Make a string for SMTP "AUTH PLAIN" from an username and a password

smtpauth-password.go

//                _                     _   _                                                     _
//  ___ _ __ ___ | |_ _ __   __ _ _   _| |_| |__        _ __   __ _ ___ _____      _____  _ __ __| |
// / __| '_ ` _ \| __| '_ \ / _` | | | | __| '_ \ _____| '_ \ / _` / __/ __\ \ /\ / / _ \| '__/ _` |
// \__ \ | | | | | |_| |_) | (_| | |_| | |_| | | |_____| |_) | (_| \__ \__ \\ V  V / (_) | | | (_| |
// |___/_| |_| |_|\__| .__/ \__,_|\__,_|\__|_| |_|     | .__/ \__,_|___/___/ \_/\_/ \___/|_|  \__,_|
//                   |_|                               |_|
package main

// Usage:
//		$ go run ./smtpauth-password username@example.jp password-string-for-smtp-authentication
//		$ go run ./smtpauth-password --aws ap-northeast-1 --smtp-password AccessKeyID AccessSecret

import "os"
import "flag"
import "fmt"
import "crypto/hmac"
import "crypto/sha256"
import b64 "encoding/base64"

var Version = "0.0.1"
var Default = map[string]string{
	"region": "us-east-1",
}
var Setting = map[string]string{
	"region": "",
}
var Options = map[string]uint8{
	"exec":          (1 << 0),
	"test":          (1 << 1),
	"neko":          (1 << 2),
	"aws":           (1 << 3),
	"smtp-password": (1 << 4),
}

func e(mesg string, cont bool) {
	if len(mesg) > 0 {
		fmt.Fprintf(os.Stderr, " * error0: %s\n", mesg)
		if !cont {
			os.Exit(1)
		}
	}
}

func main() {
	o := parseoptions()
	a := flag.Args()

	if o&Options["exec"] > 0 {
		username := a[0]
		password := a[1]
		authtext := ""

		if o&Options["aws"] > 0 {
			// --aws option specified
			if len(username) == 0 {
				e("Access Key ID is empty", false)
			}
			if len(password) == 0 {
				e("Secret Access Key is empty", false)
			}

			parameters := map[string]string{
				"date":     "11111111",
				"service":  "ses",
				"message":  "SendRawEmail",
				"terminal": "aws4_request",
				"version":  "\x04",
			}
			regionlist := []string{
				"us-east-2",      // US East (Ohio)
				"us-east-1",      // US East (N. Virginia)
				"us-west-2",      // US West (Oregon)
				"ap-south-1",     // # Asia Pacific (Mumbai)
				"ap-northeast-2", // Asia Pacific (Seoul)
				"ap-southeast-1", // Asia Pacific (Singapore)
				"ap-southeast-2", // Asia Pacific (Sydney)
				"ap-northeast-1", // Asia Pacific (Tokyo)
				"ca-central-1",   // Canada (Central)
				"eu-central-1",   // Europe (Frankfurt)
				"eu-west-1",      // Europe (Ireland)
				"eu-west-2",      // Europe (London)
				"sa-east-1",      // South America (Sao Paulo)
				"us-gov-west-1",  // AWS GovCloud (US)
			}

			regionok := false
			for _, e := range regionlist {
				// The regsion specified with --region option does not have an SMTP endpoint
				if Setting["region"] == e {
					regionok = true
					break
				}
			}
			if !regionok {
				e(fmt.Sprintf("The %s region does not have an SMTP endpoint", Setting["region"]), false)
			}

			digesthash := ""
			smtppasswd := ""
			makedigest := func(key, msg string) string {
				if len(key) == 0 {
					return ""
				}
				if len(msg) == 0 {
					return ""
				}

				mac := hmac.New(sha256.New, []byte(key))
				mac.Write([]byte(msg))
				return string(mac.Sum(nil))
			}

			digesthash = makedigest("AWS4"+password, parameters["date"])
			digesthash = makedigest(digesthash, Setting["region"])
			digesthash = makedigest(digesthash, parameters["service"])
			digesthash = makedigest(digesthash, parameters["terminal"])
			digesthash = makedigest(digesthash, parameters["message"])
			smtppasswd = b64.StdEncoding.EncodeToString([]byte(fmt.Sprintf("%s%s", parameters["version"], digesthash)))

			if o&Options["smtp-password"] > 0 {
				// Print an SMTP password and exit when --smtp-password option was specified
				fmt.Printf("%s\n", smtppasswd)

			} else {
				// Print an authentication text for "AUTH PLAIN" SMTP command
				authtext = fmt.Sprintf("%s\x00%s\x00%s", username, username, smtppasswd)
				fmt.Printf("%s\n", b64.StdEncoding.EncodeToString([]byte(authtext)))
			}
		} else {
			// Make an credentials for general SMTP Authentication
			if len(username) == 0 {
				e("Username is empty", false)
			}
			if len(password) == 0 {
				e("Passowrd is empty", false)
			}

			authtext = fmt.Sprintf("%s\x00%s\x00%s", username, username, password)
			fmt.Printf("%s\n", b64.StdEncoding.EncodeToString([]byte(authtext)))
		}
	}
}

func parseoptions() uint8 {
	// Parse arguments given from a command line
	var o uint8 = 0
	var f_is_amazonses = flag.String("aws", "", "Make SMTP Credentials for Amazon SES")
	var f_smtppassword = flag.Bool("smtp-password", false, "Output SMTP Password for Amazon SES")

	flag.Parse()
	o |= Options["exec"]

	if len(*f_is_amazonses) > 0 {
		// --aws option specified
		o |= Options["aws"]
		Setting["region"] = *f_is_amazonses
	}

	if *f_smtppassword {
		// --smtp-password option specified
		o |= Options["smtp-password"]
	}

	return o
}