1package ssh
2
3import (
4 "context"
5 "fmt"
6 "net"
7 "os"
8 "strconv"
9 "time"
10
11 "github.com/charmbracelet/keygen"
12 "github.com/charmbracelet/log"
13 "github.com/charmbracelet/soft-serve/pkg/backend"
14 "github.com/charmbracelet/soft-serve/pkg/config"
15 "github.com/charmbracelet/soft-serve/pkg/db"
16 "github.com/charmbracelet/soft-serve/pkg/proto"
17 "github.com/charmbracelet/soft-serve/pkg/store"
18 "github.com/charmbracelet/soft-serve/pkg/ui/common"
19 "github.com/charmbracelet/ssh"
20 "github.com/charmbracelet/wish"
21 bm "github.com/charmbracelet/wish/bubbletea"
22 rm "github.com/charmbracelet/wish/recover"
23 "github.com/prometheus/client_golang/prometheus"
24 "github.com/prometheus/client_golang/prometheus/promauto"
25 gossh "golang.org/x/crypto/ssh"
26)
27
28var (
29 publicKeyCounter = promauto.NewCounterVec(prometheus.CounterOpts{
30 Namespace: "soft_serve",
31 Subsystem: "ssh",
32 Name: "public_key_auth_total",
33 Help: "The total number of public key auth requests",
34 }, []string{"allowed"})
35
36 keyboardInteractiveCounter = promauto.NewCounterVec(prometheus.CounterOpts{
37 Namespace: "soft_serve",
38 Subsystem: "ssh",
39 Name: "keyboard_interactive_auth_total",
40 Help: "The total number of keyboard interactive auth requests",
41 }, []string{"allowed"})
42)
43
44// SSHServer is a SSH server that implements the git protocol.
45type SSHServer struct { // nolint: revive
46 srv *ssh.Server
47 cfg *config.Config
48 be *backend.Backend
49 ctx context.Context
50 logger *log.Logger
51}
52
53// NewSSHServer returns a new SSHServer.
54func NewSSHServer(ctx context.Context) (*SSHServer, error) {
55 cfg := config.FromContext(ctx)
56 logger := log.FromContext(ctx).WithPrefix("ssh")
57 dbx := db.FromContext(ctx)
58 datastore := store.FromContext(ctx)
59 be := backend.FromContext(ctx)
60
61 var err error
62 s := &SSHServer{
63 cfg: cfg,
64 ctx: ctx,
65 be: be,
66 logger: logger,
67 }
68
69 mw := []wish.Middleware{
70 rm.MiddlewareWithLogger(
71 logger,
72 // BubbleTea middleware.
73 bm.MiddlewareWithProgramHandler(SessionHandler, common.DefaultColorProfile),
74 // CLI middleware.
75 CommandMiddleware,
76 // Logging middleware.
77 LoggingMiddleware,
78 // Context middleware.
79 ContextMiddleware(cfg, dbx, datastore, be, logger),
80 // Authentication middleware.
81 // gossh.PublicKeyHandler doesn't guarantee that the public key
82 // is in fact the one used for authentication, so we need to
83 // check it again here.
84 AuthenticationMiddleware,
85 ),
86 }
87
88 s.srv, err = wish.NewServer(
89 ssh.PublicKeyAuth(s.PublicKeyHandler),
90 ssh.KeyboardInteractiveAuth(s.KeyboardInteractiveHandler),
91 ssh.AllocatePty(),
92 wish.WithAddress(cfg.SSH.ListenAddr),
93 wish.WithHostKeyPath(cfg.SSH.KeyPath),
94 wish.WithMiddleware(mw...),
95 )
96 if err != nil {
97 return nil, err
98 }
99
100 if config.IsDebug() {
101 s.srv.ServerConfigCallback = func(ctx ssh.Context) *gossh.ServerConfig {
102 return &gossh.ServerConfig{
103 AuthLogCallback: func(conn gossh.ConnMetadata, method string, err error) {
104 logger.Debug("authentication", "user", conn.User(), "method", method, "err", err)
105 },
106 }
107 }
108 }
109
110 if cfg.SSH.MaxTimeout > 0 {
111 s.srv.MaxTimeout = time.Duration(cfg.SSH.MaxTimeout) * time.Second
112 }
113
114 if cfg.SSH.IdleTimeout > 0 {
115 s.srv.IdleTimeout = time.Duration(cfg.SSH.IdleTimeout) * time.Second
116 }
117
118 // Create client ssh key
119 if _, err := os.Stat(cfg.SSH.ClientKeyPath); err != nil && os.IsNotExist(err) {
120 _, err := keygen.New(cfg.SSH.ClientKeyPath, keygen.WithKeyType(keygen.Ed25519), keygen.WithWrite())
121 if err != nil {
122 return nil, fmt.Errorf("client ssh key: %w", err)
123 }
124 }
125
126 return s, nil
127}
128
129// ListenAndServe starts the SSH server.
130func (s *SSHServer) ListenAndServe() error {
131 return s.srv.ListenAndServe()
132}
133
134// Serve starts the SSH server on the given net.Listener.
135func (s *SSHServer) Serve(l net.Listener) error {
136 return s.srv.Serve(l)
137}
138
139// Close closes the SSH server.
140func (s *SSHServer) Close() error {
141 return s.srv.Close()
142}
143
144// Shutdown gracefully shuts down the SSH server.
145func (s *SSHServer) Shutdown(ctx context.Context) error {
146 return s.srv.Shutdown(ctx)
147}
148
149func initializePermissions(ctx ssh.Context) {
150 perms := ctx.Permissions()
151 if perms == nil || perms.Permissions == nil {
152 perms = &ssh.Permissions{Permissions: &gossh.Permissions{}}
153 }
154 if perms.Extensions == nil {
155 perms.Extensions = make(map[string]string)
156 }
157 if perms.Permissions.Extensions == nil {
158 perms.Permissions.Extensions = make(map[string]string)
159 }
160}
161
162// PublicKeyAuthHandler handles public key authentication.
163func (s *SSHServer) PublicKeyHandler(ctx ssh.Context, pk ssh.PublicKey) (allowed bool) {
164 if pk == nil {
165 return false
166 }
167
168 defer func(allowed *bool) {
169 publicKeyCounter.WithLabelValues(strconv.FormatBool(*allowed)).Inc()
170 }(&allowed)
171
172 user, _ := s.be.UserByPublicKey(ctx, pk)
173 if user != nil {
174 ctx.SetValue(proto.ContextKeyUser, user)
175 allowed = true
176
177 // XXX: store the first "approved" public-key fingerprint in the
178 // permissions block to use for authentication later.
179 initializePermissions(ctx)
180 perms := ctx.Permissions()
181
182 // Set the public key fingerprint to be used for authentication.
183 perms.Extensions["pubkey-fp"] = gossh.FingerprintSHA256(pk)
184 ctx.SetValue(ssh.ContextKeyPermissions, perms)
185 }
186
187 return
188}
189
190// KeyboardInteractiveHandler handles keyboard interactive authentication.
191// This is used after all public key authentication has failed.
192func (s *SSHServer) KeyboardInteractiveHandler(ctx ssh.Context, _ gossh.KeyboardInteractiveChallenge) bool {
193 ac := s.be.AllowKeyless(ctx)
194 keyboardInteractiveCounter.WithLabelValues(strconv.FormatBool(ac)).Inc()
195
196 // If we're allowing keyless access, reset the public key fingerprint
197 if ac {
198 initializePermissions(ctx)
199 perms := ctx.Permissions()
200
201 // XXX: reset the public-key fingerprint. This is used to validate the
202 // public key being used to authenticate.
203 perms.Extensions["pubkey-fp"] = ""
204 ctx.SetValue(ssh.ContextKeyPermissions, perms)
205 }
206 return ac
207}