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

 /*
  * Copyright 2011-2017 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (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 "rand_lcl.h"
 #include "internal/thread_once.h"

 /*
  * Mapping of NIST SP 800-90A DRBG to OpenSSL RAND_METHOD.
  */


 /*
  * The default global DRBG and its auto-init/auto-cleanup.
  */
 static DRBG_CTX ossl_drbg;

 static CRYPTO_ONCE ossl_drbg_init = CRYPTO_ONCE_STATIC_INIT;

 DEFINE_RUN_ONCE_STATIC(do_ossl_drbg_init)
 {
     int st = 1;

     ossl_drbg.lock = CRYPTO_THREAD_lock_new();
     st &= ossl_drbg.lock != NULL;
     st &= RAND_DRBG_set(&ossl_drbg, NID_aes_128_ctr, 0) == 1;
     return st;
 }

 void rand_drbg_cleanup(void)
 {
     CRYPTO_THREAD_lock_free(ossl_drbg.lock);
 }

 static void inc_128(DRBG_CTR_CTX *cctx)
 {
     int i;
     unsigned char c;
     unsigned char *p = &cctx->V[15];

     for (i = 0; i < 16; i++, p--) {
         c = *p;
         c++;
         *p = c;
         if (c != 0) {
             /* If we didn't wrap around, we're done. */
             break;
         }
     }
 }

 static void ctr_XOR(DRBG_CTR_CTX *cctx, 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 < cctx->keylen ? inlen : cctx->keylen;
     for (i = 0; i < n; i++)
         cctx->K[i] ^= in[i];
     if (inlen <= cctx->keylen)
         return;

     n = inlen - cctx->keylen;
     if (n > 16) {
         /* Should never happen */
         n = 16;
     }
     for (i = 0; i < n; i++)
         cctx->V[i] ^= in[i + cctx->keylen];
 }

 /*
  * Process a complete block using BCC algorithm of SP 800-90A 10.3.3
  */
 static void ctr_BCC_block(DRBG_CTR_CTX *cctx, unsigned char *out,
                           const unsigned char *in)
 {
     int i;

     for (i = 0; i < 16; i++)
         out[i] ^= in[i];
     AES_encrypt(out, out, &cctx->df_ks);
 }


 /*
  * Handle several BCC operations for as much data as we need for K and X
  */
 static void ctr_BCC_blocks(DRBG_CTR_CTX *cctx, const unsigned char *in)
 {
     ctr_BCC_block(cctx, cctx->KX, in);
     ctr_BCC_block(cctx, cctx->KX + 16, in);
     if (cctx->keylen != 16)
         ctr_BCC_block(cctx, cctx->KX + 32, in);
 }

 /*
  * Initialise BCC blocks: these have the value 0,1,2 in leftmost positions:
  * see 10.3.1 stage 7.
  */
 static void ctr_BCC_init(DRBG_CTR_CTX *cctx)
 {
     memset(cctx->KX, 0, 48);
     memset(cctx->bltmp, 0, 16);
     ctr_BCC_block(cctx, cctx->KX, cctx->bltmp);
     cctx->bltmp[3] = 1;
     ctr_BCC_block(cctx, cctx->KX + 16, cctx->bltmp);
     if (cctx->keylen != 16) {
         cctx->bltmp[3] = 2;
         ctr_BCC_block(cctx, cctx->KX + 32, cctx->bltmp);
     }
 }

 /*
  * Process several blocks into BCC algorithm, some possibly partial
  */
 static void ctr_BCC_update(DRBG_CTR_CTX *cctx,
                            const unsigned char *in, size_t inlen)
 {
     if (in == NULL || inlen == 0)
         return;

     /* If we have partial block handle it first */
     if (cctx->bltmp_pos) {
         size_t left = 16 - cctx->bltmp_pos;

         /* If we now have a complete block process it */
         if (inlen >= left) {
             memcpy(cctx->bltmp + cctx->bltmp_pos, in, left);
             ctr_BCC_blocks(cctx, cctx->bltmp);
             cctx->bltmp_pos = 0;
             inlen -= left;
             in += left;
         }
     }

     /* Process zero or more complete blocks */
     for (; inlen >= 16; in += 16, inlen -= 16) {
         ctr_BCC_blocks(cctx, in);
     }

     /* Copy any remaining partial block to the temporary buffer */
     if (inlen > 0) {
         memcpy(cctx->bltmp + cctx->bltmp_pos, in, inlen);
         cctx->bltmp_pos += inlen;
     }
 }

 static void ctr_BCC_final(DRBG_CTR_CTX *cctx)
 {
     if (cctx->bltmp_pos) {
         memset(cctx->bltmp + cctx->bltmp_pos, 0, 16 - cctx->bltmp_pos);
         ctr_BCC_blocks(cctx, cctx->bltmp);
     }
 }

 static void ctr_df(DRBG_CTR_CTX *cctx,
                    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 = cctx->bltmp;

     ctr_BCC_init(cctx);
     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)((cctx->keylen + 16) & 0xff);
     cctx->bltmp_pos = 8;
     ctr_BCC_update(cctx, in1, in1len);
     ctr_BCC_update(cctx, in2, in2len);
     ctr_BCC_update(cctx, in3, in3len);
     ctr_BCC_update(cctx, &c80, 1);
     ctr_BCC_final(cctx);
     /* Set up key K */
     AES_set_encrypt_key(cctx->KX, cctx->keylen * 8, &cctx->df_kxks);
     /* X follows key K */
     AES_encrypt(cctx->KX + cctx->keylen, cctx->KX, &cctx->df_kxks);
     AES_encrypt(cctx->KX, cctx->KX + 16, &cctx->df_kxks);
     if (cctx->keylen != 16)
         AES_encrypt(cctx->KX + 16, cctx->KX + 32, &cctx->df_kxks);
 }

 /*
  * 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,
  * handle both cases in this function instead.
  */
 static void ctr_update(DRBG_CTX *dctx,
                        const unsigned char *in1, size_t in1len,
                        const unsigned char *in2, size_t in2len,
                        const unsigned char *nonce, size_t noncelen)
 {
     DRBG_CTR_CTX *cctx = &dctx->ctr;

     /* ks is already setup for correct key */
     inc_128(cctx);
     AES_encrypt(cctx->V, cctx->K, &cctx->ks);

     /* If keylen longer than 128 bits need extra encrypt */
     if (cctx->keylen != 16) {
         inc_128(cctx);
         AES_encrypt(cctx->V, cctx->K + 16, &cctx->ks);
     }
     inc_128(cctx);
     AES_encrypt(cctx->V, cctx->V, &cctx->ks);

     /* If 192 bit key part of V is on end of K */
     if (cctx->keylen == 24) {
         memcpy(cctx->V + 8, cctx->V, 8);
         memcpy(cctx->V, cctx->K + 24, 8);
     }

     if (dctx->flags & RAND_DRBG_FLAG_CTR_USE_DF) {
         /* If no input reuse existing derived value */
         if (in1 != NULL || nonce != NULL || in2 != NULL)
             ctr_df(cctx, in1, in1len, nonce, noncelen, in2, in2len);
         /* If this a reuse input in1len != 0 */
         if (in1len)
             ctr_XOR(cctx, cctx->KX, dctx->seedlen);
     } else {
         ctr_XOR(cctx, in1, in1len);
         ctr_XOR(cctx, in2, in2len);
     }

     AES_set_encrypt_key(cctx->K, dctx->strength, &cctx->ks);
 }

 int ctr_instantiate(DRBG_CTX *dctx,
                     const unsigned char *ent, size_t entlen,
                     const unsigned char *nonce, size_t noncelen,
                     const unsigned char *pers, size_t perslen)
 {
     DRBG_CTR_CTX *cctx = &dctx->ctr;

     memset(cctx->K, 0, sizeof(cctx->K));
     memset(cctx->V, 0, sizeof(cctx->V));
     AES_set_encrypt_key(cctx->K, dctx->strength, &cctx->ks);
     ctr_update(dctx, ent, entlen, pers, perslen, nonce, noncelen);
     return 1;
 }

 int ctr_reseed(DRBG_CTX *dctx,
                const unsigned char *ent, size_t entlen,
                const unsigned char *adin, size_t adinlen)
 {
     ctr_update(dctx, ent, entlen, adin, adinlen, NULL, 0);
     return 1;
 }

 int ctr_generate(DRBG_CTX *dctx,
                  unsigned char *out, size_t outlen,
                  const unsigned char *adin, size_t adinlen)
 {
     DRBG_CTR_CTX *cctx = &dctx->ctr;

     if (adin != NULL && adinlen != 0) {
         ctr_update(dctx, adin, adinlen, NULL, 0, NULL, 0);
         /* This means we reuse derived value */
         if (dctx->flags & RAND_DRBG_FLAG_CTR_USE_DF) {
             adin = NULL;
             adinlen = 1;
         }
     } else {
         adinlen = 0;
     }

     for ( ; ; ) {
         inc_128(cctx);
         if (outlen < 16) {
             /* Use K as temp space as it will be updated */
             AES_encrypt(cctx->V, cctx->K, &cctx->ks);
             memcpy(out, cctx->K, outlen);
             break;
         }
         AES_encrypt(cctx->V, out, &cctx->ks);
         out += 16;
         outlen -= 16;
         if (outlen == 0)
             break;
     }

     ctr_update(dctx, adin, adinlen, NULL, 0, NULL, 0);
     return 1;
 }

 int ctr_uninstantiate(DRBG_CTX *dctx)
 {
     memset(&dctx->ctr, 0, sizeof(dctx->ctr));
     return 1;
 }

 int ctr_init(DRBG_CTX *dctx)
 {
     DRBG_CTR_CTX *cctx = &dctx->ctr;
     size_t keylen;

     switch (dctx->nid) {
     default:
         /* This can't happen, but silence the compiler warning. */
         return -1;
     case NID_aes_128_ctr:
         keylen = 16;
         break;
     case NID_aes_192_ctr:
         keylen = 24;
         break;
     case NID_aes_256_ctr:
         keylen = 32;
         break;
     }

     cctx->keylen = keylen;
     dctx->strength = keylen * 8;
     dctx->blocklength = 16;
     dctx->seedlen = keylen + 16;

     if (dctx->flags & RAND_DRBG_FLAG_CTR_USE_DF) {
         /* df initialisation */
         static 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
         };
         /* Set key schedule for df_key */
         AES_set_encrypt_key(df_key, dctx->strength, &cctx->df_ks);

         dctx->min_entropy = cctx->keylen;
         dctx->max_entropy = DRBG_MAX_LENGTH;
         dctx->min_nonce = dctx->min_entropy / 2;
         dctx->max_nonce = DRBG_MAX_LENGTH;
         dctx->max_pers = DRBG_MAX_LENGTH;
         dctx->max_adin = DRBG_MAX_LENGTH;
     } else {
         dctx->min_entropy = dctx->seedlen;
         dctx->max_entropy = dctx->seedlen;
         /* Nonce not used */
         dctx->min_nonce = 0;
         dctx->max_nonce = 0;
         dctx->max_pers = dctx->seedlen;
         dctx->max_adin = dctx->seedlen;
     }

     dctx->max_request = 1 << 16;
     dctx->reseed_interval = MAX_RESEED;
     return 1;
 }


 /*
  * The following function tie the DRBG code into the RAND_METHOD
  */

 DRBG_CTX *RAND_DRBG_get_default(void)
 {
     if (!RUN_ONCE(&ossl_drbg_init, do_ossl_drbg_init))
         return NULL;
     return &ossl_drbg;
 }

 static int drbg_bytes(unsigned char *out, int count)
 {
     DRBG_CTX *dctx = RAND_DRBG_get_default();
     int ret = 0;

     CRYPTO_THREAD_write_lock(dctx->lock);
     do {
         size_t rcnt;

         if (count > (int)dctx->max_request)
             rcnt = dctx->max_request;
         else
             rcnt = count;
         ret = RAND_DRBG_generate(dctx, out, rcnt, 0, NULL, 0);
         if (!ret)
             goto err;
         out += rcnt;
         count -= rcnt;
     } while (count);
     ret = 1;
 err:
     CRYPTO_THREAD_unlock(dctx->lock);
     return ret;
 }

 static int drbg_status(void)
 {
     DRBG_CTX *dctx = RAND_DRBG_get_default();
     int ret;

     CRYPTO_THREAD_write_lock(dctx->lock);
     ret = dctx->status == DRBG_STATUS_READY ? 1 : 0;
     CRYPTO_THREAD_unlock(dctx->lock);
     return ret;
 }

 static void drbg_cleanup(void)
 {
     DRBG_CTX *dctx = RAND_DRBG_get_default();

     CRYPTO_THREAD_write_lock(dctx->lock);
     RAND_DRBG_uninstantiate(dctx);
     CRYPTO_THREAD_unlock(dctx->lock);
 }

 static const RAND_METHOD rand_drbg_meth =
 {
     NULL,
     drbg_bytes,
     drbg_cleanup,
     NULL,
     drbg_bytes,
     drbg_status
 };

 const RAND_METHOD *RAND_drbg(void)
 {
     return &rand_drbg_meth;
 }
	/*
	* Copyright 2011-2017 The OpenSSL Project Authors. All Rights Reserved.
	*
	* Licensed under the OpenSSL license (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 "rand_lcl.h"
	#include "internal/thread_once.h"

	/*
	* Mapping of NIST SP 800-90A DRBG to OpenSSL RAND_METHOD.
	*/


	/*
	* The default global DRBG and its auto-init/auto-cleanup.
	*/
	static DRBG_CTX ossl_drbg;

	static CRYPTO_ONCE ossl_drbg_init = CRYPTO_ONCE_STATIC_INIT;

	DEFINE_RUN_ONCE_STATIC(do_ossl_drbg_init)
	{
	int st = 1;

	ossl_drbg.lock = CRYPTO_THREAD_lock_new();
	st &= ossl_drbg.lock != NULL;
	st &= RAND_DRBG_set(&ossl_drbg, NID_aes_128_ctr, 0) == 1;
	return st;
	}

	void rand_drbg_cleanup(void)
	{
	CRYPTO_THREAD_lock_free(ossl_drbg.lock);
	}

	static void inc_128(DRBG_CTR_CTX *cctx)
	{
	int i;
	unsigned char c;
	unsigned char *p = &cctx->V[15];

	for (i = 0; i < 16; i++, p--) {
	c = *p;
	c++;
	*p = c;
	if (c != 0) {
	/* If we didn't wrap around, we're done. */
	break;
	}
	}
	}

	static void ctr_XOR(DRBG_CTR_CTX cctx, 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 < cctx->keylen ? inlen : cctx->keylen;
	for (i = 0; i < n; i++)
	cctx->K[i] ^= in[i];
	if (inlen <= cctx->keylen)
	return;

	n = inlen - cctx->keylen;
	if (n > 16) {
	/* Should never happen */
	n = 16;
	}
	for (i = 0; i < n; i++)
	cctx->V[i] ^= in[i + cctx->keylen];
	}

	/*
	* Process a complete block using BCC algorithm of SP 800-90A 10.3.3
	*/
	static void ctr_BCC_block(DRBG_CTR_CTX cctx, unsigned char out,
	const unsigned char *in)
	{
	int i;

	for (i = 0; i < 16; i++)
	out[i] ^= in[i];
	AES_encrypt(out, out, &cctx->df_ks);
	}


	/*
	* Handle several BCC operations for as much data as we need for K and X
	*/
	static void ctr_BCC_blocks(DRBG_CTR_CTX cctx, const unsigned char in)
	{
	ctr_BCC_block(cctx, cctx->KX, in);
	ctr_BCC_block(cctx, cctx->KX + 16, in);
	if (cctx->keylen != 16)
	ctr_BCC_block(cctx, cctx->KX + 32, in);
	}

	/*
	* Initialise BCC blocks: these have the value 0,1,2 in leftmost positions:
	* see 10.3.1 stage 7.
	*/
	static void ctr_BCC_init(DRBG_CTR_CTX *cctx)
	{
	memset(cctx->KX, 0, 48);
	memset(cctx->bltmp, 0, 16);
	ctr_BCC_block(cctx, cctx->KX, cctx->bltmp);
	cctx->bltmp[3] = 1;
	ctr_BCC_block(cctx, cctx->KX + 16, cctx->bltmp);
	if (cctx->keylen != 16) {
	cctx->bltmp[3] = 2;
	ctr_BCC_block(cctx, cctx->KX + 32, cctx->bltmp);
	}
	}

	/*
	* Process several blocks into BCC algorithm, some possibly partial
	*/
	static void ctr_BCC_update(DRBG_CTR_CTX *cctx,
	const unsigned char *in, size_t inlen)
	{
	if (in == NULL \|\| inlen == 0)
	return;

	/* If we have partial block handle it first */
	if (cctx->bltmp_pos) {
	size_t left = 16 - cctx->bltmp_pos;

	/* If we now have a complete block process it */
	if (inlen >= left) {
	memcpy(cctx->bltmp + cctx->bltmp_pos, in, left);
	ctr_BCC_blocks(cctx, cctx->bltmp);
	cctx->bltmp_pos = 0;
	inlen -= left;
	in += left;
	}
	}

	/* Process zero or more complete blocks */
	for (; inlen >= 16; in += 16, inlen -= 16) {
	ctr_BCC_blocks(cctx, in);
	}

	/* Copy any remaining partial block to the temporary buffer */
	if (inlen > 0) {
	memcpy(cctx->bltmp + cctx->bltmp_pos, in, inlen);
	cctx->bltmp_pos += inlen;
	}
	}

	static void ctr_BCC_final(DRBG_CTR_CTX *cctx)
	{
	if (cctx->bltmp_pos) {
	memset(cctx->bltmp + cctx->bltmp_pos, 0, 16 - cctx->bltmp_pos);
	ctr_BCC_blocks(cctx, cctx->bltmp);
	}
	}

	static void ctr_df(DRBG_CTR_CTX *cctx,
	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 = cctx->bltmp;

	ctr_BCC_init(cctx);
	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)((cctx->keylen + 16) & 0xff);
	cctx->bltmp_pos = 8;
	ctr_BCC_update(cctx, in1, in1len);
	ctr_BCC_update(cctx, in2, in2len);
	ctr_BCC_update(cctx, in3, in3len);
	ctr_BCC_update(cctx, &c80, 1);
	ctr_BCC_final(cctx);
	/* Set up key K */
	AES_set_encrypt_key(cctx->KX, cctx->keylen * 8, &cctx->df_kxks);
	/* X follows key K */
	AES_encrypt(cctx->KX + cctx->keylen, cctx->KX, &cctx->df_kxks);
	AES_encrypt(cctx->KX, cctx->KX + 16, &cctx->df_kxks);
	if (cctx->keylen != 16)
	AES_encrypt(cctx->KX + 16, cctx->KX + 32, &cctx->df_kxks);
	}

	/*
	* 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,
	* handle both cases in this function instead.
	*/
	static void ctr_update(DRBG_CTX *dctx,
	const unsigned char *in1, size_t in1len,
	const unsigned char *in2, size_t in2len,
	const unsigned char *nonce, size_t noncelen)
	{
	DRBG_CTR_CTX *cctx = &dctx->ctr;

	/* ks is already setup for correct key */
	inc_128(cctx);
	AES_encrypt(cctx->V, cctx->K, &cctx->ks);

	/* If keylen longer than 128 bits need extra encrypt */
	if (cctx->keylen != 16) {
	inc_128(cctx);
	AES_encrypt(cctx->V, cctx->K + 16, &cctx->ks);
	}
	inc_128(cctx);
	AES_encrypt(cctx->V, cctx->V, &cctx->ks);

	/* If 192 bit key part of V is on end of K */
	if (cctx->keylen == 24) {
	memcpy(cctx->V + 8, cctx->V, 8);
	memcpy(cctx->V, cctx->K + 24, 8);
	}

	if (dctx->flags & RAND_DRBG_FLAG_CTR_USE_DF) {
	/* If no input reuse existing derived value */
	if (in1 != NULL \|\| nonce != NULL \|\| in2 != NULL)
	ctr_df(cctx, in1, in1len, nonce, noncelen, in2, in2len);
	/* If this a reuse input in1len != 0 */
	if (in1len)
	ctr_XOR(cctx, cctx->KX, dctx->seedlen);
	} else {
	ctr_XOR(cctx, in1, in1len);
	ctr_XOR(cctx, in2, in2len);
	}

	AES_set_encrypt_key(cctx->K, dctx->strength, &cctx->ks);
	}

	int ctr_instantiate(DRBG_CTX *dctx,
	const unsigned char *ent, size_t entlen,
	const unsigned char *nonce, size_t noncelen,
	const unsigned char *pers, size_t perslen)
	{
	DRBG_CTR_CTX *cctx = &dctx->ctr;

	memset(cctx->K, 0, sizeof(cctx->K));
	memset(cctx->V, 0, sizeof(cctx->V));
	AES_set_encrypt_key(cctx->K, dctx->strength, &cctx->ks);
	ctr_update(dctx, ent, entlen, pers, perslen, nonce, noncelen);
	return 1;
	}

	int ctr_reseed(DRBG_CTX *dctx,
	const unsigned char *ent, size_t entlen,
	const unsigned char *adin, size_t adinlen)
	{
	ctr_update(dctx, ent, entlen, adin, adinlen, NULL, 0);
	return 1;
	}

	int ctr_generate(DRBG_CTX *dctx,
	unsigned char *out, size_t outlen,
	const unsigned char *adin, size_t adinlen)
	{
	DRBG_CTR_CTX *cctx = &dctx->ctr;

	if (adin != NULL && adinlen != 0) {
	ctr_update(dctx, adin, adinlen, NULL, 0, NULL, 0);
	/* This means we reuse derived value */
	if (dctx->flags & RAND_DRBG_FLAG_CTR_USE_DF) {
	adin = NULL;
	adinlen = 1;
	}
	} else {
	adinlen = 0;
	}

	for ( ; ; ) {
	inc_128(cctx);
	if (outlen < 16) {
	/* Use K as temp space as it will be updated */
	AES_encrypt(cctx->V, cctx->K, &cctx->ks);
	memcpy(out, cctx->K, outlen);
	break;
	}
	AES_encrypt(cctx->V, out, &cctx->ks);
	out += 16;
	outlen -= 16;
	if (outlen == 0)
	break;
	}

	ctr_update(dctx, adin, adinlen, NULL, 0, NULL, 0);
	return 1;
	}

	int ctr_uninstantiate(DRBG_CTX *dctx)
	{
	memset(&dctx->ctr, 0, sizeof(dctx->ctr));
	return 1;
	}

	int ctr_init(DRBG_CTX *dctx)
	{
	DRBG_CTR_CTX *cctx = &dctx->ctr;
	size_t keylen;

	switch (dctx->nid) {
	default:
	/* This can't happen, but silence the compiler warning. */
	return -1;
	case NID_aes_128_ctr:
	keylen = 16;
	break;
	case NID_aes_192_ctr:
	keylen = 24;
	break;
	case NID_aes_256_ctr:
	keylen = 32;
	break;
	}

	cctx->keylen = keylen;
	dctx->strength = keylen * 8;
	dctx->blocklength = 16;
	dctx->seedlen = keylen + 16;

	if (dctx->flags & RAND_DRBG_FLAG_CTR_USE_DF) {
	/* df initialisation */
	static 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
	};
	/* Set key schedule for df_key */
	AES_set_encrypt_key(df_key, dctx->strength, &cctx->df_ks);

	dctx->min_entropy = cctx->keylen;
	dctx->max_entropy = DRBG_MAX_LENGTH;
	dctx->min_nonce = dctx->min_entropy / 2;
	dctx->max_nonce = DRBG_MAX_LENGTH;
	dctx->max_pers = DRBG_MAX_LENGTH;
	dctx->max_adin = DRBG_MAX_LENGTH;
	} else {
	dctx->min_entropy = dctx->seedlen;
	dctx->max_entropy = dctx->seedlen;
	/* Nonce not used */
	dctx->min_nonce = 0;
	dctx->max_nonce = 0;
	dctx->max_pers = dctx->seedlen;
	dctx->max_adin = dctx->seedlen;
	}

	dctx->max_request = 1 << 16;
	dctx->reseed_interval = MAX_RESEED;
	return 1;
	}


	/*
	* The following function tie the DRBG code into the RAND_METHOD
	*/

	DRBG_CTX *RAND_DRBG_get_default(void)
	{
	if (!RUN_ONCE(&ossl_drbg_init, do_ossl_drbg_init))
	return NULL;
	return &ossl_drbg;
	}

	static int drbg_bytes(unsigned char *out, int count)
	{
	DRBG_CTX *dctx = RAND_DRBG_get_default();
	int ret = 0;

	CRYPTO_THREAD_write_lock(dctx->lock);
	do {
	size_t rcnt;

	if (count > (int)dctx->max_request)
	rcnt = dctx->max_request;
	else
	rcnt = count;
	ret = RAND_DRBG_generate(dctx, out, rcnt, 0, NULL, 0);
	if (!ret)
	goto err;
	out += rcnt;
	count -= rcnt;
	} while (count);
	ret = 1;
	err:
	CRYPTO_THREAD_unlock(dctx->lock);
	return ret;
	}

	static int drbg_status(void)
	{
	DRBG_CTX *dctx = RAND_DRBG_get_default();
	int ret;

	CRYPTO_THREAD_write_lock(dctx->lock);
	ret = dctx->status == DRBG_STATUS_READY ? 1 : 0;
	CRYPTO_THREAD_unlock(dctx->lock);
	return ret;
	}

	static void drbg_cleanup(void)
	{
	DRBG_CTX *dctx = RAND_DRBG_get_default();

	CRYPTO_THREAD_write_lock(dctx->lock);
	RAND_DRBG_uninstantiate(dctx);
	CRYPTO_THREAD_unlock(dctx->lock);
	}

	static const RAND_METHOD rand_drbg_meth =
	{
	NULL,
	drbg_bytes,
	drbg_cleanup,
	NULL,
	drbg_bytes,
	drbg_status
	};

	const RAND_METHOD *RAND_drbg(void)
	{
	return &rand_drbg_meth;
	}