linux-kernel - Re: [PATCH] keyrings: Allow searching the user session keyring

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Date:	Fri, 20 May 2016 14:27:47 -0500
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Gwendal Grignou <gwendal@...gle.com>
Cc:	Gwendal Grignou <gwendal@...omium.org>, dhowells@...hat.com,
	james.l.morris@...cle.com, serge@...lyn.com,
	keyrings@...r.kernel.org,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-security-module@...r.kernel.org,
	Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH] keyrings: Allow searching the user session keyring

Sorry, I just don't know al lthe subtleties there, I think we just need
David's ack/nack here.

Quoting Gwendal Grignou (gwendal@...gle.com):
> Any feedback on this? It is mandatory if we want to mount a ecryptfs
> directory while the session keyring is used.
> 
> Thanks,
> Gwendal.
> 
> On Thu, Mar 17, 2016 at 10:04 AM, Gwendal Grignou <gwendal@...omium.org> wrote:
> > Resent to a larger audience.
> >
> > On Thu, Mar 10, 2016 at 2:20 PM, Gwendal Grignou <gwendal@...omium.org> wrote:
> >> Currently, if a session keyring exists, we are not searching in the
> >> user session or user keyrings.
> >>
> >> This is a problem when a session keyring exists and we want to use
> >> ecryptfs, who adds the needed key only in the user keyring.
> >>
> >> TEST=Without this change, mounting an ecryptfs "partition" fails when a
> >> session keyring exists:
> >> ...
> >> [ 2686.047522] Could not find key with description: [dd6f92bd8660b36c]
> >> ...
> >> Although the key exits:
> >> keyctl show @us
> >> Keyring
> >>  549666721 --alswrv      0 65534  keyring: _uid_ses.0
> >>  346719914 --alswrv      0 65534   \_ keyring: _uid.0
> >>  235623693 --alswrv      0     0       \_ user: dd6f92bd8660b36c
> >>  747773852 --alswrv      0     0       \_ user: 7025717e50fd74a2
> >> With this change, ecryptfs can see the keys it needs.
> >>
> >> Note that 'keyctl show' still only shows the session keyring by default.
> >> We need to specify 'keyctl show @us' to see the user session keyring
> >> when the session keyring exits.
> >>
> >> Signed-off-by: Gwendal Grignou <gwendal@...omium.org>
> >> ---
> >>  security/keys/process_keys.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
> >> index e6d50172..a77d66e 100644
> >> --- a/security/keys/process_keys.c
> >> +++ b/security/keys/process_keys.c
> >> @@ -395,8 +395,8 @@ key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx)
> >>                         break;
> >>                 }
> >>         }
> >> -       /* or search the user-session keyring */
> >> -       else if (ctx->cred->user->session_keyring) {
> >> +       /* finally search the user-session keyring */
> >> +       if (ctx->cred->user->session_keyring) {
> >>                 key_ref = keyring_search_aux(
> >>                         make_key_ref(ctx->cred->user->session_keyring, 1),
> >>                         ctx);
> >> --
> >> 2.7.0.rc3.207.g0ac5344
> >>