auth_unix.c

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/*
 * linux/net/sunrpc/auth_unix.c
 *
 * UNIX-style authentication; no AUTH_SHORT support
 *
 * Copyright (C) 1996, Olaf Kirch <[email protected]>
 */

#include <linux/slab.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/auth.h>
#include <linux/user_namespace.h>

#define NFS_NGROUPS 16

struct unx_cred {
    struct rpc_cred     uc_base;
    gid_t           uc_gid;
    gid_t           uc_gids[NFS_NGROUPS];
};
#define uc_uid          uc_base.cr_uid

#define UNX_WRITESLACK      (21 + (UNX_MAXNODENAME >> 2))

#ifdef RPC_DEBUG
# define RPCDBG_FACILITY    RPCDBG_AUTH
#endif

static struct rpc_auth      unix_auth;
static const struct rpc_credops unix_credops;

static struct rpc_auth *
unx_create(struct rpc_clnt *clnt, rpc_authflavor_t flavor)
{
    dprintk("RPC:       creating UNIX authenticator for client %p\n",
            clnt);
    atomic_inc(&unix_auth.au_count);
    return &unix_auth;
}

static void
unx_destroy(struct rpc_auth *auth)
{
    dprintk("RPC:       destroying UNIX authenticator %p\n", auth);
    rpcauth_clear_credcache(auth->au_credcache);
}

/*
 * Lookup AUTH_UNIX creds for current process
 */
static struct rpc_cred *
unx_lookup_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
    return rpcauth_lookup_credcache(auth, acred, flags);
}

static struct rpc_cred *
unx_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
    struct unx_cred *cred;
    unsigned int groups = 0;
    unsigned int i;

    dprintk("RPC:       allocating UNIX cred for uid %d gid %d\n",
            acred->uid, acred->gid);

    if (!(cred = kmalloc(sizeof(*cred), GFP_NOFS)))
        return ERR_PTR(-ENOMEM);

    rpcauth_init_cred(&cred->uc_base, acred, auth, &unix_credops);
    cred->uc_base.cr_flags = 1UL << RPCAUTH_CRED_UPTODATE;

    if (acred->group_info != NULL)
        groups = acred->group_info->ngroups;
    if (groups > NFS_NGROUPS)
        groups = NFS_NGROUPS;

    cred->uc_gid = acred->gid;
    for (i = 0; i < groups; i++) {
        gid_t gid;
        gid = from_kgid(&init_user_ns, GROUP_AT(acred->group_info, i));
        cred->uc_gids[i] = gid;
    }
    if (i < NFS_NGROUPS)
        cred->uc_gids[i] = NOGROUP;

    return &cred->uc_base;
}

static void
unx_free_cred(struct unx_cred *unx_cred)
{
    dprintk("RPC:       unx_free_cred %p\n", unx_cred);
    kfree(unx_cred);
}

static void
unx_free_cred_callback(struct rcu_head *head)
{
    struct unx_cred *unx_cred = container_of(head, struct unx_cred, uc_base.cr_rcu);
    unx_free_cred(unx_cred);
}

static void
unx_destroy_cred(struct rpc_cred *cred)
{
    call_rcu(&cred->cr_rcu, unx_free_cred_callback);
}

/*
 * Match credentials against current process creds.
 * The root_override argument takes care of cases where the caller may
 * request root creds (e.g. for NFS swapping).
 */
static int
unx_match(struct auth_cred *acred, struct rpc_cred *rcred, int flags)
{
    struct unx_cred *cred = container_of(rcred, struct unx_cred, uc_base);
    unsigned int groups = 0;
    unsigned int i;


    if (cred->uc_uid != acred->uid || cred->uc_gid != acred->gid)
        return 0;

    if (acred->group_info != NULL)
        groups = acred->group_info->ngroups;
    if (groups > NFS_NGROUPS)
        groups = NFS_NGROUPS;
    for (i = 0; i < groups ; i++) {
        gid_t gid;
        gid = from_kgid(&init_user_ns, GROUP_AT(acred->group_info, i));
        if (cred->uc_gids[i] != gid)
            return 0;
    }
    if (groups < NFS_NGROUPS &&
        cred->uc_gids[groups] != NOGROUP)
        return 0;
    return 1;
}

/*
 * Marshal credentials.
 * Maybe we should keep a cached credential for performance reasons.
 */
static __be32 *
unx_marshal(struct rpc_task *task, __be32 *p)
{
    struct rpc_clnt *clnt = task->tk_client;
    struct unx_cred *cred = container_of(task->tk_rqstp->rq_cred, struct unx_cred, uc_base);
    __be32      *base, *hold;
    int     i;

    *p++ = htonl(RPC_AUTH_UNIX);
    base = p++;
    *p++ = htonl(jiffies/HZ);

    /*
     * Copy the UTS nodename captured when the client was created.
     */
    p = xdr_encode_array(p, clnt->cl_nodename, clnt->cl_nodelen);

    *p++ = htonl((u32) cred->uc_uid);
    *p++ = htonl((u32) cred->uc_gid);
    hold = p++;
    for (i = 0; i < 16 && cred->uc_gids[i] != (gid_t) NOGROUP; i++)
        *p++ = htonl((u32) cred->uc_gids[i]);
    *hold = htonl(p - hold - 1);        /* gid array length */
    *base = htonl((p - base - 1) << 2); /* cred length */

    *p++ = htonl(RPC_AUTH_NULL);
    *p++ = htonl(0);

    return p;
}

/*
 * Refresh credentials. This is a no-op for AUTH_UNIX
 */
static int
unx_refresh(struct rpc_task *task)
{
    set_bit(RPCAUTH_CRED_UPTODATE, &task->tk_rqstp->rq_cred->cr_flags);
    return 0;
}

static __be32 *
unx_validate(struct rpc_task *task, __be32 *p)
{
    rpc_authflavor_t    flavor;
    u32         size;

    flavor = ntohl(*p++);
    if (flavor != RPC_AUTH_NULL &&
        flavor != RPC_AUTH_UNIX &&
        flavor != RPC_AUTH_SHORT) {
        printk("RPC: bad verf flavor: %u\n", flavor);
        return NULL;
    }

    size = ntohl(*p++);
    if (size > RPC_MAX_AUTH_SIZE) {
        printk("RPC: giant verf size: %u\n", size);
        return NULL;
    }
    task->tk_rqstp->rq_cred->cr_auth->au_rslack = (size >> 2) + 2;
    p += (size >> 2);

    return p;
}

int __init rpc_init_authunix(void)
{
    return rpcauth_init_credcache(&unix_auth);
}

void rpc_destroy_authunix(void)
{
    rpcauth_destroy_credcache(&unix_auth);
}

const struct rpc_authops authunix_ops = {
    .owner      = THIS_MODULE,
    .au_flavor  = RPC_AUTH_UNIX,
    .au_name    = "UNIX",
    .create     = unx_create,
    .destroy    = unx_destroy,
    .lookup_cred    = unx_lookup_cred,
    .crcreate   = unx_create_cred,
};

static
struct rpc_auth     unix_auth = {
    .au_cslack  = UNX_WRITESLACK,
    .au_rslack  = 2,            /* assume AUTH_NULL verf */
    .au_ops     = &authunix_ops,
    .au_flavor  = RPC_AUTH_UNIX,
    .au_count   = ATOMIC_INIT(0),
};

static
const struct rpc_credops unix_credops = {
    .cr_name    = "AUTH_UNIX",
    .crdestroy  = unx_destroy_cred,
    .crbind     = rpcauth_generic_bind_cred,
    .crmatch    = unx_match,
    .crmarshal  = unx_marshal,
    .crrefresh  = unx_refresh,
    .crvalidate = unx_validate,
};