality. It would empower users to implement advanced rules for scenarios like file exfiltration detection without requiring CLI access, aligning with OPNsense's user-friendly design. We appreciate the development team's efforts and look forward to your consideration of this feature.

Thank you.