summaryrefslogtreecommitdiff
path: root/modules/caddytls/connpolicy.go
blob: 74c83241107b2b08376838077dc5a9ed4c001e22 (plain)
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
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
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
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
// Copyright 2015 Matthew Holt and The Caddy Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package caddytls

import (
	"crypto/tls"
	"crypto/x509"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"

	"github.com/caddyserver/caddy/v2"
	"github.com/mholt/acmez"
	"go.uber.org/zap"
)

func init() {
	caddy.RegisterModule(LeafCertClientAuth{})
}

// ConnectionPolicies govern the establishment of TLS connections. It is
// an ordered group of connection policies; the first matching policy will
// be used to configure TLS connections at handshake-time.
type ConnectionPolicies []*ConnectionPolicy

// Provision sets up each connection policy. It should be called
// during the Validate() phase, after the TLS app (if any) is
// already set up.
func (cp ConnectionPolicies) Provision(ctx caddy.Context) error {
	for i, pol := range cp {
		// matchers
		mods, err := ctx.LoadModule(pol, "MatchersRaw")
		if err != nil {
			return fmt.Errorf("loading handshake matchers: %v", err)
		}
		for _, modIface := range mods.(map[string]any) {
			cp[i].matchers = append(cp[i].matchers, modIface.(ConnectionMatcher))
		}

		// enable HTTP/2 by default
		if pol.ALPN == nil {
			pol.ALPN = append(pol.ALPN, defaultALPN...)
		}

		// pre-build standard TLS config so we don't have to at handshake-time
		err = pol.buildStandardTLSConfig(ctx)
		if err != nil {
			return fmt.Errorf("connection policy %d: building standard TLS config: %s", i, err)
		}

		if pol.ClientAuthentication != nil && len(pol.ClientAuthentication.VerifiersRaw) > 0 {
			clientCertValidations, err := ctx.LoadModule(pol.ClientAuthentication, "VerifiersRaw")
			if err != nil {
				return fmt.Errorf("loading client cert verifiers: %v", err)
			}
			for _, validator := range clientCertValidations.([]any) {
				cp[i].ClientAuthentication.verifiers = append(cp[i].ClientAuthentication.verifiers, validator.(ClientCertificateVerifier))
			}
		}
	}

	return nil
}

// TLSConfig returns a standard-lib-compatible TLS configuration which
// selects the first matching policy based on the ClientHello.
func (cp ConnectionPolicies) TLSConfig(_ caddy.Context) *tls.Config {
	// using ServerName to match policies is extremely common, especially in configs
	// with lots and lots of different policies; we can fast-track those by indexing
	// them by SNI, so we don't have to iterate potentially thousands of policies
	// (TODO: this map does not account for wildcards, see if this is a problem in practice? look for reports of high connection latency with wildcard certs but low latency for non-wildcards in multi-thousand-cert deployments)
	indexedBySNI := make(map[string]ConnectionPolicies)
	if len(cp) > 30 {
		for _, p := range cp {
			for _, m := range p.matchers {
				if sni, ok := m.(MatchServerName); ok {
					for _, sniName := range sni {
						indexedBySNI[sniName] = append(indexedBySNI[sniName], p)
					}
				}
			}
		}
	}

	return &tls.Config{
		MinVersion: tls.VersionTLS12,
		GetConfigForClient: func(hello *tls.ClientHelloInfo) (*tls.Config, error) {
			// filter policies by SNI first, if possible, to speed things up
			// when there may be lots of policies
			possiblePolicies := cp
			if indexedPolicies, ok := indexedBySNI[hello.ServerName]; ok {
				possiblePolicies = indexedPolicies
			}

		policyLoop:
			for _, pol := range possiblePolicies {
				for _, matcher := range pol.matchers {
					if !matcher.Match(hello) {
						continue policyLoop
					}
				}
				return pol.TLSConfig, nil
			}

			return nil, fmt.Errorf("no server TLS configuration available for ClientHello: %+v", hello)
		},
	}
}

// ConnectionPolicy specifies the logic for handling a TLS handshake.
// An empty policy is valid; safe and sensible defaults will be used.
type ConnectionPolicy struct {
	// How to match this policy with a TLS ClientHello. If
	// this policy is the first to match, it will be used.
	MatchersRaw caddy.ModuleMap `json:"match,omitempty" caddy:"namespace=tls.handshake_match"`

	// How to choose a certificate if more than one matched
	// the given ServerName (SNI) value.
	CertSelection *CustomCertSelectionPolicy `json:"certificate_selection,omitempty"`

	// The list of cipher suites to support. Caddy's
	// defaults are modern and secure.
	CipherSuites []string `json:"cipher_suites,omitempty"`

	// The list of elliptic curves to support. Caddy's
	// defaults are modern and secure.
	Curves []string `json:"curves,omitempty"`

	// Protocols to use for Application-Layer Protocol
	// Negotiation (ALPN) during the handshake.
	ALPN []string `json:"alpn,omitempty"`

	// Minimum TLS protocol version to allow. Default: `tls1.2`
	ProtocolMin string `json:"protocol_min,omitempty"`

	// Maximum TLS protocol version to allow. Default: `tls1.3`
	ProtocolMax string `json:"protocol_max,omitempty"`

	// Enables and configures TLS client authentication.
	ClientAuthentication *ClientAuthentication `json:"client_authentication,omitempty"`

	// DefaultSNI becomes the ServerName in a ClientHello if there
	// is no policy configured for the empty SNI value.
	DefaultSNI string `json:"default_sni,omitempty"`

	// FallbackSNI becomes the ServerName in a ClientHello if
	// the original ServerName doesn't match any certificates
	// in the cache. The use cases for this are very niche;
	// typically if a client is a CDN and passes through the
	// ServerName of the downstream handshake but can accept
	// a certificate with the origin's hostname instead, then
	// you would set this to your origin's hostname. Note that
	// Caddy must be managing a certificate for this name.
	//
	// This feature is EXPERIMENTAL and subject to change or removal.
	FallbackSNI string `json:"fallback_sni,omitempty"`

	// Also known as "SSLKEYLOGFILE", TLS secrets will be written to
	// this file in NSS key log format which can then be parsed by
	// Wireshark and other tools. This is INSECURE as it allows other
	// programs or tools to decrypt TLS connections. However, this
	// capability can be useful for debugging and troubleshooting.
	// **ENABLING THIS LOG COMPROMISES SECURITY!**
	//
	// This feature is EXPERIMENTAL and subject to change or removal.
	InsecureSecretsLog string `json:"insecure_secrets_log,omitempty"`

	// TLSConfig is the fully-formed, standard lib TLS config
	// used to serve TLS connections. Provision all
	// ConnectionPolicies to populate this. It is exported only
	// so it can be minimally adjusted after provisioning
	// if necessary (like to adjust NextProtos to disable HTTP/2),
	// and may be unexported in the future.
	TLSConfig *tls.Config `json:"-"`

	matchers []ConnectionMatcher
}

func (p *ConnectionPolicy) buildStandardTLSConfig(ctx caddy.Context) error {
	tlsAppIface, err := ctx.App("tls")
	if err != nil {
		return fmt.Errorf("getting tls app: %v", err)
	}
	tlsApp := tlsAppIface.(*TLS)

	// fill in some "easy" default values, but for other values
	// (such as slices), we should ensure that they start empty
	// so the user-provided config can fill them in; then we will
	// fill in a default config at the end if they are still unset
	cfg := &tls.Config{
		NextProtos: p.ALPN,
		GetCertificate: func(hello *tls.ClientHelloInfo) (*tls.Certificate, error) {
			// TODO: I don't love how this works: we pre-build certmagic configs
			// so that handshakes are faster. Unfortunately, certmagic configs are
			// comprised of settings from both a TLS connection policy and a TLS
			// automation policy. The only two fields (as of March 2020; v2 beta 17)
			// of a certmagic config that come from the TLS connection policy are
			// CertSelection and DefaultServerName, so an automation policy is what
			// builds the base certmagic config. Since the pre-built config is
			// shared, I don't think we can change any of its fields per-handshake,
			// hence the awkward shallow copy (dereference) here and the subsequent
			// changing of some of its fields. I'm worried this dereference allocates
			// more at handshake-time, but I don't know how to practically pre-build
			// a certmagic config for each combination of conn policy + automation policy...
			cfg := *tlsApp.getConfigForName(hello.ServerName)
			if p.CertSelection != nil {
				// you would think we could just set this whether or not
				// p.CertSelection is nil, but that leads to panics if
				// it is, because cfg.CertSelection is an interface,
				// so it will have a non-nil value even if the actual
				// value underlying it is nil (sigh)
				cfg.CertSelection = p.CertSelection
			}
			cfg.DefaultServerName = p.DefaultSNI
			cfg.FallbackServerName = p.FallbackSNI
			return cfg.GetCertificate(hello)
		},
		MinVersion: tls.VersionTLS12,
		MaxVersion: tls.VersionTLS13,
	}

	// session tickets support
	if tlsApp.SessionTickets != nil {
		cfg.SessionTicketsDisabled = tlsApp.SessionTickets.Disabled

		// session ticket key rotation
		tlsApp.SessionTickets.register(cfg)
		ctx.OnCancel(func() {
			// do cleanup when the context is canceled because,
			// though unlikely, it is possible that a context
			// needing a TLS server config could exist for less
			// than the lifetime of the whole app
			tlsApp.SessionTickets.unregister(cfg)
		})
	}

	// TODO: Clean up session ticket active locks in storage if app (or process) is being closed!

	// add all the cipher suites in order, without duplicates
	cipherSuitesAdded := make(map[uint16]struct{})
	for _, csName := range p.CipherSuites {
		csID := CipherSuiteID(csName)
		if csID == 0 {
			return fmt.Errorf("unsupported cipher suite: %s", csName)
		}
		if _, ok := cipherSuitesAdded[csID]; !ok {
			cipherSuitesAdded[csID] = struct{}{}
			cfg.CipherSuites = append(cfg.CipherSuites, csID)
		}
	}

	// add all the curve preferences in order, without duplicates
	curvesAdded := make(map[tls.CurveID]struct{})
	for _, curveName := range p.Curves {
		curveID := SupportedCurves[curveName]
		if _, ok := curvesAdded[curveID]; !ok {
			curvesAdded[curveID] = struct{}{}
			cfg.CurvePreferences = append(cfg.CurvePreferences, curveID)
		}
	}

	// ensure ALPN includes the ACME TLS-ALPN protocol
	var alpnFound bool
	for _, a := range p.ALPN {
		if a == acmez.ACMETLS1Protocol {
			alpnFound = true
			break
		}
	}
	if !alpnFound && (cfg.NextProtos == nil || len(cfg.NextProtos) > 0) {
		cfg.NextProtos = append(cfg.NextProtos, acmez.ACMETLS1Protocol)
	}

	// min and max protocol versions
	if (p.ProtocolMin != "" && p.ProtocolMax != "") && p.ProtocolMin > p.ProtocolMax {
		return fmt.Errorf("protocol min (%x) cannot be greater than protocol max (%x)", p.ProtocolMin, p.ProtocolMax)
	}
	if p.ProtocolMin != "" {
		cfg.MinVersion = SupportedProtocols[p.ProtocolMin]
	}
	if p.ProtocolMax != "" {
		cfg.MaxVersion = SupportedProtocols[p.ProtocolMax]
	}

	// client authentication
	if p.ClientAuthentication != nil {
		err := p.ClientAuthentication.ConfigureTLSConfig(cfg)
		if err != nil {
			return fmt.Errorf("configuring TLS client authentication: %v", err)
		}
	}

	if p.InsecureSecretsLog != "" {
		filename, err := caddy.NewReplacer().ReplaceOrErr(p.InsecureSecretsLog, true, true)
		if err != nil {
			return err
		}
		filename, err = filepath.Abs(filename)
		if err != nil {
			return err
		}
		logFile, _, err := secretsLogPool.LoadOrNew(filename, func() (caddy.Destructor, error) {
			w, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0o600)
			return destructableWriter{w}, err
		})
		if err != nil {
			return err
		}
		ctx.OnCancel(func() { _, _ = secretsLogPool.Delete(filename) })

		cfg.KeyLogWriter = logFile.(io.Writer)

		tlsApp.logger.Warn("TLS SECURITY COMPROMISED: secrets logging is enabled!",
			zap.String("log_filename", filename))
	}

	setDefaultTLSParams(cfg)

	p.TLSConfig = cfg

	return nil
}

// SettingsEmpty returns true if p's settings (fields
// except the matchers) are all empty/unset.
func (p ConnectionPolicy) SettingsEmpty() bool {
	return p.CertSelection == nil &&
		p.CipherSuites == nil &&
		p.Curves == nil &&
		p.ALPN == nil &&
		p.ProtocolMin == "" &&
		p.ProtocolMax == "" &&
		p.ClientAuthentication == nil &&
		p.DefaultSNI == "" &&
		p.InsecureSecretsLog == ""
}

// ClientAuthentication configures TLS client auth.
type ClientAuthentication struct {
	// A list of base64 DER-encoded CA certificates
	// against which to validate client certificates.
	// Client certs which are not signed by any of
	// these CAs will be rejected.
	TrustedCACerts []string `json:"trusted_ca_certs,omitempty"`

	// TrustedCACertPEMFiles is a list of PEM file names
	// from which to load certificates of trusted CAs.
	// Client certificates which are not signed by any of
	// these CA certificates will be rejected.
	TrustedCACertPEMFiles []string `json:"trusted_ca_certs_pem_files,omitempty"`

	// DEPRECATED: This field is deprecated and will be removed in
	// a future version. Please use the `validators` field instead
	// with the tls.client_auth.leaf module instead.
	//
	// A list of base64 DER-encoded client leaf certs
	// to accept. If this list is not empty, client certs
	// which are not in this list will be rejected.
	TrustedLeafCerts []string `json:"trusted_leaf_certs,omitempty"`

	// Client certificate verification modules. These can perform
	// custom client authentication checks, such as ensuring the
	// certificate is not revoked.
	VerifiersRaw []json.RawMessage `json:"verifiers,omitempty" caddy:"namespace=tls.client_auth inline_key=verifier"`

	verifiers []ClientCertificateVerifier

	// The mode for authenticating the client. Allowed values are:
	//
	// Mode | Description
	// -----|---------------
	// `request` | Ask clients for a certificate, but allow even if there isn't one; do not verify it
	// `require` | Require clients to present a certificate, but do not verify it
	// `verify_if_given` | Ask clients for a certificate; allow even if there isn't one, but verify it if there is
	// `require_and_verify` | Require clients to present a valid certificate that is verified
	//
	// The default mode is `require_and_verify` if any
	// TrustedCACerts or TrustedCACertPEMFiles or TrustedLeafCerts
	// are provided; otherwise, the default mode is `require`.
	Mode string `json:"mode,omitempty"`

	existingVerifyPeerCert func([][]byte, [][]*x509.Certificate) error
}

// Active returns true if clientauth has an actionable configuration.
func (clientauth ClientAuthentication) Active() bool {
	return len(clientauth.TrustedCACerts) > 0 ||
		len(clientauth.TrustedCACertPEMFiles) > 0 ||
		len(clientauth.TrustedLeafCerts) > 0 || // TODO: DEPRECATED
		len(clientauth.VerifiersRaw) > 0 ||
		len(clientauth.Mode) > 0
}

// ConfigureTLSConfig sets up cfg to enforce clientauth's configuration.
func (clientauth *ClientAuthentication) ConfigureTLSConfig(cfg *tls.Config) error {
	// if there's no actionable client auth, simply disable it
	if !clientauth.Active() {
		cfg.ClientAuth = tls.NoClientCert
		return nil
	}

	// enforce desired mode of client authentication
	if len(clientauth.Mode) > 0 {
		switch clientauth.Mode {
		case "request":
			cfg.ClientAuth = tls.RequestClientCert
		case "require":
			cfg.ClientAuth = tls.RequireAnyClientCert
		case "verify_if_given":
			cfg.ClientAuth = tls.VerifyClientCertIfGiven
		case "require_and_verify":
			cfg.ClientAuth = tls.RequireAndVerifyClientCert
		default:
			return fmt.Errorf("client auth mode not recognized: %s", clientauth.Mode)
		}
	} else {
		// otherwise, set a safe default mode
		if len(clientauth.TrustedCACerts) > 0 ||
			len(clientauth.TrustedCACertPEMFiles) > 0 ||
			len(clientauth.TrustedLeafCerts) > 0 {
			cfg.ClientAuth = tls.RequireAndVerifyClientCert
		} else {
			cfg.ClientAuth = tls.RequireAnyClientCert
		}
	}

	// enforce CA verification by adding CA certs to the ClientCAs pool
	if len(clientauth.TrustedCACerts) > 0 || len(clientauth.TrustedCACertPEMFiles) > 0 {
		caPool := x509.NewCertPool()
		for _, clientCAString := range clientauth.TrustedCACerts {
			clientCA, err := decodeBase64DERCert(clientCAString)
			if err != nil {
				return fmt.Errorf("parsing certificate: %v", err)
			}
			caPool.AddCert(clientCA)
		}
		for _, pemFile := range clientauth.TrustedCACertPEMFiles {
			pemContents, err := os.ReadFile(pemFile)
			if err != nil {
				return fmt.Errorf("reading %s: %v", pemFile, err)
			}
			caPool.AppendCertsFromPEM(pemContents)
		}
		cfg.ClientCAs = caPool
	}

	// TODO: DEPRECATED: Only here for backwards compatibility.
	// If leaf cert is specified, enforce by adding a client auth module
	if len(clientauth.TrustedLeafCerts) > 0 {
		caddy.Log().Named("tls.connection_policy").Warn("trusted_leaf_certs is deprecated; use leaf verifier module instead")
		var trustedLeafCerts []*x509.Certificate
		for _, clientCertString := range clientauth.TrustedLeafCerts {
			clientCert, err := decodeBase64DERCert(clientCertString)
			if err != nil {
				return fmt.Errorf("parsing certificate: %v", err)
			}
			trustedLeafCerts = append(trustedLeafCerts, clientCert)
		}
		clientauth.verifiers = append(clientauth.verifiers, LeafCertClientAuth{TrustedLeafCerts: trustedLeafCerts})
	}

	// if a custom verification function already exists, wrap it
	clientauth.existingVerifyPeerCert = cfg.VerifyPeerCertificate
	cfg.VerifyPeerCertificate = clientauth.verifyPeerCertificate
	return nil
}

// verifyPeerCertificate is for use as a tls.Config.VerifyPeerCertificate
// callback to do custom client certificate verification. It is intended
// for installation only by clientauth.ConfigureTLSConfig().
func (clientauth *ClientAuthentication) verifyPeerCertificate(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error {
	// first use any pre-existing custom verification function
	if clientauth.existingVerifyPeerCert != nil {
		err := clientauth.existingVerifyPeerCert(rawCerts, verifiedChains)
		if err != nil {
			return err
		}
	}
	for _, verifier := range clientauth.verifiers {
		err := verifier.VerifyClientCertificate(rawCerts, verifiedChains)
		if err != nil {
			return err
		}
	}
	return nil
}

// decodeBase64DERCert base64-decodes, then DER-decodes, certStr.
func decodeBase64DERCert(certStr string) (*x509.Certificate, error) {
	derBytes, err := base64.StdEncoding.DecodeString(certStr)
	if err != nil {
		return nil, err
	}
	return x509.ParseCertificate(derBytes)
}

// setDefaultTLSParams sets the default TLS cipher suites, protocol versions,
// and server preferences of cfg if they are not already set; it does not
// overwrite values, only fills in missing values.
func setDefaultTLSParams(cfg *tls.Config) {
	if len(cfg.CipherSuites) == 0 {
		cfg.CipherSuites = getOptimalDefaultCipherSuites()
	}

	// Not a cipher suite, but still important for mitigating protocol downgrade attacks
	// (prepend since having it at end breaks http2 due to non-h2-approved suites before it)
	cfg.CipherSuites = append([]uint16{tls.TLS_FALLBACK_SCSV}, cfg.CipherSuites...)

	if len(cfg.CurvePreferences) == 0 {
		cfg.CurvePreferences = defaultCurves
	}

	if cfg.MinVersion == 0 {
		cfg.MinVersion = tls.VersionTLS12
	}
	if cfg.MaxVersion == 0 {
		cfg.MaxVersion = tls.VersionTLS13
	}
}

// LeafCertClientAuth verifies the client's leaf certificate.
type LeafCertClientAuth struct {
	TrustedLeafCerts []*x509.Certificate
}

// CaddyModule returns the Caddy module information.
func (LeafCertClientAuth) CaddyModule() caddy.ModuleInfo {
	return caddy.ModuleInfo{
		ID:  "tls.client_auth.leaf",
		New: func() caddy.Module { return new(LeafCertClientAuth) },
	}
}

func (l LeafCertClientAuth) VerifyClientCertificate(rawCerts [][]byte, _ [][]*x509.Certificate) error {
	if len(rawCerts) == 0 {
		return fmt.Errorf("no client certificate provided")
	}

	remoteLeafCert, err := x509.ParseCertificate(rawCerts[0])
	if err != nil {
		return fmt.Errorf("can't parse the given certificate: %s", err.Error())
	}

	for _, trustedLeafCert := range l.TrustedLeafCerts {
		if remoteLeafCert.Equal(trustedLeafCert) {
			return nil
		}
	}

	return fmt.Errorf("client leaf certificate failed validation")
}

// PublicKeyAlgorithm is a JSON-unmarshalable wrapper type.
type PublicKeyAlgorithm x509.PublicKeyAlgorithm

// UnmarshalJSON satisfies json.Unmarshaler.
func (a *PublicKeyAlgorithm) UnmarshalJSON(b []byte) error {
	algoStr := strings.ToLower(strings.Trim(string(b), `"`))
	algo, ok := publicKeyAlgorithms[algoStr]
	if !ok {
		return fmt.Errorf("unrecognized public key algorithm: %s (expected one of %v)",
			algoStr, publicKeyAlgorithms)
	}
	*a = PublicKeyAlgorithm(algo)
	return nil
}

// ConnectionMatcher is a type which matches TLS handshakes.
type ConnectionMatcher interface {
	Match(*tls.ClientHelloInfo) bool
}

// ClientCertificateVerifier is a type which verifies client certificates.
// It is called during verifyPeerCertificate in the TLS handshake.
type ClientCertificateVerifier interface {
	VerifyClientCertificate(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error
}

var defaultALPN = []string{"h2", "http/1.1"}

type destructableWriter struct{ *os.File }

func (d destructableWriter) Destruct() error { return d.Close() }

var secretsLogPool = caddy.NewUsagePool()