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
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
|
use std::{
io::{BufRead, BufReader, Write},
net::{IpAddr, SocketAddr, TcpListener, TcpStream},
};
use anyhow::Result;
use tokio::spawn;
const SERVER_NAME: &str = "";
pub struct SmtpServer {
listener: TcpListener,
running: bool,
}
impl SmtpServer {
pub fn new(ip: [u8; 4], port: u16) -> Result<Self> {
Ok(Self {
listener: TcpListener::bind((IpAddr::from(ip), port))?,
running: false,
})
}
// TODO: trap SIGINT to stop server?
pub async fn run(&mut self) -> Result<()> {
self.running = true;
while self.running {
let (stream, addr) = self.listener.accept()?;
let session = SessionHandler {
addr,
state: SessionState::default(),
client_host: String::new(),
from: None,
to: Vec::new(),
};
spawn(session.run(stream));
}
Ok(())
}
}
struct SessionHandler {
addr: SocketAddr,
state: SessionState,
client_host: String,
from: Option<String>,
to: Vec<String>,
}
impl SessionHandler {
async fn run(mut self, stream: TcpStream) -> Result<()> {
let mut writer = stream.try_clone()?;
let mut r = BufReader::new(&stream);
let mut buffer = String::new();
writer.write_all(
Reply::Ready(String::from(SERVER_NAME))
.to_string()
.as_bytes(),
)?;
loop {
if r.read_line(&mut buffer)? == 0 {
break;
}
log::debug!("Received '{}' from '{}'", buffer.trim(), self.addr);
let command = match Command::try_from(buffer.as_str()) {
Err(_) => {
writer.write_all(Reply::InvalidCommand.to_string().as_bytes())?;
continue;
}
Ok(v) => v,
};
let res = self.apply(command).await?;
writer.write_all(res.to_string().as_bytes())?;
buffer.clear();
}
log::info!("Connection closed by {}", self.addr);
Ok(())
}
async fn apply(&mut self, command: Command) -> Result<Reply> {
match &command {
Command::HELO(hostname) => self.helo(hostname).await,
Command::MAIL(from) => self.mail(from).await,
Command::RCPT(to) => self.rcpt(to).await,
}
}
/// HELO resets buffers
async fn helo(&mut self, hostname: &str) -> Result<Reply> {
self.client_host = String::from(hostname);
self.state = SessionState::Normal;
self.from = None;
self.to.clear();
Ok(Reply::Completed(String::from(SERVER_NAME)))
}
/// TODO: Validate email address
/// MAIL resets buffers
async fn mail(&mut self, from: &str) -> Result<Reply> {
if from.is_empty() {
return Ok(Reply::InvalidParameter);
}
self.from = Some(String::from(from));
self.to.clear();
self.state = SessionState::MailTransaction;
Ok(Reply::Completed(String::from("Ok")))
}
/// TODO: Validate email addresses
/// Only after having started a mail transaction
async fn rcpt(&mut self, to: &str) -> Result<Reply> {
if self.state != SessionState::MailTransaction {
return Ok(Reply::BadSequence);
}
if to.is_empty() {
return Ok(Reply::InvalidParameter);
}
self.to.push(String::from(to));
Ok(Reply::Completed(String::from("Ok")))
}
}
#[derive(PartialEq)]
enum SessionState {
WaitingHelo,
MailTransaction,
Normal,
}
impl Default for SessionState {
fn default() -> Self {
Self::WaitingHelo
}
}
enum Reply {
Ready(String),
Completed(String),
InvalidCommand,
InvalidParameter,
BadSequence,
}
impl ToString for Reply {
fn to_string(&self) -> String {
match self {
Reply::Ready(hostname) => format!("220 {}", hostname),
Reply::Completed(hostname) => format!("250 {}", hostname),
Reply::InvalidCommand => format!("500 Command not recognized"),
Reply::InvalidParameter => format!("501 Parameter error"),
Reply::BadSequence => format!("503 Bad sequence of commands"),
}
}
}
enum Command {
HELO(String),
MAIL(String),
RCPT(String),
}
impl TryFrom<&str> for Command {
type Error = anyhow::Error;
fn try_from(value: &str) -> std::result::Result<Self, Self::Error> {
if value.len() >= 5 && value.to_lowercase().starts_with("helo ") {
return Ok(Command::HELO(String::from(&value[5..])));
}
if value.len() >= 11
&& value.to_lowercase().starts_with("mail from:<")
&& value.contains('>')
{
let from = &value[11..value.find('>').unwrap()];
return Ok(Command::MAIL(String::from(from)));
}
if value.len() >= 9 && value.to_lowercase().starts_with("rcpt to:<") && value.contains('>')
{
let to = &value[9..value.find('>').unwrap()];
return Ok(Command::RCPT(String::from(to)));
}
Err(anyhow::format_err!("Invalid command"))
}
}
|
