How to remediate – MobiLink Server Detection

1. Introduction

MobiLink Server Detection indicates a database synchronization service is listening on a remote host. This service, part of the Sybase SQL Anywhere package, facilitates two-way data synchronisation between databases and mobile clients. Its presence can represent a potential attack surface if not properly secured. A successful exploit could lead to data compromise or denial of service.

2. Technical Explanation

The vulnerability arises from the MobiLink server listening for connections, potentially allowing unauthorised access. An attacker could attempt to connect and exploit vulnerabilities within the SQL Anywhere database engine itself. Preconditions include network connectivity to the port used by the MobiLink server.

• Root cause: The service is exposed on a network interface without sufficient restrictions.
• Exploit mechanism: An attacker could attempt to connect to the MobiLink server and exploit known vulnerabilities in SQL Anywhere, such as SQL injection or authentication bypasses. For example, an attacker might use a tool like `sqlcmd` to attempt connection with default credentials.
• Scope: Affected platforms are those running Sybase SQL Anywhere with the MobiLink component enabled. Specific versions depend on the installed SQL Anywhere package.

3. Detection and Assessment

Confirming exposure involves checking for the listening service and identifying its version. A quick check can identify if the port is open, while a thorough method will confirm the specific service running.

• Quick checks: Use `netstat -tulnp` (Linux) or `netstat -ano | findstr ` (Windows) to see if a process is listening on the default MobiLink port (typically 6121).
• Scanning: Nessus plugin ID 93847 may identify exposed MobiLink servers. This is an example only and results should be verified.
• Logs and evidence: Check SQL Anywhere server logs for connection attempts from unexpected sources. Log file locations vary based on installation, but are often in the Sybase directory under `logs`.

netstat -tulnp | grep 6121

4. Solution / Remediation Steps

The primary solution is to limit incoming traffic to the MobiLink server port if it isn’t required for business operations. If needed, restrict access using firewall rules.

4.1 Preparation

• Ensure you have a rollback plan to restore the original network configuration. A change window may be required for production systems.

4.2 Implementation

1. Step 1: Identify the port used by the MobiLink server (typically 6121).
2. Step 2: Configure your firewall to allow access only from trusted IP addresses or networks. For example, using `iptables` on Linux: `iptables -A INPUT -p tcp –dport 6121 -s / -j ACCEPT`.
3. Step 3: Block all other incoming traffic to the port: `iptables -A INPUT -p tcp –dport 6121 -j DROP`.

4.3 Config or Code Example

Before

# No firewall rules in place for port 6121

After

iptables -A INPUT -p tcp --dport 6121 -s / -j ACCEPT
iptables -A INPUT -p tcp --dport 6121 -j DROP

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help mitigate this issue. Least privilege reduces the impact of a successful exploit, while network segmentation limits exposure.

• Practice 1: Implement least privilege by granting only necessary permissions to database users and services.
• Practice 2: Use network segmentation to isolate sensitive systems like SQL Anywhere servers from untrusted networks.

4.5 Automation (Optional)

If using infrastructure-as-code, firewall rules can be automated.

# Example Ansible snippet
- name: Allow MobiLink traffic from trusted network
  iptables:
    chain: INPUT
    protocol: tcp
    destination_port: 6121
    source: /
    jump: ACCEPT
- name: Drop all other MobiLink traffic
  iptables:
    chain: INPUT
    protocol: tcp
    destination_port: 6121
    jump: DROP

5. Verification / Validation

Confirm the fix by checking firewall rules and verifying that only allowed connections are permitted. A service smoke test will ensure functionality remains intact.

• Post-fix check: Use `iptables -L INPUT` (Linux) to confirm the new rules are in place.
• Re-test: Re-run the `netstat` command from section 3 to verify that connections are only accepted from trusted sources.
• Smoke test: Attempt a database connection from an authorised client application to ensure synchronisation still works as expected.
• Monitoring: Monitor firewall logs for blocked connection attempts on port 6121, which could indicate unauthorised access attempts.

iptables -L INPUT

6. Preventive Measures and Monitoring

Regular security baselines and pipeline checks can prevent similar issues. A sensible patch cycle is also important.

• Baselines: Update your security baseline to include a requirement for restricting access to database ports like 6121.
• Asset and patch process: Implement a regular patch cycle for SQL Anywhere, including timely application of security updates.

7. Risks, Side Effects, and Roll Back

Incorrect firewall rules could block legitimate traffic. A roll back plan should restore the original network configuration.

• Roll back: Remove the added firewall rules using `iptables -D INPUT `. Restore the original network configuration from backup if necessary.

8. References and Resources

• Vendor advisory or bulletin: http://www.sybase.com/developer/mobile/sqlanywhere/mobilink