feat: add smtp and smtps services

README.md

@@ -12,7 +12,7 @@
   <p align="center" width="50">
 
   [![GitHub Repo stars](https://img.shields.io/github/stars/lachlanharrisdev/gonetsim?style=social)](https://github.com/lachlanharrisdev/gonetsim/stargazers)
-  [![GitHub](https://img.shields.io/github/license/lachlanharrisdev/gonetsim)](https://github.com/lachlanharrisdev/gonetsim/?tab=Apache-2.0-1-ov-file)
+  [![GitHub](https://img.shields.io/github/license/lachlanharrisdev/gonetsim)](https://github.com/lachlanharrisdev/gonetsim?tab=Apache-2.0-1-ov-file)
   [![GitHub go.mod Go version](https://img.shields.io/github/go-mod/go-version/lachlanharrisdev/gonetsim)](https://github.com/lachlanharrisdev/gonetsim/)
   [![GitHub CI Status](https://img.shields.io/github/actions/workflow/status/lachlanharrisdev/gonetsim/ci.yaml?branch=main&label=CI)](https://github.com/lachlanharrisdev/gonetsim/actions)<br/>
   [![GitHub Release Status](https://img.shields.io/github/v/release/lachlanharrisdev/gonetsim)](https://github.com/lachlanharrisdev/gonetsim/releases/latest)
@@ -50,6 +50,9 @@ Alternatively, you can specify an individual service to run
 gonetsim dns
 gonetsim http
 gonetsim https
+gonetsim smtp
+gonetsim smtps
+...
 ```
 
 <br/>

cmd/root.go

@@ -11,6 +11,7 @@ import (
 	"github.com/lachlanharrisdev/gonetsim/internal/httpserver"
 	"github.com/lachlanharrisdev/gonetsim/internal/observability"
 	"github.com/lachlanharrisdev/gonetsim/internal/service"
+	"github.com/lachlanharrisdev/gonetsim/internal/smtpserver"
 	"github.com/lachlanharrisdev/gonetsim/internal/utils"
 	"github.com/spf13/cobra"
 )
@@ -19,7 +20,7 @@ var rootConfigPath string
 
 var rootCmd = &cobra.Command{
 	Use:           "gonetsim",
-	Short:         "Network service simulator (dns + http + https)",
+	Short:         "Starts all configured services",
 	Args:          cobra.NoArgs,
 	SilenceUsage:  true,
 	SilenceErrors: true,
@@ -93,7 +94,42 @@ var rootCmd = &cobra.Command{
 			manager.Add(httpserver.NewHTTPSService(conf, tlsOpts))
 		}
 
-		logger.Info("running", "dns", cfg.DNS.Enabled, "http", cfg.HTTP.Enabled, "https", cfg.HTTPS.Enabled)
+		if cfg.SMTP.Enabled {
+			listen, err := parseAddrPort(cfg.SMTP.Addr)
+			if err != nil {
+				return fmt.Errorf("smtp.addr: %w", err)
+			}
+			conf := smtpserver.Config{
+				Addr:              listen,
+				Domain:            cfg.SMTP.Domain,
+				WriteTimeout:      cfg.SMTP.WriteTimeout,
+				ReadTimeout:       cfg.SMTP.ReadTimeout,
+				MaxMessageBytes:   cfg.SMTP.MaxMessageBytes,
+				MaxRecipients:     cfg.SMTP.MaxRecipients,
+				AllowInsecureAuth: cfg.SMTP.AllowInsecureAuth,
+			}
+			manager.Add(smtpserver.NewSMTPService(conf))
+		}
+
+		if cfg.SMTPS.Enabled {
+			listen, err := parseAddrPort(cfg.SMTPS.Addr)
+			if err != nil {
+				return fmt.Errorf("smtps.addr: %w", err)
+			}
+			conf := smtpserver.Config{
+				Addr:              listen,
+				Domain:            cfg.SMTPS.Domain,
+				WriteTimeout:      cfg.SMTPS.WriteTimeout,
+				ReadTimeout:       cfg.SMTPS.ReadTimeout,
+				MaxMessageBytes:   cfg.SMTPS.MaxMessageBytes,
+				MaxRecipients:     cfg.SMTPS.MaxRecipients,
+				AllowInsecureAuth: cfg.SMTPS.AllowInsecureAuth,
+			}
+			tlsOpts := smtpserver.TLSOptions{CertFile: cfg.SMTPS.Cert, KeyFile: cfg.SMTPS.Key}
+			manager.Add(smtpserver.NewSMTPSService(conf, tlsOpts))
+		}
+
+		logger.Info("running", "dns", cfg.DNS.Enabled, "http", cfg.HTTP.Enabled, "https", cfg.HTTPS.Enabled, "smtp", cfg.SMTP.Enabled, "smtps", cfg.SMTPS.Enabled)
 
 		return manager.RunAll(runCtx)
 	},

cmd/smtp.go

@@ -0,0 +1,71 @@
+package cmd
+
+import (
+	"context"
+	"log/slog"
+	"time"
+
+	appconfig "github.com/lachlanharrisdev/gonetsim/internal/config"
+	"github.com/lachlanharrisdev/gonetsim/internal/observability"
+	"github.com/lachlanharrisdev/gonetsim/internal/service"
+	"github.com/lachlanharrisdev/gonetsim/internal/smtpserver"
+	"github.com/lachlanharrisdev/gonetsim/internal/utils"
+	"github.com/spf13/cobra"
+)
+
+var (
+	smtpAddr              string
+	smtpDomain            string
+	smtpWriteTimeout      int
+	smtpReadTimeout       int
+	smtpMaxMessageBytes   int
+	smtpMaxRecipients     int
+	smtpAllowInsecureAuth bool
+)
+
+var smtpCmd = &cobra.Command{
+	Use:   "smtp",
+	Short: "Run an SMTP server (insecure, no TLS)",
+	RunE: func(cmd *cobra.Command, args []string) error {
+		listen, err := parseAddrPort(smtpAddr)
+		if err != nil {
+			return err
+		}
+
+		ctx, stop := utils.SignalContext(context.Background())
+		defer stop()
+
+		logger, err := observability.NewLogger(appconfig.Default().Logging)
+		if err != nil {
+			return err
+		}
+		slog.SetDefault(logger)
+		manager := service.NewManager(5*time.Second, logger)
+
+		return manager.RunSingleService(ctx,
+			smtpserver.NewSMTPService(
+				smtpserver.Config{
+					Addr:              listen,
+					Domain:            smtpDomain,
+					WriteTimeout:      smtpWriteTimeout,
+					ReadTimeout:       smtpReadTimeout,
+					MaxMessageBytes:   smtpMaxMessageBytes,
+					MaxRecipients:     smtpMaxRecipients,
+					AllowInsecureAuth: smtpAllowInsecureAuth,
+				},
+			),
+		)
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(smtpCmd)
+
+	smtpCmd.Flags().StringVar(&smtpAddr, "listen", ":1025", "listen address")
+	smtpCmd.Flags().StringVar(&smtpDomain, "domain", "localhost", "SMTP server domain")
+	smtpCmd.Flags().IntVar(&smtpWriteTimeout, "write-timeout", 10, "write timeout in seconds")
+	smtpCmd.Flags().IntVar(&smtpReadTimeout, "read-timeout", 10, "read timeout in seconds")
+	smtpCmd.Flags().IntVar(&smtpMaxMessageBytes, "max-message-bytes", 1024*1024, "max message size in bytes")
+	smtpCmd.Flags().IntVar(&smtpMaxRecipients, "max-recipients", 50, "maximum number of recipients per message")
+	smtpCmd.Flags().BoolVar(&smtpAllowInsecureAuth, "allow-insecure-auth", true, "allow authentication without TLS")
+}

cmd/smtps.go

@@ -0,0 +1,76 @@
+package cmd
+
+import (
+	"context"
+	"log/slog"
+	"time"
+
+	appconfig "github.com/lachlanharrisdev/gonetsim/internal/config"
+	"github.com/lachlanharrisdev/gonetsim/internal/observability"
+	"github.com/lachlanharrisdev/gonetsim/internal/service"
+	"github.com/lachlanharrisdev/gonetsim/internal/smtpserver"
+	"github.com/lachlanharrisdev/gonetsim/internal/utils"
+	"github.com/spf13/cobra"
+)
+
+var (
+	smtpsAddr              string
+	smtpsDomain            string
+	smtpsWriteTimeout      int
+	smtpsReadTimeout       int
+	smtpsMaxMessageBytes   int
+	smtpsMaxRecipients     int
+	smtpsAllowInsecureAuth bool
+	smtpsCert              string
+	smtpsKey               string
+)
+
+var smtpsCmd = &cobra.Command{
+	Use:   "smtps",
+	Short: "Run an SMTPS server (secure SMTP with TLS)",
+	RunE: func(cmd *cobra.Command, args []string) error {
+		listen, err := parseAddrPort(smtpsAddr)
+		if err != nil {
+			return err
+		}
+
+		ctx, stop := utils.SignalContext(context.Background())
+		defer stop()
+
+		logger, err := observability.NewLogger(appconfig.Default().Logging)
+		if err != nil {
+			return err
+		}
+		slog.SetDefault(logger)
+		manager := service.NewManager(5*time.Second, logger)
+
+		return manager.RunSingleService(ctx,
+			smtpserver.NewSMTPSService(
+				smtpserver.Config{
+					Addr:              listen,
+					Domain:            smtpsDomain,
+					WriteTimeout:      smtpsWriteTimeout,
+					ReadTimeout:       smtpsReadTimeout,
+					MaxMessageBytes:   smtpsMaxMessageBytes,
+					MaxRecipients:     smtpsMaxRecipients,
+					AllowInsecureAuth: smtpsAllowInsecureAuth,
+				},
+				smtpserver.TLSOptions{CertFile: smtpsCert, KeyFile: smtpsKey},
+			),
+		)
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(smtpsCmd)
+
+	smtpsCmd.Flags().StringVar(&smtpsAddr, "listen", ":1465", "listen address")
+	smtpsCmd.Flags().StringVar(&smtpsDomain, "domain", "localhost", "SMTP server domain")
+	smtpsCmd.Flags().IntVar(&smtpsWriteTimeout, "write-timeout", 10, "write timeout in seconds")
+	smtpsCmd.Flags().IntVar(&smtpsReadTimeout, "read-timeout", 10, "read timeout in seconds")
+	smtpsCmd.Flags().IntVar(&smtpsMaxMessageBytes, "max-message-bytes", 1024*1024, "max message size in bytes")
+	smtpsCmd.Flags().IntVar(&smtpsMaxRecipients, "max-recipients", 50, "maximum number of recipients per message")
+	smtpsCmd.Flags().BoolVar(&smtpsAllowInsecureAuth, "allow-insecure-auth", false, "allow authentication without TLS")
+	smtpsCmd.Flags().StringVar(&smtpsCert, "cert", "", "path to TLS cert PEM (optional; defaults to ephemeral self-signed)")
+	smtpsCmd.Flags().StringVar(&smtpsKey, "key", "", "path to TLS key PEM (optional; defaults to ephemeral self-signed)")
+}

docker/docker-compose.yml

@@ -16,6 +16,8 @@ services:
       - "5353:5353/tcp"
       - "8080:8080"
       - "8443:8443"
+      - "1025:1025"
+      - "1465:1465"
 
     # by default the image includes a config at /etc/gonetsim/gonetsim.toml.
     # to use a custom config, mount a read-only file over it:

go.mod

@@ -3,6 +3,9 @@ module github.com/lachlanharrisdev/gonetsim
 go 1.26.1
 
 require (
+	github.com/emersion/go-sasl v0.0.0-20241020182733-b788ff22d5a6
+	github.com/emersion/go-smtp v0.24.0
+	github.com/fatih/color v1.19.0
 	github.com/knadh/koanf/parsers/toml/v2 v2.2.0
 	github.com/knadh/koanf/providers/file v1.2.1
 	github.com/knadh/koanf/providers/structs v1.0.0
@@ -15,7 +18,6 @@ require (
 )
 
 require (
-	github.com/fatih/color v1.19.0 // indirect
 	github.com/fatih/structs v1.1.0 // indirect
 	github.com/fsnotify/fsnotify v1.9.0 // indirect
 	github.com/go-viper/mapstructure/v2 v2.4.0 // indirect

go.sum

@@ -1,6 +1,10 @@
 github.com/cpuguy83/go-md2man/v2 v2.0.6/go.mod h1:oOW0eioCTA6cOiMLiUPZOpcVxMig6NIQQ7OS05n1F4g=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/emersion/go-sasl v0.0.0-20241020182733-b788ff22d5a6 h1:oP4q0fw+fOSWn3DfFi4EXdT+B+gTtzx8GC9xsc26Znk=
+github.com/emersion/go-sasl v0.0.0-20241020182733-b788ff22d5a6/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
+github.com/emersion/go-smtp v0.24.0 h1:g6AfoF140mvW0vLNPD/LuCBLEAdlxOjIXqbIkJIS6Wk=
+github.com/emersion/go-smtp v0.24.0/go.mod h1:ZtRRkbTyp2XTHCA+BmyTFTrj8xY4I+b4McvHxCU2gsQ=
 github.com/fatih/color v1.19.0 h1:Zp3PiM21/9Ld6FzSKyL5c/BULoe/ONr9KlbYVOfG8+w=
 github.com/fatih/color v1.19.0/go.mod h1:zNk67I0ZUT1bEGsSGyCZYZNrHuTkJJB+r6Q9VuMi0LE=
 github.com/fatih/structs v1.1.0 h1:Q7juDM0QtcnhCpeyLGQKyg4TOIghuNXrkL32pHAUMxo=
@@ -54,8 +58,6 @@ golang.org/x/net v0.48.0/go.mod h1:+ndRgGjkh8FGtu1w1FGbEC31if4VrNVMuKTgcAAnQRY=
 golang.org/x/sync v0.19.0 h1:vV+1eWNmZ5geRlYjzm2adRgW2/mcpevXNg50YZtPCE4=
 golang.org/x/sync v0.19.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.39.0 h1:CvCKL8MeisomCi6qNZ+wbb0DN9E5AATixKsvNtMoMFk=
-golang.org/x/sys v0.39.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
 golang.org/x/sys v0.42.0 h1:omrd2nAlyT5ESRdCLYdm3+fMfNFE/+Rf4bDIQImRJeo=
 golang.org/x/sys v0.42.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
 golang.org/x/tools v0.40.0 h1:yLkxfA+Qnul4cs9QA3KnlFu0lVmd8JJfoq+E41uSutA=

internal/config/config.go

@@ -29,6 +29,8 @@ type Config struct {
 	DNS     DNSConfig     `koanf:"dns"`
 	HTTP    HTTPConfig    `koanf:"http"`
 	HTTPS   HTTPSConfig   `koanf:"https"`
+	SMTP    SMTPConfig    `koanf:"smtp"`
+	SMTPS   SMTPSConfig   `koanf:"smtps"`
 	Logging LoggingConfig `koanf:"logging"`
 }
 
@@ -62,6 +64,30 @@ type HTTPSConfig struct {
 	Key     string `koanf:"key"`
 }
 
+type SMTPConfig struct {
+	Enabled           bool   `koanf:"enabled"`
+	Addr              string `koanf:"addr"`                // ":1025"
+	Domain            string `koanf:"domain"`              // "localhost"
+	WriteTimeout      int    `koanf:"write_timeout"`       // 10 seconds
+	ReadTimeout       int    `koanf:"read_timeout"`        // 10 seconds
+	MaxMessageBytes   int    `koanf:"max_message_bytes"`   // 1024 * 1024
+	MaxRecipients     int    `koanf:"max_recipients"`      // 50
+	AllowInsecureAuth bool   `koanf:"allow_insecure_auth"` // true
+}
+
+type SMTPSConfig struct {
+	Enabled           bool   `koanf:"enabled"`
+	Addr              string `koanf:"addr"`                // ":1465"
+	Domain            string `koanf:"domain"`              // "localhost"
+	WriteTimeout      int    `koanf:"write_timeout"`       // 10 seconds
+	ReadTimeout       int    `koanf:"read_timeout"`        // 10 seconds
+	MaxMessageBytes   int    `koanf:"max_message_bytes"`   // 1024 * 1024
+	MaxRecipients     int    `koanf:"max_recipients"`      // 50
+	AllowInsecureAuth bool   `koanf:"allow_insecure_auth"` // false (secure)
+	Cert              string `koanf:"cert"`                // Optional TLS cert
+	Key               string `koanf:"key"`                 // Optional TLS key
+}
+
 type LoggingConfig struct {
 	LogFormat string `koanf:"format"`
 	Level     string `koanf:"level"`
@@ -91,6 +117,26 @@ func Default() Config {
 			Listen:  ":8443",
 			Status:  200,
 		},
+		SMTP: SMTPConfig{
+			Enabled:           true,
+			Addr:              ":1025",
+			Domain:            "localhost",
+			WriteTimeout:      10,
+			ReadTimeout:       10,
+			MaxMessageBytes:   1024 * 1024,
+			MaxRecipients:     50,
+			AllowInsecureAuth: true,
+		},
+		SMTPS: SMTPSConfig{
+			Enabled:           false,
+			Addr:              ":1465",
+			Domain:            "localhost",
+			WriteTimeout:      10,
+			ReadTimeout:       10,
+			MaxMessageBytes:   1024 * 1024,
+			MaxRecipients:     50,
+			AllowInsecureAuth: false,
+		},
 		Logging: LoggingConfig{
 			LogFormat: "text",
 			Level:     "info",
@@ -130,7 +176,22 @@ func (c Config) Validate() error {
 		}
 	}
 
-	if !c.DNS.Enabled && !c.HTTP.Enabled && !c.HTTPS.Enabled {
+	if c.SMTP.Enabled {
+		if c.SMTP.Addr == "" {
+			return errors.New("smtp.addr is required when smtp.enabled=true")
+		}
+	}
+
+	if c.SMTPS.Enabled {
+		if c.SMTPS.Addr == "" {
+			return errors.New("smtps.addr is required when smtps.enabled=true")
+		}
+		if (c.SMTPS.Cert == "") != (c.SMTPS.Key == "") {
+			return errors.New("smtps.cert and smtps.key must be set together")
+		}
+	}
+
+	if !c.DNS.Enabled && !c.HTTP.Enabled && !c.HTTPS.Enabled && !c.SMTP.Enabled && !c.SMTPS.Enabled {
 		return errors.New("at least one service must be enabled")
 	}
 

internal/config/default_config.toml

@@ -47,8 +47,25 @@ listen = ":8443"
 # Status code to return for all requests. 0 means default (200).
 status = 200
 
-# Optional TLS cert/key paths (PEM). If both are empty, gonetsim generates an
-# ephemeral self-signed certificate at startup.
+[smtp]
+enabled = true
+addr = ":1025"
+domain = "localhost"
+write_timeout = 10
+read_timeout = 10
+max_message_bytes = 1048576
+max_recipients = 50
+allow_insecure_auth = true
+
+[smtps]
+enabled = false
+addr = ":1465"
+domain = "localhost"
+write_timeout = 10
+read_timeout = 10
+max_message_bytes = 1048576
+max_recipients = 50
+allow_insecure_auth = false
 cert = ""
 key = ""