If you need to get a canisters controllers from within canister

[icme]

@Severin

They basically request canister_status of a different canister, and the error message contains the controllers which they then parse into principals

Here’s the solution I’m currently using.

Getting a Canister's Controller On-Chain

There’s actually a “hacky” way to do this (would be nice to have an officially supported way though) Here’s the hacky way: From your canister, call the management canister’s canister_status API, providing the canister id of the canister you wish to retrieve controller information. If you control the canister, you’ll be able to easily see the controllers. However, since the majority of the time you will not be the controller of the canister in question, it will return an error. Wrap your call …