Cherry-pick #10706 to 6.7: Initialize Paths before loading the keysto…

…re (#11497)

Cherry-pick of PR #10706  to 6.7 branch. Original message: 

The paths were incorrectly initialized meaning that instead of creating
the keystore in the data directory it was created next to the binary.

The problem was the call to `paths.InitPaths()` was done after loading
the keystore, this was causing a chicken and egg situation and
`paths.Resolve(path.Data, "hello")` was returning "hello" instead of
`data/hello`.

To solve that situation we do a partial extract of the configuration,
just enough to initialize the paths and we move on to the keystore and
the complete unpack.

CHANGELOG.next.asciidoc

@@ -10,6 +10,8 @@ https://github.com/elastic/beats/compare/v6.7.0...6.x[Check the HEAD diff]
 
 *Affecting all Beats*
 
+- Initialize the Paths before the keystore and save the keystore into `data/{beatname}.keystore`. {pull}10706[10706]
+
 *Auditbeat*
 
 *Filebeat*

libbeat/cmd/instance/beat.go

@@ -562,6 +562,10 @@ func (b *Beat) configure(settings Settings) error {
 		return fmt.Errorf("error loading config file: %v", err)
 	}
 
+	if err := initPaths(cfg); err != nil {
+		return err
+	}
+
 	// We have to initialize the keystore before any unpack or merging the cloud
 	// options.
 	store, err := LoadKeystore(cfg, b.Info.Beat)
@@ -599,11 +603,6 @@ func (b *Beat) configure(settings Settings) error {
 		b.Info.Name = name
 	}
 
-	err = paths.InitPaths(&b.Config.Path)
-	if err != nil {
-		return fmt.Errorf("error setting default paths: %v", err)
-	}
-
 	if err := configure.Logging(b.Info.Beat, b.Config.Logging); err != nil {
 		return fmt.Errorf("error initializing logging: %v", err)
 	}
@@ -1005,3 +1004,22 @@ func LoadKeystore(cfg *common.Config, name string) (keystore.Keystore, error) {
 	defaultPathConfig := paths.Resolve(paths.Data, fmt.Sprintf("%s.keystore", name))
 	return keystore.Factory(keystoreCfg, defaultPathConfig)
 }
+
+func initPaths(cfg *common.Config) error {
+	// To Fix the chicken-egg problem with the Keystore and the loading of the configuration
+	// files we are doing a partial unpack of the configuration file and only take into consideration
+	// the paths field. After we will unpack the complete configuration and keystore reference
+	// will be correctly replaced.
+	partialConfig := struct {
+		Path paths.Path `config:"path"`
+	}{}
+
+	if err := cfg.Unpack(&partialConfig); err != nil {
+		return fmt.Errorf("error extracting default paths: %+v", err)
+	}
+
+	if err := paths.InitPaths(&partialConfig.Path); err != nil {
+		return fmt.Errorf("error setting default paths: %+v", err)
+	}
+	return nil
+}