fix #920, #921

Makefile

@@ -22,6 +22,7 @@ test:
 	cd irc/caps && go test . && go vet .
 	cd irc/cloaks && go test . && go vet .
 	cd irc/connection_limits && go test . && go vet .
+	cd irc/email && go test . && go vet .
 	cd irc/history && go test . && go vet .
 	cd irc/isupport && go test . && go vet .
 	cd irc/modes && go test . && go vet .

conventional.yaml

@@ -280,16 +280,24 @@ accounts:
         enabled-callbacks:
             - none # no verification needed, will instantly register successfully
 
-        # example configuration for sending verification emails via a local mail relay
+        # example configuration for sending verification emails
         # callbacks:
         #     mailto:
-        #         server: localhost
-        #         port: 25
-        #         tls:
-        #             enabled: false
-        #         username: ""
-        #         password: ""
         #         sender: "admin@my.network"
+        #         require-tls: true
+        #         helo-domain: "my.network" # defaults to server name if unset
+        #         dkim:
+        #             domain: "my.network"
+        #             selector: "20200229"
+        #             key-file: "dkim.pem"
+        #         # to use an MTA/smarthost instead of sending email directly:
+        #         # mta:
+        #         #     server: localhost
+        #         #     port: 25
+        #         #     username: "admin"
+        #         #     password: "hunter2"
+        #         blacklist-regexes:
+        #         #    - ".*@mailinator.com"
 
     # throttle account login attempts (to prevent either password guessing, or DoS
     # attacks on the server aimed at forcing repeated expensive bcrypt computations)

go.mod

@@ -18,6 +18,7 @@ require (
 	github.com/oragono/go-ident v0.0.0-20170110123031-337fed0fd21a
 	github.com/stretchr/testify v1.4.0 // indirect
 	github.com/tidwall/buntdb v1.1.2
+	github.com/toorop/go-dkim v0.0.0-20191019073156-897ad64a2eeb
 	golang.org/x/crypto v0.0.0-20200302210943-78000ba7a073
 	golang.org/x/text v0.3.2
 	gopkg.in/yaml.v2 v2.2.8

go.sum

@@ -65,6 +65,8 @@ github.com/tidwall/rtree v0.0.0-20180113144539-6cd427091e0e h1:+NL1GDIUOKxVfbp2K
 github.com/tidwall/rtree v0.0.0-20180113144539-6cd427091e0e/go.mod h1:/h+UnNGt0IhNNJLkGikcdcJqm66zGD/uJGMRxK/9+Ao=
 github.com/tidwall/tinyqueue v0.0.0-20180302190814-1e39f5511563 h1:Otn9S136ELckZ3KKDyCkxapfufrqDqwmGjcHfAyXRrE=
 github.com/tidwall/tinyqueue v0.0.0-20180302190814-1e39f5511563/go.mod h1:mLqSmt7Dv/CNneF2wfcChfN1rvapyQr01LGKnKex0DQ=
+github.com/toorop/go-dkim v0.0.0-20191019073156-897ad64a2eeb h1:ilDZC+k9r67aJqSOalZLtEVLO7Cmmsq5ftfcvLirc24=
+github.com/toorop/go-dkim v0.0.0-20191019073156-897ad64a2eeb/go.mod h1:BzWtXXrXzZUvMacR0oF/fbDDgUPO8L36tDMmRAf14ns=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20191112222119-e1110fd1c708 h1:pXVtWnwHkrWD9ru3sDxY/qFK/bfc0egRovX91EjWjf4=
 golang.org/x/crypto v0.0.0-20191112222119-e1110fd1c708/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=

irc/accounts.go

@@ -4,9 +4,9 @@
 package irc
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
-	"net/smtp"
 	"strconv"
 	"strings"
 	"sync"
@@ -16,6 +16,7 @@ import (
 
 	"github.com/oragono/oragono/irc/caps"
 	"github.com/oragono/oragono/irc/connection_limits"
+	"github.com/oragono/oragono/irc/email"
 	"github.com/oragono/oragono/irc/ldap"
 	"github.com/oragono/oragono/irc/passwd"
 	"github.com/oragono/oragono/irc/utils"
@@ -483,7 +484,7 @@ func (am *AccountManager) Register(client *Client, account string, callbackNames
 		return err
 	}
 
-	code, err := am.dispatchCallback(client, casefoldedAccount, callbackNamespace, callbackValue)
+	code, err := am.dispatchCallback(client, account, callbackNamespace, callbackValue)
 	if err != nil {
 		am.Unregister(casefoldedAccount, true)
 		return errCallbackFailed
@@ -698,17 +699,17 @@ func (am *AccountManager) addRemoveCertfp(account, certfp string, add bool, hasP
 	return err
 }
 
-func (am *AccountManager) dispatchCallback(client *Client, casefoldedAccount string, callbackNamespace string, callbackValue string) (string, error) {
+func (am *AccountManager) dispatchCallback(client *Client, account string, callbackNamespace string, callbackValue string) (string, error) {
 	if callbackNamespace == "*" || callbackNamespace == "none" || callbackNamespace == "admin" {
 		return "", nil
 	} else if callbackNamespace == "mailto" {
-		return am.dispatchMailtoCallback(client, casefoldedAccount, callbackValue)
+		return am.dispatchMailtoCallback(client, account, callbackValue)
 	} else {
 		return "", fmt.Errorf("Callback not implemented: %s", callbackNamespace)
 	}
 }
 
-func (am *AccountManager) dispatchMailtoCallback(client *Client, casefoldedAccount string, callbackValue string) (code string, err error) {
+func (am *AccountManager) dispatchMailtoCallback(client *Client, account string, callbackValue string) (code string, err error) {
 	config := am.server.Config().Accounts.Registration.Callbacks.Mailto
 	code = utils.GenerateSecretToken()
 
@@ -716,34 +717,27 @@ func (am *AccountManager) dispatchMailtoCallback(client *Client, casefoldedAccou
 	if subject == "" {
 		subject = fmt.Sprintf(client.t("Verify your account on %s"), am.server.name)
 	}
-	messageStrings := []string{
-		fmt.Sprintf("From: %s\r\n", config.Sender),
-		fmt.Sprintf("To: %s\r\n", callbackValue),
-		fmt.Sprintf("Subject: %s\r\n", subject),
-		"\r\n", // end headers, begin message body
-		fmt.Sprintf(client.t("Account: %s"), casefoldedAccount) + "\r\n",
-		fmt.Sprintf(client.t("Verification code: %s"), code) + "\r\n",
-		"\r\n",
-		client.t("To verify your account, issue the following command:") + "\r\n",
-		fmt.Sprintf("/MSG NickServ VERIFY %s %s", casefoldedAccount, code) + "\r\n",
-	}
 
-	var message []byte
+	var message bytes.Buffer
-	for i := 0; i < len(messageStrings); i++ {
+	fmt.Fprintf(&message, "From: %s\r\n", config.Sender)
-		message = append(message, []byte(messageStrings[i])...)
+	fmt.Fprintf(&message, "To: %s\r\n", callbackValue)
-	}
+	if config.DKIM.Domain != "" {
-	addr := fmt.Sprintf("%s:%d", config.Server, config.Port)
+		fmt.Fprintf(&message, "Message-ID: <%s@%s>\r\n", utils.GenerateSecretKey(), config.DKIM.Domain)
-	var auth smtp.Auth
-	if config.Username != "" && config.Password != "" {
-		auth = smtp.PlainAuth("", config.Username, config.Password, config.Server)
 	}
+	fmt.Fprintf(&message, "Subject: %s\r\n", subject)
+	message.WriteString("\r\n") // blank line: end headers, begin message body
+	fmt.Fprintf(&message, client.t("Account: %s"), account)
+	message.WriteString("\r\n")
+	fmt.Fprintf(&message, client.t("Verification code: %s"), code)
+	message.WriteString("\r\n")
+	message.WriteString("\r\n")
+	message.WriteString(client.t("To verify your account, issue the following command:"))
+	message.WriteString("\r\n")
+	fmt.Fprintf(&message, "/MSG NickServ VERIFY %s %s\r\n", account, code)
 
-	// TODO: this will never send the password in plaintext over a nonlocal link,
+	err = email.SendMail(config, callbackValue, message.Bytes())
-	// but it might send the email in plaintext, regardless of the value of
-	// config.TLS.InsecureSkipVerify
-	err = smtp.SendMail(addr, auth, config.Sender, []string{callbackValue}, message)
 	if err != nil {
-		am.server.logger.Error("internal", "Failed to dispatch e-mail", err.Error())
+		am.server.logger.Error("internal", "Failed to dispatch e-mail to", callbackValue, err.Error())
 	}
 	return
 }

irc/config.go

@@ -24,6 +24,7 @@ import (
 	"github.com/oragono/oragono/irc/cloaks"
 	"github.com/oragono/oragono/irc/connection_limits"
 	"github.com/oragono/oragono/irc/custime"
+	"github.com/oragono/oragono/irc/email"
 	"github.com/oragono/oragono/irc/isupport"
 	"github.com/oragono/oragono/irc/languages"
 	"github.com/oragono/oragono/irc/ldap"
@@ -290,20 +291,7 @@ type AccountRegistrationConfig struct {
 	EnabledCredentialTypes []string         `yaml:"-"`
 	VerifyTimeout          custime.Duration `yaml:"verify-timeout"`
 	Callbacks              struct {
-		Mailto struct {
+		Mailto email.MailtoConfig
-			Server string
-			Port   int
-			TLS    struct {
-				Enabled            bool
-				InsecureSkipVerify bool   `yaml:"insecure_skip_verify"`
-				ServerName         string `yaml:"servername"`
-			}
-			Username             string
-			Password             string
-			Sender               string
-			VerifyMessageSubject string `yaml:"verify-message-subject"`
-			VerifyMessage        string `yaml:"verify-message"`
-		}
 	}
 	BcryptCost uint `yaml:"bcrypt-cost"`
 }
@@ -975,14 +963,24 @@ func LoadConfig(filename string) (config *Config, err error) {
 
 	// hardcode this for now
 	config.Accounts.Registration.EnabledCredentialTypes = []string{"passphrase", "certfp"}
+	mailtoEnabled := false
 	for i, name := range config.Accounts.Registration.EnabledCallbacks {
 		if name == "none" {
 			// we store "none" as "*" internally
 			config.Accounts.Registration.EnabledCallbacks[i] = "*"
+		} else if name == "mailto" {
+			mailtoEnabled = true
 		}
 	}
 	sort.Strings(config.Accounts.Registration.EnabledCallbacks)
 
+	if mailtoEnabled {
+		err := config.Accounts.Registration.Callbacks.Mailto.Postprocess(config.Server.Name)
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	config.Accounts.RequireSasl.exemptedNets, err = utils.ParseNetList(config.Accounts.RequireSasl.Exempted)
 	if err != nil {
 		return nil, fmt.Errorf("Could not parse require-sasl exempted nets: %v", err.Error())

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
+}

irc/email/email.go

@@ -0,0 +1,124 @@
+// Copyright (c) 2020 Shivaram Lingamneni
+// released under the MIT license
+
+package email
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"regexp"
+	"strings"
+
+	"github.com/oragono/oragono/irc/smtp"
+)
+
+var (
+	ErrBlacklistedAddress = errors.New("Email address is blacklisted")
+	ErrInvalidAddress     = errors.New("Email address is blacklisted")
+	ErrNoMXRecord         = errors.New("Couldn't resolve MX record")
+)
+
+type MTAConfig struct {
+	Server   string
+	Port     int
+	Username string
+	Password string
+}
+
+type MailtoConfig struct {
+	// legacy config format assumed the use of an MTA/smarthost,
+	// so server, port, etc. appear directly at top level
+	// XXX: see https://github.com/go-yaml/yaml/issues/63
+	MTAConfig            `yaml:",inline"`
+	Sender               string
+	HeloDomain           string `yaml:"helo-domain"`
+	RequireTLS           bool   `yaml:"require-tls"`
+	VerifyMessageSubject string `yaml:"verify-message-subject"`
+	DKIM                 DKIMConfig
+	MTAReal              MTAConfig `yaml:"mta"`
+	BlacklistRegexes     []string  `yaml:"blacklist-regexes"`
+	blacklistRegexes     []*regexp.Regexp
+}
+
+func (config *MailtoConfig) Postprocess(heloDomain string) (err error) {
+	if config.Sender == "" {
+		return errors.New("Invalid mailto sender address")
+	}
+
+	// check for MTA config fields at top level,
+	// copy to MTAReal if present
+	if config.Server != "" && config.MTAReal.Server == "" {
+		config.MTAReal = config.MTAConfig
+	}
+
+	if config.HeloDomain == "" {
+		config.HeloDomain = heloDomain
+	}
+
+	for _, reg := range config.BlacklistRegexes {
+		compiled, err := regexp.Compile(fmt.Sprintf("^%s$", reg))
+		if err != nil {
+			return err
+		}
+		config.blacklistRegexes = append(config.blacklistRegexes, compiled)
+	}
+
+	if config.MTAConfig.Server != "" {
+		// smarthost, nothing more to validate
+		return nil
+	}
+
+	return config.DKIM.Postprocess()
+}
+
+// get the preferred MX record hostname, "" on error
+func lookupMX(domain string) (server string) {
+	var minPref uint16
+	results, err := net.LookupMX(domain)
+	if err != nil {
+		return
+	}
+	for _, result := range results {
+		if minPref == 0 || result.Pref < minPref {
+			server, minPref = result.Host, result.Pref
+		}
+	}
+	return
+}
+
+func SendMail(config MailtoConfig, recipient string, msg []byte) (err error) {
+	for _, reg := range config.blacklistRegexes {
+		if reg.MatchString(recipient) {
+			return ErrBlacklistedAddress
+		}
+	}
+
+	if config.DKIM.Domain != "" {
+		msg, err = DKIMSign(msg, config.DKIM)
+		if err != nil {
+			return
+		}
+	}
+
+	var addr string
+	var auth smtp.Auth
+	if config.MTAReal.Server != "" {
+		addr = fmt.Sprintf("%s:%d", config.MTAReal.Server, config.MTAReal.Port)
+		if config.MTAReal.Username != "" && config.MTAReal.Password != "" {
+			auth = smtp.PlainAuth("", config.MTAReal.Username, config.MTAReal.Password, config.MTAReal.Server)
+		}
+	} else {
+		idx := strings.IndexByte(recipient, '@')
+		if idx == -1 {
+			return ErrInvalidAddress
+		}
+		mx := lookupMX(recipient[idx+1:])
+		if mx == "" {
+			return ErrNoMXRecord
+		}
+		addr = fmt.Sprintf("%s:smtp", mx)
+	}
+
+	return smtp.SendMail(addr, auth, config.HeloDomain, config.Sender, []string{recipient}, msg, config.RequireTLS)
+}

irc/smtp/smtp.go

@@ -316,7 +316,8 @@ var testHookStartTLS func(*tls.Config) // nil, except for tests
 // attachments (see the mime/multipart package), or other mail
 // functionality. Higher-level packages exist outside of the standard
 // library.
-func SendMail(addr string, a Auth, from string, to []string, msg []byte) error {
+// XXX: modified in Oragono to add `requireTLS` and `heloDomain` arguments
+func SendMail(addr string, a Auth, heloDomain string, from string, to []string, msg []byte, requireTLS bool) error {
 	if err := validateLine(from); err != nil {
 		return err
 	}
@@ -330,7 +331,7 @@ func SendMail(addr string, a Auth, from string, to []string, msg []byte) error {
 		return err
 	}
 	defer c.Close()
-	if err = c.hello(); err != nil {
+	if err = c.Hello(heloDomain); err != nil {
 		return err
 	}
 	if ok, _ := c.Extension("STARTTLS"); ok {
@@ -341,6 +342,8 @@ func SendMail(addr string, a Auth, from string, to []string, msg []byte) error {
 		if err = c.StartTLS(config); err != nil {
 			return err
 		}
+	} else if requireTLS {
+		return errors.New("TLS required, but not negotiated")
 	}
 	if a != nil && c.ext != nil {
 		if _, ok := c.ext["AUTH"]; !ok {

oragono.yaml

@@ -301,16 +301,24 @@ accounts:
         enabled-callbacks:
             - none # no verification needed, will instantly register successfully
 
-        # example configuration for sending verification emails via a local mail relay
+        # example configuration for sending verification emails
         # callbacks:
         #     mailto:
-        #         server: localhost
-        #         port: 25
-        #         tls:
-        #             enabled: false
-        #         username: ""
-        #         password: ""
         #         sender: "admin@my.network"
+        #         require-tls: true
+        #         helo-domain: "my.network" # defaults to server name if unset
+        #         dkim:
+        #             domain: "my.network"
+        #             selector: "20200229"
+        #             key-file: "dkim.pem"
+        #         # to use an MTA/smarthost instead of sending email directly:
+        #         # mta:
+        #         #     server: localhost
+        #         #     port: 25
+        #         #     username: "admin"
+        #         #     password: "hunter2"
+        #         blacklist-regexes:
+        #         #    - ".*@mailinator.com"
 
     # throttle account login attempts (to prevent either password guessing, or DoS
     # attacks on the server aimed at forcing repeated expensive bcrypt computations)

vendor/github.com/toorop/go-dkim/.gitignore

@@ -0,0 +1,24 @@
+# Compiled Object files, Static and Dynamic libs (Shared Objects)
+*.o
+*.a
+*.so
+
+# Folders
+_obj
+_test
+
+# Architecture specific extensions/prefixes
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe
+*.test
+*.prof

vendor/github.com/toorop/go-dkim/LICENSE

@@ -0,0 +1,22 @@
+The MIT License (MIT)
+
+Copyright (c) 2015 Stéphane Depierrepont
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+

vendor/github.com/toorop/go-dkim/README.md

@@ -0,0 +1,56 @@
+# go-dkim
+DKIM package for Golang
+
+[![GoDoc](https://godoc.org/github.com/toorop/go-dkim?status.svg)](https://godoc.org/github.com/toorop/go-dkim)
+
+## Getting started
+
+### Install
+```
+ 	go get github.com/toorop/go-dkim
+```
+Warning: you need to use Go 1.4.2-master or 1.4.3 (when it will be available)
+see https://github.com/golang/go/issues/10482 fro more info.
+
+### Sign email
+
+```go
+import (
+	dkim "github.com/toorop/go-dkim"
+)
+
+func main(){
+	// email is the email to sign (byte slice)
+	// privateKey the private key (pem encoded, byte slice )	
+	options := dkim.NewSigOptions()
+	options.PrivateKey = privateKey
+	options.Domain = "mydomain.tld"
+	options.Selector = "myselector"
+	options.SignatureExpireIn = 3600
+	options.BodyLength = 50
+	options.Headers = []string{"from", "date", "mime-version", "received", "received"}
+	options.AddSignatureTimestamp = true
+	options.Canonicalization = "relaxed/relaxed"
+	err := dkim.Sign(&email, options)
+	// handle err..
+
+	// And... that's it, 'email' is signed ! Amazing© !!!
+}
+```
+
+### Verify
+```go
+import (
+	dkim "github.com/toorop/go-dkim"
+)
+
+func main(){
+	// email is the email to verify (byte slice)
+	status, err := Verify(&email)
+	// handle status, err (see godoc for status)
+}
+```
+
+## Todo
+
+- [ ] handle z tag (copied header fields used for diagnostic use)

vendor/github.com/toorop/go-dkim/dkim.go

@@ -0,0 +1,557 @@
+// Package dkim provides tools for signing and verify a email according to RFC 6376
+package dkim
+
+import (
+	"bytes"
+	"container/list"
+	"crypto"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha1"
+	"crypto/sha256"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/pem"
+	"hash"
+	"regexp"
+	"strings"
+	"time"
+)
+
+const (
+	CRLF                = "\r\n"
+	TAB                 = " "
+	FWS                 = CRLF + TAB
+	MaxHeaderLineLength = 70
+)
+
+type verifyOutput int
+
+const (
+	SUCCESS verifyOutput = 1 + iota
+	PERMFAIL
+	TEMPFAIL
+	NOTSIGNED
+	TESTINGSUCCESS
+	TESTINGPERMFAIL
+	TESTINGTEMPFAIL
+)
+
+// sigOptions represents signing options
+type SigOptions struct {
+
+	// DKIM version (default 1)
+	Version uint
+
+	// Private key used for signing (required)
+	PrivateKey []byte
+
+	// Domain (required)
+	Domain string
+
+	// Selector (required)
+	Selector string
+
+	// The Agent of User IDentifier
+	Auid string
+
+	// Message canonicalization (plain-text; OPTIONAL, default is
+	// "simple/simple").  This tag informs the Verifier of the type of
+	// canonicalization used to prepare the message for signing.
+	Canonicalization string
+
+	// The algorithm used to generate the signature
+	//"rsa-sha1" or "rsa-sha256"
+	Algo string
+
+	// Signed header fields
+	Headers []string
+
+	// Body length count( if set to 0 this tag is ommited in Dkim header)
+	BodyLength uint
+
+	// Query Methods used to retrieve the public key
+	QueryMethods []string
+
+	// Add a signature timestamp
+	AddSignatureTimestamp bool
+
+	// Time validity of the signature (0=never)
+	SignatureExpireIn uint64
+
+	// CopiedHeaderFileds
+	CopiedHeaderFields []string
+}
+
+// NewSigOptions returns new sigoption with some defaults value
+func NewSigOptions() SigOptions {
+	return SigOptions{
+		Version:               1,
+		Canonicalization:      "simple/simple",
+		Algo:                  "rsa-sha256",
+		Headers:               []string{"from"},
+		BodyLength:            0,
+		QueryMethods:          []string{"dns/txt"},
+		AddSignatureTimestamp: true,
+		SignatureExpireIn:     0,
+	}
+}
+
+// Sign signs an email
+func Sign(email *[]byte, options SigOptions) error {
+	var privateKey *rsa.PrivateKey
+
+	// PrivateKey
+	if len(options.PrivateKey) == 0 {
+		return ErrSignPrivateKeyRequired
+	}
+	d, _ := pem.Decode(options.PrivateKey)
+	if d == nil {
+		return ErrCandNotParsePrivateKey
+	}
+	key, err := x509.ParsePKCS1PrivateKey(d.Bytes)
+	if err != nil {
+		return ErrCandNotParsePrivateKey
+	}
+	privateKey = key
+
+	// Domain required
+	if options.Domain == "" {
+		return ErrSignDomainRequired
+	}
+
+	// Selector required
+	if options.Selector == "" {
+		return ErrSignSelectorRequired
+	}
+
+	// Canonicalization
+	options.Canonicalization, err = validateCanonicalization(strings.ToLower(options.Canonicalization))
+	if err != nil {
+		return err
+	}
+
+	// Algo
+	options.Algo = strings.ToLower(options.Algo)
+	if options.Algo != "rsa-sha1" && options.Algo != "rsa-sha256" {
+		return ErrSignBadAlgo
+	}
+
+	// Header must contain "from"
+	hasFrom := false
+	for i, h := range options.Headers {
+		h = strings.ToLower(h)
+		options.Headers[i] = h
+		if h == "from" {
+			hasFrom = true
+		}
+	}
+	if !hasFrom {
+		return ErrSignHeaderShouldContainsFrom
+	}
+
+	// Normalize
+	headers, body, err := canonicalize(email, options.Canonicalization, options.Headers)
+	if err != nil {
+		return err
+	}
+
+	signHash := strings.Split(options.Algo, "-")
+
+	// hash body
+	bodyHash, err := getBodyHash(&body, signHash[1], options.BodyLength)
+	if err != nil {
+		return err
+	}
+
+	// Get dkim header base
+	dkimHeader := newDkimHeaderBySigOptions(options)
+	dHeader := dkimHeader.getHeaderBaseForSigning(bodyHash)
+
+	canonicalizations := strings.Split(options.Canonicalization, "/")
+	dHeaderCanonicalized, err := canonicalizeHeader(dHeader, canonicalizations[0])
+	if err != nil {
+		return err
+	}
+	headers = append(headers, []byte(dHeaderCanonicalized)...)
+	headers = bytes.TrimRight(headers, " \r\n")
+
+	// sign
+	sig, err := getSignature(&headers, privateKey, signHash[1])
+
+	// add to DKIM-Header
+	subh := ""
+	l := len(subh)
+	for _, c := range sig {
+		subh += string(c)
+		l++
+		if l >= MaxHeaderLineLength {
+			dHeader += subh + FWS
+			subh = ""
+			l = 0
+		}
+	}
+	dHeader += subh + CRLF
+	*email = append([]byte(dHeader), *email...)
+	return nil
+}
+
+// Verify verifies an email an return
+// state: SUCCESS or PERMFAIL or TEMPFAIL, TESTINGSUCCESS, TESTINGPERMFAIL
+// TESTINGTEMPFAIL or NOTSIGNED
+// error: if an error occurs during verification
+func Verify(email *[]byte, opts ...DNSOpt) (verifyOutput, error) {
+	// parse email
+	dkimHeader, err := newDkimHeaderFromEmail(email)
+	if err != nil {
+		if err == ErrDkimHeaderNotFound {
+			return NOTSIGNED, ErrDkimHeaderNotFound
+		}
+		return PERMFAIL, err
+	}
+
+	// we do not set query method because if it's others, validation failed earlier
+	pubKey, verifyOutputOnError, err := NewPubKeyRespFromDNS(dkimHeader.Selector, dkimHeader.Domain, opts...)
+	if err != nil {
+		// fix https://github.com/toorop/go-dkim/issues/1
+		//return getVerifyOutput(verifyOutputOnError, err, pubKey.FlagTesting)
+		return verifyOutputOnError, err
+	}
+
+	// Normalize
+	headers, body, err := canonicalize(email, dkimHeader.MessageCanonicalization, dkimHeader.Headers)
+	if err != nil {
+		return getVerifyOutput(PERMFAIL, err, pubKey.FlagTesting)
+	}
+	sigHash := strings.Split(dkimHeader.Algorithm, "-")
+	// check if hash algo are compatible
+	compatible := false
+	for _, algo := range pubKey.HashAlgo {
+		if sigHash[1] == algo {
+			compatible = true
+			break
+		}
+	}
+	if !compatible {
+		return getVerifyOutput(PERMFAIL, ErrVerifyInappropriateHashAlgo, pubKey.FlagTesting)
+	}
+
+	// expired ?
+	if !dkimHeader.SignatureExpiration.IsZero() && dkimHeader.SignatureExpiration.Second() < time.Now().Second() {
+		return getVerifyOutput(PERMFAIL, ErrVerifySignatureHasExpired, pubKey.FlagTesting)
+
+	}
+
+	//println("|" + string(body) + "|")
+	// get body hash
+	bodyHash, err := getBodyHash(&body, sigHash[1], dkimHeader.BodyLength)
+	if err != nil {
+		return getVerifyOutput(PERMFAIL, err, pubKey.FlagTesting)
+	}
+	//println(bodyHash)
+	if bodyHash != dkimHeader.BodyHash {
+		return getVerifyOutput(PERMFAIL, ErrVerifyBodyHash, pubKey.FlagTesting)
+	}
+
+	// compute sig
+	dkimHeaderCano, err := canonicalizeHeader(dkimHeader.RawForSign, strings.Split(dkimHeader.MessageCanonicalization, "/")[0])
+	if err != nil {
+		return getVerifyOutput(TEMPFAIL, err, pubKey.FlagTesting)
+	}
+	toSignStr := string(headers) + dkimHeaderCano
+	toSign := bytes.TrimRight([]byte(toSignStr), " \r\n")
+
+	err = verifySignature(toSign, dkimHeader.SignatureData, &pubKey.PubKey, sigHash[1])
+	if err != nil {
+		return getVerifyOutput(PERMFAIL, err, pubKey.FlagTesting)
+	}
+	return SUCCESS, nil
+}
+
+// getVerifyOutput returns output of verify fct according to the testing flag
+func getVerifyOutput(status verifyOutput, err error, flagTesting bool) (verifyOutput, error) {
+	if !flagTesting {
+		return status, err
+	}
+	switch status {
+	case SUCCESS:
+		return TESTINGSUCCESS, err
+	case PERMFAIL:
+		return TESTINGPERMFAIL, err
+	case TEMPFAIL:
+		return TESTINGTEMPFAIL, err
+	}
+	// should never happen but compilator sream whithout return
+	return status, err
+}
+
+// canonicalize returns canonicalized version of header and body
+func canonicalize(email *[]byte, cano string, h []string) (headers, body []byte, err error) {
+	body = []byte{}
+	rxReduceWS := regexp.MustCompile(`[ \t]+`)
+
+	rawHeaders, rawBody, err := getHeadersBody(email)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	canonicalizations := strings.Split(cano, "/")
+
+	// canonicalyze header
+	headersList, err := getHeadersList(&rawHeaders)
+
+	// pour chaque header a conserver on traverse tous les headers dispo
+	// If multi instance of a field we must keep it from the bottom to the top
+	var match *list.Element
+	headersToKeepList := list.New()
+
+	for _, headerToKeep := range h {
+		match = nil
+		headerToKeepToLower := strings.ToLower(headerToKeep)
+		for e := headersList.Front(); e != nil; e = e.Next() {
+			//fmt.Printf("|%s|\n", e.Value.(string))
+			t := strings.Split(e.Value.(string), ":")
+			if strings.ToLower(t[0]) == headerToKeepToLower {
+				match = e
+			}
+		}
+		if match != nil {
+			headersToKeepList.PushBack(match.Value.(string) + "\r\n")
+			headersList.Remove(match)
+		}
+	}
+
+	//if canonicalizations[0] == "simple" {
+	for e := headersToKeepList.Front(); e != nil; e = e.Next() {
+		cHeader, err := canonicalizeHeader(e.Value.(string), canonicalizations[0])
+		if err != nil {
+			return headers, body, err
+		}
+		headers = append(headers, []byte(cHeader)...)
+	}
+	// canonicalyze body
+	if canonicalizations[1] == "simple" {
+		// simple
+		// The "simple" body canonicalization algorithm ignores all empty lines
+		// at the end of the message body.  An empty line is a line of zero
+		// length after removal of the line terminator.  If there is no body or
+		// no trailing CRLF on the message body, a CRLF is added.  It makes no
+		// other changes to the message body.  In more formal terms, the
+		// "simple" body canonicalization algorithm converts "*CRLF" at the end
+		// of the body to a single "CRLF".
+		// Note that a completely empty or missing body is canonicalized as a
+		// single "CRLF"; that is, the canonicalized length will be 2 octets.
+		body = bytes.TrimRight(rawBody, "\r\n")
+		body = append(body, []byte{13, 10}...)
+	} else {
+		// relaxed
+		// Ignore all whitespace at the end of lines.  Implementations
+		// MUST NOT remove the CRLF at the end of the line.
+		// Reduce all sequences of WSP within a line to a single SP
+		// character.
+		// Ignore all empty lines at the end of the message body.  "Empty
+		// line" is defined in Section 3.4.3.  If the body is non-empty but
+		// does not end with a CRLF, a CRLF is added.  (For email, this is
+		// only possible when using extensions to SMTP or non-SMTP transport
+		// mechanisms.)
+		rawBody = rxReduceWS.ReplaceAll(rawBody, []byte(" "))
+		for _, line := range bytes.SplitAfter(rawBody, []byte{10}) {
+			line = bytes.TrimRight(line, " \r\n")
+			body = append(body, line...)
+			body = append(body, []byte{13, 10}...)
+		}
+		body = bytes.TrimRight(body, "\r\n")
+		body = append(body, []byte{13, 10}...)
+
+	}
+	return
+}
+
+// canonicalizeHeader returns canonicalized version of header
+func canonicalizeHeader(header string, algo string) (string, error) {
+	//rxReduceWS := regexp.MustCompile(`[ \t]+`)
+	if algo == "simple" {
+		// The "simple" header canonicalization algorithm does not change header
+		// fields in any way.  Header fields MUST be presented to the signing or
+		// verification algorithm exactly as they are in the message being
+		// signed or verified.  In particular, header field names MUST NOT be
+		// case folded and whitespace MUST NOT be changed.
+		return header, nil
+	} else if algo == "relaxed" {
+		// The "relaxed" header canonicalization algorithm MUST apply the
+		// following steps in order:
+
+		// Convert all header field names (not the header field values) to
+		// lowercase.  For example, convert "SUBJect: AbC" to "subject: AbC".
+
+		// Unfold all header field continuation lines as described in
+		// [RFC5322]; in particular, lines with terminators embedded in
+		// continued header field values (that is, CRLF sequences followed by
+		// WSP) MUST be interpreted without the CRLF.  Implementations MUST
+		// NOT remove the CRLF at the end of the header field value.
+
+		// Convert all sequences of one or more WSP characters to a single SP
+		// character.  WSP characters here include those before and after a
+		// line folding boundary.
+
+		// Delete all WSP characters at the end of each unfolded header field
+		// value.
+
+		// Delete any WSP characters remaining before and after the colon
+		// separating the header field name from the header field value.  The
+		// colon separator MUST be retained.
+		kv := strings.SplitN(header, ":", 2)
+		if len(kv) != 2 {
+			return header, ErrBadMailFormatHeaders
+		}
+		k := strings.ToLower(kv[0])
+		k = strings.TrimSpace(k)
+		v := removeFWS(kv[1])
+		//v = rxReduceWS.ReplaceAllString(v, " ")
+		//v = strings.TrimSpace(v)
+		return k + ":" + v + CRLF, nil
+	}
+	return header, ErrSignBadCanonicalization
+}
+
+// getBodyHash return the hash (bas64encoded) of the body
+func getBodyHash(body *[]byte, algo string, bodyLength uint) (string, error) {
+	var h hash.Hash
+	if algo == "sha1" {
+		h = sha1.New()
+	} else {
+		h = sha256.New()
+	}
+	toH := *body
+	// if l tag (body length)
+	if bodyLength != 0 {
+		if uint(len(toH)) < bodyLength {
+			return "", ErrBadDKimTagLBodyTooShort
+		}
+		toH = toH[0:bodyLength]
+	}
+
+	h.Write(toH)
+	return base64.StdEncoding.EncodeToString(h.Sum(nil)), nil
+}
+
+// getSignature return signature of toSign using key
+func getSignature(toSign *[]byte, key *rsa.PrivateKey, algo string) (string, error) {
+	var h1 hash.Hash
+	var h2 crypto.Hash
+	switch algo {
+	case "sha1":
+		h1 = sha1.New()
+		h2 = crypto.SHA1
+		break
+	case "sha256":
+		h1 = sha256.New()
+		h2 = crypto.SHA256
+		break
+	default:
+		return "", ErrVerifyInappropriateHashAlgo
+	}
+
+	// sign
+	h1.Write(*toSign)
+	sig, err := rsa.SignPKCS1v15(rand.Reader, key, h2, h1.Sum(nil))
+	if err != nil {
+		return "", err
+	}
+	return base64.StdEncoding.EncodeToString(sig), nil
+}
+
+// verifySignature verify signature from pubkey
+func verifySignature(toSign []byte, sig64 string, key *rsa.PublicKey, algo string) error {
+	var h1 hash.Hash
+	var h2 crypto.Hash
+	switch algo {
+	case "sha1":
+		h1 = sha1.New()
+		h2 = crypto.SHA1
+		break
+	case "sha256":
+		h1 = sha256.New()
+		h2 = crypto.SHA256
+		break
+	default:
+		return ErrVerifyInappropriateHashAlgo
+	}
+
+	h1.Write(toSign)
+	sig, err := base64.StdEncoding.DecodeString(sig64)
+	if err != nil {
+		return err
+	}
+	return rsa.VerifyPKCS1v15(key, h2, h1.Sum(nil), sig)
+}
+
+// removeFWS removes all FWS from string
+func removeFWS(in string) string {
+	rxReduceWS := regexp.MustCompile(`[ \t]+`)
+	out := strings.Replace(in, "\n", "", -1)
+	out = strings.Replace(out, "\r", "", -1)
+	out = rxReduceWS.ReplaceAllString(out, " ")
+	return strings.TrimSpace(out)
+}
+
+// validateCanonicalization validate canonicalization (c flag)
+func validateCanonicalization(cano string) (string, error) {
+	p := strings.Split(cano, "/")
+	if len(p) > 2 {
+		return "", ErrSignBadCanonicalization
+	}
+	if len(p) == 1 {
+		cano = cano + "/simple"
+	}
+	for _, c := range p {
+		if c != "simple" && c != "relaxed" {
+			return "", ErrSignBadCanonicalization
+		}
+	}
+	return cano, nil
+}
+
+// getHeadersList returns headers as list
+func getHeadersList(rawHeader *[]byte) (*list.List, error) {
+	headersList := list.New()
+	currentHeader := []byte{}
+	for _, line := range bytes.SplitAfter(*rawHeader, []byte{10}) {
+		if line[0] == 32 || line[0] == 9 {
+			if len(currentHeader) == 0 {
+				return headersList, ErrBadMailFormatHeaders
+			}
+			currentHeader = append(currentHeader, line...)
+		} else {
+			// New header, save current if exists
+			if len(currentHeader) != 0 {
+				headersList.PushBack(string(bytes.TrimRight(currentHeader, "\r\n")))
+				currentHeader = []byte{}
+			}
+			currentHeader = append(currentHeader, line...)
+		}
+	}
+	headersList.PushBack(string(currentHeader))
+	return headersList, nil
+}
+
+// getHeadersBody return headers and body
+func getHeadersBody(email *[]byte) ([]byte, []byte, error) {
+	substitutedEmail := *email
+
+	// only replace \n with \r\n when \r\n\r\n not exists
+	if bytes.Index(*email, []byte{13, 10, 13, 10}) < 0 {
+		// \n -> \r\n
+		substitutedEmail = bytes.Replace(*email, []byte{10}, []byte{13, 10}, -1)
+	}
+
+	parts := bytes.SplitN(substitutedEmail, []byte{13, 10, 13, 10}, 2)
+	if len(parts) != 2 {
+		return []byte{}, []byte{}, ErrBadMailFormat
+	}
+	// Empty body
+	if len(parts[1]) == 0 {
+		parts[1] = []byte{13, 10}
+	}
+	return parts[0], parts[1], nil
+}

vendor/github.com/toorop/go-dkim/dkimHeader.go

@@ -0,0 +1,545 @@
+package dkim
+
+import (
+	"bytes"
+	"fmt"
+	"net/mail"
+	"net/textproto"
+	"strconv"
+	"strings"
+	"time"
+)
+
+type dkimHeader struct {
+	// Version  This tag defines the version of DKIM
+	// specification that applies to the signature record.
+	// tag v
+	Version string
+
+	// The algorithm used to generate the signature..
+	// Verifiers MUST support "rsa-sha1" and "rsa-sha256";
+	// Signers SHOULD sign using "rsa-sha256".
+	// tag a
+	Algorithm string
+
+	// The signature data (base64).
+	// Whitespace is ignored in this value and MUST be
+	// ignored when reassembling the original signature.
+	// In particular, the signing process can safely insert
+	// FWS in this value in arbitrary places to conform to line-length
+	// limits.
+	// tag b
+	SignatureData string
+
+	// The hash of the canonicalized body part of the message as
+	// limited by the "l=" tag (base64; REQUIRED).
+	// Whitespace is ignored in this value and MUST be ignored when reassembling the original
+	// signature.  In particular, the signing process can safely insert
+	// FWS in this value in arbitrary places to conform to line-length
+	// limits.
+	// tag bh
+	BodyHash string
+
+	// Message canonicalization (plain-text; OPTIONAL, default is
+	//"simple/simple").  This tag informs the Verifier of the type of
+	// canonicalization used to prepare the message for signing.  It
+	// consists of two names separated by a "slash" (%d47) character,
+	// corresponding to the header and body canonicalization algorithms,
+	// respectively.  These algorithms are described in Section 3.4.  If
+	// only one algorithm is named, that algorithm is used for the header
+	// and "simple" is used for the body.  For example, "c=relaxed" is
+	// treated the same as "c=relaxed/simple".
+	// tag c
+	MessageCanonicalization string
+
+	// The SDID claiming responsibility for an introduction of a message
+	//  into the mail stream (plain-text; REQUIRED).  Hence, the SDID
+	//  value is used to form the query for the public key.  The SDID MUST
+	// correspond to a valid DNS name under which the DKIM key record is
+	// published.  The conventions and semantics used by a Signer to
+	// create and use a specific SDID are outside the scope of this
+	// specification, as is any use of those conventions and semantics.
+	// When presented with a signature that does not meet these
+	// requirements, Verifiers MUST consider the signature invalid.
+	// Internationalized domain names MUST be encoded as A-labels, as
+	// described in Section 2.3 of [RFC5890].
+	// tag d
+	Domain string
+
+	// Signed header fields (plain-text, but see description; REQUIRED).
+	// A colon-separated list of header field names that identify the
+	// header fields presented to the signing algorithm.  The field MUST
+	// contain the complete list of header fields in the order presented
+	// to the signing algorithm.  The field MAY contain names of header
+	// fields that do not exist when signed; nonexistent header fields do
+	// not contribute to the signature computation (that is, they are
+	// treated as the null input, including the header field name, the
+	// separating colon, the header field value, and any CRLF
+	// terminator).  The field MAY contain multiple instances of a header
+	// field name, meaning multiple occurrences of the corresponding
+	// header field are included in the header hash.  The field MUST NOT
+	// include the DKIM-Signature header field that is being created or
+	// verified but may include others.  Folding whitespace (FWS) MAY be
+	// included on either side of the colon separator.  Header field
+	// names MUST be compared against actual header field names in a
+	// case-insensitive manner.  This list MUST NOT be empty.  See
+	// Section 5.4 for a discussion of choosing header fields to sign and
+	// Section 5.4.2 for requirements when signing multiple instances of
+	// a single field.
+	// tag h
+	Headers []string
+
+	// The Agent or User Identifier (AUID) on behalf of which the SDID is
+	// taking responsibility (dkim-quoted-printable; OPTIONAL, default is
+	// an empty local-part followed by an "@" followed by the domain from
+	// the "d=" tag).
+	// The syntax is a standard email address where the local-part MAY be
+	// omitted.  The domain part of the address MUST be the same as, or a
+	// subdomain of, the value of the "d=" tag.
+	// Internationalized domain names MUST be encoded as A-labels, as
+	// described in Section 2.3 of [RFC5890].
+	// tag i
+	Auid string
+
+	// Body length count (plain-text unsigned decimal integer; OPTIONAL,
+	// default is entire body).  This tag informs the Verifier of the
+	// number of octets in the body of the email after canonicalization
+	// included in the cryptographic hash, starting from 0 immediately
+	// following the CRLF preceding the body.  This value MUST NOT be
+	// larger than the actual number of octets in the canonicalized
+	// message body.  See further discussion in Section 8.2.
+	// tag l
+	BodyLength uint
+
+	// A colon-separated list of query methods used to retrieve the
+	// public key (plain-text; OPTIONAL, default is "dns/txt").  Each
+	// query method is of the form "type[/options]", where the syntax and
+	// semantics of the options depend on the type and specified options.
+	// If there are multiple query mechanisms listed, the choice of query
+	// mechanism MUST NOT change the interpretation of the signature.
+	// Implementations MUST use the recognized query mechanisms in the
+	// order presented.  Unrecognized query mechanisms MUST be ignored.
+	// Currently, the only valid value is "dns/txt", which defines the
+	// DNS TXT resource record (RR) lookup algorithm described elsewhere
+	// in this document.  The only option defined for the "dns" query
+	// type is "txt", which MUST be included.  Verifiers and Signers MUST
+	// support "dns/txt".
+	// tag q
+	QueryMethods []string
+
+	// The selector subdividing the namespace for the "d=" (domain) tag
+	// (plain-text; REQUIRED).
+	// Internationalized selector names MUST be encoded as A-labels, as
+	// described in Section 2.3 of [RFC5890].
+	// tag s
+	Selector string
+
+	// Signature Timestamp (plain-text unsigned decimal integer;
+	// RECOMMENDED, default is an unknown creation time).  The time that
+	// this signature was created.  The format is the number of seconds
+	// since 00:00:00 on January 1, 1970 in the UTC time zone.  The value
+	// is expressed as an unsigned integer in decimal ASCII.  This value
+	// is not constrained to fit into a 31- or 32-bit integer.
+	// Implementations SHOULD be prepared to handle values up to at least
+	// 10^12 (until approximately AD 200,000; this fits into 40 bits).
+	// To avoid denial-of-service attacks, implementations MAY consider
+	// any value longer than 12 digits to be infinite.  Leap seconds are
+	// not counted.  Implementations MAY ignore signatures that have a
+	// timestamp in the future.
+	// tag t
+	SignatureTimestamp time.Time
+
+	// Signature Expiration (plain-text unsigned decimal integer;
+	// RECOMMENDED, default is no expiration).  The format is the same as
+	// in the "t=" tag, represented as an absolute date, not as a time
+	// delta from the signing timestamp.  The value is expressed as an
+	// unsigned integer in decimal ASCII, with the same constraints on
+	// the value in the "t=" tag.  Signatures MAY be considered invalid
+	// if the verification time at the Verifier is past the expiration
+	// date.  The verification time should be the time that the message
+	// was first received at the administrative domain of the Verifier if
+	// that time is reliably available; otherwise, the current time
+	// should be used.  The value of the "x=" tag MUST be greater than
+	// the value of the "t=" tag if both are present.
+	//tag x
+	SignatureExpiration time.Time
+
+	// Copied header fields (dkim-quoted-printable, but see description;
+	// OPTIONAL, default is null).  A vertical-bar-separated list of
+	// selected header fields present when the message was signed,
+	// including both the field name and value.  It is not required to
+	// include all header fields present at the time of signing.  This
+	// field need not contain the same header fields listed in the "h="
+	// tag.  The header field text itself must encode the vertical bar
+	// ("|", %x7C) character (i.e., vertical bars in the "z=" text are
+	// meta-characters, and any actual vertical bar characters in a
+	// copied header field must be encoded).  Note that all whitespace
+	// must be encoded, including whitespace between the colon and the
+	// header field value.  After encoding, FWS MAY be added at arbitrary
+	// locations in order to avoid excessively long lines; such
+	// whitespace is NOT part of the value of the header field and MUST
+	// be removed before decoding.
+	// The header fields referenced by the "h=" tag refer to the fields
+	// in the [RFC5322] header of the message, not to any copied fields
+	// in the "z=" tag.  Copied header field values are for diagnostic
+	// use.
+	// tag z
+	CopiedHeaderFields []string
+
+	// HeaderMailFromDomain store the raw email address of the header Mail From
+	// used for verifying in case of multiple DKIM header (we will prioritise
+	// header with d = mail from domain)
+	//HeaderMailFromDomain string
+
+	// RawForsign represents the raw part (without canonicalization) of the header
+	// used for computint sig in verify process
+	RawForSign string
+}
+
+// NewDkimHeaderBySigOptions return a new DkimHeader initioalized with sigOptions value
+func newDkimHeaderBySigOptions(options SigOptions) *dkimHeader {
+	h := new(dkimHeader)
+	h.Version = "1"
+	h.Algorithm = options.Algo
+	h.MessageCanonicalization = options.Canonicalization
+	h.Domain = options.Domain
+	h.Headers = options.Headers
+	h.Auid = options.Auid
+	h.BodyLength = options.BodyLength
+	h.QueryMethods = options.QueryMethods
+	h.Selector = options.Selector
+	if options.AddSignatureTimestamp {
+		h.SignatureTimestamp = time.Now()
+	}
+	if options.SignatureExpireIn > 0 {
+		h.SignatureExpiration = time.Now().Add(time.Duration(options.SignatureExpireIn) * time.Second)
+	}
+	h.CopiedHeaderFields = options.CopiedHeaderFields
+	return h
+}
+
+// NewFromEmail return a new DkimHeader by parsing an email
+// Note: according to RFC 6376 an email can have multiple DKIM Header
+// in this case we return the last inserted or the last with d== mail from
+func newDkimHeaderFromEmail(email *[]byte) (*dkimHeader, error) {
+	m, err := mail.ReadMessage(bytes.NewReader(*email))
+	if err != nil {
+		return nil, err
+	}
+
+	// DKIM header ?
+	if len(m.Header[textproto.CanonicalMIMEHeaderKey("DKIM-Signature")]) == 0 {
+		return nil, ErrDkimHeaderNotFound
+	}
+
+	// Get mail from domain
+	mailFromDomain := ""
+	mailfrom, err := mail.ParseAddress(m.Header.Get(textproto.CanonicalMIMEHeaderKey("From")))
+	if err != nil {
+		if err.Error() != "mail: no address" {
+			return nil, err
+		}
+	} else {
+		t := strings.SplitAfter(mailfrom.Address, "@")
+		if len(t) > 1 {
+			mailFromDomain = strings.ToLower(t[1])
+		}
+	}
+
+	// get raw dkim header
+	// we can't use m.header because header key will be converted with textproto.CanonicalMIMEHeaderKey
+	// ie if key in header is not DKIM-Signature but Dkim-Signature or DKIM-signature ot... other
+	// combination of case, verify will fail.
+	rawHeaders, _, err := getHeadersBody(email)
+	if err != nil {
+		return nil, ErrBadMailFormat
+	}
+	rawHeadersList, err := getHeadersList(&rawHeaders)
+	if err != nil {
+		return nil, err
+	}
+	dkHeaders := []string{}
+	for h := rawHeadersList.Front(); h != nil; h = h.Next() {
+		if strings.HasPrefix(strings.ToLower(h.Value.(string)), "dkim-signature") {
+			dkHeaders = append(dkHeaders, h.Value.(string))
+		}
+	}
+
+	var keep *dkimHeader
+	var keepErr error
+	//for _, dk := range m.Header[textproto.CanonicalMIMEHeaderKey("DKIM-Signature")] {
+	for _, h := range dkHeaders {
+		parsed, err := parseDkHeader(h)
+		// if malformed dkim header try next
+		if err != nil {
+			keepErr = err
+			continue
+		}
+		// Keep first dkim headers
+		if keep == nil {
+			keep = parsed
+		}
+		// if d flag == domain keep this header and return
+		if mailFromDomain == parsed.Domain {
+			return parsed, nil
+		}
+	}
+	if keep == nil {
+		return nil, keepErr
+	}
+	return keep, nil
+}
+
+// parseDkHeader parse raw dkim header
+func parseDkHeader(header string) (dkh *dkimHeader, err error) {
+	dkh = new(dkimHeader)
+
+	keyVal := strings.SplitN(header, ":", 2)
+
+	t := strings.LastIndex(header, "b=")
+	if t == -1 {
+		return nil, ErrDkimHeaderBTagNotFound
+	}
+	dkh.RawForSign = header[0 : t+2]
+	p := strings.IndexByte(header[t:], ';')
+	if p != -1 {
+		dkh.RawForSign = dkh.RawForSign + header[t+p:]
+	}
+
+	// Mandatory
+	mandatoryFlags := make(map[string]bool, 7) //(b'v', b'a', b'b', b'bh', b'd', b'h', b's')
+	mandatoryFlags["v"] = false
+	mandatoryFlags["a"] = false
+	mandatoryFlags["b"] = false
+	mandatoryFlags["bh"] = false
+	mandatoryFlags["d"] = false
+	mandatoryFlags["h"] = false
+	mandatoryFlags["s"] = false
+
+	// default values
+	dkh.MessageCanonicalization = "simple/simple"
+	dkh.QueryMethods = []string{"dns/txt"}
+
+	// unfold && clean
+	val := removeFWS(keyVal[1])
+	val = strings.Replace(val, " ", "", -1)
+
+	fs := strings.Split(val, ";")
+	for _, f := range fs {
+		if f == "" {
+			continue
+		}
+		flagData := strings.SplitN(f, "=", 2)
+
+		// https://github.com/toorop/go-dkim/issues/2
+		// if flag is not in the form key=value (eg doesn't have "=")
+		if len(flagData) != 2 {
+			return nil, ErrDkimHeaderBadFormat
+		}
+		flag := strings.ToLower(strings.TrimSpace(flagData[0]))
+		data := strings.TrimSpace(flagData[1])
+		switch flag {
+		case "v":
+			if data != "1" {
+				return nil, ErrDkimVersionNotsupported
+			}
+			dkh.Version = data
+			mandatoryFlags["v"] = true
+		case "a":
+			dkh.Algorithm = strings.ToLower(data)
+			if dkh.Algorithm != "rsa-sha1" && dkh.Algorithm != "rsa-sha256" {
+				return nil, ErrSignBadAlgo
+			}
+			mandatoryFlags["a"] = true
+		case "b":
+			//dkh.SignatureData = removeFWS(data)
+			// remove all space
+			dkh.SignatureData = strings.Replace(removeFWS(data), " ", "", -1)
+			if len(dkh.SignatureData) != 0 {
+				mandatoryFlags["b"] = true
+			}
+		case "bh":
+			dkh.BodyHash = removeFWS(data)
+			if len(dkh.BodyHash) != 0 {
+				mandatoryFlags["bh"] = true
+			}
+		case "d":
+			dkh.Domain = strings.ToLower(data)
+			if len(dkh.Domain) != 0 {
+				mandatoryFlags["d"] = true
+			}
+		case "h":
+			data = strings.ToLower(data)
+			dkh.Headers = strings.Split(data, ":")
+			if len(dkh.Headers) != 0 {
+				mandatoryFlags["h"] = true
+			}
+			fromFound := false
+			for _, h := range dkh.Headers {
+				if h == "from" {
+					fromFound = true
+				}
+			}
+			if !fromFound {
+				return nil, ErrDkimHeaderNoFromInHTag
+			}
+		case "s":
+			dkh.Selector = strings.ToLower(data)
+			if len(dkh.Selector) != 0 {
+				mandatoryFlags["s"] = true
+			}
+		case "c":
+			dkh.MessageCanonicalization, err = validateCanonicalization(strings.ToLower(data))
+			if err != nil {
+				return nil, err
+			}
+		case "i":
+			if data != "" {
+				if !strings.HasSuffix(data, dkh.Domain) {
+					return nil, ErrDkimHeaderDomainMismatch
+				}
+				dkh.Auid = data
+			}
+		case "l":
+			ui, err := strconv.ParseUint(data, 10, 32)
+			if err != nil {
+				return nil, err
+			}
+			dkh.BodyLength = uint(ui)
+		case "q":
+			dkh.QueryMethods = strings.Split(data, ":")
+			if len(dkh.QueryMethods) == 0 || strings.ToLower(dkh.QueryMethods[0]) != "dns/txt" {
+				return nil, errQueryMethodNotsupported
+			}
+		case "t":
+			ts, err := strconv.ParseInt(data, 10, 64)
+			if err != nil {
+				return nil, err
+			}
+			dkh.SignatureTimestamp = time.Unix(ts, 0)
+
+		case "x":
+			ts, err := strconv.ParseInt(data, 10, 64)
+			if err != nil {
+				return nil, err
+			}
+			dkh.SignatureExpiration = time.Unix(ts, 0)
+		case "z":
+			dkh.CopiedHeaderFields = strings.Split(data, "|")
+		}
+	}
+
+	// All mandatory flags are in ?
+	for _, p := range mandatoryFlags {
+		if !p {
+			return nil, ErrDkimHeaderMissingRequiredTag
+		}
+	}
+
+	// default for i/Auid
+	if dkh.Auid == "" {
+		dkh.Auid = "@" + dkh.Domain
+	}
+
+	// defaut for query method
+	if len(dkh.QueryMethods) == 0 {
+		dkh.QueryMethods = []string{"dns/text"}
+	}
+
+	return dkh, nil
+
+}
+
+// GetHeaderBase return base header for signers
+// Todo: some refactoring needed...
+func (d *dkimHeader) getHeaderBaseForSigning(bodyHash string) string {
+	h := "DKIM-Signature: v=" + d.Version + "; a=" + d.Algorithm + "; q=" + strings.Join(d.QueryMethods, ":") + "; c=" + d.MessageCanonicalization + ";" + CRLF + TAB
+	subh := "s=" + d.Selector + ";"
+	if len(subh)+len(d.Domain)+4 > MaxHeaderLineLength {
+		h += subh + FWS
+		subh = ""
+	}
+	subh += " d=" + d.Domain + ";"
+
+	// Auid
+	if len(d.Auid) != 0 {
+		if len(subh)+len(d.Auid)+4 > MaxHeaderLineLength {
+			h += subh + FWS
+			subh = ""
+		}
+		subh += " i=" + d.Auid + ";"
+	}
+
+	/*h := "DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=tmail.io; i=@tmail.io;" + FWS
+	subh := "q=dns/txt; s=test;"*/
+
+	// signature timestamp
+	if !d.SignatureTimestamp.IsZero() {
+		ts := d.SignatureTimestamp.Unix()
+		if len(subh)+14 > MaxHeaderLineLength {
+			h += subh + FWS
+			subh = ""
+		}
+		subh += " t=" + fmt.Sprintf("%d", ts) + ";"
+	}
+	if len(subh)+len(d.Domain)+4 > MaxHeaderLineLength {
+		h += subh + FWS
+		subh = ""
+	}
+
+	// Expiration
+	if !d.SignatureExpiration.IsZero() {
+		ts := d.SignatureExpiration.Unix()
+		if len(subh)+14 > MaxHeaderLineLength {
+			h += subh + FWS
+			subh = ""
+		}
+		subh += " x=" + fmt.Sprintf("%d", ts) + ";"
+	}
+
+	// body length
+	if d.BodyLength != 0 {
+		bodyLengthStr := fmt.Sprintf("%d", d.BodyLength)
+		if len(subh)+len(bodyLengthStr)+4 > MaxHeaderLineLength {
+			h += subh + FWS
+			subh = ""
+		}
+		subh += " l=" + bodyLengthStr + ";"
+	}
+
+	// Headers
+	if len(subh)+len(d.Headers)+4 > MaxHeaderLineLength {
+		h += subh + FWS
+		subh = ""
+	}
+	subh += " h="
+	for _, header := range d.Headers {
+		if len(subh)+len(header)+1 > MaxHeaderLineLength {
+			h += subh + FWS
+			subh = ""
+		}
+		subh += header + ":"
+	}
+	subh = subh[:len(subh)-1] + ";"
+
+	// BodyHash
+	if len(subh)+5+len(bodyHash) > MaxHeaderLineLength {
+		h += subh + FWS
+		subh = ""
+	} else {
+		subh += " "
+	}
+	subh += "bh="
+	l := len(subh)
+	for _, c := range bodyHash {
+		subh += string(c)
+		l++
+		if l >= MaxHeaderLineLength {
+			h += subh + FWS
+			subh = ""
+			l = 0
+		}
+	}
+	h += subh + ";" + FWS + "b="
+	return h
+}

vendor/github.com/toorop/go-dkim/errors.go

@@ -0,0 +1,94 @@
+package dkim
+
+import (
+	"errors"
+)
+
+var (
+	// ErrSignPrivateKeyRequired when there not private key in config
+	ErrSignPrivateKeyRequired = errors.New("PrivateKey is required")
+
+	// ErrSignDomainRequired when there is no domain defined in config
+	ErrSignDomainRequired = errors.New("Domain is required")
+
+	// ErrSignSelectorRequired when there is no Selcteir defined in config
+	ErrSignSelectorRequired = errors.New("Selector is required")
+
+	// ErrSignHeaderShouldContainsFrom If Headers is specified it should at least contain 'from'
+	ErrSignHeaderShouldContainsFrom = errors.New("header must contains 'from' field")
+
+	// ErrSignBadCanonicalization If bad Canonicalization parameter
+	ErrSignBadCanonicalization = errors.New("bad Canonicalization parameter")
+
+	// ErrCandNotParsePrivateKey when unable to parse private key
+	ErrCandNotParsePrivateKey = errors.New("can not parse private key, check format (pem) and validity")
+
+	// ErrSignBadAlgo Bad algorithm
+	ErrSignBadAlgo = errors.New("bad algorithm. Only rsa-sha1 or rsa-sha256 are permitted")
+
+	// ErrBadMailFormat unable to parse mail
+	ErrBadMailFormat = errors.New("bad mail format")
+
+	// ErrBadMailFormatHeaders bad headers format (not DKIM Header)
+	ErrBadMailFormatHeaders = errors.New("bad mail format found in headers")
+
+	// ErrBadDKimTagLBodyTooShort bad l tag
+	ErrBadDKimTagLBodyTooShort = errors.New("bad tag l or bodyLength option. Body length < l value")
+
+	// ErrDkimHeaderBadFormat when errors found in DKIM header
+	ErrDkimHeaderBadFormat = errors.New("bad DKIM header format")
+
+	// ErrDkimHeaderNotFound when there's no DKIM-Signature header in an email we have to verify
+	ErrDkimHeaderNotFound = errors.New("no DKIM-Signature header field found ")
+
+	// ErrDkimHeaderBTagNotFound when there's no b tag
+	ErrDkimHeaderBTagNotFound = errors.New("no tag 'b' found in dkim header")
+
+	// ErrDkimHeaderNoFromInHTag when from is missing in h tag
+	ErrDkimHeaderNoFromInHTag = errors.New("'from' header is missing in h tag")
+
+	// ErrDkimHeaderMissingRequiredTag when a required tag is missing
+	ErrDkimHeaderMissingRequiredTag = errors.New("signature missing required tag")
+
+	// ErrDkimHeaderDomainMismatch if i tag is not a sub domain of d tag
+	ErrDkimHeaderDomainMismatch = errors.New("domain mismatch")
+
+	// ErrDkimVersionNotsupported version not supported
+	ErrDkimVersionNotsupported = errors.New("incompatible version")
+
+	// Query method unsupported
+	errQueryMethodNotsupported = errors.New("query method not supported")
+
+	// ErrVerifyBodyHash when body hash doesn't verify
+	ErrVerifyBodyHash = errors.New("body hash did not verify")
+
+	// ErrVerifyNoKeyForSignature no key
+	ErrVerifyNoKeyForSignature = errors.New("no key for verify")
+
+	// ErrVerifyKeyUnavailable when service (dns) is anavailable
+	ErrVerifyKeyUnavailable = errors.New("key unavailable")
+
+	// ErrVerifyTagVMustBeTheFirst if present the v tag must be the firts in the record
+	ErrVerifyTagVMustBeTheFirst = errors.New("pub key syntax error: v tag must be the first")
+
+	// ErrVerifyVersionMusBeDkim1 if présent flag v (version) must be DKIM1
+	ErrVerifyVersionMusBeDkim1 = errors.New("flag v must be set to DKIM1")
+
+	// ErrVerifyBadKeyType bad type for pub key (only rsa is accepted)
+	ErrVerifyBadKeyType = errors.New("bad type for key type")
+
+	// ErrVerifyRevokedKey key(s) for this selector is revoked (p is empty)
+	ErrVerifyRevokedKey = errors.New("revoked key")
+
+	// ErrVerifyBadKey when we can't parse pubkey
+	ErrVerifyBadKey = errors.New("unable to parse pub key")
+
+	// ErrVerifyNoKey when no key is found on DNS record
+	ErrVerifyNoKey = errors.New("no public key found in DNS TXT")
+
+	// ErrVerifySignatureHasExpired when signature has expired
+	ErrVerifySignatureHasExpired = errors.New("signature has expired")
+
+	// ErrVerifyInappropriateHashAlgo when h tag in pub key doesn't contain hash algo from a tag of DKIM header
+	ErrVerifyInappropriateHashAlgo = errors.New("inappropriate has algorithm")
+)

vendor/github.com/toorop/go-dkim/pubKeyRep.go

@@ -0,0 +1,181 @@
+package dkim
+
+import (
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/base64"
+	"io/ioutil"
+	"mime/quotedprintable"
+	"net"
+	"strings"
+)
+
+// PubKeyRep represents a parsed version of public key record
+type PubKeyRep struct {
+	Version      string
+	HashAlgo     []string
+	KeyType      string
+	Note         string
+	PubKey       rsa.PublicKey
+	ServiceType  []string
+	FlagTesting  bool // flag y
+	FlagIMustBeD bool // flag i
+}
+
+// DNSOptions holds settings for looking up DNS records
+type DNSOptions struct {
+	netLookupTXT func(name string) ([]string, error)
+}
+
+// DNSOpt represents an optional setting for looking up DNS records
+type DNSOpt interface {
+	apply(*DNSOptions)
+}
+
+type dnsOpt func(*DNSOptions)
+
+func (opt dnsOpt) apply(dnsOpts *DNSOptions) {
+	opt(dnsOpts)
+}
+
+// DNSOptLookupTXT sets the function to use to lookup TXT records.
+//
+// This should probably only be used in tests.
+func DNSOptLookupTXT(netLookupTXT func(name string) ([]string, error)) DNSOpt {
+	return dnsOpt(func(opts *DNSOptions) {
+		opts.netLookupTXT = netLookupTXT
+	})
+}
+
+// NewPubKeyRespFromDNS retrieves the TXT record from DNS based on the specified domain and selector
+// and parses it.
+func NewPubKeyRespFromDNS(selector, domain string, opts ...DNSOpt) (*PubKeyRep, verifyOutput, error) {
+	dnsOpts := DNSOptions{}
+
+	for _, opt := range opts {
+		opt.apply(&dnsOpts)
+	}
+
+	if dnsOpts.netLookupTXT == nil {
+		dnsOpts.netLookupTXT = net.LookupTXT
+	}
+
+	txt, err := dnsOpts.netLookupTXT(selector + "._domainkey." + domain)
+	if err != nil {
+		if strings.HasSuffix(err.Error(), "no such host") {
+			return nil, PERMFAIL, ErrVerifyNoKeyForSignature
+		}
+
+		return nil, TEMPFAIL, ErrVerifyKeyUnavailable
+	}
+
+	// empty record
+	if len(txt) == 0 {
+		return nil, PERMFAIL, ErrVerifyNoKeyForSignature
+	}
+
+	// parsing, we keep the first record
+	// TODO: if there is multiple record
+
+	return NewPubKeyResp(txt[0])
+}
+
+// NewPubKeyResp parses DKIM record (usually from DNS)
+func NewPubKeyResp(dkimRecord string) (*PubKeyRep, verifyOutput, error) {
+	pkr := new(PubKeyRep)
+	pkr.Version = "DKIM1"
+	pkr.HashAlgo = []string{"sha1", "sha256"}
+	pkr.KeyType = "rsa"
+	pkr.FlagTesting = false
+	pkr.FlagIMustBeD = false
+
+	p := strings.Split(dkimRecord, ";")
+	for i, data := range p {
+		keyVal := strings.SplitN(data, "=", 2)
+		val := ""
+		if len(keyVal) > 1 {
+			val = strings.TrimSpace(keyVal[1])
+		}
+		switch strings.ToLower(strings.TrimSpace(keyVal[0])) {
+		case "v":
+			// RFC: is this tag is specified it MUST be the first in the record
+			if i != 0 {
+				return nil, PERMFAIL, ErrVerifyTagVMustBeTheFirst
+			}
+			pkr.Version = val
+			if pkr.Version != "DKIM1" {
+				return nil, PERMFAIL, ErrVerifyVersionMusBeDkim1
+			}
+		case "h":
+			p := strings.Split(strings.ToLower(val), ":")
+			pkr.HashAlgo = []string{}
+			for _, h := range p {
+				h = strings.TrimSpace(h)
+				if h == "sha1" || h == "sha256" {
+					pkr.HashAlgo = append(pkr.HashAlgo, h)
+				}
+			}
+			// if empty switch back to default
+			if len(pkr.HashAlgo) == 0 {
+				pkr.HashAlgo = []string{"sha1", "sha256"}
+			}
+		case "k":
+			if strings.ToLower(val) != "rsa" {
+				return nil, PERMFAIL, ErrVerifyBadKeyType
+			}
+		case "n":
+			qp, err := ioutil.ReadAll(quotedprintable.NewReader(strings.NewReader(val)))
+			if err == nil {
+				val = string(qp)
+			}
+			pkr.Note = val
+		case "p":
+			rawkey := val
+			if rawkey == "" {
+				return nil, PERMFAIL, ErrVerifyRevokedKey
+			}
+			un64, err := base64.StdEncoding.DecodeString(rawkey)
+			if err != nil {
+				return nil, PERMFAIL, ErrVerifyBadKey
+			}
+			pk, err := x509.ParsePKIXPublicKey(un64)
+			if pk, ok := pk.(*rsa.PublicKey); ok {
+				pkr.PubKey = *pk
+			}
+		case "s":
+			t := strings.Split(strings.ToLower(val), ":")
+			for _, tt := range t {
+				tt = strings.TrimSpace(tt)
+				switch tt {
+				case "*":
+					pkr.ServiceType = append(pkr.ServiceType, "all")
+				case "email":
+					pkr.ServiceType = append(pkr.ServiceType, tt)
+				}
+			}
+		case "t":
+			flags := strings.Split(strings.ToLower(val), ":")
+			for _, flag := range flags {
+				flag = strings.TrimSpace(flag)
+				switch flag {
+				case "y":
+					pkr.FlagTesting = true
+				case "s":
+					pkr.FlagIMustBeD = true
+				}
+			}
+		}
+	}
+
+	// if no pubkey
+	if pkr.PubKey == (rsa.PublicKey{}) {
+		return nil, PERMFAIL, ErrVerifyNoKey
+	}
+
+	// No service type
+	if len(pkr.ServiceType) == 0 {
+		pkr.ServiceType = []string{"all"}
+	}
+
+	return pkr, SUCCESS, nil
+}

vendor/github.com/toorop/go-dkim/watch

@@ -0,0 +1,4 @@
+while true
+do 
+inotifywait -q -r -e modify,attrib,close_write,move,create,delete . && echo "--------------" && go test -v
+done

vendor/modules.txt

@@ -59,6 +59,9 @@ github.com/tidwall/rtree
 github.com/tidwall/rtree/base
 # github.com/tidwall/tinyqueue v0.0.0-20180302190814-1e39f5511563
 github.com/tidwall/tinyqueue
+# github.com/toorop/go-dkim v0.0.0-20191019073156-897ad64a2eeb
+## explicit
+github.com/toorop/go-dkim
 # golang.org/x/crypto v0.0.0-20200302210943-78000ba7a073
 ## explicit
 golang.org/x/crypto/bcrypt