Re: [PATCH v1 2/4] exports: Add an xprtsec= export option

[Jeff Layton <jlayton@kernel.org>]

On Tue, 2023-03-21 at 18:08 +0000, Chuck Lever III wrote:
> 
> > On Mar 21, 2023, at 7:55 AM, Jeff Layton <jlayton@kernel.org> wrote:
> > 
> > On Mon, 2023-03-20 at 10:35 -0400, Chuck Lever wrote:
> > > From: Chuck Lever <chuck.lever@oracle.com>
> > > 
> > > The overall goal is to enable administrators to require the use of
> > > transport layer security when clients access particular exports.
> > > 
> > > This patch adds support to exportfs to parse and display a new
> > > xprtsec= export option. The setting is not yet passed to the kernel.
> > > 
> > > Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> > > ---
> > > support/include/nfs/export.h |    6 +++
> > > support/include/nfslib.h     |   14 +++++++
> > > support/nfs/exports.c        |   85 ++++++++++++++++++++++++++++++++++++++++++
> > > utils/exportfs/exportfs.c    |    1 
> > > 4 files changed, 106 insertions(+)
> > > 
> > > diff --git a/support/include/nfs/export.h b/support/include/nfs/export.h
> > > index 0eca828ee3ad..b29c6fa4f554 100644
> > > --- a/support/include/nfs/export.h
> > > +++ b/support/include/nfs/export.h
> > > @@ -40,4 +40,10 @@
> > > #define NFSEXP_OLD_SECINFO_FLAGS (NFSEXP_READONLY | NFSEXP_ROOTSQUASH \
> > > 					| NFSEXP_ALLSQUASH)
> > > 
> > > +enum {
> > > +	NFSEXP_XPRTSEC_NONE = 1,
> > > +	NFSEXP_XPRTSEC_TLS = 2,
> > > +	NFSEXP_XPRTSEC_MTLS = 3,
> > > +};
> > > +
> > 
> > Can we put these into a uapi header somewhere and then just have
> > nfs-utils use those if they're defined?
> 
> I moved these to include/uapi/linux/nfsd/export.h in the
> kernel patches, and adjust the nfs-utils patches to use the
> same numeric values in exportfs as the kernel.
>
> But it's not clear how a uAPI header would become visible
> during, say, an RPM build of nfs-utils. Does anyone know
> how that works? The kernel docs I've read suggest uAPI is
> for user space tools that actually live in the kernel source
> tree.
> 

Unfortunately, you need to build on a box that has kernel headers from
an updated kernel.

The usual way to deal with this is to have a copy in the userland
sources but only define them if one of the relevant constants isn't
already defined.

So you'll probably want to keep something like this in the userland
tree:

#ifndef NFSEXP_XPRTSEC_NONE
# define NFSEXP_XPRTSEC_NONE 1
# define NFSEXP_XPRTSEC_TLS  2
# define NFSEXP_XPRTSEC_MTLS 3
#endif

There may be some way to do that and keep it as an enum too. I'm not
sure.

> I think the cases where only user space or only the kernel
> support xprtsec should work OK: the kernel has a default
> transport layer security policy of "all ok" and old kernels
> ignore export options from user space they don't recognize.
> 

Great!

> > > #endif /* _NSF_EXPORT_H */
> > > diff --git a/support/include/nfslib.h b/support/include/nfslib.h
> > > index 6faba71bf0cd..9a188fb84790 100644
> > > --- a/support/include/nfslib.h
> > > +++ b/support/include/nfslib.h
> > > @@ -62,6 +62,18 @@ struct sec_entry {
> > > 	int flags;
> > > };
> > > 
> > > +#define XPRTSECMODE_COUNT 4
> > > +
> > > +struct xprtsec_info {
> > > +	const char		*name;
> > > +	int			number;
> > > +};
> > > +
> > > +struct xprtsec_entry {
> > > +	const struct xprtsec_info *info;
> > > +	int			flags;
> > > +};
> > > +
> > > /*
> > >  * Data related to a single exports entry as returned by getexportent.
> > >  * FIXME: export options should probably be parsed at a later time to
> > > @@ -83,6 +95,7 @@ struct exportent {
> > > 	char *          e_fslocdata;
> > > 	char *		e_uuid;
> > > 	struct sec_entry e_secinfo[SECFLAVOR_COUNT+1];
> > > +	struct xprtsec_entry e_xprtsec[XPRTSECMODE_COUNT + 1];
> > > 	unsigned int	e_ttl;
> > > 	char *		e_realpath;
> > > };
> > > @@ -99,6 +112,7 @@ struct rmtabent {
> > > void			setexportent(char *fname, char *type);
> > > struct exportent *	getexportent(int,int);
> > > void 			secinfo_show(FILE *fp, struct exportent *ep);
> > > +void			xprtsecinfo_show(FILE *fp, struct exportent *ep);
> > > void			putexportent(struct exportent *xep);
> > > void			endexportent(void);
> > > struct exportent *	mkexportent(char *hname, char *path, char *opts);
> > > diff --git a/support/nfs/exports.c b/support/nfs/exports.c
> > > index 7f12383981c3..da8ace3a65fd 100644
> > > --- a/support/nfs/exports.c
> > > +++ b/support/nfs/exports.c
> > > @@ -99,6 +99,7 @@ static void init_exportent (struct exportent *ee, int fromkernel)
> > > 	ee->e_fslocmethod = FSLOC_NONE;
> > > 	ee->e_fslocdata = NULL;
> > > 	ee->e_secinfo[0].flav = NULL;
> > > +	ee->e_xprtsec[0].info = NULL;
> > > 	ee->e_nsquids = 0;
> > > 	ee->e_nsqgids = 0;
> > > 	ee->e_uuid = NULL;
> > > @@ -248,6 +249,17 @@ void secinfo_show(FILE *fp, struct exportent *ep)
> > > 	}
> > > }
> > > 
> > > +void xprtsecinfo_show(FILE *fp, struct exportent *ep)
> > > +{
> > > +	struct xprtsec_entry *p1, *p2;
> > > +
> > > +	for (p1 = ep->e_xprtsec; p1->info; p1 = p2) {
> > > +		fprintf(fp, ",xprtsec=%s", p1->info->name);
> > > +		for (p2 = p1 + 1; p2->info && (p1->flags == p2->flags); p2++)
> > > +			fprintf(fp, ":%s", p2->info->name);
> > > +	}
> > > +}
> > > +
> > > static void
> > > fprintpath(FILE *fp, const char *path)
> > > {
> > > @@ -344,6 +356,7 @@ putexportent(struct exportent *ep)
> > > 	}
> > > 	fprintf(fp, "anonuid=%d,anongid=%d", ep->e_anonuid, ep->e_anongid);
> > > 	secinfo_show(fp, ep);
> > > +	xprtsecinfo_show(fp, ep);
> > > 	fprintf(fp, ")\n");
> > > }
> > > 
> > > @@ -482,6 +495,75 @@ static unsigned int parse_flavors(char *str, struct exportent *ep)
> > > 	return out;
> > > }
> > > 
> > > +static const struct xprtsec_info xprtsec_name2info[] = {
> > > +	{ "none",	NFSEXP_XPRTSEC_NONE },
> > > +	{ "tls",	NFSEXP_XPRTSEC_TLS },
> > > +	{ "mtls",	NFSEXP_XPRTSEC_MTLS },
> > > +	{ NULL,		0 }
> > > +};
> > > +
> > > +static const struct xprtsec_info *find_xprtsec_info(const char *name)
> > > +{
> > > +	const struct xprtsec_info *info;
> > > +
> > > +	for (info = xprtsec_name2info; info->name; info++)
> > > +		if (strcmp(info->name, name) == 0)
> > > +			return info;
> > > +	return NULL;
> > > +}
> > > +
> > > +/*
> > > + * Append the given xprtsec mode to the exportent's e_xprtsec array,
> > > + * or do nothing if it's already there. Returns the index of flavor in
> > > + * the resulting array in any case.
> > > + */
> > > +static int xprtsec_addmode(const struct xprtsec_info *info, struct exportent *ep)
> > > +{
> > > +	struct xprtsec_entry *p;
> > > +
> > > +	for (p = ep->e_xprtsec; p->info; p++)
> > > +		if (p->info == info || p->info->number == info->number)
> > > +			return p - ep->e_xprtsec;
> > > +
> > > +	if (p - ep->e_xprtsec >= XPRTSECMODE_COUNT) {
> > > +		xlog(L_ERROR, "more than %d xprtsec modes on an export\n",
> > > +			XPRTSECMODE_COUNT);
> > > +		return -1;
> > > +	}
> > > +	p->info = info;
> > > +	p->flags = ep->e_flags;
> > > +	(p + 1)->info = NULL;
> > > +	return p - ep->e_xprtsec;
> > > +}
> > > +
> > > +/*
> > > + * @str is a colon seperated list of transport layer security modes.
> > > + * Their order is recorded in @ep, and a bitmap corresponding to the
> > > + * list is returned.
> > > + *
> > > + * A zero return indicates an error.
> > > + */
> > > +static unsigned int parse_xprtsec(char *str, struct exportent *ep)
> > > +{
> > > +	unsigned int out = 0;
> > > +	char *name;
> > > +
> > > +	while ((name = strsep(&str, ":"))) {
> > > +		const struct xprtsec_info *info = find_xprtsec_info(name);
> > > +		int bit;
> > > +
> > > +		if (!info) {
> > > +			xlog(L_ERROR, "unknown xprtsec mode %s\n", name);
> > > +			return 0;
> > > +		}
> > > +		bit = xprtsec_addmode(info, ep);
> > > +		if (bit < 0)
> > > +			return 0;
> > > +		out |= 1 << bit;
> > > +	}
> > > +	return out;
> > > +}
> > > +
> > > /* Sets the bits in @mask for the appropriate security flavor flags. */
> > > static void setflags(int mask, unsigned int active, struct exportent *ep)
> > > {
> > > @@ -687,6 +769,9 @@ bad_option:
> > > 			active = parse_flavors(opt+4, ep);
> > > 			if (!active)
> > > 				goto bad_option;
> > > +		} else if (strncmp(opt, "xprtsec=", 8) == 0) {
> > > +			if (!parse_xprtsec(opt + 8, ep))
> > > +				goto bad_option;
> > > 		} else {
> > > 			xlog(L_ERROR, "%s:%d: unknown keyword \"%s\"\n",
> > > 					flname, flline, opt);
> > > diff --git a/utils/exportfs/exportfs.c b/utils/exportfs/exportfs.c
> > > index 6d79a5b3480d..37b9e4b3612d 100644
> > > --- a/utils/exportfs/exportfs.c
> > > +++ b/utils/exportfs/exportfs.c
> > > @@ -743,6 +743,7 @@ dump(int verbose, int export_format)
> > > #endif
> > > 			}
> > > 			secinfo_show(stdout, ep);
> > > +			xprtsecinfo_show(stdout, ep);
> > > 			printf("%c\n", (c != '(')? ')' : ' ');
> > > 		}
> > > 	}
> > > 
> > > 
> > 
> > -- 
> > Jeff Layton <jlayton@kernel.org>
> 
> --
> Chuck Lever
> 
> 

-- 
Jeff Layton <jlayton@kernel.org>