33 lines
1.2 KiB
Python
33 lines
1.2 KiB
Python
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import base64, typing
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from cryptography.hazmat.primitives import hashes, serialization
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from cryptography.hazmat.primitives.asymmetric import padding, rsa
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from cryptography.hazmat.backends import default_backend
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SIGNATURE_FORMAT = (
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"keyId=\"%s\",headers=\"%s\",signature=\"%s\",algorithm=\"rsa-sha256\"")
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def private_key(key_filename: str) -> rsa.RSAPrivateKey:
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with open(key_filename) as key_file:
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return serialization.load_pem_private_key(
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key_file.read(), password=None, backend=default_backend())
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def signature(key: rsa.RSAPrivateKey, key_id: str,
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headers: typing.List[typing.Tuple[str, str]]) -> str:
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private_key = _private_key(key_filename)
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sign_header_keys = " ".join(h[0] for h in headers)
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sign_string_parts = ["%s: %s" % (k, v) for k, v in headers]
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sign_string = "\n".join(sign_string_parts)
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signature = private_key.sign(
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sign_string.encode("utf8"),
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padding.PSS(
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mgf=padding.MGF1(hashes.SHA256()),
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salt_length=padding.PSS.MAX_LENGTH),
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hashes.SHA256()
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)
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signature = base64.b64encode(signature).decode("ascii")
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return SIGNATURE_FORMAT % (key_id, sign_header_keys, signature)
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