Disable TLS Renegociation ?

[Sean Mullan]

On 4/23/24 5:54 AM, Simon Bernard wrote:
>
> Hi,
>
> I'm implementing coaps+tcp (Coap over TLS) for LWM2M protocol.
>
> In this context, I would like to disable TLS renegotiation because :
>
>   * by the past we faces security issue about it
>   * it doesn't really make sense to use it  with those protocols
>     (better to not increase the attack surface for nothing)
>   * (TLS) / (DTLS) Profiles for the Internet of Things strongly
>     recommend (mandate?) to disable it :
>     https://datatracker.ietf.org/doc/html/rfc7925#section-17
>
> So what is the right way to deactivate it  (for SslSocket and 
> SslEngine) ? I searched for a programmatically way to do that (maybe 
> using SSLParam) but didn't find it.
>
> Only find a system properties : 
> |jdk.tls.rejectClientInitiatedRenegotiation| to /"Rejects 
> client-initiated renegotiation on the server side. If this system 
> property is |true|, then the server will not accept client initiated 
> renegotiations and will fail with a fatal |handshake_failure| alert. 
> Rejects server-side client-initialized renegotiation."
>
> /But the documentation says :///"This system property is currently 
> used by the JSSE implementation, but it is not guaranteed to be 
> examined and used by other implementations. If it is examined by 
> another implementation, then that implementation should handle it in 
> the same manner as the JSSE implementation does. There is no guarantee 
> the property will continue to exist or be of the same type (system or 
> security) in future releases."/
>
> (source : 
> https://docs.oracle.com/en/java/javase/21/security/java-secure-socket-extension-jsse-reference-guide.html#GUID-A41282C3-19A3-400A-A40F-86F4DA22ABA9)
>
> Which sounds not so good and is only documented for java 17 and 21 (I 
> just checked LTS version), not java 8 or 11. /
> /
>
That property is supported in JDK 8 and up. It was originally introduced 
in JDK 8. It is supported in the SunJSSE provider. If you are using a 
different JSSE provider, it may not be supported. But most (all?) 
implementations of OpenJDK probably include the SunJSSE provider.

The docs for JDK 8 and 11 should document this property - I'll file an 
issue to have them updated.

--Sean
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