Implement config generator

This commit adds code to allow the generation of a default client
configuration. The generator is run instead of the regular client
code, when the option -generate-config is passed on the command
line.

cmd/signerclient/main.go

@@ -20,9 +20,12 @@ package main
 import (
 	"context"
 	"flag"
+	"fmt"
 	"os"
+	"strings"
 
 	"github.com/sirupsen/logrus"
+	"gopkg.in/yaml.v3"
 
 	"git.cacert.org/cacert-gosigner/pkg/protocol"
 	"git.cacert.org/cacert-gosignerclient/internal/client"
@@ -42,7 +45,7 @@ const (
 
 func main() {
 	var (
-		showVersion, verbose bool
+		showVersion, verbose, generateConfig bool
 		configFile, logLevel                 string
 		logger                               *logrus.Logger
 	)
@@ -56,6 +59,12 @@ func main() {
 	flag.StringVar(&configFile, "config", defaultConfigFile, "signer client configuration file")
 	flag.BoolVar(&showVersion, "version", false, "show version")
 	flag.BoolVar(&verbose, "verbose", false, "verbose output")
+	flag.BoolVar(
+		&generateConfig,
+		"generate-config",
+		false,
+		"generate a configuration file with default values instead of running the client",
+	)
 	flag.StringVar(&logLevel, "loglevel", "INFO", "log level")
 
 	flag.Parse()
@@ -71,9 +80,45 @@ func main() {
 
 	logger.SetLevel(parsedLevel)
 
+	if generateConfig {
+		if err = generateDefaultConfig(); err != nil {
+			logger.WithError(err).Fatal("could not generate default configuration")
+		}
+
+		return
+	}
+
+	if err := startClient(configFile, logger); err != nil {
+		logger.WithError(err).Fatal("client failure")
+	}
+}
+
+func generateDefaultConfig() error {
+	const defaultBaseConfiguration = `---
+serial:
+  device: /dev/ttyUSB0
+  baud: 112500
+`
+
+	cfg, err := config.LoadConfiguration(strings.NewReader(
+		defaultBaseConfiguration))
+	if err != nil {
+		return fmt.Errorf("could not load empty configuration: %w", err)
+	}
+
+	enc := yaml.NewEncoder(os.Stdout)
+
+	if err = enc.Encode(cfg); err != nil {
+		return fmt.Errorf("could not encode: %w", err)
+	}
+
+	return nil
+}
+
+func startClient(configFile string, logger *logrus.Logger) error {
 	clientConfig, err := config.New(configFile)
 	if err != nil {
-		logger.WithError(err).Fatal("could not configure client")
+		return fmt.Errorf("could not configure client: %w", err)
 	}
 
 	commands := make(chan *protocol.Command)
@@ -81,12 +126,12 @@ func main() {
 
 	clientHandler, err := handler.New(clientConfig, logger, commands, callbacks)
 	if err != nil {
-		logger.WithError(err).Fatal("could not setup client handler")
+		return fmt.Errorf("could not setup client handler: %w", err)
 	}
 
 	signerClient, err := client.New(clientConfig, logger, clientHandler, commands, callbacks)
 	if err != nil {
-		logger.WithError(err).Fatal("could not setup client")
+		return fmt.Errorf("could not setup client: %w", err)
 	}
 
 	defer func() { _ = signerClient.Close() }()
@@ -94,6 +139,8 @@ func main() {
 	logger.Info("setup complete, starting client operation")
 
 	if err = signerClient.Run(context.Background()); err != nil {
-		logger.WithError(err).Fatal("error in client")
+		return fmt.Errorf("error in client: %w", err)
 	}
+
+	return nil
 }

internal/client/client.go

@@ -432,24 +432,16 @@ func (c *Client) updateCRL(d *messages.FetchCRLResponse) ([]*protocol.Command, e
 }
 
 func (c *Client) buildCRLFileName(caName string) string {
-	return path.Join(c.config.PublicDataDirectory, fmt.Sprintf("%s.crl", caName))
+	return path.Join(c.config.PublicCRLDirectory, fmt.Sprintf("%s.crl", caName))
 }
 
 func (c *Client) buildCertificateFileName(caName string, certFormat string) string {
-	return path.Join(c.config.PublicDataDirectory, fmt.Sprintf("%s.%s", caName, certFormat))
+	return path.Join(c.config.PublicCRLDirectory, fmt.Sprintf("%s.%s", caName, certFormat))
-}
-
-func (c *Client) ensurePublicDataDirectory() error {
-	if err := os.MkdirAll(c.config.PublicDataDirectory, worldReadableDirPerm); err != nil {
-		return fmt.Errorf("could not create public CA data directory %s: %w", c.config.PublicDataDirectory, err)
-	}
-
-	return nil
 }
 
 func (c *Client) writeCertificate(caName string, derBytes []byte) error {
-	if err := c.ensurePublicDataDirectory(); err != nil {
+	if err := os.MkdirAll(c.config.PublicCRLDirectory, worldReadableDirPerm); err != nil {
-		return err
+		return fmt.Errorf("could not create public CA data directory %s: %w", c.config.PublicCRLDirectory, err)
 	}
 
 	if err := os.WriteFile(
@@ -470,8 +462,8 @@ func (c *Client) writeCertificate(caName string, derBytes []byte) error {
 }
 
 func (c *Client) writeCRL(caName string, crlBytes []byte) error {
-	if err := c.ensurePublicDataDirectory(); err != nil {
+	if err := os.MkdirAll(c.config.PublicCRLDirectory, worldReadableDirPerm); err != nil {
-		return err
+		return fmt.Errorf("could not create public CA data directory %s: %w", c.config.PublicCRLDirectory, err)
 	}
 
 	if err := os.WriteFile(c.buildCRLFileName(caName), crlBytes, worldReadableFilePerm); err != nil {

internal/config/config.go

@@ -59,7 +59,8 @@ type ClientConfig struct {
 	FetchCRLInterval           time.Duration `yaml:"fetch-crl-interval"`
 	ResponseAnnounceTimeout    time.Duration `yaml:"response-announce-timeout"`
 	ResponseDataTimeout        time.Duration `yaml:"response-data-timeout"`
-	PublicDataDirectory     string        `yaml:"public-data-directory"`
+	PublicCRLDirectory         string        `yaml:"public-crl-directory"`
+	PublicCertificateDirectory string        `yaml:"public-certificate-directory"`
 }
 
 func (c *ClientConfig) UnmarshalYAML(n *yaml.Node) error {
@@ -71,7 +72,8 @@ func (c *ClientConfig) UnmarshalYAML(n *yaml.Node) error {
 		FetchCRLInterval           time.Duration `yaml:"fetch-crl-interval"`
 		ResponseAnnounceTimeout    time.Duration `yaml:"response-announce-timeout"`
 		ResponseDataTimeout        time.Duration `yaml:"response-data-timeout"`
-		PublicDataDirectory     string        `yaml:"public-data-directory"`
+		PublicCRLDirectory         string        `yaml:"public-crl-directory"`
+		PublicCertificateDirectory string        `yaml:"public-certificate-directory"`
 	}{}
 
 	err := n.Decode(&data)
@@ -129,11 +131,17 @@ func (c *ClientConfig) UnmarshalYAML(n *yaml.Node) error {
 
 	c.ResponseDataTimeout = data.ResponseDataTimeout
 
-	if data.PublicDataDirectory == "" {
+	if data.PublicCRLDirectory == "" {
-		data.PublicDataDirectory = defaultFilesDirectory
+		data.PublicCRLDirectory = defaultFilesDirectory
 	}
 
-	c.PublicDataDirectory = data.PublicDataDirectory
+	c.PublicCRLDirectory = data.PublicCRLDirectory
+
+	if data.PublicCertificateDirectory == "" {
+		data.PublicCertificateDirectory = defaultFilesDirectory
+	}
+
+	c.PublicCertificateDirectory = data.PublicCRLDirectory
 
 	return nil
 }