/*
 * RNG: Random Number Generator  algorithms under the crypto API
 *
 * 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.
 *
 */

#ifndef _CRYPTO_RNG_H
#define _CRYPTO_RNG_H

#include <linux/crypto.h>

struct crypto_rng;

/**
 * struct rng_alg - random number generator definition
 *
 * @generate:   The function defined by this variable obtains a
 *              random number. The random number generator transform
 *              must generate the random number out of the context
 *              provided with this call, plus any additional data
 *              if provided to the call.
 * @seed:       Seed or reseed the random number generator.  With the
 *              invocation of this function call, the random number
 *              generator shall become ready for generation.  If the
 *              random number generator requires a seed for setting
 *              up a new state, the seed must be provided by the
 *              consumer while invoking this function. The required
 *              size of the seed is defined with @seedsize .
 * @set_ent:    Set entropy that would otherwise be obtained from
 *              entropy source.  Internal use only.
 * @seedsize:   The seed size required for a random number generator
 *              initialization defined with this variable. Some
 *              random number generators does not require a seed
 *              as the seeding is implemented internally without
 *              the need of support by the consumer. In this case,
 *              the seed size is set to zero.
 * @base:       Common crypto API algorithm data structure.
 */
struct rng_alg {
        int (*generate)(struct crypto_rng *tfm,
                        const u8 *src, unsigned int slen,
                        u8 *dst, unsigned int dlen);
        int (*seed)(struct crypto_rng *tfm, const u8 *seed, unsigned int slen);
        void (*set_ent)(struct crypto_rng *tfm, const u8 *data,
                        unsigned int len);

        unsigned int seedsize;

        struct crypto_alg base;
};

struct crypto_rng {
        struct crypto_tfm base;
};

extern struct crypto_rng *crypto_default_rng;

int crypto_get_default_rng(void);
void crypto_put_default_rng(void);

/**
 * DOC: Random number generator API
 *
 * The random number generator API is used with the ciphers of type
 * CRYPTO_ALG_TYPE_RNG (listed as type "rng" in /proc/crypto)
 */

/**
 * crypto_alloc_rng() -- allocate RNG handle
 * @alg_name: is the cra_name / name or cra_driver_name / driver name of the
 *            message digest cipher
 * @type: specifies the type of the cipher
 * @mask: specifies the mask for the cipher
 *
 * Allocate a cipher handle for a random number generator. The returned struct
 * crypto_rng is the cipher handle that is required for any subsequent
 * API invocation for that random number generator.
 *
 * For all random number generators, this call creates a new private copy of
 * the random number generator that does not share a state with other
 * instances. The only exception is the "krng" random number generator which
 * is a kernel crypto API use case for the get_random_bytes() function of the
 * /dev/random driver.
 *
 * Return: allocated cipher handle in case of success; IS_ERR() is true in case
 *         of an error, PTR_ERR() returns the error code.
 */
struct crypto_rng *crypto_alloc_rng(const char *alg_name, u32 type, u32 mask);

static inline struct crypto_tfm *crypto_rng_tfm(struct crypto_rng *tfm)
{
        return &tfm->base;
}

/**
 * crypto_rng_alg - obtain name of RNG
 * @tfm: cipher handle
 *
 * Return the generic name (cra_name) of the initialized random number generator
 *
 * Return: generic name string
 */
static inline struct rng_alg *crypto_rng_alg(struct crypto_rng *tfm)
{
        return container_of(crypto_rng_tfm(tfm)->__crt_alg,
                            struct rng_alg, base);
}

/**
 * crypto_free_rng() - zeroize and free RNG handle
 * @tfm: cipher handle to be freed
 */
static inline void crypto_free_rng(struct crypto_rng *tfm)
{
        crypto_destroy_tfm(tfm, crypto_rng_tfm(tfm));
}

/**
 * crypto_rng_generate() - get random number
 * @tfm: cipher handle
 * @src: Input buffer holding additional data, may be NULL
 * @slen: Length of additional data
 * @dst: output buffer holding the random numbers
 * @dlen: length of the output buffer
 *
 * This function fills the caller-allocated buffer with random
 * numbers using the random number generator referenced by the
 * cipher handle.
 *
 * Return: 0 function was successful; < 0 if an error occurred
 */
static inline int crypto_rng_generate(struct crypto_rng *tfm,
                                      const u8 *src, unsigned int slen,
                                      u8 *dst, unsigned int dlen)
{
        return crypto_rng_alg(tfm)->generate(tfm, src, slen, dst, dlen);
}

/**
 * crypto_rng_get_bytes() - get random number
 * @tfm: cipher handle
 * @rdata: output buffer holding the random numbers
 * @dlen: length of the output buffer
 *
 * This function fills the caller-allocated buffer with random numbers using the
 * random number generator referenced by the cipher handle.
 *
 * Return: 0 function was successful; < 0 if an error occurred
 */
static inline int crypto_rng_get_bytes(struct crypto_rng *tfm,
                                       u8 *rdata, unsigned int dlen)
{
        return crypto_rng_generate(tfm, NULL, 0, rdata, dlen);
}

/**
 * crypto_rng_reset() - re-initialize the RNG
 * @tfm: cipher handle
 * @seed: seed input data
 * @slen: length of the seed input data
 *
 * The reset function completely re-initializes the random number generator
 * referenced by the cipher handle by clearing the current state. The new state
 * is initialized with the caller provided seed or automatically, depending
 * on the random number generator type (the ANSI X9.31 RNG requires
 * caller-provided seed, the SP800-90A DRBGs perform an automatic seeding).
 * The seed is provided as a parameter to this function call. The provided seed
 * should have the length of the seed size defined for the random number
 * generator as defined by crypto_rng_seedsize.
 *
 * Return: 0 if the setting of the key was successful; < 0 if an error occurred
 */
int crypto_rng_reset(struct crypto_rng *tfm, const u8 *seed,
                     unsigned int slen);

/**
 * crypto_rng_seedsize() - obtain seed size of RNG
 * @tfm: cipher handle
 *
 * The function returns the seed size for the random number generator
 * referenced by the cipher handle. This value may be zero if the random
 * number generator does not implement or require a reseeding. For example,
 * the SP800-90A DRBGs implement an automated reseeding after reaching a
 * pre-defined threshold.
 *
 * Return: seed size for the random number generator
 */
static inline int crypto_rng_seedsize(struct crypto_rng *tfm)
{
        return crypto_rng_alg(tfm)->seedsize;
}

#endif