/*
 * Neil Brown <neilb@cse.unsw.edu.au>
 * J. Bruce Fields <bfields@umich.edu>
 * Andy Adamson <andros@umich.edu>
 * Dug Song <dugsong@monkey.org>
 *
 * RPCSEC_GSS server authentication.
 * This implements RPCSEC_GSS as defined in rfc2203 (rpcsec_gss) and rfc2078
 * (gssapi)
 *
 * The RPCSEC_GSS involves three stages:
 *  1/ context creation
 *  2/ data exchange
 *  3/ context destruction
 *
 * Context creation is handled largely by upcalls to user-space.
 *  In particular, GSS_Accept_sec_context is handled by an upcall
 * Data exchange is handled entirely within the kernel
 *  In particular, GSS_GetMIC, GSS_VerifyMIC, GSS_Seal, GSS_Unseal are in-kernel.
 * Context destruction is handled in-kernel
 *  GSS_Delete_sec_context is in-kernel
 *
 * Context creation is initiated by a RPCSEC_GSS_INIT request arriving.
 * The context handle and gss_token are used as a key into the rpcsec_init cache.
 * The content of this cache includes some of the outputs of GSS_Accept_sec_context,
 * being major_status, minor_status, context_handle, reply_token.
 * These are sent back to the client.
 * Sequence window management is handled by the kernel.  The window size if currently
 * a compile time constant.
 *
 * When user-space is happy that a context is established, it places an entry
 * in the rpcsec_context cache. The key for this cache is the context_handle.
 * The content includes:
 *   uid/gidlist - for determining access rights
 *   mechanism type
 *   mechanism specific information, such as a key
 *
 */

#include <linux/slab.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/pagemap.h>
#include <linux/user_namespace.h>

#include <linux/sunrpc/auth_gss.h>
#include <linux/sunrpc/gss_err.h>
#include <linux/sunrpc/svcauth.h>
#include <linux/sunrpc/svcauth_gss.h>
#include <linux/sunrpc/cache.h>
#include "gss_rpc_upcall.h"


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

/* The rpcsec_init cache is used for mapping RPCSEC_GSS_{,CONT_}INIT requests
 * into replies.
 *
 * Key is context handle (\x if empty) and gss_token.
 * Content is major_status minor_status (integers) context_handle, reply_token.
 *
 */

static int netobj_equal(struct xdr_netobj *a, struct xdr_netobj *b)
{
        return a->len == b->len && 0 == memcmp(a->data, b->data, a->len);
}

#define RSI_HASHBITS    6
#define RSI_HASHMAX     (1<<RSI_HASHBITS)

struct rsi {
        struct cache_head       h;
        struct xdr_netobj       in_handle, in_token;
        struct xdr_netobj       out_handle, out_token;
        int                     major_status, minor_status;
};

static struct rsi *rsi_update(struct cache_detail *cd, struct rsi *new, struct rsi *old);
static struct rsi *rsi_lookup(struct cache_detail *cd, struct rsi *item);

static void rsi_free(struct rsi *rsii)
{
        kfree(rsii->in_handle.data);
        kfree(rsii->in_token.data);
        kfree(rsii->out_handle.data);
        kfree(rsii->out_token.data);
}

static void rsi_put(struct kref *ref)
{
        struct rsi *rsii = container_of(ref, struct rsi, h.ref);
        rsi_free(rsii);
        kfree(rsii);
}

static inline int rsi_hash(struct rsi *item)
{
        return hash_mem(item->in_handle.data, item->in_handle.len, RSI_HASHBITS)
             ^ hash_mem(item->in_token.data, item->in_token.len, RSI_HASHBITS);
}

static int rsi_match(struct cache_head *a, struct cache_head *b)
{
        struct rsi *item = container_of(a, struct rsi, h);
        struct rsi *tmp = container_of(b, struct rsi, h);
        return netobj_equal(&item->in_handle, &tmp->in_handle) &&
               netobj_equal(&item->in_token, &tmp->in_token);
}

static int dup_to_netobj(struct xdr_netobj *dst, char *src, int len)
{
        dst->len = len;
        dst->data = (len ? kmemdup(src, len, GFP_KERNEL) : NULL);
        if (len && !dst->data)
                return -ENOMEM;
        return 0;
}

static inline int dup_netobj(struct xdr_netobj *dst, struct xdr_netobj *src)
{
        return dup_to_netobj(dst, src->data, src->len);
}

static void rsi_init(struct cache_head *cnew, struct cache_head *citem)
{
        struct rsi *new = container_of(cnew, struct rsi, h);
        struct rsi *item = container_of(citem, struct rsi, h);

        new->out_handle.data = NULL;
        new->out_handle.len = 0;
        new->out_token.data = NULL;
        new->out_token.len = 0;
        new->in_handle.len = item->in_handle.len;
        item->in_handle.len = 0;
        new->in_token.len = item->in_token.len;
        item->in_token.len = 0;
        new->in_handle.data = item->in_handle.data;
        item->in_handle.data = NULL;
        new->in_token.data = item->in_token.data;
        item->in_token.data = NULL;
}

static void update_rsi(struct cache_head *cnew, struct cache_head *citem)
{
        struct rsi *new = container_of(cnew, struct rsi, h);
        struct rsi *item = container_of(citem, struct rsi, h);

        BUG_ON(new->out_handle.data || new->out_token.data);
        new->out_handle.len = item->out_handle.len;
        item->out_handle.len = 0;
        new->out_token.len = item->out_token.len;
        item->out_token.len = 0;
        new->out_handle.data = item->out_handle.data;
        item->out_handle.data = NULL;
        new->out_token.data = item->out_token.data;
        item->out_token.data = NULL;

        new->major_status = item->major_status;
        new->minor_status = item->minor_status;
}

static struct cache_head *rsi_alloc(void)
{
        struct rsi *rsii = kmalloc(sizeof(*rsii), GFP_KERNEL);
        if (rsii)
                return &rsii->h;
        else
                return NULL;
}

static void rsi_request(struct cache_detail *cd,
                       struct cache_head *h,
                       char **bpp, int *blen)
{
        struct rsi *rsii = container_of(h, struct rsi, h);

        qword_addhex(bpp, blen, rsii->in_handle.data, rsii->in_handle.len);
        qword_addhex(bpp, blen, rsii->in_token.data, rsii->in_token.len);
        (*bpp)[-1] = '\n';
}

static int rsi_parse(struct cache_detail *cd,
                    char *mesg, int mlen)
{
        /* context token expiry major minor context token */
        char *buf = mesg;
        char *ep;
        int len;
        struct rsi rsii, *rsip = NULL;
        time_t expiry;
        int status = -EINVAL;

        memset(&rsii, 0, sizeof(rsii));
        /* handle */
        len = qword_get(&mesg, buf, mlen);
        if (len < 0)
                goto out;
        status = -ENOMEM;
        if (dup_to_netobj(&rsii.in_handle, buf, len))
                goto out;

        /* token */
        len = qword_get(&mesg, buf, mlen);
        status = -EINVAL;
        if (len < 0)
                goto out;
        status = -ENOMEM;
        if (dup_to_netobj(&rsii.in_token, buf, len))
                goto out;

        rsip = rsi_lookup(cd, &rsii);
        if (!rsip)
                goto out;

        rsii.h.flags = 0;
        /* expiry */
        expiry = get_expiry(&mesg);
        status = -EINVAL;
        if (expiry == 0)
                goto out;

        /* major/minor */
        len = qword_get(&mesg, buf, mlen);
        if (len <= 0)
                goto out;
        rsii.major_status = simple_strtoul(buf, &ep, 10);
        if (*ep)
                goto out;
        len = qword_get(&mesg, buf, mlen);
        if (len <= 0)
                goto out;
        rsii.minor_status = simple_strtoul(buf, &ep, 10);
        if (*ep)
                goto out;

        /* out_handle */
        len = qword_get(&mesg, buf, mlen);
        if (len < 0)
                goto out;
        status = -ENOMEM;
        if (dup_to_netobj(&rsii.out_handle, buf, len))
                goto out;

        /* out_token */
        len = qword_get(&mesg, buf, mlen);
        status = -EINVAL;
        if (len < 0)
                goto out;
        status = -ENOMEM;
        if (dup_to_netobj(&rsii.out_token, buf, len))
                goto out;
        rsii.h.expiry_time = expiry;
        rsip = rsi_update(cd, &rsii, rsip);
        status = 0;
out:
        rsi_free(&rsii);
        if (rsip)
                cache_put(&rsip->h, cd);
        else
                status = -ENOMEM;
        return status;
}

static struct cache_detail rsi_cache_template = {
        .owner          = THIS_MODULE,
        .hash_size      = RSI_HASHMAX,
        .name           = "auth.rpcsec.init",
        .cache_put      = rsi_put,
        .cache_request  = rsi_request,
        .cache_parse    = rsi_parse,
        .match          = rsi_match,
        .init           = rsi_init,
        .update         = update_rsi,
        .alloc          = rsi_alloc,
};

static struct rsi *rsi_lookup(struct cache_detail *cd, struct rsi *item)
{
        struct cache_head *ch;
        int hash = rsi_hash(item);

        ch = sunrpc_cache_lookup(cd, &item->h, hash);
        if (ch)
                return container_of(ch, struct rsi, h);
        else
                return NULL;
}

static struct rsi *rsi_update(struct cache_detail *cd, struct rsi *new, struct rsi *old)
{
        struct cache_head *ch;
        int hash = rsi_hash(new);

        ch = sunrpc_cache_update(cd, &new->h,
                                 &old->h, hash);
        if (ch)
                return container_of(ch, struct rsi, h);
        else
                return NULL;
}


/*
 * The rpcsec_context cache is used to store a context that is
 * used in data exchange.
 * The key is a context handle. The content is:
 *  uid, gidlist, mechanism, service-set, mech-specific-data
 */

#define RSC_HASHBITS    10
#define RSC_HASHMAX     (1<<RSC_HASHBITS)

#define GSS_SEQ_WIN     128

struct gss_svc_seq_data {
        /* highest seq number seen so far: */
        int                     sd_max;
        /* for i such that sd_max-GSS_SEQ_WIN < i <= sd_max, the i-th bit of
         * sd_win is nonzero iff sequence number i has been seen already: */
        unsigned long           sd_win[GSS_SEQ_WIN/BITS_PER_LONG];
        spinlock_t              sd_lock;
};

struct rsc {
        struct cache_head       h;
        struct xdr_netobj       handle;
        struct svc_cred         cred;
        struct gss_svc_seq_data seqdata;
        struct gss_ctx          *mechctx;
};

static struct rsc *rsc_update(struct cache_detail *cd, struct rsc *new, struct rsc *old);
static struct rsc *rsc_lookup(struct cache_detail *cd, struct rsc *item);

static void rsc_free(struct rsc *rsci)
{
        kfree(rsci->handle.data);
        if (rsci->mechctx)
                gss_delete_sec_context(&rsci->mechctx);
        free_svc_cred(&rsci->cred);
}

static void rsc_put(struct kref *ref)
{
        struct rsc *rsci = container_of(ref, struct rsc, h.ref);

        rsc_free(rsci);
        kfree(rsci);
}

static inline int
rsc_hash(struct rsc *rsci)
{
        return hash_mem(rsci->handle.data, rsci->handle.len, RSC_HASHBITS);
}

static int
rsc_match(struct cache_head *a, struct cache_head *b)
{
        struct rsc *new = container_of(a, struct rsc, h);
        struct rsc *tmp = container_of(b, struct rsc, h);

        return netobj_equal(&new->handle, &tmp->handle);
}

static void
rsc_init(struct cache_head *cnew, struct cache_head *ctmp)
{
        struct rsc *new = container_of(cnew, struct rsc, h);
        struct rsc *tmp = container_of(ctmp, struct rsc, h);

        new->handle.len = tmp->handle.len;
        tmp->handle.len = 0;
        new->handle.data = tmp->handle.data;
        tmp->handle.data = NULL;
        new->mechctx = NULL;
        init_svc_cred(&new->cred);
}

static void
update_rsc(struct cache_head *cnew, struct cache_head *ctmp)
{
        struct rsc *new = container_of(cnew, struct rsc, h);
        struct rsc *tmp = container_of(ctmp, struct rsc, h);

        new->mechctx = tmp->mechctx;
        tmp->mechctx = NULL;
        memset(&new->seqdata, 0, sizeof(new->seqdata));
        spin_lock_init(&new->seqdata.sd_lock);
        new->cred = tmp->cred;
        init_svc_cred(&tmp->cred);
}

static struct cache_head *
rsc_alloc(void)
{
        struct rsc *rsci = kmalloc(sizeof(*rsci), GFP_KERNEL);
        if (rsci)
                return &rsci->h;
        else
                return NULL;
}

static int rsc_parse(struct cache_detail *cd,
                     char *mesg, int mlen)
{
        /* contexthandle expiry [ uid gid N <n gids> mechname ...mechdata... ] */
        char *buf = mesg;
        int id;
        int len, rv;
        struct rsc rsci, *rscp = NULL;
        time_t expiry;
        int status = -EINVAL;
        struct gss_api_mech *gm = NULL;

        memset(&rsci, 0, sizeof(rsci));
        /* context handle */
        len = qword_get(&mesg, buf, mlen);
        if (len < 0) goto out;
        status = -ENOMEM;
        if (dup_to_netobj(&rsci.handle, buf, len))
                goto out;

        rsci.h.flags = 0;
        /* expiry */
        expiry = get_expiry(&mesg);
        status = -EINVAL;
        if (expiry == 0)
                goto out;

        rscp = rsc_lookup(cd, &rsci);
        if (!rscp)
                goto out;

        /* uid, or NEGATIVE */
        rv = get_int(&mesg, &id);
        if (rv == -EINVAL)
                goto out;
        if (rv == -ENOENT)
                set_bit(CACHE_NEGATIVE, &rsci.h.flags);
        else {
                int N, i;

                /*
                 * NOTE: we skip uid_valid()/gid_valid() checks here:
                 * instead, * -1 id's are later mapped to the
                 * (export-specific) anonymous id by nfsd_setuser.
                 *
                 * (But supplementary gid's get no such special
                 * treatment so are checked for validity here.)
                 */
                /* uid */
                rsci.cred.cr_uid = make_kuid(&init_user_ns, id);

                /* gid */
                if (get_int(&mesg, &id))
                        goto out;
                rsci.cred.cr_gid = make_kgid(&init_user_ns, id);

                /* number of additional gid's */
                if (get_int(&mesg, &N))
                        goto out;
                if (N < 0 || N > NGROUPS_MAX)
                        goto out;
                status = -ENOMEM;
                rsci.cred.cr_group_info = groups_alloc(N);
                if (rsci.cred.cr_group_info == NULL)
                        goto out;

                /* gid's */
                status = -EINVAL;
                for (i=0; i<N; i++) {
                        kgid_t kgid;
                        if (get_int(&mesg, &id))
                                goto out;
                        kgid = make_kgid(&init_user_ns, id);
                        if (!gid_valid(kgid))
                                goto out;
                        GROUP_AT(rsci.cred.cr_group_info, i) = kgid;
                }

                /* mech name */
                len = qword_get(&mesg, buf, mlen);
                if (len < 0)
                        goto out;
                gm = rsci.cred.cr_gss_mech = gss_mech_get_by_name(buf);
                status = -EOPNOTSUPP;
                if (!gm)
                        goto out;

                status = -EINVAL;
                /* mech-specific data: */
                len = qword_get(&mesg, buf, mlen);
                if (len < 0)
                        goto out;
                status = gss_import_sec_context(buf, len, gm, &rsci.mechctx,
                                                NULL, GFP_KERNEL);
                if (status)
                        goto out;

                /* get client name */
                len = qword_get(&mesg, buf, mlen);
                if (len > 0) {
                        rsci.cred.cr_principal = kstrdup(buf, GFP_KERNEL);
                        if (!rsci.cred.cr_principal) {
                                status = -ENOMEM;
                                goto out;
                        }
                }

        }
        rsci.h.expiry_time = expiry;
        rscp = rsc_update(cd, &rsci, rscp);
        status = 0;
out:
        rsc_free(&rsci);
        if (rscp)
                cache_put(&rscp->h, cd);
        else
                status = -ENOMEM;
        return status;
}

static struct cache_detail rsc_cache_template = {
        .owner          = THIS_MODULE,
        .hash_size      = RSC_HASHMAX,
        .name           = "auth.rpcsec.context",
        .cache_put      = rsc_put,
        .cache_parse    = rsc_parse,
        .match          = rsc_match,
        .init           = rsc_init,
        .update         = update_rsc,
        .alloc          = rsc_alloc,
};

static struct rsc *rsc_lookup(struct cache_detail *cd, struct rsc *item)
{
        struct cache_head *ch;
        int hash = rsc_hash(item);

        ch = sunrpc_cache_lookup(cd, &item->h, hash);
        if (ch)
                return container_of(ch, struct rsc, h);
        else
                return NULL;
}

static struct rsc *rsc_update(struct cache_detail *cd, struct rsc *new, struct rsc *old)
{
        struct cache_head *ch;
        int hash = rsc_hash(new);

        ch = sunrpc_cache_update(cd, &new->h,
                                 &old->h, hash);
        if (ch)
                return container_of(ch, struct rsc, h);
        else
                return NULL;
}


static struct rsc *
gss_svc_searchbyctx(struct cache_detail *cd, struct xdr_netobj *handle)
{
        struct rsc rsci;
        struct rsc *found;

        memset(&rsci, 0, sizeof(rsci));
        if (dup_to_netobj(&rsci.handle, handle->data, handle->len))
                return NULL;
        found = rsc_lookup(cd, &rsci);
        rsc_free(&rsci);
        if (!found)
                return NULL;
        if (cache_check(cd, &found->h, NULL))
                return NULL;
        return found;
}

/* Implements sequence number algorithm as specified in RFC 2203. */
static int
gss_check_seq_num(struct rsc *rsci, int seq_num)
{
        struct gss_svc_seq_data *sd = &rsci->seqdata;

        spin_lock(&sd->sd_lock);
        if (seq_num > sd->sd_max) {
                if (seq_num >= sd->sd_max + GSS_SEQ_WIN) {
                        memset(sd->sd_win,0,sizeof(sd->sd_win));
                        sd->sd_max = seq_num;
                } else while (sd->sd_max < seq_num) {
                        sd->sd_max++;
                        __clear_bit(sd->sd_max % GSS_SEQ_WIN, sd->sd_win);
                }
                __set_bit(seq_num % GSS_SEQ_WIN, sd->sd_win);
                goto ok;
        } else if (seq_num <= sd->sd_max - GSS_SEQ_WIN) {
                goto drop;
        }
        /* sd_max - GSS_SEQ_WIN < seq_num <= sd_max */
        if (__test_and_set_bit(seq_num % GSS_SEQ_WIN, sd->sd_win))
                goto drop;
ok:
        spin_unlock(&sd->sd_lock);
        return 1;
drop:
        spin_unlock(&sd->sd_lock);
        return 0;
}

static inline u32 round_up_to_quad(u32 i)
{
        return (i + 3 ) & ~3;
}

static inline int
svc_safe_getnetobj(struct kvec *argv, struct xdr_netobj *o)
{
        int l;

        if (argv->iov_len < 4)
                return -1;
        o->len = svc_getnl(argv);
        l = round_up_to_quad(o->len);
        if (argv->iov_len < l)
                return -1;
        o->data = argv->iov_base;
        argv->iov_base += l;
        argv->iov_len -= l;
        return 0;
}

static inline int
svc_safe_putnetobj(struct kvec *resv, struct xdr_netobj *o)
{
        u8 *p;

        if (resv->iov_len + 4 > PAGE_SIZE)
                return -1;
        svc_putnl(resv, o->len);
        p = resv->iov_base + resv->iov_len;
        resv->iov_len += round_up_to_quad(o->len);
        if (resv->iov_len > PAGE_SIZE)
                return -1;
        memcpy(p, o->data, o->len);
        memset(p + o->len, 0, round_up_to_quad(o->len) - o->len);
        return 0;
}

/*
 * Verify the checksum on the header and return SVC_OK on success.
 * Otherwise, return SVC_DROP (in the case of a bad sequence number)
 * or return SVC_DENIED and indicate error in authp.
 */
static int
gss_verify_header(struct svc_rqst *rqstp, struct rsc *rsci,
                  __be32 *rpcstart, struct rpc_gss_wire_cred *gc, __be32 *authp)
{
        struct gss_ctx          *ctx_id = rsci->mechctx;
        struct xdr_buf          rpchdr;
        struct xdr_netobj       checksum;
        u32                     flavor = 0;
        struct kvec             *argv = &rqstp->rq_arg.head[0];
        struct kvec             iov;

        /* data to compute the checksum over: */
        iov.iov_base = rpcstart;
        iov.iov_len = (u8 *)argv->iov_base - (u8 *)rpcstart;
        xdr_buf_from_iov(&iov, &rpchdr);

        *authp = rpc_autherr_badverf;
        if (argv->iov_len < 4)
                return SVC_DENIED;
        flavor = svc_getnl(argv);
        if (flavor != RPC_AUTH_GSS)
                return SVC_DENIED;
        if (svc_safe_getnetobj(argv, &checksum))
                return SVC_DENIED;

        if (rqstp->rq_deferred) /* skip verification of revisited request */
                return SVC_OK;
        if (gss_verify_mic(ctx_id, &rpchdr, &checksum) != GSS_S_COMPLETE) {
                *authp = rpcsec_gsserr_credproblem;
                return SVC_DENIED;
        }

        if (gc->gc_seq > MAXSEQ) {
                dprintk("RPC:       svcauth_gss: discarding request with "
                                "large sequence number %d\n", gc->gc_seq);
                *authp = rpcsec_gsserr_ctxproblem;
                return SVC_DENIED;
        }
        if (!gss_check_seq_num(rsci, gc->gc_seq)) {
                dprintk("RPC:       svcauth_gss: discarding request with "
                                "old sequence number %d\n", gc->gc_seq);
                return SVC_DROP;
        }
        return SVC_OK;
}

static int
gss_write_null_verf(struct svc_rqst *rqstp)
{
        __be32     *p;

        svc_putnl(rqstp->rq_res.head, RPC_AUTH_NULL);
        p = rqstp->rq_res.head->iov_base + rqstp->rq_res.head->iov_len;
        /* don't really need to check if head->iov_len > PAGE_SIZE ... */
        *p++ = 0;
        if (!xdr_ressize_check(rqstp, p))
                return -1;
        return 0;
}

static int
gss_write_verf(struct svc_rqst *rqstp, struct gss_ctx *ctx_id, u32 seq)
{
        __be32                  xdr_seq;
        u32                     maj_stat;
        struct xdr_buf          verf_data;
        struct xdr_netobj       mic;
        __be32                  *p;
        struct kvec             iov;

        svc_putnl(rqstp->rq_res.head, RPC_AUTH_GSS);
        xdr_seq = htonl(seq);

        iov.iov_base = &xdr_seq;
        iov.iov_len = sizeof(xdr_seq);
        xdr_buf_from_iov(&iov, &verf_data);
        p = rqstp->rq_res.head->iov_base + rqstp->rq_res.head->iov_len;
        mic.data = (u8 *)(p + 1);
        maj_stat = gss_get_mic(ctx_id, &verf_data, &mic);
        if (maj_stat != GSS_S_COMPLETE)
                return -1;
        *p++ = htonl(mic.len);
        memset((u8 *)p + mic.len, 0, round_up_to_quad(mic.len) - mic.len);
        p += XDR_QUADLEN(mic.len);
        if (!xdr_ressize_check(rqstp, p))
                return -1;
        return 0;
}

struct gss_domain {
        struct auth_domain      h;
        u32                     pseudoflavor;
};

static struct auth_domain *
find_gss_auth_domain(struct gss_ctx *ctx, u32 svc)
{
        char *name;

        name = gss_service_to_auth_domain_name(ctx->mech_type, svc);
        if (!name)
                return NULL;
        return auth_domain_find(name);
}

static struct auth_ops svcauthops_gss;

u32 svcauth_gss_flavor(struct auth_domain *dom)
{
        struct gss_domain *gd = container_of(dom, struct gss_domain, h);

        return gd->pseudoflavor;
}

EXPORT_SYMBOL_GPL(svcauth_gss_flavor);

int
svcauth_gss_register_pseudoflavor(u32 pseudoflavor, char * name)
{
        struct gss_domain       *new;
        struct auth_domain      *test;
        int                     stat = -ENOMEM;

        new = kmalloc(sizeof(*new), GFP_KERNEL);
        if (!new)
                goto out;
        kref_init(&new->h.ref);
        new->h.name = kstrdup(name, GFP_KERNEL);
        if (!new->h.name)
                goto out_free_dom;
        new->h.flavour = &svcauthops_gss;
        new->pseudoflavor = pseudoflavor;

        stat = 0;
        test = auth_domain_lookup(name, &new->h);
        if (test != &new->h) { /* Duplicate registration */
                auth_domain_put(test);
                kfree(new->h.name);
                goto out_free_dom;
        }
        return 0;

out_free_dom:
        kfree(new);
out:
        return stat;
}

EXPORT_SYMBOL_GPL(svcauth_gss_register_pseudoflavor);

static inline int
read_u32_from_xdr_buf(struct xdr_buf *buf, int base, u32 *obj)
{
        __be32  raw;
        int     status;

        status = read_bytes_from_xdr_buf(buf, base, &raw, sizeof(*obj));
        if (status)
                return status;
        *obj = ntohl(raw);
        return 0;
}

/* It would be nice if this bit of code could be shared with the client.
 * Obstacles:
 *      The client shouldn't malloc(), would have to pass in own memory.
 *      The server uses base of head iovec as read pointer, while the
 *      client uses separate pointer. */
static int
unwrap_integ_data(struct svc_rqst *rqstp, struct xdr_buf *buf, u32 seq, struct gss_ctx *ctx)
{
        int stat = -EINVAL;
        u32 integ_len, maj_stat;
        struct xdr_netobj mic;
        struct xdr_buf integ_buf;

        /* Did we already verify the signature on the original pass through? */
        if (rqstp->rq_deferred)
                return 0;

        integ_len = svc_getnl(&buf->head[0]);
        if (integ_len & 3)
                return stat;
        if (integ_len > buf->len)
                return stat;
        if (xdr_buf_subsegment(buf, &integ_buf, 0, integ_len))
                BUG();
        /* copy out mic... */
        if (read_u32_from_xdr_buf(buf, integ_len, &mic.len))
                BUG();
        if (mic.len > RPC_MAX_AUTH_SIZE)
                return stat;
        mic.data = kmalloc(mic.len, GFP_KERNEL);
        if (!mic.data)
                return stat;
        if (read_bytes_from_xdr_buf(buf, integ_len + 4, mic.data, mic.len))
                goto out;
        maj_stat = gss_verify_mic(ctx, &integ_buf, &mic);
        if (maj_stat != GSS_S_COMPLETE)
                goto out;
        if (svc_getnl(&buf->head[0]) != seq)
                goto out;
        /* trim off the mic at the end before returning */
        xdr_buf_trim(buf, mic.len + 4);
        stat = 0;
out:
        kfree(mic.data);
        return stat;
}

static inline int
total_buf_len(struct xdr_buf *buf)
{
        return buf->head[0].iov_len + buf->page_len + buf->tail[0].iov_len;
}

static void
fix_priv_head(struct xdr_buf *buf, int pad)
{
        if (buf->page_len == 0) {
                /* We need to adjust head and buf->len in tandem in this
                 * case to make svc_defer() work--it finds the original
                 * buffer start using buf->len - buf->head[0].iov_len. */
                buf->head[0].iov_len -= pad;
        }
}

static int
unwrap_priv_data(struct svc_rqst *rqstp, struct xdr_buf *buf, u32 seq, struct gss_ctx *ctx)
{
        u32 priv_len, maj_stat;
        int pad, saved_len, remaining_len, offset;

        clear_bit(RQ_SPLICE_OK, &rqstp->rq_flags);

        priv_len = svc_getnl(&buf->head[0]);
        if (rqstp->rq_deferred) {
                /* Already decrypted last time through! The sequence number
                 * check at out_seq is unnecessary but harmless: */
                goto out_seq;
        }
        /* buf->len is the number of bytes from the original start of the
         * request to the end, where head[0].iov_len is just the bytes
         * not yet read from the head, so these two values are different: */
        remaining_len = total_buf_len(buf);
        if (priv_len > remaining_len)
                return -EINVAL;
        pad = remaining_len - priv_len;
        buf->len -= pad;
        fix_priv_head(buf, pad);

        /* Maybe it would be better to give gss_unwrap a length parameter: */
        saved_len = buf->len;
        buf->len = priv_len;
        maj_stat = gss_unwrap(ctx, 0, buf);
        pad = priv_len - buf->len;
        buf->len = saved_len;
        buf->len -= pad;
        /* The upper layers assume the buffer is aligned on 4-byte boundaries.
         * In the krb5p case, at least, the data ends up offset, so we need to
         * move it around. */
        /* XXX: This is very inefficient.  It would be better to either do
         * this while we encrypt, or maybe in the receive code, if we can peak
         * ahead and work out the service and mechanism there. */
        offset = buf->head[0].iov_len % 4;
        if (offset) {
                buf->buflen = RPCSVC_MAXPAYLOAD;
                xdr_shift_buf(buf, offset);
                fix_priv_head(buf, pad);
        }
        if (maj_stat != GSS_S_COMPLETE)
                return -EINVAL;
out_seq:
        if (svc_getnl(&buf->head[0]) != seq)
                return -EINVAL;
        return 0;
}

struct gss_svc_data {
        /* decoded gss client cred: */
        struct rpc_gss_wire_cred        clcred;
        /* save a pointer to the beginning of the encoded verifier,
         * for use in encryption/checksumming in svcauth_gss_release: */
        __be32                          *verf_start;
        struct rsc                      *rsci;
};

static int
svcauth_gss_set_client(struct svc_rqst *rqstp)
{
        struct gss_svc_data *svcdata = rqstp->rq_auth_data;
        struct rsc *rsci = svcdata->rsci;
        struct rpc_gss_wire_cred *gc = &svcdata->clcred;
        int stat;

        /*
         * A gss export can be specified either by:
         *      export  *(sec=krb5,rw)
         * or by
         *      export gss/krb5(rw)
         * The latter is deprecated; but for backwards compatibility reasons
         * the nfsd code will still fall back on trying it if the former
         * doesn't work; so we try to make both available to nfsd, below.
         */
        rqstp->rq_gssclient = find_gss_auth_domain(rsci->mechctx, gc->gc_svc);
        if (rqstp->rq_gssclient == NULL)
                return SVC_DENIED;
        stat = svcauth_unix_set_client(rqstp);
        if (stat == SVC_DROP || stat == SVC_CLOSE)
                return stat;
        return SVC_OK;
}

static inline int
gss_write_init_verf(struct cache_detail *cd, struct svc_rqst *rqstp,
                struct xdr_netobj *out_handle, int *major_status)
{
        struct rsc *rsci;
        int        rc;

        if (*major_status != GSS_S_COMPLETE)
                return gss_write_null_verf(rqstp);
        rsci = gss_svc_searchbyctx(cd, out_handle);
        if (rsci == NULL) {
                *major_status = GSS_S_NO_CONTEXT;
                return gss_write_null_verf(rqstp);
        }
        rc = gss_write_verf(rqstp, rsci->mechctx, GSS_SEQ_WIN);
        cache_put(&rsci->h, cd);
        return rc;
}

static inline int
gss_read_common_verf(struct rpc_gss_wire_cred *gc,
                     struct kvec *argv, __be32 *authp,
                     struct xdr_netobj *in_handle)
{
        /* Read the verifier; should be NULL: */
        *authp = rpc_autherr_badverf;
        if (argv->iov_len < 2 * 4)
                return SVC_DENIED;
        if (svc_getnl(argv) != RPC_AUTH_NULL)
                return SVC_DENIED;

        if (svc_getnl(argv) != 0)
                return SVC_DENIED;
        /* Martial context handle and token for upcall: */
        *authp = rpc_autherr_badcred;
        if (gc->gc_proc == RPC_GSS_PROC_INIT && gc->gc_ctx.len != 0)
                return SVC_DENIED;
        if (dup_netobj(in_handle, &gc->gc_ctx))
                return SVC_CLOSE;
        *authp = rpc_autherr_badverf;

        return 0;
}

static inline int
gss_read_verf(struct rpc_gss_wire_cred *gc,
              struct kvec *argv, __be32 *authp,
              struct xdr_netobj *in_handle,
              struct xdr_netobj *in_token)
{
        struct xdr_netobj tmpobj;
        int res;

        res = gss_read_common_verf(gc, argv, authp, in_handle);
        if (res)
                return res;

        if (svc_safe_getnetobj(argv, &tmpobj)) {
                kfree(in_handle->data);
                return SVC_DENIED;
        }
        if (dup_netobj(in_token, &tmpobj)) {
                kfree(in_handle->data);
                return SVC_CLOSE;
        }

        return 0;
}

/* Ok this is really heavily depending on a set of semantics in
 * how rqstp is set up by svc_recv and pages laid down by the
 * server when reading a request. We are basically guaranteed that
 * the token lays all down linearly across a set of pages, starting
 * at iov_base in rq_arg.head[0] which happens to be the first of a
 * set of pages stored in rq_pages[].
 * rq_arg.head[0].iov_base will provide us the page_base to pass
 * to the upcall.
 */
static inline int
gss_read_proxy_verf(struct svc_rqst *rqstp,
                    struct rpc_gss_wire_cred *gc, __be32 *authp,
                    struct xdr_netobj *in_handle,
                    struct gssp_in_token *in_token)
{
        struct kvec *argv = &rqstp->rq_arg.head[0];
        u32 inlen;
        int res;

        res = gss_read_common_verf(gc, argv, authp, in_handle);
        if (res)
                return res;

        inlen = svc_getnl(argv);
        if (inlen > (argv->iov_len + rqstp->rq_arg.page_len))
                return SVC_DENIED;

        in_token->pages = rqstp->rq_pages;
        in_token->page_base = (ulong)argv->iov_base & ~PAGE_MASK;
        in_token->page_len = inlen;

        return 0;
}

static inline int
gss_write_resv(struct kvec *resv, size_t size_limit,
               struct xdr_netobj *out_handle, struct xdr_netobj *out_token,
               int major_status, int minor_status)
{
        if (resv->iov_len + 4 > size_limit)
                return -1;
        svc_putnl(resv, RPC_SUCCESS);
        if (svc_safe_putnetobj(resv, out_handle))
                return -1;
        if (resv->iov_len + 3 * 4 > size_limit)
                return -1;
        svc_putnl(resv, major_status);
        svc_putnl(resv, minor_status);
        svc_putnl(resv, GSS_SEQ_WIN);
        if (svc_safe_putnetobj(resv, out_token))
                return -1;
        return 0;
}

/*
 * Having read the cred already and found we're in the context
 * initiation case, read the verifier and initiate (or check the results
 * of) upcalls to userspace for help with context initiation.  If
 * the upcall results are available, write the verifier and result.
 * Otherwise, drop the request pending an answer to the upcall.
 */
static int svcauth_gss_legacy_init(struct svc_rqst *rqstp,
                        struct rpc_gss_wire_cred *gc, __be32 *authp)
{
        struct kvec *argv = &rqstp->rq_arg.head[0];
        struct kvec *resv = &rqstp->rq_res.head[0];
        struct rsi *rsip, rsikey;
        int ret;
        struct sunrpc_net *sn = net_generic(rqstp->rq_xprt->xpt_net, sunrpc_net_id);

        memset(&rsikey, 0, sizeof(rsikey));
        ret = gss_read_verf(gc, argv, authp,
                            &rsikey.in_handle, &rsikey.in_token);
        if (ret)
                return ret;

        /* Perform upcall, or find upcall result: */
        rsip = rsi_lookup(sn->rsi_cache, &rsikey);
        rsi_free(&rsikey);
        if (!rsip)
                return SVC_CLOSE;
        if (cache_check(sn->rsi_cache, &rsip->h, &rqstp->rq_chandle) < 0)
                /* No upcall result: */
                return SVC_CLOSE;

        ret = SVC_CLOSE;
        /* Got an answer to the upcall; use it: */
        if (gss_write_init_verf(sn->rsc_cache, rqstp,
                                &rsip->out_handle, &rsip->major_status))
                goto out;
        if (gss_write_resv(resv, PAGE_SIZE,
                           &rsip->out_handle, &rsip->out_token,
                           rsip->major_status, rsip->minor_status))
                goto out;

        ret = SVC_COMPLETE;
out:
        cache_put(&rsip->h, sn->rsi_cache);
        return ret;
}

static int gss_proxy_save_rsc(struct cache_detail *cd,
                                struct gssp_upcall_data *ud,
                                uint64_t *handle)
{
        struct rsc rsci, *rscp = NULL;
        static atomic64_t ctxhctr;
        long long ctxh;
        struct gss_api_mech *gm = NULL;
        time_t expiry;
        int status = -EINVAL;

        memset(&rsci, 0, sizeof(rsci));
        /* context handle */
        status = -ENOMEM;
        /* the handle needs to be just a unique id,
         * use a static counter */
        ctxh = atomic64_inc_return(&ctxhctr);

        /* make a copy for the caller */
        *handle = ctxh;

        /* make a copy for the rsc cache */
        if (dup_to_netobj(&rsci.handle, (char *)handle, sizeof(uint64_t)))
                goto out;
        rscp = rsc_lookup(cd, &rsci);
        if (!rscp)
                goto out;

        /* creds */
        if (!ud->found_creds) {
                /* userspace seem buggy, we should always get at least a
                 * mapping to nobody */
                dprintk("RPC:       No creds found!\n");
                goto out;
        } else {

                /* steal creds */
                rsci.cred = ud->creds;
                memset(&ud->creds, 0, sizeof(struct svc_cred));

                status = -EOPNOTSUPP;
                /* get mech handle from OID */
                gm = gss_mech_get_by_OID(&ud->mech_oid);
                if (!gm)
                        goto out;
                rsci.cred.cr_gss_mech = gm;

                status = -EINVAL;
                /* mech-specific data: */
                status = gss_import_sec_context(ud->out_handle.data,
                                                ud->out_handle.len,
                                                gm, &rsci.mechctx,
                                                &expiry, GFP_KERNEL);
                if (status)
                        goto out;
        }

        rsci.h.expiry_time = expiry;
        rscp = rsc_update(cd, &rsci, rscp);
        status = 0;
out:
        rsc_free(&rsci);
        if (rscp)
                cache_put(&rscp->h, cd);
        else
                status = -ENOMEM;
        return status;
}

static int svcauth_gss_proxy_init(struct svc_rqst *rqstp,
                        struct rpc_gss_wire_cred *gc, __be32 *authp)
{
        struct kvec *resv = &rqstp->rq_res.head[0];
        struct xdr_netobj cli_handle;
        struct gssp_upcall_data ud;
        uint64_t handle;
        int status;
        int ret;
        struct net *net = rqstp->rq_xprt->xpt_net;
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);

        memset(&ud, 0, sizeof(ud));
        ret = gss_read_proxy_verf(rqstp, gc, authp,
                                  &ud.in_handle, &ud.in_token);
        if (ret)
                return ret;

        ret = SVC_CLOSE;

        /* Perform synchronous upcall to gss-proxy */
        status = gssp_accept_sec_context_upcall(net, &ud);
        if (status)
                goto out;

        dprintk("RPC:       svcauth_gss: gss major status = %d\n",
                        ud.major_status);

        switch (ud.major_status) {
        case GSS_S_CONTINUE_NEEDED:
                cli_handle = ud.out_handle;
                break;
        case GSS_S_COMPLETE:
                status = gss_proxy_save_rsc(sn->rsc_cache, &ud, &handle);
                if (status)
                        goto out;
                cli_handle.data = (u8 *)&handle;
                cli_handle.len = sizeof(handle);
                break;
        default:
                ret = SVC_CLOSE;
                goto out;
        }

        /* Got an answer to the upcall; use it: */
        if (gss_write_init_verf(sn->rsc_cache, rqstp,
                                &cli_handle, &ud.major_status))
                goto out;
        if (gss_write_resv(resv, PAGE_SIZE,
                           &cli_handle, &ud.out_token,
                           ud.major_status, ud.minor_status))
                goto out;

        ret = SVC_COMPLETE;
out:
        gssp_free_upcall_data(&ud);
        return ret;
}

/*
 * Try to set the sn->use_gss_proxy variable to a new value. We only allow
 * it to be changed if it's currently undefined (-1). If it's any other value
 * then return -EBUSY unless the type wouldn't have changed anyway.
 */
static int set_gss_proxy(struct net *net, int type)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        int ret;

        WARN_ON_ONCE(type != 0 && type != 1);
        ret = cmpxchg(&sn->use_gss_proxy, -1, type);
        if (ret != -1 && ret != type)
                return -EBUSY;
        return 0;
}

static bool use_gss_proxy(struct net *net)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);

        /* If use_gss_proxy is still undefined, then try to disable it */
        if (sn->use_gss_proxy == -1)
                set_gss_proxy(net, 0);
        return sn->use_gss_proxy;
}

#ifdef CONFIG_PROC_FS

static ssize_t write_gssp(struct file *file, const char __user *buf,
                         size_t count, loff_t *ppos)
{
        struct net *net = PDE_DATA(file_inode(file));
        char tbuf[20];
        unsigned long i;
        int res;

        if (*ppos || count > sizeof(tbuf)-1)
                return -EINVAL;
        if (copy_from_user(tbuf, buf, count))
                return -EFAULT;

        tbuf[count] = 0;
        res = kstrtoul(tbuf, 0, &i);
        if (res)
                return res;
        if (i != 1)
                return -EINVAL;
        res = set_gssp_clnt(net);
        if (res)
                return res;
        res = set_gss_proxy(net, 1);
        if (res)
                return res;
        return count;
}

static ssize_t read_gssp(struct file *file, char __user *buf,
                         size_t count, loff_t *ppos)
{
        struct net *net = PDE_DATA(file_inode(file));
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        unsigned long p = *ppos;
        char tbuf[10];
        size_t len;

        snprintf(tbuf, sizeof(tbuf), "%d\n", sn->use_gss_proxy);
        len = strlen(tbuf);
        if (p >= len)
                return 0;
        len -= p;
        if (len > count)
                len = count;
        if (copy_to_user(buf, (void *)(tbuf+p), len))
                return -EFAULT;
        *ppos += len;
        return len;
}

static const struct file_operations use_gss_proxy_ops = {
        .open = nonseekable_open,
        .write = write_gssp,
        .read = read_gssp,
};

static int create_use_gss_proxy_proc_entry(struct net *net)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        struct proc_dir_entry **p = &sn->use_gssp_proc;

        sn->use_gss_proxy = -1;
        *p = proc_create_data("use-gss-proxy", S_IFREG|S_IRUSR|S_IWUSR,
                              sn->proc_net_rpc,
                              &use_gss_proxy_ops, net);
        if (!*p)
                return -ENOMEM;
        init_gssp_clnt(sn);
        return 0;
}

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

        if (sn->use_gssp_proc) {
                remove_proc_entry("use-gss-proxy", sn->proc_net_rpc); 
                clear_gssp_clnt(sn);
        }
}
#else /* CONFIG_PROC_FS */

static int create_use_gss_proxy_proc_entry(struct net *net)
{
        return 0;
}

static void destroy_use_gss_proxy_proc_entry(struct net *net) {}

#endif /* CONFIG_PROC_FS */

/*
 * Accept an rpcsec packet.
 * If context establishment, punt to user space
 * If data exchange, verify/decrypt
 * If context destruction, handle here
 * In the context establishment and destruction case we encode
 * response here and return SVC_COMPLETE.
 */
static int
svcauth_gss_accept(struct svc_rqst *rqstp, __be32 *authp)
{
        struct kvec     *argv = &rqstp->rq_arg.head[0];
        struct kvec     *resv = &rqstp->rq_res.head[0];
        u32             crlen;
        struct gss_svc_data *svcdata = rqstp->rq_auth_data;
        struct rpc_gss_wire_cred *gc;
        struct rsc      *rsci = NULL;
        __be32          *rpcstart;
        __be32          *reject_stat = resv->iov_base + resv->iov_len;
        int             ret;
        struct sunrpc_net *sn = net_generic(rqstp->rq_xprt->xpt_net, sunrpc_net_id);

        dprintk("RPC:       svcauth_gss: argv->iov_len = %zd\n",
                        argv->iov_len);

        *authp = rpc_autherr_badcred;
        if (!svcdata)
                svcdata = kmalloc(sizeof(*svcdata), GFP_KERNEL);
        if (!svcdata)
                goto auth_err;
        rqstp->rq_auth_data = svcdata;
        svcdata->verf_start = NULL;
        svcdata->rsci = NULL;
        gc = &svcdata->clcred;

        /* start of rpc packet is 7 u32's back from here:
         * xid direction rpcversion prog vers proc flavour
         */
        rpcstart = argv->iov_base;
        rpcstart -= 7;

        /* credential is:
         *   version(==1), proc(0,1,2,3), seq, service (1,2,3), handle
         * at least 5 u32s, and is preceded by length, so that makes 6.
         */

        if (argv->iov_len < 5 * 4)
                goto auth_err;
        crlen = svc_getnl(argv);
        if (svc_getnl(argv) != RPC_GSS_VERSION)
                goto auth_err;
        gc->gc_proc = svc_getnl(argv);
        gc->gc_seq = svc_getnl(argv);
        gc->gc_svc = svc_getnl(argv);
        if (svc_safe_getnetobj(argv, &gc->gc_ctx))
                goto auth_err;
        if (crlen != round_up_to_quad(gc->gc_ctx.len) + 5 * 4)
                goto auth_err;

        if ((gc->gc_proc != RPC_GSS_PROC_DATA) && (rqstp->rq_proc != 0))
                goto auth_err;

        *authp = rpc_autherr_badverf;
        switch (gc->gc_proc) {
        case RPC_GSS_PROC_INIT:
        case RPC_GSS_PROC_CONTINUE_INIT:
                if (use_gss_proxy(SVC_NET(rqstp)))
                        return svcauth_gss_proxy_init(rqstp, gc, authp);
                else
                        return svcauth_gss_legacy_init(rqstp, gc, authp);
        case RPC_GSS_PROC_DATA:
        case RPC_GSS_PROC_DESTROY:
                /* Look up the context, and check the verifier: */
                *authp = rpcsec_gsserr_credproblem;
                rsci = gss_svc_searchbyctx(sn->rsc_cache, &gc->gc_ctx);
                if (!rsci)
                        goto auth_err;
                switch (gss_verify_header(rqstp, rsci, rpcstart, gc, authp)) {
                case SVC_OK:
                        break;
                case SVC_DENIED:
                        goto auth_err;
                case SVC_DROP:
                        goto drop;
                }
                break;
        default:
                *authp = rpc_autherr_rejectedcred;
                goto auth_err;
        }

        /* now act upon the command: */
        switch (gc->gc_proc) {
        case RPC_GSS_PROC_DESTROY:
                if (gss_write_verf(rqstp, rsci->mechctx, gc->gc_seq))
                        goto auth_err;
                rsci->h.expiry_time = get_seconds();
                set_bit(CACHE_NEGATIVE, &rsci->h.flags);
                if (resv->iov_len + 4 > PAGE_SIZE)
                        goto drop;
                svc_putnl(resv, RPC_SUCCESS);
                goto complete;
        case RPC_GSS_PROC_DATA:
                *authp = rpcsec_gsserr_ctxproblem;
                svcdata->verf_start = resv->iov_base + resv->iov_len;
                if (gss_write_verf(rqstp, rsci->mechctx, gc->gc_seq))
                        goto auth_err;
                rqstp->rq_cred = rsci->cred;
                get_group_info(rsci->cred.cr_group_info);
                *authp = rpc_autherr_badcred;
                switch (gc->gc_svc) {
                case RPC_GSS_SVC_NONE:
                        break;
                case RPC_GSS_SVC_INTEGRITY:
                        /* placeholders for length and seq. number: */
                        svc_putnl(resv, 0);
                        svc_putnl(resv, 0);
                        if (unwrap_integ_data(rqstp, &rqstp->rq_arg,
                                        gc->gc_seq, rsci->mechctx))
                                goto garbage_args;
                        rqstp->rq_auth_slack = RPC_MAX_AUTH_SIZE;
                        break;
                case RPC_GSS_SVC_PRIVACY:
                        /* placeholders for length and seq. number: */
                        svc_putnl(resv, 0);
                        svc_putnl(resv, 0);
                        if (unwrap_priv_data(rqstp, &rqstp->rq_arg,
                                        gc->gc_seq, rsci->mechctx))
                                goto garbage_args;
                        rqstp->rq_auth_slack = RPC_MAX_AUTH_SIZE * 2;
                        break;
                default:
                        goto auth_err;
                }
                svcdata->rsci = rsci;
                cache_get(&rsci->h);
                rqstp->rq_cred.cr_flavor = gss_svc_to_pseudoflavor(
                                        rsci->mechctx->mech_type,
                                        GSS_C_QOP_DEFAULT,
                                        gc->gc_svc);
                ret = SVC_OK;
                goto out;
        }
garbage_args:
        ret = SVC_GARBAGE;
        goto out;
auth_err:
        /* Restore write pointer to its original value: */
        xdr_ressize_check(rqstp, reject_stat);
        ret = SVC_DENIED;
        goto out;
complete:
        ret = SVC_COMPLETE;
        goto out;
drop:
        ret = SVC_DROP;
out:
        if (rsci)
                cache_put(&rsci->h, sn->rsc_cache);
        return ret;
}

static __be32 *
svcauth_gss_prepare_to_wrap(struct xdr_buf *resbuf, struct gss_svc_data *gsd)
{
        __be32 *p;
        u32 verf_len;

        p = gsd->verf_start;
        gsd->verf_start = NULL;

        /* If the reply stat is nonzero, don't wrap: */
        if (*(p-1) != rpc_success)
                return NULL;
        /* Skip the verifier: */
        p += 1;
        verf_len = ntohl(*p++);
        p += XDR_QUADLEN(verf_len);
        /* move accept_stat to right place: */
        memcpy(p, p + 2, 4);
        /* Also don't wrap if the accept stat is nonzero: */
        if (*p != rpc_success) {
                resbuf->head[0].iov_len -= 2 * 4;
                return NULL;
        }
        p++;
        return p;
}

static inline int
svcauth_gss_wrap_resp_integ(struct svc_rqst *rqstp)
{
        struct gss_svc_data *gsd = (struct gss_svc_data *)rqstp->rq_auth_data;
        struct rpc_gss_wire_cred *gc = &gsd->clcred;
        struct xdr_buf *resbuf = &rqstp->rq_res;
        struct xdr_buf integ_buf;
        struct xdr_netobj mic;
        struct kvec *resv;
        __be32 *p;
        int integ_offset, integ_len;
        int stat = -EINVAL;

        p = svcauth_gss_prepare_to_wrap(resbuf, gsd);
        if (p == NULL)
                goto out;
        integ_offset = (u8 *)(p + 1) - (u8 *)resbuf->head[0].iov_base;
        integ_len = resbuf->len - integ_offset;
        BUG_ON(integ_len % 4);
        *p++ = htonl(integ_len);
        *p++ = htonl(gc->gc_seq);
        if (xdr_buf_subsegment(resbuf, &integ_buf, integ_offset, integ_len))
                BUG();
        if (resbuf->tail[0].iov_base == NULL) {
                if (resbuf->head[0].iov_len + RPC_MAX_AUTH_SIZE > PAGE_SIZE)
                        goto out_err;
                resbuf->tail[0].iov_base = resbuf->head[0].iov_base
                                                + resbuf->head[0].iov_len;
                resbuf->tail[0].iov_len = 0;
        }
        resv = &resbuf->tail[0];
        mic.data = (u8 *)resv->iov_base + resv->iov_len + 4;
        if (gss_get_mic(gsd->rsci->mechctx, &integ_buf, &mic))
                goto out_err;
        svc_putnl(resv, mic.len);
        memset(mic.data + mic.len, 0,
                        round_up_to_quad(mic.len) - mic.len);
        resv->iov_len += XDR_QUADLEN(mic.len) << 2;
        /* not strictly required: */
        resbuf->len += XDR_QUADLEN(mic.len) << 2;
        BUG_ON(resv->iov_len > PAGE_SIZE);
out:
        stat = 0;
out_err:
        return stat;
}

static inline int
svcauth_gss_wrap_resp_priv(struct svc_rqst *rqstp)
{
        struct gss_svc_data *gsd = (struct gss_svc_data *)rqstp->rq_auth_data;
        struct rpc_gss_wire_cred *gc = &gsd->clcred;
        struct xdr_buf *resbuf = &rqstp->rq_res;
        struct page **inpages = NULL;
        __be32 *p, *len;
        int offset;
        int pad;

        p = svcauth_gss_prepare_to_wrap(resbuf, gsd);
        if (p == NULL)
                return 0;
        len = p++;
        offset = (u8 *)p - (u8 *)resbuf->head[0].iov_base;
        *p++ = htonl(gc->gc_seq);
        inpages = resbuf->pages;
        /* XXX: Would be better to write some xdr helper functions for
         * nfs{2,3,4}xdr.c that place the data right, instead of copying: */

        /*
         * If there is currently tail data, make sure there is
         * room for the head, tail, and 2 * RPC_MAX_AUTH_SIZE in
         * the page, and move the current tail data such that
         * there is RPC_MAX_AUTH_SIZE slack space available in
         * both the head and tail.
         */
        if (resbuf->tail[0].iov_base) {
                BUG_ON(resbuf->tail[0].iov_base >= resbuf->head[0].iov_base
                                                        + PAGE_SIZE);
                BUG_ON(resbuf->tail[0].iov_base < resbuf->head[0].iov_base);
                if (resbuf->tail[0].iov_len + resbuf->head[0].iov_len
                                + 2 * RPC_MAX_AUTH_SIZE > PAGE_SIZE)
                        return -ENOMEM;
                memmove(resbuf->tail[0].iov_base + RPC_MAX_AUTH_SIZE,
                        resbuf->tail[0].iov_base,
                        resbuf->tail[0].iov_len);
                resbuf->tail[0].iov_base += RPC_MAX_AUTH_SIZE;
        }
        /*
         * If there is no current tail data, make sure there is
         * room for the head data, and 2 * RPC_MAX_AUTH_SIZE in the
         * allotted page, and set up tail information such that there
         * is RPC_MAX_AUTH_SIZE slack space available in both the
         * head and tail.
         */
        if (resbuf->tail[0].iov_base == NULL) {
                if (resbuf->head[0].iov_len + 2*RPC_MAX_AUTH_SIZE > PAGE_SIZE)
                        return -ENOMEM;
                resbuf->tail[0].iov_base = resbuf->head[0].iov_base
                        + resbuf->head[0].iov_len + RPC_MAX_AUTH_SIZE;
                resbuf->tail[0].iov_len = 0;
        }
        if (gss_wrap(gsd->rsci->mechctx, offset, resbuf, inpages))
                return -ENOMEM;
        *len = htonl(resbuf->len - offset);
        pad = 3 - ((resbuf->len - offset - 1)&3);
        p = (__be32 *)(resbuf->tail[0].iov_base + resbuf->tail[0].iov_len);
        memset(p, 0, pad);
        resbuf->tail[0].iov_len += pad;
        resbuf->len += pad;
        return 0;
}

static int
svcauth_gss_release(struct svc_rqst *rqstp)
{
        struct gss_svc_data *gsd = (struct gss_svc_data *)rqstp->rq_auth_data;
        struct rpc_gss_wire_cred *gc = &gsd->clcred;
        struct xdr_buf *resbuf = &rqstp->rq_res;
        int stat = -EINVAL;
        struct sunrpc_net *sn = net_generic(rqstp->rq_xprt->xpt_net, sunrpc_net_id);

        if (gc->gc_proc != RPC_GSS_PROC_DATA)
                goto out;
        /* Release can be called twice, but we only wrap once. */
        if (gsd->verf_start == NULL)
                goto out;
        /* normally not set till svc_send, but we need it here: */
        /* XXX: what for?  Do we mess it up the moment we call svc_putu32
         * or whatever? */
        resbuf->len = total_buf_len(resbuf);
        switch (gc->gc_svc) {
        case RPC_GSS_SVC_NONE:
                break;
        case RPC_GSS_SVC_INTEGRITY:
                stat = svcauth_gss_wrap_resp_integ(rqstp);
                if (stat)
                        goto out_err;
                break;
        case RPC_GSS_SVC_PRIVACY:
                stat = svcauth_gss_wrap_resp_priv(rqstp);
                if (stat)
                        goto out_err;
                break;
        /*
         * For any other gc_svc value, svcauth_gss_accept() already set
         * the auth_error appropriately; just fall through:
         */
        }

out:
        stat = 0;
out_err:
        if (rqstp->rq_client)
                auth_domain_put(rqstp->rq_client);
        rqstp->rq_client = NULL;
        if (rqstp->rq_gssclient)
                auth_domain_put(rqstp->rq_gssclient);
        rqstp->rq_gssclient = NULL;
        if (rqstp->rq_cred.cr_group_info)
                put_group_info(rqstp->rq_cred.cr_group_info);
        rqstp->rq_cred.cr_group_info = NULL;
        if (gsd->rsci)
                cache_put(&gsd->rsci->h, sn->rsc_cache);
        gsd->rsci = NULL;

        return stat;
}

static void
svcauth_gss_domain_release(struct auth_domain *dom)
{
        struct gss_domain *gd = container_of(dom, struct gss_domain, h);

        kfree(dom->name);
        kfree(gd);
}

static struct auth_ops svcauthops_gss = {
        .name           = "rpcsec_gss",
        .owner          = THIS_MODULE,
        .flavour        = RPC_AUTH_GSS,
        .accept         = svcauth_gss_accept,
        .release        = svcauth_gss_release,
        .domain_release = svcauth_gss_domain_release,
        .set_client     = svcauth_gss_set_client,
};

static int rsi_cache_create_net(struct net *net)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        struct cache_detail *cd;
        int err;

        cd = cache_create_net(&rsi_cache_template, net);
        if (IS_ERR(cd))
                return PTR_ERR(cd);
        err = cache_register_net(cd, net);
        if (err) {
                cache_destroy_net(cd, net);
                return err;
        }
        sn->rsi_cache = cd;
        return 0;
}

static void rsi_cache_destroy_net(struct net *net)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        struct cache_detail *cd = sn->rsi_cache;

        sn->rsi_cache = NULL;
        cache_purge(cd);
        cache_unregister_net(cd, net);
        cache_destroy_net(cd, net);
}

static int rsc_cache_create_net(struct net *net)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        struct cache_detail *cd;
        int err;

        cd = cache_create_net(&rsc_cache_template, net);
        if (IS_ERR(cd))
                return PTR_ERR(cd);
        err = cache_register_net(cd, net);
        if (err) {
                cache_destroy_net(cd, net);
                return err;
        }
        sn->rsc_cache = cd;
        return 0;
}

static void rsc_cache_destroy_net(struct net *net)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        struct cache_detail *cd = sn->rsc_cache;

        sn->rsc_cache = NULL;
        cache_purge(cd);
        cache_unregister_net(cd, net);
        cache_destroy_net(cd, net);
}

int
gss_svc_init_net(struct net *net)
{
        int rv;

        rv = rsc_cache_create_net(net);
        if (rv)
                return rv;
        rv = rsi_cache_create_net(net);
        if (rv)
                goto out1;
        rv = create_use_gss_proxy_proc_entry(net);
        if (rv)
                goto out2;
        return 0;
out2:
        destroy_use_gss_proxy_proc_entry(net);
out1:
        rsc_cache_destroy_net(net);
        return rv;
}

void
gss_svc_shutdown_net(struct net *net)
{
        destroy_use_gss_proxy_proc_entry(net);
        rsi_cache_destroy_net(net);
        rsc_cache_destroy_net(net);
}

int
gss_svc_init(void)
{
        return svc_auth_register(RPC_AUTH_GSS, &svcauthops_gss);
}

void
gss_svc_shutdown(void)
{
        svc_auth_unregister(RPC_AUTH_GSS);
}