diff options
Diffstat (limited to 'thirdparty/mbedtls/library/constant_time_impl.h')
| -rw-r--r-- | thirdparty/mbedtls/library/constant_time_impl.h | 556 |
1 files changed, 556 insertions, 0 deletions
diff --git a/thirdparty/mbedtls/library/constant_time_impl.h b/thirdparty/mbedtls/library/constant_time_impl.h new file mode 100644 index 0000000000..2a4574ba68 --- /dev/null +++ b/thirdparty/mbedtls/library/constant_time_impl.h @@ -0,0 +1,556 @@ +/** + * Constant-time functions + * + * Copyright The Mbed TLS Contributors + * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later + */ + +#ifndef MBEDTLS_CONSTANT_TIME_IMPL_H +#define MBEDTLS_CONSTANT_TIME_IMPL_H + +#include <stddef.h> + +#include "common.h" + +#if defined(MBEDTLS_BIGNUM_C) +#include "mbedtls/bignum.h" +#endif + +/* + * To improve readability of constant_time_internal.h, the static inline + * definitions are here, and constant_time_internal.h has only the declarations. + * + * This results in duplicate declarations of the form: + * static inline void f(); // from constant_time_internal.h + * static inline void f() { ... } // from constant_time_impl.h + * when constant_time_internal.h is included. + * + * This appears to behave as if the declaration-without-definition was not present + * (except for warnings if gcc -Wredundant-decls or similar is used). + * + * Disable -Wredundant-decls so that gcc does not warn about this. This is re-enabled + * at the bottom of this file. + */ +#if defined(MBEDTLS_COMPILER_IS_GCC) && (__GNUC__ > 4) + #pragma GCC diagnostic push + #pragma GCC diagnostic ignored "-Wredundant-decls" +#endif + +/* Disable asm under Memsan because it confuses Memsan and generates false errors. + * + * We also disable under Valgrind by default, because it's more useful + * for Valgrind to test the plain C implementation. MBEDTLS_TEST_CONSTANT_FLOW_ASM //no-check-names + * may be set to permit building asm under Valgrind. + */ +#if defined(MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN) || \ + (defined(MBEDTLS_TEST_CONSTANT_FLOW_VALGRIND) && !defined(MBEDTLS_TEST_CONSTANT_FLOW_ASM)) //no-check-names +#define MBEDTLS_CT_NO_ASM +#elif defined(__has_feature) +#if __has_feature(memory_sanitizer) +#define MBEDTLS_CT_NO_ASM +#endif +#endif + +/* armcc5 --gnu defines __GNUC__ but doesn't support GNU's extended asm */ +#if defined(MBEDTLS_HAVE_ASM) && defined(__GNUC__) && (!defined(__ARMCC_VERSION) || \ + __ARMCC_VERSION >= 6000000) && !defined(MBEDTLS_CT_NO_ASM) +#define MBEDTLS_CT_ASM +#if (defined(__arm__) || defined(__thumb__) || defined(__thumb2__)) +#define MBEDTLS_CT_ARM_ASM +#elif defined(__aarch64__) +#define MBEDTLS_CT_AARCH64_ASM +#elif defined(__amd64__) || defined(__x86_64__) +#define MBEDTLS_CT_X86_64_ASM +#elif defined(__i386__) +#define MBEDTLS_CT_X86_ASM +#endif +#endif + +#define MBEDTLS_CT_SIZE (sizeof(mbedtls_ct_uint_t) * 8) + + +/* ============================================================================ + * Core const-time primitives + */ + +/* Ensure that the compiler cannot know the value of x (i.e., cannot optimise + * based on its value) after this function is called. + * + * If we are not using assembly, this will be fairly inefficient, so its use + * should be minimised. + */ + +#if !defined(MBEDTLS_CT_ASM) +extern volatile mbedtls_ct_uint_t mbedtls_ct_zero; +#endif + +/** + * \brief Ensure that a value cannot be known at compile time. + * + * \param x The value to hide from the compiler. + * \return The same value that was passed in, such that the compiler + * cannot prove its value (even for calls of the form + * x = mbedtls_ct_compiler_opaque(1), x will be unknown). + * + * \note This is mainly used in constructing mbedtls_ct_condition_t + * values and performing operations over them, to ensure that + * there is no way for the compiler to ever know anything about + * the value of an mbedtls_ct_condition_t. + */ +static inline mbedtls_ct_uint_t mbedtls_ct_compiler_opaque(mbedtls_ct_uint_t x) +{ +#if defined(MBEDTLS_CT_ASM) + asm volatile ("" : [x] "+r" (x) :); + return x; +#else + return x ^ mbedtls_ct_zero; +#endif +} + +/* + * Selecting unified syntax is needed for gcc, and harmless on clang. + * + * This is needed because on Thumb 1, condition flags are always set, so + * e.g. "negs" is supported but "neg" is not (on Thumb 2, both exist). + * + * Under Thumb 1 unified syntax, only the "negs" form is accepted, and + * under divided syntax, only the "neg" form is accepted. clang only + * supports unified syntax. + * + * On Thumb 2 and Arm, both compilers are happy with the "s" suffix, + * although we don't actually care about setting the flags. + * + * For old versions of gcc (see #8516 for details), restore divided + * syntax afterwards - otherwise old versions of gcc seem to apply + * unified syntax globally, which breaks other asm code. + */ +#if defined(MBEDTLS_COMPILER_IS_GCC) && defined(__thumb__) && !defined(__thumb2__) && \ + (__GNUC__ < 11) && !defined(__ARM_ARCH_2__) +#define RESTORE_ASM_SYNTAX ".syntax divided \n\t" +#else +#define RESTORE_ASM_SYNTAX +#endif + +/* Convert a number into a condition in constant time. */ +static inline mbedtls_ct_condition_t mbedtls_ct_bool(mbedtls_ct_uint_t x) +{ + /* + * Define mask-generation code that, as far as possible, will not use branches or conditional instructions. + * + * For some platforms / type sizes, we define assembly to assure this. + * + * Otherwise, we define a plain C fallback which (in May 2023) does not get optimised into + * conditional instructions or branches by trunk clang, gcc, or MSVC v19. + */ +#if defined(MBEDTLS_CT_AARCH64_ASM) && (defined(MBEDTLS_CT_SIZE_32) || defined(MBEDTLS_CT_SIZE_64)) + mbedtls_ct_uint_t s; + asm volatile ("neg %x[s], %x[x] \n\t" + "orr %x[x], %x[s], %x[x] \n\t" + "asr %x[x], %x[x], 63 \n\t" + : + [s] "=&r" (s), + [x] "+&r" (x) + : + : + ); + return (mbedtls_ct_condition_t) x; +#elif defined(MBEDTLS_CT_ARM_ASM) && defined(MBEDTLS_CT_SIZE_32) + uint32_t s; + asm volatile (".syntax unified \n\t" + "negs %[s], %[x] \n\t" + "orrs %[x], %[x], %[s] \n\t" + "asrs %[x], %[x], #31 \n\t" + RESTORE_ASM_SYNTAX + : + [s] "=&l" (s), + [x] "+&l" (x) + : + : + "cc" /* clobbers flag bits */ + ); + return (mbedtls_ct_condition_t) x; +#elif defined(MBEDTLS_CT_X86_64_ASM) && (defined(MBEDTLS_CT_SIZE_32) || defined(MBEDTLS_CT_SIZE_64)) + uint64_t s; + asm volatile ("mov %[x], %[s] \n\t" + "neg %[s] \n\t" + "or %[x], %[s] \n\t" + "sar $63, %[s] \n\t" + : + [s] "=&a" (s) + : + [x] "D" (x) + : + ); + return (mbedtls_ct_condition_t) s; +#elif defined(MBEDTLS_CT_X86_ASM) && defined(MBEDTLS_CT_SIZE_32) + uint32_t s; + asm volatile ("mov %[x], %[s] \n\t" + "neg %[s] \n\t" + "or %[s], %[x] \n\t" + "sar $31, %[x] \n\t" + : + [s] "=&c" (s), + [x] "+&a" (x) + : + : + ); + return (mbedtls_ct_condition_t) x; +#else + const mbedtls_ct_uint_t xo = mbedtls_ct_compiler_opaque(x); +#if defined(_MSC_VER) + /* MSVC has a warning about unary minus on unsigned, but this is + * well-defined and precisely what we want to do here */ +#pragma warning( push ) +#pragma warning( disable : 4146 ) +#endif + // y is negative (i.e., top bit set) iff x is non-zero + mbedtls_ct_int_t y = (-xo) | -(xo >> 1); + + // extract only the sign bit of y so that y == 1 (if x is non-zero) or 0 (if x is zero) + y = (((mbedtls_ct_uint_t) y) >> (MBEDTLS_CT_SIZE - 1)); + + // -y has all bits set (if x is non-zero), or all bits clear (if x is zero) + return (mbedtls_ct_condition_t) (-y); +#if defined(_MSC_VER) +#pragma warning( pop ) +#endif +#endif +} + +static inline mbedtls_ct_uint_t mbedtls_ct_if(mbedtls_ct_condition_t condition, + mbedtls_ct_uint_t if1, + mbedtls_ct_uint_t if0) +{ +#if defined(MBEDTLS_CT_AARCH64_ASM) && (defined(MBEDTLS_CT_SIZE_32) || defined(MBEDTLS_CT_SIZE_64)) + asm volatile ("and %x[if1], %x[if1], %x[condition] \n\t" + "mvn %x[condition], %x[condition] \n\t" + "and %x[condition], %x[condition], %x[if0] \n\t" + "orr %x[condition], %x[if1], %x[condition]" + : + [condition] "+&r" (condition), + [if1] "+&r" (if1) + : + [if0] "r" (if0) + : + ); + return (mbedtls_ct_uint_t) condition; +#elif defined(MBEDTLS_CT_ARM_ASM) && defined(MBEDTLS_CT_SIZE_32) + asm volatile (".syntax unified \n\t" + "ands %[if1], %[if1], %[condition] \n\t" + "mvns %[condition], %[condition] \n\t" + "ands %[condition], %[condition], %[if0] \n\t" + "orrs %[condition], %[if1], %[condition] \n\t" + RESTORE_ASM_SYNTAX + : + [condition] "+&l" (condition), + [if1] "+&l" (if1) + : + [if0] "l" (if0) + : + "cc" + ); + return (mbedtls_ct_uint_t) condition; +#elif defined(MBEDTLS_CT_X86_64_ASM) && (defined(MBEDTLS_CT_SIZE_32) || defined(MBEDTLS_CT_SIZE_64)) + asm volatile ("and %[condition], %[if1] \n\t" + "not %[condition] \n\t" + "and %[condition], %[if0] \n\t" + "or %[if1], %[if0] \n\t" + : + [condition] "+&D" (condition), + [if1] "+&S" (if1), + [if0] "+&a" (if0) + : + : + ); + return if0; +#elif defined(MBEDTLS_CT_X86_ASM) && defined(MBEDTLS_CT_SIZE_32) + asm volatile ("and %[condition], %[if1] \n\t" + "not %[condition] \n\t" + "and %[if0], %[condition] \n\t" + "or %[condition], %[if1] \n\t" + : + [condition] "+&c" (condition), + [if1] "+&a" (if1) + : + [if0] "b" (if0) + : + ); + return if1; +#else + mbedtls_ct_condition_t not_cond = + (mbedtls_ct_condition_t) (~mbedtls_ct_compiler_opaque(condition)); + return (mbedtls_ct_uint_t) ((condition & if1) | (not_cond & if0)); +#endif +} + +static inline mbedtls_ct_condition_t mbedtls_ct_uint_lt(mbedtls_ct_uint_t x, mbedtls_ct_uint_t y) +{ +#if defined(MBEDTLS_CT_AARCH64_ASM) && (defined(MBEDTLS_CT_SIZE_32) || defined(MBEDTLS_CT_SIZE_64)) + uint64_t s1; + asm volatile ("eor %x[s1], %x[y], %x[x] \n\t" + "sub %x[x], %x[x], %x[y] \n\t" + "bic %x[x], %x[x], %x[s1] \n\t" + "and %x[s1], %x[s1], %x[y] \n\t" + "orr %x[s1], %x[x], %x[s1] \n\t" + "asr %x[x], %x[s1], 63" + : + [s1] "=&r" (s1), + [x] "+&r" (x) + : + [y] "r" (y) + : + ); + return (mbedtls_ct_condition_t) x; +#elif defined(MBEDTLS_CT_ARM_ASM) && defined(MBEDTLS_CT_SIZE_32) + uint32_t s1; + asm volatile ( + ".syntax unified \n\t" +#if defined(__thumb__) && !defined(__thumb2__) + "movs %[s1], %[x] \n\t" + "eors %[s1], %[s1], %[y] \n\t" +#else + "eors %[s1], %[x], %[y] \n\t" +#endif + "subs %[x], %[x], %[y] \n\t" + "bics %[x], %[x], %[s1] \n\t" + "ands %[y], %[s1], %[y] \n\t" + "orrs %[x], %[x], %[y] \n\t" + "asrs %[x], %[x], #31 \n\t" + RESTORE_ASM_SYNTAX + : + [s1] "=&l" (s1), + [x] "+&l" (x), + [y] "+&l" (y) + : + : + "cc" + ); + return (mbedtls_ct_condition_t) x; +#elif defined(MBEDTLS_CT_X86_64_ASM) && (defined(MBEDTLS_CT_SIZE_32) || defined(MBEDTLS_CT_SIZE_64)) + uint64_t s; + asm volatile ("mov %[x], %[s] \n\t" + "xor %[y], %[s] \n\t" + "sub %[y], %[x] \n\t" + "and %[s], %[y] \n\t" + "not %[s] \n\t" + "and %[s], %[x] \n\t" + "or %[y], %[x] \n\t" + "sar $63, %[x] \n\t" + : + [s] "=&a" (s), + [x] "+&D" (x), + [y] "+&S" (y) + : + : + ); + return (mbedtls_ct_condition_t) x; +#elif defined(MBEDTLS_CT_X86_ASM) && defined(MBEDTLS_CT_SIZE_32) + uint32_t s; + asm volatile ("mov %[x], %[s] \n\t" + "xor %[y], %[s] \n\t" + "sub %[y], %[x] \n\t" + "and %[s], %[y] \n\t" + "not %[s] \n\t" + "and %[s], %[x] \n\t" + "or %[y], %[x] \n\t" + "sar $31, %[x] \n\t" + : + [s] "=&b" (s), + [x] "+&a" (x), + [y] "+&c" (y) + : + : + ); + return (mbedtls_ct_condition_t) x; +#else + /* Ensure that the compiler cannot optimise the following operations over x and y, + * even if it knows the value of x and y. + */ + const mbedtls_ct_uint_t xo = mbedtls_ct_compiler_opaque(x); + const mbedtls_ct_uint_t yo = mbedtls_ct_compiler_opaque(y); + /* + * Check if the most significant bits (MSB) of the operands are different. + * cond is true iff the MSBs differ. + */ + mbedtls_ct_condition_t cond = mbedtls_ct_bool((xo ^ yo) >> (MBEDTLS_CT_SIZE - 1)); + + /* + * If the MSB are the same then the difference x-y will be negative (and + * have its MSB set to 1 during conversion to unsigned) if and only if x<y. + * + * If the MSB are different, then the operand with the MSB of 1 is the + * bigger. (That is if y has MSB of 1, then x<y is true and it is false if + * the MSB of y is 0.) + */ + + // Select either y, or x - y + mbedtls_ct_uint_t ret = mbedtls_ct_if(cond, yo, (mbedtls_ct_uint_t) (xo - yo)); + + // Extract only the MSB of ret + ret = ret >> (MBEDTLS_CT_SIZE - 1); + + // Convert to a condition (i.e., all bits set iff non-zero) + return mbedtls_ct_bool(ret); +#endif +} + +static inline mbedtls_ct_condition_t mbedtls_ct_uint_ne(mbedtls_ct_uint_t x, mbedtls_ct_uint_t y) +{ + /* diff = 0 if x == y, non-zero otherwise */ + const mbedtls_ct_uint_t diff = mbedtls_ct_compiler_opaque(x) ^ mbedtls_ct_compiler_opaque(y); + + /* all ones if x != y, 0 otherwise */ + return mbedtls_ct_bool(diff); +} + +static inline unsigned char mbedtls_ct_uchar_in_range_if(unsigned char low, + unsigned char high, + unsigned char c, + unsigned char t) +{ + const unsigned char co = (unsigned char) mbedtls_ct_compiler_opaque(c); + const unsigned char to = (unsigned char) mbedtls_ct_compiler_opaque(t); + + /* low_mask is: 0 if low <= c, 0x...ff if low > c */ + unsigned low_mask = ((unsigned) co - low) >> 8; + /* high_mask is: 0 if c <= high, 0x...ff if c > high */ + unsigned high_mask = ((unsigned) high - co) >> 8; + + return (unsigned char) (~(low_mask | high_mask)) & to; +} + +/* ============================================================================ + * Everything below here is trivial wrapper functions + */ + +static inline size_t mbedtls_ct_size_if(mbedtls_ct_condition_t condition, + size_t if1, + size_t if0) +{ + return (size_t) mbedtls_ct_if(condition, (mbedtls_ct_uint_t) if1, (mbedtls_ct_uint_t) if0); +} + +static inline unsigned mbedtls_ct_uint_if(mbedtls_ct_condition_t condition, + unsigned if1, + unsigned if0) +{ + return (unsigned) mbedtls_ct_if(condition, (mbedtls_ct_uint_t) if1, (mbedtls_ct_uint_t) if0); +} + +static inline mbedtls_ct_condition_t mbedtls_ct_bool_if(mbedtls_ct_condition_t condition, + mbedtls_ct_condition_t if1, + mbedtls_ct_condition_t if0) +{ + return (mbedtls_ct_condition_t) mbedtls_ct_if(condition, (mbedtls_ct_uint_t) if1, + (mbedtls_ct_uint_t) if0); +} + +#if defined(MBEDTLS_BIGNUM_C) + +static inline mbedtls_mpi_uint mbedtls_ct_mpi_uint_if(mbedtls_ct_condition_t condition, + mbedtls_mpi_uint if1, + mbedtls_mpi_uint if0) +{ + return (mbedtls_mpi_uint) mbedtls_ct_if(condition, + (mbedtls_ct_uint_t) if1, + (mbedtls_ct_uint_t) if0); +} + +#endif + +static inline size_t mbedtls_ct_size_if_else_0(mbedtls_ct_condition_t condition, size_t if1) +{ + return (size_t) (condition & if1); +} + +static inline unsigned mbedtls_ct_uint_if_else_0(mbedtls_ct_condition_t condition, unsigned if1) +{ + return (unsigned) (condition & if1); +} + +static inline mbedtls_ct_condition_t mbedtls_ct_bool_if_else_0(mbedtls_ct_condition_t condition, + mbedtls_ct_condition_t if1) +{ + return (mbedtls_ct_condition_t) (condition & if1); +} + +#if defined(MBEDTLS_BIGNUM_C) + +static inline mbedtls_mpi_uint mbedtls_ct_mpi_uint_if_else_0(mbedtls_ct_condition_t condition, + mbedtls_mpi_uint if1) +{ + return (mbedtls_mpi_uint) (condition & if1); +} + +#endif /* MBEDTLS_BIGNUM_C */ + +static inline int mbedtls_ct_error_if(mbedtls_ct_condition_t condition, int if1, int if0) +{ + /* Coverting int -> uint -> int here is safe, because we require if1 and if0 to be + * in the range -32767..0, and we require 32-bit int and uint types. + * + * This means that (0 <= -if0 < INT_MAX), so negating if0 is safe, and similarly for + * converting back to int. + */ + return -((int) mbedtls_ct_if(condition, (mbedtls_ct_uint_t) (-if1), + (mbedtls_ct_uint_t) (-if0))); +} + +static inline int mbedtls_ct_error_if_else_0(mbedtls_ct_condition_t condition, int if1) +{ + return -((int) (condition & (-if1))); +} + +static inline mbedtls_ct_condition_t mbedtls_ct_uint_eq(mbedtls_ct_uint_t x, + mbedtls_ct_uint_t y) +{ + return ~mbedtls_ct_uint_ne(x, y); +} + +static inline mbedtls_ct_condition_t mbedtls_ct_uint_gt(mbedtls_ct_uint_t x, + mbedtls_ct_uint_t y) +{ + return mbedtls_ct_uint_lt(y, x); +} + +static inline mbedtls_ct_condition_t mbedtls_ct_uint_ge(mbedtls_ct_uint_t x, + mbedtls_ct_uint_t y) +{ + return ~mbedtls_ct_uint_lt(x, y); +} + +static inline mbedtls_ct_condition_t mbedtls_ct_uint_le(mbedtls_ct_uint_t x, + mbedtls_ct_uint_t y) +{ + return ~mbedtls_ct_uint_gt(x, y); +} + +static inline mbedtls_ct_condition_t mbedtls_ct_bool_ne(mbedtls_ct_condition_t x, + mbedtls_ct_condition_t y) +{ + return (mbedtls_ct_condition_t) (x ^ y); +} + +static inline mbedtls_ct_condition_t mbedtls_ct_bool_and(mbedtls_ct_condition_t x, + mbedtls_ct_condition_t y) +{ + return (mbedtls_ct_condition_t) (x & y); +} + +static inline mbedtls_ct_condition_t mbedtls_ct_bool_or(mbedtls_ct_condition_t x, + mbedtls_ct_condition_t y) +{ + return (mbedtls_ct_condition_t) (x | y); +} + +static inline mbedtls_ct_condition_t mbedtls_ct_bool_not(mbedtls_ct_condition_t x) +{ + return (mbedtls_ct_condition_t) (~x); +} + +#if defined(MBEDTLS_COMPILER_IS_GCC) && (__GNUC__ > 4) +/* Restore warnings for -Wredundant-decls on gcc */ + #pragma GCC diagnostic pop +#endif + +#endif /* MBEDTLS_CONSTANT_TIME_IMPL_H */ |