1. Introduction
Digest Authentication Detected refers to the use of HTTP Digest authentication on a web page. This is considered less secure than modern alternatives like Basic Authentication with TLS, and can be vulnerable to replay attacks if not implemented correctly. Web servers and applications are commonly affected. A successful exploit could lead to credential theft and unauthorized access. Confidentiality, integrity, and availability may all be impacted.
2. Technical Explanation
Digest Authentication is an HTTP authentication scheme that uses a hash of the user’s password instead of sending it in plain text. However, vulnerabilities can arise from weak nonce generation or improper handling of the authentication process. An attacker could potentially intercept and replay the authentication exchange to gain access. There are no known CVEs specifically for detecting Digest Authentication; however, weaknesses in its implementation may be covered by other standards like OWASP. A realistic example involves an attacker capturing network traffic containing the authentication exchange and then replaying it using tools like curl or Burp Suite.
- Root cause: The use of a less secure authentication method than modern alternatives.
- Exploit mechanism: An attacker intercepts and replays the Digest Authentication exchange to gain unauthorized access.
- Scope: Web servers and applications using HTTP Digest Authentication.
3. Detection and Assessment
To confirm if a system is vulnerable, check for the presence of ‘Digest’ in the WWW-Authenticate header during an authentication attempt. A thorough method involves analyzing network traffic to identify the authentication exchange.
- Quick checks: Use browser developer tools or curl with verbose output to inspect HTTP headers when accessing a protected resource.
- Scanning: Nessus and other vulnerability scanners may flag Digest Authentication as an informational finding, but specific signature IDs vary.
- Logs and evidence: Web server logs may show authentication attempts using the ‘Digest’ scheme.
curl -v https://example.com/protected_resource4. Solution / Remediation Steps
The recommended solution is to disable Digest Authentication in favor of more secure alternatives.
4.1 Preparation
- Ensure you have alternative authentication methods configured (e.g., Basic Authentication with TLS, OAuth). A roll back plan is to restore the original configuration file.
- A change window may be required depending on the environment and impact of disabling authentication. Approval from system owners may be needed.
4.2 Implementation
- Step 1: Edit your web server configuration file (e.g., Apache httpd.conf, Nginx nginx.conf).
- Step 2: Locate the section configuring authentication for the affected resource(s).
- Step 3: Remove or comment out any lines referencing ‘Digest’ authentication.
- Step 4: Restart your web server to apply the changes.
4.3 Config or Code Example
Before
AuthType Digest
AuthName "Restricted Area"
AuthDigestRealm /example.com/protected_resourceAfter
# AuthType Digest
# AuthName "Restricted Area"
# AuthDigestRealm /example.com/protected_resource4.4 Security Practices Relevant to This Vulnerability
Several security practices can help prevent this issue. Least privilege reduces the impact of compromised credentials. Secure defaults ensure authentication is configured securely from the start. Patch cadence ensures systems are up-to-date with the latest security fixes.
- Practice 1: Implement least privilege to limit access to sensitive resources.
- Practice 2: Use secure defaults for all authentication configurations.
4.5 Automation (Optional)
No automation is provided as the configuration changes are specific to each web server and environment.
5. Verification / Validation
Confirm the fix by attempting an authentication request and verifying that Digest Authentication is no longer offered. Re-run the earlier detection method to confirm the issue is resolved. Perform a simple service smoke test to ensure functionality remains intact.
- Post-fix check: Use curl with verbose output; the WWW-Authenticate header should not include ‘Digest’.
- Re-test: Re-run the earlier detection method (browser developer tools or curl) and confirm that Digest Authentication is no longer present in the headers.
- Smoke test: Attempt to access a protected resource using an alternative authentication method to ensure it still functions correctly.
- Monitoring: Monitor web server logs for any unexpected authentication errors.
curl -v https://example.com/protected_resource6. Preventive Measures and Monitoring
Update security baselines to disallow Digest Authentication. Implement CI/CD pipeline checks to prevent insecure configurations from being deployed. Establish a regular patch or configuration review cycle to identify and address vulnerabilities promptly.
- Baselines: Update your web server security baseline to explicitly prohibit the use of Digest Authentication.
- Pipelines: Add checks in your CI/CD pipeline to scan for insecure authentication configurations.
- Asset and patch process: Review web server configurations regularly as part of a vulnerability management program.
7. Risks, Side Effects, and Roll Back
Disabling Digest Authentication may require updating client applications or configuring alternative authentication methods. A roll back plan is to restore the original configuration file and restart the web service.
- Risk or side effect 1: Client applications that rely on Digest Authentication may need to be updated.
- Roll back: Restore the original web server configuration file and restart the service.
8. References and Resources
- Vendor advisory or bulletin: Check your web server vendor’s documentation for specific guidance on disabling Digest Authentication.
- NVD or CVE entry: No specific CVE exists for detecting Digest Authentication, but review related standards like OWASP.
- Product or platform documentation relevant to the fix: https://developer.mozilla.org/en-US/docs/Web/HTTP/Authentication