fix FileIsReadableValidator and add proper tests (#434)

fixes #433
closes #434

Author: beniwohli

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## Unreleased
+[Check the diff](https://github.com/elastic/apm-agent-python/compare/v4.2.0...master)
+ * fixed an issue with the certificate pinning feature introduced in 4.2.0 (#433, #434)
+    
 ## v4.2.0 
 [Check the diff](https://github.com/elastic/apm-agent-python/compare/v4.1.0...v4.2.0)
 

elasticapm/conf/__init__.py

@@ -172,8 +172,8 @@ def __call__(self, value, field_name):
             raise ConfigurationError("{} does not exist".format(value), field_name)
         elif not os.path.isfile(value):
             raise ConfigurationError("{} is not a file".format(value), field_name)
-        elif not os.access(value):
-            raise ConfigurationError("{} is not accessible".format(value), field_name)
+        elif not os.access(value, os.R_OK):
+            raise ConfigurationError("{} is not readable".format(value), field_name)
         return value
 
 

tests/config/tests.py

@@ -31,11 +31,17 @@
 from __future__ import absolute_import
 
 import logging
+import os
+import platform
+import stat
 
 import mock
+import pytest
 
 from elasticapm.conf import (
     Config,
+    ConfigurationError,
+    FileIsReadableValidator,
     RegexValidator,
     _BoolConfigValue,
     _ConfigBase,
@@ -221,3 +227,35 @@ class MyConfig(_ConfigBase):
 
     c = MyConfig({"CHAIN": "x"})
     assert c.chained == "XX"
+
+
+def test_file_is_readable_validator_not_exists(tmpdir):
+    validator = FileIsReadableValidator()
+    with pytest.raises(ConfigurationError) as e:
+        validator(tmpdir.join("doesnotexist").strpath, "path")
+    assert "does not exist" in e.value.args[0]
+
+
+def test_file_is_readable_validator_not_a_file(tmpdir):
+    validator = FileIsReadableValidator()
+    with pytest.raises(ConfigurationError) as e:
+        validator(tmpdir.strpath, "path")
+    assert "is not a file" in e.value.args[0]
+
+
+@pytest.mark.skipif(platform.system() == "Windows", reason="os.access() doesn't seem to work as we expect on Windows")
+def test_file_is_readable_validator_not_readable(tmpdir):
+    p = tmpdir.join("nonreadable")
+    p.write("")
+    os.chmod(p.strpath, stat.S_IWRITE)
+    validator = FileIsReadableValidator()
+    with pytest.raises(ConfigurationError) as e:
+        validator(p.strpath, "path")
+    assert "is not readable" in e.value.args[0]
+
+
+def test_file_is_readable_validator_all_good(tmpdir):
+    p = tmpdir.join("readable")
+    p.write("")
+    validator = FileIsReadableValidator()
+    assert validator(p.strpath, "path") == p.strpath