diff options
author | Rich Salz <rsalz@openssl.org> | 2017-06-20 15:21:21 -0400 |
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committer | Rich Salz <rsalz@openssl.org> | 2017-06-21 09:19:42 -0400 |
commit | 9018f3ce0f9fd57e65d8e7d43741f08797811766 (patch) | |
tree | a51b119d08e3728400511572e5b09db389216c90 /include | |
parent | d2916a5b29b3ef83126cfbc7be5c16e0c3c9a521 (diff) |
Add constant-time 64
Standardize comments.
Reviewed-by: Andy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3727)
Diffstat (limited to 'include')
-rw-r--r-- | include/internal/constant_time_locl.h | 57 |
1 files changed, 35 insertions, 22 deletions
diff --git a/include/internal/constant_time_locl.h b/include/internal/constant_time_locl.h index be2730ea95..dad6d8cb99 100644 --- a/include/internal/constant_time_locl.h +++ b/include/internal/constant_time_locl.h @@ -21,17 +21,14 @@ extern "C" { * 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; - * } - * + * 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); + * unsigned int lt = constant_time_lt(a, b); + * c = constant_time_select(lt, a, b); */ /* @@ -41,35 +38,31 @@ extern "C" { * replace this with something else on odd CPUs. */ static ossl_inline unsigned int constant_time_msb(unsigned int a); +/* Convenience method for uint64_t. */ +static ossl_inline uint64_t constant_time_msb_64(uint64_t a); -/* - * Returns 0xff..f if a < b and 0 otherwise. - */ +/* Returns 0xff..f if a < b and 0 otherwise. */ static ossl_inline unsigned int constant_time_lt(unsigned int a, unsigned int b); /* Convenience method for getting an 8-bit mask. */ static ossl_inline unsigned char constant_time_lt_8(unsigned int a, unsigned int b); +/* Convenience method for uint64_t. */ +static ossl_inline uint64_t constant_time_lt_64(uint64_t a, uint64_t b); -/* - * Returns 0xff..f if a >= b and 0 otherwise. - */ +/* Returns 0xff..f if a >= b and 0 otherwise. */ static ossl_inline unsigned int constant_time_ge(unsigned int a, unsigned int b); /* Convenience method for getting an 8-bit mask. */ static ossl_inline unsigned char constant_time_ge_8(unsigned int a, unsigned int b); -/* - * Returns 0xff..f if a == 0 and 0 otherwise. - */ +/* Returns 0xff..f if a == 0 and 0 otherwise. */ static ossl_inline unsigned int constant_time_is_zero(unsigned int a); /* Convenience method for getting an 8-bit mask. */ static ossl_inline unsigned char constant_time_is_zero_8(unsigned int a); -/* - * Returns 0xff..f if a == b and 0 otherwise. - */ +/* Returns 0xff..f if a == b and 0 otherwise. */ static ossl_inline unsigned int constant_time_eq(unsigned int a, unsigned int b); /* Convenience method for getting an 8-bit mask. */ @@ -94,15 +87,24 @@ static ossl_inline unsigned int constant_time_select(unsigned int mask, static ossl_inline unsigned char constant_time_select_8(unsigned char mask, unsigned char a, unsigned char b); +/* Convenience method for uint64_t. */ +static ossl_inline uint64_t constant_time_select_64(uint64_t mask, uint64_t a, + uint64_t b); /* Convenience method for signed integers. */ static ossl_inline int constant_time_select_int(unsigned int mask, int a, int b); + static ossl_inline unsigned int constant_time_msb(unsigned int a) { return 0 - (a >> (sizeof(a) * 8 - 1)); } +static ossl_inline uint64_t constant_time_msb_64(uint64_t a) +{ + return 0 - (a >> 63); +} + static ossl_inline size_t constant_time_msb_s(size_t a) { return 0 - (a >> (sizeof(a) * 8 - 1)); @@ -125,6 +127,11 @@ static ossl_inline unsigned char constant_time_lt_8(unsigned int a, return (unsigned char)(constant_time_lt(a, b)); } +static ossl_inline uint64_t constant_time_lt_64(uint64_t a, uint64_t b) +{ + return constant_time_msb_64(a ^ ((a ^ b) | ((a - b) ^ b))); +} + static ossl_inline unsigned int constant_time_ge(unsigned int a, unsigned int b) { @@ -227,6 +234,12 @@ static ossl_inline int constant_time_select_int_s(size_t mask, int a, int b) (unsigned)(b))); } +static ossl_inline uint64_t constant_time_select_64(uint64_t mask, uint64_t a, + uint64_t b) +{ + return (mask & a) | (~mask & b); +} + #ifdef __cplusplus } #endif |