/*

 * Copyright 2011-2021 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy

 * in the file LICENSE in the source distribution or at

 * https://www.openssl.org/source/license.html

 */

#include <assert.h>

#include <stdlib.h>

#include <string.h>

#include <openssl/sha.h>

#include <openssl/crypto.h>

#include <openssl/err.h>

#include <openssl/rand.h>

#include <openssl/core_dispatch.h>

#include <openssl/proverr.h>

#include "internal/thread_once.h"

#include "prov/providercommon.h"

#include "prov/provider_ctx.h"

#include "prov/provider_util.h"

#include "prov/implementations.h"

#include "drbg_local.h"

static OSSL_FUNC_rand_newctx_fn drbg_hash_new_wrapper;

static OSSL_FUNC_rand_freectx_fn drbg_hash_free;

static OSSL_FUNC_rand_instantiate_fn drbg_hash_instantiate_wrapper;

static OSSL_FUNC_rand_uninstantiate_fn drbg_hash_uninstantiate_wrapper;

static OSSL_FUNC_rand_generate_fn drbg_hash_generate_wrapper;

static OSSL_FUNC_rand_reseed_fn drbg_hash_reseed_wrapper;

static OSSL_FUNC_rand_settable_ctx_params_fn drbg_hash_settable_ctx_params;

static OSSL_FUNC_rand_set_ctx_params_fn drbg_hash_set_ctx_params;

static OSSL_FUNC_rand_gettable_ctx_params_fn drbg_hash_gettable_ctx_params;

static OSSL_FUNC_rand_get_ctx_params_fn drbg_hash_get_ctx_params;

static OSSL_FUNC_rand_verify_zeroization_fn drbg_hash_verify_zeroization;

/* 888 bits from SP800-90Ar1 10.1 table 2 */

#define HASH_PRNG_MAX_SEEDLEN    (888/8)

/* 440 bits from SP800-90Ar1 10.1 table 2 */

#define HASH_PRNG_SMALL_SEEDLEN   (440/8)

/* Determine what seedlen to use based on the block length */

#define MAX_BLOCKLEN_USING_SMALL_SEEDLEN (256/8)

#define INBYTE_IGNORE ((unsigned char)0xFF)

typedef struct rand_drbg_hash_st {

    PROV_DIGEST digest;

    EVP_MD_CTX *ctx;

    size_t blocklen;

    unsigned char V[HASH_PRNG_MAX_SEEDLEN];

    unsigned char C[HASH_PRNG_MAX_SEEDLEN];

    /* Temporary value storage: should always exceed max digest length */

    unsigned char vtmp[HASH_PRNG_MAX_SEEDLEN];

} PROV_DRBG_HASH;

/*

 * SP800-90Ar1 10.3.1 Derivation function using a Hash Function (Hash_df).

 * The input string used is composed of:

 *    inbyte - An optional leading byte (ignore if equal to INBYTE_IGNORE)

 *    in - input string 1 (A Non NULL value).

 *    in2 - optional input string (Can be NULL).

 *    in3 - optional input string (Can be NULL).

 *    These are concatenated as part of the DigestUpdate process.

 */

static int hash_df(PROV_DRBG *drbg, unsigned char *out,

                   const unsigned char inbyte,

                   const unsigned char *in, size_t inlen,

                   const unsigned char *in2, size_t in2len,

                   const unsigned char *in3, size_t in3len)

{

    PROV_DRBG_HASH *hash = (PROV_DRBG_HASH *)drbg->data;

    EVP_MD_CTX *ctx = hash->ctx;

    unsigned char *vtmp = hash->vtmp;

    /* tmp = counter || num_bits_returned || [inbyte] */

    unsigned char tmp[1 + 4 + 1];

    int tmp_sz = 0;

    size_t outlen = drbg->seedlen;

    size_t num_bits_returned = outlen * 8;

    /*

     * No need to check outlen size here, as the standard only ever needs

     * seedlen bytes which is always less than the maximum permitted.

     */

    /* (Step 3) counter = 1 (tmp[0] is the 8 bit counter) */

    tmp[tmp_sz++] = 1;

    /* tmp[1..4] is the fixed 32 bit no_of_bits_to_return */

    tmp[tmp_sz++] = (unsigned char)((num_bits_returned >> 24) & 0xff);

    tmp[tmp_sz++] = (unsigned char)((num_bits_returned >> 16) & 0xff);

    tmp[tmp_sz++] = (unsigned char)((num_bits_returned >> 8) & 0xff);

    tmp[tmp_sz++] = (unsigned char)(num_bits_returned & 0xff);

    /* Tack the additional input byte onto the end of tmp if it exists */

    if (inbyte != INBYTE_IGNORE)

        tmp[tmp_sz++] = inbyte;

    /* (Step 4) */

    for (;;) {

        /*

         * (Step 4.1) out = out || Hash(tmp || in || [in2] || [in3])

         *            (where tmp = counter || num_bits_returned || [inbyte])

         */

        if (!(EVP_DigestInit_ex(ctx, ossl_prov_digest_md(&hash->digest), NULL)

                && EVP_DigestUpdate(ctx, tmp, tmp_sz)

                && EVP_DigestUpdate(ctx, in, inlen)

                && (in2 == NULL || EVP_DigestUpdate(ctx, in2, in2len))

                && (in3 == NULL || EVP_DigestUpdate(ctx, in3, in3len))))

            return 0;

        if (outlen < hash->blocklen) {

            if (!EVP_DigestFinal(ctx, vtmp, NULL))

                return 0;

            memcpy(out, vtmp, outlen);

            OPENSSL_cleanse(vtmp, hash->blocklen);

            break;

        } else if(!EVP_DigestFinal(ctx, out, NULL)) {

            return 0;

        }

        outlen -= hash->blocklen;

        if (outlen == 0)

            break;

        /* (Step 4.2) counter++ */

        tmp[0]++;

        out += hash->blocklen;

    }

    return 1;

}

/* Helper function that just passes 2 input parameters to hash_df() */

static int hash_df1(PROV_DRBG *drbg, unsigned char *out,

                    const unsigned char in_byte,

                    const unsigned char *in1, size_t in1len)

{

    return hash_df(drbg, out, in_byte, in1, in1len, NULL, 0, NULL, 0);

}

/*

 * Add 2 byte buffers together. The first elements in each buffer are the top

 * most bytes. The result is stored in the dst buffer.

 * The final carry is ignored i.e: dst =  (dst + in) mod (2^seedlen_bits).

 * where dst size is drbg->seedlen, and inlen <= drbg->seedlen.

 */

static int add_bytes(PROV_DRBG *drbg, unsigned char *dst,

                     unsigned char *in, size_t inlen)

{

    size_t i;

    int result;

    const unsigned char *add;

    unsigned char carry = 0, *d;

    assert(drbg->seedlen >= 1 && inlen >= 1 && inlen <= drbg->seedlen);

    d = &dst[drbg->seedlen - 1];

    add = &in[inlen - 1];

    for (i = inlen; i > 0; i--, d--, add--) {

        result = *d + *add + carry;

        carry = (unsigned char)(result >> 8);

        *d = (unsigned char)(result & 0xff);

    }

    if (carry != 0) {

        /* Add the carry to the top of the dst if inlen is not the same size */

        for (i = drbg->seedlen - inlen; i > 0; --i, d--) {

            *d += 1;     /* Carry can only be 1 */

            if (*d != 0) /* exit if carry doesnt propagate to the next byte */

                break;

        }

    }

    return 1;

}

/* V = (V + Hash(inbyte || V  || [additional_input]) mod (2^seedlen) */

static int add_hash_to_v(PROV_DRBG *drbg, unsigned char inbyte,

                         const unsigned char *adin, size_t adinlen)

{

    PROV_DRBG_HASH *hash = (PROV_DRBG_HASH *)drbg->data;

    EVP_MD_CTX *ctx = hash->ctx;

    return EVP_DigestInit_ex(ctx, ossl_prov_digest_md(&hash->digest), NULL)

           && EVP_DigestUpdate(ctx, &inbyte, 1)

           && EVP_DigestUpdate(ctx, hash->V, drbg->seedlen)

           && (adin == NULL || EVP_DigestUpdate(ctx, adin, adinlen))

           && EVP_DigestFinal(ctx, hash->vtmp, NULL)

           && add_bytes(drbg, hash->V, hash->vtmp, hash->blocklen);

}

/*

 * The Hashgen() as listed in SP800-90Ar1 10.1.1.4 Hash_DRBG_Generate_Process.

 *

 * drbg contains the current value of V.

 * outlen is the requested number of bytes.

 * out is a buffer to return the generated bits.

 *

 * The algorithm to generate the bits is:

 *     data = V

 *     w = NULL

 *     for (i = 1 to m) {

 *        W = W || Hash(data)

 *        data = (data + 1) mod (2^seedlen)

 *     }

 *     out = Leftmost(W, outlen)

 *

 * Returns zero if an error occurs otherwise it returns 1.

 */

static int hash_gen(PROV_DRBG *drbg, unsigned char *out, size_t outlen)

{

    PROV_DRBG_HASH *hash = (PROV_DRBG_HASH *)drbg->data;

    unsigned char one = 1;

    if (outlen == 0)

        return 1;

    memcpy(hash->vtmp, hash->V, drbg->seedlen);

    for(;;) {

        if (!EVP_DigestInit_ex(hash->ctx, ossl_prov_digest_md(&hash->digest),

                               NULL)

                || !EVP_DigestUpdate(hash->ctx, hash->vtmp, drbg->seedlen))

            return 0;

        if (outlen < hash->blocklen) {

            if (!EVP_DigestFinal(hash->ctx, hash->vtmp, NULL))

                return 0;

            memcpy(out, hash->vtmp, outlen);

            return 1;

        } else {

            if (!EVP_DigestFinal(hash->ctx, out, NULL))

                return 0;

            outlen -= hash->blocklen;

            if (outlen == 0)

                break;

            out += hash->blocklen;

        }

        add_bytes(drbg, hash->vtmp, &one, 1);

    }

    return 1;

}

/*

 * SP800-90Ar1 10.1.1.2 Hash_DRBG_Instantiate_Process:

 *

 * ent is entropy input obtained from a randomness source of length ent_len.

 * nonce is a string of bytes of length nonce_len.

 * pstr is a personalization string received from an application. May be NULL.

 *

 * Returns zero if an error occurs otherwise it returns 1.

 */

static int drbg_hash_instantiate(PROV_DRBG *drbg,

                                 const unsigned char *ent, size_t ent_len,

                                 const unsigned char *nonce, size_t nonce_len,

                                 const unsigned char *pstr, size_t pstr_len)

{

    PROV_DRBG_HASH *hash = (PROV_DRBG_HASH *)drbg->data;

    EVP_MD_CTX_free(hash->ctx);

    hash->ctx = EVP_MD_CTX_new();

    /* (Step 1-3) V = Hash_df(entropy||nonce||pers, seedlen) */

    return hash->ctx != NULL

           && hash_df(drbg, hash->V, INBYTE_IGNORE,

                      ent, ent_len, nonce, nonce_len, pstr, pstr_len)

           /* (Step 4) C = Hash_df(0x00||V, seedlen) */

           && hash_df1(drbg, hash->C, 0x00, hash->V, drbg->seedlen);

}

static int drbg_hash_instantiate_wrapper(void *vdrbg, unsigned int strength,

                                         int prediction_resistance,

                                         const unsigned char *pstr,

                                         size_t pstr_len,

                                         const OSSL_PARAM params[])

{

    PROV_DRBG *drbg = (PROV_DRBG *)vdrbg;

    if (!ossl_prov_is_running() || !drbg_hash_set_ctx_params(drbg, params))

        return 0;

    return ossl_prov_drbg_instantiate(drbg, strength, prediction_resistance,

                                      pstr, pstr_len);

}

/*

 * SP800-90Ar1 10.1.1.3 Hash_DRBG_Reseed_Process:

 *

 * ent is entropy input bytes obtained from a randomness source.

 * addin is additional input received from an application. May be NULL.

 *

 * Returns zero if an error occurs otherwise it returns 1.

 */

static int drbg_hash_reseed(PROV_DRBG *drbg,

                            const unsigned char *ent, size_t ent_len,

                            const unsigned char *adin, size_t adin_len)

{

    PROV_DRBG_HASH *hash = (PROV_DRBG_HASH *)drbg->data;

    /* (Step 1-2) V = Hash_df(0x01 || V || entropy_input || additional_input) */

    /* V about to be updated so use C as output instead */

    if (!hash_df(drbg, hash->C, 0x01, hash->V, drbg->seedlen, ent, ent_len,

                 adin, adin_len))

        return 0;

    memcpy(hash->V, hash->C, drbg->seedlen);

    /* (Step 4) C = Hash_df(0x00||V, seedlen) */

    return hash_df1(drbg, hash->C, 0x00, hash->V, drbg->seedlen);

}

static int drbg_hash_reseed_wrapper(void *vdrbg, int prediction_resistance,

                                    const unsigned char *ent, size_t ent_len,

                                    const unsigned char *adin, size_t adin_len)

{

    PROV_DRBG *drbg = (PROV_DRBG *)vdrbg;

    return ossl_prov_drbg_reseed(drbg, prediction_resistance, ent, ent_len,

                                 adin, adin_len);

}

/*

 * SP800-90Ar1 10.1.1.4 Hash_DRBG_Generate_Process:

 *

 * Generates pseudo random bytes using the drbg.

 * out is a buffer to fill with outlen bytes of pseudo random data.

 * addin is additional input received from an application. May be NULL.

 *

 * Returns zero if an error occurs otherwise it returns 1.

 */

static int drbg_hash_generate(PROV_DRBG *drbg,

                              unsigned char *out, size_t outlen,

                              const unsigned char *adin, size_t adin_len)

{

    PROV_DRBG_HASH *hash = (PROV_DRBG_HASH *)drbg->data;

    unsigned char counter[4];

    int reseed_counter = drbg->generate_counter;

    counter[0] = (unsigned char)((reseed_counter >> 24) & 0xff);

    counter[1] = (unsigned char)((reseed_counter >> 16) & 0xff);

    counter[2] = (unsigned char)((reseed_counter >> 8) & 0xff);

    counter[3] = (unsigned char)(reseed_counter & 0xff);

    return hash->ctx != NULL

           && (adin == NULL

           /* (Step 2) if adin != NULL then V = V + Hash(0x02||V||adin) */

               || adin_len == 0

               || add_hash_to_v(drbg, 0x02, adin, adin_len))

           /* (Step 3) Hashgen(outlen, V) */

           && hash_gen(drbg, out, outlen)

           /* (Step 4/5) H = V = (V + Hash(0x03||V) mod (2^seedlen_bits) */

           && add_hash_to_v(drbg, 0x03, NULL, 0)

           /* (Step 5) V = (V + H + C + reseed_counter) mod (2^seedlen_bits) */

           /* V = (V + C) mod (2^seedlen_bits) */

           && add_bytes(drbg, hash->V, hash->C, drbg->seedlen)

           /* V = (V + reseed_counter) mod (2^seedlen_bits) */

           && add_bytes(drbg, hash->V, counter, 4);

}

static int drbg_hash_generate_wrapper

    (void *vdrbg, unsigned char *out, size_t outlen, unsigned int strength,

     int prediction_resistance, const unsigned char *adin, size_t adin_len)

{

    PROV_DRBG *drbg = (PROV_DRBG *)vdrbg;

    return ossl_prov_drbg_generate(drbg, out, outlen, strength,

                                   prediction_resistance, adin, adin_len);

}

static int drbg_hash_uninstantiate(PROV_DRBG *drbg)

{

    PROV_DRBG_HASH *hash = (PROV_DRBG_HASH *)drbg->data;

    OPENSSL_cleanse(hash->V, sizeof(hash->V));

    OPENSSL_cleanse(hash->C, sizeof(hash->C));

    OPENSSL_cleanse(hash->vtmp, sizeof(hash->vtmp));

    return ossl_prov_drbg_uninstantiate(drbg);

}

static int drbg_hash_uninstantiate_wrapper(void *vdrbg)

{

    return drbg_hash_uninstantiate((PROV_DRBG *)vdrbg);

}

static int drbg_hash_verify_zeroization(void *vdrbg)

{

    PROV_DRBG *drbg = (PROV_DRBG *)vdrbg;

    PROV_DRBG_HASH *hash = (PROV_DRBG_HASH *)drbg->data;

    PROV_DRBG_VERYIFY_ZEROIZATION(hash->V);

    PROV_DRBG_VERYIFY_ZEROIZATION(hash->C);

    PROV_DRBG_VERYIFY_ZEROIZATION(hash->vtmp);

    return 1;

}

static int drbg_hash_new(PROV_DRBG *ctx)

{

    PROV_DRBG_HASH *hash;

    hash = OPENSSL_secure_zalloc(sizeof(*hash));

    if (hash == NULL) {

        ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);

        return 0;

    }

    ctx->data = hash;

    ctx->seedlen = HASH_PRNG_MAX_SEEDLEN;

    ctx->max_entropylen = DRBG_MAX_LENGTH;

    ctx->max_noncelen = DRBG_MAX_LENGTH;

    ctx->max_perslen = DRBG_MAX_LENGTH;

    ctx->max_adinlen = DRBG_MAX_LENGTH;

    /* Maximum number of bits per request = 2^19  = 2^16 bytes */

    ctx->max_request = 1 << 16;

    return 1;

}

static void *drbg_hash_new_wrapper(void *provctx, void *parent,

                                   const OSSL_DISPATCH *parent_dispatch)

{

    return ossl_rand_drbg_new(provctx, parent, parent_dispatch, &drbg_hash_new,

                              &drbg_hash_instantiate, &drbg_hash_uninstantiate,

                              &drbg_hash_reseed, &drbg_hash_generate);

}

static void drbg_hash_free(void *vdrbg)

{

    PROV_DRBG *drbg = (PROV_DRBG *)vdrbg;

    PROV_DRBG_HASH *hash;

    if (drbg != NULL && (hash = (PROV_DRBG_HASH *)drbg->data) != NULL) {

        EVP_MD_CTX_free(hash->ctx);

        ossl_prov_digest_reset(&hash->digest);

        OPENSSL_secure_clear_free(hash, sizeof(*hash));

    }

    ossl_rand_drbg_free(drbg);

}

static int drbg_hash_get_ctx_params(void *vdrbg, OSSL_PARAM params[])

{

    PROV_DRBG *drbg = (PROV_DRBG *)vdrbg;

    PROV_DRBG_HASH *hash = (PROV_DRBG_HASH *)drbg->data;

    const EVP_MD *md;

    OSSL_PARAM *p;

    p = OSSL_PARAM_locate(params, OSSL_DRBG_PARAM_DIGEST);

    if (p != NULL) {

        md = ossl_prov_digest_md(&hash->digest);

        if (md == NULL || !OSSL_PARAM_set_utf8_string(p, EVP_MD_get0_name(md)))

            return 0;

    }

    return ossl_drbg_get_ctx_params(drbg, params);

}

static const OSSL_PARAM *drbg_hash_gettable_ctx_params(ossl_unused void *vctx,

                                                       ossl_unused void *p_ctx)

{

    static const OSSL_PARAM known_gettable_ctx_params[] = {

        OSSL_PARAM_utf8_string(OSSL_DRBG_PARAM_DIGEST, NULL, 0),

        OSSL_PARAM_DRBG_GETTABLE_CTX_COMMON,

        OSSL_PARAM_END

    };

    return known_gettable_ctx_params;

}

static int drbg_hash_set_ctx_params(void *vctx, const OSSL_PARAM params[])

{

    PROV_DRBG *ctx = (PROV_DRBG *)vctx;

    PROV_DRBG_HASH *hash = (PROV_DRBG_HASH *)ctx->data;

    OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);

    const EVP_MD *md;

    if (!ossl_prov_digest_load_from_params(&hash->digest, params, libctx))

        return 0;

    md = ossl_prov_digest_md(&hash->digest);

    if (md != NULL) {

        if ((EVP_MD_get_flags(md) & EVP_MD_FLAG_XOF) != 0) {

            ERR_raise(ERR_LIB_PROV, PROV_R_XOF_DIGESTS_NOT_ALLOWED);

            return 0;

        }

        /* These are taken from SP 800-90 10.1 Table 2 */

        hash->blocklen = EVP_MD_get_size(md);

        /* See SP800-57 Part1 Rev4 5.6.1 Table 3 */

        ctx->strength = 64 * (hash->blocklen >> 3);

        if (ctx->strength > 256)

            ctx->strength = 256;

        if (hash->blocklen > MAX_BLOCKLEN_USING_SMALL_SEEDLEN)

            ctx->seedlen = HASH_PRNG_MAX_SEEDLEN;

        else

            ctx->seedlen = HASH_PRNG_SMALL_SEEDLEN;

        ctx->min_entropylen = ctx->strength / 8;

        ctx->min_noncelen = ctx->min_entropylen / 2;

    }

    return ossl_drbg_set_ctx_params(ctx, params);

}

static const OSSL_PARAM *drbg_hash_settable_ctx_params(ossl_unused void *vctx,

                                                       ossl_unused void *p_ctx)

{

    static const OSSL_PARAM known_settable_ctx_params[] = {

        OSSL_PARAM_utf8_string(OSSL_DRBG_PARAM_PROPERTIES, NULL, 0),

        OSSL_PARAM_utf8_string(OSSL_DRBG_PARAM_DIGEST, NULL, 0),

        OSSL_PARAM_DRBG_SETTABLE_CTX_COMMON,

        OSSL_PARAM_END

    };

    return known_settable_ctx_params;

}

const OSSL_DISPATCH ossl_drbg_hash_functions[] = {

    { OSSL_FUNC_RAND_NEWCTX, (void(*)(void))drbg_hash_new_wrapper },

    { OSSL_FUNC_RAND_FREECTX, (void(*)(void))drbg_hash_free },

    { OSSL_FUNC_RAND_INSTANTIATE,

      (void(*)(void))drbg_hash_instantiate_wrapper },

    { OSSL_FUNC_RAND_UNINSTANTIATE,

      (void(*)(void))drbg_hash_uninstantiate_wrapper },

    { OSSL_FUNC_RAND_GENERATE, (void(*)(void))drbg_hash_generate_wrapper },

    { OSSL_FUNC_RAND_RESEED, (void(*)(void))drbg_hash_reseed_wrapper },

    { OSSL_FUNC_RAND_ENABLE_LOCKING, (void(*)(void))ossl_drbg_enable_locking },

    { OSSL_FUNC_RAND_LOCK, (void(*)(void))ossl_drbg_lock },

    { OSSL_FUNC_RAND_UNLOCK, (void(*)(void))ossl_drbg_unlock },

    { OSSL_FUNC_RAND_SETTABLE_CTX_PARAMS,

      (void(*)(void))drbg_hash_settable_ctx_params },

    { OSSL_FUNC_RAND_SET_CTX_PARAMS, (void(*)(void))drbg_hash_set_ctx_params },

    { OSSL_FUNC_RAND_GETTABLE_CTX_PARAMS,

      (void(*)(void))drbg_hash_gettable_ctx_params },

    { OSSL_FUNC_RAND_GET_CTX_PARAMS, (void(*)(void))drbg_hash_get_ctx_params },

    { OSSL_FUNC_RAND_VERIFY_ZEROIZATION,

      (void(*)(void))drbg_hash_verify_zeroization },

    { OSSL_FUNC_RAND_GET_SEED, (void(*)(void))ossl_drbg_get_seed },

    { OSSL_FUNC_RAND_CLEAR_SEED, (void(*)(void))ossl_drbg_clear_seed },

    { 0, NULL }

};