[7.15](backport #27178) libbeat/cmd/instance: ensure test config file…

… has appropriate permissions (#27797)

* libbeat/cmd/instance: ensure test config file has appropriate permissions (#27178)

Git does not store r/w permissions, instead depending on the host system's
umask. On some systems the default umask is 0o002, meaning that the test
config file is checked out with g+w permission, causing the test to fail.

This change ensures that the test config is owner-exclusive write before
running the test. It also adds checks to currently ineffective error
assignments.

(cherry picked from commit 627b7a8)

# Conflicts:
#	libbeat/cmd/instance/beat_test.go

* libbeat/cmd/instance: resolve backport conflict

Co-authored-by: Dan Kortschak <[email protected]>
Co-authored-by: Dan Kortschak <[email protected]>

libbeat/cmd/instance/beat_test.go

@@ -78,16 +78,30 @@ func TestInitKibanaConfig(t *testing.T) {
  assert.Equal(t, "testidx", b.Info.IndexPrefix)
  assert.Equal(t, "0.9", b.Info.Version)
 
- cfg, err := cfgfile.Load("../test/filebeat_test.yml", nil)
+ const configPath = "../test/filebeat_test.yml"
+
+ // Ensure that the config has owner-exclusive write permissions.
+ // This is necessary on some systems which have a default umask
+ // of 0o002, meaning that files are checked out by git with mode
+ // 0o664. This would cause cfgfile.Load to fail.
+ err = os.Chmod(configPath, 0o644)
+ assert.NoError(t, err)
+
+ cfg, err := cfgfile.Load(configPath, nil)
+ assert.NoError(t, err)
  err = cfg.Unpack(&b.Config)
  assert.NoError(t, err)
 
  kibanaConfig, err := initKibanaConfig(b.Config)
  assert.NoError(t, err)
  username, err := kibanaConfig.String("username", -1)
+ assert.NoError(t, err)
  password, err := kibanaConfig.String("password", -1)
+ assert.NoError(t, err)
  protocol, err := kibanaConfig.String("protocol", -1)
+ assert.NoError(t, err)
  host, err := kibanaConfig.String("host", -1)
+ assert.NoError(t, err)
 
  assert.Equal(t, "elastic-test-username", username)
  assert.Equal(t, "elastic-test-password", password)