/*
* Copyright 1995-2021 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 <stdio.h>
#include <time.h>
#include "internal/cryptlib.h"
#include <openssl/opensslconf.h>
#include "crypto/rand.h"
#include <openssl/engine.h>
#include "internal/thread_once.h"
#include "crypto/rand_pool.h"
/*
* Allocate memory and initialize a new random pool
*/
RAND_POOL *ossl_rand_pool_new(int entropy_requested, int secure,
size_t min_len, size_t max_len)
{
RAND_POOL *pool = OPENSSL_zalloc(sizeof(*pool));
size_t min_alloc_size = RAND_POOL_MIN_ALLOCATION(secure);
if (pool == NULL)
return NULL;
pool->min_len = min_len;
pool->max_len = (max_len > RAND_POOL_MAX_LENGTH) ?
RAND_POOL_MAX_LENGTH : max_len;
pool->alloc_len = min_len < min_alloc_size ? min_alloc_size : min_len;
if (pool->alloc_len > pool->max_len)
pool->alloc_len = pool->max_len;
if (secure)
pool->buffer = OPENSSL_secure_zalloc(pool->alloc_len);
else
pool->buffer = OPENSSL_zalloc(pool->alloc_len);
if (pool->buffer == NULL)
goto err;
pool->entropy_requested = entropy_requested;
pool->secure = secure;
return pool;
err:
OPENSSL_free(pool);
return NULL;
}
/*
* Attach new random pool to the given buffer
*
* This function is intended to be used only for feeding random data
* provided by RAND_add() and RAND_seed() into the <master> DRBG.
*/
RAND_POOL *ossl_rand_pool_attach(const unsigned char *buffer, size_t len,
size_t entropy)
{
RAND_POOL *pool = OPENSSL_zalloc(sizeof(*pool));
if (pool == NULL)
return NULL;
/*
* The const needs to be cast away, but attached buffers will not be
* modified (in contrary to allocated buffers which are zeroed and
* freed in the end).
*/
pool->buffer = (unsigned char *) buffer;
pool->len = len;
pool->attached = 1;
pool->min_len = pool->max_len = pool->alloc_len = pool->len;
pool->entropy = entropy;
return pool;
}
/*
* Free |pool|, securely erasing its buffer.
*/
void ossl_rand_pool_free(RAND_POOL *pool)
{
if (pool == NULL)
return;
/*
* Although it would be advisable from a cryptographical viewpoint,
* we are not allowed to clear attached buffers, since they are passed
* to ossl_rand_pool_attach() as `const unsigned char*`.
* (see corresponding comment in ossl_rand_pool_attach()).
*/
if (!pool->attached) {
if (pool->secure)
OPENSSL_secure_clear_free(pool->buffer, pool->alloc_len);
else
OPENSSL_clear_free(pool->buffer, pool->alloc_len);
}
OPENSSL_free(pool);
}
/*
* Return the |pool|'s buffer to the caller (readonly).
*/
const unsigned char *ossl_rand_pool_buffer(RAND_POOL *pool)
{
return pool->buffer;
}
/*
* Return the |pool|'s entropy to the caller.
*/
size_t ossl_rand_pool_entropy(RAND_POOL *pool)
{
return pool->entropy;
}
/*
* Return the |pool|'s buffer length to the caller.
*/
size_t ossl_rand_pool_length(RAND_POOL *pool)
{
return pool->len;
}
/*
* Detach the |pool| buffer and return it to the caller.
* It's the responsibility of the caller to free the buffer
* using OPENSSL_secure_clear_free() or to re-attach it
* again to the pool using ossl_rand_pool_reattach().
*/
unsigned char *ossl_rand_pool_detach(RAND_POOL *pool)
{
unsigned char *ret = pool->buffer;
pool->buffer = NULL;
pool->entropy = 0;
return ret;
}
/*
* Re-attach the |pool| buffer. It is only allowed to pass
* the |buffer| which was previously detached from the same pool.
*/
void ossl_rand_pool_reattach(RAND_POOL *pool, unsigned char *buffer)
{
pool->buffer = buffer;
OPENSSL_cleanse(pool->buffer, pool->len);
pool->len = 0;
}
/*
* If |entropy_factor| bits contain 1 bit of entropy, how many bytes does one
* need to obtain at least |bits| bits of entropy?
*/
#define ENTROPY_TO_BYTES(bits, entropy_factor) \
(((bits) * (entropy_factor) + 7) / 8)
/*
* Checks whether the |pool|'s entropy is available to the caller.
* This is the case when entropy count and buffer length are high enough.
* Returns
*
* |entropy| if the entropy count and buffer size is large enough
* 0 otherwise
*/
size_t ossl_rand_pool_entropy_available(RAND_POOL *pool)
{
if (pool->entropy < pool->entropy_requested)
return 0;
if (pool->len < pool->min_len)
return 0;
return pool->entropy;
}
/*
* Returns the (remaining) amount of entropy needed to fill
* the random pool.
*/
size_t ossl_rand_pool_entropy_needed(RAND_POOL *pool)
{
if (pool->entropy < pool->entropy_requested)
return pool->entropy_requested - pool->entropy;
return 0;
}
/* Increase the allocation size -- not usable for an attached pool */
static int rand_pool_grow(RAND_POOL *pool, size_t len)
{
if (len > pool->alloc_len - pool->len) {
unsigned char *p;
const size_t limit = pool->max_len / 2;
size_t newlen = pool->alloc_len;
if (pool->attached || len > pool->max_len - pool->len) {
ERR_raise(ERR_LIB_RAND, ERR_R_INTERNAL_ERROR);
return 0;
}
do
newlen = newlen < limit ? newlen * 2 : pool->max_len;
while (len > newlen - pool->len);
if (pool->secure)
p = OPENSSL_secure_zalloc(newlen);
else
p = OPENSSL_zalloc(newlen);
if (p == NULL)
return 0;
memcpy(p, pool->buffer, pool->len);
if (pool->secure)
OPENSSL_secure_clear_free(pool->buffer, pool->alloc_len);
else
OPENSSL_clear_free(pool->buffer, pool->alloc_len);
pool->buffer = p;
pool->alloc_len = newlen;
}
return 1;
}
/*
* Returns the number of bytes needed to fill the pool, assuming
* the input has 1 / |entropy_factor| entropy bits per data bit.
* In case of an error, 0 is returned.
*/
size_t ossl_rand_pool_bytes_needed(RAND_POOL *pool, unsigned int entropy_factor)
{
size_t bytes_needed;
size_t entropy_needed = ossl_rand_pool_entropy_needed(pool);
if (entropy_factor < 1) {
ERR_raise(ERR_LIB_RAND, RAND_R_ARGUMENT_OUT_OF_RANGE);
return 0;
}
bytes_needed = ENTROPY_TO_BYTES(entropy_needed, entropy_factor);
if (bytes_needed > pool->max_len - pool->len) {
/* not enough space left */
ERR_raise_data(ERR_LIB_RAND, RAND_R_RANDOM_POOL_OVERFLOW,
"entropy_factor=%u, entropy_needed=%zu, bytes_needed=%zu,"
"pool->max_len=%zu, pool->len=%zu",
entropy_factor, entropy_needed, bytes_needed,
pool->max_len, pool->len);
return 0;
}
if (pool->len < pool->min_len &&
bytes_needed < pool->min_len - pool->len)
/* to meet the min_len requirement */
bytes_needed = pool->min_len - pool->len;
/*
* Make sure the buffer is large enough for the requested amount
* of data. This guarantees that existing code patterns where
* ossl_rand_pool_add_begin, ossl_rand_pool_add_end or ossl_rand_pool_add
* are used to collect entropy data without any error handling
* whatsoever, continue to be valid.
* Furthermore if the allocation here fails once, make sure that
* we don't fall back to a less secure or even blocking random source,
* as that could happen by the existing code patterns.
* This is not a concern for additional data, therefore that
* is not needed if rand_pool_grow fails in other places.
*/
if (!rand_pool_grow(pool, bytes_needed)) {
/* persistent error for this pool */
pool->max_len = pool->len = 0;
return 0;
}
return bytes_needed;
}
/* Returns the remaining number of bytes available */
size_t ossl_rand_pool_bytes_remaining(RAND_POOL *pool)
{
return pool->max_len - pool->len;
}
/*
* Add random bytes to the random pool.
*
* It is expected that the |buffer| contains |len| bytes of
* random input which contains at least |entropy| bits of
* randomness.
*
* Returns 1 if the added amount is adequate, otherwise 0
*/
int ossl_rand_pool_add(RAND_POOL *pool,
const unsigned char *buffer, size_t len, size_t entropy)
{
if (len > pool->max_len - pool->len) {
ERR_raise(ERR_LIB_RAND, RAND_R_ENTROPY_INPUT_TOO_LONG);
return 0;
}
if (pool->buffer == NULL) {
ERR_raise(ERR_LIB_RAND, ERR_R_INTERNAL_ERROR);
return 0;
}
if (len > 0) {
/*
* This is to protect us from accidentally passing the buffer
* returned from ossl_rand_pool_add_begin.
* The check for alloc_len makes sure we do not compare the
* address of the end of the allocated memory to something
* different, since that comparison would have an
* indeterminate result.
*/
if (pool->alloc_len > pool->len && pool->buffer + pool->len == buffer) {
ERR_raise(ERR_LIB_RAND, ERR_R_INTERNAL_ERROR);
return 0;
}
/*
* We have that only for cases when a pool is used to collect
* additional data.
* For entropy data, as long as the allocation request stays within
* the limits given by ossl_rand_pool_bytes_needed this rand_pool_grow
* below is guaranteed to succeed, thus no allocation happens.
*/
if (!rand_pool_grow(pool, len))
return 0;
memcpy(pool->buffer + pool->len, buffer, len);
pool->len += len;
pool->entropy += entropy;
}
return 1;
}
/*
* Start to add random bytes to the random pool in-place.
*
* Reserves the next |len| bytes for adding random bytes in-place
* and returns a pointer to the buffer.
* The caller is allowed to copy up to |len| bytes into the buffer.
* If |len| == 0 this is considered a no-op and a NULL pointer
* is returned without producing an error message.
*
* After updating the buffer, ossl_rand_pool_add_end() needs to be called
* to finish the update operation (see next comment).
*/
unsigned char *ossl_rand_pool_add_begin(RAND_POOL *pool, size_t len)
{
if (len == 0)
return NULL;
if (len > pool->max_len - pool->len) {
ERR_raise(ERR_LIB_RAND, RAND_R_RANDOM_POOL_OVERFLOW);
return NULL;
}
if (pool->buffer == NULL) {
ERR_raise(ERR_LIB_RAND, ERR_R_INTERNAL_ERROR);
return NULL;
}
/*
* As long as the allocation request stays within the limits given
* by ossl_rand_pool_bytes_needed this rand_pool_grow below is guaranteed
* to succeed, thus no allocation happens.
* We have that only for cases when a pool is used to collect
* additional data. Then the buffer might need to grow here,
* and of course the caller is responsible to check the return
* value of this function.
*/
if (!rand_pool_grow(pool, len))
return NULL;
return pool->buffer + pool->len;
}
/*
* Finish to add random bytes to the random pool in-place.
*
* Finishes an in-place update of the random pool started by
* ossl_rand_pool_add_begin() (see previous comment).
* It is expected that |len| bytes of random input have been added
* to the buffer which contain at least |entropy| bits of randomness.
* It is allowed to add less bytes than originally reserved.
*/
int ossl_rand_pool_add_end(RAND_POOL *pool, size_t len, size_t entropy)
{
if (len > pool->alloc_len - pool->len) {
ERR_raise(ERR_LIB_RAND, RAND_R_RANDOM_POOL_OVERFLOW);
return 0;
}
if (len > 0) {
pool->len += len;
pool->entropy += entropy;
}
return 1;
}
