// SPDX-License-Identifier: GPL-2.0
/*
 * 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/mempool.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/auth.h>
#include <linux/user_namespace.h>


#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 mempool_t                *unix_pool;

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

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

/*
 * Lookup AUTH_UNIX creds for current process
 */
static struct rpc_cred *
unx_lookup_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
        struct rpc_cred *ret = mempool_alloc(unix_pool, GFP_NOFS);

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

        rpcauth_init_cred(ret, acred, auth, &unix_credops);
        ret->cr_flags = 1UL << RPCAUTH_CRED_UPTODATE;
        return ret;
}

static void
unx_free_cred_callback(struct rcu_head *head)
{
        struct rpc_cred *rpc_cred = container_of(head, struct rpc_cred, cr_rcu);
        dprintk("RPC:       unx_free_cred %p\n", rpc_cred);
        put_cred(rpc_cred->cr_cred);
        mempool_free(rpc_cred, unix_pool);
}

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

/*
 * Match credentials against current the auth_cred.
 */
static int
unx_match(struct auth_cred *acred, struct rpc_cred *cred, int flags)
{
        unsigned int groups = 0;
        unsigned int i;

        if (cred->cr_cred == acred->cred)
                return 1;

        if (!uid_eq(cred->cr_cred->fsuid, acred->cred->fsuid) || !gid_eq(cred->cr_cred->fsgid, acred->cred->fsgid))
                return 0;

        if (acred->cred && acred->cred->group_info != NULL)
                groups = acred->cred->group_info->ngroups;
        if (groups > UNX_NGROUPS)
                groups = UNX_NGROUPS;
        if (cred->cr_cred->group_info == NULL)
                return groups == 0;
        if (groups != cred->cr_cred->group_info->ngroups)
                return 0;

        for (i = 0; i < groups ; i++)
                if (!gid_eq(cred->cr_cred->group_info->gid[i], acred->cred->group_info->gid[i]))
                        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 rpc_cred *cred = task->tk_rqstp->rq_cred;
        __be32          *base, *hold;
        int             i;
        struct group_info *gi = cred->cr_cred->group_info;

        *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->cr_cred->fsuid));
        *p++ = htonl((u32) from_kgid(&init_user_ns, cred->cr_cred->fsgid));
        hold = p++;
        if (gi)
                for (i = 0; i < UNX_NGROUPS && i < gi->ngroups; i++)
                        *p++ = htonl((u32) from_kgid(&init_user_ns, gi->gid[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)
{
        unix_pool = mempool_create_kmalloc_pool(16, sizeof(struct rpc_cred));
        return unix_pool ? 0 : -ENOMEM;
}

void rpc_destroy_authunix(void)
{
        mempool_destroy(unix_pool);
}

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,
};

static
struct rpc_auth         unix_auth = {
        .au_cslack      = UNX_CALLSLACK,
        .au_rslack      = NUL_REPLYSLACK,
        .au_ops         = &authunix_ops,
        .au_flavor      = RPC_AUTH_UNIX,
        .au_count       = REFCOUNT_INIT(1),
};

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