Limit message sizes before transfer

This introduces a fixed limit for the size of p2p messages, and enforces it
before download.

Rebased-From: ba04c4a7801e7d68a5e84035b919e5c3626eb7a7
Github-Pull: #5843

2 files changed, 7 insertions, 0 deletions

diff --git a/src/net.cpp b/src/net.cpp
index 97bb52cd3..b6ebf1cee 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -666,6 +666,11 @@ bool CNode::ReceiveMsgBytes(const char *pch, unsigned int nBytes)
         if (handled < 0)
                 return false;
 
+        if (msg.in_data && msg.hdr.nMessageSize > MAX_PROTOCOL_MESSAGE_LENGTH) {
+            LogPrint("net", "Oversized message from peer=%i, disconnecting", GetId());
+            return false;
+        }
+
         pch += handled;
         nBytes -= handled;
 
diff --git a/src/net.h b/src/net.h
index 210f7ca5c..6fc1a8ba6 100644
--- a/src/net.h
+++ b/src/net.h
@@ -43,6 +43,8 @@ static const int PING_INTERVAL = 2 * 60;
 static const int TIMEOUT_INTERVAL = 20 * 60;
 /** The maximum number of entries in an 'inv' protocol message */
 static const unsigned int MAX_INV_SZ = 50000;
+/** Maximum length of incoming protocol messages (no message over 2 MiB is currently acceptable). */
+static const unsigned int MAX_PROTOCOL_MESSAGE_LENGTH = 2 * 1024 * 1024;
 /** The maximum number of entries in mapAskFor */
 static const size_t MAPASKFOR_MAX_SZ = MAX_INV_SZ;