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protocol: option to pad transaction relay to the next kB

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To help protect one's privacy from traffic volume analysis
for people using Tor or I2P. This will really fly once we
relay txes on a timer rather than on demand, though.

Off by default for now since it's wasteful and doesn't bring
anything until I2P's in.
This commit is contained in:
moneromooo-monero 2018-11-02 22:27:25 +00:00
parent 963d247154
commit 3dba7f252e
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GPG key ID: 686F07454D6CEFC3
6 changed files with 52 additions and 1 deletions
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2
src/cryptonote_protocol/cryptonote_protocol_defs.h
View file

@ -146,9 +146,11 @@ namespace cryptonote
struct request
{
std::vector<blobdata> txs;
std::string _; // padding
BEGIN_KV_SERIALIZE_MAP()
KV_SERIALIZE(txs)
KV_SERIALIZE(_)
END_KV_SERIALIZE_MAP()
};
};

31
src/cryptonote_protocol/cryptonote_protocol_handler.inl
View file

@ -1724,8 +1724,39 @@ skip:
bool t_cryptonote_protocol_handler<t_core>::relay_transactions(NOTIFY_NEW_TRANSACTIONS::request& arg, cryptonote_connection_context& exclude_context)
{
// no check for success, so tell core they're relayed unconditionally
const bool pad_transactions = m_core.pad_transactions();
size_t bytes = pad_transactions ? 9 /* header */ + 4 /* 1 + 'txs' */ + tools::get_varint_data(arg.txs.size()).size() : 0;
for(auto tx_blob_it = arg.txs.begin(); tx_blob_it!=arg.txs.end(); ++tx_blob_it)
{
m_core.on_transaction_relayed(*tx_blob_it);
if (pad_transactions)
bytes += tools::get_varint_data(tx_blob_it->size()).size() + tx_blob_it->size();
}
if (pad_transactions)
{
// stuff some dummy bytes in to stay safe from traffic volume analysis
static constexpr 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;
arg._ = std::string(padding, ' ');
std::string arg_buff;
epee::serialization::store_t_to_binary(arg, 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 > arg._.size())
arg._.clear();
else
arg._.resize(arg._.size() - remove);
// if the size of _ moved enough, we might lose byte in size encoding, we don't care
}
return relay_post_notify<NOTIFY_NEW_TRANSACTIONS>(arg, exclude_context);
}
//------------------------------------------------------------------------------------------------------------------------