authserver.go 13.4 KB
Newer Older
ale's avatar
ale committed
1
2
3
4
package server

import (
	"context"
5
	"errors"
ale's avatar
ale committed
6
7
8
9
10
11
12
13
14
15
16
	"fmt"
	"io/ioutil"
	"log"
	"path/filepath"
	"strings"

	scrypt "github.com/elithrar/simple-scrypt"
	"github.com/pquerna/otp/totp"
	"github.com/tstranex/u2f"
	"gopkg.in/yaml.v2"

17
18
	usermetadbclient "git.autistici.org/id/usermetadb/client"

ale's avatar
ale committed
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
	"git.autistici.org/id/auth"
)

// User contains the attributes of a user account as relevant to the
// authentication server. It is only used internally, to communicate
// between the authserver and its storage backends.
type User struct {
	Name                 string
	Email                string
	EncryptedPassword    []byte
	TOTPSecret           string
	U2FRegistrations     []u2f.Registration
	AppSpecificPasswords []*AppSpecificPassword
	Groups               []string
}

// AppSpecificPassword is a password tied to a single service.
type AppSpecificPassword struct {
	Service           string
	EncryptedPassword []byte
}

// Has2FA returns true if the user supports any 2FA method.
func (u *User) Has2FA() bool {
	return u.HasU2F() || u.HasOTP()
}

// HasOTP returns true if the user supports (T)OTP.
func (u *User) HasOTP() bool {
	return u.TOTPSecret != ""
}

// HasU2F returns true if the user supports U2F.
func (u *User) HasU2F() bool {
	return len(u.U2FRegistrations) > 0
}

// UserInfo returns extra user information in the format required by
// the auth wire protocol.
func (u *User) UserInfo() *auth.UserInfo {
	return &auth.UserInfo{
		Email:  u.Email,
		Groups: u.Groups,
	}
}

// UserBackend provides us with per-service user information.
type UserBackend interface {
	Close()
	GetUser(context.Context, *BackendSpec, string) (*User, bool)
}

// U2FShortTermStorage stores short-term u2f challenges.
type U2FShortTermStorage interface {
	SetUserChallenge(string, *u2f.Challenge) error
	GetUserChallenge(string) (*u2f.Challenge, bool)
}

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
type ratelimitKeyFunc func(*User, *auth.Request) string

func usernameKey(user *User, _ *auth.Request) string {
	return user.Name
}

func ipAddrKey(_ *User, req *auth.Request) string {
	if req.DeviceInfo != nil {
		return req.DeviceInfo.RemoteAddr
	}
	return ""
}

type authRatelimiterConfig struct {
	Limit         int      `yaml:"limit"`
	Period        int      `yaml:"period"`
	BlacklistTime int      `yaml:"blacklist_for"`
	OnFailure     bool     `yaml:"on_failure"`
	Keys          []string `yaml:"keys"`

	keyFuncs []ratelimitKeyFunc
}

func (r *authRatelimiterConfig) compile() error {
	for _, k := range r.Keys {
		var f ratelimitKeyFunc
		switch k {
		case "ip":
			f = ipAddrKey
		case "user":
			f = usernameKey
		default:
			return fmt.Errorf("unknown key %s", k)
		}
		r.keyFuncs = append(r.keyFuncs, f)
	}
	return nil
}

const rlKeySep = ";"

func (r *authRatelimiterConfig) key(user *User, req *auth.Request) string {
	if len(r.keyFuncs) == 1 {
		return r.keyFuncs[0](user, req)
	}

	var parts []string
	for _, f := range r.keyFuncs {
		parts = append(parts, f(user, req))
	}
	return strings.Join(parts, rlKeySep)
}

type authRatelimiter struct {
	*authRatelimiterConfig
	rl *Ratelimiter
}

func (r *authRatelimiter) AllowIncr(user *User, req *auth.Request) bool {
	return r.rl.AllowIncr(r.key(user, req))
}

type authBlacklist struct {
	*authRatelimiterConfig
	bl *Blacklist
}

func (b *authBlacklist) Allow(user *User, req *auth.Request) bool {
	return b.bl.Allow(b.key(user, req))
}

func (b *authBlacklist) Incr(user *User, req *auth.Request, resp *auth.Response) {
	if b.OnFailure && resp.Status == auth.StatusOK {
		return
	}
	b.bl.Incr(b.key(user, req))
}

155
156
157
type requestFilter interface {
	Filter(*User, *auth.Request, *auth.Response) *auth.Response
}
158

ale's avatar
ale committed
159
160
161
162
163
164
// BackendSpec specifies backend-specific configuration for a service.
type BackendSpec struct {
	LDAPSpec *LDAPServiceConfig `yaml:"ldap"`
	FileSpec string             `yaml:"file"`
}

165
// ServiceConfig defines the authentication backends for a service.
ale's avatar
ale committed
166
type ServiceConfig struct {
167
168
169
170
	BackendSpecs         []*BackendSpec `yaml:"backends"`
	ChallengeResponse    bool           `yaml:"challenge_response"`
	Enforce2FA           bool           `yaml:"enforce_2fa"`
	EnableDeviceTracking bool           `yaml:"enable_device_tracking"`
171
172
173
174
175

	Ratelimits []string `yaml:"rate_limits"`

	rl      []*authRatelimiter
	bl      []*authBlacklist
176
	filters []requestFilter
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
}

func (c *ServiceConfig) checkRateLimits(user *User, req *auth.Request) bool {
	for _, rl := range c.rl {
		if !rl.AllowIncr(user, req) {
			return false
		}
	}
	for _, bl := range c.bl {
		if !bl.Allow(user, req) {
			return false
		}
	}
	return true
}

func (c *ServiceConfig) notifyBlacklists(user *User, req *auth.Request, resp *auth.Response) {
	for _, bl := range c.bl {
		bl.Incr(user, req, resp)
	}
ale's avatar
ale committed
197
198
199
200
201
202
203
204
205
206
207
208
209
}

// Config for the authentication server.
type Config struct {
	// Global configuration for backends.
	LDAPConfig *LDAPConfig `yaml:"ldap_config"`

	// List of enabled backends.
	EnabledBackends []string `yaml:"enabled_backends"`

	// Service-specific configuration.
	Services map[string]*ServiceConfig `yaml:"services"`

210
211
212
	// Named rate limiter configurations.
	RateLimiters map[string]*authRatelimiterConfig `yaml:"rate_limits"`

213
214
215
	// Configuration for the user-meta-server backend.
	UserMetaDBConfig *usermetadbclient.Config `yaml:"user_meta_server"`

216
217
218
219
220
	// Runtime versions of the above. These objects are shared by
	// all services, as they contain the actual map data.
	rl map[string]*Ratelimiter
	bl map[string]*Blacklist

ale's avatar
ale committed
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
	path string
}

func (c *Config) walkBackendSpecs(f func(*BackendSpec) error) error {
	for _, svc := range c.Services {
		for _, spec := range svc.BackendSpecs {
			if err := f(spec); err != nil {
				return err
			}
		}
	}
	return nil
}

func (c *Config) relativePath(path string) string {
	if strings.HasPrefix(path, "/") {
		return path
	}
	return filepath.Join(filepath.Dir(c.path), path)
}

242
func (c *Config) compile() error {
243
	// Build the global rate limiters and blacklists.
244
245
246
247
248
249
250
251
252
253
254
255
256
	c.rl = make(map[string]*Ratelimiter)
	c.bl = make(map[string]*Blacklist)
	for name, params := range c.RateLimiters {
		if err := params.compile(); err != nil {
			return err
		}
		if params.BlacklistTime > 0 {
			c.bl[name] = newBlacklist(params.Limit, params.Period, params.BlacklistTime)
		} else {
			c.rl[name] = newRatelimiter(params.Limit, params.Period)
		}
	}

257
	// Compile each service definition.
258
259
260
261
262
263
264
265
266
267
268
269
270
271
	for _, sc := range c.Services {
		for _, name := range sc.Ratelimits {
			config, ok := c.RateLimiters[name]
			if !ok {
				return fmt.Errorf("unknown rate limiter %s", name)
			}
			if rl, ok := c.rl[name]; ok {
				sc.rl = append(sc.rl, &authRatelimiter{config, rl})
			} else if bl, ok := c.bl[name]; ok {
				sc.bl = append(sc.bl, &authBlacklist{config, bl})
			} else {
				panic("can't find rl/bl")
			}
		}
272
273
274
275
276
277
278
279
280
281
282

		if sc.EnableDeviceTracking {
			if c.UserMetaDBConfig == nil {
				return errors.New("usermetadb config is missing")
			}
			dt, err := newDeviceFilter(c.UserMetaDBConfig)
			if err != nil {
				return err
			}
			sc.filters = append(sc.filters, dt)
		}
283
284
285
286
287
	}

	return nil
}

ale's avatar
ale committed
288
289
290
291
292
293
294
295
296
297
// LoadConfig loads the configuration from a YAML-encoded file.
func LoadConfig(path string) (*Config, error) {
	data, err := ioutil.ReadFile(path)
	if err != nil {
		return nil, err
	}
	config := Config{path: path}
	if err := yaml.Unmarshal(data, &config); err != nil {
		return nil, err
	}
298
299
300
	if err := config.compile(); err != nil {
		return nil, err
	}
ale's avatar
ale committed
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
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
	return &config, nil
}

// Server is the main authentication server object.
type Server struct {
	backends     []UserBackend
	config       *Config
	u2fShortTerm U2FShortTermStorage
}

func newError() *auth.Response {
	return &auth.Response{Status: auth.StatusError}
}

func newOK() *auth.Response {
	return &auth.Response{Status: auth.StatusOK}
}

// NewServer creates a Server using the given configuration.
func NewServer(config *Config, u2fShortTerm U2FShortTermStorage) (*Server, error) {
	s := &Server{
		config:       config,
		u2fShortTerm: u2fShortTerm,
	}
	for _, name := range config.EnabledBackends {
		var b UserBackend
		var err error
		switch name {
		case "file":
			b, err = newFileBackend(config)
		case "ldap":
			b, err = newLDAPBackend(config)
		default:
			err = fmt.Errorf("unknown backend %s", name)
		}
		if err != nil {
			return nil, err
		}
		s.backends = append(s.backends, b)
	}
	return s, nil
}

// Close the authentication server and release all associated resources.
func (s *Server) Close() {
	for _, b := range s.backends {
		b.Close()
	}
}

func (s *Server) getServiceConfig(service string) (*ServiceConfig, bool) {
	c, ok := s.config.Services[service]
	if !ok {
		c, ok = s.config.Services["default"]
	}
	return c, ok
}

359
360
361
362
363
364
365
366
367
368
369
func (s *Server) getUser(ctx context.Context, serviceConfig *ServiceConfig, username string) (*User, bool) {
	for _, spec := range serviceConfig.BackendSpecs {
		for _, b := range s.backends {
			if user, ok := b.GetUser(ctx, spec, username); ok {
				return user, true
			}
		}
	}
	return nil, false
}

ale's avatar
ale committed
370
371
372
373
374
375
376
377
// Authenticate a user with the parameters specified in the incoming AuthRequest.
func (s *Server) Authenticate(ctx context.Context, req *auth.Request) *auth.Response {
	serviceConfig, ok := s.getServiceConfig(req.Service)
	if !ok {
		log.Printf("unknown service %s", req.Service)
		return newError()
	}

378
	user, ok := s.getUser(ctx, serviceConfig, req.Username)
ale's avatar
ale committed
379
380
381
382
383
384
	if !ok {
		// User is unknown to all backends.
		log.Printf("unknown user %s", req.Username)
		return newError()
	}

385
386
387
388
389
390
	// Apply rate limiting and blacklisting _before_ invoking the
	// authentication handlers, as they may be CPU intensive.
	if allowed := serviceConfig.checkRateLimits(user, req); !allowed {
		return newError()
	}

ale's avatar
ale committed
391
392
393
394
395
396
397
398
	resp, err := s.authenticateUser(req, serviceConfig, user)
	if err != nil {
		resp = newError()
		log.Printf("auth: user=%s status=%s error=%s", req.Username, resp.Status.String(), err)
	} else {
		// Log the request and response.
		log.Printf("auth: user=%s status=%s", req.Username, resp.Status.String())
	}
399
400
401
402
403
404
405

	// Notify blacklists of the result.
	serviceConfig.notifyBlacklists(user, req, resp)

	return resp
}

ale's avatar
ale committed
406
407
408
// Authenticate a user. Returning an error should result in an
// AuthResponse with StatusError.
func (s *Server) authenticateUser(req *auth.Request, serviceConfig *ServiceConfig, user *User) (resp *auth.Response, err error) {
ale's avatar
ale committed
409
410
411
	// Verify different credentials depending on whether the user
	// has 2FA enabled or not, and on whether the service itself
	// supports challenge-response authentication.
ale's avatar
ale committed
412
	if serviceConfig.Enforce2FA || user.Has2FA() {
ale's avatar
ale committed
413
		if serviceConfig.ChallengeResponse {
ale's avatar
ale committed
414
			resp, err = s.authenticateUserWith2FA(user, req)
ale's avatar
ale committed
415
		} else {
ale's avatar
ale committed
416
			resp, err = s.authenticateUserWithASP(user, req)
ale's avatar
ale committed
417
418
		}
	} else {
ale's avatar
ale committed
419
420
421
422
		resp, err = s.authenticateUserWithPassword(user, req)
	}
	if err != nil {
		return
423
424
425
426
427
428
429
430
	}

	// Process the response through filters (device info checks,
	// etc) that may or may not change the response itself.
	for _, f := range serviceConfig.filters {
		if resp.Status == auth.StatusError {
			break
		}
431
		resp = f.Filter(user, req, resp)
ale's avatar
ale committed
432
433
434
435
436
437
	}

	// If the response is successful, augment it with user information.
	if resp.Status == auth.StatusOK {
		resp.UserInfo = user.UserInfo()
	}
ale's avatar
ale committed
438
	return
ale's avatar
ale committed
439
440
}

ale's avatar
ale committed
441
func (s *Server) authenticateUserWithPassword(user *User, req *auth.Request) (*auth.Response, error) {
ale's avatar
ale committed
442
443
	// Ok we only need to check the password here.
	if checkPassword(req.Password, user.EncryptedPassword) {
ale's avatar
ale committed
444
		return newOK(), nil
ale's avatar
ale committed
445
	}
ale's avatar
ale committed
446
	return nil, errors.New("wrong password")
ale's avatar
ale committed
447
448
}

ale's avatar
ale committed
449
func (s *Server) authenticateUserWithASP(user *User, req *auth.Request) (*auth.Response, error) {
ale's avatar
ale committed
450
451
	for _, asp := range user.AppSpecificPasswords {
		if asp.Service == req.Service && checkPassword(req.Password, asp.EncryptedPassword) {
ale's avatar
ale committed
452
			return newOK(), nil
ale's avatar
ale committed
453
454
		}
	}
ale's avatar
ale committed
455
	return nil, errors.New("wrong app-specific password")
ale's avatar
ale committed
456
457
}

ale's avatar
ale committed
458
func (s *Server) authenticateUserWith2FA(user *User, req *auth.Request) (*auth.Response, error) {
ale's avatar
ale committed
459
460
	// First of all verify the password.
	if !checkPassword(req.Password, user.EncryptedPassword) {
ale's avatar
ale committed
461
		return nil, errors.New("wrong password")
ale's avatar
ale committed
462
463
464
465
466
467
468
469
470
	}

	// If the request contains one of the 2FA attributes, verify
	// it. But if it contains none, we return with
	// AuthStatusInsufficientCredentials and potentially a 2FA
	// hint (for U2F).
	switch {
	case req.U2FResponse != nil:
		if user.HasU2F() && s.checkU2F(user, req.U2FResponse) {
ale's avatar
ale committed
471
			return newOK(), nil
ale's avatar
ale committed
472
		}
ale's avatar
ale committed
473
		return nil, errors.New("bad U2F response")
ale's avatar
ale committed
474
475
	case req.OTP != "":
		if user.HasOTP() && checkOTP(req.OTP, user.TOTPSecret) {
ale's avatar
ale committed
476
			return newOK(), nil
ale's avatar
ale committed
477
		}
ale's avatar
ale committed
478
		return nil, errors.New("bad OTP")
ale's avatar
ale committed
479
480
481
482
483
484
485
486
	default:
		resp := &auth.Response{
			Status: auth.StatusInsufficientCredentials,
		}
		if req.U2FAppID != "" && user.HasU2F() {
			resp.TFAMethod = auth.TFAMethodU2F
			signReq, err := s.u2fSignRequest(user, req.U2FAppID)
			if err != nil {
ale's avatar
ale committed
487
				return nil, err
ale's avatar
ale committed
488
489
490
491
492
			}
			resp.U2FSignRequest = signReq
		} else if user.HasOTP() {
			resp.TFAMethod = auth.TFAMethodOTP
		}
ale's avatar
ale committed
493
		return resp, nil
ale's avatar
ale committed
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
	}
}

func (s *Server) u2fSignRequest(user *User, appID string) (*u2f.WebSignRequest, error) {
	challenge, err := u2f.NewChallenge(appID, []string{appID})
	if err != nil {
		return nil, err
	}

	if err := s.u2fShortTerm.SetUserChallenge(user.Name, challenge); err != nil {
		return nil, err
	}

	return challenge.SignRequest(user.U2FRegistrations), nil
}

func (s *Server) checkU2F(user *User, resp *u2f.SignResponse) bool {
	challenge, ok := s.u2fShortTerm.GetUserChallenge(user.Name)
	if !ok {
		return false
	}
	for _, reg := range user.U2FRegistrations {
		_, err := reg.Authenticate(*resp, *challenge, 0)
		if err == nil {
			return true
		}
	}
	return false
}

func checkPassword(password, hash []byte) bool {
	err := scrypt.CompareHashAndPassword(hash, password)
	return err == nil
}

func checkOTP(otp, secret string) bool {
	return totp.Validate(otp, secret)
}