Mmm. But how does the package registry know which signing keys to trust from you? You can't just log in and upload a signing key because that means that anyone who stole your 2FA will log in and upload their own signing key, and then sign their payload with that.

I guess having some cool down period after some strange profile activity (e.g. you've suddenly logged from China instead of Germany) before you're allowed to add another signing key would help, but other than that?

Supporting Passkeys would improve things; not allowing releases for a grace period after adding new signing keys and sending notifications about this to all known means of contact would improve them some more. Ultimately, there will always be ways; this is as much a people problem as it is a technical one.

I suppose you'd register your keys when signing up and to change them, you'd have some recovery passphrase, kind of like how 2FA recovery codes work. If somebody can phish _that_, congratulations.

That still requires stealing your 2FA again. In this attack they compromised a one-time authenticator code, they'd have to do it a second time in a row, and the user would be looking at a legitimate "new signing key added" email alongside it.