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-rw-r--r--serve_mx.go264
1 files changed, 264 insertions, 0 deletions
diff --git a/serve_mx.go b/serve_mx.go
new file mode 100644
index 0000000..f3c1527
--- /dev/null
+++ b/serve_mx.go
@@ -0,0 +1,264 @@
+package main
+
+import (
+ "bufio"
+ "bytes"
+ "context"
+ "crypto/tls"
+ "errors"
+ "io"
+ "net"
+ "slices"
+ "strings"
+
+ "github.com/jackc/pgx/v5/pgxpool"
+ "go.lindenii.runxiyu.org/lindenii-common/mailkit"
+ "go.lindenii.runxiyu.org/lindenii-common/clog"
+)
+
+type server_state_t uint
+
+const (
+ server_state_begin server_state_t = iota
+ server_state_helo
+ server_state_mail
+ server_state_rcpt
+)
+
+type mx_recv_session struct {
+ buf_conn *bufio.ReadWriter
+ net_conn net.Conn
+ tls_conn *tls.Conn
+ my_server_name string
+ tls_config *tls.Config
+ db *pgxpool.Pool
+ remote_server_name string
+ current_mail_from string
+ current_rcpt_to []string
+ server_state server_state_t
+}
+
+func (session *mx_recv_session) handle(ctx context.Context) error {
+ session.buf_conn = bufio.NewReadWriter(bufio.NewReader(session.net_conn), bufio.NewWriter(session.net_conn))
+ config_consistent_run(func() {
+ session.my_server_name = config.Server_name
+ session.tls_config = config._tls_config
+ session.db = global_db
+ })
+ _, _ = session.buf_conn.WriteString("220 " + session.my_server_name + " " + VERSION + "\r\n")
+ _ = session.buf_conn.Flush()
+ session.server_state = server_state_begin
+ for {
+ line, err := session.buf_conn.ReadString('\n')
+ if err != nil {
+ if err == io.EOF {
+ return err_connection_handler_eof
+ }
+ return err
+ }
+ line = strings.TrimSuffix(line, "\n")
+ line = strings.TrimSuffix(line, "\r")
+ cmd_end := strings.IndexByte(line, ' ')
+ var param_start int
+ if cmd_end == -1 {
+ cmd_end = len(line)
+ param_start = len(line)
+ } else {
+ param_start = cmd_end + 1
+ }
+ cmd := strings.ToUpper(line[:cmd_end])
+ param := line[param_start:]
+ switch_cmd:
+ switch cmd {
+ case "STARTTLS":
+ if param != "" {
+ _, _ = session.buf_conn.WriteString("501 5.5.4 Syntax error (no parameters allowed)\r\n")
+ _ = session.buf_conn.Flush()
+ break
+ }
+ if session.tls_conn != nil {
+ _, _ = session.buf_conn.WriteString("554 5.5.1 Error: TLS already active\r\n")
+ _ = session.buf_conn.Flush()
+ break
+ }
+ _, _ = session.buf_conn.WriteString("220 2.0.0 Ready to start TLS\r\n")
+ _ = session.buf_conn.Flush()
+ session.tls_conn = tls.Server(session.net_conn, session.tls_config)
+ session.buf_conn = bufio.NewReadWriter(bufio.NewReader(session.tls_conn), bufio.NewWriter(session.tls_conn))
+ session.server_state = server_state_begin
+ session.current_mail_from = ""
+ session.current_rcpt_to = []string{""}
+ case "HELO":
+ if param == "" { // TODO: actually validate the hostname
+ _, _ = session.buf_conn.WriteString("501 Syntax: HELO hostname\r\n")
+ _ = session.buf_conn.Flush()
+ break
+ }
+ session.remote_server_name = param
+ _ = session.remote_server_name // TODO
+ session.server_state = server_state_helo
+ _, _ = session.buf_conn.WriteString("250 " + session.my_server_name + "\r\n")
+ _ = session.buf_conn.Flush()
+ case "MAIL":
+ switch session.server_state {
+ case server_state_begin:
+ _, _ = session.buf_conn.WriteString("503 5.5.1 Error: send HELO/EHLO first\r\n")
+ _ = session.buf_conn.Flush()
+ break switch_cmd
+ case server_state_helo:
+ break
+ case server_state_mail:
+ _, _ = session.buf_conn.WriteString("503 5.5.1 Error: nested MAIL command\r\n")
+ _ = session.buf_conn.Flush()
+ break switch_cmd
+ }
+ if len(param) <= len("FROM:") || strings.ToUpper(param[:len("FROM:")]) != "FROM:" {
+ _, _ = session.buf_conn.WriteString("501 5.5.4 Syntax: MAIL FROM:<address>\r\n")
+ _ = session.buf_conn.Flush()
+ break
+ }
+ session.current_mail_from = param[len("FROM:"):]
+ session.current_rcpt_to = []string{}
+ session.server_state = server_state_mail
+ _, _ = session.buf_conn.WriteString("250 2.1.0 Ok\r\n")
+ _ = session.buf_conn.Flush()
+ // TODO: Address validation
+ case "RCPT":
+ if session.server_state != server_state_mail && session.server_state != server_state_rcpt {
+ _, _ = session.buf_conn.WriteString("503 5.5.1 Error: need MAIL command\r\n")
+ _ = session.buf_conn.Flush()
+ break
+ }
+ if len(param) <= len("TO:") || strings.ToUpper(param[:len("TO:")]) != "TO:" {
+ _, _ = session.buf_conn.WriteString("501 5.5.4 Syntax: RCPT TO:<address>\r\n")
+ _ = session.buf_conn.Flush()
+ break
+ }
+ recipient_address, _, _ := mailkit.Strip_angle_brackets(param[len("TO:"):])
+ var count int
+ err := session.db.QueryRow(ctx, "SELECT COUNT (*) FROM addresses WHERE address = $1", recipient_address).Scan(&count)
+ if err != nil {
+ _, _ = session.buf_conn.WriteString("451 Internal error: " + err.Error() + "\r\n")
+ _ = session.buf_conn.Flush()
+ break
+ }
+ if count == 0 {
+ _, _ = session.buf_conn.WriteString("550 5.1.1 Recipient address rejected: Local recipients not found: " + recipient_address + "\r\n")
+ _ = session.buf_conn.Flush()
+ break
+ }
+ session.current_rcpt_to = append(session.current_rcpt_to, recipient_address)
+ session.server_state = server_state_rcpt
+ _, _ = session.buf_conn.WriteString("250 2.1.5 Ok\r\n")
+ _ = session.buf_conn.Flush()
+ case "DATA":
+ if session.server_state != server_state_rcpt {
+ _, _ = session.buf_conn.WriteString("503 5.5.1 Error: need RCPT command\r\n")
+ _ = session.buf_conn.Flush()
+ break
+ }
+ _, _ = session.buf_conn.WriteString("354 End data with <CR><LF>.<CR><LF>\r\n")
+ _ = session.buf_conn.Flush()
+ var current_data []byte
+ for {
+ tmp, err := session.buf_conn.ReadSlice('\r')
+ if err != nil {
+ return err
+ }
+
+ // session.buf_conn.ReadSlice returns an internal buffer that gets
+ // overwritten on the next reader operation. So we must
+ // make a copy; also we have to allocate data_part to
+ // the correct length because [[builtin.copy]] copies
+ // min(len(dst), len(src)) items.
+ data_part := make([]byte, len(tmp))
+ copy(data_part, tmp)
+
+ next_four, err := session.buf_conn.Peek(4)
+ if err != nil {
+ return err
+ }
+ if bytes.Equal(next_four, []byte{'\n', '.', '\r', '\n'}) {
+ current_data = slices.Concat(current_data, data_part[:len(data_part)-1])
+ break
+ }
+ current_data = slices.Concat(current_data, data_part)
+ }
+ _, err := session.buf_conn.Discard(4)
+ if err != nil {
+ return err
+ }
+ err = deliver_local(ctx, session.db, session.current_mail_from, session.current_rcpt_to, current_data, session.current_rcpt_to)
+ var err_local_recipients_not_found *err_local_recipients_not_found_t
+ switch {
+ case errors.As(err, &err_local_recipients_not_found):
+ _, _ = session.buf_conn.WriteString("550 5.1.1 Recipient address rejected: " + err_local_recipients_not_found.Error() + "\r\n")
+ case err != nil:
+ _, _ = session.buf_conn.WriteString("500 2.0.0 Error: " + err.Error() + "\r\n")
+ default:
+ _, _ = session.buf_conn.WriteString("250 2.0.0 Ok: Accepted\r\n")
+ }
+ _ = session.buf_conn.Flush()
+ session.server_state = server_state_helo
+ case "QUIT":
+ _, _ = session.buf_conn.WriteString("221 2.0.0 Bye\r\n")
+ _ = session.buf_conn.Flush()
+ if session.tls_conn != nil {
+ session.tls_conn.Close()
+ }
+ session.net_conn.Close()
+ return nil
+ case "NOOP":
+ _, _ = session.buf_conn.WriteString("250 2.0.0 Ok\r\n")
+ _ = session.buf_conn.Flush()
+ case "RSET":
+ if session.server_state != server_state_begin {
+ session.server_state = server_state_helo
+ }
+ _, _ = session.buf_conn.WriteString("250 2.0.0 Ok\r\n")
+ _ = session.buf_conn.Flush()
+ default:
+ _, _ = session.buf_conn.WriteString("500 5.5.2 Error: command not recognized\r\n")
+ _ = session.buf_conn.Flush()
+ }
+ }
+}
+
+func handle_mx_recv_conn(ctx context.Context, net_conn net.Conn) error {
+ session := mx_recv_session{
+ net_conn: net_conn,
+ }
+ return session.handle(ctx)
+}
+
+func serve_mx() {
+ listener, err := net.Listen(config.MX.Net, config.MX.Addr)
+ if err != nil {
+ clog.Fatal(1, "MX: Cannot listen: "+err.Error())
+ }
+ defer listener.Close()
+ clog.Info("MX: Listening via " + config.MX.Net + " on " + config.MX.Addr)
+
+ for {
+ conn, err := listener.Accept()
+ if err != nil {
+ clog.Error("MX: Cannot accept connection: " + err.Error())
+ }
+ clog.Info("MX: Accepted connection from " + conn.RemoteAddr().String())
+
+ go func() {
+ ctx, cancel := context.WithCancel(context.Background())
+ defer cancel()
+ err := handle_mx_recv_conn(ctx, conn)
+ if err != nil {
+ if err == err_connection_handler_eof {
+ clog.Info("MX: Connection for " + conn.RemoteAddr().String() + " closed with EOF")
+ } else {
+ clog.Error("MX: Connection handler for " + conn.RemoteAddr().String() + " returned error: " + err.Error())
+ }
+ } else {
+ clog.Info("MX: Connection for " + conn.RemoteAddr().String() + " closed gracefully")
+ }
+ }()
+ }
+}
generated by cgit v1.2.3 (git 2.25.1) at 2025-01-18 18:22:57 +0000