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082193ef2b
This patch fixes two issues in the ia32 RDRAND assembly code that result in a (possibly significant) loss of entropy. The first, less significant, issue is that, by returning success as 0 from OPENSSL_ia32_rdrand() and OPENSSL_ia32_rdseed(), a subtle bias was introduced. Specifically, because the assembly routine copied the remaining number of retries over the result when RDRAND/RDSEED returned 'successful but zero', a bias towards values 1-8 (primarily 8) was introduced. The second, more worrying issue was that, due to a mixup in registers, when a buffer that was not size 0 or 1 mod 8 was passed to OPENSSL_ia32_rdrand_bytes or OPENSSL_ia32_rdseed_bytes, the last (n mod 8) bytes were all the same value. This issue impacts only the 64-bit variant of the assembly. This change fixes both issues by first eliminating the only use of OPENSSL_ia32_rdrand, replacing it with OPENSSL_ia32_rdrand_bytes, and fixes the register mixup in OPENSSL_ia32_rdrand_bytes. It also adds a sanity test for OPENSSL_ia32_rdrand_bytes and OPENSSL_ia32_rdseed_bytes to help catch problems of this nature in the future. Reviewed-by: Andy Polyakov <appro@openssl.org> Reviewed-by: Rich Salz <rsalz@openssl.org> (Merged from https://github.com/openssl/openssl/pull/5342)
98 lines
2.3 KiB
C
98 lines
2.3 KiB
C
/*
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* Copyright 2011-2018 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the OpenSSL license (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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#include <openssl/opensslconf.h>
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#include <stdio.h>
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#include <string.h>
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#include "internal/engine.h"
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#include <openssl/rand.h>
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#include <openssl/err.h>
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#include <openssl/crypto.h>
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#if (defined(__i386) || defined(__i386__) || defined(_M_IX86) || \
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defined(__x86_64) || defined(__x86_64__) || \
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defined(_M_AMD64) || defined (_M_X64)) && defined(OPENSSL_CPUID_OBJ)
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size_t OPENSSL_ia32_rdrand_bytes(unsigned char *buf, size_t len);
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static int get_random_bytes(unsigned char *buf, int num)
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{
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if (num < 0) {
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return 0;
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}
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return (size_t)num == OPENSSL_ia32_rdrand_bytes(buf, (size_t)num);
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}
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static int random_status(void)
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{
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return 1;
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}
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static RAND_METHOD rdrand_meth = {
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NULL, /* seed */
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get_random_bytes,
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NULL, /* cleanup */
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NULL, /* add */
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get_random_bytes,
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random_status,
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};
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static int rdrand_init(ENGINE *e)
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{
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return 1;
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}
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static const char *engine_e_rdrand_id = "rdrand";
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static const char *engine_e_rdrand_name = "Intel RDRAND engine";
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static int bind_helper(ENGINE *e)
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{
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if (!ENGINE_set_id(e, engine_e_rdrand_id) ||
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!ENGINE_set_name(e, engine_e_rdrand_name) ||
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!ENGINE_set_flags(e, ENGINE_FLAGS_NO_REGISTER_ALL) ||
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!ENGINE_set_init_function(e, rdrand_init) ||
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!ENGINE_set_RAND(e, &rdrand_meth))
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return 0;
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return 1;
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}
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static ENGINE *ENGINE_rdrand(void)
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{
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ENGINE *ret = ENGINE_new();
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if (ret == NULL)
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return NULL;
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if (!bind_helper(ret)) {
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ENGINE_free(ret);
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return NULL;
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}
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return ret;
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}
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void engine_load_rdrand_int(void)
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{
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extern unsigned int OPENSSL_ia32cap_P[];
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if (OPENSSL_ia32cap_P[1] & (1 << (62 - 32))) {
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ENGINE *toadd = ENGINE_rdrand();
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if (!toadd)
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return;
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ENGINE_add(toadd);
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ENGINE_free(toadd);
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ERR_clear_error();
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}
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}
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#else
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void engine_load_rdrand_int(void)
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{
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}
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#endif
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