diff --git a/src/Makefile.am b/src/Makefile.am index bdad5e20c7..0813c41c48 100644 --- a/src/Makefile.am +++ b/src/Makefile.am @@ -271,7 +271,9 @@ BITCOIN_CORE_H = \ node/blockstorage.h \ node/coin.h \ node/coinstats.h \ + node/connection_types.h \ node/context.h \ + node/eviction.h \ node/psbt.h \ node/transaction.h \ node/ui_interface.h \ @@ -499,7 +501,9 @@ libbitcoin_server_a_SOURCES = \ node/blockstorage.cpp \ node/coin.cpp \ node/coinstats.cpp \ + node/connection_types.cpp \ node/context.cpp \ + node/eviction.cpp \ node/interfaces.cpp \ node/psbt.cpp \ node/transaction.cpp \ diff --git a/src/net.cpp b/src/net.cpp index ba03e2703a..e114699b4b 100644 --- a/src/net.cpp +++ b/src/net.cpp @@ -17,6 +17,7 @@ #include #include #include +#include #include #include #include @@ -680,26 +681,6 @@ bool CNode::IsBlockRelayOnly() const { return (ignores_incoming_txs && !HasPermission(NetPermissionFlags::Relay)) || IsBlockOnlyConn(); } -std::string ConnectionTypeAsString(ConnectionType conn_type) -{ - switch (conn_type) { - case ConnectionType::INBOUND: - return "inbound"; - case ConnectionType::MANUAL: - return "manual"; - case ConnectionType::FEELER: - return "feeler"; - case ConnectionType::OUTBOUND_FULL_RELAY: - return "outbound-full-relay"; - case ConnectionType::BLOCK_RELAY: - return "block-relay-only"; - case ConnectionType::ADDR_FETCH: - return "addr-fetch"; - } // no default case, so the compiler can warn about missing cases - - assert(false); -} - CService CNode::GetAddrLocal() const { AssertLockNotHeld(m_addr_local_mutex); @@ -1085,210 +1066,6 @@ std::pair CConnman::SocketSendData(CNode& node) const return {nSentSize, data_left}; } -static bool ReverseCompareNodeMinPingTime(const NodeEvictionCandidate& a, const NodeEvictionCandidate& b) -{ - return a.m_min_ping_time > b.m_min_ping_time; -} - -static bool ReverseCompareNodeTimeConnected(const NodeEvictionCandidate& a, const NodeEvictionCandidate& b) -{ - return a.m_connected > b.m_connected; -} - -static bool CompareNetGroupKeyed(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b) { - return a.nKeyedNetGroup < b.nKeyedNetGroup; -} - -static bool CompareNodeBlockTime(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b) -{ - // There is a fall-through here because it is common for a node to have many peers which have not yet relayed a block. - if (a.m_last_block_time != b.m_last_block_time) return a.m_last_block_time < b.m_last_block_time; - if (a.fRelevantServices != b.fRelevantServices) return b.fRelevantServices; - return a.m_connected > b.m_connected; -} - -static bool CompareNodeTXTime(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b) -{ - // There is a fall-through here because it is common for a node to have more than a few peers that have not yet relayed txn. - if (a.m_last_tx_time != b.m_last_tx_time) return a.m_last_tx_time < b.m_last_tx_time; - if (a.m_relay_txs != b.m_relay_txs) return b.m_relay_txs; - if (a.fBloomFilter != b.fBloomFilter) return a.fBloomFilter; - return a.m_connected > b.m_connected; -} - -// Pick out the potential block-relay only peers, and sort them by last block time. -static bool CompareNodeBlockRelayOnlyTime(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b) -{ - if (a.m_relay_txs != b.m_relay_txs) return a.m_relay_txs; - if (a.m_last_block_time != b.m_last_block_time) return a.m_last_block_time < b.m_last_block_time; - if (a.fRelevantServices != b.fRelevantServices) return b.fRelevantServices; - return a.m_connected > b.m_connected; -} - -/** - * Sort eviction candidates by network/localhost and connection uptime. - * Candidates near the beginning are more likely to be evicted, and those - * near the end are more likely to be protected, e.g. less likely to be evicted. - * - First, nodes that are not `is_local` and that do not belong to `network`, - * sorted by increasing uptime (from most recently connected to connected longer). - * - Then, nodes that are `is_local` or belong to `network`, sorted by increasing uptime. - */ -struct CompareNodeNetworkTime { - const bool m_is_local; - const Network m_network; - CompareNodeNetworkTime(bool is_local, Network network) : m_is_local(is_local), m_network(network) {} - bool operator()(const NodeEvictionCandidate& a, const NodeEvictionCandidate& b) const - { - if (m_is_local && a.m_is_local != b.m_is_local) return b.m_is_local; - if ((a.m_network == m_network) != (b.m_network == m_network)) return b.m_network == m_network; - return a.m_connected > b.m_connected; - }; -}; - -//! Sort an array by the specified comparator, then erase the last K elements where predicate is true. -template -static void EraseLastKElements( - std::vector& elements, Comparator comparator, size_t k, - std::function predicate = [](const NodeEvictionCandidate& n) { return true; }) -{ - std::sort(elements.begin(), elements.end(), comparator); - size_t eraseSize = std::min(k, elements.size()); - elements.erase(std::remove_if(elements.end() - eraseSize, elements.end(), predicate), elements.end()); -} - -void ProtectEvictionCandidatesByRatio(std::vector& eviction_candidates) -{ - // Protect the half of the remaining nodes which have been connected the longest. - // This replicates the non-eviction implicit behavior, and precludes attacks that start later. - // To favorise the diversity of our peer connections, reserve up to half of these protected - // spots for Tor/onion, localhost, I2P, and CJDNS peers, even if they're not longest uptime - // overall. This helps protect these higher-latency peers that tend to be otherwise - // disadvantaged under our eviction criteria. - const size_t initial_size = eviction_candidates.size(); - const size_t total_protect_size{initial_size / 2}; - - // Disadvantaged networks to protect. In the case of equal counts, earlier array members - // have the first opportunity to recover unused slots from the previous iteration. - struct Net { bool is_local; Network id; size_t count; }; - std::array networks{ - {{false, NET_CJDNS, 0}, {false, NET_I2P, 0}, {/*localhost=*/true, NET_MAX, 0}, {false, NET_ONION, 0}}}; - - // Count and store the number of eviction candidates per network. - for (Net& n : networks) { - n.count = std::count_if(eviction_candidates.cbegin(), eviction_candidates.cend(), - [&n](const NodeEvictionCandidate& c) { - return n.is_local ? c.m_is_local : c.m_network == n.id; - }); - } - // Sort `networks` by ascending candidate count, to give networks having fewer candidates - // the first opportunity to recover unused protected slots from the previous iteration. - std::stable_sort(networks.begin(), networks.end(), [](Net a, Net b) { return a.count < b.count; }); - - // Protect up to 25% of the eviction candidates by disadvantaged network. - const size_t max_protect_by_network{total_protect_size / 2}; - size_t num_protected{0}; - - while (num_protected < max_protect_by_network) { - // Count the number of disadvantaged networks from which we have peers to protect. - auto num_networks = std::count_if(networks.begin(), networks.end(), [](const Net& n) { return n.count; }); - if (num_networks == 0) { - break; - } - const size_t disadvantaged_to_protect{max_protect_by_network - num_protected}; - const size_t protect_per_network{std::max(disadvantaged_to_protect / num_networks, static_cast(1))}; - // Early exit flag if there are no remaining candidates by disadvantaged network. - bool protected_at_least_one{false}; - - for (Net& n : networks) { - if (n.count == 0) continue; - const size_t before = eviction_candidates.size(); - EraseLastKElements(eviction_candidates, CompareNodeNetworkTime(n.is_local, n.id), - protect_per_network, [&n](const NodeEvictionCandidate& c) { - return n.is_local ? c.m_is_local : c.m_network == n.id; - }); - const size_t after = eviction_candidates.size(); - if (before > after) { - protected_at_least_one = true; - const size_t delta{before - after}; - num_protected += delta; - if (num_protected >= max_protect_by_network) { - break; - } - n.count -= delta; - } - } - if (!protected_at_least_one) { - break; - } - } - - // Calculate how many we removed, and update our total number of peers that - // we want to protect based on uptime accordingly. - assert(num_protected == initial_size - eviction_candidates.size()); - const size_t remaining_to_protect{total_protect_size - num_protected}; - EraseLastKElements(eviction_candidates, ReverseCompareNodeTimeConnected, remaining_to_protect); -} - -[[nodiscard]] std::optional SelectNodeToEvict(std::vector&& vEvictionCandidates) -{ - // Protect connections with certain characteristics - - // Deterministically select 4 peers to protect by netgroup. - // An attacker cannot predict which netgroups will be protected - EraseLastKElements(vEvictionCandidates, CompareNetGroupKeyed, 4); - // Protect the 8 nodes with the lowest minimum ping time. - // An attacker cannot manipulate this metric without physically moving nodes closer to the target. - EraseLastKElements(vEvictionCandidates, ReverseCompareNodeMinPingTime, 8); - // Protect 4 nodes that most recently sent us novel transactions accepted into our mempool. - // An attacker cannot manipulate this metric without performing useful work. - EraseLastKElements(vEvictionCandidates, CompareNodeTXTime, 4); - // Protect up to 8 non-tx-relay peers that have sent us novel blocks. - EraseLastKElements(vEvictionCandidates, CompareNodeBlockRelayOnlyTime, 8, - [](const NodeEvictionCandidate& n) { return !n.m_relay_txs && n.fRelevantServices; }); - - // Protect 4 nodes that most recently sent us novel blocks. - // An attacker cannot manipulate this metric without performing useful work. - EraseLastKElements(vEvictionCandidates, CompareNodeBlockTime, 4); - - // Protect some of the remaining eviction candidates by ratios of desirable - // or disadvantaged characteristics. - ProtectEvictionCandidatesByRatio(vEvictionCandidates); - - if (vEvictionCandidates.empty()) return std::nullopt; - - // If any remaining peers are preferred for eviction consider only them. - // This happens after the other preferences since if a peer is really the best by other criteria (esp relaying blocks) - // then we probably don't want to evict it no matter what. - if (std::any_of(vEvictionCandidates.begin(),vEvictionCandidates.end(),[](NodeEvictionCandidate const &n){return n.prefer_evict;})) { - vEvictionCandidates.erase(std::remove_if(vEvictionCandidates.begin(),vEvictionCandidates.end(), - [](NodeEvictionCandidate const &n){return !n.prefer_evict;}),vEvictionCandidates.end()); - } - - // Identify the network group with the most connections and youngest member. - // (vEvictionCandidates is already sorted by reverse connect time) - uint64_t naMostConnections; - unsigned int nMostConnections = 0; - std::chrono::seconds nMostConnectionsTime{0}; - std::map > mapNetGroupNodes; - for (const NodeEvictionCandidate &node : vEvictionCandidates) { - std::vector &group = mapNetGroupNodes[node.nKeyedNetGroup]; - group.push_back(node); - const auto grouptime{group[0].m_connected}; - - if (group.size() > nMostConnections || (group.size() == nMostConnections && grouptime > nMostConnectionsTime)) { - nMostConnections = group.size(); - nMostConnectionsTime = grouptime; - naMostConnections = node.nKeyedNetGroup; - } - } - - // Reduce to the network group with the most connections - vEvictionCandidates = std::move(mapNetGroupNodes[naMostConnections]); - - // Disconnect from the network group with the most connections - return vEvictionCandidates.front().id; -} - /** Try to find a connection to evict when the node is full. * Extreme care must be taken to avoid opening the node to attacker * triggered network partitioning. @@ -1304,10 +1081,6 @@ bool CConnman::AttemptToEvictConnection() LOCK(m_nodes_mutex); for (const CNode* node : m_nodes) { - if (node->HasPermission(NetPermissionFlags::NoBan)) - continue; - if (!node->IsInboundConn()) - continue; if (node->fDisconnect) continue; @@ -1343,6 +1116,8 @@ bool CConnman::AttemptToEvictConnection() Desig(prefer_evict) node->m_prefer_evict, Desig(m_is_local) node->addr.IsLocal(), Desig(m_network) node->ConnectedThroughNetwork(), + Desig(m_noban) node->HasPermission(NetPermissionFlags::NoBan), + Desig(m_conn_type) node->m_conn_type, }; vEvictionCandidates.push_back(candidate); } diff --git a/src/net.h b/src/net.h index 2cc3626170..7dae298373 100644 --- a/src/net.h +++ b/src/net.h @@ -19,6 +19,7 @@ #include #include #include +#include #include #include #include @@ -158,78 +159,6 @@ struct CSerializedNetMsg { size_t GetMemoryUsage() const noexcept; }; -/** Different types of connections to a peer. This enum encapsulates the - * information we have available at the time of opening or accepting the - * connection. Aside from INBOUND, all types are initiated by us. - * - * If adding or removing types, please update CONNECTION_TYPE_DOC in - * src/rpc/net.cpp and src/qt/rpcconsole.cpp, as well as the descriptions in - * src/qt/guiutil.cpp and src/bitcoin-cli.cpp::NetinfoRequestHandler. */ -enum class ConnectionType { - /** - * Inbound connections are those initiated by a peer. This is the only - * property we know at the time of connection, until P2P messages are - * exchanged. - */ - INBOUND, - - /** - * These are the default connections that we use to connect with the - * network. There is no restriction on what is relayed; by default we relay - * blocks, addresses & transactions. We automatically attempt to open - * MAX_OUTBOUND_FULL_RELAY_CONNECTIONS using addresses from our AddrMan. - */ - OUTBOUND_FULL_RELAY, - - - /** - * We open manual connections to addresses that users explicitly requested - * via the addnode RPC or the -addnode/-connect configuration options. Even if a - * manual connection is misbehaving, we do not automatically disconnect or - * add it to our discouragement filter. - */ - MANUAL, - - /** - * Feeler connections are short-lived connections made to check that a node - * is alive. They can be useful for: - * - test-before-evict: if one of the peers is considered for eviction from - * our AddrMan because another peer is mapped to the same slot in the tried table, - * evict only if this longer-known peer is offline. - * - move node addresses from New to Tried table, so that we have more - * connectable addresses in our AddrMan. - * Note that in the literature ("Eclipse Attacks on Bitcoin’s Peer-to-Peer Network") - * only the latter feature is referred to as "feeler connections", - * although in our codebase feeler connections encompass test-before-evict as well. - * We make these connections approximately every FEELER_INTERVAL: - * first we resolve previously found collisions if they exist (test-before-evict), - * otherwise we connect to a node from the new table. - */ - FEELER, - - /** - * We use block-relay-only connections to help prevent against partition - * attacks. By not relaying transactions or addresses, these connections - * are harder to detect by a third party, thus helping obfuscate the - * network topology. We automatically attempt to open - * MAX_BLOCK_RELAY_ONLY_ANCHORS using addresses from our anchors.dat. Then - * addresses from our AddrMan if MAX_BLOCK_RELAY_ONLY_CONNECTIONS - * isn't reached yet. - */ - BLOCK_RELAY, - - /** - * AddrFetch connections are short lived connections used to solicit - * addresses from peers. These are initiated to addresses submitted via the - * -seednode command line argument, or under certain conditions when the - * AddrMan is empty. - */ - ADDR_FETCH, -}; - -/** Convert ConnectionType enum to a string value */ -std::string ConnectionTypeAsString(ConnectionType conn_type); - /** * Look up IP addresses from all interfaces on the machine and add them to the * list of local addresses to self-advertise. @@ -1711,62 +1640,10 @@ extern std::function CaptureMessage; -struct NodeEvictionCandidate -{ - NodeId id; - std::chrono::seconds m_connected; - std::chrono::microseconds m_min_ping_time; - std::chrono::seconds m_last_block_time; - std::chrono::seconds m_last_tx_time; - bool fRelevantServices; - bool m_relay_txs; - bool fBloomFilter; - uint64_t nKeyedNetGroup; - bool prefer_evict; - bool m_is_local; - Network m_network; -}; - -/** - * Select an inbound peer to evict after filtering out (protecting) peers having - * distinct, difficult-to-forge characteristics. The protection logic picks out - * fixed numbers of desirable peers per various criteria, followed by (mostly) - * ratios of desirable or disadvantaged peers. If any eviction candidates - * remain, the selection logic chooses a peer to evict. - */ -[[nodiscard]] std::optional SelectNodeToEvict(std::vector&& vEvictionCandidates); - class CExplicitNetCleanup { public: static void callCleanup(); }; -extern RecursiveMutex cs_main; - -/** Protect desirable or disadvantaged inbound peers from eviction by ratio. - * - * This function protects half of the peers which have been connected the - * longest, to replicate the non-eviction implicit behavior and preclude attacks - * that start later. - * - * Half of these protected spots (1/4 of the total) are reserved for the - * following categories of peers, sorted by longest uptime, even if they're not - * longest uptime overall: - * - * - onion peers connected via our tor control service - * - * - localhost peers, as manually configured hidden services not using - * `-bind=addr[:port]=onion` will not be detected as inbound onion connections - * - * - I2P peers - * - * - CJDNS peers - * - * This helps protect these privacy network peers, which tend to be otherwise - * disadvantaged under our eviction criteria for their higher min ping times - * relative to IPv4/IPv6 peers, and favorise the diversity of peer connections. - */ -void ProtectEvictionCandidatesByRatio(std::vector& vEvictionCandidates); - #endif // BITCOIN_NET_H diff --git a/src/node/connection_types.cpp b/src/node/connection_types.cpp new file mode 100644 index 0000000000..904f4371aa --- /dev/null +++ b/src/node/connection_types.cpp @@ -0,0 +1,26 @@ +// Copyright (c) 2022 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 +#include + +std::string ConnectionTypeAsString(ConnectionType conn_type) +{ + switch (conn_type) { + case ConnectionType::INBOUND: + return "inbound"; + case ConnectionType::MANUAL: + return "manual"; + case ConnectionType::FEELER: + return "feeler"; + case ConnectionType::OUTBOUND_FULL_RELAY: + return "outbound-full-relay"; + case ConnectionType::BLOCK_RELAY: + return "block-relay-only"; + case ConnectionType::ADDR_FETCH: + return "addr-fetch"; + } // no default case, so the compiler can warn about missing cases + + assert(false); +} diff --git a/src/node/connection_types.h b/src/node/connection_types.h new file mode 100644 index 0000000000..5e1abcace6 --- /dev/null +++ b/src/node/connection_types.h @@ -0,0 +1,82 @@ +// Copyright (c) 2022 The Bitcoin Core developers +// Distributed under the MIT software license, see the accompanying +// file COPYING or http://www.opensource.org/licenses/mit-license.php. + +#ifndef BITCOIN_NODE_CONNECTION_TYPES_H +#define BITCOIN_NODE_CONNECTION_TYPES_H + +#include + +/** Different types of connections to a peer. This enum encapsulates the + * information we have available at the time of opening or accepting the + * connection. Aside from INBOUND, all types are initiated by us. + * + * If adding or removing types, please update CONNECTION_TYPE_DOC in + * src/rpc/net.cpp and src/qt/rpcconsole.cpp, as well as the descriptions in + * src/qt/guiutil.cpp and src/bitcoin-cli.cpp::NetinfoRequestHandler. */ +enum class ConnectionType { + /** + * Inbound connections are those initiated by a peer. This is the only + * property we know at the time of connection, until P2P messages are + * exchanged. + */ + INBOUND, + + /** + * These are the default connections that we use to connect with the + * network. There is no restriction on what is relayed; by default we relay + * blocks, addresses & transactions. We automatically attempt to open + * MAX_OUTBOUND_FULL_RELAY_CONNECTIONS using addresses from our AddrMan. + */ + OUTBOUND_FULL_RELAY, + + + /** + * We open manual connections to addresses that users explicitly requested + * via the addnode RPC or the -addnode/-connect configuration options. Even if a + * manual connection is misbehaving, we do not automatically disconnect or + * add it to our discouragement filter. + */ + MANUAL, + + /** + * Feeler connections are short-lived connections made to check that a node + * is alive. They can be useful for: + * - test-before-evict: if one of the peers is considered for eviction from + * our AddrMan because another peer is mapped to the same slot in the tried table, + * evict only if this longer-known peer is offline. + * - move node addresses from New to Tried table, so that we have more + * connectable addresses in our AddrMan. + * Note that in the literature ("Eclipse Attacks on Bitcoin’s Peer-to-Peer Network") + * only the latter feature is referred to as "feeler connections", + * although in our codebase feeler connections encompass test-before-evict as well. + * We make these connections approximately every FEELER_INTERVAL: + * first we resolve previously found collisions if they exist (test-before-evict), + * otherwise we connect to a node from the new table. + */ + FEELER, + + /** + * We use block-relay-only connections to help prevent against partition + * attacks. By not relaying transactions or addresses, these connections + * are harder to detect by a third party, thus helping obfuscate the + * network topology. We automatically attempt to open + * MAX_BLOCK_RELAY_ONLY_ANCHORS using addresses from our anchors.dat. Then + * addresses from our AddrMan if MAX_BLOCK_RELAY_ONLY_CONNECTIONS + * isn't reached yet. + */ + BLOCK_RELAY, + + /** + * AddrFetch connections are short lived connections used to solicit + * addresses from peers. These are initiated to addresses submitted via the + * -seednode command line argument, or under certain conditions when the + * AddrMan is empty. + */ + ADDR_FETCH, +}; + +/** Convert ConnectionType enum to a string value */ +std::string ConnectionTypeAsString(ConnectionType conn_type); + +#endif // BITCOIN_NODE_CONNECTION_TYPES_H diff --git a/src/node/eviction.cpp b/src/node/eviction.cpp new file mode 100644 index 0000000000..33406931d4 --- /dev/null +++ b/src/node/eviction.cpp @@ -0,0 +1,240 @@ +// Copyright (c) 2022 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 + +#include +#include +#include +#include +#include +#include +#include + + +static bool ReverseCompareNodeMinPingTime(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b) +{ + return a.m_min_ping_time > b.m_min_ping_time; +} + +static bool ReverseCompareNodeTimeConnected(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b) +{ + return a.m_connected > b.m_connected; +} + +static bool CompareNetGroupKeyed(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b) { + return a.nKeyedNetGroup < b.nKeyedNetGroup; +} + +static bool CompareNodeBlockTime(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b) +{ + // There is a fall-through here because it is common for a node to have many peers which have not yet relayed a block. + if (a.m_last_block_time != b.m_last_block_time) return a.m_last_block_time < b.m_last_block_time; + if (a.fRelevantServices != b.fRelevantServices) return b.fRelevantServices; + return a.m_connected > b.m_connected; +} + +static bool CompareNodeTXTime(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b) +{ + // There is a fall-through here because it is common for a node to have more than a few peers that have not yet relayed txn. + if (a.m_last_tx_time != b.m_last_tx_time) return a.m_last_tx_time < b.m_last_tx_time; + if (a.m_relay_txs != b.m_relay_txs) return b.m_relay_txs; + if (a.fBloomFilter != b.fBloomFilter) return a.fBloomFilter; + return a.m_connected > b.m_connected; +} + +// Pick out the potential block-relay only peers, and sort them by last block time. +static bool CompareNodeBlockRelayOnlyTime(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b) +{ + if (a.m_relay_txs != b.m_relay_txs) return a.m_relay_txs; + if (a.m_last_block_time != b.m_last_block_time) return a.m_last_block_time < b.m_last_block_time; + if (a.fRelevantServices != b.fRelevantServices) return b.fRelevantServices; + return a.m_connected > b.m_connected; +} + +/** + * Sort eviction candidates by network/localhost and connection uptime. + * Candidates near the beginning are more likely to be evicted, and those + * near the end are more likely to be protected, e.g. less likely to be evicted. + * - First, nodes that are not `is_local` and that do not belong to `network`, + * sorted by increasing uptime (from most recently connected to connected longer). + * - Then, nodes that are `is_local` or belong to `network`, sorted by increasing uptime. + */ +struct CompareNodeNetworkTime { + const bool m_is_local; + const Network m_network; + CompareNodeNetworkTime(bool is_local, Network network) : m_is_local(is_local), m_network(network) {} + bool operator()(const NodeEvictionCandidate& a, const NodeEvictionCandidate& b) const + { + if (m_is_local && a.m_is_local != b.m_is_local) return b.m_is_local; + if ((a.m_network == m_network) != (b.m_network == m_network)) return b.m_network == m_network; + return a.m_connected > b.m_connected; + }; +}; + +//! Sort an array by the specified comparator, then erase the last K elements where predicate is true. +template +static void EraseLastKElements( + std::vector& elements, Comparator comparator, size_t k, + std::function predicate = [](const NodeEvictionCandidate& n) { return true; }) +{ + std::sort(elements.begin(), elements.end(), comparator); + size_t eraseSize = std::min(k, elements.size()); + elements.erase(std::remove_if(elements.end() - eraseSize, elements.end(), predicate), elements.end()); +} + +void ProtectNoBanConnections(std::vector& eviction_candidates) +{ + eviction_candidates.erase(std::remove_if(eviction_candidates.begin(), eviction_candidates.end(), + [](NodeEvictionCandidate const& n) { + return n.m_noban; + }), + eviction_candidates.end()); +} + +void ProtectOutboundConnections(std::vector& eviction_candidates) +{ + eviction_candidates.erase(std::remove_if(eviction_candidates.begin(), eviction_candidates.end(), + [](NodeEvictionCandidate const& n) { + return n.m_conn_type != ConnectionType::INBOUND; + }), + eviction_candidates.end()); +} + +void ProtectEvictionCandidatesByRatio(std::vector& eviction_candidates) +{ + // Protect the half of the remaining nodes which have been connected the longest. + // This replicates the non-eviction implicit behavior, and precludes attacks that start later. + // To favorise the diversity of our peer connections, reserve up to half of these protected + // spots for Tor/onion, localhost, I2P, and CJDNS peers, even if they're not longest uptime + // overall. This helps protect these higher-latency peers that tend to be otherwise + // disadvantaged under our eviction criteria. + const size_t initial_size = eviction_candidates.size(); + const size_t total_protect_size{initial_size / 2}; + + // Disadvantaged networks to protect. In the case of equal counts, earlier array members + // have the first opportunity to recover unused slots from the previous iteration. + struct Net { bool is_local; Network id; size_t count; }; + std::array networks{ + {{false, NET_CJDNS, 0}, {false, NET_I2P, 0}, {/*localhost=*/true, NET_MAX, 0}, {false, NET_ONION, 0}}}; + + // Count and store the number of eviction candidates per network. + for (Net& n : networks) { + n.count = std::count_if(eviction_candidates.cbegin(), eviction_candidates.cend(), + [&n](const NodeEvictionCandidate& c) { + return n.is_local ? c.m_is_local : c.m_network == n.id; + }); + } + // Sort `networks` by ascending candidate count, to give networks having fewer candidates + // the first opportunity to recover unused protected slots from the previous iteration. + std::stable_sort(networks.begin(), networks.end(), [](Net a, Net b) { return a.count < b.count; }); + + // Protect up to 25% of the eviction candidates by disadvantaged network. + const size_t max_protect_by_network{total_protect_size / 2}; + size_t num_protected{0}; + + while (num_protected < max_protect_by_network) { + // Count the number of disadvantaged networks from which we have peers to protect. + auto num_networks = std::count_if(networks.begin(), networks.end(), [](const Net& n) { return n.count; }); + if (num_networks == 0) { + break; + } + const size_t disadvantaged_to_protect{max_protect_by_network - num_protected}; + const size_t protect_per_network{std::max(disadvantaged_to_protect / num_networks, static_cast(1))}; + // Early exit flag if there are no remaining candidates by disadvantaged network. + bool protected_at_least_one{false}; + + for (Net& n : networks) { + if (n.count == 0) continue; + const size_t before = eviction_candidates.size(); + EraseLastKElements(eviction_candidates, CompareNodeNetworkTime(n.is_local, n.id), + protect_per_network, [&n](const NodeEvictionCandidate& c) { + return n.is_local ? c.m_is_local : c.m_network == n.id; + }); + const size_t after = eviction_candidates.size(); + if (before > after) { + protected_at_least_one = true; + const size_t delta{before - after}; + num_protected += delta; + if (num_protected >= max_protect_by_network) { + break; + } + n.count -= delta; + } + } + if (!protected_at_least_one) { + break; + } + } + + // Calculate how many we removed, and update our total number of peers that + // we want to protect based on uptime accordingly. + assert(num_protected == initial_size - eviction_candidates.size()); + const size_t remaining_to_protect{total_protect_size - num_protected}; + EraseLastKElements(eviction_candidates, ReverseCompareNodeTimeConnected, remaining_to_protect); +} + +[[nodiscard]] std::optional SelectNodeToEvict(std::vector&& vEvictionCandidates) +{ + // Protect connections with certain characteristics + + ProtectNoBanConnections(vEvictionCandidates); + + ProtectOutboundConnections(vEvictionCandidates); + + // Deterministically select 4 peers to protect by netgroup. + // An attacker cannot predict which netgroups will be protected + EraseLastKElements(vEvictionCandidates, CompareNetGroupKeyed, 4); + // Protect the 8 nodes with the lowest minimum ping time. + // An attacker cannot manipulate this metric without physically moving nodes closer to the target. + EraseLastKElements(vEvictionCandidates, ReverseCompareNodeMinPingTime, 8); + // Protect 4 nodes that most recently sent us novel transactions accepted into our mempool. + // An attacker cannot manipulate this metric without performing useful work. + EraseLastKElements(vEvictionCandidates, CompareNodeTXTime, 4); + // Protect up to 8 non-tx-relay peers that have sent us novel blocks. + EraseLastKElements(vEvictionCandidates, CompareNodeBlockRelayOnlyTime, 8, + [](const NodeEvictionCandidate& n) { return !n.m_relay_txs && n.fRelevantServices; }); + + // Protect 4 nodes that most recently sent us novel blocks. + // An attacker cannot manipulate this metric without performing useful work. + EraseLastKElements(vEvictionCandidates, CompareNodeBlockTime, 4); + + // Protect some of the remaining eviction candidates by ratios of desirable + // or disadvantaged characteristics. + ProtectEvictionCandidatesByRatio(vEvictionCandidates); + + if (vEvictionCandidates.empty()) return std::nullopt; + + // If any remaining peers are preferred for eviction consider only them. + // This happens after the other preferences since if a peer is really the best by other criteria (esp relaying blocks) + // then we probably don't want to evict it no matter what. + if (std::any_of(vEvictionCandidates.begin(),vEvictionCandidates.end(),[](NodeEvictionCandidate const &n){return n.prefer_evict;})) { + vEvictionCandidates.erase(std::remove_if(vEvictionCandidates.begin(),vEvictionCandidates.end(), + [](NodeEvictionCandidate const &n){return !n.prefer_evict;}),vEvictionCandidates.end()); + } + + // Identify the network group with the most connections and youngest member. + // (vEvictionCandidates is already sorted by reverse connect time) + uint64_t naMostConnections; + unsigned int nMostConnections = 0; + std::chrono::seconds nMostConnectionsTime{0}; + std::map > mapNetGroupNodes; + for (const NodeEvictionCandidate &node : vEvictionCandidates) { + std::vector &group = mapNetGroupNodes[node.nKeyedNetGroup]; + group.push_back(node); + const auto grouptime{group[0].m_connected}; + + if (group.size() > nMostConnections || (group.size() == nMostConnections && grouptime > nMostConnectionsTime)) { + nMostConnections = group.size(); + nMostConnectionsTime = grouptime; + naMostConnections = node.nKeyedNetGroup; + } + } + + // Reduce to the network group with the most connections + vEvictionCandidates = std::move(mapNetGroupNodes[naMostConnections]); + + // Disconnect from the network group with the most connections + return vEvictionCandidates.front().id; +} diff --git a/src/node/eviction.h b/src/node/eviction.h new file mode 100644 index 0000000000..1bb32e5327 --- /dev/null +++ b/src/node/eviction.h @@ -0,0 +1,69 @@ +// Copyright (c) 2022 The Bitcoin Core developers +// Distributed under the MIT software license, see the accompanying +// file COPYING or http://www.opensource.org/licenses/mit-license.php. + +#ifndef BITCOIN_NODE_EVICTION_H +#define BITCOIN_NODE_EVICTION_H + +#include +#include + +#include +#include +#include +#include + +typedef int64_t NodeId; + +struct NodeEvictionCandidate { + NodeId id; + std::chrono::seconds m_connected; + std::chrono::microseconds m_min_ping_time; + std::chrono::seconds m_last_block_time; + std::chrono::seconds m_last_tx_time; + bool fRelevantServices; + bool m_relay_txs; + bool fBloomFilter; + uint64_t nKeyedNetGroup; + bool prefer_evict; + bool m_is_local; + Network m_network; + bool m_noban; + ConnectionType m_conn_type; +}; + +/** + * Select an inbound peer to evict after filtering out (protecting) peers having + * distinct, difficult-to-forge characteristics. The protection logic picks out + * fixed numbers of desirable peers per various criteria, followed by (mostly) + * ratios of desirable or disadvantaged peers. If any eviction candidates + * remain, the selection logic chooses a peer to evict. + */ +[[nodiscard]] std::optional SelectNodeToEvict(std::vector&& vEvictionCandidates); + +/** Protect desirable or disadvantaged inbound peers from eviction by ratio. + * + * This function protects half of the peers which have been connected the + * longest, to replicate the non-eviction implicit behavior and preclude attacks + * that start later. + * + * Half of these protected spots (1/4 of the total) are reserved for the + * following categories of peers, sorted by longest uptime, even if they're not + * longest uptime overall: + * + * - onion peers connected via our tor control service + * + * - localhost peers, as manually configured hidden services not using + * `-bind=addr[:port]=onion` will not be detected as inbound onion connections + * + * - I2P peers + * + * - CJDNS peers + * + * This helps protect these privacy network peers, which tend to be otherwise + * disadvantaged under our eviction criteria for their higher min ping times + * relative to IPv4/IPv6 peers, and favorise the diversity of peer connections. + */ +void ProtectEvictionCandidatesByRatio(std::vector& vEvictionCandidates); + +#endif // BITCOIN_NODE_EVICTION_H diff --git a/src/test/fuzz/node_eviction.cpp b/src/test/fuzz/node_eviction.cpp index 0835b399e0..1d6257e28c 100644 --- a/src/test/fuzz/node_eviction.cpp +++ b/src/test/fuzz/node_eviction.cpp @@ -32,6 +32,8 @@ FUZZ_TARGET(node_eviction) /* prefer_evict */ fuzzed_data_provider.ConsumeBool(), /* m_is_local */ fuzzed_data_provider.ConsumeBool(), /* m_network */ fuzzed_data_provider.PickValueInArray(ALL_NETWORKS), + /* m_noban */ fuzzed_data_provider.ConsumeBool(), + /* m_conn_type */ fuzzed_data_provider.PickValueInArray(ALL_CONNECTION_TYPES), }); } // Make a copy since eviction_candidates may be in some valid but otherwise diff --git a/src/test/util/net.cpp b/src/test/util/net.cpp index fc6a29d424..79dbc8ab9a 100644 --- a/src/test/util/net.cpp +++ b/src/test/util/net.cpp @@ -5,6 +5,7 @@ #include #include +#include #include #include #include @@ -128,6 +129,8 @@ std::vector GetRandomNodeEvictionCandidates(int n_candida /* prefer_evict */ random_context.randbool(), /* m_is_local */ random_context.randbool(), /* m_network */ ALL_NETWORKS[random_context.randrange(ALL_NETWORKS.size())], + /* m_noban */ false, + /* m_conn_type */ConnectionType::INBOUND, }); } return candidates; diff --git a/src/test/util/net.h b/src/test/util/net.h index dc758bd43e..7f203c6d55 100644 --- a/src/test/util/net.h +++ b/src/test/util/net.h @@ -6,6 +6,7 @@ #define BITCOIN_TEST_UTIL_NET_H #include +#include #include #include #include