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76 lines
1.9 KiB
C++
76 lines
1.9 KiB
C++
/*
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* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
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* Copyright (c) 2021-2022, Brian Gianforcaro <bgianf@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Types.h>
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#include <string.h>
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ALWAYS_INLINE void fast_u32_copy(u32* dest, u32 const* src, size_t count)
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{
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#if ARCH(X86_64)
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asm volatile(
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"rep movsl\n"
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: "+S"(src), "+D"(dest), "+c"(count)::"memory");
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#else
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__builtin_memcpy(dest, src, count * 4);
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#endif
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}
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ALWAYS_INLINE void fast_u32_fill(u32* dest, u32 value, size_t count)
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{
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#if ARCH(X86_64)
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asm volatile(
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"rep stosl\n"
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: "=D"(dest), "=c"(count)
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: "D"(dest), "c"(count), "a"(value)
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: "memory");
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#else
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for (auto* p = dest; p < (dest + count); ++p) {
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*p = value;
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}
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#endif
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}
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namespace AK {
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inline void secure_zero(void* ptr, size_t size)
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{
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__builtin_memset(ptr, 0, size);
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// The memory barrier is here to avoid the compiler optimizing
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// away the memset when we rely on it for wiping secrets.
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asm volatile("" ::
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: "memory");
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}
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// Naive implementation of a constant time buffer comparison function.
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// The goal being to not use any conditional branching so calls are
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// guarded against potential timing attacks.
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//
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// See OpenBSD's timingsafe_memcmp for more advanced implementations.
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inline bool timing_safe_compare(void const* b1, void const* b2, size_t len)
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{
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auto* c1 = static_cast<char const*>(b1);
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auto* c2 = static_cast<char const*>(b2);
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u8 res = 0;
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for (size_t i = 0; i < len; i++) {
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res |= c1[i] ^ c2[i];
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}
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// FIXME: !res can potentially inject branches depending
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// on which toolchain is being used for compilation. Ideally
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// we would use a more advanced algorithm.
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return !res;
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}
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}
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#if USING_AK_GLOBALLY
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using AK::secure_zero;
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using AK::timing_safe_compare;
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#endif
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