go-cert-gen/cmd/main.go

package cmd

import (
	"crypto/x509"
	"fmt"
	"log"
	"math/big"
	"os"

	"github.com/joho/godotenv"
	"github.com/kelseyhightower/envconfig"
	"github.com/spf13/cobra"
	"github.com/spf13/viper"
	"gitlab.com/urkob/go-cert-gen/internal/cert"
	"gitlab.com/urkob/go-cert-gen/internal/io"
	"gitlab.com/urkob/go-cert-gen/pkg/ca"
	"gitlab.com/urkob/go-cert-gen/pkg/client"
	pkgio "gitlab.com/urkob/go-cert-gen/pkg/io"
	"gitlab.com/urkob/go-cert-gen/pkg/util"
)

var envConfig struct {
	ViperConfig     string `required:"true" split_words:"true"`
	ViperConfigType string `required:"true" split_words:"true"`
	Env             string `required:"true" split_words:"true"`
}

var writer pkgio.WriterIface

func intEnvConfig(envFilePath string) {
	if envFilePath != "" {
		err := godotenv.Load(envFilePath)
		if err != nil {
			log.Fatalf("environment variable ENV is empty and an error occurred while loading the .env file: %s\n", err)
		}
	}

	err := envconfig.Process("", &envConfig)
	if err != nil {
		log.Fatalf("envconfig.Process: %s\n", err)
	}
}

var rootCmd = &cobra.Command{
	Use:   "go-gen-cert",
	Short: "go-gen-cert is a CLI tool to generate TLS certificates for your gRPC client/server communication",
	Run: func(cmd *cobra.Command, args []string) {
		caCfg := &ca.CaConfig{
			SerialNumber: big.NewInt(viper.GetInt64("ca.serial_number")),
			Subject: ca.CaSubject{
				Organization: viper.GetString("ca.subject.organization"),
				CommonName:   viper.GetString("ca.subject.common_name"),
			},
			KeyUsage:    x509.KeyUsage(viper.GetInt("ca.key_usage")),
			ExtKeyUsage: getExtKeyUsage(viper.GetIntSlice("ca.ext_key_usage")),
			Duration:    viper.GetDuration("ca.duration"),
		}

		rootCA, err := cert.NewRootCA(caCfg)
		if err != nil {
			log.Fatalf("cert.NewRootCA: %s", err)
		}

		subjectKeyId, err := util.GetBytes(viper.Get("client.subject_key_id"))
		if err != nil {
			log.Fatalf("cert.NewRootCA: %s", err)
		}

		clientCfg := &client.ClientCertConfig{
			Serial: &big.Int{},
			Subject: client.Subject{
				Organization:  viper.GetString("client.subject.organization"),
				Country:       viper.GetString("client.subject.country"),
				Province:      viper.GetString("client.subject.province"),
				Locality:      viper.GetString("client.subject.locality"),
				StreetAddress: viper.GetString("client.subject.street_address"),
				PostalCode:    viper.GetString("client.subject.postal_code"),
			},
			Duration:     viper.GetDuration("client.duration"),
			SubjectKeyId: subjectKeyId,
			ExtKeyUsage:  getExtKeyUsage(viper.GetIntSlice("client.ext_key_usage")),
			KeyUsage:     x509.KeyUsage(viper.GetInt("client.key_usage")),
		}

		clientCert, err := rootCA.WithClientCert(clientCfg)
		if err != nil {
			log.Fatalf("rootCA.WithClientCert: %s", err)
		}

		outputPath, err := exportPem("root-ca.pem", rootCA.PEM())
		if err != nil {
			log.Fatalf("exportPem: %s\n", err)
		}
		log.Printf("file created successfully: %s\n", outputPath)

		outputPath, err = exportPem("root-key.pem", rootCA.Key())
		if err != nil {
			log.Fatalf("exportPem: %s\n", err)
		}
		log.Printf("file created successfully: %s\n", outputPath)

		outputPath, err = exportPem("client-cert.pem", clientCert.PEM())
		if err != nil {
			log.Fatalf("exportPem: %s\n", err)
		}
		log.Printf("file created successfully: %s\n", outputPath)

		outputPath, err = exportPem("client-key.pem", clientCert.Key())
		if err != nil {
			log.Fatalf("exportPem: %s\n", err)
		}
		log.Printf("file created successfully: %s\n", outputPath)
	},
}

func getExtKeyUsage(intKeyUsageSlice []int) []x509.ExtKeyUsage {
	if intKeyUsageSlice == nil || len(intKeyUsageSlice) <= 0 {
		return []x509.ExtKeyUsage{}
	}

	extKeyUsage := make([]x509.ExtKeyUsage, 0, len(intKeyUsageSlice))
	for _, v := range intKeyUsageSlice {
		extKeyUsage = append(extKeyUsage, x509.ExtKeyUsage(v))
	}
	return extKeyUsage
}

func exportPem(filename string, data []byte) (string, error) {
	outputPath, err := writer.WriteFile(filename, data)
	if err != nil {
		return "", fmt.Errorf("rootCA.WithClientCert: %s", err)
	}
	return outputPath, nil
}

func init() {
	envFile := ""
	if os.Getenv("ENV") != "prod" {
		envFile = "./.env"
	}

	intEnvConfig(envFile)
	cobra.OnInitialize(initConfig)
}

func initConfig() {
	if envConfig.ViperConfig != "" {
		viper.AddConfigPath(util.RootDir())
		viper.SetConfigName(envConfig.ViperConfig)
		viper.SetConfigType(envConfig.ViperConfigType)
	} else {
		home, err := os.UserHomeDir()
		cobra.CheckErr(err)
		viper.AddConfigPath(home)
		viper.SetConfigType("yaml")
		viper.SetConfigName(".cobra")
	}

	if err := viper.ReadInConfig(); err != nil {
		log.Fatalf("viper.ReadInConfig: %s", err)
	}
	log.Println("viper.GetString('export_dir)", viper.GetString("export_dir"))
	writer = io.NewWriter(viper.GetString("export_dir"))
}

func Execute() {
	if err := rootCmd.Execute(); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
}