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list.go
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list.go
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package ulist
import (
"bytes"
"crypto/hmac"
"crypto/sha256"
"encoding/base64"
"errors"
"fmt"
"net/mail"
"strconv"
"time"
"github.com/wansing/ulist/mailutil"
"github.com/wansing/ulist/txt"
)
var ErrLink = errors.New("link is invalid or expired") // HMAC related, don't leak the reason
type List struct {
ListInfo
HMACKey []byte // [32]byte would require check when reading from database
PublicSignup bool // default: false
HideFrom bool // default: false
ActionMod Action
ActionMember Action
ActionKnown Action
ActionUnknown Action
}
var sentJoinCheckbacks = make(map[string]int64) // RFC5322AddrSpec => unix time
var sentLeaveCheckbacks = make(map[string]int64) // RFC5322AddrSpec => unix time
// CreateHMAC creates an HMAC with a given user email address and the current time. The HMAC is returned as a base64 RawURLEncoding string.
func (list *List) CreateHMAC(addr *Addr) (int64, string, error) {
var now = time.Now().Unix()
var hmac, err = list.createHMAC(addr, now)
return now, base64.RawURLEncoding.EncodeToString(hmac), err
}
// ValidateHMAC validates an HMAC. If the given timestamp is older than maxAgeDays, then ErrLink is returned.
func (list *List) ValidateHMAC(inputHMAC []byte, addr *Addr, timestamp int64, maxAgeDays int) error {
expectedHMAC, err := list.createHMAC(addr, timestamp)
if err != nil {
return err
}
if !hmac.Equal(inputHMAC, expectedHMAC) {
return ErrLink
}
if timestamp < time.Now().AddDate(0, 0, -1*maxAgeDays).Unix() {
return ErrLink
}
return nil
}
// addr can be nil
func (list *List) createHMAC(addr *Addr, timestamp int64) ([]byte, error) {
if len(list.HMACKey) == 0 {
return nil, errors.New("hmac: key is empty")
}
if bytes.Equal(list.HMACKey, make([]byte, 32)) {
return nil, errors.New("hmac: key is all zeroes")
}
mac := hmac.New(sha256.New, list.HMACKey)
mac.Write([]byte(list.RFC5322AddrSpec()))
mac.Write([]byte{0}) // separator
if addr != nil {
mac.Write([]byte(addr.RFC5322AddrSpec()))
mac.Write([]byte{0}) // separator
}
mac.Write([]byte(strconv.FormatInt(timestamp, 10)))
return mac.Sum(nil), nil
}
// GetAction determines the maximum action of an email by the "From" addresses and possible spam headers. It also returns a human-readable reason for the decision.
//
// The SMTP envelope sender is ignored, because it's actually something different and a case for the spam filtering system.
// (Mailman incorporates it last, which is probably never, because each email must have a From header: https://mail.python.org/pipermail/mailman-users/2017-January/081797.html)
func (u *Ulist) GetAction(list *List, header mail.Header, froms []*Addr) (Action, string, error) {
var action = list.ActionUnknown
var reason string
if action == Pass {
reason = `list allows any "From" address`
} else {
reason = `all "From" addresses are unknown`
for _, from := range froms {
statuses, err := u.GetRoles(list, from)
if err != nil {
return Reject, "", fmt.Errorf("error getting status from database: %v", err)
}
for _, status := range statuses {
var fromAction Action = Reject
switch status {
case Known:
fromAction = list.ActionKnown
case Member:
fromAction = list.ActionMember
case Moderator:
fromAction = list.ActionMod
}
if action < fromAction {
action = fromAction
reason = fmt.Sprintf("%s is %s", from, status)
}
}
}
}
// Pass becomes Mod if the email has a positive spam header
if action == Pass {
if isSpam, spamReason := mailutil.IsSpam(header); isSpam {
action = Mod
reason = fmt.Sprintf("%s, but %s", reason, spamReason)
}
}
return action, reason, nil
}
// SendJoinCheckback does not check the authorization of the asking person. This must be done by the caller.
func (u *Ulist) SendJoinCheckback(list *List, recipient *Addr) error {
// rate limiting
if lastSentTimestamp, ok := sentJoinCheckbacks[recipient.RFC5322AddrSpec()]; ok {
if lastSentTimestamp < time.Now().AddDate(0, 0, 7).Unix() {
return fmt.Errorf("A join request has already been sent to %v. In order to prevent spamming, requests can be sent every seven days only.", recipient)
}
}
if m, err := u.Lists.GetMembership(list, recipient); err == nil {
if m.Member { // already a member
return nil // Let's return nil (after rate limiting!), so we don't reveal the subscription. Timing might still leak information.
}
} else {
return err
}
// create mail
var url, err = u.CheckbackJoinUrl(list, recipient)
if err != nil {
return err
}
data := txt.CheckbackJoinData{
ListAddress: list.RFC5322AddrSpec(),
MailAddress: recipient.RFC5322AddrSpec(),
Url: url,
}
body := &bytes.Buffer{}
if err = txt.CheckbackJoin.Execute(body, data); err != nil {
return err
}
if err = u.Notify(list, recipient.RFC5322AddrSpec(), fmt.Sprintf("Please confirm: join the mailing list %s", list), body); err != nil {
return err
}
sentJoinCheckbacks[recipient.RFC5322AddrSpec()] = time.Now().Unix()
return nil
}
// SendLeaveCheckback sends a checkback email if the user is a member of the list.
//
// If the user is not a member, the returned error is nil, so it doesn't reveal about the membership. However both timing and other errors can still reveal it.
//
// The returned bool value indicates whether the email was sent.
func (u *Ulist) SendLeaveCheckback(list *List, user *Addr) (bool, error) {
// rate limiting
if lastSentTimestamp, ok := sentLeaveCheckbacks[user.RFC5322AddrSpec()]; ok {
if lastSentTimestamp < time.Now().AddDate(0, 0, 7).Unix() {
return false, fmt.Errorf("A leave request has already been sent to %v. In order to prevent spamming, requests can be sent every seven days only.", user)
}
}
if m, err := u.Lists.GetMembership(list, user); err == nil {
if !m.Member { // not a member
return false, nil // err is nil and does not reveal about the membership
}
} else {
return false, err
}
// create mail
var url, err = u.CheckbackLeaveUrl(list, user)
if err != nil {
return false, err
}
data := txt.CheckbackLeaveData{
ListAddress: list.RFC5322AddrSpec(),
MailAddress: user.RFC5322AddrSpec(),
Url: url,
}
body := &bytes.Buffer{}
if err = txt.CheckbackLeave.Execute(body, data); err != nil {
return false, err
}
if err = u.Notify(list, user.RFC5322AddrSpec(), fmt.Sprintf("Please confirm: leave the mailing list %s", list), body); err != nil {
return false, err
}
sentLeaveCheckbacks[user.RFC5322AddrSpec()] = time.Now().Unix()
return true, nil
}
func (list *List) SignoffLeaveMessage() ([]byte, error) {
var buf = &bytes.Buffer{}
var err = txt.SignoffLeave.Execute(buf, list.RFC5322AddrSpec())
return buf.Bytes(), err
}