/* * 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 */