aboutsummaryrefslogtreecommitdiff
path: root/session.go
blob: 8e69565469126539da26c448e6f7d23443e3c342 (plain) (blame)
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
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
package alps

import (
	"crypto/rand"
	"encoding/base64"
	"errors"
	"fmt"
	"mime/multipart"
	"net/http"
	"os"
	"sync"
	"time"

	imapclient "github.com/emersion/go-imap/client"
	"github.com/emersion/go-sasl"
	"github.com/emersion/go-smtp"
	"github.com/google/uuid"
	"github.com/labstack/echo/v4"
)

// TODO: make this configurable
const sessionDuration = 30 * time.Minute

func generateToken() (string, error) {
	b := make([]byte, 32)
	_, err := rand.Read(b)
	if err != nil {
		return "", err
	}
	return base64.URLEncoding.EncodeToString(b), nil
}

var errSessionExpired = errors.New("session expired")

// AuthError wraps an authentication error.
type AuthError struct {
	cause error
}

func (err AuthError) Error() string {
	return fmt.Sprintf("authentication failed: %v", err.cause)
}

// Session is an active user session. It may also hold an IMAP connection.
//
// The session's password is not available to plugins. Plugins should use the
// session helpers to authenticate outgoing connections, for instance DoSMTP.
type Session struct {
	manager            *SessionManager
	username, password string
	token              string
	closed             chan struct{}
	pings              chan struct{}
	timer              *time.Timer
	store              Store

	imapLocker sync.Mutex
	imapConn   *imapclient.Client // protected by locker, can be nil

	attachmentsLocker sync.Mutex
	attachments       map[string]*Attachment // protected by attachmentsLocker
}

type Attachment struct {
	File *multipart.FileHeader
	Form *multipart.Form
}

func (s *Session) ping() {
	s.pings <- struct{}{}
}

// Username returns the session's username.
func (s *Session) Username() string {
	return s.username
}

// DoIMAP executes an IMAP operation on this session. The IMAP client can only
// be used from inside f.
func (s *Session) DoIMAP(f func(*imapclient.Client) error) error {
	s.imapLocker.Lock()
	defer s.imapLocker.Unlock()

	if s.imapConn == nil {
		var err error
		s.imapConn, err = s.manager.connectIMAP(s.username, s.password)
		if err != nil {
			s.Close()
			return fmt.Errorf("failed to re-connect to IMAP server: %v", err)
		}
	}

	return f(s.imapConn)
}

// DoSMTP executes an SMTP operation on this session. The SMTP client can only
// be used from inside f.
func (s *Session) DoSMTP(f func(*smtp.Client) error) error {
	c, err := s.manager.dialSMTP()
	if err != nil {
		return err
	}
	defer c.Close()

	auth := sasl.NewPlainClient("", s.username, s.password)
	if err := c.Auth(auth); err != nil {
		return AuthError{err}
	}

	if err := f(c); err != nil {
		return err
	}

	if err := c.Quit(); err != nil {
		return fmt.Errorf("QUIT failed: %v", err)
	}

	return nil
}

// SetHTTPBasicAuth adds an Authorization header field to the request with
// this session's credentials.
func (s *Session) SetHTTPBasicAuth(req *http.Request) {
	// TODO: find a way to make it harder for plugins to steal credentials
	req.SetBasicAuth(s.username, s.password)
}

// Close destroys the session. This can be used to log the user out.
func (s *Session) Close() {
	s.attachmentsLocker.Lock()
	defer s.attachmentsLocker.Unlock()

	for _, f := range s.attachments {
		f.Form.RemoveAll()
	}

	select {
	case <-s.closed:
		// This space is intentionally left blank
	default:
		close(s.closed)
	}
}

// Puts an attachment and returns a generated UUID
func (s *Session) PutAttachment(in *multipart.FileHeader,
	form *multipart.Form) (string, error) {
	// TODO: Prevent users from uploading too many attachments, or too large
	//
	// Probably just set a cap on the maximum combined size of all files in the
	// user's session
	//
	// TODO: Figure out what to do if the user abandons the compose window
	// after adding some attachments
	id := uuid.New()
	s.attachmentsLocker.Lock()
	s.attachments[id.String()] = &Attachment{
		File:     in,
		Form:     form,
	}
	s.attachmentsLocker.Unlock()
	return id.String(), nil
}

// Removes an attachment from the session. Returns nil if there was no such
// attachment.
func (s *Session) PopAttachment(uuid string) *Attachment {
	s.attachmentsLocker.Lock()
	defer s.attachmentsLocker.Unlock()

	a, ok := s.attachments[uuid]
	if !ok {
		return nil
	}
	delete(s.attachments, uuid)

	return a
}

// Store returns a store suitable for storing persistent user data.
func (s *Session) Store() Store {
	return s.store
}

type (
	// DialIMAPFunc connects to the upstream IMAP server.
	DialIMAPFunc func() (*imapclient.Client, error)
	// DialSMTPFunc connects to the upstream SMTP server.
	DialSMTPFunc func() (*smtp.Client, error)
)

// SessionManager keeps track of active sessions. It connects and re-connects
// to the upstream IMAP server as necessary. It prunes expired sessions.
type SessionManager struct {
	dialIMAP DialIMAPFunc
	dialSMTP DialSMTPFunc
	logger   echo.Logger
	debug    bool

	locker   sync.Mutex
	sessions map[string]*Session // protected by locker
}

func newSessionManager(dialIMAP DialIMAPFunc, dialSMTP DialSMTPFunc, logger echo.Logger, debug bool) *SessionManager {
	return &SessionManager{
		sessions: make(map[string]*Session),
		dialIMAP: dialIMAP,
		dialSMTP: dialSMTP,
		logger:   logger,
		debug:    debug,
	}
}

func (sm *SessionManager) Close() {
	for _, s := range sm.sessions {
		s.Close()
	}
}

func (sm *SessionManager) connectIMAP(username, password string) (*imapclient.Client, error) {
	c, err := sm.dialIMAP()
	if err != nil {
		return nil, err
	}

	if err := c.Login(username, password); err != nil {
		c.Logout()
		return nil, AuthError{err}
	}

	if sm.debug {
		c.SetDebug(os.Stderr)
	}

	return c, nil
}

func (sm *SessionManager) get(token string) (*Session, error) {
	sm.locker.Lock()
	defer sm.locker.Unlock()

	session, ok := sm.sessions[token]
	if !ok {
		return nil, errSessionExpired
	}
	return session, nil
}

// Put connects to the IMAP server and creates a new session. If authentication
// fails, the error will be of type AuthError.
func (sm *SessionManager) Put(username, password string) (*Session, error) {
	c, err := sm.connectIMAP(username, password)
	if err != nil {
		return nil, err
	}

	sm.locker.Lock()
	defer sm.locker.Unlock()

	var token string
	for {
		token, err = generateToken()
		if err != nil {
			c.Logout()
			return nil, err
		}

		if _, ok := sm.sessions[token]; !ok {
			break
		}
	}

	s := &Session{
		manager:     sm,
		closed:      make(chan struct{}),
		pings:       make(chan struct{}, 5),
		imapConn:    c,
		username:    username,
		password:    password,
		token:       token,
		attachments: make(map[string]*Attachment),
	}

	s.store, err = newStore(s, sm.logger)
	if err != nil {
		return nil, err
	}

	sm.sessions[token] = s

	go func() {
		timer := time.NewTimer(sessionDuration)

		alive := true
		for alive {
			var loggedOut <-chan struct{}
			s.imapLocker.Lock()
			if s.imapConn != nil {
				loggedOut = s.imapConn.LoggedOut()
			}
			s.imapLocker.Unlock()

			select {
			case <-loggedOut:
				s.imapLocker.Lock()
				s.imapConn = nil
				s.imapLocker.Unlock()
			case <-s.pings:
				if !timer.Stop() {
					<-timer.C
				}
				timer.Reset(sessionDuration)
			case <-timer.C:
				alive = false
			case <-s.closed:
				alive = false
			}
		}

		timer.Stop()

		s.imapLocker.Lock()
		if s.imapConn != nil {
			s.imapConn.Logout()
		}
		s.imapLocker.Unlock()

		sm.locker.Lock()
		delete(sm.sessions, token)
		sm.locker.Unlock()
	}()

	return s, nil
}