add sp_transcript

src/seraphis_crypto/sp_transcript.h

@@ -0,0 +1,397 @@
+// Copyright (c) 2022, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Transcript class for assembling data that needs to be hashed.
+
+#pragma once
+
+//local headers
+#include "crypto/crypto.h"
+#include "cryptonote_config.h"
+#include "ringct/rctTypes.h"
+#include "wipeable_string.h"
+
+//third party headers
+#include <boost/utility/string_ref.hpp>
+
+//standard headers
+#include <list>
+#include <string>
+#include <type_traits>
+#include <vector>
+
+//forward declarations
+
+
+namespace sp
+{
+
+////
+// SpTranscriptBuilder
+// - build a transcript
+// - the user must provide a label when trying to append something to the transcript; labels are prepended to objects in
+//   the transcript
+// - data types
+//     - unsigned int: uint_flag || varint(uint_variable)
+//     - signed int: int_flag || uchar{int_variable < 0 ? 1 : 0} || varint(abs(int_variable))
+//     - byte buffer (assumed little-endian): buffer_flag || buffer_length || buffer
+//       - all labels are treated as byte buffers
+//     - named container: container_flag || container_name || data_member1 || ... || container_terminator_flag
+//     - list-type container (same-type elements only): list_flag || list_length || element1 || element2 || ...
+// - the transcript can be used like a string via the .data() and .size() member functions
+// - simple mode: exclude all labels, flags, and lengths
+///
+class SpTranscriptBuilder final
+{
+public:
+//public member types
+    /// transcript builder mode
+    enum class Mode
+    {
+        FULL,
+        SIMPLE
+    };
+
+//constructors
+    /// normal constructor
+    SpTranscriptBuilder(const std::size_t estimated_data_size, const Mode mode) :
+        m_mode{mode}
+    {
+        m_transcript.reserve(2 * estimated_data_size + 20);
+    }
+
+//overloaded operators
+    /// disable copy/move (this is a scoped manager [of the 'transcript' concept])
+    SpTranscriptBuilder& operator=(SpTranscriptBuilder&&) = delete;
+
+//member functions
+    /// append a value to the transcript
+    template <typename T>
+    void append(const boost::string_ref label, const T &value)
+    {
+        this->append_impl(label, value);
+    }
+
+    /// access the transcript data
+    const void* data() const { return m_transcript.data(); }
+    std::size_t size() const { return m_transcript.size(); }
+
+private:
+//member variables
+    /// in simple mode, exclude labels, flags, and lengths
+    Mode m_mode;
+    /// the transcript buffer (wipeable in case it contains sensitive data)
+    epee::wipeable_string m_transcript;
+
+//private member types
+    /// flags for separating items added to the transcript
+    enum SpTranscriptBuilderFlag : unsigned char
+    {
+        UNSIGNED_INTEGER = 0,
+        SIGNED_INTEGER = 1,
+        BYTE_BUFFER = 2,
+        NAMED_CONTAINER = 3,
+        NAMED_CONTAINER_TERMINATOR = 4,
+        LIST_TYPE_CONTAINER = 5
+    };
+
+//transcript builders
+    void append_character(const unsigned char character)
+    {
+        m_transcript += static_cast<char>(character);
+    }
+    void append_uint(const std::uint64_t unsigned_integer)
+    {
+        unsigned char v_variable[(sizeof(std::uint64_t) * 8 + 6) / 7];
+        unsigned char *v_variable_end = v_variable;
+
+        // append uint to string as a varint
+        tools::write_varint(v_variable_end, unsigned_integer);
+        assert(v_variable_end <= v_variable + sizeof(v_variable));
+        m_transcript.append(reinterpret_cast<const char*>(v_variable), v_variable_end - v_variable);
+    }
+    void append_flag(const SpTranscriptBuilderFlag flag)
+    {
+        if (m_mode == Mode::SIMPLE)
+            return;
+
+        static_assert(sizeof(SpTranscriptBuilderFlag) == sizeof(unsigned char), "");
+        this->append_character(static_cast<unsigned char>(flag));
+    }
+    void append_length(const std::size_t length)
+    {
+        if (m_mode == Mode::SIMPLE)
+            return;
+
+        static_assert(sizeof(std::size_t) <= sizeof(std::uint64_t), "");
+        this->append_uint(static_cast<std::uint64_t>(length));
+    }
+    void append_buffer(const void *data, const std::size_t length)
+    {
+        this->append_flag(SpTranscriptBuilderFlag::BYTE_BUFFER);
+        this->append_length(length);
+        m_transcript.append(reinterpret_cast<const char*>(data), length);
+    }
+    void append_label(const boost::string_ref label)
+    {
+        if (m_mode == Mode::SIMPLE ||
+            label.size() == 0)
+            return;
+
+        this->append_buffer(label.data(), label.size());
+    }
+    void append_labeled_buffer(const boost::string_ref label, const void *data, const std::size_t length)
+    {
+        this->append_label(label);
+        this->append_buffer(data, length);
+    }
+    void begin_named_container(const boost::string_ref container_name)
+    {
+        this->append_flag(SpTranscriptBuilderFlag::NAMED_CONTAINER);
+        this->append_label(container_name);
+    }
+    void end_named_container()
+    {
+        this->append_flag(SpTranscriptBuilderFlag::NAMED_CONTAINER_TERMINATOR);
+    }
+    void begin_list_type_container(const std::size_t list_length)
+    {
+        this->append_flag(SpTranscriptBuilderFlag::LIST_TYPE_CONTAINER);
+        this->append_length(list_length);
+    }
+
+//append overloads
+    void append_impl(const boost::string_ref label, const rct::key &key_buffer)
+    {
+        this->append_labeled_buffer(label, key_buffer.bytes, sizeof(key_buffer));
+    }
+    void append_impl(const boost::string_ref label, const rct::ctkey &ctkey)
+    {
+        this->append_label(label);
+        this->append_impl("ctmask", ctkey.mask);
+        this->append_impl("ctdest", ctkey.dest);
+    }
+    void append_impl(const boost::string_ref label, const crypto::secret_key &point_buffer)
+    {
+        this->append_labeled_buffer(label, point_buffer.data, sizeof(point_buffer));
+    }
+    void append_impl(const boost::string_ref label, const crypto::public_key &scalar_buffer)
+    {
+        this->append_labeled_buffer(label, scalar_buffer.data, sizeof(scalar_buffer));
+    }
+    void append_impl(const boost::string_ref label, const crypto::key_derivation &derivation_buffer)
+    {
+        this->append_labeled_buffer(label, derivation_buffer.data, sizeof(derivation_buffer));
+    }
+    void append_impl(const boost::string_ref label, const crypto::key_image &key_image_buffer)
+    {
+        this->append_labeled_buffer(label, key_image_buffer.data, sizeof(key_image_buffer));
+    }
+    void append_impl(const boost::string_ref label, const std::string &string_buffer)
+    {
+        this->append_labeled_buffer(label, string_buffer.data(), string_buffer.size());
+    }
+    void append_impl(const boost::string_ref label, const epee::wipeable_string &string_buffer)
+    {
+        this->append_labeled_buffer(label, string_buffer.data(), string_buffer.size());
+    }
+    void append_impl(const boost::string_ref label, const boost::string_ref string_buffer)
+    {
+        this->append_labeled_buffer(label, string_buffer.data(), string_buffer.size());
+    }
+    template<std::size_t Sz>
+    void append_impl(const boost::string_ref label, const unsigned char(&uchar_buffer)[Sz])
+    {
+        this->append_labeled_buffer(label, uchar_buffer, Sz);
+    }
+    template<std::size_t Sz>
+    void append_impl(const boost::string_ref label, const char(&char_buffer)[Sz])
+    {
+        this->append_labeled_buffer(label, char_buffer, Sz);
+    }
+    void append_impl(const boost::string_ref label, const std::vector<unsigned char> &vector_buffer)
+    {
+        this->append_labeled_buffer(label, vector_buffer.data(), vector_buffer.size());
+    }
+    void append_impl(const boost::string_ref label, const std::vector<char> &vector_buffer)
+    {
+        this->append_labeled_buffer(label, vector_buffer.data(), vector_buffer.size());
+    }
+    void append_impl(const boost::string_ref label, const char single_character)
+    {
+        this->append_label(label);
+        this->append_character(static_cast<unsigned char>(single_character));
+    }
+    void append_impl(const boost::string_ref label, const unsigned char single_character)
+    {
+        this->append_label(label);
+        this->append_character(single_character);
+    }
+    template<typename T,
+        std::enable_if_t<std::is_unsigned<T>::value, bool> = true>
+    void append_impl(const boost::string_ref label, const T unsigned_integer)
+    {
+        static_assert(sizeof(T) <= sizeof(std::uint64_t), "SpTranscriptBuilder: unsupported unsigned integer type.");
+        this->append_label(label);
+        this->append_flag(SpTranscriptBuilderFlag::UNSIGNED_INTEGER);
+        this->append_uint(unsigned_integer);
+    }
+    template<typename T,
+        std::enable_if_t<std::is_integral<T>::value, bool> = true,
+        std::enable_if_t<!std::is_unsigned<T>::value, bool> = true>
+    void append_impl(const boost::string_ref label, const T signed_integer)
+    {
+        using unsigned_type = std::make_unsigned<T>::type;
+        static_assert(sizeof(unsigned_type) <= sizeof(std::uint64_t),
+            "SpTranscriptBuilder: unsupported signed integer type.");
+        this->append_label(label);
+        this->append_flag(SpTranscriptBuilderFlag::SIGNED_INTEGER);
+        this->append_uint(static_cast<std::uint64_t>(static_cast<unsigned_type>(signed_integer)));
+    }
+    template<typename T,
+        std::enable_if_t<!std::is_integral<T>::value, bool> = true>
+    void append_impl(const boost::string_ref label, const T &named_container)
+    {
+        // named containers must satisfy two concepts:
+        //   const boost::string_ref container_name(const T &container);
+        //   void append_to_transcript(const T &container, SpTranscriptBuilder &transcript_inout);
+        //todo: container_name() and append_to_transcript() must be defined in the sp namespace, but that is not generic
+        this->append_label(label);
+        this->begin_named_container(container_name(named_container));
+        append_to_transcript(named_container, *this);  //non-member function assumed to be implemented elsewhere
+        this->end_named_container();
+    }
+    template<typename T>
+    void append_impl(const boost::string_ref label, const std::vector<T> &list_container)
+    {
+        this->append_label(label);
+        this->begin_list_type_container(list_container.size());
+        for (const T &element : list_container)
+            this->append_impl("", element);
+    }
+    template<typename T>
+    void append_impl(const boost::string_ref label, const std::list<T> &list_container)
+    {
+        this->append_label(label);
+        this->begin_list_type_container(list_container.size());
+        for (const T &element : list_container)
+            this->append_impl("", element);
+    }
+};
+
+////
+// SpFSTranscript
+// - build a Fiat-Shamir transcript
+// - main format: prefix || domain_separator || object1_label || object1 || object2_label || object2 || ...
+// note: prefix defaults to "monero"
+///
+class SpFSTranscript final
+{
+public:
+//constructors
+    /// normal constructor: start building a transcript with the domain separator
+    SpFSTranscript(const boost::string_ref domain_separator,
+        const std::size_t estimated_data_size,
+        const boost::string_ref prefix = config::TRANSCRIPT_PREFIX) :
+        m_transcript_builder{15 + domain_separator.size() + estimated_data_size + prefix.size(),
+            SpTranscriptBuilder::Mode::FULL}
+    {
+        // transcript = prefix || domain_separator
+        m_transcript_builder.append("FSp", prefix);
+        m_transcript_builder.append("ds", domain_separator);
+    }
+
+//overloaded operators
+    /// disable copy/move (this is a scoped manager [of the 'transcript' concept])
+    SpFSTranscript& operator=(SpFSTranscript&&) = delete;
+
+//member functions
+    /// build the transcript
+    template<typename T>
+    void append(const boost::string_ref label, const T &value)
+    {
+        m_transcript_builder.append(label, value);
+    }
+
+    /// access the transcript data
+    const void* data() const { return m_transcript_builder.data(); }
+    std::size_t size() const { return m_transcript_builder.size(); }
+
+//member variables
+private:
+    /// underlying transcript builder
+    SpTranscriptBuilder m_transcript_builder;
+};
+
+////
+// SpKDFTranscript
+// - build a data string for a key-derivation function
+// - mainly intended for short transcripts (~128 bytes or less) with fixed-length and statically ordered components
+// - main format: prefix || domain_separator || object1 || object2 || ...
+// - simple transcript mode: no labels, flags, or lengths
+// note: prefix defaults to "monero"
+///
+class SpKDFTranscript final
+{
+public:
+//constructors
+    /// normal constructor: start building a transcript with the domain separator
+    SpKDFTranscript(const boost::string_ref domain_separator,
+        const std::size_t estimated_data_size,
+        const boost::string_ref prefix = config::TRANSCRIPT_PREFIX) :
+        m_transcript_builder{10 + domain_separator.size() + estimated_data_size + prefix.size(),
+            SpTranscriptBuilder::Mode::SIMPLE}
+    {
+        // transcript = prefix || domain_separator
+        m_transcript_builder.append("", prefix);
+        m_transcript_builder.append("", domain_separator);
+    }
+
+//overloaded operators
+    /// disable copy/move (this is a scoped manager [of the 'transcript' concept])
+    SpKDFTranscript& operator=(SpKDFTranscript&&) = delete;
+
+//member functions
+    /// build the transcript
+    template<typename T>
+    void append(const boost::string_ref, const T &value)
+    {
+        m_transcript_builder.append("", value);
+    }
+
+    /// access the transcript data
+    const void* data() const { return m_transcript_builder.data(); }
+    std::size_t size() const { return m_transcript_builder.size(); }
+
+//member variables
+private:
+    /// underlying transcript builder
+    SpTranscriptBuilder m_transcript_builder;
+};
+
+} //namespace sp