/*
 * linux/net/sunrpc/auth.c
 *
 * Generic RPC client authentication API.
 *
 * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/types.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/hash.h>
#include <linux/sunrpc/clnt.h>
#include <linux/spinlock.h>

#ifdef RPC_DEBUG
# define RPCDBG_FACILITY        RPCDBG_AUTH
#endif

#define RPC_CREDCACHE_DEFAULT_HASHBITS  (4)
struct rpc_cred_cache {
        struct hlist_head       *hashtable;
        unsigned int            hashbits;
        spinlock_t              lock;
};

static unsigned int auth_hashbits = RPC_CREDCACHE_DEFAULT_HASHBITS;

static DEFINE_SPINLOCK(rpc_authflavor_lock);
static const struct rpc_authops *auth_flavors[RPC_AUTH_MAXFLAVOR] = {
        &authnull_ops,          /* AUTH_NULL */
        &authunix_ops,          /* AUTH_UNIX */
        NULL,                   /* others can be loadable modules */
};

static LIST_HEAD(cred_unused);
static unsigned long number_cred_unused;

#define MAX_HASHTABLE_BITS (14)
static int param_set_hashtbl_sz(const char *val, const struct kernel_param *kp)
{
        unsigned long num;
        unsigned int nbits;
        int ret;

        if (!val)
                goto out_inval;
        ret = strict_strtoul(val, 0, &num);
        if (ret == -EINVAL)
                goto out_inval;
        nbits = fls(num);
        if (num > (1U << nbits))
                nbits++;
        if (nbits > MAX_HASHTABLE_BITS || nbits < 2)
                goto out_inval;
        *(unsigned int *)kp->arg = nbits;
        return 0;
out_inval:
        return -EINVAL;
}

static int param_get_hashtbl_sz(char *buffer, const struct kernel_param *kp)
{
        unsigned int nbits;

        nbits = *(unsigned int *)kp->arg;
        return sprintf(buffer, "%u", 1U << nbits);
}

#define param_check_hashtbl_sz(name, p) __param_check(name, p, unsigned int);

static struct kernel_param_ops param_ops_hashtbl_sz = {
        .set = param_set_hashtbl_sz,
        .get = param_get_hashtbl_sz,
};

module_param_named(auth_hashtable_size, auth_hashbits, hashtbl_sz, 0644);
MODULE_PARM_DESC(auth_hashtable_size, "RPC credential cache hashtable size");

static u32
pseudoflavor_to_flavor(u32 flavor) {
        if (flavor >= RPC_AUTH_MAXFLAVOR)
                return RPC_AUTH_GSS;
        return flavor;
}

int
rpcauth_register(const struct rpc_authops *ops)
{
        rpc_authflavor_t flavor;
        int ret = -EPERM;

        if ((flavor = ops->au_flavor) >= RPC_AUTH_MAXFLAVOR)
                return -EINVAL;
        spin_lock(&rpc_authflavor_lock);
        if (auth_flavors[flavor] == NULL) {
                auth_flavors[flavor] = ops;
                ret = 0;
        }
        spin_unlock(&rpc_authflavor_lock);
        return ret;
}
EXPORT_SYMBOL_GPL(rpcauth_register);

int
rpcauth_unregister(const struct rpc_authops *ops)
{
        rpc_authflavor_t flavor;
        int ret = -EPERM;

        if ((flavor = ops->au_flavor) >= RPC_AUTH_MAXFLAVOR)
                return -EINVAL;
        spin_lock(&rpc_authflavor_lock);
        if (auth_flavors[flavor] == ops) {
                auth_flavors[flavor] = NULL;
                ret = 0;
        }
        spin_unlock(&rpc_authflavor_lock);
        return ret;
}
EXPORT_SYMBOL_GPL(rpcauth_unregister);

struct rpc_auth *
rpcauth_create(rpc_authflavor_t pseudoflavor, struct rpc_clnt *clnt)
{
        struct rpc_auth         *auth;
        const struct rpc_authops *ops;
        u32                     flavor = pseudoflavor_to_flavor(pseudoflavor);

        auth = ERR_PTR(-EINVAL);
        if (flavor >= RPC_AUTH_MAXFLAVOR)
                goto out;

        if ((ops = auth_flavors[flavor]) == NULL)
                request_module("rpc-auth-%u", flavor);
        spin_lock(&rpc_authflavor_lock);
        ops = auth_flavors[flavor];
        if (ops == NULL || !try_module_get(ops->owner)) {
                spin_unlock(&rpc_authflavor_lock);
                goto out;
        }
        spin_unlock(&rpc_authflavor_lock);
        auth = ops->create(clnt, pseudoflavor);
        module_put(ops->owner);
        if (IS_ERR(auth))
                return auth;
        if (clnt->cl_auth)
                rpcauth_release(clnt->cl_auth);
        clnt->cl_auth = auth;

out:
        return auth;
}
EXPORT_SYMBOL_GPL(rpcauth_create);

void
rpcauth_release(struct rpc_auth *auth)
{
        if (!atomic_dec_and_test(&auth->au_count))
                return;
        auth->au_ops->destroy(auth);
}

static DEFINE_SPINLOCK(rpc_credcache_lock);

static void
rpcauth_unhash_cred_locked(struct rpc_cred *cred)
{
        hlist_del_rcu(&cred->cr_hash);
        smp_mb__before_clear_bit();
        clear_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags);
}

static int
rpcauth_unhash_cred(struct rpc_cred *cred)
{
        spinlock_t *cache_lock;
        int ret;

        cache_lock = &cred->cr_auth->au_credcache->lock;
        spin_lock(cache_lock);
        ret = atomic_read(&cred->cr_count) == 0;
        if (ret)
                rpcauth_unhash_cred_locked(cred);
        spin_unlock(cache_lock);
        return ret;
}

/*
 * Initialize RPC credential cache
 */
int
rpcauth_init_credcache(struct rpc_auth *auth)
{
        struct rpc_cred_cache *new;
        unsigned int hashsize;

        new = kmalloc(sizeof(*new), GFP_KERNEL);
        if (!new)
                goto out_nocache;
        new->hashbits = auth_hashbits;
        hashsize = 1U << new->hashbits;
        new->hashtable = kcalloc(hashsize, sizeof(new->hashtable[0]), GFP_KERNEL);
        if (!new->hashtable)
                goto out_nohashtbl;
        spin_lock_init(&new->lock);
        auth->au_credcache = new;
        return 0;
out_nohashtbl:
        kfree(new);
out_nocache:
        return -ENOMEM;
}
EXPORT_SYMBOL_GPL(rpcauth_init_credcache);

/*
 * Destroy a list of credentials
 */
static inline
void rpcauth_destroy_credlist(struct list_head *head)
{
        struct rpc_cred *cred;

        while (!list_empty(head)) {
                cred = list_entry(head->next, struct rpc_cred, cr_lru);
                list_del_init(&cred->cr_lru);
                put_rpccred(cred);
        }
}

/*
 * Clear the RPC credential cache, and delete those credentials
 * that are not referenced.
 */
void
rpcauth_clear_credcache(struct rpc_cred_cache *cache)
{
        LIST_HEAD(free);
        struct hlist_head *head;
        struct rpc_cred *cred;
        unsigned int hashsize = 1U << cache->hashbits;
        int             i;

        spin_lock(&rpc_credcache_lock);
        spin_lock(&cache->lock);
        for (i = 0; i < hashsize; i++) {
                head = &cache->hashtable[i];
                while (!hlist_empty(head)) {
                        cred = hlist_entry(head->first, struct rpc_cred, cr_hash);
                        get_rpccred(cred);
                        if (!list_empty(&cred->cr_lru)) {
                                list_del(&cred->cr_lru);
                                number_cred_unused--;
                        }
                        list_add_tail(&cred->cr_lru, &free);
                        rpcauth_unhash_cred_locked(cred);
                }
        }
        spin_unlock(&cache->lock);
        spin_unlock(&rpc_credcache_lock);
        rpcauth_destroy_credlist(&free);
}

/*
 * Destroy the RPC credential cache
 */
void
rpcauth_destroy_credcache(struct rpc_auth *auth)
{
        struct rpc_cred_cache *cache = auth->au_credcache;

        if (cache) {
                auth->au_credcache = NULL;
                rpcauth_clear_credcache(cache);
                kfree(cache->hashtable);
                kfree(cache);
        }
}
EXPORT_SYMBOL_GPL(rpcauth_destroy_credcache);


#define RPC_AUTH_EXPIRY_MORATORIUM (60 * HZ)

/*
 * Remove stale credentials. Avoid sleeping inside the loop.
 */
static int
rpcauth_prune_expired(struct list_head *free, int nr_to_scan)
{
        spinlock_t *cache_lock;
        struct rpc_cred *cred, *next;
        unsigned long expired = jiffies - RPC_AUTH_EXPIRY_MORATORIUM;

        list_for_each_entry_safe(cred, next, &cred_unused, cr_lru) {

                if (nr_to_scan-- == 0)
                        break;
                /*
                 * Enforce a 60 second garbage collection moratorium
                 * Note that the cred_unused list must be time-ordered.
                 */
                if (time_in_range(cred->cr_expire, expired, jiffies) &&
                    test_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags) != 0)
                        return 0;

                list_del_init(&cred->cr_lru);
                number_cred_unused--;
                if (atomic_read(&cred->cr_count) != 0)
                        continue;

                cache_lock = &cred->cr_auth->au_credcache->lock;
                spin_lock(cache_lock);
                if (atomic_read(&cred->cr_count) == 0) {
                        get_rpccred(cred);
                        list_add_tail(&cred->cr_lru, free);
                        rpcauth_unhash_cred_locked(cred);
                }
                spin_unlock(cache_lock);
        }
        return (number_cred_unused / 100) * sysctl_vfs_cache_pressure;
}

/*
 * Run memory cache shrinker.
 */
static int
rpcauth_cache_shrinker(struct shrinker *shrink, struct shrink_control *sc)
{
        LIST_HEAD(free);
        int res;
        int nr_to_scan = sc->nr_to_scan;
        gfp_t gfp_mask = sc->gfp_mask;

        if ((gfp_mask & GFP_KERNEL) != GFP_KERNEL)
                return (nr_to_scan == 0) ? 0 : -1;
        if (list_empty(&cred_unused))
                return 0;
        spin_lock(&rpc_credcache_lock);
        res = rpcauth_prune_expired(&free, nr_to_scan);
        spin_unlock(&rpc_credcache_lock);
        rpcauth_destroy_credlist(&free);
        return res;
}

/*
 * Look up a process' credentials in the authentication cache
 */
struct rpc_cred *
rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred,
                int flags)
{
        LIST_HEAD(free);
        struct rpc_cred_cache *cache = auth->au_credcache;
        struct hlist_node *pos;
        struct rpc_cred *cred = NULL,
                        *entry, *new;
        unsigned int nr;

        nr = hash_long(acred->uid, cache->hashbits);

        rcu_read_lock();
        hlist_for_each_entry_rcu(entry, pos, &cache->hashtable[nr], cr_hash) {
                if (!entry->cr_ops->crmatch(acred, entry, flags))
                        continue;
                spin_lock(&cache->lock);
                if (test_bit(RPCAUTH_CRED_HASHED, &entry->cr_flags) == 0) {
                        spin_unlock(&cache->lock);
                        continue;
                }
                cred = get_rpccred(entry);
                spin_unlock(&cache->lock);
                break;
        }
        rcu_read_unlock();

        if (cred != NULL)
                goto found;

        new = auth->au_ops->crcreate(auth, acred, flags);
        if (IS_ERR(new)) {
                cred = new;
                goto out;
        }

        spin_lock(&cache->lock);
        hlist_for_each_entry(entry, pos, &cache->hashtable[nr], cr_hash) {
                if (!entry->cr_ops->crmatch(acred, entry, flags))
                        continue;
                cred = get_rpccred(entry);
                break;
        }
        if (cred == NULL) {
                cred = new;
                set_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags);
                hlist_add_head_rcu(&cred->cr_hash, &cache->hashtable[nr]);
        } else
                list_add_tail(&new->cr_lru, &free);
        spin_unlock(&cache->lock);
found:
        if (test_bit(RPCAUTH_CRED_NEW, &cred->cr_flags) &&
            cred->cr_ops->cr_init != NULL &&
            !(flags & RPCAUTH_LOOKUP_NEW)) {
                int res = cred->cr_ops->cr_init(auth, cred);
                if (res < 0) {
                        put_rpccred(cred);
                        cred = ERR_PTR(res);
                }
        }
        rpcauth_destroy_credlist(&free);
out:
        return cred;
}
EXPORT_SYMBOL_GPL(rpcauth_lookup_credcache);

struct rpc_cred *
rpcauth_lookupcred(struct rpc_auth *auth, int flags)
{
        struct auth_cred acred;
        struct rpc_cred *ret;
        const struct cred *cred = current_cred();

        dprintk("RPC:       looking up %s cred\n",
                auth->au_ops->au_name);

        memset(&acred, 0, sizeof(acred));
        acred.uid = cred->fsuid;
        acred.gid = cred->fsgid;
        acred.group_info = get_group_info(((struct cred *)cred)->group_info);

        ret = auth->au_ops->lookup_cred(auth, &acred, flags);
        put_group_info(acred.group_info);
        return ret;
}

void
rpcauth_init_cred(struct rpc_cred *cred, const struct auth_cred *acred,
                  struct rpc_auth *auth, const struct rpc_credops *ops)
{
        INIT_HLIST_NODE(&cred->cr_hash);
        INIT_LIST_HEAD(&cred->cr_lru);
        atomic_set(&cred->cr_count, 1);
        cred->cr_auth = auth;
        cred->cr_ops = ops;
        cred->cr_expire = jiffies;
#ifdef RPC_DEBUG
        cred->cr_magic = RPCAUTH_CRED_MAGIC;
#endif
        cred->cr_uid = acred->uid;
}
EXPORT_SYMBOL_GPL(rpcauth_init_cred);

struct rpc_cred *
rpcauth_generic_bind_cred(struct rpc_task *task, struct rpc_cred *cred, int lookupflags)
{
        dprintk("RPC: %5u holding %s cred %p\n", task->tk_pid,
                        cred->cr_auth->au_ops->au_name, cred);
        return get_rpccred(cred);
}
EXPORT_SYMBOL_GPL(rpcauth_generic_bind_cred);

static struct rpc_cred *
rpcauth_bind_root_cred(struct rpc_task *task, int lookupflags)
{
        struct rpc_auth *auth = task->tk_client->cl_auth;
        struct auth_cred acred = {
                .uid = 0,
                .gid = 0,
        };

        dprintk("RPC: %5u looking up %s cred\n",
                task->tk_pid, task->tk_client->cl_auth->au_ops->au_name);
        return auth->au_ops->lookup_cred(auth, &acred, lookupflags);
}

static struct rpc_cred *
rpcauth_bind_new_cred(struct rpc_task *task, int lookupflags)
{
        struct rpc_auth *auth = task->tk_client->cl_auth;

        dprintk("RPC: %5u looking up %s cred\n",
                task->tk_pid, auth->au_ops->au_name);
        return rpcauth_lookupcred(auth, lookupflags);
}

static int
rpcauth_bindcred(struct rpc_task *task, struct rpc_cred *cred, int flags)
{
        struct rpc_rqst *req = task->tk_rqstp;
        struct rpc_cred *new;
        int lookupflags = 0;

        if (flags & RPC_TASK_ASYNC)
                lookupflags |= RPCAUTH_LOOKUP_NEW;
        if (cred != NULL)
                new = cred->cr_ops->crbind(task, cred, lookupflags);
        else if (flags & RPC_TASK_ROOTCREDS)
                new = rpcauth_bind_root_cred(task, lookupflags);
        else
                new = rpcauth_bind_new_cred(task, lookupflags);
        if (IS_ERR(new))
                return PTR_ERR(new);
        if (req->rq_cred != NULL)
                put_rpccred(req->rq_cred);
        req->rq_cred = new;
        return 0;
}

void
put_rpccred(struct rpc_cred *cred)
{
        /* Fast path for unhashed credentials */
        if (test_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags) == 0) {
                if (atomic_dec_and_test(&cred->cr_count))
                        cred->cr_ops->crdestroy(cred);
                return;
        }

        if (!atomic_dec_and_lock(&cred->cr_count, &rpc_credcache_lock))
                return;
        if (!list_empty(&cred->cr_lru)) {
                number_cred_unused--;
                list_del_init(&cred->cr_lru);
        }
        if (test_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags) != 0) {
                if (test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) != 0) {
                        cred->cr_expire = jiffies;
                        list_add_tail(&cred->cr_lru, &cred_unused);
                        number_cred_unused++;
                        goto out_nodestroy;
                }
                if (!rpcauth_unhash_cred(cred)) {
                        /* We were hashed and someone looked us up... */
                        goto out_nodestroy;
                }
        }
        spin_unlock(&rpc_credcache_lock);
        cred->cr_ops->crdestroy(cred);
        return;
out_nodestroy:
        spin_unlock(&rpc_credcache_lock);
}
EXPORT_SYMBOL_GPL(put_rpccred);

__be32 *
rpcauth_marshcred(struct rpc_task *task, __be32 *p)
{
        struct rpc_cred *cred = task->tk_rqstp->rq_cred;

        dprintk("RPC: %5u marshaling %s cred %p\n",
                task->tk_pid, cred->cr_auth->au_ops->au_name, cred);

        return cred->cr_ops->crmarshal(task, p);
}

__be32 *
rpcauth_checkverf(struct rpc_task *task, __be32 *p)
{
        struct rpc_cred *cred = task->tk_rqstp->rq_cred;

        dprintk("RPC: %5u validating %s cred %p\n",
                task->tk_pid, cred->cr_auth->au_ops->au_name, cred);

        return cred->cr_ops->crvalidate(task, p);
}

static void rpcauth_wrap_req_encode(kxdreproc_t encode, struct rpc_rqst *rqstp,
                                   __be32 *data, void *obj)
{
        struct xdr_stream xdr;

        xdr_init_encode(&xdr, &rqstp->rq_snd_buf, data);
        encode(rqstp, &xdr, obj);
}

int
rpcauth_wrap_req(struct rpc_task *task, kxdreproc_t encode, void *rqstp,
                __be32 *data, void *obj)
{
        struct rpc_cred *cred = task->tk_rqstp->rq_cred;

        dprintk("RPC: %5u using %s cred %p to wrap rpc data\n",
                        task->tk_pid, cred->cr_ops->cr_name, cred);
        if (cred->cr_ops->crwrap_req)
                return cred->cr_ops->crwrap_req(task, encode, rqstp, data, obj);
        /* By default, we encode the arguments normally. */
        rpcauth_wrap_req_encode(encode, rqstp, data, obj);
        return 0;
}

static int
rpcauth_unwrap_req_decode(kxdrdproc_t decode, struct rpc_rqst *rqstp,
                          __be32 *data, void *obj)
{
        struct xdr_stream xdr;

        xdr_init_decode(&xdr, &rqstp->rq_rcv_buf, data);
        return decode(rqstp, &xdr, obj);
}

int
rpcauth_unwrap_resp(struct rpc_task *task, kxdrdproc_t decode, void *rqstp,
                __be32 *data, void *obj)
{
        struct rpc_cred *cred = task->tk_rqstp->rq_cred;

        dprintk("RPC: %5u using %s cred %p to unwrap rpc data\n",
                        task->tk_pid, cred->cr_ops->cr_name, cred);
        if (cred->cr_ops->crunwrap_resp)
                return cred->cr_ops->crunwrap_resp(task, decode, rqstp,
                                                   data, obj);
        /* By default, we decode the arguments normally. */
        return rpcauth_unwrap_req_decode(decode, rqstp, data, obj);
}

int
rpcauth_refreshcred(struct rpc_task *task)
{
        struct rpc_cred *cred;
        int err;

        cred = task->tk_rqstp->rq_cred;
        if (cred == NULL) {
                err = rpcauth_bindcred(task, task->tk_msg.rpc_cred, task->tk_flags);
                if (err < 0)
                        goto out;
                cred = task->tk_rqstp->rq_cred;
        };
        dprintk("RPC: %5u refreshing %s cred %p\n",
                task->tk_pid, cred->cr_auth->au_ops->au_name, cred);

        err = cred->cr_ops->crrefresh(task);
out:
        if (err < 0)
                task->tk_status = err;
        return err;
}

void
rpcauth_invalcred(struct rpc_task *task)
{
        struct rpc_cred *cred = task->tk_rqstp->rq_cred;

        dprintk("RPC: %5u invalidating %s cred %p\n",
                task->tk_pid, cred->cr_auth->au_ops->au_name, cred);
        if (cred)
                clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
}

int
rpcauth_uptodatecred(struct rpc_task *task)
{
        struct rpc_cred *cred = task->tk_rqstp->rq_cred;

        return cred == NULL ||
                test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) != 0;
}

static struct shrinker rpc_cred_shrinker = {
        .shrink = rpcauth_cache_shrinker,
        .seeks = DEFAULT_SEEKS,
};

int __init rpcauth_init_module(void)
{
        int err;

        err = rpc_init_authunix();
        if (err < 0)
                goto out1;
        err = rpc_init_generic_auth();
        if (err < 0)
                goto out2;
        register_shrinker(&rpc_cred_shrinker);
        return 0;
out2:
        rpc_destroy_authunix();
out1:
        return err;
}

void rpcauth_remove_module(void)
{
        rpc_destroy_authunix();
        rpc_destroy_generic_auth();
        unregister_shrinker(&rpc_cred_shrinker);
}