67546802fe
Add an elliptic curve family for the twisted Edwards curves
Edwards25519 and Edwards448 ("Goldilocks"). As with Montgomery curves,
since these are the only two curves in common use, the family has a
generic name.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
138 lines
5.9 KiB
Python
138 lines
5.9 KiB
Python
"""Knowledge about cryptographic mechanisms implemented in Mbed TLS.
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This module is entirely based on the PSA API.
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"""
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# Copyright The Mbed TLS Contributors
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# SPDX-License-Identifier: Apache-2.0
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# 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, WITHOUT
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# 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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import re
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from typing import Iterable, Optional, Tuple
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from mbedtls_dev.asymmetric_key_data import ASYMMETRIC_KEY_DATA
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class KeyType:
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"""Knowledge about a PSA key type."""
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def __init__(self, name: str, params: Optional[Iterable[str]] = None):
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"""Analyze a key type.
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The key type must be specified in PSA syntax. In its simplest form,
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`name` is a string 'PSA_KEY_TYPE_xxx' which is the name of a PSA key
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type macro. For key types that take arguments, the arguments can
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be passed either through the optional argument `params` or by
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passing an expression of the form 'PSA_KEY_TYPE_xxx(param1, param2)'
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in `name` as a string.
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"""
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self.name = name.strip()
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"""The key type macro name (``PSA_KEY_TYPE_xxx``).
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For key types constructed from a macro with arguments, this is the
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name of the macro, and the arguments are in `self.params`.
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"""
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if params is None:
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if '(' in self.name:
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m = re.match(r'(\w+)\s*\((.*)\)\Z', self.name)
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assert m is not None
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self.name = m.group(1)
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params = ','.split(m.group(2))
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self.params = (None if params is None else
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[param.strip() for param in params])
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"""The parameters of the key type, if there are any.
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None if the key type is a macro without arguments.
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"""
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assert re.match(r'PSA_KEY_TYPE_\w+\Z', self.name)
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self.expression = self.name
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"""A C expression whose value is the key type encoding."""
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if self.params is not None:
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self.expression += '(' + ', '.join(self.params) + ')'
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self.private_type = re.sub(r'_PUBLIC_KEY\Z', r'_KEY_PAIR', self.name)
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"""The key type macro name for the corresponding key pair type.
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For everything other than a public key type, this is the same as
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`self.name`.
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"""
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ECC_KEY_SIZES = {
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'PSA_ECC_FAMILY_SECP_K1': (192, 224, 256),
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'PSA_ECC_FAMILY_SECP_R1': (225, 256, 384, 521),
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'PSA_ECC_FAMILY_SECP_R2': (160,),
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'PSA_ECC_FAMILY_SECT_K1': (163, 233, 239, 283, 409, 571),
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'PSA_ECC_FAMILY_SECT_R1': (163, 233, 283, 409, 571),
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'PSA_ECC_FAMILY_SECT_R2': (163,),
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'PSA_ECC_FAMILY_BRAINPOOL_P_R1': (160, 192, 224, 256, 320, 384, 512),
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'PSA_ECC_FAMILY_MONTGOMERY': (255, 448),
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'PSA_ECC_FAMILY_TWISTED_EDWARDS': (256, 448),
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}
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KEY_TYPE_SIZES = {
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'PSA_KEY_TYPE_AES': (128, 192, 256), # exhaustive
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'PSA_KEY_TYPE_ARC4': (8, 128, 2048), # extremes + sensible
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'PSA_KEY_TYPE_ARIA': (128, 192, 256), # exhaustive
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'PSA_KEY_TYPE_CAMELLIA': (128, 192, 256), # exhaustive
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'PSA_KEY_TYPE_CHACHA20': (256,), # exhaustive
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'PSA_KEY_TYPE_DERIVE': (120, 128), # sample
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'PSA_KEY_TYPE_DES': (64, 128, 192), # exhaustive
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'PSA_KEY_TYPE_HMAC': (128, 160, 224, 256, 384, 512), # standard size for each supported hash
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'PSA_KEY_TYPE_RAW_DATA': (8, 40, 128), # sample
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'PSA_KEY_TYPE_RSA_KEY_PAIR': (1024, 1536), # small sample
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}
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def sizes_to_test(self) -> Tuple[int, ...]:
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"""Return a tuple of key sizes to test.
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For key types that only allow a single size, or only a small set of
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sizes, these are all the possible sizes. For key types that allow a
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wide range of sizes, these are a representative sample of sizes,
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excluding large sizes for which a typical resource-constrained platform
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may run out of memory.
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"""
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if self.private_type == 'PSA_KEY_TYPE_ECC_KEY_PAIR':
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assert self.params is not None
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return self.ECC_KEY_SIZES[self.params[0]]
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return self.KEY_TYPE_SIZES[self.private_type]
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# "48657265006973206b6579a064617461"
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DATA_BLOCK = b'Here\000is key\240data'
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def key_material(self, bits: int) -> bytes:
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"""Return a byte string containing suitable key material with the given bit length.
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Use the PSA export representation. The resulting byte string is one that
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can be obtained with the following code:
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```
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psa_set_key_type(&attributes, `self.expression`);
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psa_set_key_bits(&attributes, `bits`);
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psa_set_key_usage_flags(&attributes, PSA_KEY_USAGE_EXPORT);
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psa_generate_key(&attributes, &id);
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psa_export_key(id, `material`, ...);
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```
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"""
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if self.expression in ASYMMETRIC_KEY_DATA:
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if bits not in ASYMMETRIC_KEY_DATA[self.expression]:
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raise ValueError('No key data for {}-bit {}'
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.format(bits, self.expression))
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return ASYMMETRIC_KEY_DATA[self.expression][bits]
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if bits % 8 != 0:
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raise ValueError('Non-integer number of bytes: {} bits for {}'
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.format(bits, self.expression))
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length = bits // 8
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if self.name == 'PSA_KEY_TYPE_DES':
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# "644573206b457901644573206b457902644573206b457904"
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des3 = b'dEs kEy\001dEs kEy\002dEs kEy\004'
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return des3[:length]
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return b''.join([self.DATA_BLOCK] * (length // len(self.DATA_BLOCK)) +
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[self.DATA_BLOCK[:length % len(self.DATA_BLOCK)]])
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