Nuno Gonçalves nunojpg at
Mon Jul 25 16:56:01 AEST 2016

Hi Alon,

I confirmed with pkcs11-tool (from OpenSC) and I can confirm that
pressing return when asked for the pin causes the login to stop (and
not to try a empty pin).

Can you confirm if a empty pin is actually a valid pin, and if not,
can the patch be accepted?

Once again, the problem is that from a user experience, *some/most*
users would expect they can skip pkcs11 token authentication just by
pressing return and trying then other authentication method, like

But currently that is not what happens, and users can find out too
late that they have instead tried a wrong pin too many times and
locked their token...


On Fri, Jun 17, 2016 at 10:04 PM, Alon Bar-Lev <alon.barlev at> wrote:
> On 17 June 2016 at 22:45, Nuno Gonçalves <nunojpg at> wrote:
>> On Fri, Jun 17, 2016 at 7:57 PM, Alon Bar-Lev <alon.barlev at> wrote:
>>> On 17 June 2016 at 20:58, Nuno Gonçalves <nunojpg at> wrote:
>>>> Hi,
>>>> It seems there is a bug with the pkcs11 feature where a zero-length
>>>> PIN is accepted. I believe this is a bug, since the user might want to
>>>> press return when asked for the PIN to ignore that slot/key.
>>> Hi,
>>> Empty PIN is valid case, not sure why you want to avoid supporting it.
>>> Alon
>> I didn't know it was valid but the reasoning still applies. I don't
>> really know the standard use cases, but I think it could eventually be
>> useful for the user, when asked for the PIN, to decide not enter it.
>> Currently it can only be done by killing ssh. If empty PIN is valid,
>> but eventually not usual, maybe we should ask if the user really wants
>> to try a empty pin or just continue to another authentication option?
> Not sure what best solution, but ignoring empty PIN is the same as
> ignoring "cancel" or similar constants, which is more explicit.
> What's wrong with plain <Ctrl>-C, as without PIN there is no use to
> continue session anyway.
>> Regarding the CKF_USER_PIN flags, do you think it is a good idea to
>> implement the warning messages?
> Most implementations do not support these.
> Regards,
> Alon

More information about the openssh-unix-dev mailing list