/*
 * DRBG based on NIST SP800-90A
 *
 * Copyright Stephan Mueller <smueller@chronox.de>, 2014
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, and the entire permission notice in its entirety,
 *    including the disclaimer of warranties.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 *
 * ALTERNATIVELY, this product may be distributed under the terms of
 * the GNU General Public License, in which case the provisions of the GPL are
 * required INSTEAD OF the above restrictions.  (This clause is
 * necessary due to a potential bad interaction between the GPL and
 * the restrictions contained in a BSD-style copyright.)
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
 * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */

#ifndef _DRBG_H
#define _DRBG_H


#include <linux/random.h>
#include <linux/scatterlist.h>
#include <crypto/hash.h>
#include <crypto/skcipher.h>
#include <linux/module.h>
#include <linux/crypto.h>
#include <linux/slab.h>
#include <crypto/internal/rng.h>
#include <crypto/rng.h>
#include <linux/fips.h>
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/workqueue.h>

/*
 * Concatenation Helper and string operation helper
 *
 * SP800-90A requires the concatenation of different data. To avoid copying
 * buffers around or allocate additional memory, the following data structure
 * is used to point to the original memory with its size. In addition, it
 * is used to build a linked list. The linked list defines the concatenation
 * of individual buffers. The order of memory block referenced in that
 * linked list determines the order of concatenation.
 */
struct drbg_string {
        const unsigned char *buf;
        size_t len;
        struct list_head list;
};

static inline void drbg_string_fill(struct drbg_string *string,
                                    const unsigned char *buf, size_t len)
{
        string->buf = buf;
        string->len = len;
        INIT_LIST_HEAD(&string->list);
}

struct drbg_state;
typedef uint32_t drbg_flag_t;

struct drbg_core {
        drbg_flag_t flags;      /* flags for the cipher */
        __u8 statelen;          /* maximum state length */
        __u8 blocklen_bytes;    /* block size of output in bytes */
        char cra_name[CRYPTO_MAX_ALG_NAME]; /* mapping to kernel crypto API */
         /* kernel crypto API backend cipher name */
        char backend_cra_name[CRYPTO_MAX_ALG_NAME];
};

struct drbg_state_ops {
        int (*update)(struct drbg_state *drbg, struct list_head *seed,
                      int reseed);
        int (*generate)(struct drbg_state *drbg,
                        unsigned char *buf, unsigned int buflen,
                        struct list_head *addtl);
        int (*crypto_init)(struct drbg_state *drbg);
        int (*crypto_fini)(struct drbg_state *drbg);

};

struct drbg_test_data {
        struct drbg_string *testentropy; /* TEST PARAMETER: test entropy */
};

struct drbg_state {
        struct mutex drbg_mutex;        /* lock around DRBG */
        unsigned char *V;       /* internal state 10.1.1.1 1a) */
        unsigned char *Vbuf;
        /* hash: static value 10.1.1.1 1b) hmac / ctr: key */
        unsigned char *C;
        unsigned char *Cbuf;
        /* Number of RNG requests since last reseed -- 10.1.1.1 1c) */
        size_t reseed_ctr;
        size_t reseed_threshold;
         /* some memory the DRBG can use for its operation */
        unsigned char *scratchpad;
        unsigned char *scratchpadbuf;
        void *priv_data;        /* Cipher handle */

        struct crypto_skcipher *ctr_handle;     /* CTR mode cipher handle */
        struct skcipher_request *ctr_req;       /* CTR mode request handle */
        __u8 *outscratchpadbuf;                 /* CTR mode output scratchpad */
        __u8 *outscratchpad;                    /* CTR mode aligned outbuf */
        struct crypto_wait ctr_wait;            /* CTR mode async wait obj */
        struct scatterlist sg_in, sg_out;       /* CTR mode SGLs */

        bool seeded;            /* DRBG fully seeded? */
        bool pr;                /* Prediction resistance enabled? */
        struct work_struct seed_work;   /* asynchronous seeding support */
        struct crypto_rng *jent;
        const struct drbg_state_ops *d_ops;
        const struct drbg_core *core;
        struct drbg_string test_data;
        struct random_ready_callback random_ready;
};

static inline __u8 drbg_statelen(struct drbg_state *drbg)
{
        if (drbg && drbg->core)
                return drbg->core->statelen;
        return 0;
}

static inline __u8 drbg_blocklen(struct drbg_state *drbg)
{
        if (drbg && drbg->core)
                return drbg->core->blocklen_bytes;
        return 0;
}

static inline __u8 drbg_keylen(struct drbg_state *drbg)
{
        if (drbg && drbg->core)
                return (drbg->core->statelen - drbg->core->blocklen_bytes);
        return 0;
}

static inline size_t drbg_max_request_bytes(struct drbg_state *drbg)
{
        /* SP800-90A requires the limit 2**19 bits, but we return bytes */
        return (1 << 16);
}

static inline size_t drbg_max_addtl(struct drbg_state *drbg)
{
        /* SP800-90A requires 2**35 bytes additional info str / pers str */
#if (__BITS_PER_LONG == 32)
        /*
         * SP800-90A allows smaller maximum numbers to be returned -- we
         * return SIZE_MAX - 1 to allow the verification of the enforcement
         * of this value in drbg_healthcheck_sanity.
         */
        return (SIZE_MAX - 1);
#else
        return (1UL<<35);
#endif
}

static inline size_t drbg_max_requests(struct drbg_state *drbg)
{
        /* SP800-90A requires 2**48 maximum requests before reseeding */
#if (__BITS_PER_LONG == 32)
        return SIZE_MAX;
#else
        return (1UL<<48);
#endif
}

/*
 * This is a wrapper to the kernel crypto API function of
 * crypto_rng_generate() to allow the caller to provide additional data.
 *
 * @drng DRBG handle -- see crypto_rng_get_bytes
 * @outbuf output buffer -- see crypto_rng_get_bytes
 * @outlen length of output buffer -- see crypto_rng_get_bytes
 * @addtl_input additional information string input buffer
 * @addtllen length of additional information string buffer
 *
 * return
 *      see crypto_rng_get_bytes
 */
static inline int crypto_drbg_get_bytes_addtl(struct crypto_rng *drng,
                        unsigned char *outbuf, unsigned int outlen,
                        struct drbg_string *addtl)
{
        return crypto_rng_generate(drng, addtl->buf, addtl->len,
                                   outbuf, outlen);
}

/*
 * TEST code
 *
 * This is a wrapper to the kernel crypto API function of
 * crypto_rng_generate() to allow the caller to provide additional data and
 * allow furnishing of test_data
 *
 * @drng DRBG handle -- see crypto_rng_get_bytes
 * @outbuf output buffer -- see crypto_rng_get_bytes
 * @outlen length of output buffer -- see crypto_rng_get_bytes
 * @addtl_input additional information string input buffer
 * @addtllen length of additional information string buffer
 * @test_data filled test data
 *
 * return
 *      see crypto_rng_get_bytes
 */
static inline int crypto_drbg_get_bytes_addtl_test(struct crypto_rng *drng,
                        unsigned char *outbuf, unsigned int outlen,
                        struct drbg_string *addtl,
                        struct drbg_test_data *test_data)
{
        crypto_rng_set_entropy(drng, test_data->testentropy->buf,
                               test_data->testentropy->len);
        return crypto_rng_generate(drng, addtl->buf, addtl->len,
                                   outbuf, outlen);
}

/*
 * TEST code
 *
 * This is a wrapper to the kernel crypto API function of
 * crypto_rng_reset() to allow the caller to provide test_data
 *
 * @drng DRBG handle -- see crypto_rng_reset
 * @pers personalization string input buffer
 * @perslen length of additional information string buffer
 * @test_data filled test data
 *
 * return
 *      see crypto_rng_reset
 */
static inline int crypto_drbg_reset_test(struct crypto_rng *drng,
                                         struct drbg_string *pers,
                                         struct drbg_test_data *test_data)
{
        crypto_rng_set_entropy(drng, test_data->testentropy->buf,
                               test_data->testentropy->len);
        return crypto_rng_reset(drng, pers->buf, pers->len);
}

/* DRBG type flags */
#define DRBG_CTR        ((drbg_flag_t)1<<0)
#define DRBG_HMAC       ((drbg_flag_t)1<<1)
#define DRBG_HASH       ((drbg_flag_t)1<<2)
#define DRBG_TYPE_MASK  (DRBG_CTR | DRBG_HMAC | DRBG_HASH)
/* DRBG strength flags */
#define DRBG_STRENGTH128        ((drbg_flag_t)1<<3)
#define DRBG_STRENGTH192        ((drbg_flag_t)1<<4)
#define DRBG_STRENGTH256        ((drbg_flag_t)1<<5)
#define DRBG_STRENGTH_MASK      (DRBG_STRENGTH128 | DRBG_STRENGTH192 | \
                                 DRBG_STRENGTH256)

enum drbg_prefixes {
        DRBG_PREFIX0 = 0x00,
        DRBG_PREFIX1,
        DRBG_PREFIX2,
        DRBG_PREFIX3
};

#endif /* _DRBG_H */