auth.c

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/*
 * linux/net/sunrpc/auth.c
 *
 * Generic RPC client authentication API.
 *
 * Copyright (C) 1996, Olaf Kirch <[email protected]>
 */

#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/sunrpc/gss_api.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);

int
rpcauth_list_flavors(rpc_authflavor_t *array, int size)
{
    rpc_authflavor_t flavor;
    int result = 0;

    spin_lock(&rpc_authflavor_lock);
    for (flavor = 0; flavor < RPC_AUTH_MAXFLAVOR; flavor++) {
        const struct rpc_authops *ops = auth_flavors[flavor];
        rpc_authflavor_t pseudos[4];
        int i, len;

        if (result >= size) {
            result = -ENOMEM;
            break;
        }

        if (ops == NULL)
            continue;
        if (ops->list_pseudoflavors == NULL) {
            array[result++] = ops->au_flavor;
            continue;
        }
        len = ops->list_pseudoflavors(pseudos, ARRAY_SIZE(pseudos));
        if (len < 0) {
            result = len;
            break;
        }
        for (i = 0; i < len; i++) {
            if (result >= size) {
                result = -ENOMEM;
                break;
            }
            array[result++] = pseudos[i];
        }
    }
    spin_unlock(&rpc_authflavor_lock);

    dprintk("RPC:       %s returns %d\n", __func__, result);
    return result;
}
EXPORT_SYMBOL_GPL(rpcauth_list_flavors);

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);
}