8164d91d18
The NIST standard presents two alternative ways for seeding the CTR DRBG, depending on whether a derivation function is used or not. In Section 10.2.1 of NIST SP800-90Ar1 the following is assessed: The use of the derivation function is optional if either an approved RBG or an entropy source provides full entropy output when entropy input is requested by the DRBG mechanism. Otherwise, the derivation function shall be used. Since the OpenSSL DRBG supports being reseeded from low entropy random sources (using RAND_POOL), the use of a derivation function is mandatory. For that reason we change the default and replace the opt-in flag RAND_DRBG_FLAG_CTR_USE_DF with an opt-out flag RAND_DRBG_FLAG_CTR_NO_DF. This change simplifies the RAND_DRBG_new() calls. Reviewed-by: Rich Salz <rsalz@openssl.org> (Merged from https://github.com/openssl/openssl/pull/5294)
371 lines
10 KiB
C
371 lines
10 KiB
C
/*
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* Copyright 2011-2018 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the OpenSSL license (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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#include <stdlib.h>
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#include <string.h>
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#include <openssl/crypto.h>
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#include <openssl/err.h>
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#include <openssl/rand.h>
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#include "rand_lcl.h"
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#include "internal/thread_once.h"
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/*
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* Implementation of NIST SP 800-90A CTR DRBG.
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*/
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static void inc_128(RAND_DRBG_CTR *ctr)
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{
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int i;
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unsigned char c;
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unsigned char *p = &ctr->V[15];
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for (i = 0; i < 16; i++, p--) {
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c = *p;
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c++;
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*p = c;
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if (c != 0) {
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/* If we didn't wrap around, we're done. */
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break;
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}
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}
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}
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static void ctr_XOR(RAND_DRBG_CTR *ctr, const unsigned char *in, size_t inlen)
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{
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size_t i, n;
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if (in == NULL || inlen == 0)
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return;
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/*
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* Any zero padding will have no effect on the result as we
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* are XORing. So just process however much input we have.
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*/
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n = inlen < ctr->keylen ? inlen : ctr->keylen;
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for (i = 0; i < n; i++)
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ctr->K[i] ^= in[i];
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if (inlen <= ctr->keylen)
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return;
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n = inlen - ctr->keylen;
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if (n > 16) {
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/* Should never happen */
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n = 16;
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}
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for (i = 0; i < n; i++)
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ctr->V[i] ^= in[i + ctr->keylen];
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}
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/*
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* Process a complete block using BCC algorithm of SP 800-90A 10.3.3
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*/
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static void ctr_BCC_block(RAND_DRBG_CTR *ctr, unsigned char *out,
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const unsigned char *in)
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{
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int i;
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for (i = 0; i < 16; i++)
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out[i] ^= in[i];
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AES_encrypt(out, out, &ctr->df_ks);
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}
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/*
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* Handle several BCC operations for as much data as we need for K and X
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*/
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static void ctr_BCC_blocks(RAND_DRBG_CTR *ctr, const unsigned char *in)
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{
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ctr_BCC_block(ctr, ctr->KX, in);
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ctr_BCC_block(ctr, ctr->KX + 16, in);
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if (ctr->keylen != 16)
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ctr_BCC_block(ctr, ctr->KX + 32, in);
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}
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/*
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* Initialise BCC blocks: these have the value 0,1,2 in leftmost positions:
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* see 10.3.1 stage 7.
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*/
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static void ctr_BCC_init(RAND_DRBG_CTR *ctr)
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{
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memset(ctr->KX, 0, 48);
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memset(ctr->bltmp, 0, 16);
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ctr_BCC_block(ctr, ctr->KX, ctr->bltmp);
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ctr->bltmp[3] = 1;
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ctr_BCC_block(ctr, ctr->KX + 16, ctr->bltmp);
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if (ctr->keylen != 16) {
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ctr->bltmp[3] = 2;
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ctr_BCC_block(ctr, ctr->KX + 32, ctr->bltmp);
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}
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}
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/*
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* Process several blocks into BCC algorithm, some possibly partial
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*/
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static void ctr_BCC_update(RAND_DRBG_CTR *ctr,
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const unsigned char *in, size_t inlen)
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{
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if (in == NULL || inlen == 0)
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return;
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/* If we have partial block handle it first */
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if (ctr->bltmp_pos) {
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size_t left = 16 - ctr->bltmp_pos;
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/* If we now have a complete block process it */
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if (inlen >= left) {
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memcpy(ctr->bltmp + ctr->bltmp_pos, in, left);
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ctr_BCC_blocks(ctr, ctr->bltmp);
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ctr->bltmp_pos = 0;
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inlen -= left;
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in += left;
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}
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}
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/* Process zero or more complete blocks */
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for (; inlen >= 16; in += 16, inlen -= 16) {
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ctr_BCC_blocks(ctr, in);
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}
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/* Copy any remaining partial block to the temporary buffer */
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if (inlen > 0) {
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memcpy(ctr->bltmp + ctr->bltmp_pos, in, inlen);
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ctr->bltmp_pos += inlen;
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}
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}
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static void ctr_BCC_final(RAND_DRBG_CTR *ctr)
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{
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if (ctr->bltmp_pos) {
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memset(ctr->bltmp + ctr->bltmp_pos, 0, 16 - ctr->bltmp_pos);
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ctr_BCC_blocks(ctr, ctr->bltmp);
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}
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}
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static void ctr_df(RAND_DRBG_CTR *ctr,
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const unsigned char *in1, size_t in1len,
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const unsigned char *in2, size_t in2len,
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const unsigned char *in3, size_t in3len)
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{
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static unsigned char c80 = 0x80;
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size_t inlen;
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unsigned char *p = ctr->bltmp;
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ctr_BCC_init(ctr);
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if (in1 == NULL)
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in1len = 0;
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if (in2 == NULL)
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in2len = 0;
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if (in3 == NULL)
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in3len = 0;
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inlen = in1len + in2len + in3len;
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/* Initialise L||N in temporary block */
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*p++ = (inlen >> 24) & 0xff;
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*p++ = (inlen >> 16) & 0xff;
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*p++ = (inlen >> 8) & 0xff;
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*p++ = inlen & 0xff;
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/* NB keylen is at most 32 bytes */
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*p++ = 0;
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*p++ = 0;
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*p++ = 0;
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*p = (unsigned char)((ctr->keylen + 16) & 0xff);
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ctr->bltmp_pos = 8;
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ctr_BCC_update(ctr, in1, in1len);
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ctr_BCC_update(ctr, in2, in2len);
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ctr_BCC_update(ctr, in3, in3len);
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ctr_BCC_update(ctr, &c80, 1);
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ctr_BCC_final(ctr);
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/* Set up key K */
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AES_set_encrypt_key(ctr->KX, ctr->keylen * 8, &ctr->df_kxks);
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/* X follows key K */
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AES_encrypt(ctr->KX + ctr->keylen, ctr->KX, &ctr->df_kxks);
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AES_encrypt(ctr->KX, ctr->KX + 16, &ctr->df_kxks);
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if (ctr->keylen != 16)
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AES_encrypt(ctr->KX + 16, ctr->KX + 32, &ctr->df_kxks);
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}
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/*
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* NB the no-df Update in SP800-90A specifies a constant input length
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* of seedlen, however other uses of this algorithm pad the input with
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* zeroes if necessary and have up to two parameters XORed together,
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* so we handle both cases in this function instead.
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*/
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static void ctr_update(RAND_DRBG *drbg,
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const unsigned char *in1, size_t in1len,
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const unsigned char *in2, size_t in2len,
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const unsigned char *nonce, size_t noncelen)
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{
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RAND_DRBG_CTR *ctr = &drbg->data.ctr;
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/* ks is already setup for correct key */
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inc_128(ctr);
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AES_encrypt(ctr->V, ctr->K, &ctr->ks);
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/* If keylen longer than 128 bits need extra encrypt */
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if (ctr->keylen != 16) {
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inc_128(ctr);
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AES_encrypt(ctr->V, ctr->K + 16, &ctr->ks);
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}
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inc_128(ctr);
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AES_encrypt(ctr->V, ctr->V, &ctr->ks);
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/* If 192 bit key part of V is on end of K */
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if (ctr->keylen == 24) {
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memcpy(ctr->V + 8, ctr->V, 8);
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memcpy(ctr->V, ctr->K + 24, 8);
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}
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if ((drbg->flags & RAND_DRBG_FLAG_CTR_NO_DF) == 0) {
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/* If no input reuse existing derived value */
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if (in1 != NULL || nonce != NULL || in2 != NULL)
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ctr_df(ctr, in1, in1len, nonce, noncelen, in2, in2len);
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/* If this a reuse input in1len != 0 */
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if (in1len)
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ctr_XOR(ctr, ctr->KX, drbg->seedlen);
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} else {
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ctr_XOR(ctr, in1, in1len);
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ctr_XOR(ctr, in2, in2len);
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}
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AES_set_encrypt_key(ctr->K, drbg->strength, &ctr->ks);
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}
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static int drbg_ctr_instantiate(RAND_DRBG *drbg,
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const unsigned char *entropy, size_t entropylen,
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const unsigned char *nonce, size_t noncelen,
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const unsigned char *pers, size_t perslen)
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{
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RAND_DRBG_CTR *ctr = &drbg->data.ctr;
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if (entropy == NULL)
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return 0;
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memset(ctr->K, 0, sizeof(ctr->K));
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memset(ctr->V, 0, sizeof(ctr->V));
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AES_set_encrypt_key(ctr->K, drbg->strength, &ctr->ks);
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ctr_update(drbg, entropy, entropylen, pers, perslen, nonce, noncelen);
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return 1;
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}
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static int drbg_ctr_reseed(RAND_DRBG *drbg,
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const unsigned char *entropy, size_t entropylen,
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const unsigned char *adin, size_t adinlen)
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{
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if (entropy == NULL)
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return 0;
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ctr_update(drbg, entropy, entropylen, adin, adinlen, NULL, 0);
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return 1;
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}
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static int drbg_ctr_generate(RAND_DRBG *drbg,
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unsigned char *out, size_t outlen,
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const unsigned char *adin, size_t adinlen)
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{
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RAND_DRBG_CTR *ctr = &drbg->data.ctr;
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if (adin != NULL && adinlen != 0) {
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ctr_update(drbg, adin, adinlen, NULL, 0, NULL, 0);
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/* This means we reuse derived value */
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if ((drbg->flags & RAND_DRBG_FLAG_CTR_NO_DF) == 0) {
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adin = NULL;
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adinlen = 1;
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}
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} else {
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adinlen = 0;
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}
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for ( ; ; ) {
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inc_128(ctr);
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if (outlen < 16) {
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/* Use K as temp space as it will be updated */
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AES_encrypt(ctr->V, ctr->K, &ctr->ks);
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memcpy(out, ctr->K, outlen);
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break;
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}
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AES_encrypt(ctr->V, out, &ctr->ks);
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out += 16;
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outlen -= 16;
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if (outlen == 0)
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break;
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}
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ctr_update(drbg, adin, adinlen, NULL, 0, NULL, 0);
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return 1;
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}
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static int drbg_ctr_uninstantiate(RAND_DRBG *drbg)
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{
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OPENSSL_cleanse(&drbg->data.ctr, sizeof(drbg->data.ctr));
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return 1;
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}
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static RAND_DRBG_METHOD drbg_ctr_meth = {
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drbg_ctr_instantiate,
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drbg_ctr_reseed,
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drbg_ctr_generate,
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drbg_ctr_uninstantiate
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};
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int drbg_ctr_init(RAND_DRBG *drbg)
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{
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RAND_DRBG_CTR *ctr = &drbg->data.ctr;
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size_t keylen;
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switch (drbg->nid) {
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default:
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/* This can't happen, but silence the compiler warning. */
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return 0;
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case NID_aes_128_ctr:
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keylen = 16;
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break;
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case NID_aes_192_ctr:
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keylen = 24;
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break;
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case NID_aes_256_ctr:
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keylen = 32;
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break;
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}
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drbg->meth = &drbg_ctr_meth;
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ctr->keylen = keylen;
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drbg->strength = keylen * 8;
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drbg->seedlen = keylen + 16;
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if ((drbg->flags & RAND_DRBG_FLAG_CTR_NO_DF) == 0) {
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/* df initialisation */
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static unsigned char df_key[32] = {
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0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,
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0x08,0x09,0x0a,0x0b,0x0c,0x0d,0x0e,0x0f,
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0x10,0x11,0x12,0x13,0x14,0x15,0x16,0x17,
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0x18,0x19,0x1a,0x1b,0x1c,0x1d,0x1e,0x1f
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};
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/* Set key schedule for df_key */
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AES_set_encrypt_key(df_key, drbg->strength, &ctr->df_ks);
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drbg->min_entropylen = ctr->keylen;
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drbg->max_entropylen = DRBG_MINMAX_FACTOR * drbg->min_entropylen;
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drbg->min_noncelen = drbg->min_entropylen / 2;
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drbg->max_noncelen = DRBG_MINMAX_FACTOR * drbg->min_noncelen;
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drbg->max_perslen = DRBG_MAX_LENGTH;
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drbg->max_adinlen = DRBG_MAX_LENGTH;
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} else {
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drbg->min_entropylen = drbg->seedlen;
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drbg->max_entropylen = drbg->seedlen;
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/* Nonce not used */
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drbg->min_noncelen = 0;
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drbg->max_noncelen = 0;
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drbg->max_perslen = drbg->seedlen;
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drbg->max_adinlen = drbg->seedlen;
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}
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drbg->max_request = 1 << 16;
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drbg->reseed_interval = MAX_RESEED_INTERVAL;
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return 1;
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}
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