On Fri, 2019-09-13 at 09:47 +0200, Alfonso Sanchez-Beato via
networkmanager-list wrote:
> Hi,

Hi,


> We have found a problem by which a buggy access point rejects a valid
> passphrase in the 4-Way Handshake phase. This happens just after the
> AP has rebooted - a few seconds later the AP accepts the passphrase
> again.
> 
> The problem is that NetworkManager drops the passphrase after the
> failure to connect ( see 
> https://github.com/NetworkManager/NetworkManager/blob/master/src/devices/wifi/nm-device-wifi.c#L1969
> ), and then it tries to call an agent to get another passphrase. In
> this set-up, we do not have that agent, and then the connection stays
> there and there are no more connection retries.
> 
> It does not look like NM has currently a way to force retries in this
> case, although I would be happy to be proven wrong.

What you describe is a problem, with nasty effects.

- the user gets repeatedly prompt for a password, although the password
is right.

- if no agent is available, the connection gets blocked from
autoconnect. That's especially problematic, if the user is not
available to manually re-trigger an authentication.


> So, I have thought of some possible ways to solve this and would
> appreciate your feedback on what would be the best approach and what
> would be acceptable to be merged:
> 
> 1. Do some retries before calling the agent

Does that solve the problem? Also, I don't think this should be done by
default, because the user might get blocked. Also, doing this
unconditionally, adds quite a delay in the common case where the
password is indeed wrong.

> 2. Do not drop the secret if there is no agent registered

Not "dropping" the secret does not seem to be a solution. It's merely
part of a possible solution.

> 3. Have a new property for the connection that forbids dropping
> secrets

While it's ugly to do this, I think it's the only solution. We could
add a connection property to the connection profile that says "assume-
the-secret-is-correct-for-n-times". The current behavior is like "1".
"0" means forever (with some ratelimiting).


best,
Thomas

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