OCSP Stapling Without Resolver

Gixy Check ID: ssl_stapling_without_resolver

When ssl_stapling on; is in effect for an SSL server but no resolver directive is reachable in scope, nginx has no way to look up the OCSP responder hostname. The stapling machinery silently falls back to "no stapled response," clients run their own OCSP queries, the TLS handshake adds round trips, and the security/performance gains of stapling are lost. nginx logs a warning to error.log at startup, but those warnings are easy to miss.

This is a pure configuration bug — there is no legitimate setup where you would enable ssl_stapling without configuring a resolver.

Bad Example

server {
    listen 443 ssl;
    server_name example.com;

    ssl_certificate     /etc/ssl/certs/example.com.pem;
    ssl_certificate_key /etc/ssl/private/example.com.key;

    ssl_stapling on;
    ssl_stapling_verify on;
}

Or inherited from http {} without any server providing a resolver:

http {
    ssl_stapling on;          # inherited by every server below

    server {
        listen 443 ssl;
        ssl_certificate     /etc/ssl/certs/example.com.pem;
        ssl_certificate_key /etc/ssl/private/example.com.key;
        # ← no resolver visible anywhere up the chain
    }
}

Good Example

Put the resolver at http level so every SSL server inherits it:

http {
    resolver 1.1.1.1 8.8.8.8 valid=300s ipv6=off;
    resolver_timeout 5s;

    ssl_stapling on;
    ssl_stapling_verify on;

    server {
        listen 443 ssl;
        server_name example.com;

        ssl_certificate     /etc/ssl/certs/example.com.pem;
        ssl_certificate_key /etc/ssl/private/example.com.key;
    }
}

Pair ssl_stapling on with ssl_stapling_verify on and a fast resolver_timeout so a slow OCSP lookup never stalls the handshake.

What this check does not flag

• ssl_stapling off; — stapling is intentionally disabled, no resolver needed.
• Non-SSL servers (listen 80;) — stapling is irrelevant.
• A server block that overrides with ssl_stapling off; even when http enables it globally.
• Servers where a resolver is reachable in any enclosing scope, including via include.