net_proxy

why

a friend was in need of a proxy, for pop3 and smtp. so this is a network proxy for smtp, generic tcp but no http. input is plain, output tls. enjoy.

why no http?

because http proxies exist on mass. in fact if you look for "smtp proxy" dozens of http proxies show up and no single smtp one.

what does it do?

for every "route" defined in the config file, it creates a little server that listens for incomming connections and creates a sort of forwarding worker connection. the incomming traffic is supposed to be unencrypted while the outgoing traffic will be tls encrypted. tcp is a generic type which works for most kinds of protocols while smtp is a bit more advanced specifically for smtp connections.

why no incomming tls?

there's really only 3 reasons for you to run this tool:

• you have some ancient software incapable of handling proper, modern secure tls. just let this tool handle it then tbh, as a proxy on the same machine
• you run this as a proxy, on the same machine for other reasons
• you somehow came up with an even more questionable use for this software

how to setup

in the config file (config.json),

• smtp-data-limit is the amount of bytes a single smtp message may contain.
• smtp-timeout is the smtp timeout in seconds.
• smtp-max-recipients is the maximum allowed amount of recipients of an email forwarded. I think it's pretty obvious. routes is an array of routes (roaring applause from the audience reading this) where each route defines a server listening to "port-in", and forwards the traffic to "destination" at "port-out", using either type "smtp" or "tcp". again, incomming traffic is plain, outgoing traffic is tls encrypted.

disclaimer

this is highly questionable MacGuffin I wrote as a fun little go exercise a while ago and decided to put up here. so if you need it, that means you're running insecure or outdated (and therefore insecure) software but if you feel like switching to something else would be a huge hussle, feel free to use this software provided as is :) and have fun