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

[Chuck Lever III <chuck.lever@oracle.com>]

> 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.


>> +
>> +	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