Add some countermeasure to unwanted peers

README.md

@@ -8,6 +8,7 @@ You need to specify your AFL output directory with `--fuzzer-directory`, and you
 Some other options exist to let you fine-tune your *afl-transmit* experience, have a look at them via `--help`.
 
 On default, *afl-transmit* opens port 1337/TCP to wait for incoming connections. If you are not on a private net, make sure to protect this port with a firewall, or anyone on the internet may send you files (although this might become interesting).
+As a countermeasure, use the `--restrict-to-peers` flags to only allow connections from your known peers.
 
 ### Quickstart
 

net/listener.go

@@ -13,11 +13,13 @@ import (
 
 var (
 	port int
+	restrictToPeers bool
 )
 
 // Registers the flags required for the listener
 func RegisterListenFlags() {
 	flag.IntVar(&port, "port", ServerPort, "Port to bind server component to")
+	flag.BoolVar(&restrictToPeers, "restrict-to-peers", false, "Only allow connections from peers")
 }
 
 // Sets up a listener and listens forever for packets on the given port, storing their contents in the outputDirectory
@@ -40,9 +42,29 @@ func Listen(outputDirectory string) error {
 			log.Printf("Encountered error while accepting from %s: %s", conn.RemoteAddr().String(), connErr)
 			continue
 		}
+
+		// Check if we should restrict connections from peers
+		handleConnection := true
+		if restrictToPeers {
+			found := false
+			// Loop over peers
+			for _, p := range peers {
+				// Check if we found the remote address in our peers list
+				if p.Address == conn.RemoteAddr().String() {
+					found = true
+					break
+				}
+			}
+
+			// Handle connection only if its a peer
+			handleConnection = found
+		}
+
+		if handleConnection {
 			// Handle in a separate thread
 			go handle(conn, outputDirectory)
 		}
+	}
 }
 
 // Handles a single connection, and unpacks the received data into outputDirectory