"""Knowledge about cryptographic mechanisms implemented in Mbed TLS. This module is entirely based on the PSA API. """ # Copyright The Mbed TLS Contributors # SPDX-License-Identifier: Apache-2.0 # # Licensed under the Apache License, Version 2.0 (the "License"); you may # not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. import re from typing import Dict, Iterable, Optional, Pattern, Tuple from mbedtls_dev.asymmetric_key_data import ASYMMETRIC_KEY_DATA class KeyType: """Knowledge about a PSA key type.""" def __init__(self, name: str, params: Optional[Iterable[str]] = None): """Analyze a key type. The key type must be specified in PSA syntax. In its simplest form, `name` is a string 'PSA_KEY_TYPE_xxx' which is the name of a PSA key type macro. For key types that take arguments, the arguments can be passed either through the optional argument `params` or by passing an expression of the form 'PSA_KEY_TYPE_xxx(param1, ...)' in `name` as a string. """ self.name = name.strip() """The key type macro name (``PSA_KEY_TYPE_xxx``). For key types constructed from a macro with arguments, this is the name of the macro, and the arguments are in `self.params`. """ if params is None: if '(' in self.name: m = re.match(r'(\w+)\s*\((.*)\)\Z', self.name) assert m is not None self.name = m.group(1) params = m.group(2).split(',') self.params = (None if params is None else [param.strip() for param in params]) """The parameters of the key type, if there are any. None if the key type is a macro without arguments. """ assert re.match(r'PSA_KEY_TYPE_\w+\Z', self.name) self.expression = self.name """A C expression whose value is the key type encoding.""" if self.params is not None: self.expression += '(' + ', '.join(self.params) + ')' self.private_type = re.sub(r'_PUBLIC_KEY\Z', r'_KEY_PAIR', self.name) """The key type macro name for the corresponding key pair type. For everything other than a public key type, this is the same as `self.name`. """ ECC_KEY_SIZES = { 'PSA_ECC_FAMILY_SECP_K1': (192, 224, 256), 'PSA_ECC_FAMILY_SECP_R1': (225, 256, 384, 521), 'PSA_ECC_FAMILY_SECP_R2': (160,), 'PSA_ECC_FAMILY_SECT_K1': (163, 233, 239, 283, 409, 571), 'PSA_ECC_FAMILY_SECT_R1': (163, 233, 283, 409, 571), 'PSA_ECC_FAMILY_SECT_R2': (163,), 'PSA_ECC_FAMILY_BRAINPOOL_P_R1': (160, 192, 224, 256, 320, 384, 512), 'PSA_ECC_FAMILY_MONTGOMERY': (255, 448), 'PSA_ECC_FAMILY_TWISTED_EDWARDS': (255, 448), } KEY_TYPE_SIZES = { 'PSA_KEY_TYPE_AES': (128, 192, 256), # exhaustive 'PSA_KEY_TYPE_ARC4': (8, 128, 2048), # extremes + sensible 'PSA_KEY_TYPE_ARIA': (128, 192, 256), # exhaustive 'PSA_KEY_TYPE_CAMELLIA': (128, 192, 256), # exhaustive 'PSA_KEY_TYPE_CHACHA20': (256,), # exhaustive 'PSA_KEY_TYPE_DERIVE': (120, 128), # sample 'PSA_KEY_TYPE_DES': (64, 128, 192), # exhaustive 'PSA_KEY_TYPE_HMAC': (128, 160, 224, 256, 384, 512), # standard size for each supported hash 'PSA_KEY_TYPE_RAW_DATA': (8, 40, 128), # sample 'PSA_KEY_TYPE_RSA_KEY_PAIR': (1024, 1536), # small sample } def sizes_to_test(self) -> Tuple[int, ...]: """Return a tuple of key sizes to test. For key types that only allow a single size, or only a small set of sizes, these are all the possible sizes. For key types that allow a wide range of sizes, these are a representative sample of sizes, excluding large sizes for which a typical resource-constrained platform may run out of memory. """ if self.private_type == 'PSA_KEY_TYPE_ECC_KEY_PAIR': assert self.params is not None return self.ECC_KEY_SIZES[self.params[0]] return self.KEY_TYPE_SIZES[self.private_type] # "48657265006973206b6579a064617461" DATA_BLOCK = b'Here\000is key\240data' def key_material(self, bits: int) -> bytes: """Return a byte string containing suitable key material with the given bit length. Use the PSA export representation. The resulting byte string is one that can be obtained with the following code: ``` psa_set_key_type(&attributes, `self.expression`); psa_set_key_bits(&attributes, `bits`); psa_set_key_usage_flags(&attributes, PSA_KEY_USAGE_EXPORT); psa_generate_key(&attributes, &id); psa_export_key(id, `material`, ...); ``` """ if self.expression in ASYMMETRIC_KEY_DATA: if bits not in ASYMMETRIC_KEY_DATA[self.expression]: raise ValueError('No key data for {}-bit {}' .format(bits, self.expression)) return ASYMMETRIC_KEY_DATA[self.expression][bits] if bits % 8 != 0: raise ValueError('Non-integer number of bytes: {} bits for {}' .format(bits, self.expression)) length = bits // 8 if self.name == 'PSA_KEY_TYPE_DES': # "644573206b457901644573206b457902644573206b457904" des3 = b'dEs kEy\001dEs kEy\002dEs kEy\004' return des3[:length] return b''.join([self.DATA_BLOCK] * (length // len(self.DATA_BLOCK)) + [self.DATA_BLOCK[:length % len(self.DATA_BLOCK)]]) KEY_TYPE_FOR_SIGNATURE = { 'PSA_KEY_USAGE_SIGN_HASH': re.compile('.*KEY_PAIR'), 'PSA_KEY_USAGE_VERIFY_HASH': re.compile('.*KEY.*') } #type: Dict[str, Pattern] """Use a regexp to determine key types for which signature is possible when using the actual usage flag. """ def is_valid_for_signature(self, usage: str) -> bool: """Determine if the key type is compatible with the specified signitute type. """ # This is just temporaly solution for the implicit usage flags. return re.match(self.KEY_TYPE_FOR_SIGNATURE[usage], self.name) is not None