1 /* 2 * Copyright 1995-2021 The OpenSSL Project Authors. All Rights Reserved. 3 * 4 * Licensed under the Apache License 2.0 (the "License"). You may not use 5 * this file except in compliance with the License. You can obtain a copy 6 * in the file LICENSE in the source distribution or at 7 * https://www.openssl.org/source/license.html 8 */ 9 10 #ifndef OSSL_PROVIDER_RAND_POOL_H 11 # define OSSL_PROVIDER_RAND_POOL_H 12 # pragma once 13 14 # include <stdio.h> 15 # include <openssl/rand.h> 16 17 /* 18 * Maximum allocation size for RANDOM_POOL buffers 19 * 20 * The max_len value for the buffer provided to the rand_drbg_get_entropy() 21 * callback is currently 2^31 bytes (2 gigabytes), if a derivation function 22 * is used. Since this is much too large to be allocated, the ossl_rand_pool_new() 23 * function chooses more modest values as default pool length, bounded 24 * by RAND_POOL_MIN_LENGTH and RAND_POOL_MAX_LENGTH 25 * 26 * The choice of the RAND_POOL_FACTOR is large enough such that the 27 * RAND_POOL can store a random input which has a lousy entropy rate of 28 * 8/256 (= 0.03125) bits per byte. This input will be sent through the 29 * derivation function which 'compresses' the low quality input into a 30 * high quality output. 31 * 32 * The factor 1.5 below is the pessimistic estimate for the extra amount 33 * of entropy required when no get_nonce() callback is defined. 34 */ 35 # define RAND_POOL_FACTOR 256 36 # define RAND_POOL_MAX_LENGTH (RAND_POOL_FACTOR * \ 37 3 * (RAND_DRBG_STRENGTH / 16)) 38 /* 39 * = (RAND_POOL_FACTOR * \ 40 * 1.5 * (RAND_DRBG_STRENGTH / 8)) 41 */ 42 43 /* 44 * Initial allocation minimum. 45 * 46 * There is a distinction between the secure and normal allocation minimums. 47 * Ideally, the secure allocation size should be a power of two. The normal 48 * allocation size doesn't have any such restriction. 49 * 50 * The secure value is based on 128 bits of secure material, which is 16 bytes. 51 * Typically, the DRBGs will set a minimum larger than this so optimal 52 * allocation ought to take place (for full quality seed material). 53 * 54 * The normal value has been chosen by noticing that the rand_drbg_get_nonce 55 * function is usually the largest of the built in allocation (twenty four 56 * bytes and then appending another sixteen bytes). This means the buffer ends 57 * with 40 bytes. The value of forty eight is comfortably above this which 58 * allows some slack in the platform specific values used. 59 */ 60 # define RAND_POOL_MIN_ALLOCATION(secure) ((secure) ? 16 : 48) 61 62 /* 63 * The 'random pool' acts as a dumb container for collecting random 64 * input from various entropy sources. It is the callers duty to 1) initialize 65 * the random pool, 2) pass it to the polling callbacks, 3) seed the RNG, and 66 * 4) cleanup the random pool again. 67 * 68 * The random pool contains no locking mechanism because its scope and 69 * lifetime is intended to be restricted to a single stack frame. 70 */ 71 typedef struct rand_pool_st { 72 unsigned char *buffer; /* points to the beginning of the random pool */ 73 size_t len; /* current number of random bytes contained in the pool */ 74 75 int attached; /* true pool was attached to existing buffer */ 76 int secure; /* 1: allocated on the secure heap, 0: otherwise */ 77 78 size_t min_len; /* minimum number of random bytes requested */ 79 size_t max_len; /* maximum number of random bytes (allocated buffer size) */ 80 size_t alloc_len; /* current number of bytes allocated */ 81 size_t entropy; /* current entropy count in bits */ 82 size_t entropy_requested; /* requested entropy count in bits */ 83 } RAND_POOL; 84 85 RAND_POOL *ossl_rand_pool_new(int entropy_requested, int secure, 86 size_t min_len, size_t max_len); 87 RAND_POOL *ossl_rand_pool_attach(const unsigned char *buffer, size_t len, 88 size_t entropy); 89 void ossl_rand_pool_free(RAND_POOL *pool); 90 91 const unsigned char *ossl_rand_pool_buffer(RAND_POOL *pool); 92 unsigned char *ossl_rand_pool_detach(RAND_POOL *pool); 93 void ossl_rand_pool_reattach(RAND_POOL *pool, unsigned char *buffer); 94 95 size_t ossl_rand_pool_entropy(RAND_POOL *pool); 96 size_t ossl_rand_pool_length(RAND_POOL *pool); 97 98 size_t ossl_rand_pool_entropy_available(RAND_POOL *pool); 99 size_t ossl_rand_pool_entropy_needed(RAND_POOL *pool); 100 /* |entropy_factor| expresses how many bits of data contain 1 bit of entropy */ 101 size_t ossl_rand_pool_bytes_needed(RAND_POOL *pool, unsigned int entropy_factor); 102 size_t ossl_rand_pool_bytes_remaining(RAND_POOL *pool); 103 104 int ossl_rand_pool_add(RAND_POOL *pool, 105 const unsigned char *buffer, size_t len, size_t entropy); 106 unsigned char *ossl_rand_pool_add_begin(RAND_POOL *pool, size_t len); 107 int ossl_rand_pool_add_end(RAND_POOL *pool, size_t len, size_t entropy); 108 109 #endif /* OSSL_PROVIDER_RAND_POOL_H */ 110