work on hw4 script

hw4/app.py

@@ -1,38 +1,60 @@
-from scapy.all import * #pull in all of scapy -- you could do it other ways, but this makes it isomorphic to using scapy command line
+from scapy.all import * 
 import socket
 import sys
 import time
+import hashlib
+
+def compute_checksums(file_path):
+    sha512_hash = hashlib.sha512()
+    md5_hash = hashlib.md5()
+    try:
+        with open(file_path, "rb") as f:
+            while chunk := f.read(8192):
+                sha512_hash.update(chunk)
+                md5_hash.update(chunk)
+    except FileNotFoundError:
+        print(f"Error: File not found - {file_path}")
+        return
+    sha512_digest = sha512_hash.hexdigest()
+    md5_digest = md5_hash.hexdigest()
+    print(f"MD5: {md5_digest}")
+    print(f"SHA-512: {sha512_digest}")
+
 
 def main():
-	if len(sys.argv) > 1: #if we have a command line argument
+	if len(sys.argv) > 1: 
 		try:
-			packets: PacketList = rdpcap(sys.argv[1])
+			bpf: str = 'tcp and src host 192.168.86.228 and src port 5000 and dst host 192.168.86.167'
-			#rdpcap is how we read a previously captured pcap file
+			#bpf  = 'host 192.168.86.167 or 192.168.86.228 and port 5000'
+			packets: PacketList = sniff(offline = sys.argv[1], filter=bpf, session = TCPSession)
 		except:
 			print("File read failure: %s not found" % sys.argv[1])
 			sys.exit(1)
 	else:
 		print("Need a pcap file to read!")
 		sys.exit(1)
-	#bpf = 'tcp and src host 192.168.86.228 and src port 80 and dst host 192.168.86.167'
+	raw_packets: PacketList = packets[Raw]
-	#filtered = packets.filter(bpf)
+	byte_accum: bytearray = bytearray(b'')
-	#print(packets) #this gives us a nice summary of what we have in the pcap file
+	count = 0
-
+	print("Total packets matching BPF: ",len(packets))
-	for p in packets[:5]: #let's only look at the first 100
+	print("Total raw packets matching BPF: ",len(raw_packets))
-		packet : Packet = p
+	for r in raw_packets:
-		#we can filter based on what scapy calls "layers"
+		raw_packet: Packet = r
-		#each layer is a portion of a packet
+		if b"Content-Type" in raw_packet[Raw].load:
-		#so a DNS packet would have an IP layer, a UDP layer, and a DNS layer
+			payload: bytes = raw_packet[Raw].load.split(b'\r\n')[-1]
-		#ICMP would be IP, TCP, ICMP layers
+			#print('Packet: ', raw_packet)
-		#and because we're on an ethernet network, all of the above also has an ether layer
+			#print("Packet Raw: ", raw_packet[Raw].load )
-		#let's not print DNS packets
+			#print()
-		#if not packet.haslayer(DNS):
+			#print('payload: ', payload)
-		# print(packet.summary)
+			#input()
-		lsc()
+			#print()
-		#packet.show() #print the contents of the packet
+			count += 1
-		#print(packet.summary()) #we also can print out a summary of the packet, similar to tcpdump default output
+			byte_accum = byte_accum + bytearray(payload) 
-		time.sleep(0.2) #small pause between packets
+	result_bytes: bytes = base64_bytes(bytes(byte_accum).decode('ascii'))	
-
+	file = open('download.bin','wb')
+	file.write(result_bytes)
+	print('done: ' ,count, ' packets decoded and packets written to download.bin')
+	compute_checksums('download.bin')
 
 if __name__ == '__main__':
 	main()

hw4/hw4.md

@@ -21,16 +21,13 @@ A starting point of a BPF might look like `tcp and src host 192.168.86.228 and s
 
 As a wireshark filter, this would be `tcp && ip.src == 192.168.86.228 && tcp.srcport == 5000 && ip.dst == 192.168.86.167`
 
-Before moving on to scapy, we can filter down our `firmware.pcap` to a new capture called `filtered.pcap` with the following command
+### Scapy
-
+I wrote a python scapy script will help us work with this capture file to assemble the .bin from the raw response of the relevant TCP packets. This script is shown in `./app.py`. Our script will confirm the extracted binary matches the following checksums
 ```
-tcpdump -r firmware.pcap -w filtered.pcap 'tcp and src host 192.168.86.228 and src port 5000 and dst host 192.168.86.167'
+MD5: 7aa6a7ebcbd98ce19539b668ff790655
-
+SHA256: 2a7719719aa4f869586a7043f532e01ed4985e5c25b9a54979ac7d50c67820ec61c2805d6169b9c95a98104b8fb1d4f9ec698d23881360e99f5232a4f3cf12d4 
 ```
 
-
-### 
-
 ## Questions
 1) What architecture is the firmware intended to run on?
 2) What OS is the firmware running?