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Diffstat (limited to 'openssl/crypto/constant_time_locl.h')
| -rw-r--r-- | openssl/crypto/constant_time_locl.h | 216 |
1 files changed, 216 insertions, 0 deletions
diff --git a/openssl/crypto/constant_time_locl.h b/openssl/crypto/constant_time_locl.h new file mode 100644 index 000000000..c0483939f --- /dev/null +++ b/openssl/crypto/constant_time_locl.h @@ -0,0 +1,216 @@ +/* crypto/constant_time_locl.h */ +/* + * 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.] + */ + +#ifndef HEADER_CONSTANT_TIME_LOCL_H +#define HEADER_CONSTANT_TIME_LOCL_H + +#include "e_os.h" /* For 'inline' */ + +#ifdef __cplusplus +extern "C" { +#endif + +/* + * The boolean methods return a bitmask of all ones (0xff...f) for true + * and 0 for false. This is useful for choosing a value based on the result + * of a conditional in constant time. For example, + * + * if (a < b) { + * c = a; + * } else { + * c = b; + * } + * + * can be written as + * + * unsigned int lt = constant_time_lt(a, b); + * c = constant_time_select(lt, a, b); + */ + +/* + * 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. + */ +static inline unsigned int constant_time_msb(unsigned int a); + +/* + * Returns 0xff..f if a < b and 0 otherwise. + */ +static inline unsigned int constant_time_lt(unsigned int a, unsigned int b); +/* Convenience method for getting an 8-bit mask. */ +static inline unsigned char constant_time_lt_8(unsigned int a, unsigned int b); + +/* + * Returns 0xff..f if a >= b and 0 otherwise. + */ +static inline unsigned int constant_time_ge(unsigned int a, unsigned int b); +/* Convenience method for getting an 8-bit mask. */ +static inline unsigned char constant_time_ge_8(unsigned int a, unsigned int b); + +/* + * Returns 0xff..f if a == 0 and 0 otherwise. + */ +static inline unsigned int constant_time_is_zero(unsigned int a); +/* Convenience method for getting an 8-bit mask. */ +static inline unsigned char constant_time_is_zero_8(unsigned int a); + + +/* + * Returns 0xff..f if a == b and 0 otherwise. + */ +static inline unsigned int constant_time_eq(unsigned int a, unsigned int b); +/* Convenience method for getting an 8-bit mask. */ +static inline unsigned char constant_time_eq_8(unsigned int a, unsigned int b); +/* Signed integers. */ +static inline unsigned int constant_time_eq_int(int a, int b); +/* Convenience method for getting an 8-bit mask. */ +static inline unsigned char constant_time_eq_int_8(int a, int b); + + +/* + * Returns (mask & a) | (~mask & b). + * + * When |mask| is all 1s or all 0s (as returned by the methods above), + * the select methods return either |a| (if |mask| is nonzero) or |b| + * (if |mask| is zero). + */ +static inline unsigned int constant_time_select(unsigned int mask, + unsigned int a, unsigned int b); +/* Convenience method for unsigned chars. */ +static inline unsigned char constant_time_select_8(unsigned char mask, + unsigned char a, unsigned char b); +/* Convenience method for signed integers. */ +static inline int constant_time_select_int(unsigned int mask, int a, int b); + +static inline unsigned int constant_time_msb(unsigned int a) + { + return (unsigned int)((int)(a) >> (sizeof(int) * 8 - 1)); + } + +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); + } + +static inline unsigned char constant_time_lt_8(unsigned int a, unsigned int b) + { + return (unsigned char)(constant_time_lt(a, b)); + } + +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); + } + +static inline unsigned char constant_time_ge_8(unsigned int a, unsigned int b) + { + return (unsigned char)(constant_time_ge(a, b)); + } + +static inline unsigned int constant_time_is_zero(unsigned int a) + { + return constant_time_msb(~a & (a - 1)); + } + +static inline unsigned char constant_time_is_zero_8(unsigned int a) + { + return (unsigned char)(constant_time_is_zero(a)); + } + +static inline unsigned int constant_time_eq(unsigned int a, unsigned int b) + { + return constant_time_is_zero(a ^ b); + } + +static inline unsigned char constant_time_eq_8(unsigned int a, unsigned int b) + { + return (unsigned char)(constant_time_eq(a, b)); + } + +static inline unsigned int constant_time_eq_int(int a, int b) + { + return constant_time_eq((unsigned)(a), (unsigned)(b)); + } + +static inline unsigned char constant_time_eq_int_8(int a, int b) + { + return constant_time_eq_8((unsigned)(a), (unsigned)(b)); + } + +static inline unsigned int constant_time_select(unsigned int mask, + unsigned int a, unsigned int b) + { + return (mask & a) | (~mask & b); + } + +static inline unsigned char constant_time_select_8(unsigned char mask, + unsigned char a, unsigned char b) + { + return (unsigned char)(constant_time_select(mask, a, b)); + } + +inline int constant_time_select_int(unsigned int mask, int a, int b) + { + return (int)(constant_time_select(mask, (unsigned)(a), (unsigned)(b))); + } + +#ifdef __cplusplus +} +#endif + +#endif /* HEADER_CONSTANT_TIME_LOCL_H */ |