Unit test class for config checks

Unit tests to check whether a configuration is accepted by config checks
done when compilin the library.

The framework provides a class and some smoke tests. It's up to the
consuming branches to provide test cases based on branch-specific knowledge,
and to arrange to run the tests in the CI.

Signed-off-by: Gilles Peskine <[email protected]>

scripts/mbedtls_framework/unittest_config_checks.py

@@ -0,0 +1,171 @@
+"""Test the configuration checks that reject some bad compile-time configs.
+
+This tests the output of ``generate_config_checks.py``.
+This can also let us verify what we enforce in the manually written
+checks in ``<PROJECT>_check_config.h``.
+"""
+
+## Copyright The Mbed TLS Contributors
+## SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+
+import os
+import subprocess
+import sys
+import unittest
+from typing import List, Optional, Pattern, Union
+
+
+class TestConfigChecks(unittest.TestCase):
+    """Unit tests for checks performed via ``<PROJECT>_config.c``.
+
+    This can test the code generated by `config_checks_generator`,
+    as well as manually written checks in `check_config.h`.
+    """
+
+    # Set this to the path to the source file containing the config checks.
+    PROJECT_CONFIG_C = None #type: Optional[str]
+
+    # Project-specific include directories (in addition to /include)
+    PROJECT_SPECIFIC_INCLUDE_DIRECTORIES = [] #type: List[str]
+
+    # Increase the length of strings that assertion failures are willing to
+    # print. This is useful for failures where the preprocessor has a lot
+    # to say.
+    maxDiff = 9999
+
+    def user_config_file_name(self, variant: str) -> str:
+        """Construct a unique temporary file name for a user config header."""
+        name = os.path.splitext(os.path.basename(sys.argv[0]))[0]
+        pid = str(os.getpid())
+        oid = str(id(self))
+        return f'tmp-user_config_{variant}-{name}-{pid}-{oid}.h'
+
+    def write_user_config(self, variant: str, content: Optional[str]) -> Optional[str]:
+        """Write a user configuration file with the given content.
+
+        If content is None, ensure the file does not exist.
+
+        Return None if content is none, otherwise return the file name.
+        """
+        file_name = self.user_config_file_name(variant)
+        if content is None:
+            if os.path.exists(file_name):
+                os.remove(file_name)
+            return None
+        if content and not content.endswith('\n'):
+            content += '\n'
+        with open(file_name, 'w', encoding='ascii') as out:
+            out.write(content)
+        return file_name
+
+    def run_with_config_files(self,
+                              crypto_user_config_file: Optional[str],
+                              mbedtls_user_config_file: Optional[str],
+                              extra_options: List[str],
+                              ) -> subprocess.CompletedProcess:
+        """Run cpp with the given user configuration files.
+
+        Return the CompletedProcess object capturing the return code,
+        stdout and stderr.
+        """
+        cmd = ['cpp']
+        if crypto_user_config_file is not None:
+            cmd.append(f'-DTF_PSA_CRYPTO_USER_CONFIG_FILE="{crypto_user_config_file}"')
+        if mbedtls_user_config_file is not None:
+            cmd.append(f'-DMBEDTLS_USER_CONFIG_FILE="{mbedtls_user_config_file}"')
+        cmd += extra_options
+        assert self.PROJECT_CONFIG_C is not None
+        cmd += ['-I' + dir for dir in self.PROJECT_SPECIFIC_INCLUDE_DIRECTORIES]
+        cmd += ['-Iinclude',
+                '-I.',
+                '-I' + os.path.dirname(self.PROJECT_CONFIG_C)]
+        cmd.append(self.PROJECT_CONFIG_C)
+        return subprocess.run(cmd,
+                              check=False,
+                              encoding='ascii',
+                              stdout=subprocess.PIPE,
+                              stderr=subprocess.PIPE)
+
+    def run_with_config(self,
+                        crypto_user_config: Optional[str],
+                        mbedtls_user_config: Optional[str] = None,
+                        extra_options: Optional[List[str]] = None,
+                        ) -> subprocess.CompletedProcess:
+        """Run cpp with the given content for user configuration files.
+
+        Return the CompletedProcess object capturing the return code,
+        stdout and stderr.
+        """
+        if extra_options is None:
+            extra_options = []
+        crypto_user_config_file = None
+        mbedtls_user_config_file = None
+        try:
+            # Create temporary files without using tempfile because:
+            # 1. Before Python 3.12, tempfile.NamedTemporaryFile does
+            #    not have good support for allowing an external program
+            #    to access the file on Windows.
+            # 2. With a tempfile-provided context, it's awkward to not
+            #    create a file optionally (we only do it when xxx_user_config
+            #    is not None).
+            crypto_user_config_file = \
+                self.write_user_config('crypto', crypto_user_config)
+            mbedtls_user_config_file = \
+                self.write_user_config('mbedtls', mbedtls_user_config)
+            cp = self.run_with_config_files(crypto_user_config_file,
+                                            mbedtls_user_config_file,
+                                            extra_options)
+            return cp
+        finally:
+            if crypto_user_config_file is not None and \
+               os.path.exists(crypto_user_config_file):
+                os.remove(crypto_user_config_file)
+            if mbedtls_user_config_file is not None and \
+               os.path.exists(mbedtls_user_config_file):
+                os.remove(mbedtls_user_config_file)
+
+    def good_case(self,
+                  crypto_user_config: Optional[str],
+                  mbedtls_user_config: Optional[str] = None,
+                  extra_options: Optional[List[str]] = None,
+                  ) -> None:
+        """Run cpp with the given user config(s). Expect no error.
+
+        Pass extra_options on the command line of cpp.
+        """
+        cp = self.run_with_config(crypto_user_config, mbedtls_user_config,
+                                  extra_options=extra_options)
+        # Assert the error text before the status. That way, if it fails,
+        # we see the unexpected error messages in the test log.
+        self.assertEqual(cp.stderr, '')
+        self.assertEqual(cp.returncode, 0)
+
+    def bad_case(self,
+                 crypto_user_config: Optional[str],
+                 mbedtls_user_config: Optional[str] = None,
+                 error: Optional[Union[str, Pattern]] = None,
+                 extra_options: Optional[List[str]] = None,
+                 ) -> None:
+        """Run cpp with the given user config(s). Expect errors.
+
+        Pass extra_options on the command line of cpp.
+
+        If error is given, the standard error from cpp must match this regex.
+        """
+        cp = self.run_with_config(crypto_user_config, mbedtls_user_config,
+                                  extra_options=extra_options)
+        if error is not None:
+            # Assert the error text before the status. That way, if it fails,
+            # we see the unexpected error messages in the test log.
+            self.assertRegex(cp.stderr, error)
+        self.assertGreater(cp.returncode, 0)
+        self.assertLess(cp.returncode, 126)
+
+    # Nominal case, run first
+    def test_01_nominal(self) -> None:
+        self.good_case(None)
+
+    # Trivial error case, run second
+    def test_02_error(self) -> None:
+        self.bad_case('#error "Bad crypto configuration"',
+                      error='"Bad crypto configuration"')