@cwebber @cj Something that should illustrate it quite well is that you can't actually implement a RPC interaction without a runtime check, in a sensibly-typed language. At least not without unsafe code.

That's because the communication primitive you use carries unstructured data (say, bytes) and to turn it into structured data you need to parse it: the parser is already a form of runtime check, as it will reject malformed data.

Depending on how your RPC system is engineered, you'll then do some further, semantic analysis on the structured data, like validating it conforms to a given schema/datatype, in the process of converting it to a more specific type.

(Sorry for the delete&repost, this was accidentally made followers-only.)

@garbados Opposing view: programming is a lot easier than the industry would have you believe, but they are hobbled by antiquated software engineering practices and programming technologies.

Disclaimer: I definitely agree with the point on error margins (and that it is ridiculous that we tolerate those), and that software isn't getting better (i.e. more secure, reliable or efficient).
Also, I'm a PL & infosec researcher, so I might be highly biased.

OK, I have no words for this: https://github.com/systemd/systemd/issues/6237

If your username doesn't match what Poettering expects usernames to be (and doesn't seem to be documented anywhere, but `[a-zA-Z]+` is *probably* safe?), then systemd will happily run your user services as root.

Reply: not-a-bug, don't use “invalid usernames”...

Paging @KitRedgrave, @mwlucas and @phessler for hilarity.