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openssl/crypto/rand/drbg_ctr.c

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/*
* Copyright 2011-2020 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 "modes_local.h"
#include "internal/thread_once.h"
#include "rand_local.h"
/*
* Implementation of NIST SP 800-90A CTR DRBG.
*/
static void inc_128(RAND_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(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 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(RAND_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(RAND_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(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_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(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;
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 ((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_ecb, NULL, NULL, ctr->K, NULL, -1)
|| !EVP_CipherInit_ex(ctr->ctx_ctr, NULL, 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_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;
}
__owur static int drbg_ctr_reseed(RAND_DRBG *drbg,
const unsigned char *entropy, size_t entropylen,
const unsigned char *adin, size_t adinlen)
{
RAND_DRBG_CTR *ctr = &drbg->data.ctr;
if (entropy == NULL)
return 0;
inc_128(ctr);
if (!ctr_update(drbg, entropy, entropylen, adin, adinlen, NULL, 0))
return 0;
return 1;
}
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);
}
__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;
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 ((drbg->flags & RAND_DRBG_FLAG_CTR_NO_DF) == 0) {
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_uninstantiate(RAND_DRBG *drbg)
{
EVP_CIPHER_CTX_free(drbg->data.ctr.ctx_ecb);
EVP_CIPHER_CTX_free(drbg->data.ctr.ctx_ctr);
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_ecb = EVP_aes_128_ecb();
ctr->cipher_ctr = EVP_aes_128_ctr();
break;
case NID_aes_192_ctr:
keylen = 24;
ctr->cipher_ecb = EVP_aes_192_ecb();
ctr->cipher_ctr = EVP_aes_192_ctr();
break;
case NID_aes_256_ctr:
keylen = 32;
ctr->cipher_ecb = EVP_aes_256_ecb();
ctr->cipher_ctr = EVP_aes_256_ctr();
break;
}
drbg->meth = &drbg_ctr_meth;
ctr->keylen = keylen;
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
|| !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))
return 0;
drbg->meth = &drbg_ctr_meth;
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_ecb, NULL, df_key, NULL, 1))
return 0;
drbg->min_entropylen = ctr->keylen;
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;
} 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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