Re: [PATCH RFC 5/5] NFSD: Handle new xprtsec= export option

[Jeff Layton <jlayton@kernel.org>]

On Tue, 2023-03-21 at 14:05 +0000, Chuck Lever III wrote:
> 
> > On Mar 21, 2023, at 7:50 AM, Jeff Layton <jlayton@kernel.org> wrote:
> > 
> > On Mon, 2023-03-20 at 10:24 -0400, Chuck Lever wrote:
> > > From: Chuck Lever <chuck.lever@oracle.com>
> > > 
> > > Enable administrators to require clients to use transport layer
> > > security when accessing particular exports.
> > 
> > > Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> > > ---
> > > fs/nfsd/export.c |   53 ++++++++++++++++++++++++++++++++++++++++++++++++++---
> > > fs/nfsd/export.h |   11 +++++++++++
> > > 2 files changed, 61 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
> > > index 668c7527b17e..171ebc21bf07 100644
> > > --- a/fs/nfsd/export.c
> > > +++ b/fs/nfsd/export.c
> > > @@ -439,7 +439,6 @@ static int check_export(struct path *path, int *flags, unsigned char *uuid)
> > > 		return -EINVAL;
> > > 	}
> > > 	return 0;
> > > -
> > > }
> > > 
> > > #ifdef CONFIG_NFSD_V4
> > > @@ -546,6 +545,31 @@ static inline int
> > > secinfo_parse(char **mesg, char *buf, struct svc_export *exp) { return 0; }
> > > #endif
> > > 
> > > +static int xprtsec_parse(char **mesg, char *buf, struct svc_export *exp)
> > > +{
> > > +	unsigned int i, mode, listsize;
> > > +	int err;
> > > +
> > > +	err = get_uint(mesg, &listsize);
> > > +	if (err)
> > > +		return err;
> > > +	if (listsize > 3)
> > > +		return -EINVAL;
> > 
> > Might want to make a note that the limit of 3 here is arbitrary, and
> > that it might need to be lifted in the future (if/when we grow other
> > xprtsec options).
> 
> Well I can easily add a symbolic constant for that too. I
> missed this one in the final clean-up before posting.
> 
> The bigger question is whether the new downcall parameter is
> sensible. If there's a nicer way for mountd to get this
> information to the kernel, I'm open to suggestion.
> 

I don't know of one. Export options seem fine here, since that's how we
control all sorts of options in the nfs server.

> 
> > > +
> > > +	exp->ex_xprtsec_modes = 0;
> > > +	for (i = 0; i < listsize; i++) {
> > > +		err = get_uint(mesg, &mode);
> > > +		if (err)
> > > +			return err;
> > > +		mode--;
> > > +		if (mode > 2)
> > > +			return -EINVAL;
> > > +		/* Ad hoc */
> > > +		exp->ex_xprtsec_modes |= 1 << mode;
> > > +	}
> > > +	return 0;
> > > +}
> > > +
> > > static inline int
> > > nfsd_uuid_parse(char **mesg, char *buf, unsigned char **puuid)
> > > {
> > > @@ -608,6 +632,7 @@ static int svc_export_parse(struct cache_detail *cd, char *mesg, int mlen)
> > > 	exp.ex_client = dom;
> > > 	exp.cd = cd;
> > > 	exp.ex_devid_map = NULL;
> > > +	exp.ex_xprtsec_modes = NFSEXP_XPRTSEC_ALL;
> > > 
> > > 	/* expiry */
> > > 	err = -EINVAL;
> > > @@ -650,6 +675,8 @@ static int svc_export_parse(struct cache_detail *cd, char *mesg, int mlen)
> > > 				err = nfsd_uuid_parse(&mesg, buf, &exp.ex_uuid);
> > > 			else if (strcmp(buf, "secinfo") == 0)
> > > 				err = secinfo_parse(&mesg, buf, &exp);
> > > +			else if (strcmp(buf, "xprtsec") == 0)
> > > +				err = xprtsec_parse(&mesg, buf, &exp);
> > > 			else
> > > 				/* quietly ignore unknown words and anything
> > > 				 * following. Newer user-space can try to set
> > > @@ -663,6 +690,7 @@ static int svc_export_parse(struct cache_detail *cd, char *mesg, int mlen)
> > > 		err = check_export(&exp.ex_path, &exp.ex_flags, exp.ex_uuid);
> > > 		if (err)
> > > 			goto out4;
> > > +
> > > 		/*
> > > 		 * No point caching this if it would immediately expire.
> > > 		 * Also, this protects exportfs's dummy export from the
> > > @@ -824,6 +852,7 @@ static void export_update(struct cache_head *cnew, struct cache_head *citem)
> > > 	for (i = 0; i < MAX_SECINFO_LIST; i++) {
> > > 		new->ex_flavors[i] = item->ex_flavors[i];
> > > 	}
> > > +	new->ex_xprtsec_modes = item->ex_xprtsec_modes;
> > > }
> > > 
> > > static struct cache_head *svc_export_alloc(void)
> > > @@ -1035,9 +1064,26 @@ static struct svc_export *exp_find(struct cache_detail *cd,
> > > 
> > > __be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp)
> > > {
> > > -	struct exp_flavor_info *f;
> > > -	struct exp_flavor_info *end = exp->ex_flavors + exp->ex_nflavors;
> > > +	struct exp_flavor_info *f, *end = exp->ex_flavors + exp->ex_nflavors;
> > > +	struct svc_xprt *xprt = rqstp->rq_xprt;
> > > +
> > > +	if (exp->ex_xprtsec_modes & NFSEXP_XPRTSEC_NONE) {
> > > +		if (!test_bit(XPT_TLS_SESSION, &xprt->xpt_flags))
> > > +			goto ok;
> > > +	}
> > > +	if (exp->ex_xprtsec_modes & NFSEXP_XPRTSEC_TLS) {
> > > +		if (test_bit(XPT_TLS_SESSION, &xprt->xpt_flags) &&
> > > +		    !test_bit(XPT_PEER_AUTH, &xprt->xpt_flags))
> > > +			goto ok;
> > > +	}
> > > +	if (exp->ex_xprtsec_modes & NFSEXP_XPRTSEC_MTLS) {
> > > +		if (test_bit(XPT_TLS_SESSION, &xprt->xpt_flags) &&
> > > +		    test_bit(XPT_PEER_AUTH, &xprt->xpt_flags))
> > > +			goto ok;
> > > +	}
> > > +	goto denied;
> > > 
> > > +ok:
> > > 	/* legacy gss-only clients are always OK: */
> > > 	if (exp->ex_client == rqstp->rq_gssclient)
> > > 		return 0;
> > > @@ -1062,6 +1108,7 @@ __be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp)
> > > 	if (nfsd4_spo_must_allow(rqstp))
> > > 		return 0;
> > > 
> > > +denied:
> > > 	return rqstp->rq_vers < 4 ? nfserr_acces : nfserr_wrongsec;
> > > }
> > > 
> > > diff --git a/fs/nfsd/export.h b/fs/nfsd/export.h
> > > index d03f7f6a8642..61e1e8383c3d 100644
> > > --- a/fs/nfsd/export.h
> > > +++ b/fs/nfsd/export.h
> > > @@ -77,8 +77,19 @@ struct svc_export {
> > > 	struct cache_detail	*cd;
> > > 	struct rcu_head		ex_rcu;
> > > 	struct export_stats	ex_stats;
> > > +	unsigned long		ex_xprtsec_modes;
> > > };
> > > 
> > > +enum {
> > > +	NFSEXP_XPRTSEC_NONE	= 0x01,
> > > +	NFSEXP_XPRTSEC_TLS	= 0x02,
> > > +	NFSEXP_XPRTSEC_MTLS	= 0x04,
> > > +};
> > > +
> > > +#define NFSEXP_XPRTSEC_ALL	(NFSEXP_XPRTSEC_NONE | \
> > > +				 NFSEXP_XPRTSEC_TLS | \
> > > +				 NFSEXP_XPRTSEC_MTLS)
> > > +
> > > /* an "export key" (expkey) maps a filehandlefragement to an
> > >  * svc_export for a given client.  There can be several per export,
> > >  * for the different fsid types.
> > > 
> > > 
> > 
> > -- 
> > Jeff Layton <jlayton@kernel.org>
> > 
> 
> --
> Chuck Lever
> 
> 

-- 
Jeff Layton <jlayton@kernel.org>