/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2012, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * lustre/ptlrpc/gss/gss_keyring.c
 *
 * Author: Eric Mei <ericm@clusterfs.com>
 */

#define DEBUG_SUBSYSTEM S_SEC
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/dcache.h>
#include <linux/fs.h>
#include <linux/crypto.h>
#include <linux/key.h>
#include <linux/keyctl.h>
#include <linux/key-type.h>
#include <linux/mutex.h>
#include <asm/atomic.h>

#include <obd.h>
#include <obd_class.h>
#include <obd_support.h>
#include <lustre/lustre_idl.h>
#include <lustre_sec.h>
#include <lustre_net.h>
#include <lustre_import.h>

#include "gss_err.h"
#include "gss_internal.h"
#include "gss_api.h"

static struct ptlrpc_sec_policy gss_policy_keyring;
static struct ptlrpc_ctx_ops gss_keyring_ctxops;
static struct key_type gss_key_type;

static int sec_install_rctx_kr(struct ptlrpc_sec *sec,
                               struct ptlrpc_svc_ctx *svc_ctx);

/*
 * the timeout is only for the case that upcall child process die abnormally.
 * in any other cases it should finally update kernel key.
 *
 * FIXME we'd better to incorporate the client & server side upcall timeouts
 * into the framework of Adaptive Timeouts, but we need to figure out how to
 * make sure that kernel knows the upcall processes is in-progress or died
 * unexpectedly.
 */
#define KEYRING_UPCALL_TIMEOUT  (obd_timeout + obd_timeout)

/****************************************
 * internal helpers                  *
 ****************************************/

#define DUMP_PROCESS_KEYRINGS(tsk)                                      \
{                                                                       \
        CWARN("DUMP PK: %s[%u,%u/%u](<-%s[%u,%u/%u]): "                 \
              "a %d, t %d, p %d, s %d, u %d, us %d, df %d\n",           \
              tsk->comm, tsk->pid, tsk->uid, tsk->fsuid,                \
              tsk->parent->comm, tsk->parent->pid,                      \
              tsk->parent->uid, tsk->parent->fsuid,                     \
              tsk->request_key_auth ?                                   \
              tsk->request_key_auth->serial : 0,                        \
              key_cred(tsk)->thread_keyring ?                           \
              key_cred(tsk)->thread_keyring->serial : 0,                \
              key_tgcred(tsk)->process_keyring ?                        \
              key_tgcred(tsk)->process_keyring->serial : 0,             \
              key_tgcred(tsk)->session_keyring ?                        \
              key_tgcred(tsk)->session_keyring->serial : 0,             \
              key_cred(tsk)->user->uid_keyring ?                        \
              key_cred(tsk)->user->uid_keyring->serial : 0,             \
              key_cred(tsk)->user->session_keyring ?                    \
              key_cred(tsk)->user->session_keyring->serial : 0,         \
              key_cred(tsk)->jit_keyring                                \
             );                                                         \
}

#define DUMP_KEY(key)                                              \
{                                                                      \
        CWARN("DUMP KEY: %p(%d) ref %d u%u/g%u desc %s\n",            \
              key, key->serial, atomic_read(&key->usage),              \
              key->uid, key->gid,                                      \
              key->description ? key->description : "n/a"              \
             );                                                  \
}

#define key_cred(tsk)   ((tsk)->cred)
#define key_tgcred(tsk) ((tsk)->cred->tgcred)

static inline void keyring_upcall_lock(struct gss_sec_keyring *gsec_kr)
{
#ifdef HAVE_KEYRING_UPCALL_SERIALIZED
        mutex_lock(&gsec_kr->gsk_uc_lock);
#endif
}

static inline void keyring_upcall_unlock(struct gss_sec_keyring *gsec_kr)
{
#ifdef HAVE_KEYRING_UPCALL_SERIALIZED
        mutex_unlock(&gsec_kr->gsk_uc_lock);
#endif
}

static inline void key_revoke_locked(struct key *key)
{
        set_bit(KEY_FLAG_REVOKED, &key->flags);
}

static void ctx_upcall_timeout_kr(unsigned long data)
{
        struct ptlrpc_cli_ctx *ctx = (struct ptlrpc_cli_ctx *) data;
        struct key          *key = ctx2gctx_keyring(ctx)->gck_key;

        CWARN("ctx %p, key %p\n", ctx, key);

        LASSERT(key);

        cli_ctx_expire(ctx);
        key_revoke_locked(key);
}

static
void ctx_start_timer_kr(struct ptlrpc_cli_ctx *ctx, long timeout)
{
        struct gss_cli_ctx_keyring *gctx_kr = ctx2gctx_keyring(ctx);
        struct timer_list         *timer = gctx_kr->gck_timer;

        LASSERT(timer);

        CDEBUG(D_SEC, "ctx %p: start timer %lds\n", ctx, timeout);
        timeout = timeout * HZ + cfs_time_current();

        init_timer(timer);
        timer->expires = timeout;
        timer->data = (unsigned long ) ctx;
        timer->function = ctx_upcall_timeout_kr;

        add_timer(timer);
}

/*
 * caller should make sure no race with other threads
 */
static
void ctx_clear_timer_kr(struct ptlrpc_cli_ctx *ctx)
{
        struct gss_cli_ctx_keyring *gctx_kr = ctx2gctx_keyring(ctx);
        struct timer_list         *timer = gctx_kr->gck_timer;

        if (timer == NULL)
                return;

        CDEBUG(D_SEC, "ctx %p, key %p\n", ctx, gctx_kr->gck_key);

        gctx_kr->gck_timer = NULL;

        del_singleshot_timer_sync(timer);

        OBD_FREE_PTR(timer);
}

static
struct ptlrpc_cli_ctx *ctx_create_kr(struct ptlrpc_sec *sec,
                                     struct vfs_cred *vcred)
{
        struct ptlrpc_cli_ctx      *ctx;
        struct gss_cli_ctx_keyring *gctx_kr;

        OBD_ALLOC_PTR(gctx_kr);
        if (gctx_kr == NULL)
                return NULL;

        OBD_ALLOC_PTR(gctx_kr->gck_timer);
        if (gctx_kr->gck_timer == NULL) {
                OBD_FREE_PTR(gctx_kr);
                return NULL;
        }
        init_timer(gctx_kr->gck_timer);

        ctx = &gctx_kr->gck_base.gc_base;

        if (gss_cli_ctx_init_common(sec, ctx, &gss_keyring_ctxops, vcred)) {
                OBD_FREE_PTR(gctx_kr->gck_timer);
                OBD_FREE_PTR(gctx_kr);
                return NULL;
        }

        ctx->cc_expire = cfs_time_current_sec() + KEYRING_UPCALL_TIMEOUT;
        clear_bit(PTLRPC_CTX_NEW_BIT, &ctx->cc_flags);
        atomic_inc(&ctx->cc_refcount); /* for the caller */

        return ctx;
}

static void ctx_destroy_kr(struct ptlrpc_cli_ctx *ctx)
{
        struct ptlrpc_sec         *sec = ctx->cc_sec;
        struct gss_cli_ctx_keyring *gctx_kr = ctx2gctx_keyring(ctx);

        CDEBUG(D_SEC, "destroying ctx %p\n", ctx);

        /* at this time the association with key has been broken. */
        LASSERT(sec);
        LASSERT(atomic_read(&sec->ps_refcount) > 0);
        LASSERT(atomic_read(&sec->ps_nctx) > 0);
        LASSERT(test_bit(PTLRPC_CTX_CACHED_BIT, &ctx->cc_flags) == 0);
        LASSERT(gctx_kr->gck_key == NULL);

        ctx_clear_timer_kr(ctx);
        LASSERT(gctx_kr->gck_timer == NULL);

        if (gss_cli_ctx_fini_common(sec, ctx))
                return;

        OBD_FREE_PTR(gctx_kr);

        atomic_dec(&sec->ps_nctx);
        sptlrpc_sec_put(sec);
}

static void ctx_release_kr(struct ptlrpc_cli_ctx *ctx, int sync)
{
        if (sync) {
                ctx_destroy_kr(ctx);
        } else {
                atomic_inc(&ctx->cc_refcount);
                sptlrpc_gc_add_ctx(ctx);
        }
}

static void ctx_put_kr(struct ptlrpc_cli_ctx *ctx, int sync)
{
        LASSERT(atomic_read(&ctx->cc_refcount) > 0);

        if (atomic_dec_and_test(&ctx->cc_refcount))
                ctx_release_kr(ctx, sync);
}

/*
 * key <-> ctx association and rules:
 * - ctx might not bind with any key
 * - key/ctx binding is protected by key semaphore (if the key present)
 * - key and ctx each take a reference of the other
 * - ctx enlist/unlist is protected by ctx spinlock
 * - never enlist a ctx after it's been unlisted
 * - whoever do enlist should also do bind, lock key before enlist:
 *   - lock key -> lock ctx -> enlist -> unlock ctx -> bind -> unlock key
 * - whoever do unlist should also do unbind:
 *   - lock key -> lock ctx -> unlist -> unlock ctx -> unbind -> unlock key
 *   - lock ctx -> unlist -> unlock ctx -> lock key -> unbind -> unlock key
 */

static inline void spin_lock_if(spinlock_t *lock, int condition)
{
        if (condition)
                spin_lock(lock);
}

static inline void spin_unlock_if(spinlock_t *lock, int condition)
{
        if (condition)
                spin_unlock(lock);
}

static void ctx_enlist_kr(struct ptlrpc_cli_ctx *ctx, int is_root, int locked)
{
        struct ptlrpc_sec      *sec = ctx->cc_sec;
        struct gss_sec_keyring *gsec_kr = sec2gsec_keyring(sec);

        LASSERT(!test_bit(PTLRPC_CTX_CACHED_BIT, &ctx->cc_flags));
        LASSERT(atomic_read(&ctx->cc_refcount) > 0);

        spin_lock_if(&sec->ps_lock, !locked);

        atomic_inc(&ctx->cc_refcount);
        set_bit(PTLRPC_CTX_CACHED_BIT, &ctx->cc_flags);
        hlist_add_head(&ctx->cc_cache, &gsec_kr->gsk_clist);
        if (is_root)
                gsec_kr->gsk_root_ctx = ctx;

        spin_unlock_if(&sec->ps_lock, !locked);
}

/*
 * Note after this get called, caller should not access ctx again because
 * it might have been freed, unless caller hold at least one refcount of
 * the ctx.
 *
 * return non-zero if we indeed unlist this ctx.
 */
static int ctx_unlist_kr(struct ptlrpc_cli_ctx *ctx, int locked)
{
        struct ptlrpc_sec       *sec = ctx->cc_sec;
        struct gss_sec_keyring  *gsec_kr = sec2gsec_keyring(sec);

        /* if hashed bit has gone, leave the job to somebody who is doing it */
        if (test_and_clear_bit(PTLRPC_CTX_CACHED_BIT, &ctx->cc_flags) == 0)
                return 0;

        /* drop ref inside spin lock to prevent race with other operations */
        spin_lock_if(&sec->ps_lock, !locked);

        if (gsec_kr->gsk_root_ctx == ctx)
                gsec_kr->gsk_root_ctx = NULL;
        hlist_del_init(&ctx->cc_cache);
        atomic_dec(&ctx->cc_refcount);

        spin_unlock_if(&sec->ps_lock, !locked);

        return 1;
}

/*
 * bind a key with a ctx together.
 * caller must hold write lock of the key, as well as ref on key & ctx.
 */
static void bind_key_ctx(struct key *key, struct ptlrpc_cli_ctx *ctx)
{
        LASSERT(atomic_read(&ctx->cc_refcount) > 0);
        LASSERT(atomic_read(&key->usage) > 0);
        LASSERT(ctx2gctx_keyring(ctx)->gck_key == NULL);
        LASSERT(key->payload.data == NULL);

        /* at this time context may or may not in list. */
        key_get(key);
        atomic_inc(&ctx->cc_refcount);
        ctx2gctx_keyring(ctx)->gck_key = key;
        key->payload.data = ctx;
}

/*
 * unbind a key and a ctx.
 * caller must hold write lock, as well as a ref of the key.
 */
static void unbind_key_ctx(struct key *key, struct ptlrpc_cli_ctx *ctx)
{
        LASSERT(key->payload.data == ctx);
        LASSERT(test_bit(PTLRPC_CTX_CACHED_BIT, &ctx->cc_flags) == 0);

        /* must revoke the key, or others may treat it as newly created */
        key_revoke_locked(key);

        key->payload.data = NULL;
        ctx2gctx_keyring(ctx)->gck_key = NULL;

        /* once ctx get split from key, the timer is meaningless */
        ctx_clear_timer_kr(ctx);

        ctx_put_kr(ctx, 1);
        key_put(key);
}

/*
 * given a ctx, unbind with its coupled key, if any.
 * unbind could only be called once, so we don't worry the key be released
 * by someone else.
 */
static void unbind_ctx_kr(struct ptlrpc_cli_ctx *ctx)
{
        struct key      *key = ctx2gctx_keyring(ctx)->gck_key;

        if (key) {
                LASSERT(key->payload.data == ctx);

                key_get(key);
                down_write(&key->sem);
                unbind_key_ctx(key, ctx);
                up_write(&key->sem);
                key_put(key);
        }
}

/*
 * given a key, unbind with its coupled ctx, if any.
 * caller must hold write lock, as well as a ref of the key.
 */
static void unbind_key_locked(struct key *key)
{
        struct ptlrpc_cli_ctx   *ctx = key->payload.data;

        if (ctx)
                unbind_key_ctx(key, ctx);
}

/*
 * unlist a ctx, and unbind from coupled key
 */
static void kill_ctx_kr(struct ptlrpc_cli_ctx *ctx)
{
        if (ctx_unlist_kr(ctx, 0))
                unbind_ctx_kr(ctx);
}

/*
 * given a key, unlist and unbind with the coupled ctx (if any).
 * caller must hold write lock, as well as a ref of the key.
 */
static void kill_key_locked(struct key *key)
{
        struct ptlrpc_cli_ctx *ctx = key->payload.data;

        if (ctx && ctx_unlist_kr(ctx, 0))
                unbind_key_locked(key);
}

/*
 * caller should hold one ref on contexts in freelist.
 */
static void dispose_ctx_list_kr(struct hlist_head *freelist)
{
        struct hlist_node      *next;
        struct ptlrpc_cli_ctx  *ctx;
        struct gss_cli_ctx     *gctx;

        hlist_for_each_entry_safe(ctx, next, freelist, cc_cache) {
                hlist_del_init(&ctx->cc_cache);

                /* reverse ctx: update current seq to buddy svcctx if exist.
                 * ideally this should be done at gss_cli_ctx_finalize(), but
                 * the ctx destroy could be delayed by:
                 *  1) ctx still has reference;
                 *  2) ctx destroy is asynchronous;
                 * and reverse import call inval_all_ctx() require this be done
                 *_immediately_ otherwise newly created reverse ctx might copy
                 * the very old sequence number from svcctx. */
                gctx = ctx2gctx(ctx);
                if (!rawobj_empty(&gctx->gc_svc_handle) &&
                    sec_is_reverse(gctx->gc_base.cc_sec)) {
                        gss_svc_upcall_update_sequence(&gctx->gc_svc_handle,
                                        (__u32) atomic_read(&gctx->gc_seq));
                }

                /* we need to wakeup waiting reqs here. the context might
                 * be forced released before upcall finished, then the
                 * late-arrived downcall can't find the ctx even. */
                sptlrpc_cli_ctx_wakeup(ctx);

                unbind_ctx_kr(ctx);
                ctx_put_kr(ctx, 0);
        }
}

/*
 * lookup a root context directly in a sec, return root ctx with a
 * reference taken or NULL.
 */
static
struct ptlrpc_cli_ctx * sec_lookup_root_ctx_kr(struct ptlrpc_sec *sec)
{
        struct gss_sec_keyring  *gsec_kr = sec2gsec_keyring(sec);
        struct ptlrpc_cli_ctx   *ctx = NULL;

        spin_lock(&sec->ps_lock);

        ctx = gsec_kr->gsk_root_ctx;

        if (ctx == NULL && unlikely(sec_is_reverse(sec))) {
                struct ptlrpc_cli_ctx  *tmp;

                /* reverse ctx, search root ctx in list, choose the one
                 * with shortest expire time, which is most possibly have
                 * an established peer ctx at client side. */
                hlist_for_each_entry(tmp, &gsec_kr->gsk_clist, cc_cache) {
                        if (ctx == NULL || ctx->cc_expire == 0 ||
                            ctx->cc_expire > tmp->cc_expire) {
                                ctx = tmp;
                                /* promote to be root_ctx */
                                gsec_kr->gsk_root_ctx = ctx;
                        }
                }
        }

        if (ctx) {
                LASSERT(atomic_read(&ctx->cc_refcount) > 0);
                LASSERT(!hlist_empty(&gsec_kr->gsk_clist));
                atomic_inc(&ctx->cc_refcount);
        }

        spin_unlock(&sec->ps_lock);

        return ctx;
}

#define RVS_CTX_EXPIRE_NICE    (10)

static
void rvs_sec_install_root_ctx_kr(struct ptlrpc_sec *sec,
                                 struct ptlrpc_cli_ctx *new_ctx,
                                 struct key *key)
{
        struct gss_sec_keyring *gsec_kr = sec2gsec_keyring(sec);
        struct ptlrpc_cli_ctx  *ctx;
        cfs_time_t            now;

        LASSERT(sec_is_reverse(sec));

        spin_lock(&sec->ps_lock);

        now = cfs_time_current_sec();

        /* set all existing ctxs short expiry */
        hlist_for_each_entry(ctx, &gsec_kr->gsk_clist, cc_cache) {
                if (ctx->cc_expire > now + RVS_CTX_EXPIRE_NICE) {
                        ctx->cc_early_expire = 1;
                        ctx->cc_expire = now + RVS_CTX_EXPIRE_NICE;
                }
        }

        /* if there's root_ctx there, instead obsolete the current
         * immediately, we leave it continue operating for a little while.
         * hopefully when the first backward rpc with newest ctx send out,
         * the client side already have the peer ctx well established. */
        ctx_enlist_kr(new_ctx, gsec_kr->gsk_root_ctx ? 0 : 1, 1);

        if (key)
                bind_key_ctx(key, new_ctx);

        spin_unlock(&sec->ps_lock);
}

static void construct_key_desc(void *buf, int bufsize,
                               struct ptlrpc_sec *sec, uid_t uid)
{
        snprintf(buf, bufsize, "%d@%x", uid, sec->ps_id);
        ((char *)buf)[bufsize - 1] = '\0';
}

/****************************************
 * sec apis                          *
 ****************************************/

static
struct ptlrpc_sec * gss_sec_create_kr(struct obd_import *imp,
                                      struct ptlrpc_svc_ctx *svcctx,
                                      struct sptlrpc_flavor *sf)
{
        struct gss_sec_keyring  *gsec_kr;

        OBD_ALLOC(gsec_kr, sizeof(*gsec_kr));
        if (gsec_kr == NULL)
                return NULL;

        INIT_HLIST_HEAD(&gsec_kr->gsk_clist);
        gsec_kr->gsk_root_ctx = NULL;
        mutex_init(&gsec_kr->gsk_root_uc_lock);
#ifdef HAVE_KEYRING_UPCALL_SERIALIZED
        mutex_init(&gsec_kr->gsk_uc_lock);
#endif

        if (gss_sec_create_common(&gsec_kr->gsk_base, &gss_policy_keyring,
                                  imp, svcctx, sf))
                goto err_free;

        if (svcctx != NULL &&
            sec_install_rctx_kr(&gsec_kr->gsk_base.gs_base, svcctx)) {
                gss_sec_destroy_common(&gsec_kr->gsk_base);
                goto err_free;
        }

        return &gsec_kr->gsk_base.gs_base;

err_free:
        OBD_FREE(gsec_kr, sizeof(*gsec_kr));
        return NULL;
}

static
void gss_sec_destroy_kr(struct ptlrpc_sec *sec)
{
        struct gss_sec    *gsec = sec2gsec(sec);
        struct gss_sec_keyring  *gsec_kr = sec2gsec_keyring(sec);

        CDEBUG(D_SEC, "destroy %s@%p\n", sec->ps_policy->sp_name, sec);

        LASSERT(hlist_empty(&gsec_kr->gsk_clist));
        LASSERT(gsec_kr->gsk_root_ctx == NULL);

        gss_sec_destroy_common(gsec);

        OBD_FREE(gsec_kr, sizeof(*gsec_kr));
}

static inline int user_is_root(struct ptlrpc_sec *sec, struct vfs_cred *vcred)
{
        /* except the ROOTONLY flag, treat it as root user only if real uid
         * is 0, euid/fsuid being 0 are handled as setuid scenarios */
        if (sec_is_rootonly(sec) || (vcred->vc_uid == 0))
                return 1;
        else
                return 0;
}

/*
 * unlink request key from it's ring, which is linked during request_key().
 * sadly, we have to 'guess' which keyring it's linked to.
 *
 * FIXME this code is fragile, depend on how request_key_link() is implemented.
 */
static void request_key_unlink(struct key *key)
{
        struct task_struct *tsk = current;
        struct key *ring;

        switch (key_cred(tsk)->jit_keyring) {
        case KEY_REQKEY_DEFL_DEFAULT:
        case KEY_REQKEY_DEFL_THREAD_KEYRING:
                ring = key_get(key_cred(tsk)->thread_keyring);
                if (ring)
                        break;
        case KEY_REQKEY_DEFL_PROCESS_KEYRING:
                ring = key_get(key_tgcred(tsk)->process_keyring);
                if (ring)
                        break;
        case KEY_REQKEY_DEFL_SESSION_KEYRING:
                rcu_read_lock();
                ring = key_get(rcu_dereference(key_tgcred(tsk)
                                               ->session_keyring));
                rcu_read_unlock();
                if (ring)
                        break;
        case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
                ring = key_get(key_cred(tsk)->user->session_keyring);
                break;
        case KEY_REQKEY_DEFL_USER_KEYRING:
                ring = key_get(key_cred(tsk)->user->uid_keyring);
                break;
        case KEY_REQKEY_DEFL_GROUP_KEYRING:
        default:
                LBUG();
        }

        LASSERT(ring);
        key_unlink(ring, key);
        key_put(ring);
}

static
struct ptlrpc_cli_ctx * gss_sec_lookup_ctx_kr(struct ptlrpc_sec *sec,
                                              struct vfs_cred *vcred,
                                              int create, int remove_dead)
{
        struct obd_import       *imp = sec->ps_import;
        struct gss_sec_keyring  *gsec_kr = sec2gsec_keyring(sec);
        struct ptlrpc_cli_ctx   *ctx = NULL;
        unsigned int         is_root = 0, create_new = 0;
        struct key            *key;
        char                 desc[24];
        char                *coinfo;
        int                   coinfo_size;
        char                *co_flags = "";

        LASSERT(imp != NULL);

        is_root = user_is_root(sec, vcred);

        /* a little bit optimization for root context */
        if (is_root) {
                ctx = sec_lookup_root_ctx_kr(sec);
                /*
                 * Only lookup directly for REVERSE sec, which should
                 * always succeed.
                 */
                if (ctx || sec_is_reverse(sec))
                        return ctx;
        }

        LASSERT(create != 0);

        /* for root context, obtain lock and check again, this time hold
         * the root upcall lock, make sure nobody else populated new root
         * context after last check. */
        if (is_root) {
                mutex_lock(&gsec_kr->gsk_root_uc_lock);

                ctx = sec_lookup_root_ctx_kr(sec);
                if (ctx)
                        goto out;

                /* update reverse handle for root user */
                sec2gsec(sec)->gs_rvs_hdl = gss_get_next_ctx_index();

                switch (sec->ps_part) {
                case LUSTRE_SP_MDT:
                        co_flags = "m";
                        break;
                case LUSTRE_SP_OST:
                        co_flags = "o";
                        break;
                case LUSTRE_SP_MGC:
                        co_flags = "rmo";
                        break;
                case LUSTRE_SP_CLI:
                        co_flags = "r";
                        break;
                case LUSTRE_SP_MGS:
                default:
                        LBUG();
                }
        }

        /* in case of setuid, key will be constructed as owner of fsuid/fsgid,
         * but we do authentication based on real uid/gid. the key permission
         * bits will be exactly as POS_ALL, so only processes who subscribed
         * this key could have the access, although the quota might be counted
         * on others (fsuid/fsgid).
         *
         * keyring will use fsuid/fsgid as upcall parameters, so we have to
         * encode real uid/gid into callout info.
         */

        construct_key_desc(desc, sizeof(desc), sec, vcred->vc_uid);

        /* callout info format:
         * secid:mech:uid:gid:flags:svc_type:peer_nid:target_uuid
         */
        coinfo_size = sizeof(struct obd_uuid) + MAX_OBD_NAME + 64;
        OBD_ALLOC(coinfo, coinfo_size);
        if (coinfo == NULL)
                goto out;

        snprintf(coinfo, coinfo_size, "%d:%s:%u:%u:%s:%d:"LPX64":%s",
                 sec->ps_id, sec2gsec(sec)->gs_mech->gm_name,
                 vcred->vc_uid, vcred->vc_gid,
                 co_flags, import_to_gss_svc(imp),
                 imp->imp_connection->c_peer.nid, imp->imp_obd->obd_name);

        CDEBUG(D_SEC, "requesting key for %s\n", desc);

        keyring_upcall_lock(gsec_kr);
        key = request_key(&gss_key_type, desc, coinfo);
        keyring_upcall_unlock(gsec_kr);

        OBD_FREE(coinfo, coinfo_size);

        if (IS_ERR(key)) {
                CERROR("failed request key: %ld\n", PTR_ERR(key));
                goto out;
        }
        CDEBUG(D_SEC, "obtained key %08x for %s\n", key->serial, desc);

        /* once payload.data was pointed to a ctx, it never changes until
         * we de-associate them; but parallel request_key() may return
         * a key with payload.data == NULL at the same time. so we still
         * need wirtelock of key->sem to serialize them. */
        down_write(&key->sem);

        if (likely(key->payload.data != NULL)) {
                ctx = key->payload.data;

                LASSERT(atomic_read(&ctx->cc_refcount) >= 1);
                LASSERT(ctx2gctx_keyring(ctx)->gck_key == key);
                LASSERT(atomic_read(&key->usage) >= 2);

                /* simply take a ref and return. it's upper layer's
                 * responsibility to detect & replace dead ctx. */
                atomic_inc(&ctx->cc_refcount);
        } else {
                /* pre initialization with a cli_ctx. this can't be done in
                 * key_instantiate() because we'v no enough information
                 * there. */
                ctx = ctx_create_kr(sec, vcred);
                if (ctx != NULL) {
                        ctx_enlist_kr(ctx, is_root, 0);
                        bind_key_ctx(key, ctx);

                        ctx_start_timer_kr(ctx, KEYRING_UPCALL_TIMEOUT);

                        CDEBUG(D_SEC, "installed key %p <-> ctx %p (sec %p)\n",
                               key, ctx, sec);
                } else {
                        /* we'd prefer to call key_revoke(), but we more like
                         * to revoke it within this key->sem locked period. */
                        key_revoke_locked(key);
                }

                create_new = 1;
        }

        up_write(&key->sem);

        if (is_root && create_new)
                request_key_unlink(key);

        key_put(key);
out:
        if (is_root)
                mutex_unlock(&gsec_kr->gsk_root_uc_lock);
        return ctx;
}

static
void gss_sec_release_ctx_kr(struct ptlrpc_sec *sec,
                            struct ptlrpc_cli_ctx *ctx,
                            int sync)
{
        LASSERT(atomic_read(&sec->ps_refcount) > 0);
        LASSERT(atomic_read(&ctx->cc_refcount) == 0);
        ctx_release_kr(ctx, sync);
}

/*
 * flush context of normal user, we must resort to keyring itself to find out
 * contexts which belong to me.
 *
 * Note here we suppose only to flush _my_ context, the "uid" will
 * be ignored in the search.
 */
static
void flush_user_ctx_cache_kr(struct ptlrpc_sec *sec,
                             uid_t uid,
                             int grace, int force)
{
        struct key            *key;
        char                 desc[24];

        /* nothing to do for reverse or rootonly sec */
        if (sec_is_reverse(sec) || sec_is_rootonly(sec))
                return;

        construct_key_desc(desc, sizeof(desc), sec, uid);

        /* there should be only one valid key, but we put it in the
         * loop in case of any weird cases */
        for (;;) {
                key = request_key(&gss_key_type, desc, NULL);
                if (IS_ERR(key)) {
                        CDEBUG(D_SEC, "No more key found for current user\n");
                        break;
                }

                down_write(&key->sem);

                kill_key_locked(key);

                /* kill_key_locked() should usually revoke the key, but we
                 * revoke it again to make sure, e.g. some case the key may
                 * not well coupled with a context. */
                key_revoke_locked(key);

                up_write(&key->sem);

                key_put(key);
        }
}

/*
 * flush context of root or all, we iterate through the list.
 */
static
void flush_spec_ctx_cache_kr(struct ptlrpc_sec *sec,
                             uid_t uid,
                             int grace, int force)
{
        struct gss_sec_keyring *gsec_kr;
        struct hlist_head       freelist = HLIST_HEAD_INIT;
        struct hlist_node      *next;
        struct ptlrpc_cli_ctx  *ctx;

        gsec_kr = sec2gsec_keyring(sec);

        spin_lock(&sec->ps_lock);
        hlist_for_each_entry_safe(ctx, next,
                                      &gsec_kr->gsk_clist, cc_cache) {
                LASSERT(atomic_read(&ctx->cc_refcount) > 0);

                if (uid != -1 && uid != ctx->cc_vcred.vc_uid)
                        continue;

                /* at this moment there's at least 2 base reference:
                 * key association and in-list. */
                if (atomic_read(&ctx->cc_refcount) > 2) {
                        if (!force)
                                continue;
                        CWARN("flush busy ctx %p(%u->%s, extra ref %d)\n",
                              ctx, ctx->cc_vcred.vc_uid,
                              sec2target_str(ctx->cc_sec),
                              atomic_read(&ctx->cc_refcount) - 2);
                }

                set_bit(PTLRPC_CTX_DEAD_BIT, &ctx->cc_flags);
                if (!grace)
                        clear_bit(PTLRPC_CTX_UPTODATE_BIT, &ctx->cc_flags);

                atomic_inc(&ctx->cc_refcount);

                if (ctx_unlist_kr(ctx, 1)) {
                        hlist_add_head(&ctx->cc_cache, &freelist);
                } else {
                        LASSERT(atomic_read(&ctx->cc_refcount) >= 2);
                        atomic_dec(&ctx->cc_refcount);
                }
        }
        spin_unlock(&sec->ps_lock);

        dispose_ctx_list_kr(&freelist);
}

static
int gss_sec_flush_ctx_cache_kr(struct ptlrpc_sec *sec,
                               uid_t uid, int grace, int force)
{
        CDEBUG(D_SEC, "sec %p(%d, nctx %d), uid %d, grace %d, force %d\n",
               sec, atomic_read(&sec->ps_refcount),
               atomic_read(&sec->ps_nctx),
               uid, grace, force);

        if (uid != -1 && uid != 0)
                flush_user_ctx_cache_kr(sec, uid, grace, force);
        else
                flush_spec_ctx_cache_kr(sec, uid, grace, force);

        return 0;
}

static
void gss_sec_gc_ctx_kr(struct ptlrpc_sec *sec)
{
        struct gss_sec_keyring *gsec_kr = sec2gsec_keyring(sec);
        struct hlist_head       freelist = HLIST_HEAD_INIT;
        struct hlist_node      *next;
        struct ptlrpc_cli_ctx  *ctx;

        CWARN("running gc\n");

        spin_lock(&sec->ps_lock);
        hlist_for_each_entry_safe(ctx, next,
                                      &gsec_kr->gsk_clist, cc_cache) {
                LASSERT(atomic_read(&ctx->cc_refcount) > 0);

                atomic_inc(&ctx->cc_refcount);

                if (cli_ctx_check_death(ctx) && ctx_unlist_kr(ctx, 1)) {
                        hlist_add_head(&ctx->cc_cache, &freelist);
                        CWARN("unhashed ctx %p\n", ctx);
                } else {
                        LASSERT(atomic_read(&ctx->cc_refcount) >= 2);
                        atomic_dec(&ctx->cc_refcount);
                }
        }
        spin_unlock(&sec->ps_lock);

        dispose_ctx_list_kr(&freelist);
}

static
int gss_sec_display_kr(struct ptlrpc_sec *sec, struct seq_file *seq)
{
        struct gss_sec_keyring *gsec_kr = sec2gsec_keyring(sec);
        struct hlist_node      *next;
        struct ptlrpc_cli_ctx  *ctx;
        struct gss_cli_ctx     *gctx;
        time_t            now = cfs_time_current_sec();

        spin_lock(&sec->ps_lock);
        hlist_for_each_entry_safe(ctx, next,
                                  &gsec_kr->gsk_clist, cc_cache) {
                struct key           *key;
                char                flags_str[40];
                char                mech[40];

                gctx = ctx2gctx(ctx);
                key = ctx2gctx_keyring(ctx)->gck_key;

                gss_cli_ctx_flags2str(ctx->cc_flags,
                                      flags_str, sizeof(flags_str));

                if (gctx->gc_mechctx)

                        lgss_display(gctx->gc_mechctx, mech, sizeof(mech));
                else
                        snprintf(mech, sizeof(mech), "N/A");
                mech[sizeof(mech) - 1] = '\0';

                seq_printf(seq, "%p: uid %u, ref %d, expire %ld(%+ld), fl %s, "
                           "seq %d, win %u, key %08x(ref %d), "
                           "hdl "LPX64":"LPX64", mech: %s\n",
                           ctx, ctx->cc_vcred.vc_uid,
                           atomic_read(&ctx->cc_refcount),
                           ctx->cc_expire,
                           ctx->cc_expire ?  ctx->cc_expire - now : 0,
                           flags_str,
                           atomic_read(&gctx->gc_seq),
                           gctx->gc_win,
                           key ? key->serial : 0,
                           key ? atomic_read(&key->usage) : 0,
                           gss_handle_to_u64(&gctx->gc_handle),
                           gss_handle_to_u64(&gctx->gc_svc_handle),
                           mech);
        }
        spin_unlock(&sec->ps_lock);

        return 0;
}

/****************************************
 * cli_ctx apis                  *
 ****************************************/

static
int gss_cli_ctx_refresh_kr(struct ptlrpc_cli_ctx *ctx)
{
        /* upcall is already on the way */
        return 0;
}

static
int gss_cli_ctx_validate_kr(struct ptlrpc_cli_ctx *ctx)
{
        LASSERT(atomic_read(&ctx->cc_refcount) > 0);
        LASSERT(ctx->cc_sec);

        if (cli_ctx_check_death(ctx)) {
                kill_ctx_kr(ctx);
                return 1;
        }

        if (cli_ctx_is_ready(ctx))
                return 0;
        return 1;
}

static
void gss_cli_ctx_die_kr(struct ptlrpc_cli_ctx *ctx, int grace)
{
        LASSERT(atomic_read(&ctx->cc_refcount) > 0);
        LASSERT(ctx->cc_sec);

        cli_ctx_expire(ctx);
        kill_ctx_kr(ctx);
}

/****************************************
 * (reverse) service                *
 ****************************************/

/*
 * reverse context could have nothing to do with keyrings. here we still keep
 * the version which bind to a key, for future reference.
 */
#define HAVE_REVERSE_CTX_NOKEY


static
int sec_install_rctx_kr(struct ptlrpc_sec *sec,
                        struct ptlrpc_svc_ctx *svc_ctx)
{
        struct ptlrpc_cli_ctx   *cli_ctx;
        struct vfs_cred   vcred = { 0, 0 };
        int                   rc;

        LASSERT(sec);
        LASSERT(svc_ctx);

        cli_ctx = ctx_create_kr(sec, &vcred);
        if (cli_ctx == NULL)
                return -ENOMEM;

        rc = gss_copy_rvc_cli_ctx(cli_ctx, svc_ctx);
        if (rc) {
                CERROR("failed copy reverse cli ctx: %d\n", rc);

                ctx_put_kr(cli_ctx, 1);
                return rc;
        }

        rvs_sec_install_root_ctx_kr(sec, cli_ctx, NULL);

        ctx_put_kr(cli_ctx, 1);

        return 0;
}


/****************************************
 * service apis                  *
 ****************************************/

static
int gss_svc_accept_kr(struct ptlrpc_request *req)
{
        return gss_svc_accept(&gss_policy_keyring, req);
}

static
int gss_svc_install_rctx_kr(struct obd_import *imp,
                            struct ptlrpc_svc_ctx *svc_ctx)
{
        struct ptlrpc_sec *sec;
        int             rc;

        sec = sptlrpc_import_sec_ref(imp);
        LASSERT(sec);

        rc = sec_install_rctx_kr(sec, svc_ctx);
        sptlrpc_sec_put(sec);

        return rc;
}

/****************************************
 * key apis                          *
 ****************************************/

static
int gss_kt_instantiate(struct key *key, const void *data, size_t datalen)
{
        int          rc;

        if (data != NULL || datalen != 0) {
                CERROR("invalid: data %p, len %lu\n", data, (long)datalen);
                return -EINVAL;
        }

        if (key->payload.data != 0) {
                CERROR("key already have payload\n");
                return -EINVAL;
        }

        /* link the key to session keyring, so following context negotiation
         * rpc fired from user space could find this key. This will be unlinked
         * automatically when upcall processes die.
         *
         * we can't do this through keyctl from userspace, because the upcall
         * might be neither possessor nor owner of the key (setuid).
         *
         * the session keyring is created upon upcall, and don't change all
         * the way until upcall finished, so rcu lock is not needed here.
         */
        LASSERT(key_tgcred(current)->session_keyring);

        lockdep_off();
        rc = key_link(key_tgcred(current)->session_keyring, key);
        lockdep_on();
        if (unlikely(rc)) {
                CERROR("failed to link key %08x to keyring %08x: %d\n",
                       key->serial,
                       key_tgcred(current)->session_keyring->serial, rc);
                return rc;
        }

        CDEBUG(D_SEC, "key %p instantiated, ctx %p\n", key, key->payload.data);
        return 0;
}

/*
 * called with key semaphore write locked. it means we can operate
 * on the context without fear of loosing refcount.
 */
static
int gss_kt_update(struct key *key, const void *data, size_t datalen)
{
        struct ptlrpc_cli_ctx   *ctx = key->payload.data;
        struct gss_cli_ctx      *gctx;
        rawobj_t                 tmpobj = RAWOBJ_EMPTY;
        __u32               datalen32 = (__u32) datalen;
        int                   rc;

        if (data == NULL || datalen == 0) {
                CWARN("invalid: data %p, len %lu\n", data, (long)datalen);
                return -EINVAL;
        }

        /* if upcall finished negotiation too fast (mostly likely because
         * of local error happened) and call kt_update(), the ctx
         * might be still NULL. but the key will finally be associate
         * with a context, or be revoked. if key status is fine, return
         * -EAGAIN to allow userspace sleep a while and call again. */
        if (ctx == NULL) {
                CDEBUG(D_SEC, "update too soon: key %p(%x) flags %lx\n",
                      key, key->serial, key->flags);

                rc = key_validate(key);
                if (rc == 0)
                        return -EAGAIN;
                else
                        return rc;
        }

        LASSERT(atomic_read(&ctx->cc_refcount) > 0);
        LASSERT(ctx->cc_sec);

        ctx_clear_timer_kr(ctx);

        /* don't proceed if already refreshed */
        if (cli_ctx_is_refreshed(ctx)) {
                CWARN("ctx already done refresh\n");
                return 0;
        }

        sptlrpc_cli_ctx_get(ctx);
        gctx = ctx2gctx(ctx);

        rc = buffer_extract_bytes(&data, &datalen32, &gctx->gc_win,
                                  sizeof(gctx->gc_win));
        if (rc) {
                CERROR("failed extract seq_win\n");
                goto out;
        }

        if (gctx->gc_win == 0) {
                __u32   nego_rpc_err, nego_gss_err;

                rc = buffer_extract_bytes(&data, &datalen32, &nego_rpc_err,
                                          sizeof(nego_rpc_err));
                if (rc) {
                        CERROR("failed to extrace rpc rc\n");
                        goto out;
                }

                rc = buffer_extract_bytes(&data, &datalen32, &nego_gss_err,
                                          sizeof(nego_gss_err));
                if (rc) {
                        CERROR("failed to extrace gss rc\n");
                        goto out;
                }

                CERROR("negotiation: rpc err %d, gss err %x\n",
                       nego_rpc_err, nego_gss_err);

                rc = nego_rpc_err ? nego_rpc_err : -EACCES;
        } else {
                rc = rawobj_extract_local_alloc(&gctx->gc_handle,
                                                (__u32 **) &data, &datalen32);
                if (rc) {
                        CERROR("failed extract handle\n");
                        goto out;
                }

                rc = rawobj_extract_local(&tmpobj, (__u32 **) &data,&datalen32);
                if (rc) {
                        CERROR("failed extract mech\n");
                        goto out;
                }

                rc = lgss_import_sec_context(&tmpobj,
                                             sec2gsec(ctx->cc_sec)->gs_mech,
                                             &gctx->gc_mechctx);
                if (rc != GSS_S_COMPLETE)
                        CERROR("failed import context\n");
                else
                        rc = 0;
        }
out:
        /* we don't care what current status of this ctx, even someone else
         * is operating on the ctx at the same time. we just add up our own
         * opinions here. */
        if (rc == 0) {
                gss_cli_ctx_uptodate(gctx);
        } else {
                /* this will also revoke the key. has to be done before
                 * wakeup waiters otherwise they can find the stale key */
                kill_key_locked(key);

                cli_ctx_expire(ctx);

                if (rc != -ERESTART)
                        set_bit(PTLRPC_CTX_ERROR_BIT, &ctx->cc_flags);
        }

        /* let user space think it's a success */
        sptlrpc_cli_ctx_put(ctx, 1);
        return 0;
}

static
int gss_kt_match(const struct key *key, const void *desc)
{
        return (strcmp(key->description, (const char *) desc) == 0);
}

static
void gss_kt_destroy(struct key *key)
{
        LASSERT(key->payload.data == NULL);
        CDEBUG(D_SEC, "destroy key %p\n", key);
}

static
void gss_kt_describe(const struct key *key, struct seq_file *s)
{
        if (key->description == NULL)
                seq_puts(s, "[null]");
        else
                seq_puts(s, key->description);
}

static struct key_type gss_key_type =
{
        .name      = "lgssc",
        .def_datalen    = 0,
        .instantiate    = gss_kt_instantiate,
        .update  = gss_kt_update,
        .match    = gss_kt_match,
        .destroy        = gss_kt_destroy,
        .describe       = gss_kt_describe,
};

/****************************************
 * lustre gss keyring policy        *
 ****************************************/

static struct ptlrpc_ctx_ops gss_keyring_ctxops = {
        .match            = gss_cli_ctx_match,
        .refresh                = gss_cli_ctx_refresh_kr,
        .validate              = gss_cli_ctx_validate_kr,
        .die                = gss_cli_ctx_die_kr,
        .sign              = gss_cli_ctx_sign,
        .verify          = gss_cli_ctx_verify,
        .seal              = gss_cli_ctx_seal,
        .unseal          = gss_cli_ctx_unseal,
        .wrap_bulk            = gss_cli_ctx_wrap_bulk,
        .unwrap_bulk        = gss_cli_ctx_unwrap_bulk,
};

static struct ptlrpc_sec_cops gss_sec_keyring_cops = {
        .create_sec          = gss_sec_create_kr,
        .destroy_sec        = gss_sec_destroy_kr,
        .kill_sec              = gss_sec_kill,
        .lookup_ctx          = gss_sec_lookup_ctx_kr,
        .release_ctx        = gss_sec_release_ctx_kr,
        .flush_ctx_cache        = gss_sec_flush_ctx_cache_kr,
        .gc_ctx          = gss_sec_gc_ctx_kr,
        .install_rctx      = gss_sec_install_rctx,
        .alloc_reqbuf      = gss_alloc_reqbuf,
        .free_reqbuf        = gss_free_reqbuf,
        .alloc_repbuf      = gss_alloc_repbuf,
        .free_repbuf        = gss_free_repbuf,
        .enlarge_reqbuf  = gss_enlarge_reqbuf,
        .display                = gss_sec_display_kr,
};

static struct ptlrpc_sec_sops gss_sec_keyring_sops = {
        .accept          = gss_svc_accept_kr,
        .invalidate_ctx  = gss_svc_invalidate_ctx,
        .alloc_rs              = gss_svc_alloc_rs,
        .authorize            = gss_svc_authorize,
        .free_rs                = gss_svc_free_rs,
        .free_ctx              = gss_svc_free_ctx,
        .prep_bulk            = gss_svc_prep_bulk,
        .unwrap_bulk        = gss_svc_unwrap_bulk,
        .wrap_bulk            = gss_svc_wrap_bulk,
        .install_rctx      = gss_svc_install_rctx_kr,
};

static struct ptlrpc_sec_policy gss_policy_keyring = {
        .sp_owner              = THIS_MODULE,
        .sp_name                = "gss.keyring",
        .sp_policy            = SPTLRPC_POLICY_GSS,
        .sp_cops                = &gss_sec_keyring_cops,
        .sp_sops                = &gss_sec_keyring_sops,
};


int __init gss_init_keyring(void)
{
        int rc;

        rc = register_key_type(&gss_key_type);
        if (rc) {
                CERROR("failed to register keyring type: %d\n", rc);
                return rc;
        }

        rc = sptlrpc_register_policy(&gss_policy_keyring);
        if (rc) {
                unregister_key_type(&gss_key_type);
                return rc;
        }

        return 0;
}

void __exit gss_exit_keyring(void)
{
        unregister_key_type(&gss_key_type);
        sptlrpc_unregister_policy(&gss_policy_keyring);
}