1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
|
package main
import (
"bufio"
"bytes"
"slices"
"strings"
)
type server_state_t uint
const (
server_state_begin server_state_t = iota
server_state_helo
server_state_mail
server_state_rcpt
)
func handle_incoming_server_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)
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])
break
}
current_data = slices.Concat(current_data, data_part)
}
_, err := reader.Discard(4)
if err != nil {
return err
}
err = deliver_incoming(current_mail_from, current_rcpt_to, current_data)
if err == nil {
_, _ = writer.WriteString("250 2.0.0 Ok: Accepted\r\n")
} else {
_, _ = writer.WriteString("500 2.0.0 Funderscore\r\n")
}
_ = writer.Flush()
server_state = server_state_helo
case "QUIT":
_, _ = writer.WriteString("221 2.0.0 Bye\r\n")
_ = writer.Flush()
return nil
case "NOOP":
_, _ = writer.WriteString("250 2.0.0 Ok\r\n")
_ = writer.Flush()
case "RSET":
if server_state != server_state_begin {
server_state = server_state_helo
}
_, _ = writer.WriteString("250 2.0.0 Ok\r\n")
_ = writer.Flush()
default:
_, _ = writer.WriteString("500 5.5.2 Error: command not recognized\r\n")
_ = writer.Flush()
}
}
}
|
