/*
 * linux/net/sunrpc/auth_unix.c
 *
 * UNIX-style authentication; no AUTH_SHORT support
 *
 * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
 */

#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>

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

#if IS_ENABLED(CONFIG_SUNRPC_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_auth_create_args *args, struct rpc_clnt *clnt)
{
        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);
}

static int
unx_hash_cred(struct auth_cred *acred, unsigned int hashbits)
{
        return hash_64(from_kgid(&init_user_ns, acred->gid) |
                ((u64)from_kuid(&init_user_ns, acred->uid) <<
                        (sizeof(gid_t) * 8)), hashbits);
}

/*
 * 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, GFP_NOFS);
}

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

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

        if (!(cred = kmalloc(sizeof(*cred), gfp)))
                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 > UNX_NGROUPS)
                groups = UNX_NGROUPS;

        cred->uc_gid = acred->gid;
        for (i = 0; i < groups; i++)
                cred->uc_gids[i] = acred->group_info->gid[i];
        if (i < UNX_NGROUPS)
                cred->uc_gids[i] = INVALID_GID;

        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 (!uid_eq(cred->uc_uid, acred->uid) || !gid_eq(cred->uc_gid, acred->gid))
                return 0;

        if (acred->group_info != NULL)
                groups = acred->group_info->ngroups;
        if (groups > UNX_NGROUPS)
                groups = UNX_NGROUPS;
        for (i = 0; i < groups ; i++)
                if (!gid_eq(cred->uc_gids[i], acred->group_info->gid[i]))
                        return 0;
        if (groups < UNX_NGROUPS && gid_valid(cred->uc_gids[groups]))
                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) from_kuid(&init_user_ns, cred->uc_uid));
        *p++ = htonl((u32) from_kgid(&init_user_ns, cred->uc_gid));
        hold = p++;
        for (i = 0; i < UNX_NGROUPS && gid_valid(cred->uc_gids[i]); i++)
                *p++ = htonl((u32) from_kgid(&init_user_ns, 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 ERR_PTR(-EIO);
        }

        size = ntohl(*p++);
        if (size > RPC_MAX_AUTH_SIZE) {
                printk("RPC: giant verf size: %u\n", size);
                return ERR_PTR(-EIO);
        }
        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,
        .hash_cred      = unx_hash_cred,
        .lookup_cred    = unx_lookup_cred,
        .crcreate       = unx_create_cred,
};

static
struct rpc_auth         unix_auth = {
        .au_cslack      = UNX_CALLSLACK,
        .au_rslack      = NUL_REPLYSLACK,
        .au_flags       = RPCAUTH_AUTH_NO_CRKEY_TIMEOUT,
        .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,
};