Recently, a log injection vulnerability (CVE-2023-6484) was discovered in Keycloak's WebAuthn Authentication Mode. This vulnerability enables an attacker to inject a text string into the logs through the authentication form, possibly compromising the integrity of log data. In this post, we will delve deeper into the details of this flaw, analyze its potential impact, and suggest ways to mitigate it.

Background

Keycloak is one of the most popular open-source Identity and Access Management (IAM) solutions in the market. It is widely used for securing applications by providing features such as Single Sign-On, Identity Brokering, and Social Login. You can find more information on Keycloak on their official website [1]. WebAuthn is a web standard that enables passwordless authentication on web applications with the help of PublicKeyCredential and Authenticator [2].

Description of the Vulnerability

This flaw arises from the fact that the authentication forms were not properly sanitized when WebAuthn authentication mode is used. Consequently, an attacker can inject arbitrary text strings into the log, which might lead to log pollution or potentially harmful outcomes in certain scenarios.

Here is the code snippet where this vulnerability lies within Keycloak's WebAuthn Authenticator Module [3]:

authenticate(AuthenticationFlowContext context) {
    ...
    // vulnerable code
    String userSuppliedUsername = context.getHttpRequest().getDecodedFormParameters().getFirst("username");
    ...
}

As we can see above, the userSuppliedUsername variable is retrieved from the HTTP request's decoded form parameters without proper input validation and sanitization.

Exploit Details

To exploit this vulnerability, an attacker could craft a request where the "username" parameter contains a specially crafted text string that pollutes the log file.

For example, if the attacker sends a request with the following string as the "username" parameter

hello");DROP TABLE Users; --

The log file might look something like this

Date | Event | User | Message
-----|-------|------|--------
...  | ...   | ...  | ...
2023-02-01 | Authentication | hello");DROP TABLE Users; -- | Authentication failed.

In this case, the integrity of the logs has been compromised as the timestamp, event, and original user information have been altered.

Mitigations

Keycloak project has already been informed about this vulnerability and is expected to release a patch soon. Meanwhile, administrators can implement the following recommendations to mitigate the risks:

Regularly monitor log files for any anomalies or injected text strings.

2. Implement a log monitoring and management solution to ensure prompt identification of potential log injection attacks.
3. As a temporary fix, validate and sanitize user input in application code before allowing it to interact with Keycloak's authentication system.

Conclusion

While this vulnerability (CVE-2023-6484) may only have a minor impact on the logs' integrity, it still showcases the importance of regularly auditing application code and implementing security best practices to ensure a secure environment. Stay tuned for the upcoming patch release and make sure to update your Keycloak deployments as soon as possible to prevent potential exploitation of this flaw.

References

[1] Keycloak Official Website: https://www.keycloak.org
[2] WebAuthn: https://www.w3.org/TR/webauthn/
[3] Keycloak WebAuthn Authenticator Repository: https://github.com/keycloak/keycloak/blob/master/services/src/main/java/org/keycloak/authentication/authenticators/browser/WebAuthnAuthenticator.java

Timeline

Published on: 04/25/2024 16:15:09 UTC
Last modified on: 06/12/2024 10:09:42 UTC