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Message-ID: <CAH8yC8mRVMKz=zxvV0mz+fonZ54WkN_vjy5qjdoQACT+7xX4pA@mail.gmail.com>
Date: Fri, 6 Nov 2026 16:39:24 -0500
From: Jeffrey Walton <noloader@...il.com>
To: musl@...ts.openwall.com
Subject: Re: OpenSSH password auth bypass analysis [was: Re: 
 Advisory for OpenSSH+musl users]

Hi Rich,

One comment on Item (5) below.

On Fri, Nov 6, 2026 at 1:55 PM Rich Felker <dalias@...c.org> wrote:
>
> [...]
> 5. Having a failure token not match any password is contingent on the
> caller of crypt passing the correct hash as the settign argument to
> crypt. While it's guaranteed that:
>
>         crypt(pass,failure_token) != failure_token
>
> it is impossible to guarantee that:
>
>         crypt(pass,some_other_hash) != failure_token

I think you can bind the username _and_ (salt,password) to the hash,
and that will ensure the conditions above behave as expected.  That
is, instead of storing the hash of (salt,password), instead store
(username,salt,password).  That should ensure a negligible probability
in cases where two users happen to use the same password, like
P@...ord1.

Jeff

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