scripts/generate_psa_constants.py

#!/usr/bin/env python3

"""Generate psa_constant_names_generated.c
which is included by programs/psa/psa_constant_names.c.
The code generated by this module is only meant to be used in the context
of that program.

An argument passed to this script will modify the output directory where the
file is written:
* by default (no arguments passed): writes to programs/psa/
* OUTPUT_FILE_DIR passed: writes to OUTPUT_FILE_DIR/
"""

import os
import re
import sys

OUTPUT_TEMPLATE = '''\
/* Automatically generated by generate_psa_constant.py. DO NOT EDIT. */

static const char *psa_strerror(psa_status_t status)
{
    switch (status) {
    %(status_cases)s
    default: return NULL;
    }
}

static const char *psa_ecc_curve_name(psa_ecc_curve_t curve)
{
    switch (curve) {
    %(ecc_curve_cases)s
    default: return NULL;
    }
}

static const char *psa_dh_group_name(psa_dh_group_t group)
{
    switch (group) {
    %(dh_group_cases)s
    default: return NULL;
    }
}

static const char *psa_hash_algorithm_name(psa_algorithm_t hash_alg)
{
    switch (hash_alg) {
    %(hash_algorithm_cases)s
    default: return NULL;
    }
}

static const char *psa_ka_algorithm_name(psa_algorithm_t ka_alg)
{
    switch (ka_alg) {
    %(ka_algorithm_cases)s
    default: return NULL;
    }
}

static int psa_snprint_key_type(char *buffer, size_t buffer_size,
                                psa_key_type_t type)
{
    size_t required_size = 0;
    switch (type) {
    %(key_type_cases)s
    default:
        %(key_type_code)s{
            return snprintf(buffer, buffer_size,
                            "0x%%04x", (unsigned) type);
        }
        break;
    }
    buffer[0] = 0;
    return (int) required_size;
}

#define NO_LENGTH_MODIFIER 0xfffffffflu
static int psa_snprint_algorithm(char *buffer, size_t buffer_size,
                                 psa_algorithm_t alg)
{
    size_t required_size = 0;
    psa_algorithm_t core_alg = alg;
    unsigned long length_modifier = NO_LENGTH_MODIFIER;
    if (PSA_ALG_IS_MAC(alg)) {
        core_alg = PSA_ALG_TRUNCATED_MAC(alg, 0);
        if (core_alg != alg) {
            append(&buffer, buffer_size, &required_size,
                   "PSA_ALG_TRUNCATED_MAC(", 22);
            length_modifier = PSA_MAC_TRUNCATED_LENGTH(alg);
        }
    } else if (PSA_ALG_IS_AEAD(alg)) {
        core_alg = PSA_ALG_AEAD_WITH_DEFAULT_TAG_LENGTH(alg);
        if (core_alg == 0) {
            /* For unknown AEAD algorithms, there is no "default tag length". */
            core_alg = alg;
        } else if (core_alg != alg) {
            append(&buffer, buffer_size, &required_size,
                   "PSA_ALG_AEAD_WITH_TAG_LENGTH(", 29);
            length_modifier = PSA_AEAD_TAG_LENGTH(alg);
        }
    } else if (PSA_ALG_IS_KEY_AGREEMENT(alg) &&
               !PSA_ALG_IS_RAW_KEY_AGREEMENT(alg)) {
        core_alg = PSA_ALG_KEY_AGREEMENT_GET_KDF(alg);
        append(&buffer, buffer_size, &required_size,
               "PSA_ALG_KEY_AGREEMENT(", 22);
        append_with_alg(&buffer, buffer_size, &required_size,
                        psa_ka_algorithm_name,
                        PSA_ALG_KEY_AGREEMENT_GET_BASE(alg));
        append(&buffer, buffer_size, &required_size, ", ", 2);
    }
    switch (core_alg) {
    %(algorithm_cases)s
    default:
        %(algorithm_code)s{
            append_integer(&buffer, buffer_size, &required_size,
                           "0x%%08lx", (unsigned long) core_alg);
        }
        break;
    }
    if (core_alg != alg) {
        if (length_modifier != NO_LENGTH_MODIFIER) {
            append(&buffer, buffer_size, &required_size, ", ", 2);
            append_integer(&buffer, buffer_size, &required_size,
                           "%%lu", length_modifier);
        }
        append(&buffer, buffer_size, &required_size, ")", 1);
    }
    buffer[0] = 0;
    return (int) required_size;
}

static int psa_snprint_key_usage(char *buffer, size_t buffer_size,
                                 psa_key_usage_t usage)
{
    size_t required_size = 0;
    if (usage == 0) {
        if (buffer_size > 1) {
            buffer[0] = '0';
            buffer[1] = 0;
        } else if (buffer_size == 1) {
            buffer[0] = 0;
        }
        return 1;
    }
%(key_usage_code)s
    if (usage != 0) {
        if (required_size != 0) {
            append(&buffer, buffer_size, &required_size, " | ", 3);
        }
        append_integer(&buffer, buffer_size, &required_size,
                       "0x%%08lx", (unsigned long) usage);
    } else {
        buffer[0] = 0;
    }
    return (int) required_size;
}

/* End of automatically generated file. */
'''

KEY_TYPE_FROM_CURVE_TEMPLATE = '''if (%(tester)s(type)) {
            append_with_curve(&buffer, buffer_size, &required_size,
                              "%(builder)s", %(builder_length)s,
                              PSA_KEY_TYPE_GET_CURVE(type));
        } else '''

KEY_TYPE_FROM_GROUP_TEMPLATE = '''if (%(tester)s(type)) {
            append_with_group(&buffer, buffer_size, &required_size,
                              "%(builder)s", %(builder_length)s,
                              PSA_KEY_TYPE_GET_GROUP(type));
        } else '''

ALGORITHM_FROM_HASH_TEMPLATE = '''if (%(tester)s(core_alg)) {
            append(&buffer, buffer_size, &required_size,
                   "%(builder)s(", %(builder_length)s + 1);
            append_with_alg(&buffer, buffer_size, &required_size,
                            psa_hash_algorithm_name,
                            PSA_ALG_GET_HASH(core_alg));
            append(&buffer, buffer_size, &required_size, ")", 1);
        } else '''

BIT_TEST_TEMPLATE = '''\
    if (%(var)s & %(flag)s) {
        if (required_size != 0) {
            append(&buffer, buffer_size, &required_size, " | ", 3);
        }
        append(&buffer, buffer_size, &required_size, "%(flag)s", %(length)d);
        %(var)s ^= %(flag)s;
    }\
'''

class MacroCollector:
    """Collect PSA crypto macro definitions from C header files.

    1. Call `read_file` on the input header file(s).
    2. Call `write_file` to write ``psa_constant_names_generated.c``.
    """

    def __init__(self):
        self.statuses = set()
        self.key_types = set()
        self.key_types_from_curve = {}
        self.key_types_from_group = {}
        self.ecc_curves = set()
        self.dh_groups = set()
        self.algorithms = set()
        self.hash_algorithms = set()
        self.ka_algorithms = set()
        self.algorithms_from_hash = {}
        self.key_usages = set()

    # "#define" followed by a macro name with either no parameters
    # or a single parameter and a non-empty expansion.
    # Grab the macro name in group 1, the parameter name if any in group 2
    # and the expansion in group 3.
    _define_directive_re = re.compile(r'\s*#\s*define\s+(\w+)' +
                                      r'(?:\s+|\((\w+)\)\s*)' +
                                      r'(.+)')
    _deprecated_definition_re = re.compile(r'\s*MBEDTLS_DEPRECATED')

    def read_line(self, line):
        """Parse a C header line and record the PSA identifier it defines if any.
        This function analyzes lines that start with "#define PSA_"
        (up to non-significant whitespace) and skips all non-matching lines.
        """
        # pylint: disable=too-many-branches
        m = re.match(self._define_directive_re, line)
        if not m:
            return
        name, parameter, expansion = m.groups()
        expansion = re.sub(r'/\*.*?\*/|//.*', r' ', expansion)
        if re.match(self._deprecated_definition_re, expansion):
            # Skip deprecated values, which are assumed to be
            # backward compatibility aliases that share
            # numerical values with non-deprecated values.
            return
        if name.endswith('_FLAG') or name.endswith('MASK'):
            # Macro only to build actual values
            return
        elif (name.startswith('PSA_ERROR_') or name == 'PSA_SUCCESS') \
           and not parameter:
            self.statuses.add(name)
        elif name.startswith('PSA_KEY_TYPE_') and not parameter:
            self.key_types.add(name)
        elif name.startswith('PSA_KEY_TYPE_') and parameter == 'curve':
            self.key_types_from_curve[name] = name[:13] + 'IS_' + name[13:]
        elif name.startswith('PSA_KEY_TYPE_') and parameter == 'group':
            self.key_types_from_group[name] = name[:13] + 'IS_' + name[13:]
        elif name.startswith('PSA_ECC_CURVE_') and not parameter:
            self.ecc_curves.add(name)
        elif name.startswith('PSA_DH_GROUP_') and not parameter:
            self.dh_groups.add(name)
        elif name.startswith('PSA_ALG_') and not parameter:
            if name in ['PSA_ALG_ECDSA_BASE',
                        'PSA_ALG_RSA_PKCS1V15_SIGN_BASE']:
                # Ad hoc skipping of duplicate names for some numerical values
                return
            self.algorithms.add(name)
            # Ad hoc detection of hash algorithms
            if re.search(r'0x010000[0-9A-Fa-f]{2}', expansion):
                self.hash_algorithms.add(name)
            # Ad hoc detection of key agreement algorithms
            if re.search(r'0x30[0-9A-Fa-f]{2}0000', expansion):
                self.ka_algorithms.add(name)
        elif name.startswith('PSA_ALG_') and parameter == 'hash_alg':
            if name in ['PSA_ALG_DSA', 'PSA_ALG_ECDSA']:
                # A naming irregularity
                tester = name[:8] + 'IS_RANDOMIZED_' + name[8:]
            else:
                tester = name[:8] + 'IS_' + name[8:]
            self.algorithms_from_hash[name] = tester
        elif name.startswith('PSA_KEY_USAGE_') and not parameter:
            self.key_usages.add(name)
        else:
            # Other macro without parameter
            return

    _nonascii_re = re.compile(rb'[^\x00-\x7f]+')
    _continued_line_re = re.compile(rb'\\\r?\n\Z')
    def read_file(self, header_file):
        for line in header_file:
            m = re.search(self._continued_line_re, line)
            while m:
                cont = next(header_file)
                line = line[:m.start(0)] + cont
                m = re.search(self._continued_line_re, line)
            line = re.sub(self._nonascii_re, rb'', line).decode('ascii')
            self.read_line(line)

    @staticmethod
    def _make_return_case(name):
        return 'case %(name)s: return "%(name)s";' % {'name': name}

    @staticmethod
    def _make_append_case(name):
        template = ('case %(name)s: '
                    'append(&buffer, buffer_size, &required_size, "%(name)s", %(length)d); '
                    'break;')
        return template % {'name': name, 'length': len(name)}

    @staticmethod
    def _make_bit_test(var, flag):
        return BIT_TEST_TEMPLATE % {'var': var,
                                    'flag': flag,
                                    'length': len(flag)}

    def _make_status_cases(self):
        return '\n    '.join(map(self._make_return_case,
                                 sorted(self.statuses)))

    def _make_ecc_curve_cases(self):
        return '\n    '.join(map(self._make_return_case,
                                 sorted(self.ecc_curves)))

    def _make_dh_group_cases(self):
        return '\n    '.join(map(self._make_return_case,
                                 sorted(self.dh_groups)))

    def _make_key_type_cases(self):
        return '\n    '.join(map(self._make_append_case,
                                 sorted(self.key_types)))

    @staticmethod
    def _make_key_type_from_curve_code(builder, tester):
        return KEY_TYPE_FROM_CURVE_TEMPLATE % {'builder': builder,
                                               'builder_length': len(builder),
                                               'tester': tester}

    @staticmethod
    def _make_key_type_from_group_code(builder, tester):
        return KEY_TYPE_FROM_GROUP_TEMPLATE % {'builder': builder,
                                               'builder_length': len(builder),
                                               'tester': tester}

    def _make_ecc_key_type_code(self):
        d = self.key_types_from_curve
        make = self._make_key_type_from_curve_code
        return ''.join([make(k, d[k]) for k in sorted(d.keys())])

    def _make_dh_key_type_code(self):
        d = self.key_types_from_group
        make = self._make_key_type_from_group_code
        return ''.join([make(k, d[k]) for k in sorted(d.keys())])

    def _make_hash_algorithm_cases(self):
        return '\n    '.join(map(self._make_return_case,
                                 sorted(self.hash_algorithms)))

    def _make_ka_algorithm_cases(self):
        return '\n    '.join(map(self._make_return_case,
                                 sorted(self.ka_algorithms)))

    def _make_algorithm_cases(self):
        return '\n    '.join(map(self._make_append_case,
                                 sorted(self.algorithms)))

    @staticmethod
    def _make_algorithm_from_hash_code(builder, tester):
        return ALGORITHM_FROM_HASH_TEMPLATE % {'builder': builder,
                                               'builder_length': len(builder),
                                               'tester': tester}

    def _make_algorithm_code(self):
        d = self.algorithms_from_hash
        make = self._make_algorithm_from_hash_code
        return ''.join([make(k, d[k]) for k in sorted(d.keys())])

    def _make_key_usage_code(self):
        return '\n'.join([self._make_bit_test('usage', bit)
                          for bit in sorted(self.key_usages)])

    def write_file(self, output_file):
        """Generate the pretty-printer function code from the gathered
        constant definitions.
        """
        data = {}
        data['status_cases'] = self._make_status_cases()
        data['ecc_curve_cases'] = self._make_ecc_curve_cases()
        data['dh_group_cases'] = self._make_dh_group_cases()
        data['key_type_cases'] = self._make_key_type_cases()
        data['key_type_code'] = (self._make_ecc_key_type_code() +
                                 self._make_dh_key_type_code())
        data['hash_algorithm_cases'] = self._make_hash_algorithm_cases()
        data['ka_algorithm_cases'] = self._make_ka_algorithm_cases()
        data['algorithm_cases'] = self._make_algorithm_cases()
        data['algorithm_code'] = self._make_algorithm_code()
        data['key_usage_code'] = self._make_key_usage_code()
        output_file.write(OUTPUT_TEMPLATE % data)

def generate_psa_constants(header_file_names, output_file_name):
    collector = MacroCollector()
    for header_file_name in header_file_names:
        with open(header_file_name, 'rb') as header_file:
            collector.read_file(header_file)
    temp_file_name = output_file_name + '.tmp'
    with open(temp_file_name, 'w') as output_file:
        collector.write_file(output_file)
    os.rename(temp_file_name, output_file_name)

if __name__ == '__main__':
    if not os.path.isdir('programs') and os.path.isdir('../programs'):
        os.chdir('..')
    # Allow to change the directory where psa_constant_names_generated.c is written to.
    OUTPUT_FILE_DIR = sys.argv[1] if len(sys.argv) == 2 else "programs/psa"
    generate_psa_constants(['include/psa/crypto_values.h',
                            'include/psa/crypto_extra.h'],
                           OUTPUT_FILE_DIR + '/psa_constant_names_generated.c')