There is nothing S390 specific in this, it is a requirement to use GCM based 
ciphers for TLS when running in a FIPS validated environment.  The check will 
be cheaper than trying to avoid it by conditioning on FIPS mode -- hence it’s 
unconditional.

 

 

Pauli

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Oracle

Dr Paul Dale | Cryptographer | Network Security & Encryption 

Phone +61 7 3031 7217

Oracle Australia

 

From: Dmitry Belyavsky [mailto:beld...@gmail.com] 
Sent: Friday, 14 September 2018 8:41 PM
To: openssl-users@openssl.org
Subject: Re: [openssl-users] Limit the number of AES-GCM keys allowed in TLS

 

Hello,

 

Sorry, I've just found similar checks in all _CGM functions. 

 

On Fri, Sep 14, 2018 at 1:30 PM Dmitry Belyavsky <HYPERLINK 
"mailto:beld...@gmail.com"beld...@gmail.com> wrote:

Dear Paul,

 

Could you please clarify? 

The code seems to be related to s390 platform. Do I miss something?

 

On Thu, Sep 13, 2018 at 1:55 AM Paul Dale <HYPERLINK 
"mailto:paul.d...@oracle.com"paul.d...@oracle.com> wrote:

I wasn’t aware of other national standards requiring a similar check.

 

I made the change in the AES-GCM code because FIPS demands the check be inside 
the FIPS boundary.  I’d have preferred to make it in the TLS layer, but that 
mustn’t be inside the FIPS boundary.  My understanding is that TLS catches this 
case earlier and thus the test can never pass.

 

I don’t think dropping the check down into the algorithm implementations makes 
sense.  A more generic mechanism at the EVP would.

 

 

 

Pauli

-- 

Oracle

Dr Paul Dale | Cryptographer | Network Security & Encryption 

Phone +61 7 3031 7217

Oracle Australia

 

From: Dmitry Belyavsky [mailto:HYPERLINK 
"mailto:beld...@gmail.com"beld...@gmail.com] 
Sent: Wednesday, 12 September 2018 7:02 PM
To: HYPERLINK "mailto:openssl-users@openssl.org"openssl-users@openssl.org
Subject: [openssl-users] Limit the number of AES-GCM keys allowed in TLS

 

Hello,

 

The issue https://github.com/openssl/openssl/pull/7129 has introduced a 
possibility to limit the amount of TLS records processed without key changing 
as required by FIPS.

 

We in Russia have limitations with the same semantics applicable to Russian 
GOST TLS ciphersuites 
(https://datatracker.ietf.org/doc/draft-smyshlyaev-tls12-gost-suites/) so I 
think that this mechanism is very useful. 

 

The current implementation is done at EVP level, and it seems suboptimal 
because of the following reasons:

- If the AES implementation is provided via engine, not by OpenSSL itself, the 
limitation can be avoided

- the limitation has been made too generic

- the implementation seems to be AEAD-specific. 

 

So does not it make sense to provide this limitation at least at the 
ciphersuite level? It can provide more straightforward way to manage such 
limitations.


Thank you!

 

-- 

SY, Dmitry Belyavsky

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