rng.c

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/*
 * Cryptographic API.
 *
 * RNG operations.
 *
 * Copyright (c) 2008 Neil Horman <[email protected]>
 *
 * 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>

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 int rngapi_reset(struct crypto_rng *tfm, 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)->rng_reset(tfm, seed, slen);

    kfree(buf);
    return err;
}

static int crypto_init_rng_ops(struct crypto_tfm *tfm, u32 type, u32 mask)
{
    struct rng_alg *alg = &tfm->__crt_alg->cra_rng;
    struct rng_tfm *ops = &tfm->crt_rng;

    ops->rng_gen_random = alg->rng_make_random;
    ops->rng_reset = rngapi_reset;

    return 0;
}

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

    snprintf(rrng.type, CRYPTO_MAX_ALG_NAME, "%s", "rng");

    rrng.seedsize = alg->cra_rng.seedsize;

    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", alg->cra_rng.seedsize);
}

static unsigned int crypto_rng_ctxsize(struct crypto_alg *alg, u32 type,
                       u32 mask)
{
    return alg->cra_ctxsize;
}

const struct crypto_type crypto_rng_type = {
    .ctxsize = crypto_rng_ctxsize,
    .init = crypto_init_rng_ops,
#ifdef CONFIG_PROC_FS
    .show = crypto_rng_show,
#endif
    .report = crypto_rng_report,
};
EXPORT_SYMBOL_GPL(crypto_rng_type);

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);
    if (!--crypto_default_rng_refcnt) {
        crypto_free_rng(crypto_default_rng);
        crypto_default_rng = NULL;
    }
    mutex_unlock(&crypto_default_rng_lock);
}
EXPORT_SYMBOL_GPL(crypto_put_default_rng);

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