go-mail/client.go

505 lines
12 KiB
Go

package mail
import (
"context"
"crypto/tls"
"errors"
"fmt"
"github.com/wneessen/go-mail/auth"
"net"
"net/smtp"
"os"
"strings"
"time"
)
// Defaults
const (
// DefaultPort is the default connection port cto the SMTP server
DefaultPort = 25
// DefaultTimeout is the default connection timeout
DefaultTimeout = time.Second * 15
// DefaultTLSPolicy is the default STARTTLS policy
DefaultTLSPolicy = TLSMandatory
// DefaultTLSMinVersion is the minimum TLS version required for the connection
// Nowadays TLS1.2 should be the sane default
DefaultTLSMinVersion = tls.VersionTLS12
)
// Client is the SMTP client struct
type Client struct {
// Hostname of the target SMTP server cto connect cto
host string
// Port of the SMTP server cto connect cto
port int
// Use SSL for the connection
ssl bool
// tlspolicy sets the client to use the provided TLSPolicy for the STARTTLS protocol
tlspolicy TLSPolicy
// tlsconfig represents the tls.Config setting for the STARTTLS connection
tlsconfig *tls.Config
// Timeout for the SMTP server connection
cto time.Duration
// HELO/EHLO string for the greeting the target SMTP server
helo string
// enc indicates if a Client connection is encrypted or not
enc bool
// user is the SMTP AUTH username
user string
// pass is the corresponding SMTP AUTH password
pass string
// satype represents the authentication type for SMTP AUTH
satype SMTPAuthType
// co is the net.Conn that the smtp.Client is based on
co net.Conn
// sa is a pointer to smtp.Auth
sa smtp.Auth
// sc is the smtp.Client that is set up when using the Dial*() methods
sc *smtp.Client
}
// Option returns a function that can be used for grouping Client options
type Option func(*Client) error
var (
// ErrInvalidPort should be used if a port is specified that is not valid
ErrInvalidPort = errors.New("invalid port number")
// ErrInvalidTimeout should be used if a timeout is set that is zero or negative
ErrInvalidTimeout = errors.New("timeout cannot be zero or negative")
// ErrInvalidHELO should be used if an empty HELO sting is provided
ErrInvalidHELO = errors.New("invalid HELO/EHLO value - must not be empty")
// ErrInvalidTLSConfig should be used if an empty tls.Config is provided
ErrInvalidTLSConfig = errors.New("invalid TLS config")
// ErrNoHostname should be used if a Client has no hostname set
ErrNoHostname = errors.New("hostname for client cannot be empty")
// ErrDeadlineExtendFailed should be used if the extension of the connection deadline fails
ErrDeadlineExtendFailed = errors.New("connection deadline extension failed")
// ErrNoActiveConnection should be used when a method is used that requies a server connection
// but is not yet connected
ErrNoActiveConnection = errors.New("not connected to SMTP server")
// ErrServerNoUnencoded should be used when 8BIT encoding is selected for a message, but
// the server does not offer 8BITMIME mode
ErrServerNoUnencoded = errors.New("message is 8bit unencoded, but server does not support 8BITMIME")
)
// NewClient returns a new Session client object
func NewClient(h string, o ...Option) (*Client, error) {
c := &Client{
cto: DefaultTimeout,
host: h,
port: DefaultPort,
tlsconfig: &tls.Config{ServerName: h, MinVersion: DefaultTLSMinVersion},
tlspolicy: DefaultTLSPolicy,
}
// Set default HELO/EHLO hostname
if err := c.setDefaultHelo(); err != nil {
return c, err
}
// Override defaults with optionally provided Option functions
for _, co := range o {
if co == nil {
continue
}
if err := co(c); err != nil {
return c, fmt.Errorf("failed to apply option: %w", err)
}
}
// Some settings in a Client cannot be empty/unset
if c.host == "" {
return c, ErrNoHostname
}
return c, nil
}
// WithPort overrides the default connection port
func WithPort(p int) Option {
return func(c *Client) error {
if p < 1 || p > 65535 {
return ErrInvalidPort
}
c.port = p
return nil
}
}
// WithTimeout overrides the default connection timeout
func WithTimeout(t time.Duration) Option {
return func(c *Client) error {
if t <= 0 {
return ErrInvalidTimeout
}
c.cto = t
return nil
}
}
// WithSSL tells the client to use a SSL/TLS connection
func WithSSL() Option {
return func(c *Client) error {
c.ssl = true
return nil
}
}
// WithHELO tells the client to use the provided string as HELO/EHLO greeting host
func WithHELO(h string) Option {
return func(c *Client) error {
if h == "" {
return ErrInvalidHELO
}
c.helo = h
return nil
}
}
// WithTLSPolicy tells the client to use the provided TLSPolicy
func WithTLSPolicy(p TLSPolicy) Option {
return func(c *Client) error {
c.tlspolicy = p
return nil
}
}
// WithTLSConfig tells the client to use the provided *tls.Config
func WithTLSConfig(co *tls.Config) Option {
return func(c *Client) error {
if co == nil {
return ErrInvalidTLSConfig
}
c.tlsconfig = co
return nil
}
}
// WithSMTPAuth tells the client to use the provided SMTPAuthType for authentication
func WithSMTPAuth(t SMTPAuthType) Option {
return func(c *Client) error {
c.satype = t
return nil
}
}
// WithSMTPAuthCustom tells the client to use the provided smtp.Auth for SMTP authentication
func WithSMTPAuthCustom(a smtp.Auth) Option {
return func(c *Client) error {
c.sa = a
return nil
}
}
// WithUsername tells the client to use the provided string as username for authentication
func WithUsername(u string) Option {
return func(c *Client) error {
c.user = u
return nil
}
}
// WithPassword tells the client to use the provided string as password/secret for authentication
func WithPassword(p string) Option {
return func(c *Client) error {
c.pass = p
return nil
}
}
// TLSPolicy returns the currently set TLSPolicy as string
func (c *Client) TLSPolicy() string {
return c.tlspolicy.String()
}
// ServerAddr returns the currently set combination of hostname and port
func (c *Client) ServerAddr() string {
return fmt.Sprintf("%s:%d", c.host, c.port)
}
// SetTLSPolicy overrides the current TLSPolicy with the given TLSPolicy value
func (c *Client) SetTLSPolicy(p TLSPolicy) {
c.tlspolicy = p
}
// SetSSL tells the Client wether to use SSL or not
func (c *Client) SetSSL(s bool) {
c.ssl = s
}
// SetTLSConfig overrides the current *tls.Config with the given *tls.Config value
func (c *Client) SetTLSConfig(co *tls.Config) error {
if co == nil {
return ErrInvalidTLSConfig
}
c.tlsconfig = co
return nil
}
// SetUsername overrides the current username string with the given value
func (c *Client) SetUsername(u string) {
c.user = u
}
// SetPassword overrides the current password string with the given value
func (c *Client) SetPassword(p string) {
c.pass = p
}
// SetSMTPAuth overrides the current SMTP AUTH type setting with the given value
func (c *Client) SetSMTPAuth(a SMTPAuthType) {
c.satype = a
}
// SetSMTPAuthCustom overrides the current SMTP AUTH setting with the given custom smtp.Auth
func (c *Client) SetSMTPAuthCustom(sa smtp.Auth) {
c.sa = sa
}
// setDefaultHelo retrieves the current hostname and sets it as HELO/EHLO hostname
func (c *Client) setDefaultHelo() error {
hn, err := os.Hostname()
if err != nil {
return fmt.Errorf("failed cto read local hostname: %w", err)
}
c.helo = hn
return nil
}
// DialWithContext establishes a connection cto the SMTP server with a given context.Context
func (c *Client) DialWithContext(pc context.Context) error {
ctx, cfn := context.WithDeadline(pc, time.Now().Add(c.cto))
defer cfn()
nd := net.Dialer{}
td := tls.Dialer{}
var err error
if c.ssl {
c.enc = true
c.co, err = td.DialContext(ctx, "tcp", c.ServerAddr())
}
if !c.ssl {
c.co, err = nd.DialContext(ctx, "tcp", c.ServerAddr())
}
if err != nil {
return err
}
c.sc, err = smtp.NewClient(c.co, c.host)
if err != nil {
return err
}
if err := c.sc.Hello(c.helo); err != nil {
return err
}
if err := c.tls(); err != nil {
return err
}
if err := c.auth(); err != nil {
return err
}
return nil
}
// Send sends out the mail message
func (c *Client) Send(ml ...*Msg) error {
if err := c.checkConn(); err != nil {
return fmt.Errorf("failed to send mail: %w", err)
}
for _, m := range ml {
if m.encoding == NoEncoding {
if ok, _ := c.sc.Extension("8BITMIME"); !ok {
return ErrServerNoUnencoded
}
}
f, err := m.GetSender(false)
if err != nil {
return err
}
rl, err := m.GetRecipients()
if err != nil {
return err
}
if err := c.sc.Mail(f); err != nil {
return fmt.Errorf("sending MAIL FROM command failed: %w", err)
}
for _, r := range rl {
if err := c.sc.Rcpt(r); err != nil {
return fmt.Errorf("sending RCPT TO command failed: %w", err)
}
}
w, err := c.sc.Data()
if err != nil {
return fmt.Errorf("sending DATA command failed: %w", err)
}
_, err = m.WriteTo(w)
if err != nil {
return fmt.Errorf("sending mail content failed: %w", err)
}
if err := w.Close(); err != nil {
return fmt.Errorf("failed to close DATA writer: %w", err)
}
if err := c.Reset(); err != nil {
return fmt.Errorf("sending RSET command failed: %s", err)
}
if err := c.checkConn(); err != nil {
return fmt.Errorf("failed to check server connection: %w", err)
}
}
return nil
}
// Close closes the Client connection
func (c *Client) Close() error {
if err := c.checkConn(); err != nil {
return err
}
if err := c.sc.Quit(); err != nil {
return fmt.Errorf("failed to close SMTP client: %w", err)
}
return nil
}
// Reset sends the RSET command to the SMTP client
func (c *Client) Reset() error {
if err := c.checkConn(); err != nil {
return err
}
if err := c.sc.Reset(); err != nil {
return fmt.Errorf("failed to send RSET to SMTP client: %w", err)
}
return nil
}
// DialAndSend establishes a connection to the SMTP server with a
// default context.Background and sends the mail
func (c *Client) DialAndSend(ml ...*Msg) error {
ctx := context.Background()
if err := c.DialWithContext(ctx); err != nil {
return fmt.Errorf("dial failed: %w", err)
}
if err := c.Send(ml...); err != nil {
return fmt.Errorf("send failed: %w", err)
}
if err := c.Close(); err != nil {
return fmt.Errorf("failed to close connction: %s", err)
}
return nil
}
// checkConn makes sure that a required server connection is available and extends the
// connection deadline
func (c *Client) checkConn() error {
if c.co == nil {
return ErrNoActiveConnection
}
if err := c.sc.Noop(); err != nil {
return ErrNoActiveConnection
}
if err := c.co.SetDeadline(time.Now().Add(c.cto)); err != nil {
return ErrDeadlineExtendFailed
}
return nil
}
// tls tries to make sure that the STARTTLS requirements are satisfied
func (c *Client) tls() error {
if c.co == nil {
return ErrNoActiveConnection
}
if !c.ssl && c.tlspolicy != NoTLS {
est := false
st, _ := c.sc.Extension("STARTTLS")
if c.tlspolicy == TLSMandatory {
est = true
if !st {
return fmt.Errorf("STARTTLS mode set to: %q, but target host does not support STARTTLS",
c.tlspolicy)
}
}
if c.tlspolicy == TLSOpportunistic {
if st {
est = true
}
}
if est {
if err := c.sc.StartTLS(c.tlsconfig); err != nil {
return err
}
}
_, c.enc = c.sc.TLSConnectionState()
}
return nil
}
// auth will try to perform SMTP AUTH if requested
func (c *Client) auth() error {
if err := c.checkConn(); err != nil {
return fmt.Errorf("failed to authenticate: %w", err)
}
if c.sa == nil && c.satype != "" {
sa, sat := c.sc.Extension("AUTH")
if !sa {
return fmt.Errorf("server does not support SMTP AUTH")
}
switch c.satype {
case SMTPAuthPlain:
if !strings.Contains(sat, string(SMTPAuthPlain)) {
return ErrPlainAuthNotSupported
}
c.sa = smtp.PlainAuth("", c.user, c.pass, c.host)
case SMTPAuthLogin:
if !strings.Contains(sat, string(SMTPAuthLogin)) {
return ErrLoginAuthNotSupported
}
c.sa = auth.LoginAuth(c.user, c.pass, c.host)
case SMTPAuthCramMD5:
if !strings.Contains(sat, string(SMTPAuthCramMD5)) {
return ErrCramMD5AuthNotSupported
}
c.sa = smtp.CRAMMD5Auth(c.user, c.pass)
default:
return fmt.Errorf("unsupported SMTP AUTH type %q", c.satype)
}
}
if c.sa != nil {
if err := c.sc.Auth(c.sa); err != nil {
return fmt.Errorf("SMTP AUTH failed: %w", err)
}
}
return nil
}