Choose fuzzers to transmit based on the role of the node afl-transmit runs on

README.md

@@ -18,7 +18,7 @@ As a countermeasure, use the `--restrict-to-peers` flags to only allow connectio
 
 ### Quickstart
 
-- On your host 10.0.0.1: `./afl-transmit --fuzzer-directory /ram/output --peers 10.0.0.2,10.0.0.3`
-- On your host 10.0.0.2: `./afl-transmit --fuzzer-directory /ram/output --peers 10.0.0.1,10.0.0.3`
-- On your host 10.0.0.3: `./afl-transmit --fuzzer-directory /ram/output --peers 10.0.0.1,10.0.0.2`
+- On your host 10.0.0.1: `./afl-transmit --fuzzer-directory /ram/output --main --peers 10.0.0.2,10.0.0.3`
+- On your host 10.0.0.2: `./afl-transmit --fuzzer-directory /ram/output --peers 10.0.0.1`
+- On your host 10.0.0.3: `./afl-transmit --fuzzer-directory /ram/output --peers 10.0.0.1`
 

watchdog/watchdog.go

@@ -14,21 +14,21 @@ import (
 
 var (
 	rescanSecs int
+	isMainNode bool
 )
 
 // Register flags
 func RegisterWatchdogFlags() {
 	flag.IntVar(&rescanSecs, "rescan-secs", 30, "Seconds to wait before rescanning local fuzzer directories")
+	flag.BoolVar(&isMainNode, "main", false, "Set this option if this afl-transmit instance is running on the node running the main afl-fuzz instance")
 }
 
 // Watch over the specified directory, send updates to peers and re-scan after the specified amount of seconds
 func WatchFuzzers(outputDirectory string) {
 	// Loop forever
 	for {
-		localFuzzers := detectLocalFuzzers(outputDirectory)
-		
-		// Loop over local fuzzers
-		for _, localFuzzDir := range localFuzzers {
+		// Loop over those fuzzer directories we want to share
+		for _, localFuzzDir := range getTargetFuzzers(outputDirectory) {
 			// Pack important parts of the fuzzer directory into a byte array
 			fuzzerName := filepath.Base(localFuzzDir)
 			packedFuzzer, packerErr := logistic.PackFuzzer(fuzzerName, localFuzzDir)
@@ -46,8 +46,51 @@ func WatchFuzzers(outputDirectory string) {
 	}
 }
 
-// Searches in the specified output directory for fuzzers which run locally. This is done by searching for a file which is not shared between fuzzers as it is not required for clusterized fuzzing: 'cmdline'.
-func detectLocalFuzzers(outputDirectory string) []string {
+// Searches in the specified output directory for fuzzers which we want to pack.
+// Identifying the main fuzzer is done by searching for the file "is_main_node"
+// Identifying local secondary fuzzers is done by searching for a file which is not shared between nodes as it is not required for clusterized fuzzing: 'cmdline'.
+// Please note that this is not failsafe, e.g. if you already synced your fuzzers over a different tool or by hand before.
+//
+// - If we are running in main mode (--main), we want to share the main fuzzers' queue with the secondary nodes
+// - If we are not running in main mode, we want to share all of our fuzzers' queues with the main node
+//
+// (see AFLplusplus/src/afl-fuzz.run.c:542)
+func getTargetFuzzers(outputDirectory string) []string {
+	if isMainNode {
+		// find main fuzzer directory - its the only one required by the secondaries
+
+		// List files (read: fuzzers) in output directory
+		filesInDir, readErr := ioutil.ReadDir(outputDirectory)
+		if readErr != nil {
+			log.Printf("Failed to list directory content of %s: %s", outputDirectory, readErr)
+			return nil
+		}
+
+		for _, f := range filesInDir {
+			// Get stat for maybe-existent file
+			mainnodePath := fmt.Sprintf("%s%c%s%cis_main_node", outputDirectory, os.PathSeparator, f.Name(), os.PathSeparator)
+			_, statErr := os.Stat(mainnodePath)
+			if os.IsNotExist(statErr) {
+				// File does not exist. Not the ~~chosen one~~ main fuzzer. Next.
+				continue
+			} else if statErr != nil {
+				// An error occurred. File is maybe in a Schrödinger state.
+				log.Printf("Unable to stat file %s: %s", mainnodePath, statErr)
+				continue
+			}
+
+			// is_main_node file exists, so we found the correct fuzzer directory - return it
+			fullPath := fmt.Sprintf("%s%c%s", outputDirectory, os.PathSeparator, f.Name())
+			return []string{
+				fullPath,
+			}
+		}
+
+		// Failed to find the main node - probably we are in --main mode by accident
+		log.Printf("Unable to find main node in %s - sure afl-transmit should run in --main mode?", outputDirectory)
+		return nil
+	} else {
+		// get all fuzzer directories which are locally available
 		var localFuzzers []string
 
 		// List files (read: fuzzers) in output directory
@@ -57,7 +100,7 @@ func detectLocalFuzzers(outputDirectory string) []string {
 			return nil
 		}
 
-	// Walk over each and search for 'cmdline' file
+		// Walk over each fuzzer and search for 'cmdline' file
 		for _, f := range filesInDir {
 			// Get stat for maybe-existent file
 			cmdlinePath := fmt.Sprintf("%s%c%s%ccmdline", outputDirectory, os.PathSeparator, f.Name(), os.PathSeparator)
@@ -78,3 +121,4 @@ func detectLocalFuzzers(outputDirectory string) []string {
 
 		return localFuzzers
 	}
+}