1 /* 2 * Copyright 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 #include "internal/cryptlib.h" 11 #include <openssl/opensslconf.h> 12 #include "crypto/rand_pool.h" 13 #include "prov/seeding.h" 14 15 16 #ifdef OPENSSL_RAND_SEED_RDCPU 17 #include "crypto/arm_arch.h" 18 19 size_t OPENSSL_rndrrs_bytes(unsigned char *buf, size_t len); 20 21 static size_t get_hardware_random_value(unsigned char *buf, size_t len); 22 23 /* 24 * Acquire entropy using Arm-specific cpu instructions 25 * 26 * Uses the RNDRRS instruction. RNDR is never needed since 27 * RNDRRS will always be available if RNDR is an available 28 * instruction. 29 * 30 * Returns the total entropy count, if it exceeds the requested 31 * entropy count. Otherwise, returns an entropy count of 0. 32 */ 33 size_t ossl_prov_acquire_entropy_from_cpu(RAND_POOL *pool) 34 { 35 size_t bytes_needed; 36 unsigned char *buffer; 37 38 bytes_needed = ossl_rand_pool_bytes_needed(pool, 1 /*entropy_factor*/); 39 if (bytes_needed > 0) { 40 buffer = ossl_rand_pool_add_begin(pool, bytes_needed); 41 42 if (buffer != NULL) { 43 if (get_hardware_random_value(buffer, bytes_needed) == bytes_needed) 44 ossl_rand_pool_add_end(pool, bytes_needed, 8 * bytes_needed); 45 else 46 ossl_rand_pool_add_end(pool, 0, 0); 47 } 48 } 49 50 return ossl_rand_pool_entropy_available(pool); 51 } 52 53 static size_t get_hardware_random_value(unsigned char *buf, size_t len) 54 { 55 /* Always use RNDRRS or nothing */ 56 if (OPENSSL_armcap_P & ARMV8_RNG) { 57 if (OPENSSL_rndrrs_bytes(buf, len) != len) 58 return 0; 59 } else { 60 return 0; 61 } 62 return len; 63 } 64 65 #else 66 NON_EMPTY_TRANSLATION_UNIT 67 #endif /* OPENSSL_RAND_SEED_RDCPU */ 68