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Thank you Benjamin,
According to OpenSSL , aNULL stands for no-authentication.
NULL-ciphers that you mention would be part of eNULL group, that offer no encryption.
Does it mean that all 3 default protocols of TLS 1.3 offer no authentication (because they are listed under command
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
Thank you,
Yury
From: Benjamin Kaduk <bkaduk@xxxxxxxxxx>
Sent: Thursday, September 3, 2020 5:12 PM To: Yury Mazin <ymazin@xxxxxxxxxxxx> Cc: openssl-users@xxxxxxxxxxx <openssl-users@xxxxxxxxxxx> Subject: [EXTERNAL] - Re: Question about TLS 1.3 and openssl -cipher aNULL option On Thu, Sep 03, 2020 at 11:45:28PM +0000, Yury Mazin via openssl-users wrote:
> Hello, > > We have a server was originaly using OpenSSL 1.0.2h. > Server is configured to use SSL ciphers as following > ALL:!aNULL:!ADH:!EDH:!eNULL:!EXPORT > When openssl client tries to connect to this server with command > openssl s_client -connect localhost:8101-cipher aNULL > it fails, because any aNULL ciphers are not available per server configuration. > We have now upgraded server to use OpenSSL 1.1.1f. > The current behavior is this: client can connect using the same command > openssl s_client -connect localhost:8101 -cipher aNULL > or > openssl s_client -tls1_3 -connect localhost:8101 -cipher aNULL > > while the same connect attempt using TLS1.2 protocol would still fail > > openssl s_client -tls1_2 -connect localhost:8001-cipher aNULL > > Would the fact that I can connect to the server using TLS 1.3 using the following command (specifically, using -cipher aNULL, while server is configured to exclude all aNULL cipher suites) considered a security violation? > > openssl s_client -tls1_3 -connect localhost:8001 -cipher aNULL > > Also, if this a security violation, how this can be addressed in the server configuration? > Lastly, if this is not a security violation, please explain. It is not a security violation, because you are using TLS 1.3 ciphers, and there are not any NULL-encryption TLS 1.3 ciphers. Configuration of TLS 1.3 ciphers and ciphers for previous versions of TLS are separate (since, at a protocol level, they serve different roles). See the documentation for s_client/s_server -ciphersuites for more information about TLS 1.3 ciphers. -Ben |
