Merge pull request #5442

dca799e Ignore getaddr messages on Outbound connections. (Ivan Pustogarov)

1 files changed, 6 insertions, 1 deletions

diff --git a/src/main.cpp b/src/main.cpp
index fdbcfa52fa..a2043dd9cb 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -4021,7 +4021,12 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
     }
 
 
-    else if (strCommand == "getaddr")
+    // This asymmetric behavior for inbound and outbound connections was introduced
+    // to prevent a fingerprinting attack: an attacker can send specific fake addresses
+    // to users' AddrMan and later request them by sending getaddr messages. 
+    // Making users (which are behind NAT and can only make outgoing connections) ignore 
+    // getaddr message mitigates the attack.
+    else if ((strCommand == "getaddr") && (pfrom->fInbound))
     {
         pfrom->vAddrToSend.clear();
         vector<CAddress> vAddr = addrman.GetAddr();