[EXTERNAL] - Re: Question about TLS 1.3 and openssl -cipher aNULL option

[Yury Mazin]

Hello,

I have a question based on the response provided to me:

My question is why following openssl commands (version 1.1.1f)  return those TLSv1.3 ciphers as offering no authentication and no encryption?



C:\OpenText\iHub20.4-29324643-250C200831\ihub\modules\BIRTiHub\iHub\bin>openssl  ciphers -v -s NULL

TLS_AES_256_GCM_SHA384  TLSv1.3 Kx=any      Au=any  Enc=AESGCM(256) Mac=AEAD

TLS_CHACHA20_POLY1305_SHA256 TLSv1.3 Kx=any      Au=any  Enc=CHACHA20/POLY1305(256) Mac=AEAD

TLS_AES_128_GCM_SHA256  TLSv1.3 Kx=any      Au=any  Enc=AESGCM(128) Mac=AEAD



C:\OpenText\iHub20.4-29324643-250C200831\ihub\modules\BIRTiHub\iHub\bin>openssl  ciphers -v -s eNULL

TLS_AES_256_GCM_SHA384  TLSv1.3 Kx=any      Au=any  Enc=AESGCM(256) Mac=AEAD

TLS_CHACHA20_POLY1305_SHA256 TLSv1.3 Kx=any      Au=any  Enc=CHACHA20/POLY1305(256) Mac=AEAD

TLS_AES_128_GCM_SHA256  TLSv1.3 Kx=any      Au=any  Enc=AESGCM(128) Mac=AEAD



C:\OpenText\iHub20.4-29324643-250C200831\ihub\modules\BIRTiHub\iHub\bin>openssl  ciphers -v -s aNULL

TLS_AES_256_GCM_SHA384  TLSv1.3 Kx=any      Au=any  Enc=AESGCM(256) Mac=AEAD

TLS_CHACHA20_POLY1305_SHA256 TLSv1.3 Kx=any      Au=any  Enc=CHACHA20/POLY1305(256) Mac=AEAD

TLS_AES_128_GCM_SHA256  TLSv1.3 Kx=any      Au=any  Enc=AESGCM(128) Mac=AEAD
________________________________
From: Yury Mazin <ymazin at opentext.com>
Sent: Friday, September 4, 2020 12:43 PM
To: openssl-users at openssl.org <openssl-users at openssl.org>
Subject: Re: [EXTERNAL] - Re: Question about TLS 1.3 and openssl -cipher aNULL option

Viktor,

Thank you for clarifying it.

Yury
________________________________
From: openssl-users <openssl-users-bounces at openssl.org> on behalf of Viktor Dukhovni <openssl-users at dukhovni.org>
Sent: Friday, September 4, 2020 12:10 PM
To: openssl-users at openssl.org <openssl-users at openssl.org>
Subject: Re: [EXTERNAL] - Re: Question about TLS 1.3 and openssl -cipher aNULL option

On Fri, Sep 04, 2020 at 07:00:01PM +0000, Yury Mazin via openssl-users wrote:

> Thank you Benjamin,
>
> According to OpenSSL , aNULL stands for no-authentication.

Specifically, SSL 3.0 through TLS 1.2 ciphers in which the server and
client exchange no certificates, and the TLS handshake consists largely
of an unsigned anonymous ephemeral DH or ECDH key exchang.

TLS 1.3 dropped support for anonymous DH and ECDH.  Server certificates
are *required.  And the all-in-one ciphersuites of TLS <= 1.2, are
replaced with separately negotiated components.  As a result of which,
in OpenSSL 1.1.1 and later, they are controlled via a different set of
APIs and command-line options.

Specifically, in your case, the "-ciphers aNULL" option only applies
to TLS <= 1.2

> Does it mean that all 3 default protocols of TLS 1.3 offer no
> authentication

No.  None of them "support no authentication" (which is not even strictly
true, it is the protocol that does not support "no authentication",
the TLS 1.3 ciphers are simply silent re certificate algorithm selection),
but the "-cipher aNULL" is simply not used when TLS 1.3 is negotiated,
so your question is makes incorrect assumptions to reach its tentative
conclusions.

--
    Viktor.
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