opendht/src/infohash.cpp

/*
 *  Copyright (C) 2014-2017 Savoir-faire Linux Inc.
 *  Author : Adrien Béraud <adrien.beraud@savoirfairelinux.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program. If not, see <https://www.gnu.org/licenses/>.
 */

#include "infohash.h"
#include "rng.h"

extern "C" {
#include <gnutls/gnutls.h>
}

#include <functional>
#include <sstream>
#include <cstdio>

namespace dht {

InfoHash::InfoHash(const std::string& hex) {
    if (hex.size() < 2*HASH_LEN) {
        fill(0);
        return;
    }
    const auto p = (const char*)hex.data();
    for (size_t i = 0; i < HASH_LEN; i++) {
        unsigned res = 0;
        sscanf(p + 2*i, "%02x", &res);
        (*this)[i] = res;
    }
}

InfoHash
InfoHash::get(const uint8_t* data, size_t data_len)
{
    InfoHash h;
    size_t s = h.size();
    const gnutls_datum_t gnudata = {(uint8_t*)data, (unsigned)data_len};
    const gnutls_digest_algorithm_t algo =  (HASH_LEN == 64) ? GNUTLS_DIG_SHA512 : (
                                            (HASH_LEN == 32) ? GNUTLS_DIG_SHA256 : (
                                            (HASH_LEN == 20) ? GNUTLS_DIG_SHA1   :
                                            GNUTLS_DIG_NULL ));
    static_assert(algo != GNUTLS_DIG_NULL, "Can't find hash function to use.");
    int rc = gnutls_fingerprint(algo, &gnudata, h.data(), &s);
    if (rc == 0 && s == HASH_LEN)
        return h;
    throw std::runtime_error(std::string("Error hashing: ") + gnutls_strerror(rc));
}

InfoHash
InfoHash::getRandom()
{
    InfoHash h;
    crypto::random_device rdev;
    std::uniform_int_distribution<uint32_t> rand_int;
    auto a = reinterpret_cast<uint32_t*>(h.data());
    auto b = reinterpret_cast<uint32_t*>(h.data() + h.size());
    std::generate(a, b, std::bind(rand_int, std::ref(rdev)));
    return h;
}

struct HexMap : public std::array<std::array<char, 2>, 256> {
    HexMap() {
        for (size_t i=0; i<size(); i++) {
            auto& e = (*this)[i];
            e[0] = hex_digits[(i >> 4) & 0x0F];
            e[1] = hex_digits[i & 0x0F];
        }
    }
private:
    static constexpr const char* hex_digits = "0123456789abcdef";
};

const char*
InfoHash::to_c_str() const
{
    static const HexMap map;
    thread_local std::array<char, HASH_LEN*2+1> buf;
    for (size_t i=0; i<HASH_LEN; i++) {
        auto b = buf.data()+i*2;
        const auto& m = map[(*this)[i]];
        *((uint16_t*)b) = *((uint16_t*)&m);
    }
    return buf.data();
}

std::string
InfoHash::toString() const
{
    return std::string(to_c_str(), HASH_LEN*2);
}

std::ostream& operator<< (std::ostream& s, const InfoHash& h)
{
    s.write(h.to_c_str(), HASH_LEN*2);
    return s;
}

std::istream& operator>> (std::istream& s, InfoHash& h)
{
    std::array<char, HASH_LEN*2> dat;
    s.exceptions(std::istream::eofbit | std::istream::failbit);
    s.read(&(*dat.begin()), dat.size());
    for (size_t i = 0; i < HASH_LEN; i++) {
        unsigned res = 0;
        sscanf(dat.data() + 2*i, "%02x", &res);
        h[i] = res;
    }
    return s;
}

void
NodeExport::msgpack_unpack(msgpack::object o)
{
    if (o.type != msgpack::type::MAP)
        throw msgpack::type_error();
    if (o.via.map.size < 2)
        throw msgpack::type_error();
    if (o.via.map.ptr[0].key.as<std::string>() != "id")
        throw msgpack::type_error();
    if (o.via.map.ptr[1].key.as<std::string>() != "addr")
        throw msgpack::type_error();
    const auto& addr = o.via.map.ptr[1].val;
    if (addr.type != msgpack::type::BIN)
        throw msgpack::type_error();
    if (addr.via.bin.size > sizeof(sockaddr_storage))
        throw msgpack::type_error();
    id.msgpack_unpack(o.via.map.ptr[0].val);
    sslen = addr.via.bin.size;
    std::copy_n(addr.via.bin.ptr, addr.via.bin.size, (char*)&ss);
}

std::ostream& operator<< (std::ostream& s, const NodeExport& h)
{
    msgpack::pack(s, h);
    return s;
}

}