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openssl/crypto/rand/drbg_ctr.c
Kurt Roeckx dbdcc04f27 DRBG: Use the EVP layer to do AES encryption 
Reviewed-by: Rich Salz <rsalz@openssl.org>
GH: #5580
2018-03-21 21:32:47 +01:00

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/*
* Copyright 2011-2018 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 "internal/thread_once.h"
#include "internal/thread_once.h"
#include "rand_lcl.h"
/*
* Implementation of NIST SP 800-90A CTR DRBG.
*/
static void inc_128(RAND_DRBG_CTR *ctr)
{
int i;
unsigned char c;
unsigned char *p = &ctr->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(RAND_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(RAND_DRBG_CTR *ctr, unsigned char *out,
const unsigned char *in)
{
int i, outlen = AES_BLOCK_SIZE;
for (i = 0; i < 16; i++)
out[i] ^= in[i];
if (!EVP_CipherUpdate(ctr->ctx_df, out, &outlen, out, AES_BLOCK_SIZE)
|| outlen != AES_BLOCK_SIZE)
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(RAND_DRBG_CTR *ctr, const unsigned char *in)
{
if (!ctr_BCC_block(ctr, ctr->KX, in)
|| !ctr_BCC_block(ctr, ctr->KX + 16, in))
return 0;
if (ctr->keylen != 16 && !ctr_BCC_block(ctr, ctr->KX + 32, in))
return 0;
return 1;
}
/*
* 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(RAND_DRBG_CTR *ctr)
{
memset(ctr->KX, 0, 48);
memset(ctr->bltmp, 0, 16);
if (!ctr_BCC_block(ctr, ctr->KX, ctr->bltmp))
return 0;
ctr->bltmp[3] = 1;
if (!ctr_BCC_block(ctr, ctr->KX + 16, ctr->bltmp))
return 0;
if (ctr->keylen != 16) {
ctr->bltmp[3] = 2;
if (!ctr_BCC_block(ctr, ctr->KX + 32, ctr->bltmp))
return 0;
}
return 1;
}
/*
* Process several blocks into BCC algorithm, some possibly partial
*/
__owur static int ctr_BCC_update(RAND_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(RAND_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(RAND_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, ctr->cipher, NULL, ctr->KX, NULL, 1))
return 0;
/* X follows key K */
if (!EVP_CipherUpdate(ctr->ctx, ctr->KX, &outlen, ctr->KX + ctr->keylen,
AES_BLOCK_SIZE)
|| outlen != AES_BLOCK_SIZE)
return 0;
if (!EVP_CipherUpdate(ctr->ctx, ctr->KX + 16, &outlen, ctr->KX,
AES_BLOCK_SIZE)
|| outlen != AES_BLOCK_SIZE)
return 0;
if (ctr->keylen != 16)
if (!EVP_CipherUpdate(ctr->ctx, 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(RAND_DRBG *drbg,
const unsigned char *in1, size_t in1len,
const unsigned char *in2, size_t in2len,
const unsigned char *nonce, size_t noncelen)
{
RAND_DRBG_CTR *ctr = &drbg->data.ctr;
int outlen = AES_BLOCK_SIZE;
/* correct key is already set up. */
inc_128(ctr);
if (!EVP_CipherUpdate(ctr->ctx, ctr->K, &outlen, ctr->V, AES_BLOCK_SIZE)
|| outlen != AES_BLOCK_SIZE)
return 0;
/* If keylen longer than 128 bits need extra encrypt */
if (ctr->keylen != 16) {
inc_128(ctr);
if (!EVP_CipherUpdate(ctr->ctx, ctr->K+16, &outlen, ctr->V,
AES_BLOCK_SIZE)
|| outlen != AES_BLOCK_SIZE)
return 0;
}
inc_128(ctr);
if (!EVP_CipherUpdate(ctr->ctx, ctr->V, &outlen, ctr->V, AES_BLOCK_SIZE)
|| outlen != AES_BLOCK_SIZE)
return 0;
/* If 192 bit key part of V is on end of K */
if (ctr->keylen == 24) {
memcpy(ctr->V + 8, ctr->V, 8);
memcpy(ctr->V, ctr->K + 24, 8);
}
if ((drbg->flags & RAND_DRBG_FLAG_CTR_NO_DF) == 0) {
/* 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, ctr->cipher, NULL, ctr->K, NULL, 1))
return 0;
return 1;
}
__owur static int drbg_ctr_instantiate(RAND_DRBG *drbg,
const unsigned char *entropy, size_t entropylen,
const unsigned char *nonce, size_t noncelen,
const unsigned char *pers, size_t perslen)
{
RAND_DRBG_CTR *ctr = &drbg->data.ctr;
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, ctr->cipher, NULL, ctr->K, NULL, 1))
return 0;
if (!ctr_update(drbg, entropy, entropylen, pers, perslen, nonce, noncelen))
return 0;
return 1;
}
__owur static int drbg_ctr_reseed(RAND_DRBG *drbg,
const unsigned char *entropy, size_t entropylen,
const unsigned char *adin, size_t adinlen)
{
if (entropy == NULL)
return 0;
if (!ctr_update(drbg, entropy, entropylen, adin, adinlen, NULL, 0))
return 0;
return 1;
}
__owur static int drbg_ctr_generate(RAND_DRBG *drbg,
unsigned char *out, size_t outlen,
const unsigned char *adin, size_t adinlen)
{
RAND_DRBG_CTR *ctr = &drbg->data.ctr;
if (adin != NULL && adinlen != 0) {
if (!ctr_update(drbg, adin, adinlen, NULL, 0, NULL, 0))
return 0;
/* This means we reuse derived value */
if ((drbg->flags & RAND_DRBG_FLAG_CTR_NO_DF) == 0) {
adin = NULL;
adinlen = 1;
}
} else {
adinlen = 0;
}
for ( ; ; ) {
int outl = AES_BLOCK_SIZE;
inc_128(ctr);
if (outlen < 16) {
/* Use K as temp space as it will be updated */
if (!EVP_CipherUpdate(ctr->ctx, ctr->K, &outl, ctr->V,
AES_BLOCK_SIZE)
|| outl != AES_BLOCK_SIZE)
return 0;
memcpy(out, ctr->K, outlen);
break;
}
if (!EVP_CipherUpdate(ctr->ctx, out, &outl, ctr->V, AES_BLOCK_SIZE)
|| outl != AES_BLOCK_SIZE)
return 0;
out += 16;
outlen -= 16;
if (outlen == 0)
break;
}
if (!ctr_update(drbg, adin, adinlen, NULL, 0, NULL, 0))
return 0;
return 1;
}
static int drbg_ctr_uninstantiate(RAND_DRBG *drbg)
{
EVP_CIPHER_CTX_free(drbg->data.ctr.ctx);
EVP_CIPHER_CTX_free(drbg->data.ctr.ctx_df);
OPENSSL_cleanse(&drbg->data.ctr, sizeof(drbg->data.ctr));
return 1;
}
static RAND_DRBG_METHOD drbg_ctr_meth = {
drbg_ctr_instantiate,
drbg_ctr_reseed,
drbg_ctr_generate,
drbg_ctr_uninstantiate
};
int drbg_ctr_init(RAND_DRBG *drbg)
{
RAND_DRBG_CTR *ctr = &drbg->data.ctr;
size_t keylen;
switch (drbg->type) {
default:
/* This can't happen, but silence the compiler warning. */
return 0;
case NID_aes_128_ctr:
keylen = 16;
ctr->cipher = EVP_aes_128_ecb();
break;
case NID_aes_192_ctr:
keylen = 24;
ctr->cipher = EVP_aes_192_ecb();
break;
case NID_aes_256_ctr:
keylen = 32;
ctr->cipher = EVP_aes_256_ecb();
break;
}
drbg->meth = &drbg_ctr_meth;
ctr->keylen = keylen;
if (ctr->ctx == NULL)
ctr->ctx = EVP_CIPHER_CTX_new();
if (ctr->ctx == NULL)
return 0;
drbg->strength = keylen * 8;
drbg->seedlen = keylen + 16;
if ((drbg->flags & RAND_DRBG_FLAG_CTR_NO_DF) == 0) {
/* 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)
return 0;
/* Set key schedule for df_key */
if (!EVP_CipherInit_ex(ctr->ctx_df, ctr->cipher, NULL, df_key, NULL, 1))
return 0;
drbg->min_entropylen = ctr->keylen;
drbg->max_entropylen = DRBG_MINMAX_FACTOR * drbg->min_entropylen;
drbg->min_noncelen = drbg->min_entropylen / 2;
drbg->max_noncelen = DRBG_MINMAX_FACTOR * drbg->min_noncelen;
drbg->max_perslen = DRBG_MAX_LENGTH;
drbg->max_adinlen = DRBG_MAX_LENGTH;
} else {
drbg->min_entropylen = drbg->seedlen;
drbg->max_entropylen = drbg->seedlen;
/* Nonce not used */
drbg->min_noncelen = 0;
drbg->max_noncelen = 0;
drbg->max_perslen = drbg->seedlen;
drbg->max_adinlen = drbg->seedlen;
}
drbg->max_request = 1 << 16;
return 1;
}
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