cobalt / cobalt / 2a8c847d785c1602f60915c8e0112e0aec6a15a5 / . / src / third_party / openssl / openssl / crypto / constant_time_locl.h

/* 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 0 - (a >> (sizeof(a) * 8 - 1)); | |

} | |

static inline unsigned int constant_time_lt(unsigned int a, unsigned int b) | |

{ | |

return constant_time_msb(a ^ ((a ^ b) | ((a - b) ^ b))); | |

} | |

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) | |

{ | |

return ~constant_time_lt(a, b); | |

} | |

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)); | |

} | |

static 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 */ |