README
¶
A SMTP Server Package 
a simple smtp server library, forked from This repo but I refactored it to be more advanced and organized
Features
- Very simple
- Automated SPF Checks
- Automated
FROMvalidation (MXchecking), viaRequest.Mailable - Supports TLS
- Modular, as you can add more smtp command processors to extend the functionality as you need
Quick Start
go get github.com/alash3al/go-smtpsrv
package main
import (
"fmt"
"github.com/alash3al/go-smtpsrv"
)
func main() {
handler := func(req *smtpsrv.Request) error {
// ...
return nil
}
srv := &smtpsrv.Server{
Name: "mail.my.server",
Addr: ":25025",
MaxBodySize: 5 * 1024,
Handler: handler,
}
fmt.Println(srv.ListenAndServe())
}
Security
The smtp server also supports the STARTTLS option, if you use the ListenAndServeTLS variant.
You can also further customize the tls config as well.
server := smtp.Server{Name: "example.com", Debug: true}
config := &tls.Config{MinVersion:tls.VersionSSL30}
server.TLSConfig = config
log.Fatal(server.ListenAndServeTLS(":smtp", "cert.pem", "key.pem", nil))
Authentication
The smtp server also supports authentication via the PLAIN method. Ideally this would be coupled with STARTTLS to ensure secrecy of passwords in transit. You can do this by creating a custom server and registering the AUTH callback. This will be called everytime someone attempts to authenticate.
server.Auth = func(username, password, remoteAddress string) error {
if username == "user" && password == "p@$$w0rd" {
return nil
}
return errors.New("Nope!")
}
Addressing and preventing open-relay
Since your callback is only called once the smtp protocol has progressed to the data point, meaning the sender and recipient have been specified, the server also offers an Addressable callback that can be used to deny unknown recipients.
server.Addressable = func(user, address string) bool {
if user != ""{
//Allow relay for authenticated users
return true
}
if strings.HasSuffix(address, "example.com"){
return true
}
return false
}
Documentation
¶
Index ¶
- Variables
- func CanonicalizeEmail(local string) string
- func LimitDataSize(r io.Reader, s int64) io.Reader
- func ListenAndServe(addr string, handler Handler) error
- func ListenAndServeTLS(addr, certFile, keyFile string, handler Handler) error
- func SplitAddress(address string) (string, string, error)
- type Handler
- type Processor
- type Request
- type Server
Constants ¶
This section is empty.
Variables ¶
var ( // ErrorRequestedActionAbortedLocalError .. ErrorRequestedActionAbortedLocalError = errors.New("Requested action aborted: local error in processing") // ErrorTransactionFailed .. ErrorTransactionFailed = errors.New("Transaction failed") // ErrorServiceNotAvailable .. ErrorServiceNotAvailable = errors.New("Service not available, closing transmission channel") // ErrorRequestedActionAbortedExceededStorage .. ErrorRequestedActionAbortedExceededStorage = errors.New("Requested mail action aborted: exceeded storage allocation") )
var ( // DefaultProcessors holds processor functions DefaultProcessors = map[string]Processor{ "EHLO": ehloProcessor, "HELO": ehloProcessor, "STARTTLS": starttlsProcessor, "AUTH": authProcessor, "MAIL": mailProcessor, "RCPT": rcptProcessor, "DATA": dataProcessor, "RSET": rsetProcessor, "VRFY": vrfyProcessor, "EXPN": expnProcessor, "HELP": helpProcessor, "NOOP": noopProcessor, "QUIT": quitProcessor, } )
Functions ¶
func CanonicalizeEmail ¶
CanonicalizeEmail format the specified email address I'm following googles example here. Basically all '.' dont matter in the local portion. Also you can append a '+' section to the end of your email and it will still route to you. This allows categorization of emails when they are given out. The muxer will canonicalize incoming email addresses to route them to a handler. The handler will still see the original email in the to portion.
func LimitDataSize ¶
LimitDataSize Limit the incoming data size of the DATA command
func ListenAndServe ¶
ListenAndServe start listening on the specified addr using the specified handler
func ListenAndServeTLS ¶
ListenAndServeTLS start listening on the specified addr using the specified handler and tls configs
Types ¶
type Request ¶
type Request struct {
// the currently running server
Server *Server
// the underlying socket for currently connected client
Conn net.Conn
// an instance of go stdlib for handling the above Conn as a text-porotocol
TextProto *textproto.Conn
// TLS related info
TLSState *tls.ConnectionState
// a shortcut for Conn.RemoteAddr()
RemoteAddr string
// contains the hostname of the currently connected client during the EHLO/HELO command
HelloHost string
// whether EHLO/HELO called or not
HelloRecieved bool
// the login username used for login, empty means that this is an anonymous attempt
AuthUser string
// the user that sends the mail
From string
// the rctps!
To []string
// the body of the mail "DATA command" but parsed
Message *mail.Message
// whether the client called QUIT or not
QuitSent bool
// whether to check the from domain
DisableFromChecks bool
// the spf checking result
SPFResult spf.Result
// whether the FROM mail is mailable or not
Mailable bool
// the currently processing line
Line []string
}
Request is the incoming connection meta-data
func NewRequest ¶
NewRequest creates a new instance of the Request struct
type Server ¶
type Server struct {
// The name of the server used while greeting
Name string
// The address to listen on
Addr string
// The default inbox handler
Handler Handler
// If a tls config is set then this server will broadcast support
// for the STARTTLS (RFC3207) extension.
TLSConfig *tls.Config
// Auth specifies an optional callback function that is called
// when a client attempts to authenticate. If left nil (the default)
// then the AUTH extension will not be supported.
Auth func(username, password, remoteAddress string) error
// Addressable specifies an optional callback function that is called
// when a client attempts to send a message to the given address. This
// allows the server to refuse messages that it doesn't own. If left nil
// (the default) then the server will assume true
Addressable func(user, address string) bool
// Processors is a map of current supported commands' processor for incomming
// SMTP messages/lines.
Processors map[string]Processor
// Maximum size of the DATA command in bytes
MaxBodySize int64
DisableFromChecks bool
}
Server is our main server handler
func (*Server) ListenAndServe ¶
ListenAndServe start serving the incoming data
func (*Server) ListenAndServeTLS ¶
ListenAndServeTLS start serving the incoming tls connection
Source Files