kris/boringssl
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Update constant-time operations.

Browse Source 
(Based on upstream's 42af669ff2754dfbe1dd55a0ab56664f82284dc4)

Change-Id: I4d3954fea7471e274c626483a0dfb9d7b3250b74
This commit is contained in:
Adam Langley 2014-11-04 11:22:01 -08:00
parent a0b74eb241
commit 9ed9dae18e
3 changed files with 354 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

307
crypto/constant_time_test.c Normal file
View File

@ -0,0 +1,307 @@
/*
* Utilities for constant-time cryptography.
*
* Author: Emilia Kasper (emilia@openssl.org)
* Based on previous work by Bodo Moeller, Emilia Kasper, Adam Langley
* (Google).
* ====================================================================
* Copyright (c) 2014 The OpenSSL Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* "This product includes cryptographic software written by
* Eric Young (eay@cryptsoft.com)"
* The word 'cryptographic' can be left out if the rouines from the library
* being used are not cryptographic related :-).
* 4. If you include any Windows specific code (or a derivative thereof) from
* the apps directory (application code) you must include an acknowledgement:
* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
*
* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* The licence and distribution terms for any publically available version or
* derivative of this code cannot be changed. i.e. this code cannot simply be
* copied and put under another distribution licence
* [including the GNU Public Licence.]
*/
#include "internal.h"
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
static const unsigned int CONSTTIME_TRUE = (unsigned)(~0);
static const unsigned int CONSTTIME_FALSE = 0;
static const uint8_t CONSTTIME_TRUE_8 = 0xff;
static const uint8_t CONSTTIME_FALSE_8 = 0;
static int test_binary_op(unsigned int (*op)(unsigned int a, unsigned int b),
const char* op_name, unsigned int a, unsigned int b,
int is_true) {
unsigned c = op(a, b);
if (is_true && c != CONSTTIME_TRUE) {
fprintf(stderr,
"Test failed for %s(%du, %du): expected %du (TRUE), got %du\n",
op_name, a, b, CONSTTIME_TRUE, c);
return 1;
} else if (!is_true && c != CONSTTIME_FALSE) {
fprintf(stderr,
"Test failed for %s(%du, %du): expected %du (FALSE), got %du\n",
op_name, a, b, CONSTTIME_FALSE, c);
return 1;
}
return 0;
}
static int test_binary_op_8(uint8_t (*op)(unsigned int a, unsigned int b),
const char* op_name, unsigned int a, unsigned int b,
int is_true) {
uint8_t c = op(a, b);
if (is_true && c != CONSTTIME_TRUE_8) {
fprintf(stderr,
"Test failed for %s(%du, %du): expected %u (TRUE), got %u\n",
op_name, a, b, CONSTTIME_TRUE_8, c);
return 1;
} else if (!is_true && c != CONSTTIME_FALSE_8) {
fprintf(stderr,
"Test failed for %s(%du, %du): expected %u (FALSE), got %u\n",
op_name, a, b, CONSTTIME_FALSE_8, c);
return 1;
}
return 0;
}
static int test_is_zero(unsigned int a) {
unsigned int c = constant_time_is_zero(a);
if (a == 0 && c != CONSTTIME_TRUE) {
fprintf(stderr,
"Test failed for constant_time_is_zero(%du): expected %du (TRUE), "
"got %du\n",
a, CONSTTIME_TRUE, c);
return 1;
} else if (a != 0 && c != CONSTTIME_FALSE) {
fprintf(stderr,
"Test failed for constant_time_is_zero(%du): expected %du (FALSE), "
"got %du\n",
a, CONSTTIME_FALSE, c);
return 1;
}
return 0;
}
static int test_is_zero_8(unsigned int a) {
uint8_t c = constant_time_is_zero_8(a);
if (a == 0 && c != CONSTTIME_TRUE_8) {
fprintf(stderr,
"Test failed for constant_time_is_zero(%du): expected %u (TRUE), "
"got %u\n",
a, CONSTTIME_TRUE_8, c);
return 1;
} else if (a != 0 && c != CONSTTIME_FALSE) {
fprintf(stderr,
"Test failed for constant_time_is_zero(%du): expected %u (FALSE), "
"got %u\n",
a, CONSTTIME_FALSE_8, c);
return 1;
}
return 0;
}
static int test_select(unsigned int a, unsigned int b) {
unsigned int selected = constant_time_select(CONSTTIME_TRUE, a, b);
if (selected != a) {
fprintf(stderr,
"Test failed for constant_time_select(%du, %du,"
"%du): expected %du(first value), got %du\n",
CONSTTIME_TRUE, a, b, a, selected);
return 1;
}
selected = constant_time_select(CONSTTIME_FALSE, a, b);
if (selected != b) {
fprintf(stderr,
"Test failed for constant_time_select(%du, %du,"
"%du): expected %du(second value), got %du\n",
CONSTTIME_FALSE, a, b, b, selected);
return 1;
}
return 0;
}
static int test_select_8(uint8_t a, uint8_t b) {
uint8_t selected = constant_time_select_8(CONSTTIME_TRUE_8, a, b);
if (selected != a) {
fprintf(stderr,
"Test failed for constant_time_select(%u, %u,"
"%u): expected %u(first value), got %u\n",
CONSTTIME_TRUE, a, b, a, selected);
return 1;
}
selected = constant_time_select_8(CONSTTIME_FALSE_8, a, b);
if (selected != b) {
fprintf(stderr,
"Test failed for constant_time_select(%u, %u,"
"%u): expected %u(second value), got %u\n",
CONSTTIME_FALSE, a, b, b, selected);
return 1;
}
return 0;
}
static int test_select_int(int a, int b) {
int selected = constant_time_select_int(CONSTTIME_TRUE, a, b);
if (selected != a) {
fprintf(stderr,
"Test failed for constant_time_select(%du, %d,"
"%d): expected %d(first value), got %d\n",
CONSTTIME_TRUE, a, b, a, selected);
return 1;
}
selected = constant_time_select_int(CONSTTIME_FALSE, a, b);
if (selected != b) {
fprintf(stderr,
"Test failed for constant_time_select(%du, %d,"
"%d): expected %d(second value), got %d\n",
CONSTTIME_FALSE, a, b, b, selected);
return 1;
}
return 0;
}
static int test_eq_int(int a, int b) {
unsigned int equal = constant_time_eq_int(a, b);
if (a == b && equal != CONSTTIME_TRUE) {
fprintf(stderr,
"Test failed for constant_time_eq_int(%d, %d): expected %du(TRUE), "
"got %du\n",
a, b, CONSTTIME_TRUE, equal);
return 1;
} else if (a != b && equal != CONSTTIME_FALSE) {
fprintf(stderr,
"Test failed for constant_time_eq_int(%d, %d): expected "
"%du(FALSE), got %du\n",
a, b, CONSTTIME_FALSE, equal);
return 1;
}
return 0;
}
static int test_eq_int_8(int a, int b) {
uint8_t equal = constant_time_eq_int_8(a, b);
if (a == b && equal != CONSTTIME_TRUE_8) {
fprintf(stderr,
"Test failed for constant_time_eq_int_8(%d, %d): expected "
"%u(TRUE), got %u\n",
a, b, CONSTTIME_TRUE_8, equal);
return 1;
} else if (a != b && equal != CONSTTIME_FALSE_8) {
fprintf(stderr,
"Test failed for constant_time_eq_int_8(%d, %d): expected "
"%u(FALSE), got %u\n",
a, b, CONSTTIME_FALSE_8, equal);
return 1;
}
return 0;
}
static unsigned int test_values[] = {0, 1, 1024, 12345, 32000, UINT_MAX / 2 - 1,
UINT_MAX / 2, UINT_MAX / 2 + 1,
UINT_MAX - 1, UINT_MAX};
static uint8_t test_values_8[] = {0, 1, 2, 20, 32, 127, 128, 129, 255};
static int signed_test_values[] = {
0, 1, -1, 1024, -1024, 12345, -12345,
32000, -32000, INT_MAX, INT_MIN, INT_MAX - 1, INT_MIN + 1};
int main(int argc, char* argv[]) {
unsigned int a, b, i, j;
int c, d;
uint8_t e, f;
int num_failed = 0, num_all = 0;
fprintf(stdout, "Testing constant time operations...\n");
for (i = 0; i < sizeof(test_values) / sizeof(int); ++i) {
a = test_values[i];
num_failed += test_is_zero(a);
num_failed += test_is_zero_8(a);
num_all += 2;
for (j = 0; j < sizeof(test_values) / sizeof(int); ++j) {
b = test_values[j];
num_failed +=
test_binary_op(&constant_time_lt, "constant_time_lt", a, b, a < b);
num_failed += test_binary_op_8(&constant_time_lt_8, "constant_time_lt_8",
a, b, a < b);
num_failed +=
test_binary_op(&constant_time_lt, "constant_time_lt_8", b, a, b < a);
num_failed += test_binary_op_8(&constant_time_lt_8, "constant_time_lt_8",
b, a, b < a);
num_failed +=
test_binary_op(&constant_time_ge, "constant_time_ge", a, b, a >= b);
num_failed += test_binary_op_8(&constant_time_ge_8, "constant_time_ge_8",
a, b, a >= b);
num_failed +=
test_binary_op(&constant_time_ge, "constant_time_ge", b, a, b >= a);
num_failed += test_binary_op_8(&constant_time_ge_8, "constant_time_ge_8",
b, a, b >= a);
num_failed +=
test_binary_op(&constant_time_eq, "constant_time_eq", a, b, a == b);
num_failed += test_binary_op_8(&constant_time_eq_8, "constant_time_eq_8",
a, b, a == b);
num_failed +=
test_binary_op(&constant_time_eq, "constant_time_eq", b, a, b == a);
num_failed += test_binary_op_8(&constant_time_eq_8, "constant_time_eq_8",
b, a, b == a);
num_failed += test_select(a, b);
num_all += 13;
}
}
for (i = 0; i < sizeof(signed_test_values) / sizeof(int); ++i) {
c = signed_test_values[i];
for (j = 0; j < sizeof(signed_test_values) / sizeof(int); ++j) {
d = signed_test_values[j];
num_failed += test_select_int(c, d);
num_failed += test_eq_int(c, d);
num_failed += test_eq_int_8(c, d);
num_all += 3;
}
}
for (i = 0; i < sizeof(test_values_8); ++i) {
e = test_values_8[i];
for (j = 0; j < sizeof(test_values_8); ++j) {
f = test_values_8[j];
num_failed += test_select_8(e, f);
num_all += 1;
}
}
if (!num_failed) {
fprintf(stdout, "ok (ran %d tests)\n", num_all);
fprintf(stdout, "PASS\n");
return EXIT_SUCCESS;
} else {
fprintf(stdout, "%d of %d tests failed!\n", num_failed, num_all);
return EXIT_FAILURE;
}
}

61
crypto/internal.h
View File

@ -172,21 +172,45 @@ void OPENSSL_cpuid_setup(void);
* c = constant_time_select(lt, a, b); */
/* constant_time_msb returns the given value with the MSB copied to all the
* other bits. Uses the fact that arithmetic shift shifts-in the sign bit.
* However, this is not ensured by the C standard so you may need to replace
* this with something else on odd CPUs. */
* other bits. */
static inline unsigned int constant_time_msb(unsigned int a) {
return (unsigned int)((int)(a) >> (sizeof(int) * 8 - 1));
}
/* constant_time_lt returns 0xff..f if a < b and 0 otherwise. */
static inline unsigned int constant_time_lt(unsigned int a, unsigned int b) {
unsigned int lt;
/* Case 1: msb(a) == msb(b). a < b iff the MSB of a - b is set.*/
lt = ~(a ^ b) & (a - b);
/* Case 2: msb(a) != msb(b). a < b iff the MSB of b is set. */
lt |= ~a & b;
return constant_time_msb(lt);
/* Consider the two cases of the problem:
* msb(a) == msb(b): a < b iff the MSB of a - b is set.
* msb(a) != msb(b): a < b iff the MSB of b is set.
*
* If msb(a) == msb(b) then the following evaluates as:
* msb(a^((a^b)|((a-b)^a))) ==
* msb(a^((a-b) ^ a)) == (because msb(a^b) == 0)
* msb(a^a^(a-b)) == (rearranging)
* msb(a-b) (because ∀x. x^x == 0)
*
* Else, if msb(a) != msb(b) then the following evaluates as:
* msb(a^((a^b)|((a-b)^a))) ==
* msb(a^(𝟙 | ((a-b)^a))) == (because msb(a^b) == 1 and 𝟙
* represents a value s.t. msb(𝟙) = 1)
* msb(a^𝟙) == (because ORing with 1 results in 1)
* msb(b)
*
*
* Here is an SMT-LIB verification of this formula:
*
* (define-fun lt ((a (_ BitVec 32)) (b (_ BitVec 32))) (_ BitVec 32)
* (bvxor a (bvor (bvxor a b) (bvxor (bvsub a b) a)))
* )
*
* (declare-fun a () (_ BitVec 32))
* (declare-fun b () (_ BitVec 32))
*
* (assert (not (= (= #x00000001 (bvlshr (lt a b) #x0000001f)) (bvult a b))))
* (check-sat)
* (get-model)
*/
return constant_time_msb(a^((a^b)|((a-b)^a)));
}
/* constant_time_lt_8 acts like |constant_time_lt| but returns an 8-bit mask. */
@ -196,12 +220,7 @@ static inline uint8_t constant_time_lt_8(unsigned int a, unsigned int b) {
/* constant_time_gt returns 0xff..f if a >= b and 0 otherwise. */
static inline unsigned int constant_time_ge(unsigned int a, unsigned int b) {
unsigned int ge;
/* Case 1: msb(a) == msb(b). a >= b iff the MSB of a - b is not set.*/
ge = ~((a ^ b) | (a - b));
/* Case 2: msb(a) != msb(b). a >= b iff the MSB of a is set. */
ge |= a & ~b;
return constant_time_msb(ge);
return ~constant_time_lt(a, b);
}
/* constant_time_ge_8 acts like |constant_time_ge| but returns an 8-bit mask. */
@ -211,6 +230,18 @@ static inline uint8_t constant_time_ge_8(unsigned int a, unsigned int b) {
/* constant_time_is_zero returns 0xff..f if a == 0 and 0 otherwise. */
static inline unsigned int constant_time_is_zero(unsigned int a) {
/* Here is an SMT-LIB verification of this formula:
*
* (define-fun is_zero ((a (_ BitVec 32))) (_ BitVec 32)
* (bvand (bvnot a) (bvsub a #x00000001))
* )
*
* (declare-fun a () (_ BitVec 32))
*
* (assert (not (= (= #x00000001 (bvlshr (is_zero a) #x0000001f)) (= a #x00000000))))
* (check-sat)
* (get-model)
*/
return constant_time_msb(~a & (a - 1));
}

1
util/all_tests.sh
View File

@ -31,6 +31,7 @@ TESTS="
./crypto/cipher/aead_test chacha20-poly1305 $SRC/crypto/cipher/chacha20_poly1305_tests.txt
./crypto/cipher/aead_test rc4-md5 $SRC/crypto/cipher/rc4_md5_tests.txt
./crypto/cipher/cipher_test $SRC/crypto/cipher/cipher_test.txt
./crypto/constant_time_test
./crypto/dh/dh_test
./crypto/digest/digest_test
./crypto/dsa/dsa_test