fix(config): restrict censys.cfg to owner-only permissions

censys/common/config.py

@@ -1,6 +1,7 @@
 """Interact with the config file."""
 
 import configparser
+import contextlib
 import os
 from pathlib import Path
 
@@ -29,9 +30,40 @@ def get_config_path() -> str:
     return CONFIG_PATH
 
 
+def _restricted_opener(path: str, flags: int) -> int:
+    """Opener that creates files readable and writable by the owner only.
+
+    Args:
+        path (str): Path to open.
+        flags (int): Flags passed by `open()`.
+
+    Returns:
+        int: File descriptor.
+    """
+    return os.open(path, flags, 0o600)
+
+
+def _try_chmod(path: str, mode: int) -> None:
+    """Best-effort permission tightening.
+
+    Files are already created owner-only by `_restricted_opener`, so failing to
+    tighten an existing path must never stop the config from being written.
+
+    Args:
+        path (str): Path to tighten.
+        mode (int): Desired permission bits.
+    """
+    with contextlib.suppress(OSError):
+        os.chmod(path, mode)
+
+
 def write_config(config: configparser.ConfigParser) -> None:
     """Writes config to file.
 
+    The config file contains API credentials, so the directory and file are
+    created owner-only (0700/0600). Existing paths are tightened on a
+    best-effort basis; the requested modes are still subject to the umask.
+
     Args:
         config (configparser.ConfigParser): Configuration to write.
 
@@ -45,8 +77,12 @@ def write_config(config: configparser.ConfigParser) -> None:
                 "Cannot write to home directory. Please set the `CENSYS_CONFIG_PATH` environmental variable to a writeable location."
             )
         elif not os.path.isdir(CENSYS_PATH):
-            os.makedirs(CENSYS_PATH)
-    with open(config_path, "w") as configfile:
+            os.makedirs(CENSYS_PATH, mode=0o700)
+        else:
+            _try_chmod(CENSYS_PATH, 0o700)
+    if os.path.isfile(config_path):
+        _try_chmod(config_path, 0o600)
+    with open(config_path, "w", opener=_restricted_opener) as configfile:
         config.write(configfile)
 
 

tests/cli/test_config.py

@@ -1,3 +1,7 @@
+import os
+import stat
+from unittest.mock import patch
+
 import pytest
 import responses
 
@@ -6,8 +10,10 @@
     CENSYS_PATH,
     CONFIG_PATH,
     DEFAULT,
+    _restricted_opener,
     default_config,
     get_config,
+    write_config,
 )
 from tests.search.v1.test_api import ACCOUNT_JSON
 from tests.utils import V1_URL, CensysTestCase
@@ -42,6 +48,7 @@ def setUp(self):
         )
         self.mocker.patch("rich.prompt.Prompt.ask", side_effect=prompt_side_effect)
         self.mocker.patch("rich.prompt.Confirm.ask", side_effect=confirm_side_effect)
+        self.mock_chmod = self.mocker.patch("censys.common.config._try_chmod")
 
     def test_search_config(self):
         # Mock
@@ -62,7 +69,7 @@ def test_search_config(self):
             cli_main()
 
         # Assert that the config file was read from the right place
-        self.mock_open.assert_called_with(TEST_CONFIG_PATH, "w")
+        self.mock_open.assert_called_with(TEST_CONFIG_PATH, "w", opener=_restricted_opener)
 
     def test_search_config_failed(self):
         # Mock
@@ -103,7 +110,7 @@ def test_search_config_makedirs(self):
         with pytest.raises(SystemExit, match="0"):
             cli_main()
 
-        mock_makedirs.assert_called_with(CENSYS_PATH)
+        mock_makedirs.assert_called_with(CENSYS_PATH, mode=0o700)
 
     def test_config_default(self):
         mock_isfile = self.mocker.patch("censys.common.config.os.path.isfile", return_value=True)
@@ -134,7 +141,7 @@ def test_search_config_custom_config(self):
             cli_main()
 
         # Assert that the config file was read from the right place
-        self.mock_open.assert_called_with("censys.cfg", "w")
+        self.mock_open.assert_called_with("censys.cfg", "w", opener=_restricted_opener)
 
     def test_search_config_perm_error(self):
         self.patch_args(
@@ -153,3 +160,81 @@ def test_search_config_perm_error(self):
 
         with pytest.raises(SystemExit, match="1"):
             cli_main()
+
+
+@pytest.fixture
+def home_config(tmp_path, mocker, monkeypatch):
+    """Points the default config location at a throwaway home directory."""
+    monkeypatch.delenv("CENSYS_CONFIG_PATH", raising=False)
+    censys_path = tmp_path / ".config" / "censys"
+    config_path = censys_path / "censys.cfg"
+    mocker.patch("censys.common.config.HOME_PATH", str(tmp_path))
+    mocker.patch("censys.common.config.CENSYS_PATH", str(censys_path))
+    mocker.patch("censys.common.config.CONFIG_PATH", str(config_path))
+    return censys_path, config_path
+
+
+def test_write_config_creates_and_rewrites(home_config):
+    censys_path, config_path = home_config
+
+    # First write creates the directory and the file
+    write_config(get_config())
+    assert censys_path.is_dir()
+    assert config_path.is_file()
+
+    # Second write takes the existing-directory and existing-file branches
+    write_config(get_config())
+    assert get_config().get(DEFAULT, "color") == "auto"
+
+
+def test_write_config_survives_unchmodable_path(home_config):
+    # A path we may not chmod must not stop the config from being written:
+    # root-owned config dirs in containers, a non-owned CENSYS_CONFIG_PATH, and
+    # mounts that reject chmod outright (NFS, CIFS, WSL DrvFs without metadata).
+    _, config_path = home_config
+
+    write_config(get_config())
+
+    with patch(
+        "censys.common.config.os.chmod",
+        side_effect=PermissionError(1, "Operation not permitted"),
+    ):
+        write_config(get_config())
+
+    assert config_path.is_file()
+
+
+@pytest.mark.skipif(os.name != "posix", reason="POSIX file permissions only")
+def test_write_config_restricts_permissions(home_config):
+    censys_path, config_path = home_config
+    old_umask = os.umask(0o022)
+    try:
+        write_config(get_config())
+
+        assert stat.S_IMODE(os.stat(censys_path).st_mode) & 0o077 == 0
+        assert stat.S_IMODE(os.stat(config_path).st_mode) & 0o077 == 0
+
+        # Pre-existing loose permissions are tightened on rewrite
+        os.chmod(censys_path, 0o755)
+        os.chmod(config_path, 0o644)
+        write_config(get_config())
+
+        assert stat.S_IMODE(os.stat(censys_path).st_mode) & 0o077 == 0
+        assert stat.S_IMODE(os.stat(config_path).st_mode) & 0o077 == 0
+    finally:
+        os.umask(old_umask)
+
+
+@pytest.mark.skipif(os.name != "posix", reason="POSIX file permissions only")
+def test_write_config_keeps_permissions_when_chmod_fails(home_config):
+    _, config_path = home_config
+
+    write_config(get_config())
+
+    with patch(
+        "censys.common.config.os.chmod",
+        side_effect=PermissionError(1, "Operation not permitted"),
+    ):
+        write_config(get_config())
+
+    assert stat.S_IMODE(os.stat(config_path).st_mode) & 0o077 == 0