Randomize message processing peer order

sipa · sipa · commit 79c02c88b347 · 2021-06-02T13:55:14.000-07:00
diff --git a/src/net.cpp b/src/net.cpp
@@ -2173,6 +2173,7 @@ void CConnman::OpenNetworkConnection(const CAddress& addrConnect, bool fCountFai
 
 void CConnman::ThreadMessageHandler()
 {
+    FastRandomContext rng;
     while (!flagInterruptMsgProc)
     {
         std::vector<CNode*> vNodesCopy;
@@ -2186,6 +2187,11 @@ void CConnman::ThreadMessageHandler()
 
         bool fMoreWork = false;
 
+        // Randomize the order in which we process messages from/to our peers.
+        // This prevents attacks in which an attacker exploits having multiple
+        // consecutive connections in the vNodes list.
+        Shuffle(vNodesCopy.begin(), vNodesCopy.end(), rng);
+
         for (CNode* pnode : vNodesCopy)
         {
             if (pnode->fDisconnect)

Original file line number	Diff line number	Diff line change
`@@ -2173,6 +2173,7 @@ void CConnman::OpenNetworkConnection(const CAddress& addrConnect, bool fCountFai`
`2173`	`2173`
`2174`	`2174`	`void CConnman::ThreadMessageHandler()`
`2175`	`2175`	`{`
	`2176`	`+ FastRandomContext rng;`
`2176`	`2177`	`while (!flagInterruptMsgProc)`
`2177`	`2178`	`{`
`2178`	`2179`	`std::vector<CNode*> vNodesCopy;`
`@@ -2186,6 +2187,11 @@ void CConnman::ThreadMessageHandler()`
`2186`	`2187`
`2187`	`2188`	`bool fMoreWork = false;`
`2188`	`2189`
	`2190`	`+ // Randomize the order in which we process messages from/to our peers.`
	`2191`	`+ // This prevents attacks in which an attacker exploits having multiple`
	`2192`	`+ // consecutive connections in the vNodes list.`
	`2193`	`+ Shuffle(vNodesCopy.begin(), vNodesCopy.end(), rng);`
	`2194`	`+`
`2189`	`2195`	`for (CNode* pnode : vNodesCopy)`
`2190`	`2196`	`{`
`2191`	`2197`	`if (pnode->fDisconnect)`