42 lines
1.5 KiB
Python
42 lines
1.5 KiB
Python
#!/usr/bin/env python3
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"""Sign a firmware binary with ECDSA P-256. Outputs a raw 64-byte r||s .sig file."""
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import argparse
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from pathlib import Path
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from cryptography.hazmat.primitives.asymmetric import ec
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from cryptography.hazmat.primitives import hashes, serialization
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from cryptography.hazmat.primitives.asymmetric.utils import decode_dss_signature
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def load_private_key(key_path: Path) -> ec.EllipticCurvePrivateKey:
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return serialization.load_pem_private_key(key_path.read_bytes(), password=None)
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def sign_firmware(firmware_path: Path, key_path: Path) -> bytes:
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key = load_private_key(key_path)
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data = firmware_path.read_bytes()
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sig_der = key.sign(data, ec.ECDSA(hashes.SHA256()))
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r, s = decode_dss_signature(sig_der)
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return r.to_bytes(32, 'big') + s.to_bytes(32, 'big')
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def main() -> None:
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p = argparse.ArgumentParser(description=__doc__)
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p.add_argument("firmware", help="Path to firmware .bin")
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p.add_argument("--key", default="secrets/firmware_signing_key.pem",
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help="Path to PEM private key")
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p.add_argument("--out", help="Output .sig path (default: firmware.bin.sig)")
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args = p.parse_args()
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firmware = Path(args.firmware)
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key_path = Path(args.key)
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out_path = Path(args.out) if args.out else firmware.with_suffix(".bin.sig")
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sig = sign_firmware(firmware, key_path)
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out_path.write_bytes(sig)
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print(f"Signed {firmware.name} → {out_path} ({len(sig)} bytes)")
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if __name__ == "__main__":
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main()
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