Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
Config extractor for Jumplump malware family from the Knotweed report
#!/usr/bin/env python3
#
# Author: @jaydinbas
#
# Extract config from Knotweed Jumplump samples
# Note: Not all samples tagged as 'Jumplump' in the MS report
# contain a config, some just load other samples that do
#
# Works for
# cbae79f66f724e0fe1705d6b5db3cc8a4e89f6bdf4c37004aa1d45eeab26e84b
# 4611340fdade4e36f074f75294194b64dcf2ec0db00f3d958956b4b0d6586431
# fd6515a71530b8329e2c0104d0866c5c6f87546d4b44cc17bbb03e64663b11fc
# 7f84bf6a016ca15e654fb5ebc36fd7407cb32c69a0335a32bfc36cb91e36184d
# 5d169e083faa73f2920c8593fb95f599dad93d34a6aa2b0f794be978e44c8206
# 7f29b69eb1af1cc6c1998bad980640bfe779525fd5bb775bc36a0ce3789a8bfc
#
# Rest of the 'Jumplump' hashes are loaders
#
import capstone
import sys
import struct
import binascii
DEBUG = 0
def rc4crypt(data, key):
key = bytearray(key)
data = bytearray(data)
x = 0
box = bytearray([i for i in range(256)])
for i in range(256):
x = (x + box[i] + key[i % len(key)]) % 256
box[i], box[x] = box[x], box[i]
x,y = 0, 0
for (i,char) in enumerate(data):
x = (x + 1) % 256
y = (y + box[x]) % 256
box[x], box[y] = box[y], box[x]
data[i] ^= box[(box[x] + box[y]) % 256]
return bytes(data)
def parse_config(config):
print("Config:")
(unk1,unk2) = struct.unpack_from("<II",config)
print(" ",unk1) # ports prob
print(" ",unk2) #
strings = config[8:].split(b"\x00")
for s in strings:
print(" ",s.decode("ascii"))
def find_payload(data,p):
md = capstone.Cs(capstone.CS_ARCH_X86,capstone.CS_MODE_64)
md.detail = True
# Follow code until first jz
jz = None
for insn in md.disasm(data[p:],p):
if DEBUG:
print("%s %s" % (insn.mnemonic,insn.op_str))
if insn.mnemonic == "je":
jz = insn.operands[0].imm
break
if not jz:
if DEBUG:
print("jz not found")
return None
# then follow code flow until 1st call
payload = None
p = jz
for i in range(10): #max 10 instructions
insn = next(md.disasm(data[p:],p))
if insn.mnemonic == "jmp":
p = insn.operands[0].imm
elif insn.mnemonic == "call":
payload = p
break
else:
p += insn.size
if not payload:
return None
else:
payload += 5 # skip call
return payload
# call+5/pop rcx/sub rcx, 5
pic_pattern = b"\xE8\x00\x00\x00\x00\x59\x48\x83\xE9\x05"
data = open(sys.argv[1],"rb").read()
p = data.find(pic_pattern)
if p == -1:
print("[-] PIC not found")
sys.exit(0)
payload = find_payload(data,p)
if payload:
print("[+] Payload found @ %x" % payload)
else:
print("[-] Payload not found")
sys.exit(0)
rc4_key = data[payload:payload+16]
config_len_enc = data[payload+16:payload+16+4]
config_len = struct.unpack("<I",rc4crypt(config_len_enc,rc4_key))[0]
print("[+] RC4 key: %s" % binascii.hexlify(rc4_key))
print("[+] Config len: %d bytes" % config_len)
config_enc = data[payload+20:payload+20+config_len]
config = rc4crypt(config_enc,rc4_key)
parse_config(config)
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment