nfsd4: implement minimal SP4_MACH_CRED

Do a minimal SP4_MACH_CRED implementation suggested by Trond, ignoring
the client-provided spo_must_* arrays and just enforcing credential
checks for the minimum required operations.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

3 files changed, 87 insertions, 12 deletions

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 109b43402e82..2383d24e258f 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1265,6 +1265,31 @@ same_creds(struct svc_cred *cr1, struct svc_cred *cr2)
         return 0 == strcmp(cr1->cr_principal, cr2->cr_principal);
 }
 
+static bool svc_rqst_integrity_protected(struct svc_rqst *rqstp)
+{
+        struct svc_cred *cr = &rqstp->rq_cred;
+        u32 service;
+
+        service = gss_pseudoflavor_to_service(cr->cr_gss_mech, cr->cr_flavor);
+        return service == RPC_GSS_SVC_INTEGRITY ||
+               service == RPC_GSS_SVC_PRIVACY;
+}
+
+static bool mach_creds_match(struct nfs4_client *cl, struct svc_rqst *rqstp)
+{
+        struct svc_cred *cr = &rqstp->rq_cred;
+
+        if (!cl->cl_mach_cred)
+                return true;
+        if (cl->cl_cred.cr_gss_mech != cr->cr_gss_mech)
+                return false;
+        if (!svc_rqst_integrity_protected(rqstp))
+                return false;
+        if (!cr->cr_principal)
+                return false;
+        return 0 == strcmp(cl->cl_cred.cr_principal, cr->cr_principal);
+}
+
 static void gen_clid(struct nfs4_client *clp, struct nfsd_net *nn)
 {
         static u32 current_clientid = 1;
@@ -1642,16 +1667,16 @@ nfsd4_exchange_id(struct svc_rqst *rqstp,
         if (exid->flags & ~EXCHGID4_FLAG_MASK_A)
                 return nfserr_inval;
 
-        /* Currently only support SP4_NONE */
         switch (exid->spa_how) {
+        case SP4_MACH_CRED:
+                if (!svc_rqst_integrity_protected(rqstp))
+                        return nfserr_inval;
         case SP4_NONE:
                 break;
         default:                                /* checked by xdr code */
                 WARN_ON_ONCE(1);
         case SP4_SSV:
                 return nfserr_encr_alg_unsupp;
-        case SP4_MACH_CRED:
-                return nfserr_serverfault;      /* no excuse :-/ */
         }
 
         /* Cases below refer to rfc 5661 section 18.35.4: */
@@ -1666,6 +1691,10 @@ nfsd4_exchange_id(struct svc_rqst *rqstp,
                                 status = nfserr_inval;
                                 goto out;
                         }
+                        if (!mach_creds_match(conf, rqstp)) {
+                                status = nfserr_wrong_cred;
+                                goto out;
+                        }
                         if (!creds_match) { /* case 9 */
                                 status = nfserr_perm;
                                 goto out;
@@ -1713,6 +1742,7 @@ out_new:
                 goto out;
         }
         new->cl_minorversion = cstate->minorversion;
+        new->cl_mach_cred = (exid->spa_how == SP4_MACH_CRED);
 
         gen_clid(new, nn);
         add_to_unconfirmed(new);
@@ -1877,6 +1907,9 @@ nfsd4_create_session(struct svc_rqst *rqstp,
         WARN_ON_ONCE(conf && unconf);
 
         if (conf) {
+                status = nfserr_wrong_cred;
+                if (!mach_creds_match(conf, rqstp))
+                        goto out_free_conn;
                 cs_slot = &conf->cl_cs_slot;
                 status = check_slot_seqid(cr_ses->seqid, cs_slot->sl_seqid, 0);
                 if (status == nfserr_replay_cache) {
@@ -1893,6 +1926,9 @@ nfsd4_create_session(struct svc_rqst *rqstp,
                         status = nfserr_clid_inuse;
                         goto out_free_conn;
                 }
+                status = nfserr_wrong_cred;
+                if (!mach_creds_match(unconf, rqstp))
+                        goto out_free_conn;
                 cs_slot = &unconf->cl_cs_slot;
                 status = check_slot_seqid(cr_ses->seqid, cs_slot->sl_seqid, 0);
                 if (status) {
@@ -1989,6 +2025,9 @@ __be32 nfsd4_bind_conn_to_session(struct svc_rqst *rqstp,
         status = nfserr_badsession;
         if (!session)
                 goto out;
+        status = nfserr_wrong_cred;
+        if (!mach_creds_match(session->se_client, rqstp))
+                goto out;
         status = nfsd4_map_bcts_dir(&bcts->dir);
         if (status)
                 goto out;
@@ -2031,6 +2070,9 @@ nfsd4_destroy_session(struct svc_rqst *r,
         status = nfserr_badsession;
         if (!ses)
                 goto out_client_lock;
+        status = nfserr_wrong_cred;
+        if (!mach_creds_match(ses->se_client, r))
+                goto out_client_lock;
         status = mark_session_dead_locked(ses);
         if (status)
                 goto out_client_lock;
@@ -2061,26 +2103,31 @@ static struct nfsd4_conn *__nfsd4_find_conn(struct svc_xprt *xpt, struct nfsd4_s
         return NULL;
 }
 
-static void nfsd4_sequence_check_conn(struct nfsd4_conn *new, struct nfsd4_session *ses)
+static __be32 nfsd4_sequence_check_conn(struct nfsd4_conn *new, struct nfsd4_session *ses)
 {
         struct nfs4_client *clp = ses->se_client;
         struct nfsd4_conn *c;
+        __be32 status = nfs_ok;
         int ret;
 
         spin_lock(&clp->cl_lock);
         c = __nfsd4_find_conn(new->cn_xprt, ses);
-        if (c) {
-                spin_unlock(&clp->cl_lock);
-                free_conn(new);
-                return;
-        }
+        if (c)
+                goto out_free;
+        status = nfserr_conn_not_bound_to_session;
+        if (clp->cl_mach_cred)
+                goto out_free;
         __nfsd4_hash_conn(new, ses);
         spin_unlock(&clp->cl_lock);
         ret = nfsd4_register_conn(new);
         if (ret)
                 /* oops; xprt is already down: */
                 nfsd4_conn_lost(&new->cn_xpt_user);
-        return;
+        return nfs_ok;
+out_free:
+        spin_unlock(&clp->cl_lock);
+        free_conn(new);
+        return status;
 }
 
 static bool nfsd4_session_too_many_ops(struct svc_rqst *rqstp, struct nfsd4_session *session)
@@ -2172,8 +2219,10 @@ nfsd4_sequence(struct svc_rqst *rqstp,
         if (status)
                 goto out_put_session;
 
-        nfsd4_sequence_check_conn(conn, session);
+        status = nfsd4_sequence_check_conn(conn, session);
         conn = NULL;
+        if (status)
+                goto out_put_session;
 
         /* Success! bump slot seqid */
         slot->sl_seqid = seq->seqid;
@@ -2235,7 +2284,10 @@ nfsd4_destroy_clientid(struct svc_rqst *rqstp, struct nfsd4_compound_state *csta
                 status = nfserr_stale_clientid;
                 goto out;
         }
-
+        if (!mach_creds_match(clp, rqstp)) {
+                status = nfserr_wrong_cred;
+                goto out;
+        }
         expire_client(clp);
 out:
         nfs4_unlock_state();
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 170ea7e1ae25..3126210383bd 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3321,6 +3321,14 @@ nfsd4_encode_write(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_w
         return nfserr;
 }
 
+static const u32 nfs4_minimal_spo_must_enforce[2] = {
+        [1] = 1 << (OP_BIND_CONN_TO_SESSION - 32) |
+              1 << (OP_EXCHANGE_ID - 32) |
+              1 << (OP_CREATE_SESSION - 32) |
+              1 << (OP_DESTROY_SESSION - 32) |
+              1 << (OP_DESTROY_CLIENTID - 32)
+};
+
 static __be32
 nfsd4_encode_exchange_id(struct nfsd4_compoundres *resp, __be32 nfserr,
                          struct nfsd4_exchange_id *exid)
@@ -3359,6 +3367,20 @@ nfsd4_encode_exchange_id(struct nfsd4_compoundres *resp, __be32 nfserr,
         /* state_protect4_r. Currently only support SP4_NONE */
         BUG_ON(exid->spa_how != SP4_NONE);
         WRITE32(exid->spa_how);
+        switch (exid->spa_how) {
+        case SP4_NONE:
+                break;
+        case SP4_MACH_CRED:
+                /* spo_must_enforce bitmap: */
+                WRITE32(2);
+                WRITE32(nfs4_minimal_spo_must_enforce[0]);
+                WRITE32(nfs4_minimal_spo_must_enforce[1]);
+                /* empty spo_must_allow bitmap: */
+                WRITE32(0);
+                break;
+        default:
+                WARN_ON_ONCE(1);
+        }
 
         /* The server_owner struct */
         WRITE64(minor_id);      /* Minor id */
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 274e2a114e05..424d8f5f2317 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -246,6 +246,7 @@ struct nfs4_client {
         nfs4_verifier           cl_verifier;    /* generated by client */
         time_t                  cl_time;        /* time of last lease renewal */
         struct sockaddr_storage cl_addr;        /* client ipaddress */
+        bool                    cl_mach_cred;   /* SP4_MACH_CRED in force */
         struct svc_cred         cl_cred;        /* setclientid principal */
         clientid_t              cl_clientid;    /* generated by server */
         nfs4_verifier           cl_confirm;     /* generated by server */