120 lines
3.4 KiB
Python
120 lines
3.4 KiB
Python
"""
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X25519 key management
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"""
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# SPDX-License-Identifier: Apache-2.0
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from cryptography.hazmat.backends import default_backend
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from cryptography.hazmat.primitives import serialization
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from cryptography.hazmat.primitives.asymmetric import x25519
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from .general import KeyClass
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from .privatebytes import PrivateBytesMixin
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class X25519UsageError(Exception):
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pass
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class X25519Public(KeyClass):
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def __init__(self, key):
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self.key = key
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def shortname(self):
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return "x25519"
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def _unsupported(self, name):
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raise X25519UsageError("Operation {} requires private key".format(name))
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def _get_public(self):
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return self.key
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def get_public_bytes(self):
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# The key is embedded into MBUboot in "SubjectPublicKeyInfo" format
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return self._get_public().public_bytes(
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encoding=serialization.Encoding.DER,
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format=serialization.PublicFormat.SubjectPublicKeyInfo)
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def get_public_pem(self):
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return self._get_public().public_bytes(
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encoding=serialization.Encoding.PEM,
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format=serialization.PublicFormat.SubjectPublicKeyInfo)
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def get_private_bytes(self, minimal, format):
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self._unsupported('get_private_bytes')
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def export_private(self, path, passwd=None):
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self._unsupported('export_private')
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def export_public(self, path):
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"""Write the public key to the given file."""
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pem = self._get_public().public_bytes(
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encoding=serialization.Encoding.PEM,
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format=serialization.PublicFormat.SubjectPublicKeyInfo)
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with open(path, 'wb') as f:
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f.write(pem)
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def sig_type(self):
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return "X25519"
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def sig_tlv(self):
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return "X25519"
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def sig_len(self):
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return 32
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class X25519(X25519Public, PrivateBytesMixin):
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"""
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Wrapper around an X25519 private key.
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"""
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def __init__(self, key):
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"""key should be an instance of EllipticCurvePrivateKey"""
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self.key = key
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@staticmethod
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def generate():
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pk = x25519.X25519PrivateKey.generate()
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return X25519(pk)
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def _get_public(self):
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return self.key.public_key()
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_VALID_FORMATS = {
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'pkcs8': serialization.PrivateFormat.PKCS8
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}
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_DEFAULT_FORMAT = 'pkcs8'
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def get_private_bytes(self, minimal, format):
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_, priv = self._get_private_bytes(minimal, format,
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X25519UsageError)
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return priv
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def export_private(self, path, passwd=None):
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"""
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Write the private key to the given file, protecting it with the
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optional password.
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"""
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if passwd is None:
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enc = serialization.NoEncryption()
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else:
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enc = serialization.BestAvailableEncryption(passwd)
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pem = self.key.private_bytes(
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encoding=serialization.Encoding.PEM,
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format=serialization.PrivateFormat.PKCS8,
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encryption_algorithm=enc)
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with open(path, 'wb') as f:
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f.write(pem)
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def sign_digest(self, digest):
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"""Return the actual signature"""
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return self.key.sign(data=digest)
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def verify_digest(self, signature, digest):
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"""Verify that signature is valid for given digest"""
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k = self.key
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if isinstance(self.key, x25519.X25519PrivateKey):
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k = self.key.public_key()
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return k.verify(signature=signature, data=digest)
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