/*
 * Cryptographic API.
 *
 * RNG operations.
 *
 * Copyright (c) 2008 Neil Horman <nhorman@tuxdriver.com>
 * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 */

#include <linux/atomic.h>
#include <crypto/internal/rng.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/random.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/cryptouser.h>
#include <net/netlink.h>

#include "internal.h"

static DEFINE_MUTEX(crypto_default_rng_lock);
struct crypto_rng *crypto_default_rng;
EXPORT_SYMBOL_GPL(crypto_default_rng);
static int crypto_default_rng_refcnt;

static inline struct crypto_rng *__crypto_rng_cast(struct crypto_tfm *tfm)
{
        return container_of(tfm, struct crypto_rng, base);
}

int crypto_rng_reset(struct crypto_rng *tfm, const u8 *seed, unsigned int slen)
{
        u8 *buf = NULL;
        int err;

        if (!seed && slen) {
                buf = kmalloc(slen, GFP_KERNEL);
                if (!buf)
                        return -ENOMEM;

                get_random_bytes(buf, slen);
                seed = buf;
        }

        err = crypto_rng_alg(tfm)->seed(tfm, seed, slen);

        kzfree(buf);
        return err;
}
EXPORT_SYMBOL_GPL(crypto_rng_reset);

static int crypto_rng_init_tfm(struct crypto_tfm *tfm)
{
        return 0;
}

static unsigned int seedsize(struct crypto_alg *alg)
{
        struct rng_alg *ralg = container_of(alg, struct rng_alg, base);

        return ralg->seedsize;
}

#ifdef CONFIG_NET
static int crypto_rng_report(struct sk_buff *skb, struct crypto_alg *alg)
{
        struct crypto_report_rng rrng;

        strncpy(rrng.type, "rng", sizeof(rrng.type));

        rrng.seedsize = seedsize(alg);

        if (nla_put(skb, CRYPTOCFGA_REPORT_RNG,
                    sizeof(struct crypto_report_rng), &rrng))
                goto nla_put_failure;
        return 0;

nla_put_failure:
        return -EMSGSIZE;
}
#else
static int crypto_rng_report(struct sk_buff *skb, struct crypto_alg *alg)
{
        return -ENOSYS;
}
#endif

static void crypto_rng_show(struct seq_file *m, struct crypto_alg *alg)
        __attribute__ ((unused));
static void crypto_rng_show(struct seq_file *m, struct crypto_alg *alg)
{
        seq_printf(m, "type         : rng\n");
        seq_printf(m, "seedsize     : %u\n", seedsize(alg));
}

static const struct crypto_type crypto_rng_type = {
        .extsize = crypto_alg_extsize,
        .init_tfm = crypto_rng_init_tfm,
#ifdef CONFIG_PROC_FS
        .show = crypto_rng_show,
#endif
        .report = crypto_rng_report,
        .maskclear = ~CRYPTO_ALG_TYPE_MASK,
        .maskset = CRYPTO_ALG_TYPE_MASK,
        .type = CRYPTO_ALG_TYPE_RNG,
        .tfmsize = offsetof(struct crypto_rng, base),
};

struct crypto_rng *crypto_alloc_rng(const char *alg_name, u32 type, u32 mask)
{
        return crypto_alloc_tfm(alg_name, &crypto_rng_type, type, mask);
}
EXPORT_SYMBOL_GPL(crypto_alloc_rng);

int crypto_get_default_rng(void)
{
        struct crypto_rng *rng;
        int err;

        mutex_lock(&crypto_default_rng_lock);
        if (!crypto_default_rng) {
                rng = crypto_alloc_rng("stdrng", 0, 0);
                err = PTR_ERR(rng);
                if (IS_ERR(rng))
                        goto unlock;

                err = crypto_rng_reset(rng, NULL, crypto_rng_seedsize(rng));
                if (err) {
                        crypto_free_rng(rng);
                        goto unlock;
                }

                crypto_default_rng = rng;
        }

        crypto_default_rng_refcnt++;
        err = 0;

unlock:
        mutex_unlock(&crypto_default_rng_lock);

        return err;
}
EXPORT_SYMBOL_GPL(crypto_get_default_rng);

void crypto_put_default_rng(void)
{
        mutex_lock(&crypto_default_rng_lock);
        crypto_default_rng_refcnt--;
        mutex_unlock(&crypto_default_rng_lock);
}
EXPORT_SYMBOL_GPL(crypto_put_default_rng);

#if defined(CONFIG_CRYPTO_RNG) || defined(CONFIG_CRYPTO_RNG_MODULE)
int crypto_del_default_rng(void)
{
        int err = -EBUSY;

        mutex_lock(&crypto_default_rng_lock);
        if (crypto_default_rng_refcnt)
                goto out;

        crypto_free_rng(crypto_default_rng);
        crypto_default_rng = NULL;

        err = 0;

out:
        mutex_unlock(&crypto_default_rng_lock);

        return err;
}
EXPORT_SYMBOL_GPL(crypto_del_default_rng);
#endif

int crypto_register_rng(struct rng_alg *alg)
{
        struct crypto_alg *base = &alg->base;

        if (alg->seedsize > PAGE_SIZE / 8)
                return -EINVAL;

        base->cra_type = &crypto_rng_type;
        base->cra_flags &= ~CRYPTO_ALG_TYPE_MASK;
        base->cra_flags |= CRYPTO_ALG_TYPE_RNG;

        return crypto_register_alg(base);
}
EXPORT_SYMBOL_GPL(crypto_register_rng);

void crypto_unregister_rng(struct rng_alg *alg)
{
        crypto_unregister_alg(&alg->base);
}
EXPORT_SYMBOL_GPL(crypto_unregister_rng);

int crypto_register_rngs(struct rng_alg *algs, int count)
{
        int i, ret;

        for (i = 0; i < count; i++) {
                ret = crypto_register_rng(algs + i);
                if (ret)
                        goto err;
        }

        return 0;

err:
        for (--i; i >= 0; --i)
                crypto_unregister_rng(algs + i);

        return ret;
}
EXPORT_SYMBOL_GPL(crypto_register_rngs);

void crypto_unregister_rngs(struct rng_alg *algs, int count)
{
        int i;

        for (i = count - 1; i >= 0; --i)
                crypto_unregister_rng(algs + i);
}
EXPORT_SYMBOL_GPL(crypto_unregister_rngs);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Random Number Generator");