On Tue, 2013-10-22 at 15:32 +0000, Adamson, Andy wrote: > On Oct 22, 2013, at 11:02 AM, Simo Sorce <simo@xxxxxxxxxx> wrote: > > > On Tue, 2013-10-22 at 10:22 -0400, andros@xxxxxxxxxx wrote: > >> From: Andy Adamson <andros@xxxxxxxxxx> > >> > >> This is an RFC patchset, which will be used for testing. > >> > >> This patchset requires the "SUNRPC: destroy gss_cred and context on Kerberos credential destruction" kernel patchset. > >> > >> We need to do a lot of testing to ensure that once kdestroy and gss-ctx > >> gss_user_destroy is called, all existing buffered > >> writes using the 'destroyed gss credential + context' are serviced. > >> > >> Differences from version 1: > >> > >> - moved from nfstgt_login and nfstgt_logout to gsskeyd. > >> - gsskeyd automatically creates gss-ctx key on kinit and destroys the gss-ctx > >> key on kdestroy. > >> > >> gsskeyd will need to act differently for different krb5 credential caches. > > > > Why ? > > Just need different parsing to know which directory to poll. > > > >> For example, some versions of gssd store FILE credentials in FILE:/tmp/krb5cc_<UID> > >> while this code, written for fedora 19 uses FILE:/run/user/<UID>/krb5cc/tgt. > > > > This is incorrect, Fedora 19 use DIR type ccaches, so you should > > reference a cache withing the dir type, which will notmally be something > > like: DIR:/run/user/<uidnumber>/krb5cc for the whole collection or > > DIR::/run/user/<uidnumber>/krb5cc/txtXXXXXX for the sepcific cache. > > > > However note that due to issues with DIR type caches we are moving to a > > new KEYRING based type of cache in F20, so assuming any specific type of > > cache is a dead start. > > But I'm not assuming any kind of kerberos credential cache! I just coded to one type for this RFC. > Didn't you see my KEYRING based ccache comment below? Ah sorry, I had not noticed. > >> As Trond suggested, if we keep gsskeyd separate from gssd, we could set up a > >> configuration file along the lines of the keytools' request-key.conf file to > >> allow both NFS and CIFS (and other filesystems) to install plugin handlers > >> for kinit/kdestroy events. > > > > Given in many cases (the desirable ones at least) kerberos credentials > > are not inited via kinit, but rather by things like pam_krb5, sssd, or > > directly imported via sshd, I am trying to understand how you are going > > to address the majority of these cases. > > All of these cases use a kerberos credential cache which if is of type > FILE the gsskeyd can poll inotify and if it is of type KEY: then > gsskeyd adds the gss-ctx key to the Kerberos keyring (that is the > theory :)) so the same code services kinit/pam_krb5 You wouldn't be able to see it if I set a custom ccache file though export KRB5CCNAME=FILE:/random/sir/foofile > > Should users put gsskeyd in their .profile/.bashrc files or something ? > > > >> Else, we could have gssd be the process to poll inotify (given > >> that it already polls rpc_pipefs) and then just have it fork off the > >> subprocess if and when it sees an interesting event. > > > > What is an 'interesting' event ? > > TGT (used for NFS TGS) creation/destruction Shouldn't you care for the specific NFS ticket only ? Although kdestroy is quite blunt, in theory users can simply destroy the specific NFS ticket and keep their TGT. Also I see a problem with this approach. In order to make user life easier we reinit ccaches in sssd when a user for example unlocks the screen. If you track a specific TGT or NFS ticket, this would cause the immediate destruction of credentials in the nfs client which will also kill access to the NFS server. I think this would cause quite some grief to users. > >> We need to investigate how this works when the kernel keyring is used for > >> Kerberos credentials. I believe that in this case gsskeyd can add the gss-ctx > >> key to the kerberos keyring, and it will get destroyed along with all other > >> keys at kdestroy. > > > > Is there any reason why you are doing this work with an utility that is > > separate from gssd or libkrb5 ? > > Yes - to allow both NFS and CIFS (and other filesystems) to install > plugin handlers for kerberos credential cache creation/destruction > events. > > But, having gssd do it is fine, or having a client plugin in libkrb5 > is also fine. > > > > I think the only sensible way to handle something like this is by adding > > support directly in libkrb5, I do not see something external ever > > working reliably. > > I agree that I should persue a libkrb5 approach. Keep in mind the point above though. The issues here is that you do not know what the intention was if you try a completely automated approach. you should probably interact with the login service and act conditionally in any way. I think it may be safer for you to provide a hook that the system can call when a user fully logs out. And use that hook to kill any credential associated to a particular UID. Done this way you do not need to poll anything nor change libkrb5. And you also allow the creation of a tool that the user can run to force the destruction of his credentials if he is not using a compliant login manager. Or if he wants to explicitly kill NFS creds in the kernel for whatever reason. > > I am not against it for testing purposes, but then does it need to be > > committed to nfs-utils ? > > Did you not see the "This is an RFC patchset"? I'm not asking for a commit to nfs-utils, but "request for comments" which you just did! Thanks :) Yes I was providing feedback :-) Simo. -- Simo Sorce * Red Hat, Inc * New York -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
