On Monday 07 October 2024 09:13:17 NeilBrown wrote: > On Mon, 07 Oct 2024, Chuck Lever wrote: > > On Fri, Sep 13, 2024 at 08:52:20AM +1000, NeilBrown wrote: > > > On Fri, 13 Sep 2024, Pali Rohár wrote: > > > > Currently NFSD_MAY_BYPASS_GSS and NFSD_MAY_BYPASS_GSS_ON_ROOT do not bypass > > > > only GSS, but bypass any authentication method. This is problem specially > > > > for NFS3 AUTH_NULL-only exports. > > > > > > > > The purpose of NFSD_MAY_BYPASS_GSS_ON_ROOT is described in RFC 2623, > > > > section 2.3.2, to allow mounting NFS2/3 GSS-only export without > > > > authentication. So few procedures which do not expose security risk used > > > > during mount time can be called also with AUTH_NONE or AUTH_SYS, to allow > > > > client mount operation to finish successfully. > > > > > > > > The problem with current implementation is that for AUTH_NULL-only exports, > > > > the NFSD_MAY_BYPASS_GSS_ON_ROOT is active also for NFS3 AUTH_UNIX mount > > > > attempts which confuse NFS3 clients, and make them think that AUTH_UNIX is > > > > enabled and is working. Linux NFS3 client never switches from AUTH_UNIX to > > > > AUTH_NONE on active mount, which makes the mount inaccessible. > > > > > > > > Fix the NFSD_MAY_BYPASS_GSS and NFSD_MAY_BYPASS_GSS_ON_ROOT implementation > > > > and really allow to bypass only exports which have some GSS auth flavor > > > > enabled. > > > > > > > > The result would be: For AUTH_NULL-only export if client attempts to do > > > > mount with AUTH_UNIX flavor then it will receive access errors, which > > > > instruct client that AUTH_UNIX flavor is not usable and will either try > > > > other auth flavor (AUTH_NULL if enabled) or fails mount procedure. > > > > > > > > This should fix problems with AUTH_NULL-only or AUTH_UNIX-only exports if > > > > client attempts to mount it with other auth flavor (e.g. with AUTH_NULL for > > > > AUTH_UNIX-only export, or with AUTH_UNIX for AUTH_NULL-only export). > > > > > > The MAY_BYPASS_GSS flag currently also bypasses TLS restrictions. With > > > your change it doesn't. I don't think we want to make that change. > > > > Neil, I'm not seeing this, I must be missing something. > > > > RPC_AUTH_TLS is used only on NULL procedures. > > > > The export's xprtsec= setting determines whether a TLS session must > > be present to access the files on the export. If the TLS session > > meets the xprtsec= policy, then the normal user authentication > > settings apply. In other words, I don't think execution gets close > > to check_nfsd_access() unless the xprtsec policy setting is met. > > check_nfsd_access() is literally the ONLY place that ->ex_xprtsec_modes > is tested and that seems to be where xprtsec= export settings are stored. > > > > > I'm not convinced check_nfsd_access() needs to care about > > RPC_AUTH_TLS. Can you expand a little on your concern? > > Probably it doesn't care about RPC_AUTH_TLS which as you say is only > used on NULL procedures when setting up the TLS connection. > > But it *does* care about NFS_XPRTSEC_MTLS etc. > > But I now see that RPC_AUTH_TLS is never reported by OP_SECINFO as an > acceptable flavour, so the client cannot dynamically determine that TLS > is required. Why is not RPC_AUTH_TLS announced in NFS4 OP_SECINFO? Should not NFS4 OP_SECINFO report all possible auth methods for particular filehandle? > So there is no value in giving non-tls clients access to > xprtsec=mtls exports so they can discover that for themselves. The > client needs to explicitly mount with tls, or possibly the client can > opportunistically try TLS in every case, and call back. > > So the original patch is OK. > > NeilBrown
