feat: initial implementation of config file support (#79)

* feat: initial implementation of config file support

Author: evgeniy-scherbina

cli/cli.go

@@ -2,6 +2,7 @@ package cli
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"log"
 	"log/slog"
@@ -24,12 +25,14 @@ import (
 
 // Config holds all configuration for the CLI
 type Config struct {
-	AllowStrings []string
-	LogLevel     string
-	LogDir       string
-	ProxyPort    int64
-	PprofEnabled bool
-	PprofPort    int64
+	Config          serpent.YAMLConfigPath `yaml:"-"`
+	AllowListStrings serpent.StringArray   `yaml:"allowlist"` // From config file
+	AllowStrings    serpent.StringArray    `yaml:"-"`       // From CLI flags only
+	LogLevel        serpent.String         `yaml:"log_level"`
+	LogDir          serpent.String         `yaml:"log_dir"`
+	ProxyPort       serpent.Int64          `yaml:"proxy_port"`
+	PprofEnabled    serpent.Bool           `yaml:"pprof_enabled"`
+	PprofPort       serpent.Int64          `yaml:"pprof_port"`
 }
 
 // NewCommand creates and returns the root serpent command
@@ -47,6 +50,9 @@ func NewCommand() *serpent.Command {
   # Monitor all requests to specific domains (allow only those)
   boundary --allow "domain=github.com path=/api/issues/*" --allow "method=GET,HEAD domain=github.com" -- npm install
 
+  # Use allowlist from config file with additional CLI allow rules
+  boundary --allow "domain=example.com" -- curl https://example.com
+
   # Block everything by default (implicit)`
 
 	return cmd
@@ -58,49 +64,76 @@ func NewCommand() *serpent.Command {
 func BaseCommand() *serpent.Command {
 	config := Config{}
 
+	// Set default config path if file exists - serpent will load it automatically
+	if home, err := os.UserHomeDir(); err == nil {
+		defaultPath := filepath.Join(home, ".config", "coder_boundary", "config.yaml")
+		if _, err := os.Stat(defaultPath); err == nil {
+			config.Config = serpent.YAMLConfigPath(defaultPath)
+		}
+	}
+
 	return &serpent.Command{
 		Use:   "boundary",
 		Short: "Network isolation tool for monitoring and restricting HTTP/HTTPS requests",
 		Long:  `boundary creates an isolated network environment for target processes, intercepting HTTP/HTTPS traffic through a transparent proxy that enforces user-defined allow rules.`,
 		Options: []serpent.Option{
+			{
+				Flag:        "config",
+				Env:         "BOUNDARY_CONFIG",
+				Description: "Path to YAML config file.",
+				Value:       &config.Config,
+				YAML:        "",
+			},
 			{
 				Flag:        "allow",
 				Env:         "BOUNDARY_ALLOW",
-				Description: "Allow rule (repeatable). Format: \"pattern\" or \"METHOD[,METHOD] pattern\".",
-				Value:       serpent.StringArrayOf(&config.AllowStrings),
+				Description: "Allow rule (repeatable). These are merged with allowlist from config file. Format: \"pattern\" or \"METHOD[,METHOD] pattern\".",
+				Value:       &config.AllowStrings,
+				YAML:        "", // CLI only, not loaded from YAML
+			},
+			{
+				Flag:        "", // No CLI flag, YAML only
+				Description:  "Allowlist rules from config file (YAML only).",
+				Value:        &config.AllowListStrings,
+				YAML:         "allowlist",
 			},
 			{
 				Flag:        "log-level",
 				Env:         "BOUNDARY_LOG_LEVEL",
 				Description: "Set log level (error, warn, info, debug).",
 				Default:     "warn",
-				Value:       serpent.StringOf(&config.LogLevel),
+				Value:       &config.LogLevel,
+				YAML:        "log_level",
 			},
 			{
 				Flag:        "log-dir",
 				Env:         "BOUNDARY_LOG_DIR",
 				Description: "Set a directory to write logs to rather than stderr.",
-				Value:       serpent.StringOf(&config.LogDir),
+				Value:       &config.LogDir,
+				YAML:        "log_dir",
 			},
 			{
 				Flag:        "proxy-port",
 				Env:         "PROXY_PORT",
 				Description: "Set a port for HTTP proxy.",
 				Default:     "8080",
-				Value:       serpent.Int64Of(&config.ProxyPort),
+				Value:       &config.ProxyPort,
+				YAML:        "proxy_port",
 			},
 			{
 				Flag:        "pprof",
 				Env:         "BOUNDARY_PPROF",
 				Description: "Enable pprof profiling server.",
-				Value:       serpent.BoolOf(&config.PprofEnabled),
+				Value:       &config.PprofEnabled,
+				YAML:        "pprof_enabled",
 			},
 			{
 				Flag:        "pprof-port",
 				Env:         "BOUNDARY_PPROF_PORT",
 				Description: "Set port for pprof profiling server.",
 				Default:     "6060",
-				Value:       serpent.Int64Of(&config.PprofPort),
+				Value:       &config.PprofPort,
+				YAML:        "pprof_port",
 			},
 		},
 		Handler: func(inv *serpent.Invocation) error {
@@ -121,6 +154,12 @@ func Run(ctx context.Context, config Config, args []string) error {
 		return fmt.Errorf("could not set up logging: %v", err)
 	}
 
+	configInJSON, err := json.Marshal(config)
+	if err != nil {
+		return err
+	}
+	logger.Debug("config", "json_config", configInJSON)
+
 	if isChild() {
 		logger.Info("boundary CHILD process is started")
 
@@ -158,13 +197,19 @@ func Run(ctx context.Context, config Config, args []string) error {
 		return fmt.Errorf("no command specified")
 	}
 
-	// Parse allow list; default to deny-all if none provided
-	if len(config.AllowStrings) == 0 {
+	// Merge allowlist from config file with allow from CLI flags
+	allowListStrings := config.AllowListStrings.Value()
+	allowStrings := config.AllowStrings.Value()
+	
+	// Combine allowlist (config file) with allow (CLI flags)
+	allAllowStrings := append(allowListStrings, allowStrings...)
+	
+	if len(allAllowStrings) == 0 {
 		logger.Warn("No allow rules specified; all network traffic will be denied by default")
 	}
 
 	// Parse allow rules
-	allowRules, err := rulesengine.ParseAllowSpecs(config.AllowStrings)
+	allowRules, err := rulesengine.ParseAllowSpecs(allAllowStrings)
 	if err != nil {
 		logger.Error("Failed to parse allow rules", "error", err)
 		return fmt.Errorf("failed to parse allow rules: %v", err)
@@ -197,7 +242,7 @@ func Run(ctx context.Context, config Config, args []string) error {
 	// Create jailer with cert path from TLS setup
 	jailer, err := createJailer(jail.Config{
 		Logger:        logger,
-		HttpProxyPort: int(config.ProxyPort),
+		HttpProxyPort: int(config.ProxyPort.Value()),
 		Username:      username,
 		Uid:           uid,
 		Gid:           gid,
@@ -216,9 +261,9 @@ func Run(ctx context.Context, config Config, args []string) error {
 		TLSConfig:    tlsConfig,
 		Logger:       logger,
 		Jailer:       jailer,
-		ProxyPort:    int(config.ProxyPort),
-		PprofEnabled: config.PprofEnabled,
-		PprofPort:    int(config.PprofPort),
+		ProxyPort:    int(config.ProxyPort.Value()),
+		PprofEnabled: config.PprofEnabled.Value(),
+		PprofPort:    int(config.PprofPort.Value()),
 	})
 	if err != nil {
 		return fmt.Errorf("failed to create boundary instance: %v", err)
@@ -283,7 +328,7 @@ func Run(ctx context.Context, config Config, args []string) error {
 // setupLogging creates a slog logger with the specified level
 func setupLogging(config Config) (*slog.Logger, error) {
 	var level slog.Level
-	switch strings.ToLower(config.LogLevel) {
+	switch strings.ToLower(config.LogLevel.Value()) {
 	case "error":
 		level = slog.LevelError
 	case "warn":
@@ -298,18 +343,19 @@ func setupLogging(config Config) (*slog.Logger, error) {
 
 	logTarget := os.Stderr
 
-	if config.LogDir != "" {
+	logDir := config.LogDir.Value()
+	if logDir != "" {
 		// Set up the logging directory if it doesn't exist yet
-		if err := os.MkdirAll(config.LogDir, 0755); err != nil {
-			return nil, fmt.Errorf("could not set up log dir %s: %v", config.LogDir, err)
+		if err := os.MkdirAll(logDir, 0755); err != nil {
+			return nil, fmt.Errorf("could not set up log dir %s: %v", logDir, err)
 		}
 
 		// Create a logfile (timestamp and pid to avoid race conditions with multiple boundary calls running)
 		logFilePath := fmt.Sprintf("boundary-%s-%d.log",
 			time.Now().Format("2006-01-02_15-04-05"),
 			os.Getpid())
 
-		logFile, err := os.Create(filepath.Join(config.LogDir, logFilePath))
+		logFile, err := os.Create(filepath.Join(logDir, logFilePath))
 		if err != nil {
 			return nil, fmt.Errorf("could not create log file %s: %v", logFilePath, err)
 		}

rulesengine/rules.go

@@ -142,14 +142,14 @@ func parseMethodPattern(token string) (string, string, error) {
 	if token == "" {
 		return "", "", errors.New("expected http token, got empty string")
 	}
-	
+
 	// Find the first invalid HTTP token character
 	for i := 0; i < len(token); i++ {
 		if !isHTTPTokenChar(token[i]) {
 			return token[:i], token[i:], nil
 		}
 	}
-	
+
 	// Entire string is a valid HTTP token
 	return token, "", nil
 }