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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.
 *
 * $Id$
 */


#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;

#ifdef RPC_DEBUG
# define RPCDBG_FACILITY      RPCDBG_AUTH
#endif

#define NFS_NGROUPS     16

#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        100

/* 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))

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;
      struct dentry *dentry;
};

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

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);
      struct gss_cl_ctx *old;

      old = gss_cred->gc_ctx;
      rcu_assign_pointer(gss_cred->gc_ctx, ctx);
      set_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
      clear_bit(RPCAUTH_CRED_NEW, &cred->cr_flags);
      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;

      rcu_read_lock();
      if (test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) && gss_cred->gc_ctx)
            res = 1;
      rcu_read_unlock();
      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 = kmemdup(p, len, GFP_KERNEL);
      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_KERNEL);
      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 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 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 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 inode *inode = gss_auth->dentry->d_inode;
      struct rpc_inode *rpci = RPC_I(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 gss_auth *gss_auth = gss_msg->auth;
      struct inode *inode = gss_auth->dentry->d_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_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;
      struct inode *inode = gss_msg->auth->dentry->d_inode;

      spin_lock(&inode->i_lock);
      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;
      gss_cred->gc_upcall = NULL;
      rpc_wake_up_status(&gss_msg->rpc_waitqueue, gss_msg->msg.errno);
      spin_unlock(&inode->i_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 = kzalloc(sizeof(*gss_msg), GFP_KERNEL);
      if (gss_msg != NULL) {
            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(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 = gss_auth->dentry->d_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 (IS_ERR(gss_msg)) {
            err = PTR_ERR(gss_msg);
            goto out;
      }
      spin_lock(&inode->i_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(&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 = gss_auth->dentry->d_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);
      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(&inode->i_lock);
            if (gss_msg->ctx != NULL || gss_msg->msg.errno < 0) {
                  break;
            }
            spin_unlock(&inode->i_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;
      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;
      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_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_KERNEL);
      if (!buf)
            goto out;

      clnt = RPC_I(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 = -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);
            gss_msg->msg.errno = (err == -EAGAIN) ? -EAGAIN : -EACCES;
            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 void
gss_pipe_release(struct inode *inode)
{
      struct rpc_inode *rpci = RPC_I(inode);
      struct gss_upcall_msg *gss_msg;

      spin_lock(&inode->i_lock);
      while (!list_empty(&rpci->in_downcall)) {

            gss_msg = list_entry(rpci->in_downcall.next,
                        struct gss_upcall_msg, list);
            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);
            spin_lock(&inode->i_lock);
      }
      spin_unlock(&inode->i_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) {
                  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;
      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",
                        __FUNCTION__, 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);

      gss_auth->dentry = rpc_mkpipe(clnt->cl_dentry, gss_auth->mech->gm_name,
                  clnt, &gss_upcall_ops, RPC_PIPE_WAIT_FOR_OPEN);
      if (IS_ERR(gss_auth->dentry)) {
            err = PTR_ERR(gss_auth->dentry);
            goto err_put_mech;
      }

      err = rpcauth_init_credcache(auth);
      if (err)
            goto err_unlink_pipe;

      return auth;
err_unlink_pipe:
      rpc_unlink(gss_auth->dentry);
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);
      gss_auth->dentry = NULL;
      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 ||
                  gss_cred->gc_ctx->gc_proc == RPC_GSS_PROC_DESTROY)
            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);
      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");

      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)
{
      struct gss_ctx *gc_gss_ctx;

      gc_gss_ctx = rcu_dereference(ctx->gc_gss_ctx);
      rcu_assign_pointer(ctx->gc_gss_ctx, NULL);
      call_rcu(&ctx->gc_rcu, gss_free_ctx_callback);
      if (gc_gss_ctx)
            gss_delete_sec_context(&gc_gss_ctx);
}

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_cred(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;

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

/*
 * 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_KERNEL)))
            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;
      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 the searchflags have set RPCAUTH_LOOKUP_NEW, then
       * we don't really care if the credential has expired or not,
       * since the caller should be prepared to reinitialise it.
       */
      if ((flags & RPCAUTH_LOOKUP_NEW) && test_bit(RPCAUTH_CRED_NEW, &rc->cr_flags))
            goto out;
      /* Don't match with creds that have expired. */
      if (gss_cred->gc_ctx && time_after(jiffies, gss_cred->gc_ctx->gc_expiry))
            return 0;
out:
      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_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);
      __be32            *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: %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;
}

/*
* 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;
}

/* 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_msg.rpc_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 inline int
gss_wrap_req_integ(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
            kxdrproc_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);

      status = rpc_call_xdrproc(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, &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:
      for (i--; i >= 0; i--) {
            __free_page(rqstp->rq_enc_pages[i]);
      }
out:
      return -EAGAIN;
}

static inline int
gss_wrap_req_priv(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
            kxdrproc_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);

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

      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: */
      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);
      /* RPC_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,
           kxdrproc_t encode, void *rqstp, __be32 *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: %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.
             */
            status = rpc_call_xdrproc(encode, rqstp, p, obj);
            goto out;
      }
      switch (gss_cred->gc_service) {
            case RPC_GSS_SVC_NONE:
                  status = rpc_call_xdrproc(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:
                  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_resp(struct rpc_task *task,
            kxdrproc_t decode, void *rqstp, __be32 *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);
      __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 = rpc_call_xdrproc(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,
#ifdef RPC_DEBUG
      .au_name    = "RPCSEC_GSS",
#endif
      .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,
      .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_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 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)

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