-
-
Notifications
You must be signed in to change notification settings - Fork 0
/
server.go
252 lines (225 loc) · 7.78 KB
/
server.go
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
package sftp
import (
"context"
"crypto/rand"
"crypto/x509"
"encoding/pem"
"io"
"net"
"os"
"path"
"regexp"
"strconv"
"strings"
"emperror.dev/errors"
"github.com/apex/log"
"github.com/pkg/sftp"
"golang.org/x/crypto/ed25519"
"golang.org/x/crypto/ssh"
"github.com/blademindeu/wings/config"
"github.com/blademindeu/wings/remote"
"github.com/blademindeu/wings/server"
)
// Usernames all follow the same format, so don't even bother hitting the API if the username is not
// at least in the expected format. This is very basic protection against random bots finding the SFTP
// server and sending a flood of usernames.
var validUsernameRegexp = regexp.MustCompile(`^(?i)(.+)\.([a-z0-9]{8})$`)
//goland:noinspection GoNameStartsWithPackageName
type SFTPServer struct {
manager *server.Manager
BasePath string
ReadOnly bool
Listen string
}
func New(m *server.Manager) *SFTPServer {
cfg := config.Get().System
return &SFTPServer{
manager: m,
BasePath: cfg.Data,
ReadOnly: cfg.Sftp.ReadOnly,
Listen: cfg.Sftp.Address + ":" + strconv.Itoa(cfg.Sftp.Port),
}
}
// Run starts the SFTP server and add a persistent listener to handle inbound
// SFTP connections. This will automatically generate an ED25519 key if one does
// not already exist on the system for host key verification purposes.
func (c *SFTPServer) Run() error {
if _, err := os.Stat(c.PrivateKeyPath()); os.IsNotExist(err) {
if err := c.generateED25519PrivateKey(); err != nil {
return err
}
} else if err != nil {
return errors.Wrap(err, "sftp: could not stat private key file")
}
pb, err := os.ReadFile(c.PrivateKeyPath())
if err != nil {
return errors.Wrap(err, "sftp: could not read private key file")
}
private, err := ssh.ParsePrivateKey(pb)
if err != nil {
return err
}
conf := &ssh.ServerConfig{
Config: ssh.Config{
KeyExchanges: []string{
"curve25519-sha256", "curve25519-sha256@libssh.org",
"ecdh-sha2-nistp256", "ecdh-sha2-nistp384", "ecdh-sha2-nistp521",
"diffie-hellman-group14-sha256",
},
Ciphers: []string{
"aes128-gcm@openssh.com",
"chacha20-poly1305@openssh.com",
"aes128-ctr", "aes192-ctr", "aes256-ctr",
},
MACs: []string{
"hmac-sha2-256-etm@openssh.com", "hmac-sha2-256",
},
},
NoClientAuth: false,
MaxAuthTries: 6,
PasswordCallback: func(conn ssh.ConnMetadata, password []byte) (*ssh.Permissions, error) {
return c.makeCredentialsRequest(conn, remote.SftpAuthPassword, string(password))
},
PublicKeyCallback: func(conn ssh.ConnMetadata, key ssh.PublicKey) (*ssh.Permissions, error) {
return c.makeCredentialsRequest(conn, remote.SftpAuthPublicKey, string(ssh.MarshalAuthorizedKey(key)))
},
}
conf.AddHostKey(private)
listener, err := net.Listen("tcp", c.Listen)
if err != nil {
return err
}
public := string(ssh.MarshalAuthorizedKey(private.PublicKey()))
log.WithField("listen", c.Listen).WithField("public_key", strings.Trim(public, "\n")).Info("sftp server listening for connections")
for {
if conn, _ := listener.Accept(); conn != nil {
go func(conn net.Conn) {
defer conn.Close()
if err := c.AcceptInbound(conn, conf); err != nil {
log.WithField("error", err).Error("sftp: failed to accept inbound connection")
}
}(conn)
}
}
}
// AcceptInbound handles an inbound connection to the instance and determines if we should
// serve the request or not.
func (c *SFTPServer) AcceptInbound(conn net.Conn, config *ssh.ServerConfig) error {
// Before beginning a handshake must be performed on the incoming net.Conn
sconn, chans, reqs, err := ssh.NewServerConn(conn, config)
if err != nil {
return errors.WithStack(err)
}
defer sconn.Close()
go ssh.DiscardRequests(reqs)
for ch := range chans {
// If its not a session channel we just move on because its not something we
// know how to handle at this point.
if ch.ChannelType() != "session" {
ch.Reject(ssh.UnknownChannelType, "unknown channel type")
continue
}
channel, requests, err := ch.Accept()
if err != nil {
continue
}
go func(in <-chan *ssh.Request) {
for req := range in {
// Channels have a type that is dependent on the protocol. For SFTP
// this is "subsystem" with a payload that (should) be "sftp". Discard
// anything else we receive ("pty", "shell", etc)
req.Reply(req.Type == "subsystem" && string(req.Payload[4:]) == "sftp", nil)
}
}(requests)
// If no UUID has been set on this inbound request then we can assume we
// have screwed up something in the authentication code. This is a sanity
// check, but should never be encountered (ideally...).
//
// This will also attempt to match a specific server out of the global server
// store and return nil if there is no match.
uuid := sconn.Permissions.Extensions["uuid"]
srv := c.manager.Find(func(s *server.Server) bool {
if uuid == "" {
return false
}
return s.ID() == uuid
})
if srv == nil {
continue
}
// Spin up a SFTP server instance for the authenticated user's server allowing
// them access to the underlying filesystem.
handler, err := NewHandler(sconn, srv)
if err != nil {
return errors.WithStackIf(err)
}
rs := sftp.NewRequestServer(channel, handler.Handlers())
if err := rs.Serve(); err == io.EOF {
_ = rs.Close()
}
}
return nil
}
// Generates a new ED25519 private key that is used for host authentication when
// a user connects to the SFTP server.
func (c *SFTPServer) generateED25519PrivateKey() error {
_, priv, err := ed25519.GenerateKey(rand.Reader)
if err != nil {
return errors.Wrap(err, "sftp: failed to generate ED25519 private key")
}
if err := os.MkdirAll(path.Dir(c.PrivateKeyPath()), 0o755); err != nil {
return errors.Wrap(err, "sftp: could not create internal sftp data directory")
}
o, err := os.OpenFile(c.PrivateKeyPath(), os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0o600)
if err != nil {
return errors.WithStack(err)
}
defer o.Close()
b, err := x509.MarshalPKCS8PrivateKey(priv)
if err != nil {
return errors.Wrap(err, "sftp: failed to marshal private key into bytes")
}
if err := pem.Encode(o, &pem.Block{Type: "PRIVATE KEY", Bytes: b}); err != nil {
return errors.Wrap(err, "sftp: failed to write ED25519 private key to disk")
}
return nil
}
func (c *SFTPServer) makeCredentialsRequest(conn ssh.ConnMetadata, t remote.SftpAuthRequestType, p string) (*ssh.Permissions, error) {
request := remote.SftpAuthRequest{
Type: t,
User: conn.User(),
Pass: p,
IP: conn.RemoteAddr().String(),
SessionID: conn.SessionID(),
ClientVersion: conn.ClientVersion(),
}
logger := log.WithFields(log.Fields{"subsystem": "sftp", "method": request.Type, "username": request.User, "ip": request.IP})
logger.Debug("validating credentials for SFTP connection")
if !validUsernameRegexp.MatchString(request.User) {
logger.Warn("failed to validate user credentials (invalid format)")
return nil, &remote.SftpInvalidCredentialsError{}
}
resp, err := c.manager.Client().ValidateSftpCredentials(context.Background(), request)
if err != nil {
if _, ok := err.(*remote.SftpInvalidCredentialsError); ok {
logger.Warn("failed to validate user credentials (invalid username or password)")
} else {
logger.WithField("error", err).Error("encountered an error while trying to validate user credentials")
}
return nil, err
}
logger.WithField("server", resp.Server).Debug("credentials validated and matched to server instance")
permissions := ssh.Permissions{
Extensions: map[string]string{
"ip": conn.RemoteAddr().String(),
"uuid": resp.Server,
"user": resp.User,
"permissions": strings.Join(resp.Permissions, ","),
},
}
return &permissions, nil
}
// PrivateKeyPath returns the path the host private key for this server instance.
func (c *SFTPServer) PrivateKeyPath() string {
return path.Join(c.BasePath, ".sftp/id_ed25519")
}