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openssl/crypto/rand/drbg_rand.c

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/*
* 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;
}
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