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[linux-2.6/next.git] / net / sunrpc / auth_gss / auth_gss.c

/*
 * 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 <asm/uaccess.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;

#ifdef RPC_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

struct gss_auth {
        struct kref kref;
        struct rpc_auth rpc_auth;
        struct gss_api_mech *mech;
        enum rpc_gss_svc service;
        struct rpc_clnt *client;
        /*
         * 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 dentry *dentry[2];
};

/* pipe_version >= 0 if and only if someone has a pipe open. */
static int pipe_version = -1;
static atomic_t pipe_users = ATOMIC_INIT(0);
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_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)
{
        atomic_inc(&ctx->count);
        return ctx;
}

static inline void
gss_put_ctx(struct gss_cl_ctx *ctx)
{
        if (atomic_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 inode->i_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_clear_bit();
        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();
        if (gss_cred->gc_ctx)
                ctx = gss_get_ctx(gss_cred->gc_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);
                atomic_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;
        u32 window_size;
        int ret;

        /* First unsigned int gives the lifetime (in seconds) of the cred */
        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 = jiffies + (unsigned long)timeout * HZ * 3 / 4;
        /* 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, GFP_NOFS);
        if (ret < 0) {
                p = ERR_PTR(ret);
                goto err;
        }
        return q;
err:
        dprintk("RPC:       gss_fill_context returning %ld\n", -PTR_ERR(p));
        return p;
}

#define UPCALL_BUF_LEN 128

struct gss_upcall_msg {
        atomic_t count;
        uid_t   uid;
        struct rpc_pipe_msg msg;
        struct list_head list;
        struct gss_auth *auth;
        struct rpc_inode *inode;
        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(void)
{
        int ret;

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

static void put_pipe_version(void)
{
        if (atomic_dec_and_lock(&pipe_users, &pipe_version_lock)) {
                pipe_version = -1;
                spin_unlock(&pipe_version_lock);
        }
}

static void
gss_release_msg(struct gss_upcall_msg *gss_msg)
{
        if (!atomic_dec_and_test(&gss_msg->count))
                return;
        put_pipe_version();
        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);
        kfree(gss_msg);
}

static struct gss_upcall_msg *
__gss_find_upcall(struct rpc_inode *rpci, uid_t uid)
{
        struct gss_upcall_msg *pos;
        list_for_each_entry(pos, &rpci->in_downcall, list) {
                if (pos->uid != uid)
                        continue;
                atomic_inc(&pos->count);
                dprintk("RPC:       gss_find_upcall found msg %p\n", pos);
                return pos;
        }
        dprintk("RPC:       gss_find_upcall found nothing\n");
        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_inode *rpci = gss_msg->inode;
        struct inode *inode = &rpci->vfs_inode;
        struct gss_upcall_msg *old;

        spin_lock(&inode->i_lock);
        old = __gss_find_upcall(rpci, gss_msg->uid);
        if (old == NULL) {
                atomic_inc(&gss_msg->count);
                list_add(&gss_msg->list, &rpci->in_downcall);
        } else
                gss_msg = old;
        spin_unlock(&inode->i_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);
        atomic_dec(&gss_msg->count);
}

static void
gss_unhash_msg(struct gss_upcall_msg *gss_msg)
{
        struct inode *inode = &gss_msg->inode->vfs_inode;

        if (list_empty(&gss_msg->list))
                return;
        spin_lock(&inode->i_lock);
        if (!list_empty(&gss_msg->list))
                __gss_unhash_msg(gss_msg);
        spin_unlock(&inode->i_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 inode *inode = &gss_msg->inode->vfs_inode;

        spin_lock(&inode->i_lock);
        gss_handle_downcall_result(gss_cred, gss_msg);
        spin_unlock(&inode->i_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)
{
        gss_msg->msg.data = &gss_msg->uid;
        gss_msg->msg.len = sizeof(gss_msg->uid);
}

static void gss_encode_v1_msg(struct gss_upcall_msg *gss_msg,
                                struct rpc_clnt *clnt, int machine_cred)
{
        struct gss_api_mech *mech = gss_msg->auth->mech;
        char *p = gss_msg->databuf;
        int len = 0;

        gss_msg->msg.len = sprintf(gss_msg->databuf, "mech=%s uid=%d ",
                                   mech->gm_name,
                                   gss_msg->uid);
        p += gss_msg->msg.len;
        if (clnt->cl_principal) {
                len = sprintf(p, "target=%s ", clnt->cl_principal);
                p += len;
                gss_msg->msg.len += len;
        }
        if (machine_cred) {
                len = sprintf(p, "service=* ");
                p += len;
                gss_msg->msg.len += len;
        } else if (!strcmp(clnt->cl_program->name, "nfs4_cb")) {
                len = sprintf(p, "service=nfs ");
                p += len;
                gss_msg->msg.len += len;
        }
        if (mech->gm_upcall_enctypes) {
                len = sprintf(p, "enctypes=%s ", mech->gm_upcall_enctypes);
                p += len;
                gss_msg->msg.len += len;
        }
        len = sprintf(p, "\n");
        gss_msg->msg.len += len;

        gss_msg->msg.data = gss_msg->databuf;
        BUG_ON(gss_msg->msg.len > UPCALL_BUF_LEN);
}

static void gss_encode_msg(struct gss_upcall_msg *gss_msg,
                                struct rpc_clnt *clnt, int machine_cred)
{
        if (pipe_version == 0)
                gss_encode_v0_msg(gss_msg);
        else /* pipe_version == 1 */
                gss_encode_v1_msg(gss_msg, clnt, machine_cred);
}

static inline struct gss_upcall_msg *
gss_alloc_msg(struct gss_auth *gss_auth, uid_t uid, struct rpc_clnt *clnt,
                int machine_cred)
{
        struct gss_upcall_msg *gss_msg;
        int vers;

        gss_msg = kzalloc(sizeof(*gss_msg), GFP_NOFS);
        if (gss_msg == NULL)
                return ERR_PTR(-ENOMEM);
        vers = get_pipe_version();
        if (vers < 0) {
                kfree(gss_msg);
                return ERR_PTR(vers);
        }
        gss_msg->inode = RPC_I(gss_auth->dentry[vers]->d_inode);
        INIT_LIST_HEAD(&gss_msg->list);
        rpc_init_wait_queue(&gss_msg->rpc_waitqueue, "RPCSEC_GSS upcall waitq");
        init_waitqueue_head(&gss_msg->waitqueue);
        atomic_set(&gss_msg->count, 1);
        gss_msg->uid = uid;
        gss_msg->auth = gss_auth;
        gss_encode_msg(gss_msg, clnt, machine_cred);
        return gss_msg;
}

static struct gss_upcall_msg *
gss_setup_upcall(struct rpc_clnt *clnt, 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;
        uid_t uid = cred->cr_uid;

        gss_new = gss_alloc_msg(gss_auth, uid, clnt, gss_cred->gc_machine_cred);
        if (IS_ERR(gss_new))
                return gss_new;
        gss_msg = gss_add_msg(gss_new);
        if (gss_msg == gss_new) {
                struct inode *inode = &gss_new->inode->vfs_inode;
                int res = rpc_queue_upcall(inode, &gss_new->msg);
                if (res) {
                        gss_unhash_msg(gss_new);
                        gss_msg = ERR_PTR(res);
                }
        } else
                gss_release_msg(gss_new);
        return gss_msg;
}

static void warn_gssd(void)
{
        static unsigned long ratelimit;
        unsigned long now = jiffies;

        if (time_after(now, ratelimit)) {
                printk(KERN_WARNING "RPC: AUTH_GSS upcall timed out.\n"
                                "Please check user daemon is running.\n");
                ratelimit = now + 15*HZ;
        }
}

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 inode *inode;
        int err = 0;

        dprintk("RPC: %5u gss_refresh_upcall for uid %u\n", task->tk_pid,
                                                                cred->cr_uid);
        gss_msg = gss_setup_upcall(task->tk_client, 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;
        }
        inode = &gss_msg->inode->vfs_inode;
        spin_lock(&inode->i_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 */
                atomic_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(&inode->i_lock);
        gss_release_msg(gss_msg);
out:
        dprintk("RPC: %5u gss_refresh_upcall for uid %u result %d\n",
                        task->tk_pid, cred->cr_uid, err);
        return err;
}

static inline int
gss_create_upcall(struct gss_auth *gss_auth, struct gss_cred *gss_cred)
{
        struct inode *inode;
        struct rpc_cred *cred = &gss_cred->gc_base;
        struct gss_upcall_msg *gss_msg;
        DEFINE_WAIT(wait);
        int err = 0;

        dprintk("RPC:       gss_upcall for uid %u\n", cred->cr_uid);
retry:
        gss_msg = gss_setup_upcall(gss_auth->client, gss_auth, cred);
        if (PTR_ERR(gss_msg) == -EAGAIN) {
                err = wait_event_interruptible_timeout(pipe_version_waitqueue,
                                pipe_version >= 0, 15*HZ);
                if (pipe_version < 0) {
                        warn_gssd();
                        err = -EACCES;
                }
                if (err)
                        goto out;
                goto retry;
        }
        if (IS_ERR(gss_msg)) {
                err = PTR_ERR(gss_msg);
                goto out;
        }
        inode = &gss_msg->inode->vfs_inode;
        for (;;) {
                prepare_to_wait(&gss_msg->waitqueue, &wait, TASK_KILLABLE);
                spin_lock(&inode->i_lock);
                if (gss_msg->ctx != NULL || gss_msg->msg.errno < 0) {
                        break;
                }
                spin_unlock(&inode->i_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(&inode->i_lock);
out_intr:
        finish_wait(&gss_msg->waitqueue, &wait);
        gss_release_msg(gss_msg);
out:
        dprintk("RPC:       gss_create_upcall for uid %u result %d\n",
                        cred->cr_uid, err);
        return err;
}

static ssize_t
gss_pipe_upcall(struct file *filp, struct rpc_pipe_msg *msg,
                char __user *dst, size_t buflen)
{
        char *data = (char *)msg->data + msg->copied;
        size_t mlen = min(msg->len, buflen);
        unsigned long left;

        left = copy_to_user(dst, data, mlen);
        if (left == mlen) {
                msg->errno = -EFAULT;
                return -EFAULT;
        }

        mlen -= left;
        msg->copied += mlen;
        msg->errno = 0;
        return mlen;
}

#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 inode *inode = filp->f_path.dentry->d_inode;
        struct gss_cl_ctx *ctx;
        uid_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, &uid, sizeof(uid));
        if (IS_ERR(p)) {
                err = PTR_ERR(p);
                goto err;
        }

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

        err = -ENOENT;
        /* Find a matching upcall */
        spin_lock(&inode->i_lock);
        gss_msg = __gss_find_upcall(RPC_I(inode), uid);
        if (gss_msg == NULL) {
                spin_unlock(&inode->i_lock);
                goto err_put_ctx;
        }
        list_del_init(&gss_msg->list);
        spin_unlock(&inode->i_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);
                        BUG();
                }
                goto err_release_msg;
        }
        gss_msg->ctx = gss_get_ctx(ctx);
        err = mlen;

err_release_msg:
        spin_lock(&inode->i_lock);
        __gss_unhash_msg(gss_msg);
        spin_unlock(&inode->i_lock);
        gss_release_msg(gss_msg);
err_put_ctx:
        gss_put_ctx(ctx);
err:
        kfree(buf);
out:
        dprintk("RPC:       gss_pipe_downcall returning %Zd\n", err);
        return err;
}

static int gss_pipe_open(struct inode *inode, int new_version)
{
        int ret = 0;

        spin_lock(&pipe_version_lock);
        if (pipe_version < 0) {
                /* First open of any gss pipe determines the version: */
                pipe_version = new_version;
                rpc_wake_up(&pipe_version_rpc_waitqueue);
                wake_up(&pipe_version_waitqueue);
        } else if (pipe_version != new_version) {
                /* Trying to open a pipe of a different version */
                ret = -EBUSY;
                goto out;
        }
        atomic_inc(&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 rpc_inode *rpci = RPC_I(inode);
        struct gss_upcall_msg *gss_msg;

restart:
        spin_lock(&inode->i_lock);
        list_for_each_entry(gss_msg, &rpci->in_downcall, list) {

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

        put_pipe_version();
}

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:       gss_pipe_destroy_msg releasing msg %p\n",
                                gss_msg);
                atomic_inc(&gss_msg->count);
                gss_unhash_msg(gss_msg);
                if (msg->errno == -ETIMEDOUT)
                        warn_gssd();
                gss_release_msg(gss_msg);
        }
}

/*
 * NOTE: we have the opportunity to use different
 * parameters based on the input flavor (which must be a pseudoflavor)
 */
static struct rpc_auth *
gss_create(struct rpc_clnt *clnt, rpc_authflavor_t flavor)
{
        struct gss_auth *gss_auth;
        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;
        gss_auth->client = clnt;
        err = -EINVAL;
        gss_auth->mech = gss_mech_get_by_pseudoflavor(flavor);
        if (!gss_auth->mech) {
                printk(KERN_WARNING "%s: Pseudoflavor %d not found!\n",
                                __func__, flavor);
                goto err_free;
        }
        gss_auth->service = gss_pseudoflavor_to_service(gss_auth->mech, flavor);
        if (gss_auth->service == 0)
                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_ops = &authgss_ops;
        auth->au_flavor = flavor;
        atomic_set(&auth->au_count, 1);
        kref_init(&gss_auth->kref);

        /*
         * 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_auth->dentry[1] = rpc_mkpipe(clnt->cl_path.dentry,
                                         "gssd",
                                         clnt, &gss_upcall_ops_v1,
                                         RPC_PIPE_WAIT_FOR_OPEN);
        if (IS_ERR(gss_auth->dentry[1])) {
                err = PTR_ERR(gss_auth->dentry[1]);
                goto err_put_mech;
        }

        gss_auth->dentry[0] = rpc_mkpipe(clnt->cl_path.dentry,
                                         gss_auth->mech->gm_name,
                                         clnt, &gss_upcall_ops_v0,
                                         RPC_PIPE_WAIT_FOR_OPEN);
        if (IS_ERR(gss_auth->dentry[0])) {
                err = PTR_ERR(gss_auth->dentry[0]);
                goto err_unlink_pipe_1;
        }
        err = rpcauth_init_credcache(auth);
        if (err)
                goto err_unlink_pipe_0;

        return auth;
err_unlink_pipe_0:
        rpc_unlink(gss_auth->dentry[0]);
err_unlink_pipe_1:
        rpc_unlink(gss_auth->dentry[1]);
err_put_mech:
        gss_mech_put(gss_auth->mech);
err_free:
        kfree(gss_auth);
out_dec:
        module_put(THIS_MODULE);
        return ERR_PTR(err);
}

static void
gss_free(struct gss_auth *gss_auth)
{
        rpc_unlink(gss_auth->dentry[1]);
        rpc_unlink(gss_auth->dentry[0]);
        gss_mech_put(gss_auth->mech);

        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_destroy(struct rpc_auth *auth)
{
        struct gss_auth *gss_auth;

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

        rpcauth_destroy_credcache(auth);

        gss_auth = container_of(auth, struct gss_auth, rpc_auth);
        kref_put(&gss_auth->kref, gss_free_callback);
}

/*
 * 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 rpc_task *task;

        if (gss_cred->gc_ctx == NULL ||
            test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) == 0)
                return 0;

        gss_cred->gc_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:       gss_free_ctx\n");

        gss_delete_sec_context(&ctx->gc_gss_ctx);
        kfree(ctx->gc_wire_ctx.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:       gss_free_cred %p\n", 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 = gss_cred->gc_ctx;

        rcu_assign_pointer(gss_cred->gc_ctx, NULL);
        call_rcu(&cred->cr_rcu, gss_free_cred_callback);
        if (ctx)
                gss_put_ctx(ctx);
        kref_put(&gss_auth->kref, gss_free_callback);
}

static void
gss_destroy_cred(struct rpc_cred *cred)
{

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

/*
 * 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);
}

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

        dprintk("RPC:       gss_create_cred for uid %d, flavor %d\n",
                acred->uid, auth->au_flavor);

        if (!(cred = kzalloc(sizeof(*cred), GFP_NOFS)))
                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_machine_cred = acred->machine_cred;
        kref_get(&gss_auth->kref);
        return &cred->gc_base;

out_err:
        dprintk("RPC:       gss_create_cred failed with error %d\n", 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 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);

        if (test_bit(RPCAUTH_CRED_NEW, &rc->cr_flags))
                goto out;
        /* Don't match with creds that have expired. */
        if (time_after(jiffies, gss_cred->gc_ctx->gc_expiry))
                return 0;
        if (!test_bit(RPCAUTH_CRED_UPTODATE, &rc->cr_flags))
                return 0;
out:
        if (acred->machine_cred != gss_cred->gc_machine_cred)
                return 0;
        return rc->cr_uid == acred->uid;
}

/*
* 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 gss_marshal\n", task->tk_pid);

        *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(task->tk_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,
                .machine_cred = gss_cred->gc_machine_cred,
        };
        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 -EACCES;
}

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;
        struct kvec     iov;
        struct xdr_buf  verf_buf;
        struct xdr_netobj mic;
        u32             flav,len;
        u32             maj_stat;

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

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

        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 gss_validate: gss_verify_mic returned "
                                "error 0x%08x\n", task->tk_pid, 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 gss_validate: gss_verify_mic succeeded.\n",
                        task->tk_pid);
        return p + XDR_QUADLEN(len);
out_bad:
        gss_put_ctx(ctx);
        dprintk("RPC: %5u gss_validate failed.\n", task->tk_pid);
        return NULL;
}

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_CACHE_SHIFT;
        last = (snd_buf->page_base + snd_buf->page_len - 1) >> PAGE_CACHE_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_CACHE_SHIFT;
        inpages = snd_buf->pages + first;
        snd_buf->pages = rqstp->rq_enc_pages;
        snd_buf->page_base -= first << PAGE_CACHE_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 gss_wrap_req\n", task->tk_pid);
        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 gss_wrap_req returning %d\n", task->tk_pid, 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 gss_unwrap_resp returning %d\n", task->tk_pid,
                        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,
        .lookup_cred    = gss_lookup_cred,
        .crcreate       = gss_create_cred
};

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,
};

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,
};

static const struct rpc_pipe_ops gss_upcall_ops_v0 = {
        .upcall         = gss_pipe_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         = gss_pipe_upcall,
        .downcall       = gss_pipe_downcall,
        .destroy_msg    = gss_pipe_destroy_msg,
        .open_pipe      = gss_pipe_open_v1,
        .release_pipe   = gss_pipe_release,
};

/*
 * 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;
        rpc_init_wait_queue(&pipe_version_rpc_waitqueue, "gss pipe version");
        return 0;
out_unregister:
        rpcauth_unregister(&authgss_ops);
out:
        return err;
}

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

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_init(init_rpcsec_gss)
module_exit(exit_rpcsec_gss)