Initial commit

.gitignore

@@ -0,0 +1,2 @@
+.idea
+lda

go.mod

@@ -0,0 +1,5 @@
+module lmtpdelivery
+
+go 1.15
+
+require github.com/emersion/go-smtp v0.14.0

go.sum

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+github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21 h1:OJyUGMJTzHTd1XQp98QTaHernxMYzRaOasRir9hUlFQ=
+github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
+github.com/emersion/go-smtp v0.14.0 h1:RYW203p+EcPjL8Z/ZpT9lZ6iOc8MG1MQzEx1UKEkXlA=
+github.com/emersion/go-smtp v0.14.0/go.mod h1:qm27SGYgoIPRot6ubfQ/GpiPy/g3PaZAVRxiO/sDUgQ=

lda.go

@@ -0,0 +1,107 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"github.com/emersion/go-smtp"
+	"io"
+	"net"
+	"os"
+	"regexp"
+	"strings"
+)
+
+func sendMail(from string, to string, socket string) (err error) {
+	conn, err := net.Dial("unix", socket)
+	if err != nil {
+		_, _ = fmt.Fprintf(os.Stderr, "Failed opening the socket <%s>: %s", socket, err)
+		return err
+	}
+	client, err := smtp.NewClientLMTP(conn, "localhost")
+	if err != nil {
+		_, _ = fmt.Fprintf(os.Stderr, "Failed establishing the connection: %s", err)
+		return err
+	}
+	defer func() {
+		quitErr := client.Quit()
+		if quitErr != nil {
+			_, _ = fmt.Fprintf(os.Stderr, "Failed closing the connection: %s", quitErr)
+		}
+	}()
+	err = client.Mail(from, &smtp.MailOptions{})
+	if err != nil {
+		_, _ = fmt.Fprintf(os.Stderr, "Failed establishing the envelope FROM <%s>: %s", from, err)
+		return err
+	}
+	err = client.Rcpt(to)
+	if err != nil {
+		_, _ = fmt.Fprintf(os.Stderr, "Failed establishing the envelope FROM <%s> TO <%s>: %s", from, to, err)
+		return err
+	}
+	var sendError *smtp.SMTPError
+	writer, err := client.LMTPData(func(rcpt string, status *smtp.SMTPError) {
+		if status != nil {
+			sendError = status
+			_, _ = fmt.Fprintf(os.Stderr, "Failed sending the message FROM <%s> TO <%s>: %s", from, rcpt, status)
+		}
+	})
+	if err != nil {
+		_, _ = fmt.Fprintf(os.Stderr, "Failed opening the writing stream FROM <%s> TO <%s>: %s", from, to, err)
+		return err
+	}
+	_, err = io.Copy(writer, os.Stdin)
+	if err != nil {
+		_, _ = fmt.Fprintf(os.Stderr, "Failed copying the message FROM <%s> TO <%s> data: %s", from, to, err)
+		return err
+	}
+	err = writer.Close()
+	if err != nil {
+		_, _ = fmt.Fprintf(os.Stderr, "Failed closing the writing stream FROM <%s> TO <%s>: %s", from, to, err)
+		return err
+	}
+	if sendError != nil {
+		return sendError
+	}
+	return nil
+}
+
+var UnwrapRe = regexp.MustCompile("^.*\\s*<([^<>]+)>\\s*$")
+
+func unwrap(from string) string {
+	result := UnwrapRe.FindStringSubmatch(from)
+	if result == nil {
+		return from
+	}
+	return result[1]
+}
+
+func escapeAts(from string) string {
+	count := strings.Count(from, "@")
+	if count <= 1 {
+		return from
+	}
+	return strings.Replace(from, "@", ".at.", count - 1)
+}
+
+func main() {
+	from := flag.String("from", "", "The original envelope sender of the message.")
+	to := flag.String("to", "", "The envelope recipient of the message.")
+	socket := flag.String("socket", "/var/run/dovecot/lmtp", "The LMTP Unix socket to send on.")
+	escapeDoubledAts := flag.Bool("escapeDoubledAts", true, "True to escape multiple @ symbols.")
+	unwrapFrom := flag.Bool("unwrapBrackets", true, "True to unwrap unnecessary <> symbols.")
+	replaceUnknown := flag.Bool("replaceUnknown", true, "True to replace 'unknown' with a default value")
+	flag.Parse()
+
+	if *unwrapFrom {
+		*from = unwrap(*from)
+	}
+	if *escapeDoubledAts {
+		*from = escapeAts(*from)
+	}
+	if *replaceUnknown && *from == "unknown" {
+		*from = "unknown@unknown.invalid"
+	}
+	if err := sendMail(*from, *to, *socket); err != nil {
+		os.Exit(1)
+	}
+}