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// Copyright (c) 2019, 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.
#include "levin_notify.h"
#include <boost/asio/steady_timer.hpp>
#include <boost/system/system_error.hpp>
#include <chrono>
#include <deque>
#include <stdexcept>
#include "common/expect.h"
#include "common/varint.h"
#include "cryptonote_config.h"
#include "crypto/random.h"
#include "cryptonote_basic/connection_context.h"
#include "cryptonote_protocol/cryptonote_protocol_defs.h"
#include "net/dandelionpp.h"
#include "p2p/net_node.h"
namespace cryptonote
{
namespace levin
{
namespace
{
constexpr std::size_t connection_id_reserve_size = 100;
constexpr const std::chrono::minutes noise_min_epoch{CRYPTONOTE_NOISE_MIN_EPOCH};
constexpr const std::chrono::seconds noise_epoch_range{CRYPTONOTE_NOISE_EPOCH_RANGE};
constexpr const std::chrono::seconds noise_min_delay{CRYPTONOTE_NOISE_MIN_DELAY};
constexpr const std::chrono::seconds noise_delay_range{CRYPTONOTE_NOISE_DELAY_RANGE};
/*! Select a randomized duration from 0 to `range`. The precision will be to
the systems `steady_clock`. As an example, supplying 3 seconds to this
function will select a duration from [0, 3] seconds, and the increments
for the selection will be determined by the `steady_clock` precision
(typically nanoseconds).
\return A randomized duration from 0 to `range`. */
std::chrono::steady_clock::duration random_duration(std::chrono::steady_clock::duration range)
{
using rep = std::chrono::steady_clock::rep;
return std::chrono::steady_clock::duration{crypto::rand_range(rep(0), range.count())};
}
//! \return All outgoing connections supporting fragments in `connections`.
std::vector<boost::uuids::uuid> get_out_connections(connections& p2p)
{
std::vector<boost::uuids::uuid> outs;
outs.reserve(connection_id_reserve_size);
/* The foreach call is serialized with a lock, but should be quick due to
the reserve call so a strand is not used. Investigate if there is lots
of waiting in here. */
p2p.foreach_connection([&outs] (detail::p2p_context& context) {
if (!context.m_is_income)
outs.emplace_back(context.m_connection_id);
return true;
});
return outs;
}
std::string make_tx_payload(std::vector<blobdata>&& txs, const bool pad)
{
NOTIFY_NEW_TRANSACTIONS::request request{};
request.txs = std::move(txs);
if (pad)
{
size_t bytes = 9 /* header */ + 4 /* 1 + 'txs' */ + tools::get_varint_data(request.txs.size()).size();
for(auto tx_blob_it = request.txs.begin(); tx_blob_it!=request.txs.end(); ++tx_blob_it)
bytes += tools::get_varint_data(tx_blob_it->size()).size() + tx_blob_it->size();
// stuff some dummy bytes in to stay safe from traffic volume analysis
static constexpr const size_t granularity = 1024;
size_t padding = granularity - bytes % granularity;
const size_t overhead = 2 /* 1 + '_' */ + tools::get_varint_data(padding).size();
if (overhead > padding)
padding = 0;
else
padding -= overhead;
request._ = std::string(padding, ' ');
std::string arg_buff;
epee::serialization::store_t_to_binary(request, arg_buff);
// we probably lowballed the payload size a bit, so added a but too much. Fix this now.
size_t remove = arg_buff.size() % granularity;
if (remove > request._.size())
request._.clear();
else
request._.resize(request._.size() - remove);
// if the size of _ moved enough, we might lose byte in size encoding, we don't care
}
std::string fullBlob;
if (!epee::serialization::store_t_to_binary(request, fullBlob))
throw std::runtime_error{"Failed to serialize to epee binary format"};
return fullBlob;
}
/* The current design uses `asio::strand`s. The documentation isn't as clear
as it should be - a `strand` has an internal `mutex` and `bool`. The
`mutex` synchronizes thread access and the `bool` is set when a thread is
executing something "in the strand". Therefore, if a callback has lots of
work to do in a `strand`, asio can switch to some other task instead of
blocking 1+ threads to wait for the original thread to complete the task
(as is the case when client code has a `mutex` inside the callback). The
downside is that asio _always_ allocates for the callback, even if it can
be immediately executed. So if all work in a strand is minimal, a lock
may be better.
This code uses a strand per "zone" and a strand per "channel in a zone".
`dispatch` is used heavily, which means "execute immediately in _this_
thread if the strand is not in use, otherwise queue the callback to be
executed immediately after the strand completes its current task".
`post` is used where deferred execution to an `asio::io_service::run`
thread is preferred.
The strand per "zone" is useful because the levin
`foreach_connection` is blocked with a mutex anyway. So this primarily
helps with reducing blocking of a thread attempting a "flood"
notification. Updating/merging the outgoing connections in the
Dandelion++ map is also somewhat expensive.
The strand per "channel" may need a re-visit. The most "expensive" code
is figuring out the noise/notification to send. If levin code is
optimized further, it might be better to just use standard locks per
channel. */
//! A queue of levin messages for a noise i2p/tor link
struct noise_channel
{
explicit noise_channel(boost::asio::io_service& io_service)
: active(nullptr),
queue(),
strand(io_service),
next_noise(io_service),
connection(boost::uuids::nil_uuid())
{}
// `asio::io_service::strand` cannot be copied or moved
noise_channel(const noise_channel&) = delete;
noise_channel& operator=(const noise_channel&) = delete;
// Only read/write these values "inside the strand"
epee::byte_slice active;
std::deque<epee::byte_slice> queue;
boost::asio::io_service::strand strand;
boost::asio::steady_timer next_noise;
boost::uuids::uuid connection;
};
} // anonymous
namespace detail
{
struct zone
{
explicit zone(boost::asio::io_service& io_service, std::shared_ptr<connections> p2p, epee::byte_slice noise_in, bool is_public)
: p2p(std::move(p2p)),
noise(std::move(noise_in)),
next_epoch(io_service),
strand(io_service),
map(),
channels(),
connection_count(0),
is_public(is_public)
{
for (std::size_t count = 0; !noise.empty() && count < CRYPTONOTE_NOISE_CHANNELS; ++count)
channels.emplace_back(io_service);
}
const std::shared_ptr<connections> p2p;
const epee::byte_slice noise; //!< `!empty()` means zone is using noise channels
boost::asio::steady_timer next_epoch;
boost::asio::io_service::strand strand;
net::dandelionpp::connection_map map;//!< Tracks outgoing uuid's for noise channels or Dandelion++ stems
std::deque<noise_channel> channels; //!< Never touch after init; only update elements on `noise_channel.strand`
std::atomic<std::size_t> connection_count; //!< Only update in strand, can be read at any time
const bool is_public; //!< Zone is public ipv4/ipv6 connections
};
} // detail
namespace
{
//! Adds a message to the sending queue of the channel.
class queue_covert_notify
{
std::shared_ptr<detail::zone> zone_;
epee::byte_slice message_; // Requires manual copy constructor
const std::size_t destination_;
public:
queue_covert_notify(std::shared_ptr<detail::zone> zone, epee::byte_slice message, std::size_t destination)
: zone_(std::move(zone)), message_(std::move(message)), destination_(destination)
{}
queue_covert_notify(queue_covert_notify&&) = default;
queue_covert_notify(const queue_covert_notify& source)
: zone_(source.zone_), message_(source.message_.clone()), destination_(source.destination_)
{}
//! \pre Called within `zone_->channels[destionation_].strand`.
void operator()()
{
if (!zone_)
return;
noise_channel& channel = zone_->channels.at(destination_);
assert(channel.strand.running_in_this_thread());
if (!channel.connection.is_nil())
channel.queue.push_back(std::move(message_));
}
};
//! Sends a message to every active connection
class flood_notify
{
std::shared_ptr<detail::zone> zone_;
epee::byte_slice message_; // Requires manual copy
boost::uuids::uuid source_;
public:
explicit flood_notify(std::shared_ptr<detail::zone> zone, epee::byte_slice message, const boost::uuids::uuid& source)
: zone_(std::move(zone)), message_(message.clone()), source_(source)
{}
flood_notify(flood_notify&&) = default;
flood_notify(const flood_notify& source)
: zone_(source.zone_), message_(source.message_.clone()), source_(source.source_)
{}
void operator()() const
{
if (!zone_ || !zone_->p2p)
return;
assert(zone_->strand.running_in_this_thread());
/* The foreach should be quick, but then it iterates and acquires the
same lock for every connection. So do in a strand because two threads
will ping-pong each other with cacheline invalidations. Revisit if
algorithm changes or the locking strategy within the levin config
class changes. */
std::vector<boost::uuids::uuid> connections;
connections.reserve(connection_id_reserve_size);
zone_->p2p->foreach_connection([this, &connections] (detail::p2p_context& context) {
/* Only send to outgoing connections when "flooding" over i2p/tor.
Otherwise this makes the tx linkable to a hidden service address,
making things linkable across connections. */
if (this->source_ != context.m_connection_id && (this->zone_->is_public || !context.m_is_income))
connections.emplace_back(context.m_connection_id);
return true;
});
for (const boost::uuids::uuid& connection : connections)
zone_->p2p->send(message_.clone(), connection);
}
};
//! Updates the connection for a channel.
struct update_channel
{
std::shared_ptr<detail::zone> zone_;
const std::size_t channel_;
const boost::uuids::uuid connection_;
//! \pre Called within `stem_.strand`.
void operator()() const
{
if (!zone_)
return;
noise_channel& channel = zone_->channels.at(channel_);
assert(channel.strand.running_in_this_thread());
static_assert(
CRYPTONOTE_MAX_FRAGMENTS <= (noise_min_epoch / (noise_min_delay + noise_delay_range)),
"Max fragments more than the max that can be sent in an epoch"
);
/* This clears the active message so that a message "in-flight" is
restarted. DO NOT try to send the remainder of the fragments, this
additional send time can leak that this node was sending out a real
notify (tx) instead of dummy noise. */
channel.connection = connection_;
channel.active = nullptr;
if (connection_.is_nil())
channel.queue.clear();
}
};
//! Merges `out_connections_` into the existing `zone_->map`.
struct update_channels
{
std::shared_ptr<detail::zone> zone_;
std::vector<boost::uuids::uuid> out_connections_;
//! \pre Called within `zone->strand`.
static void post(std::shared_ptr<detail::zone> zone)
{
if (!zone)
return;
assert(zone->strand.running_in_this_thread());
zone->connection_count = zone->map.size();
for (auto id = zone->map.begin(); id != zone->map.end(); ++id)
{
const std::size_t i = id - zone->map.begin();
zone->channels[i].strand.post(update_channel{zone, i, *id});
}
}
//! \pre Called within `zone_->strand`.
void operator()()
{
if (!zone_)
return;
assert(zone_->strand.running_in_this_thread());
if (zone_->map.update(std::move(out_connections_)))
post(std::move(zone_));
}
};
//! Swaps out noise channels entirely; new epoch start.
class change_channels
{
std::shared_ptr<detail::zone> zone_;
net::dandelionpp::connection_map map_; // Requires manual copy constructor
public:
explicit change_channels(std::shared_ptr<detail::zone> zone, net::dandelionpp::connection_map map)
: zone_(std::move(zone)), map_(std::move(map))
{}
change_channels(change_channels&&) = default;
change_channels(const change_channels& source)
: zone_(source.zone_), map_(source.map_.clone())
{}
//! \pre Called within `zone_->strand`.
void operator()()
{
if (!zone_)
return
assert(zone_->strand.running_in_this_thread());
zone_->map = std::move(map_);
update_channels::post(std::move(zone_));
}
};
//! Sends a noise packet or real notification and sets timer for next call.
struct send_noise
{
std::shared_ptr<detail::zone> zone_;
const std::size_t channel_;
static void wait(const std::chrono::steady_clock::time_point start, std::shared_ptr<detail::zone> zone, const std::size_t index)
{
if (!zone)
return;
noise_channel& channel = zone->channels.at(index);
channel.next_noise.expires_at(start + noise_min_delay + random_duration(noise_delay_range));
channel.next_noise.async_wait(
channel.strand.wrap(send_noise{std::move(zone), index})
);
}
//! \pre Called within `zone_->channels[channel_].strand`.
void operator()(boost::system::error_code error)
{
if (!zone_ || !zone_->p2p || zone_->noise.empty())
return;
if (error && error != boost::system::errc::operation_canceled)
throw boost::system::system_error{error, "send_noise timer failed"};
assert(zone_->channels.at(channel_).strand.running_in_this_thread());
const auto start = std::chrono::steady_clock::now();
noise_channel& channel = zone_->channels.at(channel_);
if (!channel.connection.is_nil())
{
epee::byte_slice message = nullptr;
if (!channel.active.empty())
message = channel.active.take_slice(zone_->noise.size());
else if (!channel.queue.empty())
{
channel.active = channel.queue.front().clone();
message = channel.active.take_slice(zone_->noise.size());
}
else
message = zone_->noise.clone();
if (zone_->p2p->send(std::move(message), channel.connection))
{
if (!channel.queue.empty() && channel.active.empty())
channel.queue.pop_front();
}
else
{
channel.active = nullptr;
channel.connection = boost::uuids::nil_uuid();
zone_->strand.post(
update_channels{zone_, get_out_connections(*zone_->p2p)}
);
}
}
wait(start, std::move(zone_), channel_);
}
};
//! Prepares connections for new channel epoch and sets timer for next epoch
struct start_epoch
{
// Variables allow for Dandelion++ extension
std::shared_ptr<detail::zone> zone_;
std::chrono::seconds min_epoch_;
std::chrono::seconds epoch_range_;
std::size_t count_;
//! \pre Should not be invoked within any strand to prevent blocking.
void operator()(const boost::system::error_code error = {})
{
if (!zone_ || !zone_->p2p)
return;
if (error && error != boost::system::errc::operation_canceled)
throw boost::system::system_error{error, "start_epoch timer failed"};
const auto start = std::chrono::steady_clock::now();
zone_->strand.dispatch(
change_channels{zone_, net::dandelionpp::connection_map{get_out_connections(*(zone_->p2p)), count_}}
);
detail::zone& alias = *zone_;
alias.next_epoch.expires_at(start + min_epoch_ + random_duration(epoch_range_));
alias.next_epoch.async_wait(start_epoch{std::move(*this)});
}
};
} // anonymous
notify::notify(boost::asio::io_service& service, std::shared_ptr<connections> p2p, epee::byte_slice noise, bool is_public)
: zone_(std::make_shared<detail::zone>(service, std::move(p2p), std::move(noise), is_public))
{
if (!zone_->p2p)
throw std::logic_error{"cryptonote::levin::notify cannot have nullptr p2p argument"};
if (!zone_->noise.empty())
{
const auto now = std::chrono::steady_clock::now();
start_epoch{zone_, noise_min_epoch, noise_epoch_range, CRYPTONOTE_NOISE_CHANNELS}();
for (std::size_t channel = 0; channel < zone_->channels.size(); ++channel)
send_noise::wait(now, zone_, channel);
}
}
notify::~notify() noexcept
{}
notify::status notify::get_status() const noexcept
{
if (!zone_)
return {false, false};
return {!zone_->noise.empty(), CRYPTONOTE_NOISE_CHANNELS <= zone_->connection_count};
}
void notify::new_out_connection()
{
if (!zone_ || zone_->noise.empty() || CRYPTONOTE_NOISE_CHANNELS <= zone_->connection_count)
return;
zone_->strand.dispatch(
update_channels{zone_, get_out_connections(*(zone_->p2p))}
);
}
void notify::run_epoch()
{
if (!zone_)
return;
zone_->next_epoch.cancel();
}
void notify::run_stems()
{
if (!zone_)
return;
for (noise_channel& channel : zone_->channels)
channel.next_noise.cancel();
}
bool notify::send_txs(std::vector<blobdata> txs, const boost::uuids::uuid& source, const bool pad_txs)
{
if (!zone_)
return false;
if (!zone_->noise.empty() && !zone_->channels.empty())
{
// covert send in "noise" channel
static_assert(
CRYPTONOTE_MAX_FRAGMENTS * CRYPTONOTE_NOISE_BYTES <= LEVIN_DEFAULT_MAX_PACKET_SIZE, "most nodes will reject this fragment setting"
);
// padding is not useful when using noise mode
const std::string payload = make_tx_payload(std::move(txs), false);
epee::byte_slice message = epee::levin::make_fragmented_notify(
zone_->noise, NOTIFY_NEW_TRANSACTIONS::ID, epee::strspan<std::uint8_t>(payload)
);
if (CRYPTONOTE_MAX_FRAGMENTS * zone_->noise.size() < message.size())
{
MERROR("notify::send_txs provided message exceeding covert fragment size");
return false;
}
for (std::size_t channel = 0; channel < zone_->channels.size(); ++channel)
{
zone_->channels[channel].strand.dispatch(
queue_covert_notify{zone_, message.clone(), channel}
);
}
}
else
{
const std::string payload = make_tx_payload(std::move(txs), pad_txs);
epee::byte_slice message =
epee::levin::make_notify(NOTIFY_NEW_TRANSACTIONS::ID, epee::strspan<std::uint8_t>(payload));
// traditional monero send technique
zone_->strand.dispatch(flood_notify{zone_, std::move(message), source});
}
return true;
}
} // levin
} // net
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