diff options
| -rw-r--r-- | src/net.cpp | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/src/net.cpp b/src/net.cpp index 7dec8fc1cf..ced371164a 100644 --- a/src/net.cpp +++ b/src/net.cpp @@ -877,6 +877,14 @@ public: } }; +/** 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. + * The strategy used here is to protect a small number of peers + * for each of several distinct characteristics which are difficult + * to forge. In order to partition a node the attacker must be + * simultaneously better at all of them than honest peers. + */ static bool AttemptToEvictConnection(bool fPreferNewConnection) { std::vector<CNodeRef> vEvictionCandidates; { @@ -905,7 +913,7 @@ static bool AttemptToEvictConnection(bool fPreferNewConnection) { if (vEvictionCandidates.empty()) return false; - // Protect the 8 nodes with the best ping times. + // Protect the 8 nodes with the lowest minimum ping time. // An attacker cannot manipulate this metric without physically moving nodes closer to the target. std::sort(vEvictionCandidates.begin(), vEvictionCandidates.end(), ReverseCompareNodeMinPingTime); vEvictionCandidates.erase(vEvictionCandidates.end() - std::min(8, static_cast<int>(vEvictionCandidates.size())), vEvictionCandidates.end()); @@ -913,7 +921,7 @@ static bool AttemptToEvictConnection(bool fPreferNewConnection) { if (vEvictionCandidates.empty()) return false; // Protect the half of the remaining nodes which have been connected the longest. - // This replicates the existing implicit behavior. + // This replicates the non-eviction implicit behavior, and precludes attacks that start later. std::sort(vEvictionCandidates.begin(), vEvictionCandidates.end(), ReverseCompareNodeTimeConnected); vEvictionCandidates.erase(vEvictionCandidates.end() - static_cast<int>(vEvictionCandidates.size() / 2), vEvictionCandidates.end()); @@ -941,6 +949,7 @@ static bool AttemptToEvictConnection(bool fPreferNewConnection) { vEvictionCandidates = mapAddrCounts[naMostConnections]; // Do not disconnect peers if there is only one unprotected connection from their network group. + // This step excessively favors netgroup diversity, and should be removed once more protective criteria are established. if (vEvictionCandidates.size() <= 1) // unless we prefer the new connection (for whitelisted peers) if (!fPreferNewConnection) |