/*
 * linux/net/sunrpc/auth_gss/auth_gss.c
 *
 * RPCSEC_GSS client authentication.
 *
 *  Copyright (c) 2000 The Regents of the University of Michigan.
 *  All rights reserved.
 *
 *  Dug Song       <dugsong@monkey.org>
 *  Andy Adamson   <andros@umich.edu>
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *  3. Neither the name of the University nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 *  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 *  DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 *  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 *  BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/pagemap.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/auth.h>
#include <linux/sunrpc/auth_gss.h>
#include <linux/sunrpc/svcauth_gss.h>
#include <linux/sunrpc/gss_err.h>
#include <linux/workqueue.h>
#include <linux/sunrpc/rpc_pipe_fs.h>
#include <linux/sunrpc/gss_api.h>
#include <linux/uaccess.h>
#include <linux/hashtable.h>

#include "../netns.h"

static const struct rpc_authops authgss_ops;

static const struct rpc_credops gss_credops;
static const struct rpc_credops gss_nullops;

#define GSS_RETRY_EXPIRED 5
static unsigned int gss_expired_cred_retry_delay = GSS_RETRY_EXPIRED;

#define GSS_KEY_EXPIRE_TIMEO 240
static unsigned int gss_key_expire_timeo = GSS_KEY_EXPIRE_TIMEO;

#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
# define RPCDBG_FACILITY        RPCDBG_AUTH
#endif

#define GSS_CRED_SLACK          (RPC_MAX_AUTH_SIZE * 2)
/* length of a krb5 verifier (48), plus data added before arguments when
 * using integrity (two 4-byte integers): */
#define GSS_VERF_SLACK          100

static DEFINE_HASHTABLE(gss_auth_hash_table, 4);
static DEFINE_SPINLOCK(gss_auth_hash_lock);

struct gss_pipe {
        struct rpc_pipe_dir_object pdo;
        struct rpc_pipe *pipe;
        struct rpc_clnt *clnt;
        const char *name;
        struct kref kref;
};

struct gss_auth {
        struct kref kref;
        struct hlist_node hash;
        struct rpc_auth rpc_auth;
        struct gss_api_mech *mech;
        enum rpc_gss_svc service;
        struct rpc_clnt *client;
        struct net *net;
        /*
         * There are two upcall pipes; dentry[1], named "gssd", is used
         * for the new text-based upcall; dentry[0] is named after the
         * mechanism (for example, "krb5") and exists for
         * backwards-compatibility with older gssd's.
         */
        struct gss_pipe *gss_pipe[2];
        const char *target_name;
};

/* pipe_version >= 0 if and only if someone has a pipe open. */
static DEFINE_SPINLOCK(pipe_version_lock);
static struct rpc_wait_queue pipe_version_rpc_waitqueue;
static DECLARE_WAIT_QUEUE_HEAD(pipe_version_waitqueue);
static void gss_put_auth(struct gss_auth *gss_auth);

static void gss_free_ctx(struct gss_cl_ctx *);
static const struct rpc_pipe_ops gss_upcall_ops_v0;
static const struct rpc_pipe_ops gss_upcall_ops_v1;

static inline struct gss_cl_ctx *
gss_get_ctx(struct gss_cl_ctx *ctx)
{
        refcount_inc(&ctx->count);
        return ctx;
}

static inline void
gss_put_ctx(struct gss_cl_ctx *ctx)
{
        if (refcount_dec_and_test(&ctx->count))
                gss_free_ctx(ctx);
}

/* gss_cred_set_ctx:
 * called by gss_upcall_callback and gss_create_upcall in order
 * to set the gss context. The actual exchange of an old context
 * and a new one is protected by the pipe->lock.
 */
static void
gss_cred_set_ctx(struct rpc_cred *cred, struct gss_cl_ctx *ctx)
{
        struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);

        if (!test_bit(RPCAUTH_CRED_NEW, &cred->cr_flags))
                return;
        gss_get_ctx(ctx);
        rcu_assign_pointer(gss_cred->gc_ctx, ctx);
        set_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
        smp_mb__before_atomic();
        clear_bit(RPCAUTH_CRED_NEW, &cred->cr_flags);
}

static const void *
simple_get_bytes(const void *p, const void *end, void *res, size_t len)
{
        const void *q = (const void *)((const char *)p + len);
        if (unlikely(q > end || q < p))
                return ERR_PTR(-EFAULT);
        memcpy(res, p, len);
        return q;
}

static inline const void *
simple_get_netobj(const void *p, const void *end, struct xdr_netobj *dest)
{
        const void *q;
        unsigned int len;

        p = simple_get_bytes(p, end, &len, sizeof(len));
        if (IS_ERR(p))
                return p;
        q = (const void *)((const char *)p + len);
        if (unlikely(q > end || q < p))
                return ERR_PTR(-EFAULT);
        dest->data = kmemdup(p, len, GFP_NOFS);
        if (unlikely(dest->data == NULL))
                return ERR_PTR(-ENOMEM);
        dest->len = len;
        return q;
}

static struct gss_cl_ctx *
gss_cred_get_ctx(struct rpc_cred *cred)
{
        struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
        struct gss_cl_ctx *ctx = NULL;

        rcu_read_lock();
        ctx = rcu_dereference(gss_cred->gc_ctx);
        if (ctx)
                gss_get_ctx(ctx);
        rcu_read_unlock();
        return ctx;
}

static struct gss_cl_ctx *
gss_alloc_context(void)
{
        struct gss_cl_ctx *ctx;

        ctx = kzalloc(sizeof(*ctx), GFP_NOFS);
        if (ctx != NULL) {
                ctx->gc_proc = RPC_GSS_PROC_DATA;
                ctx->gc_seq = 1;        /* NetApp 6.4R1 doesn't accept seq. no. 0 */
                spin_lock_init(&ctx->gc_seq_lock);
                refcount_set(&ctx->count,1);
        }
        return ctx;
}

#define GSSD_MIN_TIMEOUT (60 * 60)
static const void *
gss_fill_context(const void *p, const void *end, struct gss_cl_ctx *ctx, struct gss_api_mech *gm)
{
        const void *q;
        unsigned int seclen;
        unsigned int timeout;
        unsigned long now = jiffies;
        u32 window_size;
        int ret;

        /* First unsigned int gives the remaining lifetime in seconds of the
         * credential - e.g. the remaining TGT lifetime for Kerberos or
         * the -t value passed to GSSD.
         */
        p = simple_get_bytes(p, end, &timeout, sizeof(timeout));
        if (IS_ERR(p))
                goto err;
        if (timeout == 0)
                timeout = GSSD_MIN_TIMEOUT;
        ctx->gc_expiry = now + ((unsigned long)timeout * HZ);
        /* Sequence number window. Determines the maximum number of
         * simultaneous requests
         */
        p = simple_get_bytes(p, end, &window_size, sizeof(window_size));
        if (IS_ERR(p))
                goto err;
        ctx->gc_win = window_size;
        /* gssd signals an error by passing ctx->gc_win = 0: */
        if (ctx->gc_win == 0) {
                /*
                 * in which case, p points to an error code. Anything other
                 * than -EKEYEXPIRED gets converted to -EACCES.
                 */
                p = simple_get_bytes(p, end, &ret, sizeof(ret));
                if (!IS_ERR(p))
                        p = (ret == -EKEYEXPIRED) ? ERR_PTR(-EKEYEXPIRED) :
                                                    ERR_PTR(-EACCES);
                goto err;
        }
        /* copy the opaque wire context */
        p = simple_get_netobj(p, end, &ctx->gc_wire_ctx);
        if (IS_ERR(p))
                goto err;
        /* import the opaque security context */
        p  = simple_get_bytes(p, end, &seclen, sizeof(seclen));
        if (IS_ERR(p))
                goto err;
        q = (const void *)((const char *)p + seclen);
        if (unlikely(q > end || q < p)) {
                p = ERR_PTR(-EFAULT);
                goto err;
        }
        ret = gss_import_sec_context(p, seclen, gm, &ctx->gc_gss_ctx, NULL, GFP_NOFS);
        if (ret < 0) {
                p = ERR_PTR(ret);
                goto err;
        }

        /* is there any trailing data? */
        if (q == end) {
                p = q;
                goto done;
        }

        /* pull in acceptor name (if there is one) */
        p = simple_get_netobj(q, end, &ctx->gc_acceptor);
        if (IS_ERR(p))
                goto err;
done:
        dprintk("RPC:       %s Success. gc_expiry %lu now %lu timeout %u acceptor %.*s\n",
                __func__, ctx->gc_expiry, now, timeout, ctx->gc_acceptor.len,
                ctx->gc_acceptor.data);
        return p;
err:
        dprintk("RPC:       %s returns error %ld\n", __func__, -PTR_ERR(p));
        return p;
}

#define UPCALL_BUF_LEN 128

struct gss_upcall_msg {
        refcount_t count;
        kuid_t  uid;
        struct rpc_pipe_msg msg;
        struct list_head list;
        struct gss_auth *auth;
        struct rpc_pipe *pipe;
        struct rpc_wait_queue rpc_waitqueue;
        wait_queue_head_t waitqueue;
        struct gss_cl_ctx *ctx;
        char databuf[UPCALL_BUF_LEN];
};

static int get_pipe_version(struct net *net)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        int ret;

        spin_lock(&pipe_version_lock);
        if (sn->pipe_version >= 0) {
                atomic_inc(&sn->pipe_users);
                ret = sn->pipe_version;
        } else
                ret = -EAGAIN;
        spin_unlock(&pipe_version_lock);
        return ret;
}

static void put_pipe_version(struct net *net)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);

        if (atomic_dec_and_lock(&sn->pipe_users, &pipe_version_lock)) {
                sn->pipe_version = -1;
                spin_unlock(&pipe_version_lock);
        }
}

static void
gss_release_msg(struct gss_upcall_msg *gss_msg)
{
        struct net *net = gss_msg->auth->net;
        if (!refcount_dec_and_test(&gss_msg->count))
                return;
        put_pipe_version(net);
        BUG_ON(!list_empty(&gss_msg->list));
        if (gss_msg->ctx != NULL)
                gss_put_ctx(gss_msg->ctx);
        rpc_destroy_wait_queue(&gss_msg->rpc_waitqueue);
        gss_put_auth(gss_msg->auth);
        kfree(gss_msg);
}

static struct gss_upcall_msg *
__gss_find_upcall(struct rpc_pipe *pipe, kuid_t uid, const struct gss_auth *auth)
{
        struct gss_upcall_msg *pos;
        list_for_each_entry(pos, &pipe->in_downcall, list) {
                if (!uid_eq(pos->uid, uid))
                        continue;
                if (auth && pos->auth->service != auth->service)
                        continue;
                refcount_inc(&pos->count);
                dprintk("RPC:       %s found msg %p\n", __func__, pos);
                return pos;
        }
        dprintk("RPC:       %s found nothing\n", __func__);
        return NULL;
}

/* Try to add an upcall to the pipefs queue.
 * If an upcall owned by our uid already exists, then we return a reference
 * to that upcall instead of adding the new upcall.
 */
static inline struct gss_upcall_msg *
gss_add_msg(struct gss_upcall_msg *gss_msg)
{
        struct rpc_pipe *pipe = gss_msg->pipe;
        struct gss_upcall_msg *old;

        spin_lock(&pipe->lock);
        old = __gss_find_upcall(pipe, gss_msg->uid, gss_msg->auth);
        if (old == NULL) {
                refcount_inc(&gss_msg->count);
                list_add(&gss_msg->list, &pipe->in_downcall);
        } else
                gss_msg = old;
        spin_unlock(&pipe->lock);
        return gss_msg;
}

static void
__gss_unhash_msg(struct gss_upcall_msg *gss_msg)
{
        list_del_init(&gss_msg->list);
        rpc_wake_up_status(&gss_msg->rpc_waitqueue, gss_msg->msg.errno);
        wake_up_all(&gss_msg->waitqueue);
        refcount_dec(&gss_msg->count);
}

static void
gss_unhash_msg(struct gss_upcall_msg *gss_msg)
{
        struct rpc_pipe *pipe = gss_msg->pipe;

        if (list_empty(&gss_msg->list))
                return;
        spin_lock(&pipe->lock);
        if (!list_empty(&gss_msg->list))
                __gss_unhash_msg(gss_msg);
        spin_unlock(&pipe->lock);
}

static void
gss_handle_downcall_result(struct gss_cred *gss_cred, struct gss_upcall_msg *gss_msg)
{
        switch (gss_msg->msg.errno) {
        case 0:
                if (gss_msg->ctx == NULL)
                        break;
                clear_bit(RPCAUTH_CRED_NEGATIVE, &gss_cred->gc_base.cr_flags);
                gss_cred_set_ctx(&gss_cred->gc_base, gss_msg->ctx);
                break;
        case -EKEYEXPIRED:
                set_bit(RPCAUTH_CRED_NEGATIVE, &gss_cred->gc_base.cr_flags);
        }
        gss_cred->gc_upcall_timestamp = jiffies;
        gss_cred->gc_upcall = NULL;
        rpc_wake_up_status(&gss_msg->rpc_waitqueue, gss_msg->msg.errno);
}

static void
gss_upcall_callback(struct rpc_task *task)
{
        struct gss_cred *gss_cred = container_of(task->tk_rqstp->rq_cred,
                        struct gss_cred, gc_base);
        struct gss_upcall_msg *gss_msg = gss_cred->gc_upcall;
        struct rpc_pipe *pipe = gss_msg->pipe;

        spin_lock(&pipe->lock);
        gss_handle_downcall_result(gss_cred, gss_msg);
        spin_unlock(&pipe->lock);
        task->tk_status = gss_msg->msg.errno;
        gss_release_msg(gss_msg);
}

static void gss_encode_v0_msg(struct gss_upcall_msg *gss_msg)
{
        uid_t uid = from_kuid(&init_user_ns, gss_msg->uid);
        memcpy(gss_msg->databuf, &uid, sizeof(uid));
        gss_msg->msg.data = gss_msg->databuf;
        gss_msg->msg.len = sizeof(uid);

        BUILD_BUG_ON(sizeof(uid) > sizeof(gss_msg->databuf));
}

static int gss_encode_v1_msg(struct gss_upcall_msg *gss_msg,
                                const char *service_name,
                                const char *target_name)
{
        struct gss_api_mech *mech = gss_msg->auth->mech;
        char *p = gss_msg->databuf;
        size_t buflen = sizeof(gss_msg->databuf);
        int len;

        len = scnprintf(p, buflen, "mech=%s uid=%d ", mech->gm_name,
                        from_kuid(&init_user_ns, gss_msg->uid));
        buflen -= len;
        p += len;
        gss_msg->msg.len = len;
        if (target_name) {
                len = scnprintf(p, buflen, "target=%s ", target_name);
                buflen -= len;
                p += len;
                gss_msg->msg.len += len;
        }
        if (service_name != NULL) {
                len = scnprintf(p, buflen, "service=%s ", service_name);
                buflen -= len;
                p += len;
                gss_msg->msg.len += len;
        }
        if (mech->gm_upcall_enctypes) {
                len = scnprintf(p, buflen, "enctypes=%s ",
                                mech->gm_upcall_enctypes);
                buflen -= len;
                p += len;
                gss_msg->msg.len += len;
        }
        len = scnprintf(p, buflen, "\n");
        if (len == 0)
                goto out_overflow;
        gss_msg->msg.len += len;

        gss_msg->msg.data = gss_msg->databuf;
        return 0;
out_overflow:
        WARN_ON_ONCE(1);
        return -ENOMEM;
}

static struct gss_upcall_msg *
gss_alloc_msg(struct gss_auth *gss_auth,
                kuid_t uid, const char *service_name)
{
        struct gss_upcall_msg *gss_msg;
        int vers;
        int err = -ENOMEM;

        gss_msg = kzalloc(sizeof(*gss_msg), GFP_NOFS);
        if (gss_msg == NULL)
                goto err;
        vers = get_pipe_version(gss_auth->net);
        err = vers;
        if (err < 0)
                goto err_free_msg;
        gss_msg->pipe = gss_auth->gss_pipe[vers]->pipe;
        INIT_LIST_HEAD(&gss_msg->list);
        rpc_init_wait_queue(&gss_msg->rpc_waitqueue, "RPCSEC_GSS upcall waitq");
        init_waitqueue_head(&gss_msg->waitqueue);
        refcount_set(&gss_msg->count, 1);
        gss_msg->uid = uid;
        gss_msg->auth = gss_auth;
        switch (vers) {
        case 0:
                gss_encode_v0_msg(gss_msg);
                break;
        default:
                err = gss_encode_v1_msg(gss_msg, service_name, gss_auth->target_name);
                if (err)
                        goto err_put_pipe_version;
        };
        kref_get(&gss_auth->kref);
        return gss_msg;
err_put_pipe_version:
        put_pipe_version(gss_auth->net);
err_free_msg:
        kfree(gss_msg);
err:
        return ERR_PTR(err);
}

static struct gss_upcall_msg *
gss_setup_upcall(struct gss_auth *gss_auth, struct rpc_cred *cred)
{
        struct gss_cred *gss_cred = container_of(cred,
                        struct gss_cred, gc_base);
        struct gss_upcall_msg *gss_new, *gss_msg;
        kuid_t uid = cred->cr_uid;

        gss_new = gss_alloc_msg(gss_auth, uid, gss_cred->gc_principal);
        if (IS_ERR(gss_new))
                return gss_new;
        gss_msg = gss_add_msg(gss_new);
        if (gss_msg == gss_new) {
                int res;
                refcount_inc(&gss_msg->count);
                res = rpc_queue_upcall(gss_new->pipe, &gss_new->msg);
                if (res) {
                        gss_unhash_msg(gss_new);
                        refcount_dec(&gss_msg->count);
                        gss_release_msg(gss_new);
                        gss_msg = ERR_PTR(res);
                }
        } else
                gss_release_msg(gss_new);
        return gss_msg;
}

static void warn_gssd(void)
{
        dprintk("AUTH_GSS upcall failed. Please check user daemon is running.\n");
}

static inline int
gss_refresh_upcall(struct rpc_task *task)
{
        struct rpc_cred *cred = task->tk_rqstp->rq_cred;
        struct gss_auth *gss_auth = container_of(cred->cr_auth,
                        struct gss_auth, rpc_auth);
        struct gss_cred *gss_cred = container_of(cred,
                        struct gss_cred, gc_base);
        struct gss_upcall_msg *gss_msg;
        struct rpc_pipe *pipe;
        int err = 0;

        dprintk("RPC: %5u %s for uid %u\n",
                task->tk_pid, __func__, from_kuid(&init_user_ns, cred->cr_uid));
        gss_msg = gss_setup_upcall(gss_auth, cred);
        if (PTR_ERR(gss_msg) == -EAGAIN) {
                /* XXX: warning on the first, under the assumption we
                 * shouldn't normally hit this case on a refresh. */
                warn_gssd();
                task->tk_timeout = 15*HZ;
                rpc_sleep_on(&pipe_version_rpc_waitqueue, task, NULL);
                return -EAGAIN;
        }
        if (IS_ERR(gss_msg)) {
                err = PTR_ERR(gss_msg);
                goto out;
        }
        pipe = gss_msg->pipe;
        spin_lock(&pipe->lock);
        if (gss_cred->gc_upcall != NULL)
                rpc_sleep_on(&gss_cred->gc_upcall->rpc_waitqueue, task, NULL);
        else if (gss_msg->ctx == NULL && gss_msg->msg.errno >= 0) {
                task->tk_timeout = 0;
                gss_cred->gc_upcall = gss_msg;
                /* gss_upcall_callback will release the reference to gss_upcall_msg */
                refcount_inc(&gss_msg->count);
                rpc_sleep_on(&gss_msg->rpc_waitqueue, task, gss_upcall_callback);
        } else {
                gss_handle_downcall_result(gss_cred, gss_msg);
                err = gss_msg->msg.errno;
        }
        spin_unlock(&pipe->lock);
        gss_release_msg(gss_msg);
out:
        dprintk("RPC: %5u %s for uid %u result %d\n",
                task->tk_pid, __func__,
                from_kuid(&init_user_ns, cred->cr_uid), err);
        return err;
}

static inline int
gss_create_upcall(struct gss_auth *gss_auth, struct gss_cred *gss_cred)
{
        struct net *net = gss_auth->net;
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        struct rpc_pipe *pipe;
        struct rpc_cred *cred = &gss_cred->gc_base;
        struct gss_upcall_msg *gss_msg;
        DEFINE_WAIT(wait);
        int err;

        dprintk("RPC:       %s for uid %u\n",
                __func__, from_kuid(&init_user_ns, cred->cr_uid));
retry:
        err = 0;
        /* if gssd is down, just skip upcalling altogether */
        if (!gssd_running(net)) {
                warn_gssd();
                return -EACCES;
        }
        gss_msg = gss_setup_upcall(gss_auth, cred);
        if (PTR_ERR(gss_msg) == -EAGAIN) {
                err = wait_event_interruptible_timeout(pipe_version_waitqueue,
                                sn->pipe_version >= 0, 15 * HZ);
                if (sn->pipe_version < 0) {
                        warn_gssd();
                        err = -EACCES;
                }
                if (err < 0)
                        goto out;
                goto retry;
        }
        if (IS_ERR(gss_msg)) {
                err = PTR_ERR(gss_msg);
                goto out;
        }
        pipe = gss_msg->pipe;
        for (;;) {
                prepare_to_wait(&gss_msg->waitqueue, &wait, TASK_KILLABLE);
                spin_lock(&pipe->lock);
                if (gss_msg->ctx != NULL || gss_msg->msg.errno < 0) {
                        break;
                }
                spin_unlock(&pipe->lock);
                if (fatal_signal_pending(current)) {
                        err = -ERESTARTSYS;
                        goto out_intr;
                }
                schedule();
        }
        if (gss_msg->ctx)
                gss_cred_set_ctx(cred, gss_msg->ctx);
        else
                err = gss_msg->msg.errno;
        spin_unlock(&pipe->lock);
out_intr:
        finish_wait(&gss_msg->waitqueue, &wait);
        gss_release_msg(gss_msg);
out:
        dprintk("RPC:       %s for uid %u result %d\n",
                __func__, from_kuid(&init_user_ns, cred->cr_uid), err);
        return err;
}

#define MSG_BUF_MAXSIZE 1024

static ssize_t
gss_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
{
        const void *p, *end;
        void *buf;
        struct gss_upcall_msg *gss_msg;
        struct rpc_pipe *pipe = RPC_I(file_inode(filp))->pipe;
        struct gss_cl_ctx *ctx;
        uid_t id;
        kuid_t uid;
        ssize_t err = -EFBIG;

        if (mlen > MSG_BUF_MAXSIZE)
                goto out;
        err = -ENOMEM;
        buf = kmalloc(mlen, GFP_NOFS);
        if (!buf)
                goto out;

        err = -EFAULT;
        if (copy_from_user(buf, src, mlen))
                goto err;

        end = (const void *)((char *)buf + mlen);
        p = simple_get_bytes(buf, end, &id, sizeof(id));
        if (IS_ERR(p)) {
                err = PTR_ERR(p);
                goto err;
        }

        uid = make_kuid(&init_user_ns, id);
        if (!uid_valid(uid)) {
                err = -EINVAL;
                goto err;
        }

        err = -ENOMEM;
        ctx = gss_alloc_context();
        if (ctx == NULL)
                goto err;

        err = -ENOENT;
        /* Find a matching upcall */
        spin_lock(&pipe->lock);
        gss_msg = __gss_find_upcall(pipe, uid, NULL);
        if (gss_msg == NULL) {
                spin_unlock(&pipe->lock);
                goto err_put_ctx;
        }
        list_del_init(&gss_msg->list);
        spin_unlock(&pipe->lock);

        p = gss_fill_context(p, end, ctx, gss_msg->auth->mech);
        if (IS_ERR(p)) {
                err = PTR_ERR(p);
                switch (err) {
                case -EACCES:
                case -EKEYEXPIRED:
                        gss_msg->msg.errno = err;
                        err = mlen;
                        break;
                case -EFAULT:
                case -ENOMEM:
                case -EINVAL:
                case -ENOSYS:
                        gss_msg->msg.errno = -EAGAIN;
                        break;
                default:
                        printk(KERN_CRIT "%s: bad return from "
                                "gss_fill_context: %zd\n", __func__, err);
                        gss_msg->msg.errno = -EIO;
                }
                goto err_release_msg;
        }
        gss_msg->ctx = gss_get_ctx(ctx);
        err = mlen;

err_release_msg:
        spin_lock(&pipe->lock);
        __gss_unhash_msg(gss_msg);
        spin_unlock(&pipe->lock);
        gss_release_msg(gss_msg);
err_put_ctx:
        gss_put_ctx(ctx);
err:
        kfree(buf);
out:
        dprintk("RPC:       %s returning %zd\n", __func__, err);
        return err;
}

static int gss_pipe_open(struct inode *inode, int new_version)
{
        struct net *net = inode->i_sb->s_fs_info;
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        int ret = 0;

        spin_lock(&pipe_version_lock);
        if (sn->pipe_version < 0) {
                /* First open of any gss pipe determines the version: */
                sn->pipe_version = new_version;
                rpc_wake_up(&pipe_version_rpc_waitqueue);
                wake_up(&pipe_version_waitqueue);
        } else if (sn->pipe_version != new_version) {
                /* Trying to open a pipe of a different version */
                ret = -EBUSY;
                goto out;
        }
        atomic_inc(&sn->pipe_users);
out:
        spin_unlock(&pipe_version_lock);
        return ret;

}

static int gss_pipe_open_v0(struct inode *inode)
{
        return gss_pipe_open(inode, 0);
}

static int gss_pipe_open_v1(struct inode *inode)
{
        return gss_pipe_open(inode, 1);
}

static void
gss_pipe_release(struct inode *inode)
{
        struct net *net = inode->i_sb->s_fs_info;
        struct rpc_pipe *pipe = RPC_I(inode)->pipe;
        struct gss_upcall_msg *gss_msg;

restart:
        spin_lock(&pipe->lock);
        list_for_each_entry(gss_msg, &pipe->in_downcall, list) {

                if (!list_empty(&gss_msg->msg.list))
                        continue;
                gss_msg->msg.errno = -EPIPE;
                refcount_inc(&gss_msg->count);
                __gss_unhash_msg(gss_msg);
                spin_unlock(&pipe->lock);
                gss_release_msg(gss_msg);
                goto restart;
        }
        spin_unlock(&pipe->lock);

        put_pipe_version(net);
}

static void
gss_pipe_destroy_msg(struct rpc_pipe_msg *msg)
{
        struct gss_upcall_msg *gss_msg = container_of(msg, struct gss_upcall_msg, msg);

        if (msg->errno < 0) {
                dprintk("RPC:       %s releasing msg %p\n",
                        __func__, gss_msg);
                refcount_inc(&gss_msg->count);
                gss_unhash_msg(gss_msg);
                if (msg->errno == -ETIMEDOUT)
                        warn_gssd();
                gss_release_msg(gss_msg);
        }
        gss_release_msg(gss_msg);
}

static void gss_pipe_dentry_destroy(struct dentry *dir,
                struct rpc_pipe_dir_object *pdo)
{
        struct gss_pipe *gss_pipe = pdo->pdo_data;
        struct rpc_pipe *pipe = gss_pipe->pipe;

        if (pipe->dentry != NULL) {
                rpc_unlink(pipe->dentry);
                pipe->dentry = NULL;
        }
}

static int gss_pipe_dentry_create(struct dentry *dir,
                struct rpc_pipe_dir_object *pdo)
{
        struct gss_pipe *p = pdo->pdo_data;
        struct dentry *dentry;

        dentry = rpc_mkpipe_dentry(dir, p->name, p->clnt, p->pipe);
        if (IS_ERR(dentry))
                return PTR_ERR(dentry);
        p->pipe->dentry = dentry;
        return 0;
}

static const struct rpc_pipe_dir_object_ops gss_pipe_dir_object_ops = {
        .create = gss_pipe_dentry_create,
        .destroy = gss_pipe_dentry_destroy,
};

static struct gss_pipe *gss_pipe_alloc(struct rpc_clnt *clnt,
                const char *name,
                const struct rpc_pipe_ops *upcall_ops)
{
        struct gss_pipe *p;
        int err = -ENOMEM;

        p = kmalloc(sizeof(*p), GFP_KERNEL);
        if (p == NULL)
                goto err;
        p->pipe = rpc_mkpipe_data(upcall_ops, RPC_PIPE_WAIT_FOR_OPEN);
        if (IS_ERR(p->pipe)) {
                err = PTR_ERR(p->pipe);
                goto err_free_gss_pipe;
        }
        p->name = name;
        p->clnt = clnt;
        kref_init(&p->kref);
        rpc_init_pipe_dir_object(&p->pdo,
                        &gss_pipe_dir_object_ops,
                        p);
        return p;
err_free_gss_pipe:
        kfree(p);
err:
        return ERR_PTR(err);
}

struct gss_alloc_pdo {
        struct rpc_clnt *clnt;
        const char *name;
        const struct rpc_pipe_ops *upcall_ops;
};

static int gss_pipe_match_pdo(struct rpc_pipe_dir_object *pdo, void *data)
{
        struct gss_pipe *gss_pipe;
        struct gss_alloc_pdo *args = data;

        if (pdo->pdo_ops != &gss_pipe_dir_object_ops)
                return 0;
        gss_pipe = container_of(pdo, struct gss_pipe, pdo);
        if (strcmp(gss_pipe->name, args->name) != 0)
                return 0;
        if (!kref_get_unless_zero(&gss_pipe->kref))
                return 0;
        return 1;
}

static struct rpc_pipe_dir_object *gss_pipe_alloc_pdo(void *data)
{
        struct gss_pipe *gss_pipe;
        struct gss_alloc_pdo *args = data;

        gss_pipe = gss_pipe_alloc(args->clnt, args->name, args->upcall_ops);
        if (!IS_ERR(gss_pipe))
                return &gss_pipe->pdo;
        return NULL;
}

static struct gss_pipe *gss_pipe_get(struct rpc_clnt *clnt,
                const char *name,
                const struct rpc_pipe_ops *upcall_ops)
{
        struct net *net = rpc_net_ns(clnt);
        struct rpc_pipe_dir_object *pdo;
        struct gss_alloc_pdo args = {
                .clnt = clnt,
                .name = name,
                .upcall_ops = upcall_ops,
        };

        pdo = rpc_find_or_alloc_pipe_dir_object(net,
                        &clnt->cl_pipedir_objects,
                        gss_pipe_match_pdo,
                        gss_pipe_alloc_pdo,
                        &args);
        if (pdo != NULL)
                return container_of(pdo, struct gss_pipe, pdo);
        return ERR_PTR(-ENOMEM);
}

static void __gss_pipe_free(struct gss_pipe *p)
{
        struct rpc_clnt *clnt = p->clnt;
        struct net *net = rpc_net_ns(clnt);

        rpc_remove_pipe_dir_object(net,
                        &clnt->cl_pipedir_objects,
                        &p->pdo);
        rpc_destroy_pipe_data(p->pipe);
        kfree(p);
}

static void __gss_pipe_release(struct kref *kref)
{
        struct gss_pipe *p = container_of(kref, struct gss_pipe, kref);

        __gss_pipe_free(p);
}

static void gss_pipe_free(struct gss_pipe *p)
{
        if (p != NULL)
                kref_put(&p->kref, __gss_pipe_release);
}

/*
 * NOTE: we have the opportunity to use different
 * parameters based on the input flavor (which must be a pseudoflavor)
 */
static struct gss_auth *
gss_create_new(struct rpc_auth_create_args *args, struct rpc_clnt *clnt)
{
        rpc_authflavor_t flavor = args->pseudoflavor;
        struct gss_auth *gss_auth;
        struct gss_pipe *gss_pipe;
        struct rpc_auth * auth;
        int err = -ENOMEM; /* XXX? */

        dprintk("RPC:       creating GSS authenticator for client %p\n", clnt);

        if (!try_module_get(THIS_MODULE))
                return ERR_PTR(err);
        if (!(gss_auth = kmalloc(sizeof(*gss_auth), GFP_KERNEL)))

                goto out_dec;
        INIT_HLIST_NODE(&gss_auth->hash);
        gss_auth->target_name = NULL;
        if (args->target_name) {
                gss_auth->target_name = kstrdup(args->target_name, GFP_KERNEL);
                if (gss_auth->target_name == NULL)
                        goto err_free;
        }
        gss_auth->client = clnt;
        gss_auth->net = get_net(rpc_net_ns(clnt));
        err = -EINVAL;
        gss_auth->mech = gss_mech_get_by_pseudoflavor(flavor);
        if (!gss_auth->mech) {
                dprintk("RPC:       Pseudoflavor %d not found!\n", flavor);
                goto err_put_net;
        }
        gss_auth->service = gss_pseudoflavor_to_service(gss_auth->mech, flavor);
        if (gss_auth->service == 0)
                goto err_put_mech;
        if (!gssd_running(gss_auth->net))
                goto err_put_mech;
        auth = &gss_auth->rpc_auth;
        auth->au_cslack = GSS_CRED_SLACK >> 2;
        auth->au_rslack = GSS_VERF_SLACK >> 2;
        auth->au_flags = 0;
        auth->au_ops = &authgss_ops;
        auth->au_flavor = flavor;
        if (gss_pseudoflavor_to_datatouch(gss_auth->mech, flavor))
                auth->au_flags |= RPCAUTH_AUTH_DATATOUCH;
        atomic_set(&auth->au_count, 1);
        kref_init(&gss_auth->kref);

        err = rpcauth_init_credcache(auth);
        if (err)
                goto err_put_mech;
        /*
         * Note: if we created the old pipe first, then someone who
         * examined the directory at the right moment might conclude
         * that we supported only the old pipe.  So we instead create
         * the new pipe first.
         */
        gss_pipe = gss_pipe_get(clnt, "gssd", &gss_upcall_ops_v1);
        if (IS_ERR(gss_pipe)) {
                err = PTR_ERR(gss_pipe);
                goto err_destroy_credcache;
        }
        gss_auth->gss_pipe[1] = gss_pipe;

        gss_pipe = gss_pipe_get(clnt, gss_auth->mech->gm_name,
                        &gss_upcall_ops_v0);
        if (IS_ERR(gss_pipe)) {
                err = PTR_ERR(gss_pipe);
                goto err_destroy_pipe_1;
        }
        gss_auth->gss_pipe[0] = gss_pipe;

        return gss_auth;
err_destroy_pipe_1:
        gss_pipe_free(gss_auth->gss_pipe[1]);
err_destroy_credcache:
        rpcauth_destroy_credcache(auth);
err_put_mech:
        gss_mech_put(gss_auth->mech);
err_put_net:
        put_net(gss_auth->net);
err_free:
        kfree(gss_auth->target_name);
        kfree(gss_auth);
out_dec:
        module_put(THIS_MODULE);
        return ERR_PTR(err);
}

static void
gss_free(struct gss_auth *gss_auth)
{
        gss_pipe_free(gss_auth->gss_pipe[0]);
        gss_pipe_free(gss_auth->gss_pipe[1]);
        gss_mech_put(gss_auth->mech);
        put_net(gss_auth->net);
        kfree(gss_auth->target_name);

        kfree(gss_auth);
        module_put(THIS_MODULE);
}

static void
gss_free_callback(struct kref *kref)
{
        struct gss_auth *gss_auth = container_of(kref, struct gss_auth, kref);

        gss_free(gss_auth);
}

static void
gss_put_auth(struct gss_auth *gss_auth)
{
        kref_put(&gss_auth->kref, gss_free_callback);
}

static void
gss_destroy(struct rpc_auth *auth)
{
        struct gss_auth *gss_auth = container_of(auth,
                        struct gss_auth, rpc_auth);

        dprintk("RPC:       destroying GSS authenticator %p flavor %d\n",
                        auth, auth->au_flavor);

        if (hash_hashed(&gss_auth->hash)) {
                spin_lock(&gss_auth_hash_lock);
                hash_del(&gss_auth->hash);
                spin_unlock(&gss_auth_hash_lock);
        }

        gss_pipe_free(gss_auth->gss_pipe[0]);
        gss_auth->gss_pipe[0] = NULL;
        gss_pipe_free(gss_auth->gss_pipe[1]);
        gss_auth->gss_pipe[1] = NULL;
        rpcauth_destroy_credcache(auth);

        gss_put_auth(gss_auth);
}

/*
 * Auths may be shared between rpc clients that were cloned from a
 * common client with the same xprt, if they also share the flavor and
 * target_name.
 *
 * The auth is looked up from the oldest parent sharing the same
 * cl_xprt, and the auth itself references only that common parent
 * (which is guaranteed to last as long as any of its descendants).
 */
static struct gss_auth *
gss_auth_find_or_add_hashed(struct rpc_auth_create_args *args,
                struct rpc_clnt *clnt,
                struct gss_auth *new)
{
        struct gss_auth *gss_auth;
        unsigned long hashval = (unsigned long)clnt;

        spin_lock(&gss_auth_hash_lock);
        hash_for_each_possible(gss_auth_hash_table,
                        gss_auth,
                        hash,
                        hashval) {
                if (gss_auth->client != clnt)
                        continue;
                if (gss_auth->rpc_auth.au_flavor != args->pseudoflavor)
                        continue;
                if (gss_auth->target_name != args->target_name) {
                        if (gss_auth->target_name == NULL)
                                continue;
                        if (args->target_name == NULL)
                                continue;
                        if (strcmp(gss_auth->target_name, args->target_name))
                                continue;
                }
                if (!atomic_inc_not_zero(&gss_auth->rpc_auth.au_count))
                        continue;
                goto out;
        }
        if (new)
                hash_add(gss_auth_hash_table, &new->hash, hashval);
        gss_auth = new;
out:
        spin_unlock(&gss_auth_hash_lock);
        return gss_auth;
}

static struct gss_auth *
gss_create_hashed(struct rpc_auth_create_args *args, struct rpc_clnt *clnt)
{
        struct gss_auth *gss_auth;
        struct gss_auth *new;

        gss_auth = gss_auth_find_or_add_hashed(args, clnt, NULL);
        if (gss_auth != NULL)
                goto out;
        new = gss_create_new(args, clnt);
        if (IS_ERR(new))
                return new;
        gss_auth = gss_auth_find_or_add_hashed(args, clnt, new);
        if (gss_auth != new)
                gss_destroy(&new->rpc_auth);
out:
        return gss_auth;
}

static struct rpc_auth *
gss_create(struct rpc_auth_create_args *args, struct rpc_clnt *clnt)
{
        struct gss_auth *gss_auth;
        struct rpc_xprt_switch *xps = rcu_access_pointer(clnt->cl_xpi.xpi_xpswitch);

        while (clnt != clnt->cl_parent) {
                struct rpc_clnt *parent = clnt->cl_parent;
                /* Find the original parent for this transport */
                if (rcu_access_pointer(parent->cl_xpi.xpi_xpswitch) != xps)
                        break;
                clnt = parent;
        }

        gss_auth = gss_create_hashed(args, clnt);
        if (IS_ERR(gss_auth))
                return ERR_CAST(gss_auth);
        return &gss_auth->rpc_auth;
}

/*
 * gss_destroying_context will cause the RPCSEC_GSS to send a NULL RPC call
 * to the server with the GSS control procedure field set to
 * RPC_GSS_PROC_DESTROY. This should normally cause the server to release
 * all RPCSEC_GSS state associated with that context.
 */
static int
gss_destroying_context(struct rpc_cred *cred)
{
        struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
        struct gss_auth *gss_auth = container_of(cred->cr_auth, struct gss_auth, rpc_auth);
        struct gss_cl_ctx *ctx = rcu_dereference_protected(gss_cred->gc_ctx, 1);
        struct rpc_task *task;

        if (test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) == 0)
                return 0;

        ctx->gc_proc = RPC_GSS_PROC_DESTROY;
        cred->cr_ops = &gss_nullops;

        /* Take a reference to ensure the cred will be destroyed either
         * by the RPC call or by the put_rpccred() below */
        get_rpccred(cred);

        task = rpc_call_null(gss_auth->client, cred, RPC_TASK_ASYNC|RPC_TASK_SOFT);
        if (!IS_ERR(task))
                rpc_put_task(task);

        put_rpccred(cred);
        return 1;
}

/* gss_destroy_cred (and gss_free_ctx) are used to clean up after failure
 * to create a new cred or context, so they check that things have been
 * allocated before freeing them. */
static void
gss_do_free_ctx(struct gss_cl_ctx *ctx)
{
        dprintk("RPC:       %s\n", __func__);

        gss_delete_sec_context(&ctx->gc_gss_ctx);
        kfree(ctx->gc_wire_ctx.data);
        kfree(ctx->gc_acceptor.data);
        kfree(ctx);
}

static void
gss_free_ctx_callback(struct rcu_head *head)
{
        struct gss_cl_ctx *ctx = container_of(head, struct gss_cl_ctx, gc_rcu);
        gss_do_free_ctx(ctx);
}

static void
gss_free_ctx(struct gss_cl_ctx *ctx)
{
        call_rcu(&ctx->gc_rcu, gss_free_ctx_callback);
}

static void
gss_free_cred(struct gss_cred *gss_cred)
{
        dprintk("RPC:       %s cred=%p\n", __func__, gss_cred);
        kfree(gss_cred);
}

static void
gss_free_cred_callback(struct rcu_head *head)
{
        struct gss_cred *gss_cred = container_of(head, struct gss_cred, gc_base.cr_rcu);
        gss_free_cred(gss_cred);
}

static void
gss_destroy_nullcred(struct rpc_cred *cred)
{
        struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
        struct gss_auth *gss_auth = container_of(cred->cr_auth, struct gss_auth, rpc_auth);
        struct gss_cl_ctx *ctx = rcu_dereference_protected(gss_cred->gc_ctx, 1);

        RCU_INIT_POINTER(gss_cred->gc_ctx, NULL);
        call_rcu(&cred->cr_rcu, gss_free_cred_callback);
        if (ctx)
                gss_put_ctx(ctx);
        gss_put_auth(gss_auth);
}

static void
gss_destroy_cred(struct rpc_cred *cred)
{

        if (gss_destroying_context(cred))
                return;
        gss_destroy_nullcred(cred);
}

static int
gss_hash_cred(struct auth_cred *acred, unsigned int hashbits)
{
        return hash_64(from_kuid(&init_user_ns, acred->uid), hashbits);
}

/*
 * Lookup RPCSEC_GSS cred for the current process
 */
static struct rpc_cred *
gss_lookup_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
        return rpcauth_lookup_credcache(auth, acred, flags, GFP_NOFS);
}

static struct rpc_cred *
gss_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags, gfp_t gfp)
{
        struct gss_auth *gss_auth = container_of(auth, struct gss_auth, rpc_auth);
        struct gss_cred *cred = NULL;
        int err = -ENOMEM;

        dprintk("RPC:       %s for uid %d, flavor %d\n",
                __func__, from_kuid(&init_user_ns, acred->uid),
                auth->au_flavor);

        if (!(cred = kzalloc(sizeof(*cred), gfp)))
                goto out_err;

        rpcauth_init_cred(&cred->gc_base, acred, auth, &gss_credops);
        /*
         * Note: in order to force a call to call_refresh(), we deliberately
         * fail to flag the credential as RPCAUTH_CRED_UPTODATE.
         */
        cred->gc_base.cr_flags = 1UL << RPCAUTH_CRED_NEW;
        cred->gc_service = gss_auth->service;
        cred->gc_principal = NULL;
        if (acred->machine_cred)
                cred->gc_principal = acred->principal;
        kref_get(&gss_auth->kref);
        return &cred->gc_base;

out_err:
        dprintk("RPC:       %s failed with error %d\n", __func__, err);
        return ERR_PTR(err);
}

static int
gss_cred_init(struct rpc_auth *auth, struct rpc_cred *cred)
{
        struct gss_auth *gss_auth = container_of(auth, struct gss_auth, rpc_auth);
        struct gss_cred *gss_cred = container_of(cred,struct gss_cred, gc_base);
        int err;

        do {
                err = gss_create_upcall(gss_auth, gss_cred);
        } while (err == -EAGAIN);
        return err;
}

static char *
gss_stringify_acceptor(struct rpc_cred *cred)
{
        char *string = NULL;
        struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
        struct gss_cl_ctx *ctx;
        unsigned int len;
        struct xdr_netobj *acceptor;

        rcu_read_lock();
        ctx = rcu_dereference(gss_cred->gc_ctx);
        if (!ctx)
                goto out;

        len = ctx->gc_acceptor.len;
        rcu_read_unlock();

        /* no point if there's no string */
        if (!len)
                return NULL;
realloc:
        string = kmalloc(len + 1, GFP_KERNEL);
        if (!string)
                return NULL;

        rcu_read_lock();
        ctx = rcu_dereference(gss_cred->gc_ctx);

        /* did the ctx disappear or was it replaced by one with no acceptor? */
        if (!ctx || !ctx->gc_acceptor.len) {
                kfree(string);
                string = NULL;
                goto out;
        }

        acceptor = &ctx->gc_acceptor;

        /*
         * Did we find a new acceptor that's longer than the original? Allocate
         * a longer buffer and try again.
         */
        if (len < acceptor->len) {
                len = acceptor->len;
                rcu_read_unlock();
                kfree(string);
                goto realloc;
        }

        memcpy(string, acceptor->data, acceptor->len);
        string[acceptor->len] = '\0';
out:
        rcu_read_unlock();
        return string;
}

/*
 * Returns -EACCES if GSS context is NULL or will expire within the
 * timeout (miliseconds)
 */
static int
gss_key_timeout(struct rpc_cred *rc)
{
        struct gss_cred *gss_cred = container_of(rc, struct gss_cred, gc_base);
        struct gss_cl_ctx *ctx;
        unsigned long timeout = jiffies + (gss_key_expire_timeo * HZ);
        int ret = 0;

        rcu_read_lock();
        ctx = rcu_dereference(gss_cred->gc_ctx);
        if (!ctx || time_after(timeout, ctx->gc_expiry))
                ret = -EACCES;
        rcu_read_unlock();

        return ret;
}

static int
gss_match(struct auth_cred *acred, struct rpc_cred *rc, int flags)
{
        struct gss_cred *gss_cred = container_of(rc, struct gss_cred, gc_base);
        struct gss_cl_ctx *ctx;
        int ret;

        if (test_bit(RPCAUTH_CRED_NEW, &rc->cr_flags))
                goto out;
        /* Don't match with creds that have expired. */
        rcu_read_lock();
        ctx = rcu_dereference(gss_cred->gc_ctx);
        if (!ctx || time_after(jiffies, ctx->gc_expiry)) {
                rcu_read_unlock();
                return 0;
        }
        rcu_read_unlock();
        if (!test_bit(RPCAUTH_CRED_UPTODATE, &rc->cr_flags))
                return 0;
out:
        if (acred->principal != NULL) {
                if (gss_cred->gc_principal == NULL)
                        return 0;
                ret = strcmp(acred->principal, gss_cred->gc_principal) == 0;
                goto check_expire;
        }
        if (gss_cred->gc_principal != NULL)
                return 0;
        ret = uid_eq(rc->cr_uid, acred->uid);

check_expire:
        if (ret == 0)
                return ret;

        /* Notify acred users of GSS context expiration timeout */
        if (test_bit(RPC_CRED_NOTIFY_TIMEOUT, &acred->ac_flags) &&
            (gss_key_timeout(rc) != 0)) {
                /* test will now be done from generic cred */
                test_and_clear_bit(RPC_CRED_NOTIFY_TIMEOUT, &acred->ac_flags);
                /* tell NFS layer that key will expire soon */
                set_bit(RPC_CRED_KEY_EXPIRE_SOON, &acred->ac_flags);
        }
        return ret;
}

/*
* Marshal credentials.
* Maybe we should keep a cached credential for performance reasons.
*/
static __be32 *
gss_marshal(struct rpc_task *task, __be32 *p)
{
        struct rpc_rqst *req = task->tk_rqstp;
        struct rpc_cred *cred = req->rq_cred;
        struct gss_cred *gss_cred = container_of(cred, struct gss_cred,
                                                 gc_base);
        struct gss_cl_ctx       *ctx = gss_cred_get_ctx(cred);
        __be32          *cred_len;
        u32             maj_stat = 0;
        struct xdr_netobj mic;
        struct kvec     iov;
        struct xdr_buf  verf_buf;

        dprintk("RPC: %5u %s\n", task->tk_pid, __func__);

        *p++ = htonl(RPC_AUTH_GSS);
        cred_len = p++;

        spin_lock(&ctx->gc_seq_lock);
        req->rq_seqno = ctx->gc_seq++;
        spin_unlock(&ctx->gc_seq_lock);

        *p++ = htonl((u32) RPC_GSS_VERSION);
        *p++ = htonl((u32) ctx->gc_proc);
        *p++ = htonl((u32) req->rq_seqno);
        *p++ = htonl((u32) gss_cred->gc_service);
        p = xdr_encode_netobj(p, &ctx->gc_wire_ctx);
        *cred_len = htonl((p - (cred_len + 1)) << 2);

        /* We compute the checksum for the verifier over the xdr-encoded bytes
         * starting with the xid and ending at the end of the credential: */
        iov.iov_base = xprt_skip_transport_header(req->rq_xprt,
                                        req->rq_snd_buf.head[0].iov_base);
        iov.iov_len = (u8 *)p - (u8 *)iov.iov_base;
        xdr_buf_from_iov(&iov, &verf_buf);

        /* set verifier flavor*/
        *p++ = htonl(RPC_AUTH_GSS);

        mic.data = (u8 *)(p + 1);
        maj_stat = gss_get_mic(ctx->gc_gss_ctx, &verf_buf, &mic);
        if (maj_stat == GSS_S_CONTEXT_EXPIRED) {
                clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
        } else if (maj_stat != 0) {
                printk("gss_marshal: gss_get_mic FAILED (%d)\n", maj_stat);
                goto out_put_ctx;
        }
        p = xdr_encode_opaque(p, NULL, mic.len);
        gss_put_ctx(ctx);
        return p;
out_put_ctx:
        gss_put_ctx(ctx);
        return NULL;
}

static int gss_renew_cred(struct rpc_task *task)
{
        struct rpc_cred *oldcred = task->tk_rqstp->rq_cred;
        struct gss_cred *gss_cred = container_of(oldcred,
                                                 struct gss_cred,
                                                 gc_base);
        struct rpc_auth *auth = oldcred->cr_auth;
        struct auth_cred acred = {
                .uid = oldcred->cr_uid,
                .principal = gss_cred->gc_principal,
                .machine_cred = (gss_cred->gc_principal != NULL ? 1 : 0),
        };
        struct rpc_cred *new;

        new = gss_lookup_cred(auth, &acred, RPCAUTH_LOOKUP_NEW);
        if (IS_ERR(new))
                return PTR_ERR(new);
        task->tk_rqstp->rq_cred = new;
        put_rpccred(oldcred);
        return 0;
}

static int gss_cred_is_negative_entry(struct rpc_cred *cred)
{
        if (test_bit(RPCAUTH_CRED_NEGATIVE, &cred->cr_flags)) {
                unsigned long now = jiffies;
                unsigned long begin, expire;
                struct gss_cred *gss_cred; 

                gss_cred = container_of(cred, struct gss_cred, gc_base);
                begin = gss_cred->gc_upcall_timestamp;
                expire = begin + gss_expired_cred_retry_delay * HZ;

                if (time_in_range_open(now, begin, expire))
                        return 1;
        }
        return 0;
}

/*
* Refresh credentials. XXX - finish
*/
static int
gss_refresh(struct rpc_task *task)
{
        struct rpc_cred *cred = task->tk_rqstp->rq_cred;
        int ret = 0;

        if (gss_cred_is_negative_entry(cred))
                return -EKEYEXPIRED;

        if (!test_bit(RPCAUTH_CRED_NEW, &cred->cr_flags) &&
                        !test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags)) {
                ret = gss_renew_cred(task);
                if (ret < 0)
                        goto out;
                cred = task->tk_rqstp->rq_cred;
        }

        if (test_bit(RPCAUTH_CRED_NEW, &cred->cr_flags))
                ret = gss_refresh_upcall(task);
out:
        return ret;
}

/* Dummy refresh routine: used only when destroying the context */
static int
gss_refresh_null(struct rpc_task *task)
{
        return 0;
}

static __be32 *
gss_validate(struct rpc_task *task, __be32 *p)
{
        struct rpc_cred *cred = task->tk_rqstp->rq_cred;
        struct gss_cl_ctx *ctx = gss_cred_get_ctx(cred);
        __be32          *seq = NULL;
        struct kvec     iov;
        struct xdr_buf  verf_buf;
        struct xdr_netobj mic;
        u32             flav,len;
        u32             maj_stat;
        __be32          *ret = ERR_PTR(-EIO);

        dprintk("RPC: %5u %s\n", task->tk_pid, __func__);

        flav = ntohl(*p++);
        if ((len = ntohl(*p++)) > RPC_MAX_AUTH_SIZE)
                goto out_bad;
        if (flav != RPC_AUTH_GSS)
                goto out_bad;
        seq = kmalloc(4, GFP_NOFS);
        if (!seq)
                goto out_bad;
        *seq = htonl(task->tk_rqstp->rq_seqno);
        iov.iov_base = seq;
        iov.iov_len = 4;
        xdr_buf_from_iov(&iov, &verf_buf);
        mic.data = (u8 *)p;
        mic.len = len;

        ret = ERR_PTR(-EACCES);
        maj_stat = gss_verify_mic(ctx->gc_gss_ctx, &verf_buf, &mic);
        if (maj_stat == GSS_S_CONTEXT_EXPIRED)
                clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
        if (maj_stat) {
                dprintk("RPC: %5u %s: gss_verify_mic returned error 0x%08x\n",
                        task->tk_pid, __func__, maj_stat);
                goto out_bad;
        }
        /* We leave it to unwrap to calculate au_rslack. For now we just
         * calculate the length of the verifier: */
        cred->cr_auth->au_verfsize = XDR_QUADLEN(len) + 2;
        gss_put_ctx(ctx);
        dprintk("RPC: %5u %s: gss_verify_mic succeeded.\n",
                        task->tk_pid, __func__);
        kfree(seq);
        return p + XDR_QUADLEN(len);
out_bad:
        gss_put_ctx(ctx);
        dprintk("RPC: %5u %s failed ret %ld.\n", task->tk_pid, __func__,
                PTR_ERR(ret));
        kfree(seq);
        return ret;
}

static void gss_wrap_req_encode(kxdreproc_t encode, struct rpc_rqst *rqstp,
                                __be32 *p, void *obj)
{
        struct xdr_stream xdr;

        xdr_init_encode(&xdr, &rqstp->rq_snd_buf, p);
        encode(rqstp, &xdr, obj);
}

static inline int
gss_wrap_req_integ(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
                   kxdreproc_t encode, struct rpc_rqst *rqstp,
                   __be32 *p, void *obj)
{
        struct xdr_buf  *snd_buf = &rqstp->rq_snd_buf;
        struct xdr_buf  integ_buf;
        __be32          *integ_len = NULL;
        struct xdr_netobj mic;
        u32             offset;
        __be32          *q;
        struct kvec     *iov;
        u32             maj_stat = 0;
        int             status = -EIO;

        integ_len = p++;
        offset = (u8 *)p - (u8 *)snd_buf->head[0].iov_base;
        *p++ = htonl(rqstp->rq_seqno);

        gss_wrap_req_encode(encode, rqstp, p, obj);

        if (xdr_buf_subsegment(snd_buf, &integ_buf,
                                offset, snd_buf->len - offset))
                return status;
        *integ_len = htonl(integ_buf.len);

        /* guess whether we're in the head or the tail: */
        if (snd_buf->page_len || snd_buf->tail[0].iov_len)
                iov = snd_buf->tail;
        else
                iov = snd_buf->head;
        p = iov->iov_base + iov->iov_len;
        mic.data = (u8 *)(p + 1);

        maj_stat = gss_get_mic(ctx->gc_gss_ctx, &integ_buf, &mic);
        status = -EIO; /* XXX? */
        if (maj_stat == GSS_S_CONTEXT_EXPIRED)
                clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
        else if (maj_stat)
                return status;
        q = xdr_encode_opaque(p, NULL, mic.len);

        offset = (u8 *)q - (u8 *)p;
        iov->iov_len += offset;
        snd_buf->len += offset;
        return 0;
}

static void
priv_release_snd_buf(struct rpc_rqst *rqstp)
{
        int i;

        for (i=0; i < rqstp->rq_enc_pages_num; i++)
                __free_page(rqstp->rq_enc_pages[i]);
        kfree(rqstp->rq_enc_pages);
}

static int
alloc_enc_pages(struct rpc_rqst *rqstp)
{
        struct xdr_buf *snd_buf = &rqstp->rq_snd_buf;
        int first, last, i;

        if (snd_buf->page_len == 0) {
                rqstp->rq_enc_pages_num = 0;
                return 0;
        }

        first = snd_buf->page_base >> PAGE_SHIFT;
        last = (snd_buf->page_base + snd_buf->page_len - 1) >> PAGE_SHIFT;
        rqstp->rq_enc_pages_num = last - first + 1 + 1;
        rqstp->rq_enc_pages
                = kmalloc(rqstp->rq_enc_pages_num * sizeof(struct page *),
                                GFP_NOFS);
        if (!rqstp->rq_enc_pages)
                goto out;
        for (i=0; i < rqstp->rq_enc_pages_num; i++) {
                rqstp->rq_enc_pages[i] = alloc_page(GFP_NOFS);
                if (rqstp->rq_enc_pages[i] == NULL)
                        goto out_free;
        }
        rqstp->rq_release_snd_buf = priv_release_snd_buf;
        return 0;
out_free:
        rqstp->rq_enc_pages_num = i;
        priv_release_snd_buf(rqstp);
out:
        return -EAGAIN;
}

static inline int
gss_wrap_req_priv(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
                  kxdreproc_t encode, struct rpc_rqst *rqstp,
                  __be32 *p, void *obj)
{
        struct xdr_buf  *snd_buf = &rqstp->rq_snd_buf;
        u32             offset;
        u32             maj_stat;
        int             status;
        __be32          *opaque_len;
        struct page     **inpages;
        int             first;
        int             pad;
        struct kvec     *iov;
        char            *tmp;

        opaque_len = p++;
        offset = (u8 *)p - (u8 *)snd_buf->head[0].iov_base;
        *p++ = htonl(rqstp->rq_seqno);

        gss_wrap_req_encode(encode, rqstp, p, obj);

        status = alloc_enc_pages(rqstp);
        if (status)
                return status;
        first = snd_buf->page_base >> PAGE_SHIFT;
        inpages = snd_buf->pages + first;
        snd_buf->pages = rqstp->rq_enc_pages;
        snd_buf->page_base -= first << PAGE_SHIFT;
        /*
         * Give the tail its own page, in case we need extra space in the
         * head when wrapping:
         *
         * call_allocate() allocates twice the slack space required
         * by the authentication flavor to rq_callsize.
         * For GSS, slack is GSS_CRED_SLACK.
         */
        if (snd_buf->page_len || snd_buf->tail[0].iov_len) {
                tmp = page_address(rqstp->rq_enc_pages[rqstp->rq_enc_pages_num - 1]);
                memcpy(tmp, snd_buf->tail[0].iov_base, snd_buf->tail[0].iov_len);
                snd_buf->tail[0].iov_base = tmp;
        }
        maj_stat = gss_wrap(ctx->gc_gss_ctx, offset, snd_buf, inpages);
        /* slack space should prevent this ever happening: */
        BUG_ON(snd_buf->len > snd_buf->buflen);
        status = -EIO;
        /* We're assuming that when GSS_S_CONTEXT_EXPIRED, the encryption was
         * done anyway, so it's safe to put the request on the wire: */
        if (maj_stat == GSS_S_CONTEXT_EXPIRED)
                clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
        else if (maj_stat)
                return status;

        *opaque_len = htonl(snd_buf->len - offset);
        /* guess whether we're in the head or the tail: */
        if (snd_buf->page_len || snd_buf->tail[0].iov_len)
                iov = snd_buf->tail;
        else
                iov = snd_buf->head;
        p = iov->iov_base + iov->iov_len;
        pad = 3 - ((snd_buf->len - offset - 1) & 3);
        memset(p, 0, pad);
        iov->iov_len += pad;
        snd_buf->len += pad;

        return 0;
}

static int
gss_wrap_req(struct rpc_task *task,
             kxdreproc_t encode, void *rqstp, __be32 *p, void *obj)
{
        struct rpc_cred *cred = task->tk_rqstp->rq_cred;
        struct gss_cred *gss_cred = container_of(cred, struct gss_cred,
                        gc_base);
        struct gss_cl_ctx *ctx = gss_cred_get_ctx(cred);
        int             status = -EIO;

        dprintk("RPC: %5u %s\n", task->tk_pid, __func__);
        if (ctx->gc_proc != RPC_GSS_PROC_DATA) {
                /* The spec seems a little ambiguous here, but I think that not
                 * wrapping context destruction requests makes the most sense.
                 */
                gss_wrap_req_encode(encode, rqstp, p, obj);
                status = 0;
                goto out;
        }
        switch (gss_cred->gc_service) {
        case RPC_GSS_SVC_NONE:
                gss_wrap_req_encode(encode, rqstp, p, obj);
                status = 0;
                break;
        case RPC_GSS_SVC_INTEGRITY:
                status = gss_wrap_req_integ(cred, ctx, encode, rqstp, p, obj);
                break;
        case RPC_GSS_SVC_PRIVACY:
                status = gss_wrap_req_priv(cred, ctx, encode, rqstp, p, obj);
                break;
        }
out:
        gss_put_ctx(ctx);
        dprintk("RPC: %5u %s returning %d\n", task->tk_pid, __func__, status);
        return status;
}

static inline int
gss_unwrap_resp_integ(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
                struct rpc_rqst *rqstp, __be32 **p)
{
        struct xdr_buf  *rcv_buf = &rqstp->rq_rcv_buf;
        struct xdr_buf integ_buf;
        struct xdr_netobj mic;
        u32 data_offset, mic_offset;
        u32 integ_len;
        u32 maj_stat;
        int status = -EIO;

        integ_len = ntohl(*(*p)++);
        if (integ_len & 3)
                return status;
        data_offset = (u8 *)(*p) - (u8 *)rcv_buf->head[0].iov_base;
        mic_offset = integ_len + data_offset;
        if (mic_offset > rcv_buf->len)
                return status;
        if (ntohl(*(*p)++) != rqstp->rq_seqno)
                return status;

        if (xdr_buf_subsegment(rcv_buf, &integ_buf, data_offset,
                                mic_offset - data_offset))
                return status;

        if (xdr_buf_read_netobj(rcv_buf, &mic, mic_offset))
                return status;

        maj_stat = gss_verify_mic(ctx->gc_gss_ctx, &integ_buf, &mic);
        if (maj_stat == GSS_S_CONTEXT_EXPIRED)
                clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
        if (maj_stat != GSS_S_COMPLETE)
                return status;
        return 0;
}

static inline int
gss_unwrap_resp_priv(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
                struct rpc_rqst *rqstp, __be32 **p)
{
        struct xdr_buf  *rcv_buf = &rqstp->rq_rcv_buf;
        u32 offset;
        u32 opaque_len;
        u32 maj_stat;
        int status = -EIO;

        opaque_len = ntohl(*(*p)++);
        offset = (u8 *)(*p) - (u8 *)rcv_buf->head[0].iov_base;
        if (offset + opaque_len > rcv_buf->len)
                return status;
        /* remove padding: */
        rcv_buf->len = offset + opaque_len;

        maj_stat = gss_unwrap(ctx->gc_gss_ctx, offset, rcv_buf);
        if (maj_stat == GSS_S_CONTEXT_EXPIRED)
                clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
        if (maj_stat != GSS_S_COMPLETE)
                return status;
        if (ntohl(*(*p)++) != rqstp->rq_seqno)
                return status;

        return 0;
}

static int
gss_unwrap_req_decode(kxdrdproc_t decode, struct rpc_rqst *rqstp,
                      __be32 *p, void *obj)
{
        struct xdr_stream xdr;

        xdr_init_decode(&xdr, &rqstp->rq_rcv_buf, p);
        return decode(rqstp, &xdr, obj);
}

static int
gss_unwrap_resp(struct rpc_task *task,
                kxdrdproc_t decode, void *rqstp, __be32 *p, void *obj)
{
        struct rpc_cred *cred = task->tk_rqstp->rq_cred;
        struct gss_cred *gss_cred = container_of(cred, struct gss_cred,
                        gc_base);
        struct gss_cl_ctx *ctx = gss_cred_get_ctx(cred);
        __be32          *savedp = p;
        struct kvec     *head = ((struct rpc_rqst *)rqstp)->rq_rcv_buf.head;
        int             savedlen = head->iov_len;
        int             status = -EIO;

        if (ctx->gc_proc != RPC_GSS_PROC_DATA)
                goto out_decode;
        switch (gss_cred->gc_service) {
        case RPC_GSS_SVC_NONE:
                break;
        case RPC_GSS_SVC_INTEGRITY:
                status = gss_unwrap_resp_integ(cred, ctx, rqstp, &p);
                if (status)
                        goto out;
                break;
        case RPC_GSS_SVC_PRIVACY:
                status = gss_unwrap_resp_priv(cred, ctx, rqstp, &p);
                if (status)
                        goto out;
                break;
        }
        /* take into account extra slack for integrity and privacy cases: */
        cred->cr_auth->au_rslack = cred->cr_auth->au_verfsize + (p - savedp)
                                                + (savedlen - head->iov_len);
out_decode:
        status = gss_unwrap_req_decode(decode, rqstp, p, obj);
out:
        gss_put_ctx(ctx);
        dprintk("RPC: %5u %s returning %d\n",
                task->tk_pid, __func__, status);
        return status;
}

static const struct rpc_authops authgss_ops = {
        .owner          = THIS_MODULE,
        .au_flavor      = RPC_AUTH_GSS,
        .au_name        = "RPCSEC_GSS",
        .create         = gss_create,
        .destroy        = gss_destroy,

        .hash_cred      = gss_hash_cred,
        .lookup_cred    = gss_lookup_cred,
        .crcreate       = gss_create_cred,
        .list_pseudoflavors = gss_mech_list_pseudoflavors,
        .info2flavor    = gss_mech_info2flavor,
        .flavor2info    = gss_mech_flavor2info,
};

static const struct rpc_credops gss_credops = {
        .cr_name                = "AUTH_GSS",
        .crdestroy              = gss_destroy_cred,
        .cr_init                = gss_cred_init,
        .crbind                 = rpcauth_generic_bind_cred,
        .crmatch                = gss_match,
        .crmarshal              = gss_marshal,
        .crrefresh              = gss_refresh,
        .crvalidate             = gss_validate,
        .crwrap_req             = gss_wrap_req,
        .crunwrap_resp          = gss_unwrap_resp,
        .crkey_timeout          = gss_key_timeout,
        .crstringify_acceptor   = gss_stringify_acceptor,
};

static const struct rpc_credops gss_nullops = {
        .cr_name                = "AUTH_GSS",
        .crdestroy              = gss_destroy_nullcred,
        .crbind                 = rpcauth_generic_bind_cred,
        .crmatch                = gss_match,
        .crmarshal              = gss_marshal,
        .crrefresh              = gss_refresh_null,
        .crvalidate             = gss_validate,
        .crwrap_req             = gss_wrap_req,
        .crunwrap_resp          = gss_unwrap_resp,
        .crstringify_acceptor   = gss_stringify_acceptor,
};

static const struct rpc_pipe_ops gss_upcall_ops_v0 = {
        .upcall         = rpc_pipe_generic_upcall,
        .downcall       = gss_pipe_downcall,
        .destroy_msg    = gss_pipe_destroy_msg,
        .open_pipe      = gss_pipe_open_v0,
        .release_pipe   = gss_pipe_release,
};

static const struct rpc_pipe_ops gss_upcall_ops_v1 = {
        .upcall         = rpc_pipe_generic_upcall,
        .downcall       = gss_pipe_downcall,
        .destroy_msg    = gss_pipe_destroy_msg,
        .open_pipe      = gss_pipe_open_v1,
        .release_pipe   = gss_pipe_release,
};

static __net_init int rpcsec_gss_init_net(struct net *net)
{
        return gss_svc_init_net(net);
}

static __net_exit void rpcsec_gss_exit_net(struct net *net)
{
        gss_svc_shutdown_net(net);
}

static struct pernet_operations rpcsec_gss_net_ops = {
        .init = rpcsec_gss_init_net,
        .exit = rpcsec_gss_exit_net,
};

/*
 * Initialize RPCSEC_GSS module
 */
static int __init init_rpcsec_gss(void)
{
        int err = 0;

        err = rpcauth_register(&authgss_ops);
        if (err)
                goto out;
        err = gss_svc_init();
        if (err)
                goto out_unregister;
        err = register_pernet_subsys(&rpcsec_gss_net_ops);
        if (err)
                goto out_svc_exit;
        rpc_init_wait_queue(&pipe_version_rpc_waitqueue, "gss pipe version");
        return 0;
out_svc_exit:
        gss_svc_shutdown();
out_unregister:
        rpcauth_unregister(&authgss_ops);
out:
        return err;
}

static void __exit exit_rpcsec_gss(void)
{
        unregister_pernet_subsys(&rpcsec_gss_net_ops);
        gss_svc_shutdown();
        rpcauth_unregister(&authgss_ops);
        rcu_barrier(); /* Wait for completion of call_rcu()'s */
}

MODULE_ALIAS("rpc-auth-6");
MODULE_LICENSE("GPL");
module_param_named(expired_cred_retry_delay,
                   gss_expired_cred_retry_delay,
                   uint, 0644);
MODULE_PARM_DESC(expired_cred_retry_delay, "Timeout (in seconds) until "
                "the RPC engine retries an expired credential");

module_param_named(key_expire_timeo,
                   gss_key_expire_timeo,
                   uint, 0644);
MODULE_PARM_DESC(key_expire_timeo, "Time (in seconds) at the end of a "
                "credential keys lifetime where the NFS layer cleans up "
                "prior to key expiration");

module_init(init_rpcsec_gss)
module_exit(exit_rpcsec_gss)