dkim.go

package main

import (
	"bytes"
	"encoding/json"
	"errors"
	"io/ioutil"
	"os"
	"smtprelay/dkim"
	"strings"
)

const KEY_CONFIG_SUFFIX string = ".config"

type DKIM struct {
	Selector string
	Domain   string
	Data     []byte
	dkimConf dkim.Conf
	dkim     dkim.DKIM
}

var DKIMRepo map[string]DKIM

func DKIMLoadKeyRepository() error {
	DKIMRepo = make(map[string]DKIM)
	dir, err := ioutil.ReadDir(conf.DKIMKeyDir)
	if err != nil {
		return err
	}
	var keyCount int
	var sep = os.PathSeparator
	for _, keyFile := range dir {
		if strings.Contains(keyFile.Name(), KEY_CONFIG_SUFFIX) {
			continue
		}

		key, err := DKIMLoadConfig(conf.DKIMKeyDir + string(sep) + keyFile.Name() + KEY_CONFIG_SUFFIX)
		if err != nil {
			log.Warn("can't read key config from %s:%s", conf.DKIMKeyDir+string(sep)+keyFile.Name(), err.Error()+KEY_CONFIG_SUFFIX)
			continue
		}

		key.Data, err = ioutil.ReadFile(conf.DKIMKeyDir + string(sep) + keyFile.Name())
		if err != nil {
			log.Warn("can't read key data from %s:%s", conf.DKIMKeyDir+string(sep)+keyFile.Name(), err.Error())
			continue
		}
		key.dkimConf, err = dkim.NewConf(key.Domain, key.Selector)
		if err != nil {
			log.Error("DKIM configuration error: %v", err)
			continue
		}

		d, err := dkim.New(key.dkimConf, key.Data)
		if err != nil {
			log.Error("DKIM error: %v", err)
			continue
		}
		key.dkim = *d
		DKIMRepo[key.Domain] = key

		keyCount++
	}
	log.Info("DKIM keys loaded - %d :", keyCount)
	for _, val := range DKIMRepo {
		log.Info("%s - %s", val.Domain, val.Selector)
	}

	return nil
}

func DKIMLoadConfig(filename string) (keyConfig DKIM, err error) {
	file, err := ioutil.ReadFile(filename)
	if err != nil {
		return keyConfig, err
	}

	err = json.Unmarshal(file, &keyConfig)
	if err != nil {
		return keyConfig, err
	}
	return keyConfig, nil
}

func DKIMSign(data []byte, domain string) ([]byte, error) {
	var err error
	privKey := DKIMRepo[domain]
	if len(privKey.Domain) == 0 {
		return data, errors.New("no key in keyrepo")
	}

	privKey.dkim.Conf, err = dkim.NewConf(privKey.Domain, privKey.Selector)
	if err != nil {
		return data, err
	}

	if bytes.Index(data, []byte("\r\n")) < 0 {
		data = bytes.Replace(data, []byte("\n"), []byte("\r\n"), -1)
	}
	signeddata, err := privKey.dkim.Sign(data)
	if err != nil {
		log.Error("DKIM signing error: %v", err)
		return data, err
	}
	return signeddata, nil
}