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

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Date:	Tue, 3 May 2016 11:34:09 -0700
From:	Gwendal Grignou <gwendal@...gle.com>
To:	Gwendal Grignou <gwendal@...omium.org>
Cc:	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

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
>>