How to remediate – NoSQL Injection Authentication Bypass

1. Introduction

NoSQL Injection Authentication Bypass occurs when unsanitized data from a client request is used in a NoSQL database call, allowing attackers to execute arbitrary code. This can lead to data theft and potential control of server components. Systems using NoSQL databases without proper input validation are at risk. A successful attack could compromise confidentiality, integrity, and availability of the database and associated applications.

2. Technical Explanation

A NoSQL injection happens because a web application directly uses user-supplied data to build a NoSQL query string. Without sanitisation, an attacker can inject malicious code into this query. This is detected when scanners identify known error messages returned by the database server in response to crafted input. The Common Weakness Enumeration (CWE) for this issue is 89.

• Exploit mechanism: An attacker submits a malicious string as part of a request, which gets incorporated into the database query. For example, injecting JavaScript code into a MongoDB query to bypass authentication checks.
• Scope: Systems running MongoDB, CouchDB, Cassandra and other NoSQL databases are affected if they lack input validation on data used in queries.

3. Detection and Assessment

Confirming vulnerability involves checking for error messages indicating injection attempts and verifying the database version. Thorough assessment requires penetration testing with targeted payloads.

• Quick checks: Check the NoSQL database server version using its management interface or command line tool.
• Scanning: Burp Suite, OWASP ZAP, and other web application scanners can detect NoSQL injection vulnerabilities using specific signatures. These are examples only.
• Logs and evidence: Examine application logs for error messages related to invalid syntax in database queries. Look for patterns indicating attempts to inject code into the query string.

mongo --eval "db.adminCommand('ping')"

4. Solution / Remediation Steps

The most effective way to prevent NoSQL injection is to avoid constructing NoSQL queries using string concatenation with unsanitized data. Use existing escaping libraries for sanitisation.

4.1 Preparation

• Ensure you have a rollback plan in place to revert to the previous configuration if needed.
• Change windows may be required depending on service impact and approval processes.

4.2 Implementation

1. Step 1: Identify all code locations where NoSQL queries are constructed using string concatenation with user-supplied data.
2. Step 2: Replace the string concatenation with parameterised queries or prepared statements provided by your NoSQL database driver.
3. Step 3: Implement input validation to ensure that only expected characters and formats are allowed in user inputs.

4.3 Config or Code Example

Before

query = "db." + collectionName + ".find({username: '" + username + "'})"

After

query = { username: username }
db.collectionName.find(query)

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent NoSQL injection attacks. Least privilege limits the impact of a successful attack, while input validation blocks malicious data.

• Practice 1: Implement least privilege access control to limit database user permissions.
• Practice 2: Use robust input validation techniques to block unsafe characters and formats in user inputs.

4.5 Automation (Optional)

Automated code scanning tools can help identify vulnerable code patterns during development.

# Example using a static analysis tool
./static-analyzer --target /path/to/application --ruleset nosql_injection

5. Verification / Validation

Confirm the fix by re-running the initial injection test and verifying that it no longer succeeds. Perform a smoke test to ensure application functionality remains intact.

• Post-fix check: Re-run the original query with the malicious payload; the database should not return any unexpected results or error messages.
• Re-test: Use your scanner to confirm that the vulnerability is no longer detected.
• Smoke test: Verify key user actions, such as logging in and retrieving data, still function correctly.
• Monitoring: Monitor application logs for any unusual database query patterns or errors.

mongo --eval "db.adminCommand('ping')" # Should return a success message without error

6. Preventive Measures and Monitoring

Regular security baselines, CI/CD pipeline checks, and patch management are crucial for preventing NoSQL injection vulnerabilities.

• Baselines: Update your security baseline to include requirements for input validation and secure coding practices.
• Asset and patch process: Implement a regular patch management cycle for NoSQL databases and associated libraries.

7. Risks, Side Effects, and Roll Back

Changes may introduce compatibility issues or performance impacts. A rollback plan should be available to revert the changes if necessary.

• Risk or side effect 1: Parameterised queries might require code modifications that could affect application functionality.
• Risk or side effect 2: Input validation rules might inadvertently block legitimate user inputs, requiring adjustments.

8. References and Resources

• Vendor advisory or bulletin: Check your NoSQL database vendor’s website for specific security advisories related to injection vulnerabilities.
• NVD or CVE entry: https://nvd.nist.gov/vuln/detail/CVE-2019-17845 (example)
• Product or platform documentation relevant to the fix: Refer to your NoSQL database’s official documentation for guidance on parameterised queries and input validation techniques.