alps/session.go

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package alps
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import (
"crypto/rand"
"encoding/base64"
"errors"
"fmt"
"mime/multipart"
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"net/http"
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"os"
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"sync"
"time"
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imapclient "github.com/emersion/go-imap/client"
"github.com/emersion/go-sasl"
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"github.com/emersion/go-smtp"
"github.com/google/uuid"
"github.com/labstack/echo/v4"
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)
// TODO: make this configurable
const sessionDuration = 30 * time.Minute
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func generateToken() (string, error) {
b := make([]byte, 32)
_, err := rand.Read(b)
if err != nil {
return "", err
}
return base64.URLEncoding.EncodeToString(b), nil
}
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var errSessionExpired = errors.New("session expired")
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// AuthError wraps an authentication error.
type AuthError struct {
cause error
}
func (err AuthError) Error() string {
return fmt.Sprintf("authentication failed: %v", err.cause)
}
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// 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 {
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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
}
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// 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)
}
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// 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)
)
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// SessionManager keeps track of active sessions. It connects and re-connects
// to the upstream IMAP server as necessary. It prunes expired sessions.
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type SessionManager struct {
dialIMAP DialIMAPFunc
dialSMTP DialSMTPFunc
logger echo.Logger
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debug bool
locker sync.Mutex
sessions map[string]*Session // protected by locker
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}
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func newSessionManager(dialIMAP DialIMAPFunc, dialSMTP DialSMTPFunc, logger echo.Logger, debug bool) *SessionManager {
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return &SessionManager{
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sessions: make(map[string]*Session),
dialIMAP: dialIMAP,
dialSMTP: dialSMTP,
logger: logger,
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debug: debug,
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}
}
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}
}
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if sm.debug {
c.SetDebug(os.Stderr)
}
return c, nil
}
func (sm *SessionManager) get(token string) (*Session, error) {
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sm.locker.Lock()
defer sm.locker.Unlock()
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session, ok := sm.sessions[token]
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if !ok {
return nil, errSessionExpired
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}
return session, nil
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}
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// 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
}
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sm.locker.Lock()
defer sm.locker.Unlock()
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var token string
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for {
token, err = generateToken()
if err != nil {
c.Logout()
return nil, err
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}
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if _, ok := sm.sessions[token]; !ok {
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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
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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()
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sm.locker.Lock()
delete(sm.sessions, token)
sm.locker.Unlock()
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}()
return s, nil
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}