Enable SSLv3 in nginx on debian server

Question

For some demonstration on HTTPS weakness, I'd like to enable SSLv3 on one sub domain of my webserver. I use nginx 1.12.2 on debian 8, and already tried to add the following line

ssl_protocols SSLv2 SSLv3 TLSv1 TLSv1.1 TLSv1.2;

and then a sudo service nginx restart, but ssllabs still shows SSL as disabled (with the clear-cache option).

Apparently the version of openssl I have supports SSLv3 (openssl ciphers -v), so I don't understand why SSLv3 isn't enabled.

Thanks !

Answer 1

Try this command to compare with SSLLabs result :

openssl s_client -ssl3 -connect youserver:443

If the handshake is OK, you probably need to configure the cipers in the NGINX config.

Answer 2

With new versions of openssl, configurations goes in exclusion-way. You can use this command to test SSLv3 protocol

 openssl s_client -connect youserver:443 -no_tls1_2 -no_tls1_1 -no_tls1

But the best way to ensure wich versions of SSL/TLS are working on the remote werver is using NMAP:

nmap -sV --script ssl-enum-ciphers -p 443 youserver

Nmap output will point you in the right direction, because it describes the version working protocols and every available cipher.

PORT    STATE SERVICE   VERSION
443/tcp open  ssl/https nginx
|_http-server-header: nginx
| ssl-enum-ciphers:
|   TLSv1.0:
|     ciphers:
|       TLS_DHE_RSA_WITH_AES_128_CBC_SHA (dh 1024) - A
|       TLS_DHE_RSA_WITH_AES_256_CBC_SHA (dh 1024) - A
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (secp256r1) - A
|     compressors:
|       NULL
|     cipher preference: client
|     warnings:
|       Key exchange (dh 1024) of lower strength than certificate key
|   TLSv1.1:
|     ciphers:
|       TLS_DHE_RSA_WITH_AES_128_CBC_SHA (dh 1024) - A
|       TLS_DHE_RSA_WITH_AES_256_CBC_SHA (dh 1024) - A
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (secp256r1) - A
|     compressors:
|       NULL
|     cipher preference: client
|     warnings:
|       Key exchange (dh 1024) of lower strength than certificate key
|   TLSv1.2:
|     ciphers:
|       TLS_DHE_RSA_WITH_AES_128_CBC_SHA (dh 1024) - A
|       TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 (dh 1024) - A
|       TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (dh 1024) - A
|       TLS_DHE_RSA_WITH_AES_256_CBC_SHA (dh 1024) - A
|       TLS_DHE_RSA_WITH_AES_256_CBC_SHA256 (dh 1024) - A
|       TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 (dh 1024) - A
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (secp256r1) - A
|     compressors:
|       NULL
|     cipher preference: client
|     warnings:
|       Key exchange (dh 1024) of lower strength than certificate key
|_  least strength: A

Hope that helps