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/*
* 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
*/
#ifndef OSSL_PROVIDER_RAND_POOL_H
# define OSSL_PROVIDER_RAND_POOL_H
# pragma once
# include <stdio.h>
# include <openssl/rand.h>
/*
* Maximum allocation size for RANDOM_POOL buffers
*
* The max_len value for the buffer provided to the rand_drbg_get_entropy()
* callback is currently 2^31 bytes (2 gigabytes), if a derivation function
* is used. Since this is much too large to be allocated, the ossl_rand_pool_new()
* function chooses more modest values as default pool length, bounded
* by RAND_POOL_MIN_LENGTH and RAND_POOL_MAX_LENGTH
*
* The choice of the RAND_POOL_FACTOR is large enough such that the
* RAND_POOL can store a random input which has a lousy entropy rate of
* 8/256 (= 0.03125) bits per byte. This input will be sent through the
* derivation function which 'compresses' the low quality input into a
* high quality output.
*
* The factor 1.5 below is the pessimistic estimate for the extra amount
* of entropy required when no get_nonce() callback is defined.
*/
# define RAND_POOL_FACTOR 256
# define RAND_POOL_MAX_LENGTH (RAND_POOL_FACTOR * \
3 * (RAND_DRBG_STRENGTH / 16))
/*
* = (RAND_POOL_FACTOR * \
* 1.5 * (RAND_DRBG_STRENGTH / 8))
*/
/*
* Initial allocation minimum.
*
* There is a distinction between the secure and normal allocation minimums.
* Ideally, the secure allocation size should be a power of two. The normal
* allocation size doesn't have any such restriction.
*
* The secure value is based on 128 bits of secure material, which is 16 bytes.
* Typically, the DRBGs will set a minimum larger than this so optimal
* allocation ought to take place (for full quality seed material).
*
* The normal value has been chosen by noticing that the rand_drbg_get_nonce
* function is usually the largest of the built in allocation (twenty four
* bytes and then appending another sixteen bytes). This means the buffer ends
* with 40 bytes. The value of forty eight is comfortably above this which
* allows some slack in the platform specific values used.
*/
# define RAND_POOL_MIN_ALLOCATION(secure) ((secure) ? 16 : 48)
/*
* The 'random pool' acts as a dumb container for collecting random
* input from various entropy sources. It is the callers duty to 1) initialize
* the random pool, 2) pass it to the polling callbacks, 3) seed the RNG, and
* 4) cleanup the random pool again.
*
* The random pool contains no locking mechanism because its scope and
* lifetime is intended to be restricted to a single stack frame.
*/
typedef struct rand_pool_st {
unsigned char *buffer; /* points to the beginning of the random pool */
size_t len; /* current number of random bytes contained in the pool */
int attached; /* true pool was attached to existing buffer */
int secure; /* 1: allocated on the secure heap, 0: otherwise */
size_t min_len; /* minimum number of random bytes requested */
size_t max_len; /* maximum number of random bytes (allocated buffer size) */
size_t alloc_len; /* current number of bytes allocated */
size_t entropy; /* current entropy count in bits */
size_t entropy_requested; /* requested entropy count in bits */
} RAND_POOL;
RAND_POOL *ossl_rand_pool_new(int entropy_requested, int secure,
size_t min_len, size_t max_len);
RAND_POOL *ossl_rand_pool_attach(const unsigned char *buffer, size_t len,
size_t entropy);
void ossl_rand_pool_free(RAND_POOL *pool);
const unsigned char *ossl_rand_pool_buffer(RAND_POOL *pool);
unsigned char *ossl_rand_pool_detach(RAND_POOL *pool);
void ossl_rand_pool_reattach(RAND_POOL *pool, unsigned char *buffer);
size_t ossl_rand_pool_entropy(RAND_POOL *pool);
size_t ossl_rand_pool_length(RAND_POOL *pool);
size_t ossl_rand_pool_entropy_available(RAND_POOL *pool);
size_t ossl_rand_pool_entropy_needed(RAND_POOL *pool);
/* |entropy_factor| expresses how many bits of data contain 1 bit of entropy */
size_t ossl_rand_pool_bytes_needed(RAND_POOL *pool, unsigned int entropy_factor);
size_t ossl_rand_pool_bytes_remaining(RAND_POOL *pool);
int ossl_rand_pool_add(RAND_POOL *pool,
const unsigned char *buffer, size_t len, size_t entropy);
unsigned char *ossl_rand_pool_add_begin(RAND_POOL *pool, size_t len);
int ossl_rand_pool_add_end(RAND_POOL *pool, size_t len, size_t entropy);
#endif /* OSSL_PROVIDER_RAND_POOL_H */
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