Re: "too many auth failures"?

[nisse%lysator.liu.se@localhost (Niels Möller)]

Simon Josefsson <simon%josefsson.org@localhost> writes:

> Often private keys are protected by a password or requires a PIN to
> unlock a smartcard, and iterating to sign with all keys becomes a user
> interface issue quickly.

As far as I understand, the possibility to send a
SSH_MSG_USERAUTH_REQUEST without a signature in it is intended to solve
precisely this problem.

The client can store the *public* keys somewhere where you don't need
any user interaction to retrieve them, send a bunch of userauth requests
with these keys and no signatures. When you get a SSH_MSG_USERAUTH_PK_OK
response from the server, you ask the user to unlock the corresponding
private key and send a single SSH_MSG_USERAUTH_REQUEST with both key and
signature. This shouldn't have to cost more than a single network
roundtrip, independent of the number of public keys.

(Since I'd consider that client behaviour perfectly normal, I also think
that the server should *not* increment the failure counter when sending
a SSH_MSG_USERAUTH_PK_OK).

Regards,
/Niels

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