Module ngx_stream_ssl_preread_module

• Example Configuration
• Directives
• ssl_preread
• Embedded Variables

The ngx_stream_ssl_preread_module module (1.11.5) allows extracting information from the ClientHello message without terminating SSL/TLS, for example, the server name requested through SNI or protocols advertised in ALPN. This module is not built by default, it should be enabled with the --with-stream_ssl_preread_module configuration parameter.

Example Configuration

Selecting an upstream based on server name:

map $ssl_preread_server_name $name {
    backend.example.com      backend;
    default                  backend2;
}

upstream backend {
    server 192.168.0.1:12345;
    server 192.168.0.2:12345;
}

upstream backend2 {
    server 192.168.0.3:12345;
    server 192.168.0.4:12345;
}

server {
    listen      12346;
    proxy_pass  $name;
    ssl_preread on;
}

Selecting an upstream based on protocol:

map $ssl_preread_alpn_protocols $proxy {
    ~\bh2\b           127.0.0.1:8001;
    ~\bhttp/1.1\b     127.0.0.1:8002;
    ~\bxmpp-client\b  127.0.0.1:8003;
}

server {
    listen      9000;
    proxy_pass  $proxy;
    ssl_preread on;
}

Selecting an upstream based on SSL protocol version:

map $ssl_preread_protocol $upstream {
    ""        ssh.example.com:22;
    "TLSv1.2" new.example.com:443;
    default   tls.example.com:443;
}

# ssh and https on the same port
server {
    listen      192.168.0.1:443;
    proxy_pass  $upstream;
    ssl_preread on;
}

Directives

Enables extracting information from the ClientHello message at the preread phase.

Embedded Variables

$ssl_preread_protocol

the highest SSL protocol version supported by the client (1.15.2)

$ssl_preread_server_name

server name requested through SNI

$ssl_preread_alpn_protocols

list of protocols advertised by the client through ALPN (1.13.10). The values are separated by commas.