Linux-2.6.12-rc2

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

/*
 * linux/net/sunrpc/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.
 *
 * $Id$
 */


#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/sched.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 struct rpc_authops authgss_ops;

static struct rpc_credops gss_credops;

#ifdef RPC_DEBUG
# define RPCDBG_FACILITY        RPCDBG_AUTH
#endif

#define NFS_NGROUPS     16

#define GSS_CRED_EXPIRE         (60 * HZ)       /* XXX: reasonable? */
#define GSS_CRED_SLACK          1024            /* XXX: unused */
/* length of a krb5 verifier (48), plus data added before arguments when
 * using integrity (two 4-byte integers): */
#define GSS_VERF_SLACK          56

/* XXX this define must match the gssd define
* as it is passed to gssd to signal the use of
* machine creds should be part of the shared rpc interface */

#define CA_RUN_AS_MACHINE  0x00000200 

/* dump the buffer in `emacs-hexl' style */
#define isprint(c)      ((c > 0x1f) && (c < 0x7f))

static DEFINE_RWLOCK(gss_ctx_lock);

struct gss_auth {
        struct rpc_auth rpc_auth;
        struct gss_api_mech *mech;
        enum rpc_gss_svc service;
        struct list_head upcalls;
        struct rpc_clnt *client;
        struct dentry *dentry;
        char path[48];
        spinlock_t lock;
};

static void gss_destroy_ctx(struct gss_cl_ctx *);
static struct rpc_pipe_ops gss_upcall_ops;

void
print_hexl(u32 *p, u_int length, u_int offset)
{
        u_int i, j, jm;
        u8 c, *cp;
        
        dprintk("RPC: print_hexl: length %d\n",length);
        dprintk("\n");
        cp = (u8 *) p;
        
        for (i = 0; i < length; i += 0x10) {
                dprintk("  %04x: ", (u_int)(i + offset));
                jm = length - i;
                jm = jm > 16 ? 16 : jm;
                
                for (j = 0; j < jm; j++) {
                        if ((j % 2) == 1)
                                dprintk("%02x ", (u_int)cp[i+j]);
                        else
                                dprintk("%02x", (u_int)cp[i+j]);
                }
                for (; j < 16; j++) {
                        if ((j % 2) == 1)
                                dprintk("   ");
                        else
                                dprintk("  ");
                }
                dprintk(" ");
                
                for (j = 0; j < jm; j++) {
                        c = cp[i+j];
                        c = isprint(c) ? c : '.';
                        dprintk("%c", c);
                }
                dprintk("\n");
        }
}

EXPORT_SYMBOL(print_hexl);

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_destroy_ctx(ctx);
}

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);
        struct gss_cl_ctx *old;
        write_lock(&gss_ctx_lock);
        old = gss_cred->gc_ctx;
        gss_cred->gc_ctx = ctx;
        cred->cr_flags |= RPCAUTH_CRED_UPTODATE;
        write_unlock(&gss_ctx_lock);
        if (old)
                gss_put_ctx(old);
}

static int
gss_cred_is_uptodate_ctx(struct rpc_cred *cred)
{
        struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
        int res = 0;

        read_lock(&gss_ctx_lock);
        if ((cred->cr_flags & RPCAUTH_CRED_UPTODATE) && gss_cred->gc_ctx)
                res = 1;
        read_unlock(&gss_ctx_lock);
        return res;
}

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 = kmalloc(len, GFP_KERNEL);
        if (unlikely(dest->data == NULL))
                return ERR_PTR(-ENOMEM);
        dest->len = len;
        memcpy(dest->data, p, 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;

        read_lock(&gss_ctx_lock);
        if (gss_cred->gc_ctx)
                ctx = gss_get_ctx(gss_cred->gc_ctx);
        read_unlock(&gss_ctx_lock);
        return ctx;
}

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

        ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
        if (ctx != NULL) {
                memset(ctx, 0, sizeof(*ctx));
                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 which we ignore */
                p = 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);
        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;
}


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_wait_queue rpc_waitqueue;
        wait_queue_head_t waitqueue;
        struct gss_cl_ctx *ctx;
};

static void
gss_release_msg(struct gss_upcall_msg *gss_msg)
{
        if (!atomic_dec_and_test(&gss_msg->count))
                return;
        BUG_ON(!list_empty(&gss_msg->list));
        if (gss_msg->ctx != NULL)
                gss_put_ctx(gss_msg->ctx);
        kfree(gss_msg);
}

static struct gss_upcall_msg *
__gss_find_upcall(struct gss_auth *gss_auth, uid_t uid)
{
        struct gss_upcall_msg *pos;
        list_for_each_entry(pos, &gss_auth->upcalls, 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 a 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_auth *gss_auth, struct gss_upcall_msg *gss_msg)
{
        struct gss_upcall_msg *old;

        spin_lock(&gss_auth->lock);
        old = __gss_find_upcall(gss_auth, gss_msg->uid);
        if (old == NULL) {
                atomic_inc(&gss_msg->count);
                list_add(&gss_msg->list, &gss_auth->upcalls);
        } else
                gss_msg = old;
        spin_unlock(&gss_auth->lock);
        return gss_msg;
}

static void
__gss_unhash_msg(struct gss_upcall_msg *gss_msg)
{
        if (list_empty(&gss_msg->list))
                return;
        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 gss_auth *gss_auth = gss_msg->auth;

        spin_lock(&gss_auth->lock);
        __gss_unhash_msg(gss_msg);
        spin_unlock(&gss_auth->lock);
}

static void
gss_upcall_callback(struct rpc_task *task)
{
        struct gss_cred *gss_cred = container_of(task->tk_msg.rpc_cred,
                        struct gss_cred, gc_base);
        struct gss_upcall_msg *gss_msg = gss_cred->gc_upcall;

        BUG_ON(gss_msg == NULL);
        if (gss_msg->ctx)
                gss_cred_set_ctx(task->tk_msg.rpc_cred, gss_get_ctx(gss_msg->ctx));
        else
                task->tk_status = gss_msg->msg.errno;
        spin_lock(&gss_msg->auth->lock);
        gss_cred->gc_upcall = NULL;
        rpc_wake_up_status(&gss_msg->rpc_waitqueue, gss_msg->msg.errno);
        spin_unlock(&gss_msg->auth->lock);
        gss_release_msg(gss_msg);
}

static inline struct gss_upcall_msg *
gss_alloc_msg(struct gss_auth *gss_auth, uid_t uid)
{
        struct gss_upcall_msg *gss_msg;

        gss_msg = kmalloc(sizeof(*gss_msg), GFP_KERNEL);
        if (gss_msg != NULL) {
                memset(gss_msg, 0, sizeof(*gss_msg));
                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->msg.data = &gss_msg->uid;
                gss_msg->msg.len = sizeof(gss_msg->uid);
                gss_msg->uid = uid;
                gss_msg->auth = gss_auth;
        }
        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_upcall_msg *gss_new, *gss_msg;

        gss_new = gss_alloc_msg(gss_auth, cred->cr_uid);
        if (gss_new == NULL)
                return ERR_PTR(-ENOMEM);
        gss_msg = gss_add_msg(gss_auth, gss_new);
        if (gss_msg == gss_new) {
                int res = rpc_queue_upcall(gss_auth->dentry->d_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 inline int
gss_refresh_upcall(struct rpc_task *task)
{
        struct rpc_cred *cred = task->tk_msg.rpc_cred;
        struct gss_auth *gss_auth = container_of(task->tk_client->cl_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;
        int err = 0;

        dprintk("RPC: %4u 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 (IS_ERR(gss_msg)) {
                err = PTR_ERR(gss_msg);
                goto out;
        }
        spin_lock(&gss_auth->lock);
        if (gss_cred->gc_upcall != NULL)
                rpc_sleep_on(&gss_cred->gc_upcall->rpc_waitqueue, task, NULL, 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, NULL);
        } else
                err = gss_msg->msg.errno;
        spin_unlock(&gss_auth->lock);
        gss_release_msg(gss_msg);
out:
        dprintk("RPC: %4u 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 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);
        gss_msg = gss_setup_upcall(gss_auth->client, gss_auth, cred);
        if (IS_ERR(gss_msg)) {
                err = PTR_ERR(gss_msg);
                goto out;
        }
        for (;;) {
                prepare_to_wait(&gss_msg->waitqueue, &wait, TASK_INTERRUPTIBLE);
                spin_lock(&gss_auth->lock);
                if (gss_msg->ctx != NULL || gss_msg->msg.errno < 0) {
                        spin_unlock(&gss_auth->lock);
                        break;
                }
                spin_unlock(&gss_auth->lock);
                if (signalled()) {
                        err = -ERESTARTSYS;
                        goto out_intr;
                }
                schedule();
        }
        if (gss_msg->ctx)
                gss_cred_set_ctx(cred, gss_get_ctx(gss_msg->ctx));
        else
                err = gss_msg->msg.errno;
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;
        ssize_t mlen = msg->len;
        ssize_t left;

        if (mlen > buflen)
                mlen = buflen;
        left = copy_to_user(dst, data, mlen);
        if (left < 0) {
                msg->errno = left;
                return left;
        }
        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 rpc_clnt *clnt;
        struct gss_auth *gss_auth;
        struct rpc_cred *cred;
        struct gss_upcall_msg *gss_msg;
        struct gss_cl_ctx *ctx;
        uid_t uid;
        int err = -EFBIG;

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

        clnt = RPC_I(filp->f_dentry->d_inode)->private;
        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 = 0;
        gss_auth = container_of(clnt->cl_auth, struct gss_auth, rpc_auth);
        p = gss_fill_context(p, end, ctx, gss_auth->mech);
        if (IS_ERR(p)) {
                err = PTR_ERR(p);
                if (err != -EACCES)
                        goto err_put_ctx;
        }
        spin_lock(&gss_auth->lock);
        gss_msg = __gss_find_upcall(gss_auth, uid);
        if (gss_msg) {
                if (err == 0 && gss_msg->ctx == NULL)
                        gss_msg->ctx = gss_get_ctx(ctx);
                gss_msg->msg.errno = err;
                __gss_unhash_msg(gss_msg);
                spin_unlock(&gss_auth->lock);
                gss_release_msg(gss_msg);
        } else {
                struct auth_cred acred = { .uid = uid };
                spin_unlock(&gss_auth->lock);
                cred = rpcauth_lookup_credcache(clnt->cl_auth, &acred, 0);
                if (IS_ERR(cred)) {
                        err = PTR_ERR(cred);
                        goto err_put_ctx;
                }
                gss_cred_set_ctx(cred, gss_get_ctx(ctx));
        }
        gss_put_ctx(ctx);
        kfree(buf);
        dprintk("RPC:      gss_pipe_downcall returning length %Zu\n", mlen);
        return mlen;
err_put_ctx:
        gss_put_ctx(ctx);
err:
        kfree(buf);
out:
        dprintk("RPC:      gss_pipe_downcall returning %d\n", err);
        return err;
}

static void
gss_pipe_release(struct inode *inode)
{
        struct rpc_inode *rpci = RPC_I(inode);
        struct rpc_clnt *clnt;
        struct rpc_auth *auth;
        struct gss_auth *gss_auth;

        clnt = rpci->private;
        auth = clnt->cl_auth;
        gss_auth = container_of(auth, struct gss_auth, rpc_auth);
        spin_lock(&gss_auth->lock);
        while (!list_empty(&gss_auth->upcalls)) {
                struct gss_upcall_msg *gss_msg;

                gss_msg = list_entry(gss_auth->upcalls.next,
                                struct gss_upcall_msg, list);
                gss_msg->msg.errno = -EPIPE;
                atomic_inc(&gss_msg->count);
                __gss_unhash_msg(gss_msg);
                spin_unlock(&gss_auth->lock);
                gss_release_msg(gss_msg);
                spin_lock(&gss_auth->lock);
        }
        spin_unlock(&gss_auth->lock);
}

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);
        static unsigned long ratelimit;

        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 || msg->errno == -EPIPE) {
                        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;
                        }
                }
                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;

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

        if (!try_module_get(THIS_MODULE))
                return NULL;
        if (!(gss_auth = kmalloc(sizeof(*gss_auth), GFP_KERNEL)))
                goto out_dec;
        gss_auth->client = clnt;
        gss_auth->mech = gss_mech_get_by_pseudoflavor(flavor);
        if (!gss_auth->mech) {
                printk(KERN_WARNING "%s: Pseudoflavor %d not found!",
                                __FUNCTION__, flavor);
                goto err_free;
        }
        gss_auth->service = gss_pseudoflavor_to_service(gss_auth->mech, flavor);
        /* FIXME: Will go away once privacy support is merged in */
        if (gss_auth->service == RPC_GSS_SVC_PRIVACY)
                gss_auth->service = RPC_GSS_SVC_INTEGRITY;
        INIT_LIST_HEAD(&gss_auth->upcalls);
        spin_lock_init(&gss_auth->lock);
        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);

        if (rpcauth_init_credcache(auth, GSS_CRED_EXPIRE) < 0)
                goto err_put_mech;

        snprintf(gss_auth->path, sizeof(gss_auth->path), "%s/%s",
                        clnt->cl_pathname,
                        gss_auth->mech->gm_name);
        gss_auth->dentry = rpc_mkpipe(gss_auth->path, clnt, &gss_upcall_ops, RPC_PIPE_WAIT_FOR_OPEN);
        if (IS_ERR(gss_auth->dentry))
                goto err_put_mech;

        return auth;
err_put_mech:
        gss_mech_put(gss_auth->mech);
err_free:
        kfree(gss_auth);
out_dec:
        module_put(THIS_MODULE);
        return NULL;
}

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);

        gss_auth = container_of(auth, struct gss_auth, rpc_auth);
        rpc_unlink(gss_auth->path);
        gss_mech_put(gss_auth->mech);

        rpcauth_free_credcache(auth);
        kfree(gss_auth);
        module_put(THIS_MODULE);
}

/* gss_destroy_cred (and gss_destroy_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_destroy_ctx(struct gss_cl_ctx *ctx)
{
        dprintk("RPC:      gss_destroy_ctx\n");

        if (ctx->gc_gss_ctx)
                gss_delete_sec_context(&ctx->gc_gss_ctx);

        kfree(ctx->gc_wire_ctx.data);
        kfree(ctx);
}

static void
gss_destroy_cred(struct rpc_cred *rc)
{
        struct gss_cred *cred = container_of(rc, struct gss_cred, gc_base);

        dprintk("RPC:      gss_destroy_cred \n");

        if (cred->gc_ctx)
                gss_put_ctx(cred->gc_ctx);
        kfree(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 taskflags)
{
        return rpcauth_lookup_credcache(auth, acred, taskflags);
}

static struct rpc_cred *
gss_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int taskflags)
{
        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 = kmalloc(sizeof(*cred), GFP_KERNEL)))
                goto out_err;

        memset(cred, 0, sizeof(*cred));
        atomic_set(&cred->gc_count, 1);
        cred->gc_uid = acred->uid;
        /*
         * Note: in order to force a call to call_refresh(), we deliberately
         * fail to flag the credential as RPCAUTH_CRED_UPTODATE.
         */
        cred->gc_flags = 0;
        cred->gc_base.cr_ops = &gss_credops;
        cred->gc_service = gss_auth->service;
        err = gss_create_upcall(gss_auth, cred);
        if (err < 0)
                goto out_err;

        return &cred->gc_base;

out_err:
        dprintk("RPC:      gss_create_cred failed with error %d\n", err);
        if (cred) gss_destroy_cred(&cred->gc_base);
        return ERR_PTR(err);
}

static int
gss_match(struct auth_cred *acred, struct rpc_cred *rc, int taskflags)
{
        struct gss_cred *gss_cred = container_of(rc, struct gss_cred, gc_base);

        /* Don't match with creds that have expired. */
        if (gss_cred->gc_ctx && time_after(jiffies, gss_cred->gc_ctx->gc_expiry))
                return 0;
        return (rc->cr_uid == acred->uid);
}

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

        dprintk("RPC: %4u 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 = req->rq_snd_buf.head[0].iov_base;
        if (task->tk_client->cl_xprt->stream)
                /* See clnt.c:call_header() */
                iov.iov_base += 4;
        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,
                               GSS_C_QOP_DEFAULT, 
                               &verf_buf, &mic);
        if (maj_stat == GSS_S_CONTEXT_EXPIRED) {
                cred->cr_flags &= ~RPCAUTH_CRED_UPTODATE;
        } 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;
}

/*
* Refresh credentials. XXX - finish
*/
static int
gss_refresh(struct rpc_task *task)
{

        if (!gss_cred_is_uptodate_ctx(task->tk_msg.rpc_cred))
                return gss_refresh_upcall(task);
        return 0;
}

static u32 *
gss_validate(struct rpc_task *task, u32 *p)
{
        struct rpc_cred *cred = task->tk_msg.rpc_cred;
        struct gss_cred *gss_cred = container_of(cred, struct gss_cred,
                                                gc_base);
        struct gss_cl_ctx *ctx = gss_cred_get_ctx(cred);
        u32             seq, qop_state;
        struct kvec     iov;
        struct xdr_buf  verf_buf;
        struct xdr_netobj mic;
        u32             flav,len;
        u32             maj_stat;

        dprintk("RPC: %4u 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, &qop_state);
        if (maj_stat == GSS_S_CONTEXT_EXPIRED)
                cred->cr_flags &= ~RPCAUTH_CRED_UPTODATE;
        if (maj_stat)
                goto out_bad;
       switch (gss_cred->gc_service) {
       case RPC_GSS_SVC_NONE:
               /* verifier data, flavor, length: */
               task->tk_auth->au_rslack = XDR_QUADLEN(len) + 2;
               break;
       case RPC_GSS_SVC_INTEGRITY:
               /* verifier data, flavor, length, length, sequence number: */
               task->tk_auth->au_rslack = XDR_QUADLEN(len) + 4;
               break;
       case RPC_GSS_SVC_PRIVACY:
               goto out_bad;
       }
        gss_put_ctx(ctx);
        dprintk("RPC: %4u GSS gss_validate: gss_verify_mic succeeded.\n",
                        task->tk_pid);
        return p + XDR_QUADLEN(len);
out_bad:
        gss_put_ctx(ctx);
        dprintk("RPC: %4u gss_validate failed.\n", task->tk_pid);
        return NULL;
}

static inline int
gss_wrap_req_integ(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
                kxdrproc_t encode, struct rpc_rqst *rqstp, u32 *p, void *obj)
{
        struct xdr_buf  *snd_buf = &rqstp->rq_snd_buf;
        struct xdr_buf  integ_buf;
        u32             *integ_len = NULL;
        struct xdr_netobj mic;
        u32             offset, *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);

        status = encode(rqstp, p, obj);
        if (status)
                return status;

        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,
                        GSS_C_QOP_DEFAULT, &integ_buf, &mic);
        status = -EIO; /* XXX? */
        if (maj_stat == GSS_S_CONTEXT_EXPIRED)
                cred->cr_flags &= ~RPCAUTH_CRED_UPTODATE;
        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 int
gss_wrap_req(struct rpc_task *task,
             kxdrproc_t encode, void *rqstp, u32 *p, void *obj)
{
        struct rpc_cred *cred = task->tk_msg.rpc_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: %4u 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.
                 */
                status = encode(rqstp, p, obj);
                goto out;
        }
        switch (gss_cred->gc_service) {
                case RPC_GSS_SVC_NONE:
                        status = encode(rqstp, p, obj);
                        break;
                case RPC_GSS_SVC_INTEGRITY:
                        status = gss_wrap_req_integ(cred, ctx, encode,
                                                                rqstp, p, obj);
                        break;
                case RPC_GSS_SVC_PRIVACY:
                        break;
        }
out:
        gss_put_ctx(ctx);
        dprintk("RPC: %4u 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, u32 **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, NULL);
        if (maj_stat == GSS_S_CONTEXT_EXPIRED)
                cred->cr_flags &= ~RPCAUTH_CRED_UPTODATE;
        if (maj_stat != GSS_S_COMPLETE)
                return status;
        return 0;
}

static int
gss_unwrap_resp(struct rpc_task *task,
                kxdrproc_t decode, void *rqstp, u32 *p, void *obj)
{
        struct rpc_cred *cred = task->tk_msg.rpc_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;

        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:
                        break;
        }
out_decode:
        status = decode(rqstp, p, obj);
out:
        gss_put_ctx(ctx);
        dprintk("RPC: %4u gss_unwrap_resp returning %d\n", task->tk_pid,
                        status);
        return status;
}
  
static struct rpc_authops authgss_ops = {
        .owner          = THIS_MODULE,
        .au_flavor      = RPC_AUTH_GSS,
#ifdef RPC_DEBUG
        .au_name        = "RPCSEC_GSS",
#endif
        .create         = gss_create,
        .destroy        = gss_destroy,
        .lookup_cred    = gss_lookup_cred,
        .crcreate       = gss_create_cred
};

static struct rpc_credops gss_credops = {
        .cr_name        = "AUTH_GSS",
        .crdestroy      = gss_destroy_cred,
        .crmatch        = gss_match,
        .crmarshal      = gss_marshal,
        .crrefresh      = gss_refresh,
        .crvalidate     = gss_validate,
        .crwrap_req     = gss_wrap_req,
        .crunwrap_resp  = gss_unwrap_resp,
};

static struct rpc_pipe_ops gss_upcall_ops = {
        .upcall         = gss_pipe_upcall,
        .downcall       = gss_pipe_downcall,
        .destroy_msg    = gss_pipe_destroy_msg,
        .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;
        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);
}

MODULE_LICENSE("GPL");
module_init(init_rpcsec_gss)
module_exit(exit_rpcsec_gss)