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).
-dros
>
>> +
>> switch (err) {
>> case 0:
>> case -NFS4ERR_WRONGSEC:
>
> --
> Trond Myklebust
> Linux NFS client maintainer
>
> NetApp
> Trond.Myklebust@xxxxxxxxxx
> www.netapp.com
--
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
