Validation of X.509 certificates is essential to create secure SSL/TLS sessions not vulnerable to man-in-the-middle attacks. 

The certificate chain validation includes these steps:

* The certificate is issued by its parent Certificate Authority or the root CA trusted by the system.
* Each CA is allowed to issue certificates.
* Each certificate in the chain is not expired.

This rule raises an issue when an implementation of X509TrustManager is not controlling the validity of the certificate (ie: no exception is raised). Empty implementations of the ``++X509TrustManager++`` interface are often created to disable certificate validation. The correct solution is to provide an appropriate trust store.

== Noncompliant Code Example

----
class TrustAllManager implements X509TrustManager {

    @Override
    public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {  // Noncompliant, nothing means trust any client
    }

    @Override
    public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException { // Noncompliant, this method never throws exception, it means trust any server
        LOG.log(Level.SEVERE, ERROR_MESSAGE);
    }

    @Override
    public X509Certificate[] getAcceptedIssuers() {
        return null;
    }
}
----

== See

* https://www.owasp.org/index.php/Top_10-2017_A6-Security_Misconfiguration[OWASP Top 10 2017 Category A6] - Security Misconfiguration
* https://cwe.mitre.org/data/definitions/295.html[MITRE, CWE-295] - Improper Certificate Validation
* https://wiki.sei.cmu.edu/confluence/x/hDdGBQ[CERT, MSC61-J.] - Do not use insecure or weak cryptographic algorithms

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