VAULT-24452: audit refactor (#26460)

* Refactor audit code into audit package
* remove builtin/audit
* removed unrequired files

audit/backend_file.go

@@ -0,0 +1,154 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: BUSL-1.1
+
+package audit
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+
+	"github.com/hashicorp/eventlogger"
+	"github.com/hashicorp/vault/internal/observability/event"
+)
+
+const (
+	stdout  = "stdout"
+	discard = "discard"
+
+	optionFilePath = "file_path"
+	optionMode     = "mode"
+)
+
+var _ Backend = (*FileBackend)(nil)
+
+type FileBackend struct {
+	*backend
+}
+
+// NewFileBackend provides a wrapper to support the expectation elsewhere in Vault that
+// all audit backends can be created via a factory that returns an interface (Backend).
+func NewFileBackend(conf *BackendConfig, headersConfig HeaderFormatter) (be Backend, err error) {
+	be, err = newFileBackend(conf, headersConfig)
+	return
+}
+
+// newFileBackend creates a backend and configures all nodes including a file sink.
+func newFileBackend(conf *BackendConfig, headersConfig HeaderFormatter) (*FileBackend, error) {
+	if headersConfig == nil || reflect.ValueOf(headersConfig).IsNil() {
+		return nil, fmt.Errorf("nil header formatter: %w", ErrInvalidParameter)
+	}
+	if conf == nil {
+		return nil, fmt.Errorf("nil config: %w", ErrInvalidParameter)
+	}
+	if err := conf.Validate(); err != nil {
+		return nil, err
+	}
+
+	// Get file path from config or fall back to the old option ('path') for compatibility
+	// (see commit bac4fe0799a372ba1245db642f3f6cd1f1d02669).
+	var filePath string
+	if p, ok := conf.Config[optionFilePath]; ok {
+		filePath = p
+	} else if p, ok = conf.Config["path"]; ok {
+		filePath = p
+	} else {
+		return nil, fmt.Errorf("%q is required: %w", optionFilePath, ErrExternalOptions)
+	}
+
+	bec, err := newBackend(headersConfig, conf)
+	if err != nil {
+		return nil, err
+	}
+	b := &FileBackend{backend: bec}
+
+	// normalize file path if configured for stdout
+	if strings.EqualFold(filePath, stdout) {
+		filePath = stdout
+	}
+	if strings.EqualFold(filePath, discard) {
+		filePath = discard
+	}
+
+	// Configure the sink.
+	cfg, err := newFormatterConfig(headersConfig, conf.Config)
+	if err != nil {
+		return nil, err
+	}
+
+	var opt []event.Option
+	if mode, ok := conf.Config[optionMode]; ok {
+		opt = append(opt, event.WithFileMode(mode))
+	}
+
+	err = b.configureSinkNode(conf.MountPath, filePath, cfg.requiredFormat, opt...)
+	if err != nil {
+		return nil, err
+	}
+
+	return b, nil
+}
+
+// configureSinkNode is used internally by FileBackend to create and configure the
+// sink node on the backend.
+func (b *FileBackend) configureSinkNode(name string, filePath string, format format, opt ...event.Option) error {
+	name = strings.TrimSpace(name)
+	if name == "" {
+		return fmt.Errorf("name is required: %w", ErrExternalOptions)
+	}
+
+	filePath = strings.TrimSpace(filePath)
+	if filePath == "" {
+		return fmt.Errorf("file path is required: %w", ErrExternalOptions)
+	}
+
+	sinkNodeID, err := event.GenerateNodeID()
+	if err != nil {
+		return fmt.Errorf("error generating random NodeID for sink node: %w: %w", ErrInternal, err)
+	}
+
+	// normalize file path if configured for stdout or discard
+	if strings.EqualFold(filePath, stdout) {
+		filePath = stdout
+	} else if strings.EqualFold(filePath, discard) {
+		filePath = discard
+	}
+
+	var sinkNode eventlogger.Node
+	var sinkName string
+
+	switch filePath {
+	case stdout:
+		sinkName = stdout
+		sinkNode, err = event.NewStdoutSinkNode(format.String())
+	case discard:
+		sinkName = discard
+		sinkNode = event.NewNoopSink()
+	default:
+		// The NewFileSink function attempts to open the file and will return an error if it can't.
+		sinkName = name
+		sinkNode, err = event.NewFileSink(filePath, format.String(), opt...)
+	}
+	if err != nil {
+		return fmt.Errorf("file sink creation failed for path %q: %w", filePath, err)
+	}
+
+	// Wrap the sink node with metrics middleware
+	err = b.wrapMetrics(sinkName, sinkNodeID, sinkNode)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Reload will trigger the reload action on the sink node for this backend.
+func (b *FileBackend) Reload() error {
+	for _, n := range b.nodeMap {
+		if n.Type() == eventlogger.NodeTypeSink {
+			return n.Reopen()
+		}
+	}
+
+	return nil
+}