[Freeipa-devel] [PATCH 0030] Add OTP sync plugin

[Nathaniel McCallum]

On Thu, 2014-01-23 at 22:12 +0200, Alexander Bokovoy wrote:
> On Thu, 23 Jan 2014, Nathaniel McCallum wrote:
> >On Thu, 2014-01-23 at 14:23 -0500, Simo Sorce wrote:
> >> On Thu, 2014-01-09 at 16:28 -0500, Nathaniel McCallum wrote:
> >> > This plugin adds an extended operation for synchronizing tokens. This
> >> > operation is availalbe both with and without bind. In the latter case,
> >> > the first factor is required. This operation can also be performed
> >> > on a per-token or per-user level. In the latter case, we will attempt
> >> > to find the token automatically.
> >> >
> >> > Thanks to Mark Reynolds for helping me with this patch.
> >>
> >>
> >> Huge NACK,
> >>
> >> otp_sync_request_authenticate() is not ok, it allows an attacker to do
> >> password bruteforcing without any check.
> >>
> >> This is the result of trying to re-implement what is basically a bind
> >> but w/o using the ind code.
> >>
> >> No checks to see if the user is enabled/disabled/locked
> >> No updates for locking account after N wrong tries, etc...
> >>
> >> It also duplicates the places to change should we wish to not depend on
> >> having userPassword as an actual password field anymore (which I
> >> considered multiple times as we already have kerberos keys against which
> >> we could test binds in theory).
> >>
> >> You should either extend the bind operation so all checks are used there
> >> and re-sync is done at last if all checks pass, and as a bonus you end
> >> up with an authenticated LDAP connection should you need it, or the bind
> >> code that does all the checks need to be abstracted into helper
> >> functions that can be reused by this plugin.
> >>
> >> Simo.
> >
> >Is it possible to do a post-bind extop which rejects the bind? Because
> >if synchronization fails, we MUST reject the authentication even if the
> >first factor was validated correctly. Also, is it possible to add
> >extended data to a bind operation? Because if not, this is going to get
> >hairy fast.
> Extended data on the server side? You can set what you want in PB in
> pre-bind and pick it up in post-bind.
> 
> However, the question is about successful binds -- when SIMPLE bind is
> successful DS code will send response to the client and will call post
> plugins. The response is sent unconditionally.
> 
> May be we could add a condition that if a certain flag is set in PB
> after pre-bind plugins ran successfully, response is not sent and
> post-bind plugins then run. A post-bind plugin then is required to
> send out proper result.

No, extended data from the client side. The client needs to somehow
communicate to the server:
1. that it wants the server to resynchronize
2. two tokens codes in a row

Ideally we need some sort of additional metadata in the bind request.
Without this, doing all the tests are pretty much impossible. We could
refactor the code in ipa-pwd-extop into a library, but ipa-pwd-extop
doesn't contain all the tests. Some of them are built into 389ds. The
ipa-pwd-extop plugin just performs additional work and then falls
through to 389ds.

What we need to do is this:

bool bind_preop() {
    if (otp_configured() && !is_sync_request())
        if (!validate_otp())
            return false;

    // ... fall through to password validation ...
}

bool bind_postop() {
    return bind_successful()
           && (!is_sync_request()
               || perform_synchronization());
}

At the least, however, we need extra metadata for is_sync_request().

So the question is: is it possible to get some extra metadata in a bind
request?

Nathaniel