crypto/rand/drbg_hash.c - third_party/openssl - Git at Google

 /*
  * Copyright 2011-2018 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/crypto.h>
 #include <openssl/err.h>
 #include <openssl/rand.h>
 #include "internal/thread_once.h"
 #include "prov/providercommon.h"
 #include "rand_local.h"

 /* 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)


 /*
  * 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(RAND_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)
 {
     RAND_DRBG_HASH *hash = &drbg->data.hash;
     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, hash->md, 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(RAND_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(RAND_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(RAND_DRBG *drbg, unsigned char inbyte,
                          const unsigned char *adin, size_t adinlen)
 {
     RAND_DRBG_HASH *hash = &drbg->data.hash;
     EVP_MD_CTX *ctx = hash->ctx;

     return EVP_DigestInit_ex(ctx, hash->md, 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(RAND_DRBG *drbg, unsigned char *out, size_t outlen)
 {
     RAND_DRBG_HASH *hash = &drbg->data.hash;
     unsigned char one = 1;

     if (outlen == 0)
         return 1;
     memcpy(hash->vtmp, hash->V, drbg->seedlen);
     for(;;) {
         if (!EVP_DigestInit_ex(hash->ctx, hash->md, 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(RAND_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)
 {
     RAND_DRBG_HASH *hash = &drbg->data.hash;

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

 /*
  * 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(RAND_DRBG *drbg,
                             const unsigned char *ent, size_t ent_len,
                             const unsigned char *adin, size_t adin_len)
 {
     RAND_DRBG_HASH *hash = &drbg->data.hash;

     /* (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);
 }

 /*
  * 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(RAND_DRBG *drbg,
                               unsigned char *out, size_t outlen,
                               const unsigned char *adin, size_t adin_len)
 {
     RAND_DRBG_HASH *hash = &drbg->data.hash;
     unsigned char counter[4];
     int reseed_counter = drbg->reseed_gen_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 (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_uninstantiate(RAND_DRBG *drbg)
 {
     EVP_MD_free(drbg->data.hash.md);
     EVP_MD_CTX_free(drbg->data.hash.ctx);
     OPENSSL_cleanse(&drbg->data.hash, sizeof(drbg->data.hash));
     return 1;
 }

 static RAND_DRBG_METHOD drbg_hash_meth = {
     drbg_hash_instantiate,
     drbg_hash_reseed,
     drbg_hash_generate,
     drbg_hash_uninstantiate
 };

 int drbg_hash_init(RAND_DRBG *drbg)
 {
     EVP_MD *md;
     RAND_DRBG_HASH *hash = &drbg->data.hash;

     /*
      * Confirm digest is allowed. We allow all digests that are not XOF
      * (such as SHAKE).  In FIPS mode, the fetch will fail for non-approved
      * digests.
      */
     md = EVP_MD_fetch(drbg->libctx, ossl_prov_util_nid_to_name(drbg->type), "");
     if (md == NULL)
         return 0;

     if ((EVP_MD_flags(md) & EVP_MD_FLAG_XOF) != 0)
         return 0;

     drbg->meth = &drbg_hash_meth;

     if (hash->ctx == NULL) {
         hash->ctx = EVP_MD_CTX_new();
         if (hash->ctx == NULL) {
             EVP_MD_free(md);
             return 0;
         }
     }

     EVP_MD_free(hash->md);
     hash->md = md;

     /* These are taken from SP 800-90 10.1 Table 2 */
     hash->blocklen = EVP_MD_size(md);
     /* See SP800-57 Part1 Rev4 5.6.1 Table 3 */
     drbg->strength = 64 * (hash->blocklen >> 3);
     if (drbg->strength > 256)
         drbg->strength = 256;
     if (hash->blocklen > MAX_BLOCKLEN_USING_SMALL_SEEDLEN)
         drbg->seedlen = HASH_PRNG_MAX_SEEDLEN;
     else
         drbg->seedlen = HASH_PRNG_SMALL_SEEDLEN;

     drbg->min_entropylen = drbg->strength / 8;
     drbg->max_entropylen = DRBG_MAX_LENGTH;

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

     drbg->max_perslen = DRBG_MAX_LENGTH;
     drbg->max_adinlen = DRBG_MAX_LENGTH;

     /* Maximum number of bits per request = 2^19  = 2^16 bytes */
     drbg->max_request = 1 << 16;

     return 1;
 }
	/*
	* Copyright 2011-2018 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/crypto.h>
	#include <openssl/err.h>
	#include <openssl/rand.h>
	#include "internal/thread_once.h"
	#include "prov/providercommon.h"
	#include "rand_local.h"

	/* 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)


	/*
	* 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(RAND_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)
	{
	RAND_DRBG_HASH *hash = &drbg->data.hash;
	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, hash->md, 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(RAND_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(RAND_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(RAND_DRBG *drbg, unsigned char inbyte,
	const unsigned char *adin, size_t adinlen)
	{
	RAND_DRBG_HASH *hash = &drbg->data.hash;
	EVP_MD_CTX *ctx = hash->ctx;

	return EVP_DigestInit_ex(ctx, hash->md, 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(RAND_DRBG drbg, unsigned char out, size_t outlen)
	{
	RAND_DRBG_HASH *hash = &drbg->data.hash;
	unsigned char one = 1;

	if (outlen == 0)
	return 1;
	memcpy(hash->vtmp, hash->V, drbg->seedlen);
	for(;;) {
	if (!EVP_DigestInit_ex(hash->ctx, hash->md, 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(RAND_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)
	{
	RAND_DRBG_HASH *hash = &drbg->data.hash;

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

	/*
	* 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(RAND_DRBG *drbg,
	const unsigned char *ent, size_t ent_len,
	const unsigned char *adin, size_t adin_len)
	{
	RAND_DRBG_HASH *hash = &drbg->data.hash;

	/* (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);
	}

	/*
	* 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(RAND_DRBG *drbg,
	unsigned char *out, size_t outlen,
	const unsigned char *adin, size_t adin_len)
	{
	RAND_DRBG_HASH *hash = &drbg->data.hash;
	unsigned char counter[4];
	int reseed_counter = drbg->reseed_gen_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 (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_uninstantiate(RAND_DRBG *drbg)
	{
	EVP_MD_free(drbg->data.hash.md);
	EVP_MD_CTX_free(drbg->data.hash.ctx);
	OPENSSL_cleanse(&drbg->data.hash, sizeof(drbg->data.hash));
	return 1;
	}

	static RAND_DRBG_METHOD drbg_hash_meth = {
	drbg_hash_instantiate,
	drbg_hash_reseed,
	drbg_hash_generate,
	drbg_hash_uninstantiate
	};

	int drbg_hash_init(RAND_DRBG *drbg)
	{
	EVP_MD *md;
	RAND_DRBG_HASH *hash = &drbg->data.hash;

	/*
	* Confirm digest is allowed. We allow all digests that are not XOF
	* (such as SHAKE). In FIPS mode, the fetch will fail for non-approved
	* digests.
	*/
	md = EVP_MD_fetch(drbg->libctx, ossl_prov_util_nid_to_name(drbg->type), "");
	if (md == NULL)
	return 0;

	if ((EVP_MD_flags(md) & EVP_MD_FLAG_XOF) != 0)
	return 0;

	drbg->meth = &drbg_hash_meth;

	if (hash->ctx == NULL) {
	hash->ctx = EVP_MD_CTX_new();
	if (hash->ctx == NULL) {
	EVP_MD_free(md);
	return 0;
	}
	}

	EVP_MD_free(hash->md);
	hash->md = md;

	/* These are taken from SP 800-90 10.1 Table 2 */
	hash->blocklen = EVP_MD_size(md);
	/* See SP800-57 Part1 Rev4 5.6.1 Table 3 */
	drbg->strength = 64 * (hash->blocklen >> 3);
	if (drbg->strength > 256)
	drbg->strength = 256;
	if (hash->blocklen > MAX_BLOCKLEN_USING_SMALL_SEEDLEN)
	drbg->seedlen = HASH_PRNG_MAX_SEEDLEN;
	else
	drbg->seedlen = HASH_PRNG_SMALL_SEEDLEN;

	drbg->min_entropylen = drbg->strength / 8;
	drbg->max_entropylen = DRBG_MAX_LENGTH;

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

	drbg->max_perslen = DRBG_MAX_LENGTH;
	drbg->max_adinlen = DRBG_MAX_LENGTH;

	/* Maximum number of bits per request = 2^19 = 2^16 bytes */
	drbg->max_request = 1 << 16;

	return 1;
	}