/*

 * Copyright 2011-2022 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 <stdlib.h>

#include <string.h>

#include <openssl/crypto.h>

#include <openssl/err.h>

#include <openssl/rand.h>

#include <openssl/aes.h>

#include <openssl/proverr.h>

#include "crypto/modes.h"

#include "internal/thread_once.h"

#include "prov/implementations.h"

#include "prov/providercommon.h"

#include "prov/provider_ctx.h"

#include "drbg_local.h"

static OSSL_FUNC_rand_newctx_fn drbg_ctr_new_wrapper;

static OSSL_FUNC_rand_freectx_fn drbg_ctr_free;

static OSSL_FUNC_rand_instantiate_fn drbg_ctr_instantiate_wrapper;

static OSSL_FUNC_rand_uninstantiate_fn drbg_ctr_uninstantiate_wrapper;

static OSSL_FUNC_rand_generate_fn drbg_ctr_generate_wrapper;

static OSSL_FUNC_rand_reseed_fn drbg_ctr_reseed_wrapper;

static OSSL_FUNC_rand_settable_ctx_params_fn drbg_ctr_settable_ctx_params;

static OSSL_FUNC_rand_set_ctx_params_fn drbg_ctr_set_ctx_params;

static OSSL_FUNC_rand_gettable_ctx_params_fn drbg_ctr_gettable_ctx_params;

static OSSL_FUNC_rand_get_ctx_params_fn drbg_ctr_get_ctx_params;

static OSSL_FUNC_rand_verify_zeroization_fn drbg_ctr_verify_zeroization;

/*

 * The state of a DRBG AES-CTR.

 */

typedef struct rand_drbg_ctr_st {

    EVP_CIPHER_CTX *ctx_ecb;

    EVP_CIPHER_CTX *ctx_ctr;

    EVP_CIPHER_CTX *ctx_df;

    EVP_CIPHER *cipher_ecb;

    EVP_CIPHER *cipher_ctr;

    size_t keylen;

    int use_df;

    unsigned char K[32];

    unsigned char V[16];

    /* Temporary block storage used by ctr_df */

    unsigned char bltmp[16];

    size_t bltmp_pos;

    unsigned char KX[48];

} PROV_DRBG_CTR;

/*

 * Implementation of NIST SP 800-90A CTR DRBG.

 */

static void inc_128(PROV_DRBG_CTR *ctr)

{

    unsigned char *p = &ctr->V[0];

    u32 n = 16, c = 1;

    do {

        --n;

        c += p[n];

        p[n] = (u8)c;

        c >>= 8;

    } while (n);

}

static void ctr_XOR(PROV_DRBG_CTR *ctr, const unsigned char *in, size_t inlen)

{

    size_t i, n;

    if (in == NULL || inlen == 0)

        return;

    /*

     * Any zero padding will have no effect on the result as we

     * are XORing. So just process however much input we have.

     */

    n = inlen < ctr->keylen ? inlen : ctr->keylen;

    for (i = 0; i < n; i++)

        ctr->K[i] ^= in[i];

    if (inlen <= ctr->keylen)

        return;

    n = inlen - ctr->keylen;

    if (n > 16) {

        /* Should never happen */

        n = 16;

    }

    for (i = 0; i < n; i++)

        ctr->V[i] ^= in[i + ctr->keylen];

}

/*

 * Process a complete block using BCC algorithm of SP 800-90A 10.3.3

 */

__owur static int ctr_BCC_block(PROV_DRBG_CTR *ctr, unsigned char *out,

                                const unsigned char *in, int len)

{

    int i, outlen = AES_BLOCK_SIZE;

    for (i = 0; i < len; i++)

        out[i] ^= in[i];

    if (!EVP_CipherUpdate(ctr->ctx_df, out, &outlen, out, len)

        || outlen != len)

        return 0;

    return 1;

}

/*

 * Handle several BCC operations for as much data as we need for K and X

 */

__owur static int ctr_BCC_blocks(PROV_DRBG_CTR *ctr, const unsigned char *in)

{

    unsigned char in_tmp[48];

    unsigned char num_of_blk = 2;

    memcpy(in_tmp, in, 16);

    memcpy(in_tmp + 16, in, 16);

    if (ctr->keylen != 16) {

        memcpy(in_tmp + 32, in, 16);

        num_of_blk = 3;

    }

    return ctr_BCC_block(ctr, ctr->KX, in_tmp, AES_BLOCK_SIZE * num_of_blk);

}

/*

 * Initialise BCC blocks: these have the value 0,1,2 in leftmost positions:

 * see 10.3.1 stage 7.

 */

__owur static int ctr_BCC_init(PROV_DRBG_CTR *ctr)

{

    unsigned char bltmp[48] = {0};

    unsigned char num_of_blk;

    memset(ctr->KX, 0, 48);

    num_of_blk = ctr->keylen == 16 ? 2 : 3;

    bltmp[(AES_BLOCK_SIZE * 1) + 3] = 1;

    bltmp[(AES_BLOCK_SIZE * 2) + 3] = 2;

    return ctr_BCC_block(ctr, ctr->KX, bltmp, num_of_blk * AES_BLOCK_SIZE);

}

/*

 * Process several blocks into BCC algorithm, some possibly partial

 */

__owur static int ctr_BCC_update(PROV_DRBG_CTR *ctr,

                                 const unsigned char *in, size_t inlen)

{

    if (in == NULL || inlen == 0)

        return 1;

    /* If we have partial block handle it first */

    if (ctr->bltmp_pos) {

        size_t left = 16 - ctr->bltmp_pos;

        /* If we now have a complete block process it */

        if (inlen >= left) {

            memcpy(ctr->bltmp + ctr->bltmp_pos, in, left);

            if (!ctr_BCC_blocks(ctr, ctr->bltmp))

                return 0;

            ctr->bltmp_pos = 0;

            inlen -= left;

            in += left;

        }

    }

    /* Process zero or more complete blocks */

    for (; inlen >= 16; in += 16, inlen -= 16) {

        if (!ctr_BCC_blocks(ctr, in))

            return 0;

    }

    /* Copy any remaining partial block to the temporary buffer */

    if (inlen > 0) {

        memcpy(ctr->bltmp + ctr->bltmp_pos, in, inlen);

        ctr->bltmp_pos += inlen;

    }

    return 1;

}

__owur static int ctr_BCC_final(PROV_DRBG_CTR *ctr)

{

    if (ctr->bltmp_pos) {

        memset(ctr->bltmp + ctr->bltmp_pos, 0, 16 - ctr->bltmp_pos);

        if (!ctr_BCC_blocks(ctr, ctr->bltmp))

            return 0;

    }

    return 1;

}

__owur static int ctr_df(PROV_DRBG_CTR *ctr,

                         const unsigned char *in1, size_t in1len,

                         const unsigned char *in2, size_t in2len,

                         const unsigned char *in3, size_t in3len)

{

    static unsigned char c80 = 0x80;

    size_t inlen;

    unsigned char *p = ctr->bltmp;

    int outlen = AES_BLOCK_SIZE;

    if (!ctr_BCC_init(ctr))

        return 0;

    if (in1 == NULL)

        in1len = 0;

    if (in2 == NULL)

        in2len = 0;

    if (in3 == NULL)

        in3len = 0;

    inlen = in1len + in2len + in3len;

    /* Initialise L||N in temporary block */

    *p++ = (inlen >> 24) & 0xff;

    *p++ = (inlen >> 16) & 0xff;

    *p++ = (inlen >> 8) & 0xff;

    *p++ = inlen & 0xff;

    /* NB keylen is at most 32 bytes */

    *p++ = 0;

    *p++ = 0;

    *p++ = 0;

    *p = (unsigned char)((ctr->keylen + 16) & 0xff);

    ctr->bltmp_pos = 8;

    if (!ctr_BCC_update(ctr, in1, in1len)

        || !ctr_BCC_update(ctr, in2, in2len)

        || !ctr_BCC_update(ctr, in3, in3len)

        || !ctr_BCC_update(ctr, &c80, 1)

        || !ctr_BCC_final(ctr))

        return 0;

    /* Set up key K */

    if (!EVP_CipherInit_ex(ctr->ctx_ecb, NULL, NULL, ctr->KX, NULL, -1))

        return 0;

    /* X follows key K */

    if (!EVP_CipherUpdate(ctr->ctx_ecb, ctr->KX, &outlen, ctr->KX + ctr->keylen,

                          AES_BLOCK_SIZE)

        || outlen != AES_BLOCK_SIZE)

        return 0;

    if (!EVP_CipherUpdate(ctr->ctx_ecb, ctr->KX + 16, &outlen, ctr->KX,

                          AES_BLOCK_SIZE)

        || outlen != AES_BLOCK_SIZE)

        return 0;

    if (ctr->keylen != 16)

        if (!EVP_CipherUpdate(ctr->ctx_ecb, ctr->KX + 32, &outlen,

                              ctr->KX + 16, AES_BLOCK_SIZE)

            || outlen != AES_BLOCK_SIZE)

            return 0;

    return 1;

}

/*

 * NB the no-df Update in SP800-90A specifies a constant input length

 * of seedlen, however other uses of this algorithm pad the input with

 * zeroes if necessary and have up to two parameters XORed together,

 * so we handle both cases in this function instead.

 */

__owur static int ctr_update(PROV_DRBG *drbg,

                             const unsigned char *in1, size_t in1len,

                             const unsigned char *in2, size_t in2len,

                             const unsigned char *nonce, size_t noncelen)

{

    PROV_DRBG_CTR *ctr = (PROV_DRBG_CTR *)drbg->data;

    int outlen = AES_BLOCK_SIZE;

    unsigned char V_tmp[48], out[48];

    unsigned char len;

    /* correct key is already set up. */

    memcpy(V_tmp, ctr->V, 16);

    inc_128(ctr);

    memcpy(V_tmp + 16, ctr->V, 16);

    if (ctr->keylen == 16) {

        len = 32;

    } else {

        inc_128(ctr);

        memcpy(V_tmp + 32, ctr->V, 16);

        len = 48;

    }

    if (!EVP_CipherUpdate(ctr->ctx_ecb, out, &outlen, V_tmp, len)

            || outlen != len)

        return 0;

    memcpy(ctr->K, out, ctr->keylen);

    memcpy(ctr->V, out + ctr->keylen, 16);

    if (ctr->use_df) {

        /* If no input reuse existing derived value */

        if (in1 != NULL || nonce != NULL || in2 != NULL)

            if (!ctr_df(ctr, in1, in1len, nonce, noncelen, in2, in2len))

                return 0;

        /* If this a reuse input in1len != 0 */

        if (in1len)

            ctr_XOR(ctr, ctr->KX, drbg->seedlen);

    } else {

        ctr_XOR(ctr, in1, in1len);

        ctr_XOR(ctr, in2, in2len);

    }

    if (!EVP_CipherInit_ex(ctr->ctx_ecb, NULL, NULL, ctr->K, NULL, -1)

        || !EVP_CipherInit_ex(ctr->ctx_ctr, NULL, NULL, ctr->K, NULL, -1))

        return 0;

    return 1;

}

static int drbg_ctr_instantiate(PROV_DRBG *drbg,

                                const unsigned char *entropy, size_t entropylen,

                                const unsigned char *nonce, size_t noncelen,

                                const unsigned char *pers, size_t perslen)

{

    PROV_DRBG_CTR *ctr = (PROV_DRBG_CTR *)drbg->data;

    if (entropy == NULL)

        return 0;

    memset(ctr->K, 0, sizeof(ctr->K));

    memset(ctr->V, 0, sizeof(ctr->V));

    if (!EVP_CipherInit_ex(ctr->ctx_ecb, NULL, NULL, ctr->K, NULL, -1))

        return 0;

    inc_128(ctr);

    if (!ctr_update(drbg, entropy, entropylen, pers, perslen, nonce, noncelen))

        return 0;

    return 1;

}

static int drbg_ctr_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_ctr_set_ctx_params(drbg, params))

        return 0;

    return ossl_prov_drbg_instantiate(drbg, strength, prediction_resistance,

                                      pstr, pstr_len);

}

static int drbg_ctr_reseed(PROV_DRBG *drbg,

                           const unsigned char *entropy, size_t entropylen,

                           const unsigned char *adin, size_t adinlen)

{

    PROV_DRBG_CTR *ctr = (PROV_DRBG_CTR *)drbg->data;

    if (entropy == NULL)

        return 0;

    inc_128(ctr);

    if (!ctr_update(drbg, entropy, entropylen, adin, adinlen, NULL, 0))

        return 0;

    return 1;

}

static int drbg_ctr_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);

}

static void ctr96_inc(unsigned char *counter)

{

    u32 n = 12, c = 1;

    do {

        --n;

        c += counter[n];

        counter[n] = (u8)c;

        c >>= 8;

    } while (n);

}

static int drbg_ctr_generate(PROV_DRBG *drbg,

                             unsigned char *out, size_t outlen,

                             const unsigned char *adin, size_t adinlen)

{

    PROV_DRBG_CTR *ctr = (PROV_DRBG_CTR *)drbg->data;

    unsigned int ctr32, blocks;

    int outl, buflen;

    if (adin != NULL && adinlen != 0) {

        inc_128(ctr);

        if (!ctr_update(drbg, adin, adinlen, NULL, 0, NULL, 0))

            return 0;

        /* This means we reuse derived value */

        if (ctr->use_df) {

            adin = NULL;

            adinlen = 1;

        }

    } else {

        adinlen = 0;

    }

    inc_128(ctr);

    if (outlen == 0) {

        inc_128(ctr);

        if (!ctr_update(drbg, adin, adinlen, NULL, 0, NULL, 0))

            return 0;

        return 1;

    }

    memset(out, 0, outlen);

    do {

        if (!EVP_CipherInit_ex(ctr->ctx_ctr,

                               NULL, NULL, NULL, ctr->V, -1))

            return 0;

        /*-

         * outlen has type size_t while EVP_CipherUpdate takes an

         * int argument and thus cannot be guaranteed to process more

         * than 2^31-1 bytes at a time. We process such huge generate

         * requests in 2^30 byte chunks, which is the greatest multiple

         * of AES block size lower than or equal to 2^31-1.

         */

        buflen = outlen > (1U << 30) ? (1U << 30) : outlen;

        blocks = (buflen + 15) / 16;

        ctr32 = GETU32(ctr->V + 12) + blocks;

        if (ctr32 < blocks) {

            /* 32-bit counter overflow into V. */

            if (ctr32 != 0) {

                blocks -= ctr32;

                buflen = blocks * 16;

                ctr32 = 0;

            }

            ctr96_inc(ctr->V);

        }

        PUTU32(ctr->V + 12, ctr32);

        if (!EVP_CipherUpdate(ctr->ctx_ctr, out, &outl, out, buflen)

            || outl != buflen)

            return 0;

        out += buflen;

        outlen -= buflen;

    } while (outlen);

    if (!ctr_update(drbg, adin, adinlen, NULL, 0, NULL, 0))

        return 0;

    return 1;

}

static int drbg_ctr_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_ctr_uninstantiate(PROV_DRBG *drbg)

{

    PROV_DRBG_CTR *ctr = (PROV_DRBG_CTR *)drbg->data;

    OPENSSL_cleanse(ctr->K, sizeof(ctr->K));

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

    OPENSSL_cleanse(ctr->bltmp, sizeof(ctr->bltmp));

    OPENSSL_cleanse(ctr->KX, sizeof(ctr->KX));

    ctr->bltmp_pos = 0;

    return ossl_prov_drbg_uninstantiate(drbg);

}

static int drbg_ctr_uninstantiate_wrapper(void *vdrbg)

{

    return drbg_ctr_uninstantiate((PROV_DRBG *)vdrbg);

}

static int drbg_ctr_verify_zeroization(void *vdrbg)

{

    PROV_DRBG *drbg = (PROV_DRBG *)vdrbg;

    PROV_DRBG_CTR *ctr = (PROV_DRBG_CTR *)drbg->data;

    PROV_DRBG_VERYIFY_ZEROIZATION(ctr->K);

    PROV_DRBG_VERYIFY_ZEROIZATION(ctr->V);

    PROV_DRBG_VERYIFY_ZEROIZATION(ctr->bltmp);

    PROV_DRBG_VERYIFY_ZEROIZATION(ctr->KX);

    if (ctr->bltmp_pos != 0)

        return 0;

    return 1;

}

static int drbg_ctr_init_lengths(PROV_DRBG *drbg)

{

    PROV_DRBG_CTR *ctr = (PROV_DRBG_CTR *)drbg->data;

    int res = 1;

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

    drbg->max_request = 1 << 16;

    if (ctr->use_df) {

        drbg->min_entropylen = 0;

        drbg->max_entropylen = DRBG_MAX_LENGTH;

        drbg->min_noncelen = 0;

        drbg->max_noncelen = DRBG_MAX_LENGTH;

        drbg->max_perslen = DRBG_MAX_LENGTH;

        drbg->max_adinlen = DRBG_MAX_LENGTH;

        if (ctr->keylen > 0) {

            drbg->min_entropylen = ctr->keylen;

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

        }

    } else {

        const size_t len = ctr->keylen > 0 ? drbg->seedlen : DRBG_MAX_LENGTH;

        drbg->min_entropylen = len;

        drbg->max_entropylen = len;

        /* Nonce not used */

        drbg->min_noncelen = 0;

        drbg->max_noncelen = 0;

        drbg->max_perslen = len;

        drbg->max_adinlen = len;

    }

    return res;

}

static int drbg_ctr_init(PROV_DRBG *drbg)

{

    PROV_DRBG_CTR *ctr = (PROV_DRBG_CTR *)drbg->data;

    size_t keylen;

    if (ctr->cipher_ctr == NULL) {

        ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_CIPHER);

        return 0;

    }

    ctr->keylen = keylen = EVP_CIPHER_get_key_length(ctr->cipher_ctr);

    if (ctr->ctx_ecb == NULL)

        ctr->ctx_ecb = EVP_CIPHER_CTX_new();

    if (ctr->ctx_ctr == NULL)

        ctr->ctx_ctr = EVP_CIPHER_CTX_new();

    if (ctr->ctx_ecb == NULL || ctr->ctx_ctr == NULL) {

        ERR_raise(ERR_LIB_PROV, ERR_R_EVP_LIB);

        goto err;

    }

    if (!EVP_CipherInit_ex(ctr->ctx_ecb,

                           ctr->cipher_ecb, NULL, NULL, NULL, 1)

        || !EVP_CipherInit_ex(ctr->ctx_ctr,

                              ctr->cipher_ctr, NULL, NULL, NULL, 1)) {

        ERR_raise(ERR_LIB_PROV, PROV_R_UNABLE_TO_INITIALISE_CIPHERS);

        goto err;

    }

    drbg->strength = keylen * 8;

    drbg->seedlen = keylen + 16;

    if (ctr->use_df) {

        /* df initialisation */

        static const unsigned char df_key[32] = {

            0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,

            0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,

            0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,

            0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f

        };

        if (ctr->ctx_df == NULL)

            ctr->ctx_df = EVP_CIPHER_CTX_new();

        if (ctr->ctx_df == NULL) {

            ERR_raise(ERR_LIB_PROV, ERR_R_EVP_LIB);

            goto err;

        }

        /* Set key schedule for df_key */

        if (!EVP_CipherInit_ex(ctr->ctx_df,

                               ctr->cipher_ecb, NULL, df_key, NULL, 1)) {

            ERR_raise(ERR_LIB_PROV, PROV_R_DERIVATION_FUNCTION_INIT_FAILED);

            goto err;

        }

    }

    return drbg_ctr_init_lengths(drbg);

err:

    EVP_CIPHER_CTX_free(ctr->ctx_ecb);

    EVP_CIPHER_CTX_free(ctr->ctx_ctr);

    ctr->ctx_ecb = ctr->ctx_ctr = NULL;

    return 0;    

}

static int drbg_ctr_new(PROV_DRBG *drbg)

{

    PROV_DRBG_CTR *ctr;

    ctr = OPENSSL_secure_zalloc(sizeof(*ctr));

    if (ctr == NULL)

        return 0;

    ctr->use_df = 1;

    drbg->data = ctr;

    return drbg_ctr_init_lengths(drbg);

}

static void *drbg_ctr_new_wrapper(void *provctx, void *parent,

                                   const OSSL_DISPATCH *parent_dispatch)

{

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

                              &drbg_ctr_instantiate, &drbg_ctr_uninstantiate,

                              &drbg_ctr_reseed, &drbg_ctr_generate);

}

static void drbg_ctr_free(void *vdrbg)

{

    PROV_DRBG *drbg = (PROV_DRBG *)vdrbg;

    PROV_DRBG_CTR *ctr;

    if (drbg != NULL && (ctr = (PROV_DRBG_CTR *)drbg->data) != NULL) {

        EVP_CIPHER_CTX_free(ctr->ctx_ecb);

        EVP_CIPHER_CTX_free(ctr->ctx_ctr);

        EVP_CIPHER_CTX_free(ctr->ctx_df);

        EVP_CIPHER_free(ctr->cipher_ecb);

        EVP_CIPHER_free(ctr->cipher_ctr);

        OPENSSL_secure_clear_free(ctr, sizeof(*ctr));

    }

    ossl_rand_drbg_free(drbg);

}

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

{

    PROV_DRBG *drbg = (PROV_DRBG *)vdrbg;

    PROV_DRBG_CTR *ctr = (PROV_DRBG_CTR *)drbg->data;

    OSSL_PARAM *p;

    p = OSSL_PARAM_locate(params, OSSL_DRBG_PARAM_USE_DF);

    if (p != NULL && !OSSL_PARAM_set_int(p, ctr->use_df))

        return 0;

    p = OSSL_PARAM_locate(params, OSSL_DRBG_PARAM_CIPHER);

    if (p != NULL) {

        if (ctr->cipher_ctr == NULL

            || !OSSL_PARAM_set_utf8_string(p,

                                           EVP_CIPHER_get0_name(ctr->cipher_ctr)))

            return 0;

    }

    return ossl_drbg_get_ctx_params(drbg, params);

}

static const OSSL_PARAM *drbg_ctr_gettable_ctx_params(ossl_unused void *vctx,

                                                      ossl_unused void *provctx)

{

    static const OSSL_PARAM known_gettable_ctx_params[] = {

        OSSL_PARAM_utf8_string(OSSL_DRBG_PARAM_CIPHER, NULL, 0),

        OSSL_PARAM_int(OSSL_DRBG_PARAM_USE_DF, NULL),

        OSSL_PARAM_DRBG_GETTABLE_CTX_COMMON,

        OSSL_PARAM_END

    };

    return known_gettable_ctx_params;

}

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

{

    PROV_DRBG *ctx = (PROV_DRBG *)vctx;

    PROV_DRBG_CTR *ctr = (PROV_DRBG_CTR *)ctx->data;

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

    const OSSL_PARAM *p;

    char *ecb;

    const char *propquery = NULL;

    int i, cipher_init = 0;

    if ((p = OSSL_PARAM_locate_const(params, OSSL_DRBG_PARAM_USE_DF)) != NULL

            && OSSL_PARAM_get_int(p, &i)) {

        /* FIPS errors out in the drbg_ctr_init() call later */

        ctr->use_df = i != 0;

        cipher_init = 1;

    }

    if ((p = OSSL_PARAM_locate_const(params,

                                     OSSL_DRBG_PARAM_PROPERTIES)) != NULL) {

        if (p->data_type != OSSL_PARAM_UTF8_STRING)

            return 0;

        propquery = (const char *)p->data;

    }

    if ((p = OSSL_PARAM_locate_const(params, OSSL_DRBG_PARAM_CIPHER)) != NULL) {

        const char *base = (const char *)p->data;

        size_t ctr_str_len = sizeof("CTR") - 1;

        size_t ecb_str_len = sizeof("ECB") - 1;

        if (p->data_type != OSSL_PARAM_UTF8_STRING

                || p->data_size < ctr_str_len)

            return 0;

        if (OPENSSL_strcasecmp("CTR", base + p->data_size - ctr_str_len) != 0) {

            ERR_raise(ERR_LIB_PROV, PROV_R_REQUIRE_CTR_MODE_CIPHER);

            return 0;

        }

        if ((ecb = OPENSSL_strndup(base, p->data_size)) == NULL)

            return 0;

        strcpy(ecb + p->data_size - ecb_str_len, "ECB");

        EVP_CIPHER_free(ctr->cipher_ecb);

        EVP_CIPHER_free(ctr->cipher_ctr);

        ctr->cipher_ctr = EVP_CIPHER_fetch(libctx, base, propquery);

        ctr->cipher_ecb = EVP_CIPHER_fetch(libctx, ecb, propquery);

        OPENSSL_free(ecb);

        if (ctr->cipher_ctr == NULL || ctr->cipher_ecb == NULL) {

            ERR_raise(ERR_LIB_PROV, PROV_R_UNABLE_TO_FIND_CIPHERS);

            return 0;

        }

        cipher_init = 1;

    }

    if (cipher_init && !drbg_ctr_init(ctx))

        return 0;

    return ossl_drbg_set_ctx_params(ctx, params);

}

static const OSSL_PARAM *drbg_ctr_settable_ctx_params(ossl_unused void *vctx,

                                                      ossl_unused void *provctx)

{

    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_CIPHER, NULL, 0),

        OSSL_PARAM_int(OSSL_DRBG_PARAM_USE_DF, NULL),

        OSSL_PARAM_DRBG_SETTABLE_CTX_COMMON,

        OSSL_PARAM_END

    };

    return known_settable_ctx_params;

}

const OSSL_DISPATCH ossl_drbg_ctr_functions[] = {

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

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

    { OSSL_FUNC_RAND_INSTANTIATE,

      (void(*)(void))drbg_ctr_instantiate_wrapper },

    { OSSL_FUNC_RAND_UNINSTANTIATE,

      (void(*)(void))drbg_ctr_uninstantiate_wrapper },

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

    { OSSL_FUNC_RAND_RESEED, (void(*)(void))drbg_ctr_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_ctr_settable_ctx_params },

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

    { OSSL_FUNC_RAND_GETTABLE_CTX_PARAMS,

      (void(*)(void))drbg_ctr_gettable_ctx_params },

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

    { OSSL_FUNC_RAND_VERIFY_ZEROIZATION,

      (void(*)(void))drbg_ctr_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 }

};