git / moonbite-core / src/util/asmap.cpp · raw

// Copyright (c) 2019-2020 The Bitcoin Core developers// Distributed under the MIT software license, see the accompanying// file COPYING or http://www.opensource.org/licenses/mit-license.php.#include <map>#include <vector>#include <assert.h>#include <crypto/common.h>namespace {constexpr uint32_t INVALID = 0xFFFFFFFF;uint32_t DecodeBits(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos, uint8_t minval, const std::vector<uint8_t> &bit_sizes){    uint32_t val = minval;    bool bit;    for (std::vector<uint8_t>::const_iterator bit_sizes_it = bit_sizes.begin();        bit_sizes_it != bit_sizes.end(); ++bit_sizes_it) {        if (bit_sizes_it + 1 != bit_sizes.end()) {            if (bitpos == endpos) break;            bit = *bitpos;            bitpos++;        } else {            bit = 0;        }        if (bit) {            val += (1 << *bit_sizes_it);        } else {            for (int b = 0; b < *bit_sizes_it; b++) {                if (bitpos == endpos) return INVALID; // Reached EOF in mantissa                bit = *bitpos;                bitpos++;                val += bit << (*bit_sizes_it - 1 - b);            }            return val;        }    }    return INVALID; // Reached EOF in exponent}enum class Instruction : uint32_t{    RETURN = 0,    JUMP = 1,    MATCH = 2,    DEFAULT = 3,};const std::vector<uint8_t> TYPE_BIT_SIZES{0, 0, 1};Instruction DecodeType(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos){    return Instruction(DecodeBits(bitpos, endpos, 0, TYPE_BIT_SIZES));}const std::vector<uint8_t> ASN_BIT_SIZES{15, 16, 17, 18, 19, 20, 21, 22, 23, 24};uint32_t DecodeASN(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos){    return DecodeBits(bitpos, endpos, 1, ASN_BIT_SIZES);}const std::vector<uint8_t> MATCH_BIT_SIZES{1, 2, 3, 4, 5, 6, 7, 8};uint32_t DecodeMatch(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos){    return DecodeBits(bitpos, endpos, 2, MATCH_BIT_SIZES);}const std::vector<uint8_t> JUMP_BIT_SIZES{5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30};uint32_t DecodeJump(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos){    return DecodeBits(bitpos, endpos, 17, JUMP_BIT_SIZES);}}uint32_t Interpret(const std::vector<bool> &asmap, const std::vector<bool> &ip){    std::vector<bool>::const_iterator pos = asmap.begin();    const std::vector<bool>::const_iterator endpos = asmap.end();    uint8_t bits = ip.size();    uint32_t default_asn = 0;    uint32_t jump, match, matchlen;    Instruction opcode;    while (pos != endpos) {        opcode = DecodeType(pos, endpos);        if (opcode == Instruction::RETURN) {            default_asn = DecodeASN(pos, endpos);            if (default_asn == INVALID) break; // ASN straddles EOF            return default_asn;        } else if (opcode == Instruction::JUMP) {            jump = DecodeJump(pos, endpos);            if (jump == INVALID) break; // Jump offset straddles EOF            if (bits == 0) break; // No input bits left            if (pos + jump < pos) break; // overflow            if (pos + jump >= endpos) break; // Jumping past EOF            if (ip[ip.size() - bits]) {                pos += jump;            }            bits--;        } else if (opcode == Instruction::MATCH) {            match = DecodeMatch(pos, endpos);            if (match == INVALID) break; // Match bits straddle EOF            matchlen = CountBits(match) - 1;            if (bits < matchlen) break; // Not enough input bits            for (uint32_t bit = 0; bit < matchlen; bit++) {                if ((ip[ip.size() - bits]) != ((match >> (matchlen - 1 - bit)) & 1)) {                    return default_asn;                }                bits--;            }        } else if (opcode == Instruction::DEFAULT) {            default_asn = DecodeASN(pos, endpos);            if (default_asn == INVALID) break; // ASN straddles EOF        } else {            break; // Instruction straddles EOF        }    }    assert(false); // Reached EOF without RETURN, or aborted (see any of the breaks above) - should have been caught by SanityCheckASMap below    return 0; // 0 is not a valid ASN}bool SanityCheckASMap(const std::vector<bool>& asmap, int bits){    const std::vector<bool>::const_iterator begin = asmap.begin(), endpos = asmap.end();    std::vector<bool>::const_iterator pos = begin;    std::vector<std::pair<uint32_t, int>> jumps; // All future positions we may jump to (bit offset in asmap -> bits to consume left)    jumps.reserve(bits);    Instruction prevopcode = Instruction::JUMP;    bool had_incomplete_match = false;    while (pos != endpos) {        uint32_t offset = pos - begin;        if (!jumps.empty() && offset >= jumps.back().first) return false; // There was a jump into the middle of the previous instruction        Instruction opcode = DecodeType(pos, endpos);        if (opcode == Instruction::RETURN) {            if (prevopcode == Instruction::DEFAULT) return false; // There should not be any RETURN immediately after a DEFAULT (could be combined into just RETURN)            uint32_t asn = DecodeASN(pos, endpos);            if (asn == INVALID) return false; // ASN straddles EOF            if (jumps.empty()) {                // Nothing to execute anymore                if (endpos - pos > 7) return false; // Excessive padding                while (pos != endpos) {                    if (*pos) return false; // Nonzero padding bit                    ++pos;                }                return true; // Sanely reached EOF            } else {                // Continue by pretending we jumped to the next instruction                offset = pos - begin;                if (offset != jumps.back().first) return false; // Unreachable code                bits = jumps.back().second; // Restore the number of bits we would have had left after this jump                jumps.pop_back();                prevopcode = Instruction::JUMP;            }        } else if (opcode == Instruction::JUMP) {            uint32_t jump = DecodeJump(pos, endpos);            if (jump == INVALID) return false; // Jump offset straddles EOF            if (pos + jump < pos) return false; // overflow            if (pos + jump > endpos) return false; // Jump out of range            if (bits == 0) return false; // Consuming bits past the end of the input            --bits;            uint32_t jump_offset = pos - begin + jump;            if (!jumps.empty() && jump_offset >= jumps.back().first) return false; // Intersecting jumps            jumps.emplace_back(jump_offset, bits);            prevopcode = Instruction::JUMP;        } else if (opcode == Instruction::MATCH) {            uint32_t match = DecodeMatch(pos, endpos);            if (match == INVALID) return false; // Match bits straddle EOF            int matchlen = CountBits(match) - 1;            if (prevopcode != Instruction::MATCH) had_incomplete_match = false;            if (matchlen < 8 && had_incomplete_match) return false; // Within a sequence of matches only at most one should be incomplete            had_incomplete_match = (matchlen < 8);            if (bits < matchlen) return false; // Consuming bits past the end of the input            bits -= matchlen;            prevopcode = Instruction::MATCH;        } else if (opcode == Instruction::DEFAULT) {            if (prevopcode == Instruction::DEFAULT) return false; // There should not be two successive DEFAULTs (they could be combined into one)            uint32_t asn = DecodeASN(pos, endpos);            if (asn == INVALID) return false; // ASN straddles EOF            prevopcode = Instruction::DEFAULT;        } else {            return false; // Instruction straddles EOF        }    }    return false; // Reached EOF without RETURN instruction}