Wow, what a bug. I expect the exploit is literally as simple as trying to ssh in as a user with the password has ‘*’ in /etc/shadow and typing anything as the password.
To the extent that systems that are configured in the vulnerable manner exist in the wild, I’m surprised they weren’t exploited years ago by trivial ssh bots.
P.S. Wow, I’m reminded of just how awful traditional UNIX-y C APIs and code are.
P.P.S. The musl code in question is nuts. The API it implements is awful. Seriously, here’s the manpage:
How do you break back into your digital life? You wake up in a strange place. Something happened. Everything's gone. No wallet/keys/smartphone/tablet/laptop. How would you get back into your digital life given only a laptop with access to the Internet, unless something, somewhere is passwordauthenticate=yes.
I walk to my pc and type ssh-keygen. If i can’t do that I’ve got bigger problems. “I must be able to recover remotely using a memorised credential” is a terrible requirement.
Yeah your vault has password authentication. Your password manager in other words. Your vault is where you store your private ssh keys, and or the passwords for the keys.
Remotely: An encrypted file with a seed / master passwords to all the other data, published under a public url you can remember, but not linked anywhere and not listed.
Locally: Same, but printed out, laminated, in a safe place with other documents.
Seems slightly confusing that the OpenSSH release notes page says:
> This release contains a critical security workaround that affects Linux systems that use the musl libc and PAM disabled.
But that there's nothing about it on their security page.
Even if it's not technically a bug in their code, the fact that they've made a "critical" release to address it suggests that it should probably be listed on the security page as well. But maybe (hopefully) they just haven't updated the security page yet.
To the extent that systems that are configured in the vulnerable manner exist in the wild, I’m surprised they weren’t exploited years ago by trivial ssh bots.
P.S. Wow, I’m reminded of just how awful traditional UNIX-y C APIs and code are.
P.P.S. The musl code in question is nuts. The API it implements is awful. Seriously, here’s the manpage:
https://man.archlinux.org/man/crypt.3.en
You can’t call this function correctly. sshd’s “fix” is basically to assume that a too-short return is an error return instead of a success return.
PAM is also awful, but this is worse.
at this point the _last_ thing i care about is my email.
where am i? am i ok? how are my friends/loved ones?
once those are in place, it becomes clearer how to get back to "normal"
Locally: Same, but printed out, laminated, in a safe place with other documents.
You must present a key first after which you must enter a password.
> This release contains a critical security workaround that affects Linux systems that use the musl libc and PAM disabled.
But that there's nothing about it on their security page.
Even if it's not technically a bug in their code, the fact that they've made a "critical" release to address it suggests that it should probably be listed on the security page as well. But maybe (hopefully) they just haven't updated the security page yet.
So not a ssh issue but an issue specific to Linux using "musl libc without PAM".
At the bottom of that it says dropbear is unaffected.
> on debian, ubuntu, fedora or anything else with glibc? going through pam? dropbear? openbsd? you're fine
[0] https://sshhole.com/
[1] https://news.ycombinator.com/item?id=50378228