fix #920, #921

irc/email/dkim.go

@@ -0,0 +1,54 @@
+// Copyright (c) 2020 Shivaram Lingamneni
+// released under the MIT license
+
+package email
+
+import (
+	"errors"
+	dkim "github.com/toorop/go-dkim"
+	"io/ioutil"
+)
+
+var (
+	ErrMissingFields = errors.New("DKIM config is missing fields")
+)
+
+type DKIMConfig struct {
+	Domain   string
+	Selector string
+	KeyFile  string `yaml:"key-file"`
+	keyBytes []byte
+}
+
+func (dkim *DKIMConfig) Postprocess() (err error) {
+	if dkim.Domain != "" {
+		if dkim.Selector == "" || dkim.KeyFile == "" {
+			return ErrMissingFields
+		}
+		dkim.keyBytes, err = ioutil.ReadFile(dkim.KeyFile)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+var defaultOptions = dkim.SigOptions{
+	Version:               1,
+	Canonicalization:      "relaxed/relaxed",
+	Algo:                  "rsa-sha256",
+	Headers:               []string{"from", "to", "subject", "message-id"},
+	BodyLength:            0,
+	QueryMethods:          []string{"dns/txt"},
+	AddSignatureTimestamp: true,
+	SignatureExpireIn:     0,
+}
+
+func DKIMSign(message []byte, dkimConfig DKIMConfig) (result []byte, err error) {
+	options := defaultOptions
+	options.PrivateKey = dkimConfig.keyBytes
+	options.Domain = dkimConfig.Domain
+	options.Selector = dkimConfig.Selector
+	err = dkim.Sign(&message, options)
+	return message, err
+}