Ignore getaddr messages on Outbound connections.

[novacoin.git] / src / main.cpp

diff --git a/src/main.cpp b/src/main.cpp
index 9ff24e4..b3c3504 100644 (file)
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -3619,7 +3619,12 @@ 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))
     {
         // Don't return addresses older than nCutOff timestamp
         int64_t nCutOff = GetTime() - (nNodeLifespan * nOneDay);