Created
September 4, 2025 20:00
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nginx mail proxy in front of mta submission server (no auth) with STARTTLS required
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| user nginx; | |
| worker_processes auto; | |
| error_log /var/log/nginx/error.log info; | |
| pid /run/nginx.pid; | |
| include /usr/share/nginx/modules/*.conf; | |
| env RELAY_HOST; | |
| env RELAY_PORT; | |
| events { | |
| worker_connections 1024; | |
| } | |
| http { | |
| access_log /var/log/nginx/access.log; | |
| log_not_found off; | |
| perl_modules /etc/nginx/perl/lib; | |
| perl_require auth.pm; | |
| server { | |
| listen 80 default_server; | |
| listen [::]:80 ipv6only=on default_server; | |
| server_name _; | |
| root /dev/null; # No static content served | |
| location /auth { | |
| perl auth::handler; | |
| } | |
| } | |
| } | |
| mail { | |
| server_name mail.example.com; | |
| auth_http 127.0.0.1:80/auth; | |
| smtp_capabilities PIPELINING 8BITMIME ENHANCEDSTATUSCODES "SIZE 10240000" SMTPUTF8 CHUNKING ETRN VRFY; | |
| xclient on; | |
| proxy_pass_error_message on; | |
| ssl_trusted_certificate /etc/nginx/ssl/ca.crt; | |
| ssl_certificate /etc/nginx/ssl/server.crt; | |
| ssl_certificate_key /etc/nginx/ssl/server.nopass.key; | |
| server { | |
| listen 25; | |
| listen 465 ssl; | |
| protocol smtp; | |
| smtp_auth none; | |
| starttls on; | |
| } | |
| server { | |
| listen 587; | |
| protocol smtp; | |
| smtp_auth none; | |
| starttls only; | |
| } | |
| } |
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| package auth; | |
| use strict; | |
| use warnings; | |
| use Socket; | |
| use nginx; | |
| sub handler { | |
| my $r = shift; | |
| # Require STARTTLS if Auth-Method is "none" | |
| # nginx handles ensuring TLS for other methods (e.g. "plain", "login", "cram-md5") | |
| if ($r->header_in("Auth-Method") eq "none" && $r->header_in("Auth-SSL") || "" ne "on") { | |
| my $max_attempts = 3; | |
| my $attempt = ($r->header_in("Auth-Login-Attempt") || 0) + 0; | |
| if ($attempt > $max_attempts) { | |
| $r->header_out("Auth-Status", "Too many errors"); | |
| $r->header_out("Auth-Error-Code", "503"); | |
| } else { | |
| $r->header_out("Auth-Status", "Must issue a STARTTLS command first"); | |
| $r->header_out("Auth-Error-Code", "530 5.7.0"); | |
| $r->header_out("Auth-Wait", "1"); | |
| } | |
| return DECLINED; | |
| } | |
| if (exists $ENV{RELAY_HOST} && $ENV{RELAY_PORT}) { | |
| my $address = inet_ntoa(inet_aton($ENV{RELAY_HOST})); | |
| $r->header_out("Auth-Status", "OK"); | |
| $r->header_out("Auth-Server", $address); | |
| $r->header_out("Auth-Port", $ENV{RELAY_PORT}); | |
| return OK; | |
| } | |
| return DECLINED; | |
| } | |
| 1; |
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