[PATCH] knfsd: svcrpc: fix gss krb5i memory leak

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

/*
 * 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/types.h>
#include <linux/module.h>
#include <linux/pagemap.h>

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

#ifdef RPC_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)
#define RSI_HASHMASK    (RSI_HASHMAX-1)

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 cache_head *rsi_table[RSI_HASHMAX];
static struct cache_detail rsi_cache;
static struct rsi *rsi_update(struct rsi *new, struct rsi *old);
static struct rsi *rsi_lookup(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(&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;
        if (len == 0) {
                goto out;
        } else {
                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(&rsii, rsip);
        status = 0;
out:
        rsi_free(&rsii);
        if (rsip)
                cache_put(&rsip->h, &rsi_cache);
        else
                status = -ENOMEM;
        return status;
}

static struct cache_detail rsi_cache = {
        .owner          = THIS_MODULE,
        .hash_size      = RSI_HASHMAX,
        .hash_table     = rsi_table,
        .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 rsi *item)
{
        struct cache_head *ch;
        int hash = rsi_hash(item);

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

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

        ch = sunrpc_cache_update(&rsi_cache, &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 RSC_HASHMASK    (RSC_HASHMAX-1)

#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 cache_head *rsc_table[RSC_HASHMAX];
static struct cache_detail rsc_cache;
static struct rsc *rsc_update(struct rsc *new, struct rsc *old);
static struct rsc *rsc_lookup(struct rsc *item);

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

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;
        new->cred.cr_group_info = NULL;
}

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;
        tmp->cred.cr_group_info = NULL;
}

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 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(&rsci);
        if (!rscp)
                goto out;

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

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

                /* number of additional gid's */
                if (get_int(&mesg, &N))
                        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++) {
                        gid_t gid;
                        if (get_int(&mesg, &gid))
                                goto out;
                        GROUP_AT(rsci.cred.cr_group_info, i) = gid;
                }

                /* mech name */
                len = qword_get(&mesg, buf, mlen);
                if (len < 0)
                        goto out;
                gm = 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);
                if (status)
                        goto out;
        }
        rsci.h.expiry_time = expiry;
        rscp = rsc_update(&rsci, rscp);
        status = 0;
out:
        gss_mech_put(gm);
        rsc_free(&rsci);
        if (rscp)
                cache_put(&rscp->h, &rsc_cache);
        else
                status = -ENOMEM;
        return status;
}

static struct cache_detail rsc_cache = {
        .owner          = THIS_MODULE,
        .hash_size      = RSC_HASHMAX,
        .hash_table     = rsc_table,
        .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 rsc *item)
{
        struct cache_head *ch;
        int hash = rsc_hash(item);

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

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

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


static struct rsc *
gss_svc_searchbyctx(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(&rsci);
        rsc_free(&rsci);
        if (!found)
                return NULL;
        if (cache_check(&rsc_cache, &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;

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;

        test = auth_domain_lookup(name, &new->h);
        if (test != &new->h) { /* XXX Duplicate registration? */
                auth_domain_put(&new->h);
                /* dangling ref-count... */
                goto out;
        }
        return 0;

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

EXPORT_SYMBOL(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 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;

        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;
        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;

        rqstp->rq_sendfile_ok = 0;

        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;

        rqstp->rq_client = find_gss_auth_domain(rsci->mechctx, gc->gc_svc);
        if (rqstp->rq_client == NULL)
                return SVC_DENIED;
        return SVC_OK;
}

static inline int
gss_write_init_verf(struct svc_rqst *rqstp, struct rsi *rsip)
{
        struct rsc *rsci;

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

/*
 * 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 xdr_netobj tmpobj;
        struct gss_svc_data *svcdata = rqstp->rq_auth_data;
        struct rpc_gss_wire_cred *gc;
        struct rsc      *rsci = NULL;
        struct rsi      *rsip, rsikey;
        __be32          *rpcstart;
        __be32          *reject_stat = resv->iov_base + resv->iov_len;
        int             ret;

        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 preceeded 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;

        /*
         * We've successfully parsed the credential. Let's check out the
         * verifier.  An AUTH_NULL verifier is allowed (and required) for
         * INIT and CONTINUE_INIT requests. AUTH_RPCSEC_GSS is required for
         * PROC_DATA and PROC_DESTROY.
         *
         * AUTH_NULL verifier is 0 (AUTH_NULL), 0 (length).
         * AUTH_RPCSEC_GSS verifier is:
         *   6 (AUTH_RPCSEC_GSS), length, checksum.
         * checksum is calculated over rpcheader from xid up to here.
         */
        *authp = rpc_autherr_badverf;
        switch (gc->gc_proc) {
        case RPC_GSS_PROC_INIT:
        case RPC_GSS_PROC_CONTINUE_INIT:
                if (argv->iov_len < 2 * 4)
                        goto auth_err;
                if (svc_getnl(argv) != RPC_AUTH_NULL)
                        goto auth_err;
                if (svc_getnl(argv) != 0)
                        goto auth_err;
                break;
        case RPC_GSS_PROC_DATA:
        case RPC_GSS_PROC_DESTROY:
                *authp = rpcsec_gsserr_credproblem;
                rsci = gss_svc_searchbyctx(&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_INIT:
        case RPC_GSS_PROC_CONTINUE_INIT:
                *authp = rpc_autherr_badcred;
                if (gc->gc_proc == RPC_GSS_PROC_INIT && gc->gc_ctx.len != 0)
                        goto auth_err;
                memset(&rsikey, 0, sizeof(rsikey));
                if (dup_netobj(&rsikey.in_handle, &gc->gc_ctx))
                        goto drop;
                *authp = rpc_autherr_badverf;
                if (svc_safe_getnetobj(argv, &tmpobj)) {
                        kfree(rsikey.in_handle.data);
                        goto auth_err;
                }
                if (dup_netobj(&rsikey.in_token, &tmpobj)) {
                        kfree(rsikey.in_handle.data);
                        goto drop;
                }

                rsip = rsi_lookup(&rsikey);
                rsi_free(&rsikey);
                if (!rsip) {
                        goto drop;
                }
                switch(cache_check(&rsi_cache, &rsip->h, &rqstp->rq_chandle)) {
                case -EAGAIN:
                        goto drop;
                case -ENOENT:
                        goto drop;
                case 0:
                        if (gss_write_init_verf(rqstp, rsip))
                                goto drop;
                        if (resv->iov_len + 4 > PAGE_SIZE)
                                goto drop;
                        svc_putnl(resv, RPC_SUCCESS);
                        if (svc_safe_putnetobj(resv, &rsip->out_handle))
                                goto drop;
                        if (resv->iov_len + 3 * 4 > PAGE_SIZE)
                                goto drop;
                        svc_putnl(resv, rsip->major_status);
                        svc_putnl(resv, rsip->minor_status);
                        svc_putnl(resv, GSS_SEQ_WIN);
                        if (svc_safe_putnetobj(resv, &rsip->out_token))
                                goto drop;
                        rqstp->rq_client = NULL;
                }
                goto complete;
        case RPC_GSS_PROC_DESTROY:
                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:
                        if (unwrap_integ_data(&rqstp->rq_arg,
                                        gc->gc_seq, rsci->mechctx))
                                goto auth_err;
                        /* placeholders for length and seq. number: */
                        svc_putnl(resv, 0);
                        svc_putnl(resv, 0);
                        break;
                case RPC_GSS_SVC_PRIVACY:
                        if (unwrap_priv_data(rqstp, &rqstp->rq_arg,
                                        gc->gc_seq, rsci->mechctx))
                                goto auth_err;
                        /* placeholders for length and seq. number: */
                        svc_putnl(resv, 0);
                        svc_putnl(resv, 0);
                        break;
                default:
                        goto auth_err;
                }
                svcdata->rsci = rsci;
                cache_get(&rsci->h);
                ret = SVC_OK;
                goto out;
        }
auth_err:
        /* Restore write pointer to 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, &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->page_len == 0
                        && resbuf->head[0].iov_len + RPC_MAX_AUTH_SIZE
                        < PAGE_SIZE) {
                BUG_ON(resbuf->tail[0].iov_len);
                /* Use head for everything */
                resv = &resbuf->head[0];
        } else 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];
        } else {
                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 (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 (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;

        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;
        default:
                goto out_err;
        }

out:
        stat = 0;
out_err:
        if (rqstp->rq_client)
                auth_domain_put(rqstp->rq_client);
        rqstp->rq_client = 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, &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,
};

int
gss_svc_init(void)
{
        int rv = svc_auth_register(RPC_AUTH_GSS, &svcauthops_gss);
        if (rv == 0) {
                cache_register(&rsc_cache);
                cache_register(&rsi_cache);
        }
        return rv;
}

void
gss_svc_shutdown(void)
{
        if (cache_unregister(&rsc_cache))
                printk(KERN_ERR "auth_rpcgss: failed to unregister rsc cache\n");
        if (cache_unregister(&rsi_cache))
                printk(KERN_ERR "auth_rpcgss: failed to unregister rsi cache\n");
        svc_auth_unregister(RPC_AUTH_GSS);
}