95 lines
3.6 KiB
Python
95 lines
3.6 KiB
Python
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# Copyright 2017 Linaro Limited
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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Cryptographic key management for imgtool.
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"""
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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.rsa import (
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RSAPrivateKey, RSAPublicKey)
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from cryptography.hazmat.primitives.asymmetric.ec import (
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EllipticCurvePrivateKey, EllipticCurvePublicKey)
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from cryptography.hazmat.primitives.asymmetric.ed25519 import (
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Ed25519PrivateKey, Ed25519PublicKey)
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from cryptography.hazmat.primitives.asymmetric.x25519 import (
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X25519PrivateKey, X25519PublicKey)
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from .rsa import RSA, RSAPublic, RSAUsageError, RSA_KEY_SIZES
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from .ecdsa import ECDSA256P1, ECDSA256P1Public, ECDSAUsageError
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from .ed25519 import Ed25519, Ed25519Public, Ed25519UsageError
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from .x25519 import X25519, X25519Public, X25519UsageError
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class PasswordRequired(Exception):
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"""Raised to indicate that the key is password protected, but a
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password was not specified."""
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pass
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def load(path, passwd=None):
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"""Try loading a key from the given path. Returns None if the password wasn't specified."""
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with open(path, 'rb') as f:
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raw_pem = f.read()
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try:
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pk = serialization.load_pem_private_key(
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raw_pem,
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password=passwd,
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backend=default_backend())
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# Unfortunately, the crypto library raises unhelpful exceptions,
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# so we have to look at the text.
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except TypeError as e:
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msg = str(e)
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if "private key is encrypted" in msg:
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return None
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raise e
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except ValueError:
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# This seems to happen if the key is a public key, let's try
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# loading it as a public key.
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pk = serialization.load_pem_public_key(
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raw_pem,
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backend=default_backend())
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if isinstance(pk, RSAPrivateKey):
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if pk.key_size not in RSA_KEY_SIZES:
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raise Exception("Unsupported RSA key size: " + pk.key_size)
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return RSA(pk)
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elif isinstance(pk, RSAPublicKey):
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if pk.key_size not in RSA_KEY_SIZES:
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raise Exception("Unsupported RSA key size: " + pk.key_size)
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return RSAPublic(pk)
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elif isinstance(pk, EllipticCurvePrivateKey):
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if pk.curve.name != 'secp256r1':
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raise Exception("Unsupported EC curve: " + pk.curve.name)
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if pk.key_size != 256:
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raise Exception("Unsupported EC size: " + pk.key_size)
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return ECDSA256P1(pk)
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elif isinstance(pk, EllipticCurvePublicKey):
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if pk.curve.name != 'secp256r1':
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raise Exception("Unsupported EC curve: " + pk.curve.name)
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if pk.key_size != 256:
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raise Exception("Unsupported EC size: " + pk.key_size)
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return ECDSA256P1Public(pk)
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elif isinstance(pk, Ed25519PrivateKey):
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return Ed25519(pk)
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elif isinstance(pk, Ed25519PublicKey):
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return Ed25519Public(pk)
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elif isinstance(pk, X25519PrivateKey):
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return X25519(pk)
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elif isinstance(pk, X25519PublicKey):
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return X25519Public(pk)
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else:
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raise Exception("Unknown key type: " + str(type(pk)))
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