diff options
Diffstat (limited to 'src/net.cpp')
| -rw-r--r-- | src/net.cpp | 45 |
1 files changed, 39 insertions, 6 deletions
diff --git a/src/net.cpp b/src/net.cpp index e35d05cec0..0fd95dfe3f 100644 --- a/src/net.cpp +++ b/src/net.cpp @@ -94,6 +94,7 @@ const std::string NET_MESSAGE_COMMAND_OTHER = "*other*"; static const uint64_t RANDOMIZER_ID_NETGROUP = 0x6c0edd8036ef4036ULL; // SHA256("netgroup")[0:8] static const uint64_t RANDOMIZER_ID_LOCALHOSTNONCE = 0xd93e69e2bbfa5735ULL; // SHA256("localhostnonce")[0:8] +static const uint64_t RANDOMIZER_ID_ADDRCACHE = 0x1cf2e4ddd306dda9ULL; // SHA256("addrcache")[0:8] // // Global state variables // @@ -2560,15 +2561,47 @@ std::vector<CAddress> CConnman::GetAddresses(size_t max_addresses, size_t max_pc return addresses; } -std::vector<CAddress> CConnman::GetAddresses(Network requestor_network, size_t max_addresses, size_t max_pct) +std::vector<CAddress> CConnman::GetAddresses(CNode& requestor, size_t max_addresses, size_t max_pct) { + SOCKET socket; + WITH_LOCK(requestor.cs_hSocket, socket = requestor.hSocket); + auto local_socket_bytes = GetBindAddress(socket).GetAddrBytes(); + uint64_t cache_id = GetDeterministicRandomizer(RANDOMIZER_ID_ADDRCACHE) + .Write(requestor.addr.GetNetwork()) + .Write(local_socket_bytes.data(), local_socket_bytes.size()) + .Finalize(); const auto current_time = GetTime<std::chrono::microseconds>(); - if (m_addr_response_caches.find(requestor_network) == m_addr_response_caches.end() || - m_addr_response_caches[requestor_network].m_update_addr_response < current_time) { - m_addr_response_caches[requestor_network].m_addrs_response_cache = GetAddresses(max_addresses, max_pct); - m_addr_response_caches[requestor_network].m_update_addr_response = current_time + std::chrono::hours(21) + GetRandMillis(std::chrono::hours(6)); + auto r = m_addr_response_caches.emplace(cache_id, CachedAddrResponse{}); + CachedAddrResponse& cache_entry = r.first->second; + if (cache_entry.m_cache_entry_expiration < current_time) { // If emplace() added new one it has expiration 0. + cache_entry.m_addrs_response_cache = GetAddresses(max_addresses, max_pct); + // Choosing a proper cache lifetime is a trade-off between the privacy leak minimization + // and the usefulness of ADDR responses to honest users. + // + // Longer cache lifetime makes it more difficult for an attacker to scrape + // enough AddrMan data to maliciously infer something useful. + // By the time an attacker scraped enough AddrMan records, most of + // the records should be old enough to not leak topology info by + // e.g. analyzing real-time changes in timestamps. + // + // It takes only several hundred requests to scrape everything from an AddrMan containing 100,000 nodes, + // so ~24 hours of cache lifetime indeed makes the data less inferable by the time + // most of it could be scraped (considering that timestamps are updated via + // ADDR self-announcements and when nodes communicate). + // We also should be robust to those attacks which may not require scraping *full* victim's AddrMan + // (because even several timestamps of the same handful of nodes may leak privacy). + // + // On the other hand, longer cache lifetime makes ADDR responses + // outdated and less useful for an honest requestor, e.g. if most nodes + // in the ADDR response are no longer active. + // + // However, the churn in the network is known to be rather low. Since we consider + // nodes to be "terrible" (see IsTerrible()) if the timestamps are older than 30 days, + // max. 24 hours of "penalty" due to cache shouldn't make any meaningful difference + // in terms of the freshness of the response. + cache_entry.m_cache_entry_expiration = current_time + std::chrono::hours(21) + GetRandMillis(std::chrono::hours(6)); } - return m_addr_response_caches[requestor_network].m_addrs_response_cache; + return cache_entry.m_addrs_response_cache; } bool CConnman::AddNode(const std::string& strNode) |