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Diffstat (limited to 'thirdparty/internal/constant_time.h')
| -rw-r--r-- | thirdparty/internal/constant_time.h | 421 |
1 files changed, 421 insertions, 0 deletions
diff --git a/thirdparty/internal/constant_time.h b/thirdparty/internal/constant_time.h new file mode 100644 index 00000000..0ed6f823 --- /dev/null +++ b/thirdparty/internal/constant_time.h @@ -0,0 +1,421 @@ +/* + * Copyright 2014-2021 The OpenSSL Project Authors. All Rights Reserved. + * + * Licensed under the Apache License 2.0 (the "License"). You may not use + * this file except in compliance with the License. You can obtain a copy + * in the file LICENSE in the source distribution or at + * https://www.openssl.org/source/license.html + */ + +#ifndef OSSL_INTERNAL_CONSTANT_TIME_H +# define OSSL_INTERNAL_CONSTANT_TIME_H +# pragma once + +# include <stdlib.h> +# include <string.h> +# include <openssl/e_os2.h> /* For 'ossl_inline' */ + +/*- + * 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. */ +static ossl_inline unsigned int constant_time_msb(unsigned int a); +/* Convenience method for uint32_t. */ +static ossl_inline uint32_t constant_time_msb_32(uint32_t 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. */ +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. */ +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. */ +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); +/* Convenience method for getting a 32-bit mask. */ +static ossl_inline uint32_t constant_time_is_zero_32(uint32_t a); + +/* 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. */ +static ossl_inline unsigned char constant_time_eq_8(unsigned int a, + unsigned int b); +/* Signed integers. */ +static ossl_inline unsigned int constant_time_eq_int(int a, int b); +/* Convenience method for getting an 8-bit mask. */ +static ossl_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 ossl_inline unsigned int constant_time_select(unsigned int mask, + unsigned int a, + unsigned int b); +/* Convenience method for unsigned chars. */ +static ossl_inline unsigned char constant_time_select_8(unsigned char mask, + unsigned char a, + unsigned char b); + +/* Convenience method for uint32_t. */ +static ossl_inline uint32_t constant_time_select_32(uint32_t mask, uint32_t a, + uint32_t 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 uint32_t constant_time_msb_32(uint32_t a) +{ + return 0 - (a >> 31); +} + +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)); +} + +static ossl_inline unsigned int constant_time_lt(unsigned int a, + unsigned int b) +{ + return constant_time_msb(a ^ ((a ^ b) | ((a - b) ^ b))); +} + +static ossl_inline size_t constant_time_lt_s(size_t a, size_t b) +{ + return constant_time_msb_s(a ^ ((a ^ b) | ((a - b) ^ b))); +} + +static ossl_inline unsigned char constant_time_lt_8(unsigned int a, + unsigned int b) +{ + 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) +{ + return ~constant_time_lt(a, b); +} + +static ossl_inline size_t constant_time_ge_s(size_t a, size_t b) +{ + return ~constant_time_lt_s(a, b); +} + +static ossl_inline unsigned char constant_time_ge_8(unsigned int a, + unsigned int b) +{ + return (unsigned char)constant_time_ge(a, b); +} + +static ossl_inline unsigned char constant_time_ge_8_s(size_t a, size_t b) +{ + return (unsigned char)constant_time_ge_s(a, b); +} + +static ossl_inline unsigned int constant_time_is_zero(unsigned int a) +{ + return constant_time_msb(~a & (a - 1)); +} + +static ossl_inline size_t constant_time_is_zero_s(size_t a) +{ + return constant_time_msb_s(~a & (a - 1)); +} + +static ossl_inline unsigned char constant_time_is_zero_8(unsigned int a) +{ + return (unsigned char)constant_time_is_zero(a); +} + +static ossl_inline uint32_t constant_time_is_zero_32(uint32_t a) +{ + return constant_time_msb_32(~a & (a - 1)); +} + +static ossl_inline uint64_t constant_time_is_zero_64(uint64_t a) +{ + return constant_time_msb_64(~a & (a - 1)); +} + +static ossl_inline unsigned int constant_time_eq(unsigned int a, + unsigned int b) +{ + return constant_time_is_zero(a ^ b); +} + +static ossl_inline size_t constant_time_eq_s(size_t a, size_t b) +{ + return constant_time_is_zero_s(a ^ b); +} + +static ossl_inline unsigned char constant_time_eq_8(unsigned int a, + unsigned int b) +{ + return (unsigned char)constant_time_eq(a, b); +} + +static ossl_inline unsigned char constant_time_eq_8_s(size_t a, size_t b) +{ + return (unsigned char)constant_time_eq_s(a, b); +} + +static ossl_inline unsigned int constant_time_eq_int(int a, int b) +{ + return constant_time_eq((unsigned)(a), (unsigned)(b)); +} + +static ossl_inline unsigned char constant_time_eq_int_8(int a, int b) +{ + return constant_time_eq_8((unsigned)(a), (unsigned)(b)); +} + +/* + * Returns the value unmodified, but avoids optimizations. + * The barriers prevent the compiler from narrowing down the + * possible value range of the mask and ~mask in the select + * statements, which avoids the recognition of the select + * and turning it into a conditional load or branch. + */ +static ossl_inline unsigned int value_barrier(unsigned int a) +{ +#if !defined(OPENSSL_NO_ASM) && defined(__GNUC__) + unsigned int r; + __asm__("" : "=r"(r) : "0"(a)); +#else + volatile unsigned int r = a; +#endif + return r; +} + +/* Convenience method for uint32_t. */ +static ossl_inline uint32_t value_barrier_32(uint32_t a) +{ +#if !defined(OPENSSL_NO_ASM) && defined(__GNUC__) + uint32_t r; + __asm__("" : "=r"(r) : "0"(a)); +#else + volatile uint32_t r = a; +#endif + return r; +} + +/* Convenience method for uint64_t. */ +static ossl_inline uint64_t value_barrier_64(uint64_t a) +{ +#if !defined(OPENSSL_NO_ASM) && defined(__GNUC__) + uint64_t r; + __asm__("" : "=r"(r) : "0"(a)); +#else + volatile uint64_t r = a; +#endif + return r; +} + +/* Convenience method for size_t. */ +static ossl_inline size_t value_barrier_s(size_t a) +{ +#if !defined(OPENSSL_NO_ASM) && defined(__GNUC__) + size_t r; + __asm__("" : "=r"(r) : "0"(a)); +#else + volatile size_t r = a; +#endif + return r; +} + +static ossl_inline unsigned int constant_time_select(unsigned int mask, + unsigned int a, + unsigned int b) +{ + return (value_barrier(mask) & a) | (value_barrier(~mask) & b); +} + +static ossl_inline size_t constant_time_select_s(size_t mask, + size_t a, + size_t b) +{ + return (value_barrier_s(mask) & a) | (value_barrier_s(~mask) & b); +} + +static ossl_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 ossl_inline int constant_time_select_int(unsigned int mask, int a, + int b) +{ + return (int)constant_time_select(mask, (unsigned)(a), (unsigned)(b)); +} + +static ossl_inline int constant_time_select_int_s(size_t mask, int a, int b) +{ + return (int)constant_time_select((unsigned)mask, (unsigned)(a), + (unsigned)(b)); +} + +static ossl_inline uint32_t constant_time_select_32(uint32_t mask, uint32_t a, + uint32_t b) +{ + return (value_barrier_32(mask) & a) | (value_barrier_32(~mask) & b); +} + +static ossl_inline uint64_t constant_time_select_64(uint64_t mask, uint64_t a, + uint64_t b) +{ + return (value_barrier_64(mask) & a) | (value_barrier_64(~mask) & b); +} + +/* + * mask must be 0xFFFFFFFF or 0x00000000. + * + * if (mask) { + * uint32_t tmp = *a; + * + * *a = *b; + * *b = tmp; + * } + */ +static ossl_inline void constant_time_cond_swap_32(uint32_t mask, uint32_t *a, + uint32_t *b) +{ + uint32_t xor = *a ^ *b; + + xor &= mask; + *a ^= xor; + *b ^= xor; +} + +/* + * mask must be 0xFFFFFFFF or 0x00000000. + * + * if (mask) { + * uint64_t tmp = *a; + * + * *a = *b; + * *b = tmp; + * } + */ +static ossl_inline void constant_time_cond_swap_64(uint64_t mask, uint64_t *a, + uint64_t *b) +{ + uint64_t xor = *a ^ *b; + + xor &= mask; + *a ^= xor; + *b ^= xor; +} + +/* + * mask must be 0xFF or 0x00. + * "constant time" is per len. + * + * if (mask) { + * unsigned char tmp[len]; + * + * memcpy(tmp, a, len); + * memcpy(a, b); + * memcpy(b, tmp); + * } + */ +static ossl_inline void constant_time_cond_swap_buff(unsigned char mask, + unsigned char *a, + unsigned char *b, + size_t len) +{ + size_t i; + unsigned char tmp; + + for (i = 0; i < len; i++) { + tmp = a[i] ^ b[i]; + tmp &= mask; + a[i] ^= tmp; + b[i] ^= tmp; + } +} + +/* + * table is a two dimensional array of bytes. Each row has rowsize elements. + * Copies row number idx into out. rowsize and numrows are not considered + * private. + */ +static ossl_inline void constant_time_lookup(void *out, + const void *table, + size_t rowsize, + size_t numrows, + size_t idx) +{ + size_t i, j; + const unsigned char *tablec = (const unsigned char *)table; + unsigned char *outc = (unsigned char *)out; + unsigned char mask; + + memset(out, 0, rowsize); + + /* Note idx may underflow - but that is well defined */ + for (i = 0; i < numrows; i++, idx--) { + mask = (unsigned char)constant_time_is_zero_s(idx); + for (j = 0; j < rowsize; j++) + *(outc + j) |= constant_time_select_8(mask, *(tablec++), 0); + } +} + +/* + * Expected usage pattern is to unconditionally set error and then + * wipe it if there was no actual error. |clear| is 1 or 0. + */ +void err_clear_last_constant_time(int clear); + +#endif /* OSSL_INTERNAL_CONSTANT_TIME_H */ |