Add basic mail / auth server

.gitignore

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+*~
+*.swp
+*.log
+run.sh
+burner

auth/server.go

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+package auth
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"regexp"
+
+	"github.com/thebaer/burner/validate"
+)
+
+// Serve starts an HTTP server that handles auth requests from nginx.
+func Serve(port int) error {
+	if port <= 0 {
+		return errors.New("auth server: Invalid port number.")
+	}
+	serverPort = port
+
+	mailInfo := log.New(os.Stdout, "", log.Ldate|log.Ltime)
+	mailInfo.Printf("Starting mail auth server on :%d", serverPort)
+
+	http.HandleFunc("/auth", authHandler)
+	http.ListenAndServe(fmt.Sprintf("127.0.0.1:%d", serverPort), nil)
+
+	return nil
+}
+
+var (
+	// Port that the auth server will run on.
+	serverPort int
+
+	// Regular expression for matching / finding a valid To address.
+	smtpEmailReg = regexp.MustCompile("<(.+)>")
+)
+
+// authHandler works with nginx to determine whether or not a receipient email
+// address is valid. If it is, running mail server's information is passed
+// back.
+func authHandler(w http.ResponseWriter, r *http.Request) {
+	toHeader := r.Header.Get("Auth-SMTP-To")
+	if toHeader == "" {
+		w.Header().Set("Auth-Status", "Unrecognized receipient.")
+		w.Header().Set("Auth-Error-Code", "550")
+		return
+	}
+
+	to := smtpEmailReg.FindStringSubmatch(toHeader)[1]
+	if to == "" {
+		w.Header().Set("Auth-Status", "Unrecognized receipient.")
+		w.Header().Set("Auth-Error-Code", "550")
+		return
+	}
+	if err := validate.Email(to); err != nil {
+		// Email address validation failed
+		w.Header().Set("Auth-Status", err.Error())
+		w.Header().Set("Auth-Error-Code", "550")
+		return
+	}
+
+	// Email passed validation, send back mail server information
+	w.Header().Set("Auth-Status", "OK")
+	w.Header().Set("Auth-Server", "127.0.0.1")
+	w.Header().Set("Auth-Port", fmt.Sprintf("%d", serverPort))
+}

database/database.go

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+package database
+
+import (
+	"database/sql"
+	"errors"
+	"fmt"
+	"os"
+
+	_ "github.com/go-sql-driver/mysql"
+)
+
+type (
+	DB struct {
+		*sql.DB
+	}
+	Tx struct {
+		*sql.Tx
+	}
+)
+
+func Open() (*DB, error) {
+	// Get database configuration
+	dbUser := os.Getenv("DB_USER")
+	dbPassword := os.Getenv("DB_PASSWORD")
+	dbName := os.Getenv("DB_DB")
+	dbHost := os.Getenv("DB_HOST")
+
+	if dbUser == "" || dbPassword == "" {
+		return nil, errors.New("Database user or password not set.")
+	}
+	if dbHost == "" {
+		dbHost = "localhost"
+	}
+	if dbName == "" {
+		dbName = "burnermail"
+	}
+
+	db, err := sql.Open("mysql", fmt.Sprintf("%s:%s@tcp(%s:3306)/%s?charset=utf8mb4&parseTime=true", dbUser, dbPassword, dbHost, dbName))
+	if err != nil {
+		return nil, err
+	}
+	db.SetMaxOpenConns(250)
+
+	return &DB{db}, nil
+}

mail.go

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+package main
+
+import (
+	"flag"
+	"log"
+
+	"github.com/thebaer/burner/auth"
+	"github.com/thebaer/burner/database"
+	"github.com/thebaer/burner/mail"
+)
+
+var host = flag.String("h", "example.com", "Domain this service lives on.")
+
+func main() {
+	// Parse configuration flags and validate
+	flag.Parse()
+	if *host == "example.com" {
+		log.Printf("WARNING: Default hostname (example.com) unchanged. Use -h flag to set correct host.")
+	}
+
+	// Connect to database
+	db, err := database.Open()
+	if err != nil {
+		panic(err)
+	}
+	defer db.Close()
+
+	// TODO: make port numbers configurable
+	go func() {
+		auth.Serve(8080)
+	}()
+
+	mail.Serve(*host, 2525)
+}

mail/mail.go

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+package mail
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"mime"
+	"mime/multipart"
+	"net"
+	"net/mail"
+	"os"
+	"strings"
+
+	"github.com/mhale/smtpd"
+	"github.com/thebaer/burner/validate"
+)
+
+var (
+	mailInfo  *log.Logger
+	mailError *log.Logger
+)
+
+type MailConfig struct {
+	Port int
+	Host string
+}
+
+var mailCfg *MailConfig
+
+func Serve(host string, port int) error {
+	mailCfg = &MailConfig{
+		Port: port,
+		Host: host,
+	}
+
+	// Set up variables
+	mailInfo = log.New(os.Stdout, "", log.Ldate|log.Ltime)
+	mailError = log.New(os.Stderr, "ERROR: ", log.Ldate|log.Ltime|log.Lshortfile)
+
+	// Start mail server
+	mailInfo.Printf("Starting %s mail server on :%d", mailCfg.Host, mailCfg.Port)
+	err := smtpd.ListenAndServe(fmt.Sprintf(":%d", mailCfg.Port), mailHandler, mailCfg.Host, mailCfg.Host)
+	if err != nil {
+		mailError.Printf("Couldn't start mail server: %v", err)
+		return err
+	}
+
+	return nil
+}
+
+func mailHandler(origin net.Addr, from string, to []string, data []byte) {
+	msg, err := mail.ReadMessage(bytes.NewReader(data))
+	if err != nil {
+		mailError.Printf("Couldn't read email message: %v", err)
+		return
+	}
+
+	var content []byte
+	subject := msg.Header.Get("Subject")
+	contentType, params, err := mime.ParseMediaType(msg.Header.Get("Content-Type"))
+	if err != nil {
+		mailError.Printf("Couldn't parse Content-Type: %v", err)
+	}
+	if strings.HasPrefix(contentType, "multipart/") {
+		mr := multipart.NewReader(msg.Body, params["boundary"])
+		for {
+			p, err := mr.NextPart()
+			if err == io.EOF {
+				break
+			}
+			if err != nil {
+				mailError.Printf("Error getting NextPart(): %v", err)
+				continue
+			}
+			if !strings.HasPrefix(p.Header.Get("Content-Type"), "text/plain") {
+				continue
+			}
+
+			// We correctly read the text/plain section of email
+			content, err = ioutil.ReadAll(p)
+			if err != nil {
+				mailError.Printf("Error in ReadAll on part: %v", err)
+			}
+			break
+		}
+	} else {
+		var err error
+		content, err = ioutil.ReadAll(msg.Body)
+		if err != nil {
+			mailError.Printf("Couldn't read email body: %v", err)
+			return
+		}
+	}
+
+	mailInfo.Printf("Received mail from %s for %s with subject %s", from, to[0], subject)
+
+	createPostFromEmail(to[0], subject, from, content)
+}
+
+func createPostFromEmail(to, subject, from string, content []byte) {
+	if err := validate.Email(to); err != nil {
+		return
+	}
+}

validate/mail.go

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+package validate
+
+import (
+	"errors"
+	"strings"
+)
+
+// Friendly user-facing errors
+var (
+	errBadEmail = errors.New("User doesn't exist.")
+)
+
+// Email does basic validation on the intended receiving address. It returns a
+// friendly error message that can be served directly to connecting clients if
+// validation fails.
+func Email(to string) error {
+	host := to[strings.IndexRune(to, '@')+1:]
+	// TODO: use given configurable host (don't hardcode)
+	if host != "writ.es" {
+		return errBadEmail
+	}
+
+	toName := to[:strings.IndexRune(to, '@')]
+	if toName == "anyone" {
+		return nil
+	}
+
+	if len(toName) != 32 {
+		return errBadEmail
+	}
+
+	return nil
+}