Command prompt to check TLS version required by a host - ssl

Question

Is there a command to check the TLS version required by a host site? Right now, the only way I know to check is by adjusting the max TLS version of my browser and checking if I can still access the site. However, I suspect there is a more sophisticated way to do this.

Answer 1

You can check using following commands.
For TLS 1.2:
openssl s_client -connect www.google.com:443 -tls1_2
For TLS 1.1:
openssl s_client -connect www.google.com:443 -tls1_1
For TLS 1:
openssl s_client -connect www.google.com:443 -tls1
If you get the certificate chain and the handshake then the TLS version is supported. If you don't see the certificate chain, and something similar to "handshake error" then its not.

Answer 2

From https://maxchadwick.xyz/blog/checking-ssl-tls-version-support-of-remote-host-from-command-line:
nmap ssl-enum-ciphers
Another option for checking SSL / TLS version support is nmap. nmap is not typically installed by default, so you’ll need to manually install it. Once installed you can use the following command to check SSL / TLS version support…
nmap --script ssl-enum-ciphers -p 443 www.google.com
nmap’s ssl-enum-ciphers script will not only check SSL / TLS version support for all versions (TLS 1.0, TLS 1.1, and TLS 1.2) in one go, but will also check cipher support for each version including giving providing a grade.

Answer 3

I like to use curl which can report a TLS version negotiation quite nicely.
For example, this tries to connect with TLS 1.1, which the server negotiates to upgrade to 1.2:
$ curl -Iiv --tlsv1.1 https://example.com
* Trying 192.168.205.11:443...
* TCP_NODELAY set
* Connected to example.com (192.168.205.11) port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* successfully set certificate verify locations:
* CAfile: /etc/ssl/certs/ca-certificates.crt
CApath: /etc/ssl/certs
* TLSv1.3 (OUT), TLS handshake, Client hello (1):
* TLSv1.3 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
* TLSv1.2 (IN), TLS handshake, Server finished (14):
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
* TLSv1.2 (OUT), TLS change cipher, Change cipher spec (1):
* TLSv1.2 (OUT), TLS handshake, Finished (20):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-RSA-AES256-GCM-SHA384
* ALPN, server accepted to use http/1.1
* Server certificate:
[...]
To forbid that the server upgrades the TLS version use the --tls-max option:
$ curl -Iiv --tlsv1.1 --tls-max 1.1 https://example.com
* Trying 192.168.205.11:443...
* TCP_NODELAY set
* Connected to example.com (192.168.205.11) port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* successfully set certificate verify locations:
* CAfile: /etc/ssl/certs/ca-certificates.crt
CApath: /etc/ssl/certs
* TLSv1.3 (OUT), TLS alert, internal error (592):
* error:141E70BF:SSL routines:tls_construct_client_hello:no protocols available
* Closing connection 0
curl: (35) error:141E70BF:SSL routines:tls_construct_client_hello:no protocols available
In this case, the connection fails because the client does not offer any TLS version above 1.1, but the server does not accept any version below 1.2. If used like this, the output is very similar to the openssl_client output.

Answer 4

It seems the most sophisticated way is to check like this for each version:
openssl s_client -connect : -

Answer 5

Nmap has very convenient TLS version and ciphersuite checking NSE script. All in one, multiplatform too: https://nmap.org/nsedoc/scripts/ssl-enum-ciphers.html