On Sep 5, 2013, at 11:31 AM, Dr James Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
> On Thu, Sep 05, 2013 at 03:17:37PM +0000, Adamson, Dros wrote:
>>
>> On Sep 5, 2013, at 10:07 AM, Dr James Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
>>
>>> On Thu, Sep 05, 2013 at 12:45:09AM +0000, Myklebust, Trond wrote:
>>>> On Wed, 2013-09-04 at 16:48 +0000, Adamson, Dros wrote:
>>>>> On Sep 4, 2013, at 12:24 PM, "Myklebust, Trond" <Trond.Myklebust@xxxxxxxxxx> wrote:
>>>>>
>>>>>> On Wed, 2013-09-04 at 12:13 -0400, Weston Andros Adamson wrote:
>>>>>>> Commit 97431204ea005ec8070ac94bc3251e836daa7ca7 introduced a regression
>>>>>>> that causes SECINFO_NO_NAME to fail without sending an RPC if:
>>>>>>>
>>>>>>> 1) the nfs_client's rpc_client is using krb5i/p (now tried by default)
>>>>>>> 2) the current user doesn't have valid kerberos credentials
>>>>>>>
>>>>>>> This situation is quite common - as of now a sec=sys mount would use
>>>>>>> krb5i for the nfs_client's rpc_client and a user would hardly be faulted
>>>>>>> for not having run kinit.
>>>>>>>
>>>>>>> The solution is to use the machine cred when trying to use an integrity
>>>>>>> protected auth flavor for SECINFO_NO_NAME.
>>>>>>>
>>>>>>> Older servers may not support using the machine cred or an integrity
>>>>>>> protected auth flavor for SECINFO_NO_NAME in every circumstance, so we fall
>>>>>>> back to using the user's cred and the filesystem's auth flavor in this case.
>>>>>>>
>>>>>>> We run into another problem when running against linux nfs servers -
>>>>>>> they return NFS4ERR_WRONGSEC when using integrity auth flavor (unless the
>>>>>>> mount is also that flavor) even though that is not a valid error for
>>>>>>> SECINFO*. Even though it's against spec, handle WRONGSEC errors on
>>>>>>> SECINFO_NO_NAME by falling back to using the user cred and the
>>>>>>> filesystem's auth flavor.
>>>>>>>
>>>>>>> Signed-off-by: Weston Andros Adamson <dros@xxxxxxxxxx>
>>>>>>> ---
>>>>>>>
>>>>>>> This patch goes along with yesterday's SECINFO patch
>>>>>>>
>>>>>>> fs/nfs/nfs4proc.c | 41 +++++++++++++++++++++++++++++++++++++----
>>>>>>> 1 file changed, 37 insertions(+), 4 deletions(-)
>>>>>>>
>>>>>>> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
>>>>>>> index ab1461e..74b37f5 100644
>>>>>>> --- a/fs/nfs/nfs4proc.c
>>>>>>> +++ b/fs/nfs/nfs4proc.c
>>>>>>> @@ -7291,7 +7291,8 @@ out:
>>>>>>> */
>>>>>>> static int
>>>>>>> _nfs41_proc_secinfo_no_name(struct nfs_server *server, struct nfs_fh *fhandle,
>>>>>>> - struct nfs_fsinfo *info, struct nfs4_secinfo_flavors *flavors)
>>>>>>> + struct nfs_fsinfo *info,
>>>>>>> + struct nfs4_secinfo_flavors *flavors, bool use_integrity)
>>>>>>> {
>>>>>>> struct nfs41_secinfo_no_name_args args = {
>>>>>>> .style = SECINFO_STYLE_CURRENT_FH,
>>>>>>> @@ -7304,8 +7305,23 @@ _nfs41_proc_secinfo_no_name(struct nfs_server *server, struct nfs_fh *fhandle,
>>>>>>> .rpc_argp = &args,
>>>>>>> .rpc_resp = &res,
>>>>>>> };
>>>>>>> - return nfs4_call_sync(server->nfs_client->cl_rpcclient, server, &msg,
>>>>>>> - &args.seq_args, &res.seq_res, 0);
>>>>>>> + struct rpc_clnt *clnt = server->client;
>>>>>>> + int status;
>>>>>>> +
>>>>>>> + if (use_integrity) {
>>>>>>> + clnt = server->nfs_client->cl_rpcclient;
>>>>>>> + msg.rpc_cred = nfs4_get_clid_cred(server->nfs_client);
>>>>>>> + }
>>>>>>> +
>>>>>>> + dprintk("--> %s\n", __func__);
>>>>>>> + status = nfs4_call_sync(clnt, server, &msg, &args.seq_args,
>>>>>>> + &res.seq_res, 0);
>>>>>>> + dprintk("<-- %s status=%d\n", __func__, status);
>>>>>>> +
>>>>>>> + if (msg.rpc_cred)
>>>>>>> + put_rpccred(msg.rpc_cred);
>>>>>>> +
>>>>>>> + return status;
>>>>>>> }
>>>>>>>
>>>>>>> static int
>>>>>>> @@ -7315,7 +7331,24 @@ nfs41_proc_secinfo_no_name(struct nfs_server *server, struct nfs_fh *fhandle,
>>>>>>> struct nfs4_exception exception = { };
>>>>>>> int err;
>>>>>>> do {
>>>>>>> - err = _nfs41_proc_secinfo_no_name(server, fhandle, info, flavors);
>>>>>>> + /* first try using integrity protection */
>>>>>>> + err = -NFS4ERR_WRONGSEC;
>>>>>>> +
>>>>>>> + /* try to use integrity protection with machine cred */
>>>>>>> + if (_nfs4_is_integrity_protected(server->nfs_client))
>>>>>>> + err = _nfs41_proc_secinfo_no_name(server, fhandle, info,
>>>>>>> + flavors, true);
>>>>>>> +
>>>>>>> + /*
>>>>>>> + * if unable to use integrity protection, or SECINFO with
>>>>>>> + * integrity protection returns NFS4ERR_WRONGSEC (which is
>>>>>>> + * disallowed by spec, but exists in deployed servers) use
>>>>>>> + * the current filesystem's rpc_client and the user cred.
>>>>>>> + */
>>>>>>> + if (err == -NFS4ERR_WRONGSEC)
>>>>>>> + err = _nfs41_proc_secinfo_no_name(server, fhandle, info,
>>>>>>> + flavors, false);
>>>>>>
>>>>>> As I said yesterday, RFC5661 forbids SECINFO_NO_NAME from returning
>>>>>> NFS4ERR_WRONGSEC, so this is 100% equivalent to
>>>>>>
>>>>>> if (!_nfs4_is_integrity_protected())
>>>>>> err = ….
>>>>>
>>>>> Right, but I thought we were doing this to support server implementations like linux that *do* return NFS4ERR_WRONGSEC on SECINFO_NO_NAME even though it's forbidden. I know we normally don't work around server bugs, but this seems pretty simple.
>>>>>
>>>>> If we don't do this, then SECINFO_NO_NAME will always fail against current linux severs no matter what the mount options - unless krb5i/p is unusable (not configured, time skew, no machine cred, etc).
>>>>
>>>> Bruce, you're it: what's the deal here?
>>>
>>> Dros, in what cases exactly do you see SECINFO_NO_NAME returning
>>> WRONGSEC?
>>>
>>> From a quick skim of the code it looks like it shouldn't happen in the
>>> CURRENT_FH case, which is the one the client uses. But I probably
>>> overlooked something....
>>>
>>> --b.
>>
>> SECINFO_NO_NAME will fail with NFS4ERR_WRONGSEC in check_nfsd_access when the rpc auth flavor is different from the export's auth flavor - in the same way as SECINFO.
>
> Huh. There's no check_nfsd_access call in secinfo_no_name in the
> CURRENT_FH case. And any checks on the putfh op should be turned off by
> the OP_HANDLES_WRONGSEC flag on secinfo_no_name.
>
> But I haven't actually tried it, and presumably you have (any hints on
> reproducing?), so I'll take a look....
>
> --b.
You may be right here - I'm pretty sure I saw SECINFO_NO_NAME fail like this, but I'm not 100%. I'll try to reproduce and report back.
-dros
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