openssl/crypto/rand/drbg_hash.c
Richard Levitte 0db63de94c Following the license change, modify the boilerplates in crypto/rand/
[skip ci]

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7811)
2018-12-06 15:14:05 +01:00

348 lines
12 KiB
C

/*
* Copyright 2011-2018 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (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 <assert.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/crypto.h>
#include <openssl/err.h>
#include <openssl/rand.h>
#include "internal/thread_once.h"
#include "rand_lcl.h"
/* 440 bits from SP800-90Ar1 10.1 table 2 */
#define HASH_PRNG_SMALL_SEEDLEN (440/8)
/* Determine what seedlen to use based on the block length */
#define MAX_BLOCKLEN_USING_SMALL_SEEDLEN (256/8)
#define INBYTE_IGNORE ((unsigned char)0xFF)
/*
* SP800-90Ar1 10.3.1 Derivation function using a Hash Function (Hash_df).
* The input string used is composed of:
* inbyte - An optional leading byte (ignore if equal to INBYTE_IGNORE)
* in - input string 1 (A Non NULL value).
* in2 - optional input string (Can be NULL).
* in3 - optional input string (Can be NULL).
* These are concatenated as part of the DigestUpdate process.
*/
static int hash_df(RAND_DRBG *drbg, unsigned char *out,
const unsigned char inbyte,
const unsigned char *in, size_t inlen,
const unsigned char *in2, size_t in2len,
const unsigned char *in3, size_t in3len)
{
RAND_DRBG_HASH *hash = &drbg->data.hash;
EVP_MD_CTX *ctx = hash->ctx;
unsigned char *vtmp = hash->vtmp;
/* tmp = counter || num_bits_returned || [inbyte] */
unsigned char tmp[1 + 4 + 1];
int tmp_sz = 0;
size_t outlen = drbg->seedlen;
size_t num_bits_returned = outlen * 8;
/*
* No need to check outlen size here, as the standard only ever needs
* seedlen bytes which is always less than the maximum permitted.
*/
/* (Step 3) counter = 1 (tmp[0] is the 8 bit counter) */
tmp[tmp_sz++] = 1;
/* tmp[1..4] is the fixed 32 bit no_of_bits_to_return */
tmp[tmp_sz++] = (unsigned char)((num_bits_returned >> 24) & 0xff);
tmp[tmp_sz++] = (unsigned char)((num_bits_returned >> 16) & 0xff);
tmp[tmp_sz++] = (unsigned char)((num_bits_returned >> 8) & 0xff);
tmp[tmp_sz++] = (unsigned char)(num_bits_returned & 0xff);
/* Tack the additional input byte onto the end of tmp if it exists */
if (inbyte != INBYTE_IGNORE)
tmp[tmp_sz++] = inbyte;
/* (Step 4) */
for (;;) {
/*
* (Step 4.1) out = out || Hash(tmp || in || [in2] || [in3])
* (where tmp = counter || num_bits_returned || [inbyte])
*/
if (!(EVP_DigestInit_ex(ctx, hash->md, NULL)
&& EVP_DigestUpdate(ctx, tmp, tmp_sz)
&& EVP_DigestUpdate(ctx, in, inlen)
&& (in2 == NULL || EVP_DigestUpdate(ctx, in2, in2len))
&& (in3 == NULL || EVP_DigestUpdate(ctx, in3, in3len))))
return 0;
if (outlen < hash->blocklen) {
if (!EVP_DigestFinal(ctx, vtmp, NULL))
return 0;
memcpy(out, vtmp, outlen);
OPENSSL_cleanse(vtmp, hash->blocklen);
break;
} else if(!EVP_DigestFinal(ctx, out, NULL)) {
return 0;
}
outlen -= hash->blocklen;
if (outlen == 0)
break;
/* (Step 4.2) counter++ */
tmp[0]++;
out += hash->blocklen;
}
return 1;
}
/* Helper function that just passes 2 input parameters to hash_df() */
static int hash_df1(RAND_DRBG *drbg, unsigned char *out,
const unsigned char in_byte,
const unsigned char *in1, size_t in1len)
{
return hash_df(drbg, out, in_byte, in1, in1len, NULL, 0, NULL, 0);
}
/*
* Add 2 byte buffers together. The first elements in each buffer are the top
* most bytes. The result is stored in the dst buffer.
* The final carry is ignored i.e: dst = (dst + in) mod (2^seedlen_bits).
* where dst size is drbg->seedlen, and inlen <= drbg->seedlen.
*/
static int add_bytes(RAND_DRBG *drbg, unsigned char *dst,
unsigned char *in, size_t inlen)
{
size_t i;
int result;
const unsigned char *add;
unsigned char carry = 0, *d;
assert(drbg->seedlen >= 1 && inlen >= 1 && inlen <= drbg->seedlen);
d = &dst[drbg->seedlen - 1];
add = &in[inlen - 1];
for (i = inlen; i > 0; i--, d--, add--) {
result = *d + *add + carry;
carry = (unsigned char)(result >> 8);
*d = (unsigned char)(result & 0xff);
}
if (carry != 0) {
/* Add the carry to the top of the dst if inlen is not the same size */
for (i = drbg->seedlen - inlen; i > 0; --i, d--) {
*d += 1; /* Carry can only be 1 */
if (*d != 0) /* exit if carry doesnt propagate to the next byte */
break;
}
}
return 1;
}
/* V = (V + Hash(inbyte || V || [additional_input]) mod (2^seedlen) */
static int add_hash_to_v(RAND_DRBG *drbg, unsigned char inbyte,
const unsigned char *adin, size_t adinlen)
{
RAND_DRBG_HASH *hash = &drbg->data.hash;
EVP_MD_CTX *ctx = hash->ctx;
return EVP_DigestInit_ex(ctx, hash->md, NULL)
&& EVP_DigestUpdate(ctx, &inbyte, 1)
&& EVP_DigestUpdate(ctx, hash->V, drbg->seedlen)
&& (adin == NULL || EVP_DigestUpdate(ctx, adin, adinlen))
&& EVP_DigestFinal(ctx, hash->vtmp, NULL)
&& add_bytes(drbg, hash->V, hash->vtmp, hash->blocklen);
}
/*
* The Hashgen() as listed in SP800-90Ar1 10.1.1.4 Hash_DRBG_Generate_Process.
*
* drbg contains the current value of V.
* outlen is the requested number of bytes.
* out is a buffer to return the generated bits.
*
* The algorithm to generate the bits is:
* data = V
* w = NULL
* for (i = 1 to m) {
* W = W || Hash(data)
* data = (data + 1) mod (2^seedlen)
* }
* out = Leftmost(W, outlen)
*
* Returns zero if an error occurs otherwise it returns 1.
*/
static int hash_gen(RAND_DRBG *drbg, unsigned char *out, size_t outlen)
{
RAND_DRBG_HASH *hash = &drbg->data.hash;
unsigned char one = 1;
if (outlen == 0)
return 1;
memcpy(hash->vtmp, hash->V, drbg->seedlen);
for(;;) {
if (!EVP_DigestInit_ex(hash->ctx, hash->md, NULL)
|| !EVP_DigestUpdate(hash->ctx, hash->vtmp, drbg->seedlen))
return 0;
if (outlen < hash->blocklen) {
if (!EVP_DigestFinal(hash->ctx, hash->vtmp, NULL))
return 0;
memcpy(out, hash->vtmp, outlen);
return 1;
} else {
if (!EVP_DigestFinal(hash->ctx, out, NULL))
return 0;
outlen -= hash->blocklen;
if (outlen == 0)
break;
out += hash->blocklen;
}
add_bytes(drbg, hash->vtmp, &one, 1);
}
return 1;
}
/*
* SP800-90Ar1 10.1.1.2 Hash_DRBG_Instantiate_Process:
*
* ent is entropy input obtained from a randomness source of length ent_len.
* nonce is a string of bytes of length nonce_len.
* pstr is a personalization string received from an application. May be NULL.
*
* Returns zero if an error occurs otherwise it returns 1.
*/
static int drbg_hash_instantiate(RAND_DRBG *drbg,
const unsigned char *ent, size_t ent_len,
const unsigned char *nonce, size_t nonce_len,
const unsigned char *pstr, size_t pstr_len)
{
RAND_DRBG_HASH *hash = &drbg->data.hash;
/* (Step 1-3) V = Hash_df(entropy||nonce||pers, seedlen) */
return hash_df(drbg, hash->V, INBYTE_IGNORE,
ent, ent_len, nonce, nonce_len, pstr, pstr_len)
/* (Step 4) C = Hash_df(0x00||V, seedlen) */
&& hash_df1(drbg, hash->C, 0x00, hash->V, drbg->seedlen);
}
/*
* SP800-90Ar1 10.1.1.3 Hash_DRBG_Reseed_Process:
*
* ent is entropy input bytes obtained from a randomness source.
* addin is additional input received from an application. May be NULL.
*
* Returns zero if an error occurs otherwise it returns 1.
*/
static int drbg_hash_reseed(RAND_DRBG *drbg,
const unsigned char *ent, size_t ent_len,
const unsigned char *adin, size_t adin_len)
{
RAND_DRBG_HASH *hash = &drbg->data.hash;
/* (Step 1-2) V = Hash_df(0x01 || V || entropy_input || additional_input)*/
/* V about to be updated so use C as output instead */
if (!hash_df(drbg, hash->C, 0x01, hash->V, drbg->seedlen, ent, ent_len,
adin, adin_len))
return 0;
memcpy(hash->V, hash->C, drbg->seedlen);
/* (Step 4) C = Hash_df(0x00||V, seedlen) */
return hash_df1(drbg, hash->C, 0x00, hash->V, drbg->seedlen);
}
/*
* SP800-90Ar1 10.1.1.4 Hash_DRBG_Generate_Process:
*
* Generates pseudo random bytes using the drbg.
* out is a buffer to fill with outlen bytes of pseudo random data.
* addin is additional input received from an application. May be NULL.
*
* Returns zero if an error occurs otherwise it returns 1.
*/
static int drbg_hash_generate(RAND_DRBG *drbg,
unsigned char *out, size_t outlen,
const unsigned char *adin, size_t adin_len)
{
RAND_DRBG_HASH *hash = &drbg->data.hash;
unsigned char counter[4];
int reseed_counter = drbg->reseed_gen_counter;
counter[0] = (unsigned char)((reseed_counter >> 24) & 0xff);
counter[1] = (unsigned char)((reseed_counter >> 16) & 0xff);
counter[2] = (unsigned char)((reseed_counter >> 8) & 0xff);
counter[3] = (unsigned char)(reseed_counter & 0xff);
return (adin == NULL
/* (Step 2) if adin != NULL then V = V + Hash(0x02||V||adin) */
|| adin_len == 0
|| add_hash_to_v(drbg, 0x02, adin, adin_len))
/* (Step 3) Hashgen(outlen, V) */
&& hash_gen(drbg, out, outlen)
/* (Step 4/5) H = V = (V + Hash(0x03||V) mod (2^seedlen_bits) */
&& add_hash_to_v(drbg, 0x03, NULL, 0)
/* (Step 5) V = (V + H + C + reseed_counter) mod (2^seedlen_bits) */
/* V = (V + C) mod (2^seedlen_bits) */
&& add_bytes(drbg, hash->V, hash->C, drbg->seedlen)
/* V = (V + reseed_counter) mod (2^seedlen_bits) */
&& add_bytes(drbg, hash->V, counter, 4);
}
static int drbg_hash_uninstantiate(RAND_DRBG *drbg)
{
EVP_MD_CTX_free(drbg->data.hash.ctx);
OPENSSL_cleanse(&drbg->data.hash, sizeof(drbg->data.hash));
return 1;
}
static RAND_DRBG_METHOD drbg_hash_meth = {
drbg_hash_instantiate,
drbg_hash_reseed,
drbg_hash_generate,
drbg_hash_uninstantiate
};
int drbg_hash_init(RAND_DRBG *drbg)
{
const EVP_MD *md;
RAND_DRBG_HASH *hash = &drbg->data.hash;
/* Any approved digest is allowed */
md = EVP_get_digestbynid(drbg->type);
if (md == NULL)
return 0;
drbg->meth = &drbg_hash_meth;
hash->md = md;
if (hash->ctx == NULL) {
hash->ctx = EVP_MD_CTX_new();
if (hash->ctx == NULL)
return 0;
}
/* These are taken from SP 800-90 10.1 Table 2 */
hash->blocklen = EVP_MD_size(md);
/* See SP800-57 Part1 Rev4 5.6.1 Table 3 */
drbg->strength = 64 * (hash->blocklen >> 3);
if (drbg->strength > 256)
drbg->strength = 256;
if (hash->blocklen > MAX_BLOCKLEN_USING_SMALL_SEEDLEN)
drbg->seedlen = HASH_PRNG_MAX_SEEDLEN;
else
drbg->seedlen = HASH_PRNG_SMALL_SEEDLEN;
drbg->min_entropylen = drbg->strength / 8;
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;
/* Maximum number of bits per request = 2^19 = 2^16 bytes */
drbg->max_request = 1 << 16;
return 1;
}