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Partially implements #74. Securely erases keys from memory after they are no longer needed. Might have a performance impact, which I haven't measured (perf measurements aren't generally reliable on laptops). Thanks to @stoffu for the suggestion to specialize the pod_to_hex/hex_to_pod functions. Using overloads + SFINAE instead generalizes it so other types can be marked as scrubbed without adding more boilerplate.
131 lines
5.2 KiB
C++
131 lines
5.2 KiB
C++
// Copyright (c) 2017, The Monero Project
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//
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without modification, are
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// permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice, this list of
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// conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright notice, this list
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// of conditions and the following disclaimer in the documentation and/or other
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// materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its contributors may be
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// used to endorse or promote products derived from this software without specific
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// prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#pragma once
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#include <cstdint>
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#include <memory>
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#include <type_traits>
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namespace epee
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{
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/*!
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\brief Non-owning sequence of data. Does not deep copy
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Inspired by `gsl::span` and/or `boost::iterator_range`. This class is
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intended to be used as a parameter type for functions that need to take a
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writable or read-only sequence of data. Most common cases are `span<char>`
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and `span<std::uint8_t>`. Using as a class member is only recommended if
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clearly documented as not doing a deep-copy. C-arrays are easily convertible
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to this type.
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\note Conversion from C string literal to `span<const char>` will include
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the NULL-terminator.
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\note Never allows derived-to-base pointer conversion; an array of derived
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types is not an array of base types.
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*/
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template<typename T>
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class span
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{
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/* Supporting class types is tricky - the {ptr,len} constructor will allow
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derived-to-base conversions. This is NOT desireable because an array of
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derived types is not an array of base types. It is possible to handle
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this case, implement when/if needed. */
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static_assert(!std::is_class<T>(), "no class types are currently allowed");
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public:
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using value_type = T;
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using size_type = std::size_t;
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using difference_type = std::ptrdiff_t;
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using pointer = T*;
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using const_pointer = const T*;
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using reference = T&;
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using const_reference = const T&;
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using iterator = pointer;
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using const_iterator = const_pointer;
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constexpr span() noexcept : ptr(nullptr), len(0) {}
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constexpr span(std::nullptr_t) noexcept : span() {}
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constexpr span(T* const src_ptr, const std::size_t count) noexcept
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: ptr(src_ptr), len(count) {}
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//! Conversion from C-array. Prevents common bugs with sizeof + arrays.
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template<std::size_t N>
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constexpr span(T (&src)[N]) noexcept : span(src, N) {}
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constexpr span(const span&) noexcept = default;
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span& operator=(const span&) noexcept = default;
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constexpr iterator begin() const noexcept { return ptr; }
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constexpr const_iterator cbegin() const noexcept { return ptr; }
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constexpr iterator end() const noexcept { return begin() + size(); }
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constexpr const_iterator cend() const noexcept { return cbegin() + size(); }
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constexpr bool empty() const noexcept { return size() == 0; }
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constexpr pointer data() const noexcept { return ptr; }
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constexpr std::size_t size() const noexcept { return len; }
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constexpr std::size_t size_bytes() const noexcept { return size() * sizeof(value_type); }
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private:
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T* ptr;
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std::size_t len;
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};
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//! \return `span<const T::value_type>` from a STL compatible `src`.
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template<typename T>
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constexpr span<const typename T::value_type> to_span(const T& src)
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{
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// compiler provides diagnostic if size() is not size_t.
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return {src.data(), src.size()};
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}
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template<typename T>
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constexpr bool has_padding() noexcept
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{
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return !std::is_pod<T>::value || alignof(T) != 1;
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}
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//! \return Cast data from `src` as `span<const std::uint8_t>`.
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template<typename T>
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span<const std::uint8_t> to_byte_span(const span<const T> src) noexcept
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{
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static_assert(!has_padding<T>(), "source type may have padding");
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return {reinterpret_cast<const std::uint8_t*>(src.data()), src.size_bytes()};
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}
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//! \return `span<const std::uint8_t>` which represents the bytes at `&src`.
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template<typename T>
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span<const std::uint8_t> as_byte_span(const T& src) noexcept
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{
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static_assert(!std::is_empty<T>(), "empty types will not work -> sizeof == 1");
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static_assert(!has_padding<T>(), "source type may have padding");
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return {reinterpret_cast<const std::uint8_t*>(std::addressof(src)), sizeof(T)};
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}
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}
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