Stop "Allow Incoming Connections?" Popups When Developing on macOS

• 2024-03-02
• macos
• tip
• development
• meta

These days, I'm back to developing almost entirely on macOS. When I was working on the implementation of this site, it was starting to get quite grating that every time I ran cargo run, macOS would pop up a window that says "Allow Incoming Connections?". I had to click "Allow" every single time I changed the code and re-ran it.

In general, I know why this happens: the firewall is enabled, and Cargo doesn't sign executables, so every time I produced a new executable, it was nEw AnD sCaRy. Adding the executable to the list of trusted apps doesn't help for exactly that reason (in fact, that's all that clicking "Allow" does). The problem is, I want the firewall to be enabled.

I tried a few things to stop this, including adding my terminal emulator as a developer tool in the Security & Privacy preference pane, which allows it to "run software locally that does not meet the system's security policy". That doesn't extend to running executables that need to accept incoming connections, apparently (at least for WezTerm).

It turns out that in my particular case, though, there's an easy solution: I had totally overlooked that my program was binding to 0.0.0.0:<port>. For local development, that's unnecessary. I changed it to 127.0.0.1:<port>, and the popups blissfully disappeared.