VAULT-17075: syslog sink node (#21859)

* syslog sink added, options + tests added, tweaks to file sink comments

* defaults for syslog options

internal/observability/event/audit_sink_file.go

@@ -34,6 +34,7 @@ type AuditFileSink struct {
 }
 
 // NewAuditFileSink should be used to create a new AuditFileSink.
+// Accepted options: WithFileMode and WithPrefix.
 func NewAuditFileSink(path string, format auditFormat, opt ...Option) (*AuditFileSink, error) {
 	const op = "event.NewAuditFileSink"
 
@@ -110,12 +111,12 @@ func (f *AuditFileSink) Process(ctx context.Context, e *eventlogger.Event) (*eve
 		return nil, fmt.Errorf("%s: unable to retrieve event formatted as %q", op, f.format)
 	}
 
-	buffer := bytes.NewBuffer(formatted)
-	err := f.log(buffer)
+	err := f.log(formatted)
 	if err != nil {
 		return nil, fmt.Errorf("%s: error writing file for audit sink: %w", op, err)
 	}
 
+	// return nil for the event to indicate the pipeline is complete.
 	return nil, nil
 }
 
@@ -145,7 +146,7 @@ func (f *AuditFileSink) Reopen() error {
 	return f.open()
 }
 
-// Type is used to define which type of node AuditFileSink is.
+// Type describes the type of this node (sink).
 func (f *AuditFileSink) Type() eventlogger.NodeType {
 	return eventlogger.NodeTypeSink
 }
@@ -189,13 +190,13 @@ func (f *AuditFileSink) open() error {
 
 // log writes the buffer to the file.
 // It acquires a lock on the file to do this.
-func (f *AuditFileSink) log(buf *bytes.Buffer) error {
+func (f *AuditFileSink) log(data []byte) error {
 	const op = "event.(AuditFileSink).log"
 
 	f.fileLock.Lock()
 	defer f.fileLock.Unlock()
 
-	reader := bytes.NewReader(buf.Bytes())
+	reader := bytes.NewReader(data)
 
 	var writer io.Writer
 	switch {

internal/observability/event/audit_sink_syslog.go

@@ -0,0 +1,75 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+package event
+
+import (
+	"context"
+	"fmt"
+
+	gsyslog "github.com/hashicorp/go-syslog"
+
+	"github.com/hashicorp/eventlogger"
+)
+
+// AuditSyslogSink is a sink node which handles writing audit events to syslog.
+type AuditSyslogSink struct {
+	format auditFormat
+	logger gsyslog.Syslogger
+}
+
+// NewAuditSyslogSink should be used to create a new AuditSyslogSink.
+// Accepted options: WithFacility and WithTag.
+func NewAuditSyslogSink(format auditFormat, opt ...Option) (*AuditSyslogSink, error) {
+	const op = "event.NewAuditSyslogSink"
+
+	opts, err := getOpts(opt...)
+	if err != nil {
+		return nil, fmt.Errorf("%s: error applying options: %w", op, err)
+	}
+
+	logger, err := gsyslog.NewLogger(gsyslog.LOG_INFO, opts.withFacility, opts.withTag)
+	if err != nil {
+		return nil, fmt.Errorf("%s: error creating syslogger: %w", op, err)
+	}
+
+	return &AuditSyslogSink{format: format, logger: logger}, nil
+}
+
+// Process handles writing the event to the syslog.
+func (s *AuditSyslogSink) Process(ctx context.Context, e *eventlogger.Event) (*eventlogger.Event, error) {
+	const op = "event.(AuditSyslogSink).Process"
+
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	default:
+	}
+
+	if e == nil {
+		return nil, fmt.Errorf("%s: event is nil: %w", op, ErrInvalidParameter)
+	}
+
+	formatted, found := e.Format(s.format.String())
+	if !found {
+		return nil, fmt.Errorf("%s: unable to retrieve event formatted as %q", op, s.format)
+	}
+
+	_, err := s.logger.Write(formatted)
+	if err != nil {
+		return nil, fmt.Errorf("%s: error writing to syslog: %w", op, err)
+	}
+
+	// return nil for the event to indicate the pipeline is complete.
+	return nil, nil
+}
+
+// Reopen is a no-op for a syslog sink.
+func (s *AuditSyslogSink) Reopen() error {
+	return nil
+}
+
+// Type describes the type of this node (sink).
+func (s *AuditSyslogSink) Type() eventlogger.NodeType {
+	return eventlogger.NodeTypeSink
+}

internal/observability/event/options.go

@@ -25,12 +25,16 @@ type options struct {
 	withFormat   auditFormat
 	withFileMode *os.FileMode
 	withPrefix   string
+	withFacility string
+	withTag      string
 }
 
 // getDefaultOptions returns options with their default values.
 func getDefaultOptions() options {
 	return options{
-		withNow: time.Now(),
+		withNow:      time.Now(),
+		withFacility: "AUTH",
+		withTag:      "vault",
 	}
 }
 
@@ -143,12 +147,11 @@ func WithFormat(format string) Option {
 // applied, but it will not return an error in those circumstances.
 func WithFileMode(mode string) Option {
 	return func(o *options) error {
-		// Clear up whitespace before attempting to parse
+		// If supplied file mode is empty, just return early without setting anything.
+		// We can assume that this option was called by something that didn't
+		// parse the incoming value, perhaps from a config map etc.
 		mode = strings.TrimSpace(mode)
 		if mode == "" {
-			// If supplied file mode is empty, just return early without setting anything.
-			// We can assume that this option was called by something that didn't
-			// parse the incoming value, perhaps from a config map etc.
 			return nil
 		}
 
@@ -175,3 +178,29 @@ func WithPrefix(prefix string) Option {
 		return nil
 	}
 }
+
+// WithFacility provides an option to represent a 'facility' for a syslog sink.
+func WithFacility(facility string) Option {
+	return func(o *options) error {
+		facility = strings.TrimSpace(facility)
+
+		if facility != "" {
+			o.withFacility = facility
+		}
+
+		return nil
+	}
+}
+
+// WithTag provides an option to represent a 'tag' for a syslog sink.
+func WithTag(tag string) Option {
+	return func(o *options) error {
+		tag = strings.TrimSpace(tag)
+
+		if tag != "" {
+			o.withTag = tag
+		}
+
+		return nil
+	}
+}

internal/observability/event/options_test.go

@@ -197,6 +197,82 @@ func TestOptions_WithID(t *testing.T) {
 	}
 }
 
+// TestOptions_WithFacility exercises WithFacility option to ensure it performs as expected.
+func TestOptions_WithFacility(t *testing.T) {
+	tests := map[string]struct {
+		Value         string
+		ExpectedValue string
+	}{
+		"empty": {
+			Value:         "",
+			ExpectedValue: "",
+		},
+		"whitespace": {
+			Value:         "    ",
+			ExpectedValue: "",
+		},
+		"value": {
+			Value:         "juan",
+			ExpectedValue: "juan",
+		},
+		"spacey-value": {
+			Value:         "   juan   ",
+			ExpectedValue: "juan",
+		},
+	}
+
+	for name, tc := range tests {
+		name := name
+		tc := tc
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+			options := &options{}
+			applyOption := WithFacility(tc.Value)
+			err := applyOption(options)
+			require.NoError(t, err)
+			require.Equal(t, tc.ExpectedValue, options.withFacility)
+		})
+	}
+}
+
+// TestOptions_WithTag exercises WithTag option to ensure it performs as expected.
+func TestOptions_WithTag(t *testing.T) {
+	tests := map[string]struct {
+		Value         string
+		ExpectedValue string
+	}{
+		"empty": {
+			Value:         "",
+			ExpectedValue: "",
+		},
+		"whitespace": {
+			Value:         "    ",
+			ExpectedValue: "",
+		},
+		"value": {
+			Value:         "juan",
+			ExpectedValue: "juan",
+		},
+		"spacey-value": {
+			Value:         "   juan   ",
+			ExpectedValue: "juan",
+		},
+	}
+
+	for name, tc := range tests {
+		name := name
+		tc := tc
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+			options := &options{}
+			applyOption := WithTag(tc.Value)
+			err := applyOption(options)
+			require.NoError(t, err)
+			require.Equal(t, tc.ExpectedValue, options.withTag)
+		})
+	}
+}
+
 // TestOptions_WithFileMode exercises WithFileMode option to ensure it performs as expected.
 func TestOptions_WithFileMode(t *testing.T) {
 	tests := map[string]struct {
@@ -266,6 +342,8 @@ func TestOptions_Default(t *testing.T) {
 	require.NotNil(t, opts)
 	require.True(t, time.Now().After(opts.withNow))
 	require.False(t, opts.withNow.IsZero())
+	require.Equal(t, "AUTH", opts.withFacility)
+	require.Equal(t, "vault", opts.withTag)
 }
 
 // TestOptions_Opts exercises getOpts with various Option values.