A while back I had reported that an NFSv3 client could successfully
mount using '-o xprtsec=none' an export that had been exported with
'xprtsec=tls:mtls'. By "successfully" I mean that the mount command
would succeed and the mount would show up in /proc/mounts. Attempting
to do anything futher with the mount would be met with NFS3ERR_ACCES.
This was fixed (albeit accidentally) by bb4f07f2409c ("nfsd: Fix
NFSD_MAY_BYPASS_GSS and NFSD_MAY_BYPASS_GSS_ON_ROOT") and was
subsequently re-broken by 0813c5f01249 ("nfsd: fix access checking for
NLM under XPRTSEC policies").
Transport Layer Security isn't an RPC security flavor or pseudo-flavor,
so they shouldn't be conflated when determining whether the access
checks can be bypassed.
Signed-off-by: Scott Mayhew <smayhew@xxxxxxxxxx>
---
fs/nfsd/export.c | 60 ++++++++++++++++++++++++++++++++++++----------
fs/nfsd/export.h | 1 +
fs/nfsd/nfs4proc.c | 6 ++++-
fs/nfsd/nfs4xdr.c | 3 +++
fs/nfsd/nfsfh.c | 8 +++++++
fs/nfsd/vfs.c | 3 +++
6 files changed, 67 insertions(+), 14 deletions(-)
diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index cadfc2bae60e..bc54b01bb516 100644
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -1082,19 +1082,27 @@ static struct svc_export *exp_find(struct cache_detail *cd,
}
/**
- * check_nfsd_access - check if access to export is allowed.
+ * check_xprtsec_policy - check if access to export is permitted by the
+ * xprtsec policy
* @exp: svc_export that is being accessed.
* @rqstp: svc_rqst attempting to access @exp (will be NULL for LOCALIO).
- * @may_bypass_gss: reduce strictness of authorization check
+ *
+ * This logic should not be combined with check_nfsd_access, as the rules
+ * for bypassing GSS are not the same as for bypassing the xprtsec policy
+ * check:
+ * - NFSv3 FSINFO and GETATTR can bypass the GSS for the root dentry,
+ * but that doesn't mean they can bypass the xprtsec poolicy check
+ * - NLM can bypass the GSS check on exports exported with the
+ * NFSEXP_NOAUTHNLM flag
+ * - NLM can always bypass the xprtsec policy check since TLS isn't
+ * implemented for the sidecar protocols
*
* Return values:
* %nfs_ok if access is granted, or
- * %nfserr_wrongsec if access is denied
+ * %nfserr_acces or %nfserr_wrongsec if access is denied
*/
-__be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp,
- bool may_bypass_gss)
+__be32 check_xprtsec_policy(struct svc_export *exp, struct svc_rqst *rqstp)
{
- struct exp_flavor_info *f, *end = exp->ex_flavors + exp->ex_nflavors;
struct svc_xprt *xprt;
/*
@@ -1110,22 +1118,49 @@ __be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp,
if (exp->ex_xprtsec_modes & NFSEXP_XPRTSEC_NONE) {
if (!test_bit(XPT_TLS_SESSION, &xprt->xpt_flags))
- goto ok;
+ return nfs_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;
+ return nfs_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;
+ return nfs_ok;
}
- if (!may_bypass_gss)
- goto denied;
-ok:
+ return rqstp->rq_vers < 4 ? nfserr_acces : nfserr_wrongsec;
+}
+
+/**
+ * check_nfsd_access - check if access to export is allowed.
+ * @exp: svc_export that is being accessed.
+ * @rqstp: svc_rqst attempting to access @exp (will be NULL for LOCALIO).
+ * @may_bypass_gss: reduce strictness of authorization check
+ *
+ * Return values:
+ * %nfs_ok if access is granted, or
+ * %nfserr_wrongsec if access is denied
+ */
+__be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp,
+ bool may_bypass_gss)
+{
+ struct exp_flavor_info *f, *end = exp->ex_flavors + exp->ex_nflavors;
+ struct svc_xprt *xprt;
+
+ /*
+ * If rqstp is NULL, this is a LOCALIO request which will only
+ * ever use a filehandle/credential pair for which access has
+ * been affirmed (by ACCESS or OPEN NFS requests) over the
+ * wire. So there is no need for further checks here.
+ */
+ if (!rqstp)
+ return nfs_ok;
+
+ xprt = rqstp->rq_xprt;
+
/* legacy gss-only clients are always OK: */
if (exp->ex_client == rqstp->rq_gssclient)
return nfs_ok;
@@ -1167,7 +1202,6 @@ __be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp,
}
}
-denied:
return nfserr_wrongsec;
}
diff --git a/fs/nfsd/export.h b/fs/nfsd/export.h
index b9c0adb3ce09..c5a45f4b72be 100644
--- a/fs/nfsd/export.h
+++ b/fs/nfsd/export.h
@@ -101,6 +101,7 @@ struct svc_expkey {
struct svc_cred;
int nfsexp_flags(struct svc_cred *cred, struct svc_export *exp);
+__be32 check_xprtsec_policy(struct svc_export *exp, struct svc_rqst *rqstp);
__be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp,
bool may_bypass_gss);
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 71b428efcbb5..71e9a170f7bf 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -2902,8 +2902,12 @@ nfsd4_proc_compound(struct svc_rqst *rqstp)
clear_current_stateid(cstate);
if (current_fh->fh_export &&
- need_wrongsec_check(rqstp))
+ need_wrongsec_check(rqstp)) {
+ op->status = check_xprtsec_policy(current_fh->fh_export, rqstp);
+ if (op->status)
+ goto encode_op;
op->status = check_nfsd_access(current_fh->fh_export, rqstp, false);
+ }
}
encode_op:
if (op->status == nfserr_replay_me) {
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index ea91bad4eee2..48d55c13c918 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3859,6 +3859,9 @@ nfsd4_encode_entry4_fattr(struct nfsd4_readdir *cd, const char *name,
nfserr = nfserrno(err);
goto out_put;
}
+ nfserr = check_xprtsec_policy(exp, cd->rd_rqstp);
+ if (nfserr)
+ goto out_put;
nfserr = check_nfsd_access(exp, cd->rd_rqstp, false);
if (nfserr)
goto out_put;
diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index 74cf1f4de174..1ffc33662582 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -364,6 +364,14 @@ __fh_verify(struct svc_rqst *rqstp,
if (error)
goto out;
+ if (access & NFSD_MAY_NLM)
+ /* NLM is allowed to bypass the xprtssec policy check */
+ goto out;
+
+ error = check_xprtsec_policy(exp, rqstp);
+ if (error)
+ goto out;
+
if ((access & NFSD_MAY_NLM) && (exp->ex_flags & NFSEXP_NOAUTHNLM))
/* NLM is allowed to fully bypass authentication */
goto out;
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 98ab55ba3ced..1b66aff1d750 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -323,6 +323,9 @@ nfsd_lookup(struct svc_rqst *rqstp, struct svc_fh *fhp, const char *name,
err = nfsd_lookup_dentry(rqstp, fhp, name, len, &exp, &dentry);
if (err)
return err;
+ err = check_xprtsec_policy(exp, rqstp);
+ if (err)
+ goto out;
err = check_nfsd_access(exp, rqstp, false);
if (err)
goto out;
--
2.48.1
