cloudflare/filterforgeИнструмент для разбора BPF-фильтров и создания пакетов на их основе.
Python-набор инструментов для обратной разработки байт-кода Berkeley Packet Filter (BPF). Имея на входе сырые инструкции BPF — такие, какие можно извлечь из образца вредоносного ПО, фильтра захвата пакетов или сетевого устройства — filterforge дизассемблирует их в человекочитаемый вид, использует Z3 для нахождения набора ограничений на пакет, удовлетворяющих принимающему пути, а затем применяет Scapy для создания конкретного сетевого пакета, который прошёл бы через фильтр.
Проще говоря: передайте ему программу BPF, и он вернёт вам полностью сформированный пакет (Ethernet, IPv4/IPv6, TCP/UDP/SCTP и т.д.), который фильтр принимает — готовый к просмотру, сохранению в PCAP или отправке по сети.
Для запуска этого инструмента рекомендуется установить uv.
Пожалуйста, обратитесь к приведённым ниже примерам использования инструмента; со временем, скорее всего, будет добавлено больше функций.
Чтобы быстро получить результат для заданного BPF, проще всего использовать командную строку. Поскольку некоторые инструменты обратной разработки возвращают скопированные данные, вы можете передать как сырую шестнадцатеричную строку, так и массив шестнадцатеричных значений, используя флаг -d для простого показа дизассемблирования переданного BPF;
# шестнадцатеричная строка
uv run ff -d -b "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"
# массив шестнадцатеричных значений
uv run ff -d -b "[0x28,0x0,0x0,0xc,0x15,0x0,0x1b,0x800,0x30,0x0,0x0,0x17,0x15,0x0,0x5,0x11,0x28,0x0,0x0,0x14,0x45,0x17,0x0,0x1fff,0xb1,0x0,0x0,0xe,0x48,0x0,0x0,0x16,0x15,0x13,0x14,0x7255,0x15,0x0,0x7,0x1,0x28,0x0,0x0,0x14,0x45,0x11,0x0,0x1fff,0xb1,0x0,0x0,0xe,0x48,0x0,0x0,0x16,0x15,0x0,0xe,0x7255,0x50,0x0,0x0,0xe,0x15,0xb,0xc,0x8,0x15,0x0,0xb,0x6,0x28,0x0,0x0,0x14,0x45,0x9,0x0,0x1fff,0xb1,0x0,0x0,0xe,0x50,0x0,0x0,0x1a,0x54,0x0,0x0,0xf0,0x74,0x0,0x0,0x2,0xc,0x0,0x0,0x0,0x7,0x0,0x0,0x0,0x48,0x0,0x0,0xe,0x15,0x0,0x1,0x5293,0x6,0x0,0x0,0xffff,0x6,0x0,0x0,0x0]"
Чтобы получить обзор того, как будет выглядеть сетевой пакет, созданный из заданного байт-кода BPF, используйте флаг -c:
uv run ff -c -b "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"
2026-02-09 12:06:23,342 - INFO - Loaded 45 instructions
2026-02-09 12:06:23,342 - DEBUG - Found 50 accepting path(s)
2026-02-09 12:06:23,346 - DEBUG - Path 1 is satisfiable
2026-02-09 12:06:23,347 - INFO - Hexdump:
0000 00 00 00 00 00 00 00 00 00 00 00 00 86 DD 60 00 ..............`.
0010 00 00 00 00 84 00 00 00 00 00 00 00 00 00 00 00 ................
0020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0030 00 00 00 00 00 00 D5 FA 00 00 00 00 00 00 00 00 ................
0040 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0050 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0060 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0070 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
2026-02-09 12:06:23,347 - INFO - Packet summary:
###[ Ethernet ]###
dst = 00:00:00:00:00:00
src = 00:00:00:00:00:00
type = IPv6
###[ IPv6 ]###
version = 6
tc = 0
fl = 0
plen = 0
nh = SCTP
hlim = 0
src = ::
dst = ::
###[ SCTP ]###
sport = 54778
dport = 0
tag = 0x0
chksum = 0x0
###[ Raw ]###
load = b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
Некоторые BPF могут использовать сырой IP-уровень; для этого можно указать тип канала -l raw (по умолчанию используется ethernet);
uv run ff -c -b 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 -l raw
2026-02-09 12:06:46,064 - INFO - Loaded 229 instructions
2026-02-09 12:06:46,717 - DEBUG - Found 50 accepting path(s)
2026-02-09 12:06:46,725 - DEBUG - Path 1 unsatisfiable
2026-02-09 12:06:46,730 - DEBUG - Path 2 is satisfiable
2026-02-09 12:06:46,731 - INFO - Hexdump:
0000 45 00 00 00 00 00 00 00 00 11 00 00 00 00 00 00 E...............
0010 00 00 00 00 00 00 00 00 00 00 00 00 72 55 00 00 ............rU..
0020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0040 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0050 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0060 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0070 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
2026-02-09 12:06:46,731 - INFO - Packet summary:
###[ IP ]###
version = 4
ihl = 5
tos = 0x0
len = 0
id = 0
flags =
frag = 0
ttl = 0
proto = udp
chksum = 0x0
src = 0.0.0.0
dst = 0.0.0.0
\options \
###[ UDP ]###
sport = 0
dport = 0
len = 0
chksum = 0x0
###[ Raw ]###
load = b'rU\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
Для использования инструмента в более программном стиле мы создали относительно простой в использовании API, который можно реализовать множеством различных способов; обратитесь к некоторым примерам ниже для вдохновения:
from ff import BPFSolver
# Create a solver with BPF bytecode
solver = BPFSolver("280000000c00000015001b00...")
# Solve and craft a packet
result = solver.solve()
if result:
result.hexdump()
result.show()
print(result.summary())
from ff import BPFSolver
solver = BPFSolver("280000000c00000015001b00...")
# Get human-readable disassembly
print(solver.disassemble())
# Access parsed instructions
print(f"Instruction count: {solver.instruction_count}")
for insn in solver.instructions:
print(insn)
from ff import BPFSolver, PacketOverrides
solver = BPFSolver("280000000c00000015001b00...")
# Override specific packet fields
overrides = PacketOverrides(
src_ip="192.168.1.100",
dst_ip="10.0.0.1",
src_port=12345,
dst_port=80,
src_mac="00:11:22:33:44:55",
dst_mac="aa:bb:cc:dd:ee:ff"
)
result = solver.solve(overrides=overrides)
if result:
result.show()
from ff import BPFSolver
solver = BPFSolver("280000000c00000015001b00...")
result = solver.solve()
if result:
# Save to PCAP file
solver.to_pcap("output.pcap")
# Or save a specific result
solver.to_pcap("output.pcap", result=result)
from ff import BPFSolver
# Use link_type="raw" for DLT_RAW (no Ethernet header)
solver = BPFSolver("280000000c00000015001b00...", link_type="raw")
result = solver.solve()
from ff import BPFSolver
solver = BPFSolver("280000000c00000015001b00...")
# Find all paths that lead to packet acceptance
paths = solver.find_paths()
print(f"Found {len(paths)} accepting path(s)")
for i, path in enumerate(paths):
print(f"Path {i+1}: {path}")
from ff import BPFSolver
solver = BPFSolver("280000000c00000015001b00...")
result = solver.solve()
if result:
# Raw bytes
raw_bytes = result.raw
# Scapy packet object for advanced manipulation
scapy_pkt = result.scapy_packet
scapy_pkt[0].dst = "192.168.1.1" # Modify directly
# Execution path taken
print(f"Path: {result.path}")
print(f"Link type: {result.link_type}")
from ff import BPFSolver
solver = BPFSolver("280000000c00000015001b00...")
result = solver.solve()
if result:
# Send packet (requires root/sudo)
solver.send(iface="eth0", count=1)
# Or send a specific result
solver.send(result=result, iface="eth0")
Иногда в BPF отсутствуют две ожидаемые инструкции ret (одна для принятия пакета, одна для отбрасывания). Возьмём, к примеру, этот образец Symbiote (dcfbd5054bb6ea61b8f5a352a482e0cf7e8c5545bd88915d3e67f7ba01c2b3d4):
uv run ff -d -b "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"
2026-02-09 12:08:32,009 - INFO - Loaded 44 instructions
(000) ldh [12]
(001) jeq #0x86dd, jt 2, jf 17
(002) ldb [20]
<SNIPPED>
(026) jeq #0xd5fa, jt 43, jf 27
(027) jeq #0xe5f6, jt 43, jf 28
(028) jeq #0xe912, jt 43, jf 29
(029) jeq #0xd65f, jt 43, jf 30
(030) jeq #0xe283, jt 43, jf 31
(031) jeq #0xfb42, jt 43, jf 32
(032) jeq #0xb26d, jt 43, jf 33
(033) jeq #0xf6fb, jt 43, jf 34
(034) ldh [x + 16]
(035) jeq #0xd5fa, jt 43, jf 36
(036) jeq #0xe5f6, jt 43, jf 37
(037) jeq #0xe912, jt 43, jf 38
(038) jeq #0xd65f, jt 43, jf 39
(039) jeq #0xe283, jt 43, jf 40
(040) jeq #0xfb42, jt 43, jf 41
(041) jeq #0xb26d, jt 43, jf 42
(042) jeq #0xf6fb, jt 43, jf 44
(043) ret #0 (DROP)
Мы видим, что здесь присутствует только одна из ожидаемых инструкций ret, из-за чего наш решатель Z3 терпит неудачу;
2025-12-16 12:09:31,123 - ERROR - No satisfiable paths found, failed to craft packet
Мы можем добавить свою собственную инструкцию с успешным переходом, посмотрев на то, что делает BPF. В приведённом выше фрагменте видно множество условий, связанных с номерами портов, каждое из которых либо проверяет следующее условие, либо переходит к инструкции 43, обозначенной нами как DROP из-за того, как мы дизассемблируем BPF. В данном случае это не точный DROP, а корректный оператор возврата. Это означает, что если мы добавим свою собственную фиктивную инструкцию ret успеха, она будет правильно разобрана, например:
ret: 06 00 00 00 00 00 00 0006 00 00 00 ff ff 00 00 06 00 00 00 00 00 00 00В результате:
uv run ff -d -b "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"
2025-12-16 12:12:04,346 - INFO - Loaded 45 instructions
(000) ldh [12]
(001) jeq #0x86dd, jt 2, jf 17
(002) ldb [20]
<SNIPPED>
(026) jeq #0xd5fa, jt 43, jf 27
(027) jeq #0xe5f6, jt 43, jf 28
(028) jeq #0xe912, jt 43, jf 29
(029) jeq #0xd65f, jt 43, jf 30
(030) jeq #0xe283, jt 43, jf 31
(031) jeq #0xfb42, jt 43, jf 32
(032) jeq #0xb26d, jt 43, jf 33
(033) jeq #0xf6fb, jt 43, jf 34
(034) ldh [x + 16]
(035) jeq #0xd5fa, jt 43, jf 36
(036) jeq #0xe5f6, jt 43, jf 37
(037) jeq #0xe912, jt 43, jf 38
(038) jeq #0xd65f, jt 43, jf 39
(039) jeq #0xe283, jt 43, jf 40
(040) jeq #0xfb42, jt 43, jf 41
(041) jeq #0xb26d, jt 43, jf 42
(042) jeq #0xf6fb, jt 43, jf 44
(043) ret #0xffff (ACCEPT)
(044) ret #0 (DROP)
Если теперь запустить -c для создания пакета, нас встретит свежий магический пакет:
uv run ff -c -b "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"
2026-02-09 12:07:47,247 - INFO - Loaded 45 instructions
2026-02-09 12:07:47,247 - DEBUG - Found 50 accepting path(s)
2026-02-09 12:07:47,251 - DEBUG - Path 1 is satisfiable
2026-02-09 12:07:47,251 - INFO - Hexdump:
0000 00 00 00 00 00 00 00 00 00 00 00 00 86 DD 60 00 ..............`.
0010 00 00 00 00 84 00 00 00 00 00 00 00 00 00 00 00 ................
0020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0030 00 00 00 00 00 00 D5 FA 00 00 00 00 00 00 00 00 ................
0040 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0050 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0060 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0070 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
2026-02-09 12:07:47,252 - INFO - Packet summary:
###[ Ethernet ]###
dst = 00:00:00:00:00:00
src = 00:00:00:00:00:00
type = IPv6
###[ IPv6 ]###
version = 6
tc = 0
fl = 0
plen = 0
nh = SCTP
hlim = 0
src = ::
dst = ::
###[ SCTP ]###
sport = 54778
dport = 0
tag = 0x0
chksum = 0x0
###[ Raw ]###
load = b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
Для запуска тестов локально:
uv run --extra dev pytest tests/ -v