File size: 4,072 Bytes
387c3d6 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 | import struct
import numpy as np
# ================= 配置 =================
INPUT_FILE = "beacon_chips.bin"
# 802.11b Barker Code (11 chips)
BARKER_SEQ = np.array([1, 0, 1, 1, 0, 1, 1, 1, 0, 0, 0], dtype=int)
def correlate_and_despread(chips):
if len(chips) % 11 != 0:
print(f"[Warning] Chip count {len(chips)} is not a multiple of 11. Truncating.")
chips = chips[:-(len(chips) % 11)]
n_bits = len(chips) // 11
decoded_bits = []
for i in range(n_bits):
chunk = chips[i * 11: (i + 1) * 11]
xor_sum = np.sum(chunk ^ BARKER_SEQ)
if xor_sum < 2:
decoded_bits.append(0)
elif xor_sum > 9:
decoded_bits.append(1)
else:
decoded_bits.append(0)
return decoded_bits
def diff_decode(bits):
decoded = []
prev = 0
for curr in bits:
val = curr ^ prev
decoded.append(val)
prev = curr
return decoded
def descrambler(bits):
state = [1, 0, 1, 1, 1, 0, 1]
out_bits = []
for b in bits:
feedback = state[6] ^ state[3]
state = [feedback] + state[:-1]
out_bits.append(b ^ feedback)
return out_bits
def bits_to_bytes(bits):
bytes_data = bytearray()
for i in range(0, len(bits), 8):
byte_chunk = bits[i:i + 8]
if len(byte_chunk) < 8:
break
val = 0
for idx, bit in enumerate(byte_chunk):
val |= (bit << idx)
bytes_data.append(val)
return bytes_data
def verify():
print(f"[*] Reading {INPUT_FILE}...")
try:
with open(INPUT_FILE, 'rb') as f:
chips = np.frombuffer(f.read(), dtype=np.uint8)
except FileNotFoundError:
print(f"[Error] File not found.")
return
print(f"[*] Total Chips: {len(chips)}")
# 1. 解扩频
raw_bits = correlate_and_despread(chips)
# 2. 解差分
diff_decoded = diff_decode(raw_bits)
# 3. 解扰码
descrambled = descrambler(diff_decoded)
# 4. 寻找 SFD
sfd_pattern = [1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1]
start_idx = -1
for i in range(len(descrambled) - 16):
if descrambled[i: i + 16] == sfd_pattern:
start_idx = i + 16
print(f"[+] Found SFD at bit index: {i}")
break
if start_idx == -1:
print("[-] SFD not found!")
return
# 5. 提取 Payload
payload_bits = descrambled[start_idx:]
payload_bytes = bits_to_bytes(payload_bits)
plcp_header = payload_bytes[:6]
psdu = payload_bytes[6:] # 这里是完整的 MAC Frame (Header + Body + FCS)
print(f"[+] PLCP Header: {plcp_header.hex()} (Signal: {plcp_header[0]:02x})")
print(f"[+] PSDU (MAC Frame): {psdu.hex()}")
# ================= 解析 SSID =================
print("\n--- Parsing Beacon Info ---")
# Beacon Frame 结构:
# 24 bytes: MAC Header
# 12 bytes: Fixed Parameters (Timestamp, Interval, Cap)
# Variable: Tags
offset_to_tags = 24 + 12
if len(psdu) < offset_to_tags:
print("[!] MAC Frame too short.")
return
# 跳过 MAC Header 和 Fixed Parameters，直接定位到 Tags
tagged_params = psdu[offset_to_tags:]
current_idx = 0
found_ssid = False
while current_idx < len(tagged_params):
if current_idx + 2 > len(tagged_params):
break
tag_id = tagged_params[current_idx]
tag_len = tagged_params[current_idx + 1]
if current_idx + 2 + tag_len > len(tagged_params):
print("[!] Malformed Tag length.")
break
tag_data = tagged_params[current_idx + 2: current_idx + 2 + tag_len]
if tag_id == 0: # SSID Tag
ssid_str = tag_data.decode('utf-8', errors='replace')
print(f"\n[SUCCESS] PARSED SSID: '{ssid_str}'")
print(f" (Tag Length: {tag_len})")
found_ssid = True
break
current_idx += 2 + tag_len
if not found_ssid:
print("\n[FAIL] SSID Tag not found.")
if __name__ == "__main__":
verify() |