69 lines
2.3 KiB
Python
69 lines
2.3 KiB
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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import wave
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import struct
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import zlib
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import numpy as np
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SR = 44100
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SKIP_SEC = 1.0
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STEP = 2
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IN_WAV = "some_secret.wav"
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def read_wav_int16(path: str):
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with wave.open(path, "rb") as wf:
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assert wf.getnchannels() == 2
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assert wf.getsampwidth() == 2
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sr = wf.getframerate()
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frames = wf.readframes(wf.getnframes())
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arr = np.frombuffer(frames, dtype=np.int16).reshape(-1, 2)
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return sr, arr
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def bits_to_bytes_big_endian(bits: np.ndarray) -> bytes:
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# Длина должна быть кратна 8
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n = (bits.size + 7) // 8 * 8
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if n != bits.size:
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bits = np.pad(bits, (0, n - bits.size), constant_values=0)
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by = np.packbits(bits.astype(np.uint8), bitorder='big').tobytes()
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return by
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def extract_header_and_length(right: np.ndarray, sr: int):
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skip = int(sr * SKIP_SEC)
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# Считываем первые 12 байт (заголовок: 4 + 4 + 4)
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header_bits_count = 12 * 8
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idxs = skip + np.arange(header_bits_count) * STEP
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bits = (right[idxs] & 1).astype(np.uint8)
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header = bits_to_bytes_big_endian(bits)
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magic = header[:4]
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if magic != b"STAG":
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raise ValueError("Магия заголовка не совпала — это не тот контейнер.")
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length = struct.unpack(">I", header[4:8])[0]
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crc = struct.unpack(">I", header[8:12])[0]
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return length, crc
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def extract_all(sr: int, stereo: np.ndarray):
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right = stereo[:, 1]
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length, crc_expected = extract_header_and_length(right, sr)
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total_bytes = 12 + length
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total_bits = total_bytes * 8
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skip = int(sr * SKIP_SEC)
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idxs = skip + np.arange(total_bits) * STEP
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bits = (right[idxs] & 1).astype(np.uint8)
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data = bits_to_bytes_big_endian(bits)
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header = data[:12]
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payload = data[12:12+length]
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crc_actual = zlib.crc32(payload) & 0xFFFFFFFF
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if crc_actual != crc_expected:
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raise ValueError("CRC не сошлась — данные повреждены или неверные параметры извлечения.")
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flag = zlib.decompress(payload).decode("utf-8")
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return flag
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def main():
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sr, stereo = read_wav_int16(IN_WAV)
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flag = extract_all(sr, stereo)
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print("[+] DATA [ ", flag, " ]")
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if __name__ == "__main__":
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main()
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