tests/scripts/generate_psa_tests.py

#!/usr/bin/env python3
"""Generate test data for PSA cryptographic mechanisms.

With no arguments, generate all test data. With non-option arguments,
generate only the specified files.
"""

# 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 enum
import re
import sys
from typing import Callable, Dict, FrozenSet, Iterable, Iterator, List, Optional

import scripts_path # pylint: disable=unused-import
from mbedtls_dev import crypto_knowledge
from mbedtls_dev import macro_collector
from mbedtls_dev import psa_storage
from mbedtls_dev import test_case
from mbedtls_dev import test_data_generation


def psa_want_symbol(name: str) -> str:
    """Return the PSA_WANT_xxx symbol associated with a PSA crypto feature."""
    if name.startswith('PSA_'):
        return name[:4] + 'WANT_' + name[4:]
    else:
        raise ValueError('Unable to determine the PSA_WANT_ symbol for ' + name)

def finish_family_dependency(dep: str, bits: int) -> str:
    """Finish dep if it's a family dependency symbol prefix.

    A family dependency symbol prefix is a PSA_WANT_ symbol that needs to be
    qualified by the key size. If dep is such a symbol, finish it by adjusting
    the prefix and appending the key size. Other symbols are left unchanged.
    """
    return re.sub(r'_FAMILY_(.*)', r'_\1_' + str(bits), dep)

def finish_family_dependencies(dependencies: List[str], bits: int) -> List[str]:
    """Finish any family dependency symbol prefixes.

    Apply `finish_family_dependency` to each element of `dependencies`.
    """
    return [finish_family_dependency(dep, bits) for dep in dependencies]

SYMBOLS_WITHOUT_DEPENDENCY = frozenset([
    'PSA_ALG_AEAD_WITH_AT_LEAST_THIS_LENGTH_TAG', # modifier, only in policies
    'PSA_ALG_AEAD_WITH_SHORTENED_TAG', # modifier
    'PSA_ALG_ANY_HASH', # only in policies
    'PSA_ALG_AT_LEAST_THIS_LENGTH_MAC', # modifier, only in policies
    'PSA_ALG_KEY_AGREEMENT', # chaining
    'PSA_ALG_TRUNCATED_MAC', # modifier
])
def automatic_dependencies(*expressions: str) -> List[str]:
    """Infer dependencies of a test case by looking for PSA_xxx symbols.

    The arguments are strings which should be C expressions. Do not use
    string literals or comments as this function is not smart enough to
    skip them.
    """
    used = set()
    for expr in expressions:
        used.update(re.findall(r'PSA_(?:ALG|ECC_FAMILY|KEY_TYPE)_\w+', expr))
    used.difference_update(SYMBOLS_WITHOUT_DEPENDENCY)
    return sorted(psa_want_symbol(name) for name in used)

# Define set of regular expressions and dependencies to optionally append
# extra dependencies for test case.
AES_128BIT_ONLY_DEP_REGEX = r'AES\s(192|256)'
AES_128BIT_ONLY_DEP = ["!MBEDTLS_AES_ONLY_128_BIT_KEY_LENGTH"]

DEPENDENCY_FROM_KEY = {
    AES_128BIT_ONLY_DEP_REGEX: AES_128BIT_ONLY_DEP
}#type: Dict[str, List[str]]
def generate_key_dependencies(description: str) -> List[str]:
    """Return additional dependencies based on pairs of REGEX and dependencies.
    """
    deps = []
    for regex, dep in DEPENDENCY_FROM_KEY.items():
        if re.search(regex, description):
            deps += dep

    return deps

# A temporary hack: at the time of writing, not all dependency symbols
# are implemented yet. Skip test cases for which the dependency symbols are
# not available. Once all dependency symbols are available, this hack must
# be removed so that a bug in the dependency symbols properly leads to a test
# failure.
def read_implemented_dependencies(filename: str) -> FrozenSet[str]:
    return frozenset(symbol
                     for line in open(filename)
                     for symbol in re.findall(r'\bPSA_WANT_\w+\b', line))
_implemented_dependencies = None #type: Optional[FrozenSet[str]] #pylint: disable=invalid-name
def hack_dependencies_not_implemented(dependencies: List[str]) -> None:
    global _implemented_dependencies #pylint: disable=global-statement,invalid-name
    if _implemented_dependencies is None:
        _implemented_dependencies = \
            read_implemented_dependencies('include/psa/crypto_config.h')
    if not all((dep.lstrip('!') in _implemented_dependencies or
                not dep.lstrip('!').startswith('PSA_WANT'))
               for dep in dependencies):
        dependencies.append('DEPENDENCY_NOT_IMPLEMENTED_YET')

def tweak_key_pair_dependency(dep: str, usage: str):
    """
    This helper function add the proper suffix to PSA_WANT_KEY_TYPE_xxx_KEY_PAIR
    symbols according to the required usage.
    """
    ret_list = list()
    if dep.endswith('KEY_PAIR'):
        if usage == "BASIC":
            # BASIC automatically includes IMPORT and EXPORT for test purposes (see
            # config_psa.h).
            ret_list.append(re.sub(r'KEY_PAIR', r'KEY_PAIR_BASIC', dep))
            ret_list.append(re.sub(r'KEY_PAIR', r'KEY_PAIR_IMPORT', dep))
            ret_list.append(re.sub(r'KEY_PAIR', r'KEY_PAIR_EXPORT', dep))
        elif usage == "GENERATE":
            ret_list.append(re.sub(r'KEY_PAIR', r'KEY_PAIR_GENERATE', dep))
    else:
        # No replacement to do in this case
        ret_list.append(dep)
    return ret_list

def fix_key_pair_dependencies(dep_list: List[str], usage: str):
    new_list = [new_deps
                for dep in dep_list
                for new_deps in tweak_key_pair_dependency(dep, usage)]

    return new_list

class Information:
    """Gather information about PSA constructors."""

    def __init__(self) -> None:
        self.constructors = self.read_psa_interface()

    @staticmethod
    def remove_unwanted_macros(
            constructors: macro_collector.PSAMacroEnumerator
    ) -> None:
        # Mbed TLS does not support finite-field DSA.
        # Don't attempt to generate any related test case.
        constructors.key_types.discard('PSA_KEY_TYPE_DSA_KEY_PAIR')
        constructors.key_types.discard('PSA_KEY_TYPE_DSA_PUBLIC_KEY')

    def read_psa_interface(self) -> macro_collector.PSAMacroEnumerator:
        """Return the list of known key types, algorithms, etc."""
        constructors = macro_collector.InputsForTest()
        header_file_names = ['include/psa/crypto_values.h',
                             'include/psa/crypto_extra.h']
        test_suites = ['tests/suites/test_suite_psa_crypto_metadata.data']
        for header_file_name in header_file_names:
            constructors.parse_header(header_file_name)
        for test_cases in test_suites:
            constructors.parse_test_cases(test_cases)
        self.remove_unwanted_macros(constructors)
        constructors.gather_arguments()
        return constructors


def test_case_for_key_type_not_supported(
        verb: str, key_type: str, bits: int,
        dependencies: List[str],
        *args: str,
        param_descr: str = ''
) -> test_case.TestCase:
    """Return one test case exercising a key creation method
    for an unsupported key type or size.
    """
    hack_dependencies_not_implemented(dependencies)
    tc = test_case.TestCase()
    short_key_type = crypto_knowledge.short_expression(key_type)
    adverb = 'not' if dependencies else 'never'
    if param_descr:
        adverb = param_descr + ' ' + adverb
    tc.set_description('PSA {} {} {}-bit {} supported'
                       .format(verb, short_key_type, bits, adverb))
    tc.set_dependencies(dependencies)
    tc.set_function(verb + '_not_supported')
    tc.set_arguments([key_type] + list(args))
    return tc

class KeyTypeNotSupported:
    """Generate test cases for when a key type is not supported."""

    def __init__(self, info: Information) -> None:
        self.constructors = info.constructors

    ALWAYS_SUPPORTED = frozenset([
        'PSA_KEY_TYPE_DERIVE',
        'PSA_KEY_TYPE_PASSWORD',
        'PSA_KEY_TYPE_PASSWORD_HASH',
        'PSA_KEY_TYPE_RAW_DATA',
        'PSA_KEY_TYPE_HMAC'
    ])
    def test_cases_for_key_type_not_supported(
            self,
            kt: crypto_knowledge.KeyType,
            param: Optional[int] = None,
            param_descr: str = '',
    ) -> Iterator[test_case.TestCase]:
        """Return test cases exercising key creation when the given type is unsupported.

        If param is present and not None, emit test cases conditioned on this
        parameter not being supported. If it is absent or None, emit test cases
        conditioned on the base type not being supported.
        """
        if kt.name in self.ALWAYS_SUPPORTED:
            # Don't generate test cases for key types that are always supported.
            # They would be skipped in all configurations, which is noise.
            return
        import_dependencies = [('!' if param is None else '') +
                               psa_want_symbol(kt.name)]
        if kt.params is not None:
            import_dependencies += [('!' if param == i else '') +
                                    psa_want_symbol(sym)
                                    for i, sym in enumerate(kt.params)]
        if kt.name.endswith('_PUBLIC_KEY'):
            generate_dependencies = []
        else:
            generate_dependencies = fix_key_pair_dependencies(import_dependencies, 'GENERATE')
            import_dependencies = fix_key_pair_dependencies(import_dependencies, 'BASIC')
        for bits in kt.sizes_to_test():
            yield test_case_for_key_type_not_supported(
                'import', kt.expression, bits,
                finish_family_dependencies(import_dependencies, bits),
                test_case.hex_string(kt.key_material(bits)),
                param_descr=param_descr,
            )
            if not generate_dependencies and param is not None:
                # If generation is impossible for this key type, rather than
                # supported or not depending on implementation capabilities,
                # only generate the test case once.
                continue
                # For public key we expect that key generation fails with
                # INVALID_ARGUMENT. It is handled by KeyGenerate class.
            if not kt.is_public():
                yield test_case_for_key_type_not_supported(
                    'generate', kt.expression, bits,
                    finish_family_dependencies(generate_dependencies, bits),
                    str(bits),
                    param_descr=param_descr,
                )
            # To be added: derive

    ECC_KEY_TYPES = ('PSA_KEY_TYPE_ECC_KEY_PAIR',
                     'PSA_KEY_TYPE_ECC_PUBLIC_KEY')
    DH_KEY_TYPES = ('PSA_KEY_TYPE_DH_KEY_PAIR',
                    'PSA_KEY_TYPE_DH_PUBLIC_KEY')

    def test_cases_for_not_supported(self) -> Iterator[test_case.TestCase]:
        """Generate test cases that exercise the creation of keys of unsupported types."""
        for key_type in sorted(self.constructors.key_types):
            if key_type in self.ECC_KEY_TYPES:
                continue
            if key_type in self.DH_KEY_TYPES:
                continue
            kt = crypto_knowledge.KeyType(key_type)
            yield from self.test_cases_for_key_type_not_supported(kt)
        for curve_family in sorted(self.constructors.ecc_curves):
            for constr in self.ECC_KEY_TYPES:
                kt = crypto_knowledge.KeyType(constr, [curve_family])
                yield from self.test_cases_for_key_type_not_supported(
                    kt, param_descr='type')
                yield from self.test_cases_for_key_type_not_supported(
                    kt, 0, param_descr='curve')
        for dh_family in sorted(self.constructors.dh_groups):
            for constr in self.DH_KEY_TYPES:
                kt = crypto_knowledge.KeyType(constr, [dh_family])
                yield from self.test_cases_for_key_type_not_supported(
                    kt, param_descr='type')
                yield from self.test_cases_for_key_type_not_supported(
                    kt, 0, param_descr='group')

def test_case_for_key_generation(
        key_type: str, bits: int,
        dependencies: List[str],
        *args: str,
        result: str = ''
) -> test_case.TestCase:
    """Return one test case exercising a key generation.
    """
    hack_dependencies_not_implemented(dependencies)
    tc = test_case.TestCase()
    short_key_type = crypto_knowledge.short_expression(key_type)
    tc.set_description('PSA {} {}-bit'
                       .format(short_key_type, bits))
    tc.set_dependencies(dependencies)
    tc.set_function('generate_key')
    tc.set_arguments([key_type] + list(args) + [result])

    return tc

class KeyGenerate:
    """Generate positive and negative (invalid argument) test cases for key generation."""

    def __init__(self, info: Information) -> None:
        self.constructors = info.constructors

    ECC_KEY_TYPES = ('PSA_KEY_TYPE_ECC_KEY_PAIR',
                     'PSA_KEY_TYPE_ECC_PUBLIC_KEY')
    DH_KEY_TYPES = ('PSA_KEY_TYPE_DH_KEY_PAIR',
                    'PSA_KEY_TYPE_DH_PUBLIC_KEY')

    @staticmethod
    def test_cases_for_key_type_key_generation(
            kt: crypto_knowledge.KeyType
    ) -> Iterator[test_case.TestCase]:
        """Return test cases exercising key generation.

        All key types can be generated except for public keys. For public key
        PSA_ERROR_INVALID_ARGUMENT status is expected.
        """
        result = 'PSA_SUCCESS'

        import_dependencies = [psa_want_symbol(kt.name)]
        if kt.params is not None:
            import_dependencies += [psa_want_symbol(sym)
                                    for i, sym in enumerate(kt.params)]
        if kt.name.endswith('_PUBLIC_KEY'):
            # The library checks whether the key type is a public key generically,
            # before it reaches a point where it needs support for the specific key
            # type, so it returns INVALID_ARGUMENT for unsupported public key types.
            generate_dependencies = []
            result = 'PSA_ERROR_INVALID_ARGUMENT'
        else:
            generate_dependencies = fix_key_pair_dependencies(import_dependencies, 'GENERATE')
        for bits in kt.sizes_to_test():
            if kt.name == 'PSA_KEY_TYPE_RSA_KEY_PAIR':
                size_dependency = "PSA_VENDOR_RSA_GENERATE_MIN_KEY_BITS <= " +  str(bits)
                test_dependencies = generate_dependencies + [size_dependency]
            else:
                test_dependencies = generate_dependencies
            yield test_case_for_key_generation(
                kt.expression, bits,
                finish_family_dependencies(test_dependencies, bits),
                str(bits),
                result
            )

    def test_cases_for_key_generation(self) -> Iterator[test_case.TestCase]:
        """Generate test cases that exercise the generation of keys."""
        for key_type in sorted(self.constructors.key_types):
            if key_type in self.ECC_KEY_TYPES:
                continue
            if key_type in self.DH_KEY_TYPES:
                continue
            kt = crypto_knowledge.KeyType(key_type)
            yield from self.test_cases_for_key_type_key_generation(kt)
        for curve_family in sorted(self.constructors.ecc_curves):
            for constr in self.ECC_KEY_TYPES:
                kt = crypto_knowledge.KeyType(constr, [curve_family])
                yield from self.test_cases_for_key_type_key_generation(kt)
        for dh_family in sorted(self.constructors.dh_groups):
            for constr in self.DH_KEY_TYPES:
                kt = crypto_knowledge.KeyType(constr, [dh_family])
                yield from self.test_cases_for_key_type_key_generation(kt)

class OpFail:
    """Generate test cases for operations that must fail."""
    #pylint: disable=too-few-public-methods

    class Reason(enum.Enum):
        NOT_SUPPORTED = 0
        INVALID = 1
        INCOMPATIBLE = 2
        PUBLIC = 3

    def __init__(self, info: Information) -> None:
        self.constructors = info.constructors
        key_type_expressions = self.constructors.generate_expressions(
            sorted(self.constructors.key_types)
        )
        self.key_types = [crypto_knowledge.KeyType(kt_expr)
                          for kt_expr in key_type_expressions]

    def make_test_case(
            self,
            alg: crypto_knowledge.Algorithm,
            category: crypto_knowledge.AlgorithmCategory,
            reason: 'Reason',
            kt: Optional[crypto_knowledge.KeyType] = None,
            not_deps: FrozenSet[str] = frozenset(),
    ) -> test_case.TestCase:
        """Construct a failure test case for a one-key or keyless operation."""
        #pylint: disable=too-many-arguments,too-many-locals
        tc = test_case.TestCase()
        pretty_alg = alg.short_expression()
        if reason == self.Reason.NOT_SUPPORTED:
            short_deps = [re.sub(r'PSA_WANT_ALG_', r'', dep)
                          for dep in not_deps]
            pretty_reason = '!' + '&'.join(sorted(short_deps))
        else:
            pretty_reason = reason.name.lower()
        if kt:
            key_type = kt.expression
            pretty_type = kt.short_expression()
        else:
            key_type = ''
            pretty_type = ''
        tc.set_description('PSA {} {}: {}{}'
                           .format(category.name.lower(),
                                   pretty_alg,
                                   pretty_reason,
                                   ' with ' + pretty_type if pretty_type else ''))
        dependencies = automatic_dependencies(alg.base_expression, key_type)
        dependencies = fix_key_pair_dependencies(dependencies, 'BASIC')
        for i, dep in enumerate(dependencies):
            if dep in not_deps:
                dependencies[i] = '!' + dep
        tc.set_dependencies(dependencies)
        tc.set_function(category.name.lower() + '_fail')
        arguments = [] # type: List[str]
        if kt:
            key_material = kt.key_material(kt.sizes_to_test()[0])
            arguments += [key_type, test_case.hex_string(key_material)]
        arguments.append(alg.expression)
        if category.is_asymmetric():
            arguments.append('1' if reason == self.Reason.PUBLIC else '0')
        error = ('NOT_SUPPORTED' if reason == self.Reason.NOT_SUPPORTED else
                 'INVALID_ARGUMENT')
        arguments.append('PSA_ERROR_' + error)
        tc.set_arguments(arguments)
        return tc

    def no_key_test_cases(
            self,
            alg: crypto_knowledge.Algorithm,
            category: crypto_knowledge.AlgorithmCategory,
    ) -> Iterator[test_case.TestCase]:
        """Generate failure test cases for keyless operations with the specified algorithm."""
        if alg.can_do(category):
            # Compatible operation, unsupported algorithm
            for dep in automatic_dependencies(alg.base_expression):
                yield self.make_test_case(alg, category,
                                          self.Reason.NOT_SUPPORTED,
                                          not_deps=frozenset([dep]))
        else:
            # Incompatible operation, supported algorithm
            yield self.make_test_case(alg, category, self.Reason.INVALID)

    def one_key_test_cases(
            self,
            alg: crypto_knowledge.Algorithm,
            category: crypto_knowledge.AlgorithmCategory,
    ) -> Iterator[test_case.TestCase]:
        """Generate failure test cases for one-key operations with the specified algorithm."""
        for kt in self.key_types:
            key_is_compatible = kt.can_do(alg)
            if key_is_compatible and alg.can_do(category):
                # Compatible key and operation, unsupported algorithm
                for dep in automatic_dependencies(alg.base_expression):
                    yield self.make_test_case(alg, category,
                                              self.Reason.NOT_SUPPORTED,
                                              kt=kt, not_deps=frozenset([dep]))
                # Public key for a private-key operation
                if category.is_asymmetric() and kt.is_public():
                    yield self.make_test_case(alg, category,
                                              self.Reason.PUBLIC,
                                              kt=kt)
            elif key_is_compatible:
                # Compatible key, incompatible operation, supported algorithm
                yield self.make_test_case(alg, category,
                                          self.Reason.INVALID,
                                          kt=kt)
            elif alg.can_do(category):
                # Incompatible key, compatible operation, supported algorithm
                yield self.make_test_case(alg, category,
                                          self.Reason.INCOMPATIBLE,
                                          kt=kt)
            else:
                # Incompatible key and operation. Don't test cases where
                # multiple things are wrong, to keep the number of test
                # cases reasonable.
                pass

    def test_cases_for_algorithm(
            self,
            alg: crypto_knowledge.Algorithm,
    ) -> Iterator[test_case.TestCase]:
        """Generate operation failure test cases for the specified algorithm."""
        for category in crypto_knowledge.AlgorithmCategory:
            if category == crypto_knowledge.AlgorithmCategory.PAKE:
                # PAKE operations are not implemented yet
                pass
            elif category.requires_key():
                yield from self.one_key_test_cases(alg, category)
            else:
                yield from self.no_key_test_cases(alg, category)

    def all_test_cases(self) -> Iterator[test_case.TestCase]:
        """Generate all test cases for operations that must fail."""
        algorithms = sorted(self.constructors.algorithms)
        for expr in self.constructors.generate_expressions(algorithms):
            alg = crypto_knowledge.Algorithm(expr)
            yield from self.test_cases_for_algorithm(alg)


class StorageKey(psa_storage.Key):
    """Representation of a key for storage format testing."""

    IMPLICIT_USAGE_FLAGS = {
        'PSA_KEY_USAGE_SIGN_HASH': 'PSA_KEY_USAGE_SIGN_MESSAGE',
        'PSA_KEY_USAGE_VERIFY_HASH': 'PSA_KEY_USAGE_VERIFY_MESSAGE'
    } #type: Dict[str, str]
    """Mapping of usage flags to the flags that they imply."""

    def __init__(
            self,
            usage: Iterable[str],
            without_implicit_usage: Optional[bool] = False,
            **kwargs
    ) -> None:
        """Prepare to generate a key.

        * `usage`                 : The usage flags used for the key.
        * `without_implicit_usage`: Flag to define to apply the usage extension
        """
        usage_flags = set(usage)
        if not without_implicit_usage:
            for flag in sorted(usage_flags):
                if flag in self.IMPLICIT_USAGE_FLAGS:
                    usage_flags.add(self.IMPLICIT_USAGE_FLAGS[flag])
        if usage_flags:
            usage_expression = ' | '.join(sorted(usage_flags))
        else:
            usage_expression = '0'
        super().__init__(usage=usage_expression, **kwargs)

class StorageTestData(StorageKey):
    """Representation of test case data for storage format testing."""

    def __init__(
            self,
            description: str,
            expected_usage: Optional[List[str]] = None,
            **kwargs
    ) -> None:
        """Prepare to generate test data

        * `description`   : used for the test case names
        * `expected_usage`: the usage flags generated as the expected usage flags
                            in the test cases. CAn differ from the usage flags
                            stored in the keys because of the usage flags extension.
        """
        super().__init__(**kwargs)
        self.description = description #type: str
        if expected_usage is None:
            self.expected_usage = self.usage #type: psa_storage.Expr
        elif expected_usage:
            self.expected_usage = psa_storage.Expr(' | '.join(expected_usage))
        else:
            self.expected_usage = psa_storage.Expr(0)

class StorageFormat:
    """Storage format stability test cases."""

    def __init__(self, info: Information, version: int, forward: bool) -> None:
        """Prepare to generate test cases for storage format stability.

        * `info`: information about the API. See the `Information` class.
        * `version`: the storage format version to generate test cases for.
        * `forward`: if true, generate forward compatibility test cases which
          save a key and check that its representation is as intended. Otherwise
          generate backward compatibility test cases which inject a key
          representation and check that it can be read and used.
        """
        self.constructors = info.constructors #type: macro_collector.PSAMacroEnumerator
        self.version = version #type: int
        self.forward = forward #type: bool

    RSA_OAEP_RE = re.compile(r'PSA_ALG_RSA_OAEP\((.*)\)\Z')
    BRAINPOOL_RE = re.compile(r'PSA_KEY_TYPE_\w+\(PSA_ECC_FAMILY_BRAINPOOL_\w+\)\Z')
    @classmethod
    def exercise_key_with_algorithm(
            cls,
            key_type: psa_storage.Expr, bits: int,
            alg: psa_storage.Expr
    ) -> bool:
        """Whether to exercise the given key with the given algorithm.

        Normally only the type and algorithm matter for compatibility, and
        this is handled in crypto_knowledge.KeyType.can_do(). This function
        exists to detect exceptional cases. Exceptional cases detected here
        are not tested in OpFail and should therefore have manually written
        test cases.
        """
        # Some test keys have the RAW_DATA type and attributes that don't
        # necessarily make sense. We do this to validate numerical
        # encodings of the attributes.
        # Raw data keys have no useful exercise anyway so there is no
        # loss of test coverage.
        if key_type.string == 'PSA_KEY_TYPE_RAW_DATA':
            return False
        # OAEP requires room for two hashes plus wrapping
        m = cls.RSA_OAEP_RE.match(alg.string)
        if m:
            hash_alg = m.group(1)
            hash_length = crypto_knowledge.Algorithm.hash_length(hash_alg)
            key_length = (bits + 7) // 8
            # Leave enough room for at least one byte of plaintext
            return key_length > 2 * hash_length + 2
        # There's nothing wrong with ECC keys on Brainpool curves,
        # but operations with them are very slow. So we only exercise them
        # with a single algorithm, not with all possible hashes. We do
        # exercise other curves with all algorithms so test coverage is
        # perfectly adequate like this.
        m = cls.BRAINPOOL_RE.match(key_type.string)
        if m and alg.string != 'PSA_ALG_ECDSA_ANY':
            return False
        return True

    def make_test_case(self, key: StorageTestData) -> test_case.TestCase:
        """Construct a storage format test case for the given key.

        If ``forward`` is true, generate a forward compatibility test case:
        create a key and validate that it has the expected representation.
        Otherwise generate a backward compatibility test case: inject the
        key representation into storage and validate that it can be read
        correctly.
        """
        verb = 'save' if self.forward else 'read'
        tc = test_case.TestCase()
        tc.set_description(verb + ' ' + key.description)
        dependencies = automatic_dependencies(
            key.lifetime.string, key.type.string,
            key.alg.string, key.alg2.string,
        )
        dependencies = finish_family_dependencies(dependencies, key.bits)
        dependencies += generate_key_dependencies(key.description)
        dependencies = fix_key_pair_dependencies(dependencies, 'BASIC')
        tc.set_dependencies(dependencies)
        tc.set_function('key_storage_' + verb)
        if self.forward:
            extra_arguments = []
        else:
            flags = []
            if self.exercise_key_with_algorithm(key.type, key.bits, key.alg):
                flags.append('TEST_FLAG_EXERCISE')
            if 'READ_ONLY' in key.lifetime.string:
                flags.append('TEST_FLAG_READ_ONLY')
            extra_arguments = [' | '.join(flags) if flags else '0']
        tc.set_arguments([key.lifetime.string,
                          key.type.string, str(key.bits),
                          key.expected_usage.string,
                          key.alg.string, key.alg2.string,
                          '"' + key.material.hex() + '"',
                          '"' + key.hex() + '"',
                          *extra_arguments])
        return tc

    def key_for_lifetime(
            self,
            lifetime: str,
    ) -> StorageTestData:
        """Construct a test key for the given lifetime."""
        short = lifetime
        short = re.sub(r'PSA_KEY_LIFETIME_FROM_PERSISTENCE_AND_LOCATION',
                       r'', short)
        short = crypto_knowledge.short_expression(short)
        description = 'lifetime: ' + short
        key = StorageTestData(version=self.version,
                              id=1, lifetime=lifetime,
                              type='PSA_KEY_TYPE_RAW_DATA', bits=8,
                              usage=['PSA_KEY_USAGE_EXPORT'], alg=0, alg2=0,
                              material=b'L',
                              description=description)
        return key

    def all_keys_for_lifetimes(self) -> Iterator[StorageTestData]:
        """Generate test keys covering lifetimes."""
        lifetimes = sorted(self.constructors.lifetimes)
        expressions = self.constructors.generate_expressions(lifetimes)
        for lifetime in expressions:
            # Don't attempt to create or load a volatile key in storage
            if 'VOLATILE' in lifetime:
                continue
            # Don't attempt to create a read-only key in storage,
            # but do attempt to load one.
            if 'READ_ONLY' in lifetime and self.forward:
                continue
            yield self.key_for_lifetime(lifetime)

    def key_for_usage_flags(
            self,
            usage_flags: List[str],
            short: Optional[str] = None,
            test_implicit_usage: Optional[bool] = True
    ) -> StorageTestData:
        """Construct a test key for the given key usage."""
        extra_desc = ' without implication' if test_implicit_usage else ''
        description = 'usage' + extra_desc + ': '
        key1 = StorageTestData(version=self.version,
                               id=1, lifetime=0x00000001,
                               type='PSA_KEY_TYPE_RAW_DATA', bits=8,
                               expected_usage=usage_flags,
                               without_implicit_usage=not test_implicit_usage,
                               usage=usage_flags, alg=0, alg2=0,
                               material=b'K',
                               description=description)
        if short is None:
            usage_expr = key1.expected_usage.string
            key1.description += crypto_knowledge.short_expression(usage_expr)
        else:
            key1.description += short
        return key1

    def generate_keys_for_usage_flags(self, **kwargs) -> Iterator[StorageTestData]:
        """Generate test keys covering usage flags."""
        known_flags = sorted(self.constructors.key_usage_flags)
        yield self.key_for_usage_flags(['0'], **kwargs)
        for usage_flag in known_flags:
            yield self.key_for_usage_flags([usage_flag], **kwargs)
        for flag1, flag2 in zip(known_flags,
                                known_flags[1:] + [known_flags[0]]):
            yield self.key_for_usage_flags([flag1, flag2], **kwargs)

    def generate_key_for_all_usage_flags(self) -> Iterator[StorageTestData]:
        known_flags = sorted(self.constructors.key_usage_flags)
        yield self.key_for_usage_flags(known_flags, short='all known')

    def all_keys_for_usage_flags(self) -> Iterator[StorageTestData]:
        yield from self.generate_keys_for_usage_flags()
        yield from self.generate_key_for_all_usage_flags()

    def key_for_type_and_alg(
            self,
            kt: crypto_knowledge.KeyType,
            bits: int,
            alg: Optional[crypto_knowledge.Algorithm] = None,
    ) -> StorageTestData:
        """Construct a test key of the given type.

        If alg is not None, this key allows it.
        """
        usage_flags = ['PSA_KEY_USAGE_EXPORT']
        alg1 = 0 #type: psa_storage.Exprable
        alg2 = 0
        if alg is not None:
            alg1 = alg.expression
            usage_flags += alg.usage_flags(public=kt.is_public())
        key_material = kt.key_material(bits)
        description = 'type: {} {}-bit'.format(kt.short_expression(1), bits)
        if alg is not None:
            description += ', ' + alg.short_expression(1)
        key = StorageTestData(version=self.version,
                              id=1, lifetime=0x00000001,
                              type=kt.expression, bits=bits,
                              usage=usage_flags, alg=alg1, alg2=alg2,
                              material=key_material,
                              description=description)
        return key

    def keys_for_type(
            self,
            key_type: str,
            all_algorithms: List[crypto_knowledge.Algorithm],
    ) -> Iterator[StorageTestData]:
        """Generate test keys for the given key type."""
        kt = crypto_knowledge.KeyType(key_type)
        for bits in kt.sizes_to_test():
            # Test a non-exercisable key, as well as exercisable keys for
            # each compatible algorithm.
            # To do: test reading a key from storage with an incompatible
            # or unsupported algorithm.
            yield self.key_for_type_and_alg(kt, bits)
            compatible_algorithms = [alg for alg in all_algorithms
                                     if kt.can_do(alg)]
            for alg in compatible_algorithms:
                yield self.key_for_type_and_alg(kt, bits, alg)

    def all_keys_for_types(self) -> Iterator[StorageTestData]:
        """Generate test keys covering key types and their representations."""
        key_types = sorted(self.constructors.key_types)
        all_algorithms = [crypto_knowledge.Algorithm(alg)
                          for alg in self.constructors.generate_expressions(
                              sorted(self.constructors.algorithms)
                          )]
        for key_type in self.constructors.generate_expressions(key_types):
            yield from self.keys_for_type(key_type, all_algorithms)

    def keys_for_algorithm(self, alg: str) -> Iterator[StorageTestData]:
        """Generate test keys for the encoding of the specified algorithm."""
        # These test cases only validate the encoding of algorithms, not
        # whether the key read from storage is suitable for an operation.
        # `keys_for_types` generate read tests with an algorithm and a
        # compatible key.
        descr = crypto_knowledge.short_expression(alg, 1)
        usage = ['PSA_KEY_USAGE_EXPORT']
        key1 = StorageTestData(version=self.version,
                               id=1, lifetime=0x00000001,
                               type='PSA_KEY_TYPE_RAW_DATA', bits=8,
                               usage=usage, alg=alg, alg2=0,
                               material=b'K',
                               description='alg: ' + descr)
        yield key1
        key2 = StorageTestData(version=self.version,
                               id=1, lifetime=0x00000001,
                               type='PSA_KEY_TYPE_RAW_DATA', bits=8,
                               usage=usage, alg=0, alg2=alg,
                               material=b'L',
                               description='alg2: ' + descr)
        yield key2

    def all_keys_for_algorithms(self) -> Iterator[StorageTestData]:
        """Generate test keys covering algorithm encodings."""
        algorithms = sorted(self.constructors.algorithms)
        for alg in self.constructors.generate_expressions(algorithms):
            yield from self.keys_for_algorithm(alg)

    def generate_all_keys(self) -> Iterator[StorageTestData]:
        """Generate all keys for the test cases."""
        yield from self.all_keys_for_lifetimes()
        yield from self.all_keys_for_usage_flags()
        yield from self.all_keys_for_types()
        yield from self.all_keys_for_algorithms()

    def all_test_cases(self) -> Iterator[test_case.TestCase]:
        """Generate all storage format test cases."""
        # First build a list of all keys, then construct all the corresponding
        # test cases. This allows all required information to be obtained in
        # one go, which is a significant performance gain as the information
        # includes numerical values obtained by compiling a C program.
        all_keys = list(self.generate_all_keys())
        for key in all_keys:
            if key.location_value() != 0:
                # Skip keys with a non-default location, because they
                # require a driver and we currently have no mechanism to
                # determine whether a driver is available.
                continue
            yield self.make_test_case(key)

class StorageFormatForward(StorageFormat):
    """Storage format stability test cases for forward compatibility."""

    def __init__(self, info: Information, version: int) -> None:
        super().__init__(info, version, True)

class StorageFormatV0(StorageFormat):
    """Storage format stability test cases for version 0 compatibility."""

    def __init__(self, info: Information) -> None:
        super().__init__(info, 0, False)

    def all_keys_for_usage_flags(self) -> Iterator[StorageTestData]:
        """Generate test keys covering usage flags."""
        yield from super().all_keys_for_usage_flags()
        yield from self.generate_keys_for_usage_flags(test_implicit_usage=False)

    def keys_for_implicit_usage(
            self,
            implyer_usage: str,
            alg: str,
            key_type: crypto_knowledge.KeyType
    ) -> StorageTestData:
        # pylint: disable=too-many-locals
        """Generate test keys for the specified implicit usage flag,
           algorithm and key type combination.
        """
        bits = key_type.sizes_to_test()[0]
        implicit_usage = StorageKey.IMPLICIT_USAGE_FLAGS[implyer_usage]
        usage_flags = ['PSA_KEY_USAGE_EXPORT']
        material_usage_flags = usage_flags + [implyer_usage]
        expected_usage_flags = material_usage_flags + [implicit_usage]
        alg2 = 0
        key_material = key_type.key_material(bits)
        usage_expression = crypto_knowledge.short_expression(implyer_usage, 1)
        alg_expression = crypto_knowledge.short_expression(alg, 1)
        key_type_expression = key_type.short_expression(1)
        description = 'implied by {}: {} {} {}-bit'.format(
            usage_expression, alg_expression, key_type_expression, bits)
        key = StorageTestData(version=self.version,
                              id=1, lifetime=0x00000001,
                              type=key_type.expression, bits=bits,
                              usage=material_usage_flags,
                              expected_usage=expected_usage_flags,
                              without_implicit_usage=True,
                              alg=alg, alg2=alg2,
                              material=key_material,
                              description=description)
        return key

    def gather_key_types_for_sign_alg(self) -> Dict[str, List[str]]:
        # pylint: disable=too-many-locals
        """Match possible key types for sign algorithms."""
        # To create a valid combination both the algorithms and key types
        # must be filtered. Pair them with keywords created from its names.
        incompatible_alg_keyword = frozenset(['RAW', 'ANY', 'PURE'])
        incompatible_key_type_keywords = frozenset(['MONTGOMERY'])
        keyword_translation = {
            'ECDSA': 'ECC',
            'ED[0-9]*.*' : 'EDWARDS'
        }
        exclusive_keywords = {
            'EDWARDS': 'ECC'
        }
        key_types = set(self.constructors.generate_expressions(self.constructors.key_types))
        algorithms = set(self.constructors.generate_expressions(self.constructors.sign_algorithms))
        alg_with_keys = {} #type: Dict[str, List[str]]
        translation_table = str.maketrans('(', '_', ')')
        for alg in algorithms:
            # Generate keywords from the name of the algorithm
            alg_keywords = set(alg.partition('(')[0].split(sep='_')[2:])
            # Translate keywords for better matching with the key types
            for keyword in alg_keywords.copy():
                for pattern, replace in keyword_translation.items():
                    if re.match(pattern, keyword):
                        alg_keywords.remove(keyword)
                        alg_keywords.add(replace)
            # Filter out incompatible algorithms
            if not alg_keywords.isdisjoint(incompatible_alg_keyword):
                continue

            for key_type in key_types:
                # Generate keywords from the of the key type
                key_type_keywords = set(key_type.translate(translation_table).split(sep='_')[3:])

                # Remove ambiguous keywords
                for keyword1, keyword2 in exclusive_keywords.items():
                    if keyword1 in key_type_keywords:
                        key_type_keywords.remove(keyword2)

                if key_type_keywords.isdisjoint(incompatible_key_type_keywords) and\
                   not key_type_keywords.isdisjoint(alg_keywords):
                    if alg in alg_with_keys:
                        alg_with_keys[alg].append(key_type)
                    else:
                        alg_with_keys[alg] = [key_type]
        return alg_with_keys

    def all_keys_for_implicit_usage(self) -> Iterator[StorageTestData]:
        """Generate test keys for usage flag extensions."""
        # Generate a key type and algorithm pair for each extendable usage
        # flag to generate a valid key for exercising. The key is generated
        # without usage extension to check the extension compatibility.
        alg_with_keys = self.gather_key_types_for_sign_alg()

        for usage in sorted(StorageKey.IMPLICIT_USAGE_FLAGS, key=str):
            for alg in sorted(alg_with_keys):
                for key_type in sorted(alg_with_keys[alg]):
                    # The key types must be filtered to fit the specific usage flag.
                    kt = crypto_knowledge.KeyType(key_type)
                    if kt.is_public() and '_SIGN_' in usage:
                        # Can't sign with a public key
                        continue
                    yield self.keys_for_implicit_usage(usage, alg, kt)

    def generate_all_keys(self) -> Iterator[StorageTestData]:
        yield from super().generate_all_keys()
        yield from self.all_keys_for_implicit_usage()

class PSATestGenerator(test_data_generation.TestGenerator):
    """Test generator subclass including PSA targets and info."""
    # Note that targets whose names contain 'test_format' have their content
    # validated by `abi_check.py`.
    targets = {
        'test_suite_psa_crypto_generate_key.generated':
        lambda info: KeyGenerate(info).test_cases_for_key_generation(),
        'test_suite_psa_crypto_not_supported.generated':
        lambda info: KeyTypeNotSupported(info).test_cases_for_not_supported(),
        'test_suite_psa_crypto_op_fail.generated':
        lambda info: OpFail(info).all_test_cases(),
        'test_suite_psa_crypto_storage_format.current':
        lambda info: StorageFormatForward(info, 0).all_test_cases(),
        'test_suite_psa_crypto_storage_format.v0':
        lambda info: StorageFormatV0(info).all_test_cases(),
    } #type: Dict[str, Callable[[Information], Iterable[test_case.TestCase]]]

    def __init__(self, options):
        super().__init__(options)
        self.info = Information()

    def generate_target(self, name: str, *target_args) -> None:
        super().generate_target(name, self.info)

if __name__ == '__main__':
    test_data_generation.main(sys.argv[1:], __doc__, PSATestGenerator)