diff options
Diffstat (limited to 'main.go')
| -rw-r--r-- | main.go | 196 |
1 files changed, 196 insertions, 0 deletions
@@ -0,0 +1,196 @@ +package main + +// TODO: panic bleh!!!!!!!!!!!!!!!!!! + +import ( + "bufio" + "bytes" + "net" + "os" + "slices" + "strings" + + "go.lindenii.runxiyu.org/lindenii-common/clog" + "go.lindenii.runxiyu.org/lindenii-common/scfg" +) + +const VERSION = "lindenii-maild v0.0.0" + +func main() { + config_file, err := os.Open("maild.scfg") + if err != nil { + panic(err) + } + + err = scfg.NewDecoder(bufio.NewReader(config_file)).Decode(&config) + if err != nil { + panic(err) + } + + listener, err := net.Listen("tcp", ":25") + if err != nil { + panic(err) + } + defer listener.Close() + + for { + conn, err := listener.Accept() + if err != nil { + panic(err) + } + + go func() { + err := handle_connection(bufio.NewReader(conn), bufio.NewWriter(conn)) + if err != nil { + clog.Error("connection handler returned error", "err", err) + } + }() + } + +} + +type server_state_t uint + +const ( + server_state_begin server_state_t = iota + server_state_helo + server_state_mail + server_state_rcpt +) + +func handle_connection(reader *bufio.Reader, writer *bufio.Writer) error { + _, _ = writer.WriteString("220 " + config.Server_name + " " + VERSION + "\r\n") + _ = writer.Flush() + server_state := server_state_begin + var remote_server_name string + var current_mail_from string + var current_rcpt_to []string + for { + line, err := reader.ReadString('\n') + if err != nil { + 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 "HELO": + if param == "" { // TODO: actually validate the hostname + _, _ = writer.WriteString("501 Syntax: HELO hostname\r\n") + _ = writer.Flush() + break + } + remote_server_name = param + _ = remote_server_name // TODO + server_state = server_state_helo + _, _ = writer.WriteString("250 " + config.Server_name + "\r\n") + _ = writer.Flush() + case "MAIL": + switch server_state { + case server_state_begin: + _, _ = writer.WriteString("503 5.5.1 Error: send HELO/EHLO first\r\n") + _ = writer.Flush() + break switch_cmd + case server_state_helo: + break + case server_state_mail: + _, _ = writer.WriteString("503 5.5.1 Error: nested MAIL command\r\n") + _ = writer.Flush() + break switch_cmd + } + if len(param) <= len("FROM:") || strings.ToUpper(param[:len("FROM:")]) != "FROM:" { + _, _ = writer.WriteString("501 5.5.4 Syntax: MAIL FROM:<address>\r\n") + _ = writer.Flush() + break + } + current_mail_from = param[len("FROM:"):] + current_rcpt_to = []string{} + server_state = server_state_mail + _, _ = writer.WriteString("250 2.1.0 Ok\r\n") + _ = writer.Flush() + // TODO: Address validation + case "RCPT": + if server_state != server_state_mail && server_state != server_state_rcpt { + _, _ = writer.WriteString("503 5.5.1 Error: need MAIL command\r\n") + _ = writer.Flush() + break + } + if len(param) <= len("TO:") || strings.ToUpper(param[:len("TO:")]) != "TO:" { + _, _ = writer.WriteString("501 5.5.4 Syntax: RCPT TO:<address>\r\n") + _ = writer.Flush() + break + } + current_rcpt_to = append(current_rcpt_to, param[len("TO:"):]) + server_state = server_state_rcpt + _, _ = writer.WriteString("250 2.1.5 Ok\r\n") + _ = writer.Flush() + case "DATA": + if server_state != server_state_rcpt { + _, _ = writer.WriteString("503 5.5.1 Error: need RCPT command\r\n") + _ = writer.Flush() + break + } + _, _ = writer.WriteString("354 End data with <CR><LF>.<CR><LF>\r\n") + _ = writer.Flush() + var current_data []byte + for { + tmp, err := reader.ReadSlice('\r') + if err != nil { + return err + } + + // reader.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) + + clog.Debug("e", "e", string(data_part)) + next_four, err := reader.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]) + clog.Debug("eee", string(next_four)) // shut up go + break + } + clog.Debug("pre concat", "current_data", string(current_data), "data_part", string(data_part)) + current_data = slices.Concat(current_data, data_part) + clog.Debug("post concat", "current_data", string(current_data), "data_part", string(data_part)) + } + _, err := reader.Discard(4) + if err != nil { + return err + } + deliver_incoming(current_mail_from, current_rcpt_to, current_data) + server_state = server_state_helo + _, _ = writer.WriteString("250 2.0.0 Ok: Accepted\r\n") + _ = writer.Flush() + default: + _, _ = writer.WriteString("500 5.5.2 Error: command not recognized\r\n") + _ = writer.Flush() + } + } +} + +func deliver_incoming(envelope_from string, envelope_recipients []string, data []byte) { + clog.Debug( + "incoming_mail", + "envelope_from", envelope_from, + "envelope_recipients", envelope_recipients, + "data", string(data), + ) +} |