1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
34 // Deprecated: SSLv3 is cryptographically broken, and is no longer
35 // supported by this package. See golang.org/issue/32716.
39 // VersionName returns the name for the provided TLS version number
40 // (e.g. "TLS 1.3"), or a fallback representation of the value if the
41 // version is not implemented by this package.
42 func VersionName(version uint16) string {
55 return fmt.Sprintf("0x%04X", version)
60 maxPlaintext = 16384 // maximum plaintext payload length
61 maxCiphertext = 16384 + 2048 // maximum ciphertext payload length
62 maxCiphertextTLS13 = 16384 + 256 // maximum ciphertext length in TLS 1.3
63 recordHeaderLen = 5 // record header length
64 maxHandshake = 65536 // maximum handshake we support (protocol max is 16 MB)
65 maxUselessRecords = 16 // maximum number of consecutive non-advancing records
72 recordTypeChangeCipherSpec recordType = 20
73 recordTypeAlert recordType = 21
74 recordTypeHandshake recordType = 22
75 recordTypeApplicationData recordType = 23
78 // TLS handshake message types.
80 typeHelloRequest uint8 = 0
81 typeClientHello uint8 = 1
82 typeServerHello uint8 = 2
83 typeNewSessionTicket uint8 = 4
84 typeEndOfEarlyData uint8 = 5
85 typeEncryptedExtensions uint8 = 8
86 typeCertificate uint8 = 11
87 typeServerKeyExchange uint8 = 12
88 typeCertificateRequest uint8 = 13
89 typeServerHelloDone uint8 = 14
90 typeCertificateVerify uint8 = 15
91 typeClientKeyExchange uint8 = 16
92 typeFinished uint8 = 20
93 typeCertificateStatus uint8 = 22
94 typeKeyUpdate uint8 = 24
95 typeNextProtocol uint8 = 67 // Not IANA assigned
96 typeMessageHash uint8 = 254 // synthetic message
99 // TLS compression types.
101 compressionNone uint8 = 0
104 // TLS extension numbers
106 extensionServerName uint16 = 0
107 extensionStatusRequest uint16 = 5
108 extensionSupportedCurves uint16 = 10 // supported_groups in TLS 1.3, see RFC 8446, Section 4.2.7
109 extensionSupportedPoints uint16 = 11
110 extensionSignatureAlgorithms uint16 = 13
111 extensionALPN uint16 = 16
112 extensionSCT uint16 = 18
113 extensionExtendedMasterSecret uint16 = 23
114 extensionSessionTicket uint16 = 35
115 extensionPreSharedKey uint16 = 41
116 extensionEarlyData uint16 = 42
117 extensionSupportedVersions uint16 = 43
118 extensionCookie uint16 = 44
119 extensionPSKModes uint16 = 45
120 extensionCertificateAuthorities uint16 = 47
121 extensionSignatureAlgorithmsCert uint16 = 50
122 extensionKeyShare uint16 = 51
123 extensionQUICTransportParameters uint16 = 57
124 extensionRenegotiationInfo uint16 = 0xff01
127 // TLS signaling cipher suite values
129 scsvRenegotiation uint16 = 0x00ff
132 // CurveID is the type of a TLS identifier for an elliptic curve. See
133 // https://www.iana.org/assignments/tls-parameters/tls-parameters.xml#tls-parameters-8.
135 // In TLS 1.3, this type is called NamedGroup, but at this time this library
136 // only supports Elliptic Curve based groups. See RFC 8446, Section 4.2.7.
140 CurveP256 CurveID = 23
141 CurveP384 CurveID = 24
142 CurveP521 CurveID = 25
146 // TLS 1.3 Key Share. See RFC 8446, Section 4.2.8.
147 type keyShare struct {
152 // TLS 1.3 PSK Key Exchange Modes. See RFC 8446, Section 4.2.9.
154 pskModePlain uint8 = 0
158 // TLS 1.3 PSK Identity. Can be a Session Ticket, or a reference to a saved
159 // session. See RFC 8446, Section 4.2.11.
160 type pskIdentity struct {
162 obfuscatedTicketAge uint32
165 // TLS Elliptic Curve Point Formats
166 // https://www.iana.org/assignments/tls-parameters/tls-parameters.xml#tls-parameters-9
168 pointFormatUncompressed uint8 = 0
171 // TLS CertificateStatusType (RFC 3546)
173 statusTypeOCSP uint8 = 1
176 // Certificate types (for certificateRequestMsg)
179 certTypeECDSASign = 64 // ECDSA or EdDSA keys, see RFC 8422, Section 3.
182 // Signature algorithms (for internal signaling use). Starting at 225 to avoid overlap with
183 // TLS 1.2 codepoints (RFC 5246, Appendix A.4.1), with which these have nothing to do.
185 signaturePKCS1v15 uint8 = iota + 225
191 // directSigning is a standard Hash value that signals that no pre-hashing
192 // should be performed, and that the input should be signed directly. It is the
193 // hash function associated with the Ed25519 signature scheme.
194 var directSigning crypto.Hash = 0
196 // defaultSupportedSignatureAlgorithms contains the signature and hash algorithms that
197 // the code advertises as supported in a TLS 1.2+ ClientHello and in a TLS 1.2+
198 // CertificateRequest. The two fields are merged to match with TLS 1.3.
199 // Note that in TLS 1.2, the ECDSA algorithms are not constrained to P-256, etc.
200 var defaultSupportedSignatureAlgorithms = []SignatureScheme{
202 ECDSAWithP256AndSHA256,
209 ECDSAWithP384AndSHA384,
210 ECDSAWithP521AndSHA512,
215 // helloRetryRequestRandom is set as the Random value of a ServerHello
216 // to signal that the message is actually a HelloRetryRequest.
217 var helloRetryRequestRandom = []byte{ // See RFC 8446, Section 4.1.3.
218 0xCF, 0x21, 0xAD, 0x74, 0xE5, 0x9A, 0x61, 0x11,
219 0xBE, 0x1D, 0x8C, 0x02, 0x1E, 0x65, 0xB8, 0x91,
220 0xC2, 0xA2, 0x11, 0x16, 0x7A, 0xBB, 0x8C, 0x5E,
221 0x07, 0x9E, 0x09, 0xE2, 0xC8, 0xA8, 0x33, 0x9C,
225 // downgradeCanaryTLS12 or downgradeCanaryTLS11 is embedded in the server
226 // random as a downgrade protection if the server would be capable of
227 // negotiating a higher version. See RFC 8446, Section 4.1.3.
228 downgradeCanaryTLS12 = "DOWNGRD\x01"
229 downgradeCanaryTLS11 = "DOWNGRD\x00"
232 // testingOnlyForceDowngradeCanary is set in tests to force the server side to
233 // include downgrade canaries even if it's using its highers supported version.
234 var testingOnlyForceDowngradeCanary bool
236 // ConnectionState records basic TLS details about the connection.
237 type ConnectionState struct {
238 // Version is the TLS version used by the connection (e.g. VersionTLS12).
241 // HandshakeComplete is true if the handshake has concluded.
242 HandshakeComplete bool
244 // DidResume is true if this connection was successfully resumed from a
245 // previous session with a session ticket or similar mechanism.
248 // CipherSuite is the cipher suite negotiated for the connection (e.g.
249 // TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, TLS_AES_128_GCM_SHA256).
252 // NegotiatedProtocol is the application protocol negotiated with ALPN.
253 NegotiatedProtocol string
255 // NegotiatedProtocolIsMutual used to indicate a mutual NPN negotiation.
257 // Deprecated: this value is always true.
258 NegotiatedProtocolIsMutual bool
260 // ServerName is the value of the Server Name Indication extension sent by
261 // the client. It's available both on the server and on the client side.
264 // PeerCertificates are the parsed certificates sent by the peer, in the
265 // order in which they were sent. The first element is the leaf certificate
266 // that the connection is verified against.
268 // On the client side, it can't be empty. On the server side, it can be
269 // empty if Config.ClientAuth is not RequireAnyClientCert or
270 // RequireAndVerifyClientCert.
272 // PeerCertificates and its contents should not be modified.
273 PeerCertificates []*x509.Certificate
275 // VerifiedChains is a list of one or more chains where the first element is
276 // PeerCertificates[0] and the last element is from Config.RootCAs (on the
277 // client side) or Config.ClientCAs (on the server side).
279 // On the client side, it's set if Config.InsecureSkipVerify is false. On
280 // the server side, it's set if Config.ClientAuth is VerifyClientCertIfGiven
281 // (and the peer provided a certificate) or RequireAndVerifyClientCert.
283 // VerifiedChains and its contents should not be modified.
284 VerifiedChains [][]*x509.Certificate
286 // SignedCertificateTimestamps is a list of SCTs provided by the peer
287 // through the TLS handshake for the leaf certificate, if any.
288 SignedCertificateTimestamps [][]byte
290 // OCSPResponse is a stapled Online Certificate Status Protocol (OCSP)
291 // response provided by the peer for the leaf certificate, if any.
294 // TLSUnique contains the "tls-unique" channel binding value (see RFC 5929,
295 // Section 3). This value will be nil for TLS 1.3 connections and for
296 // resumed connections that don't support Extended Master Secret (RFC 7627).
299 // ekm is a closure exposed via ExportKeyingMaterial.
300 ekm func(label string, context []byte, length int) ([]byte, error)
303 // ExportKeyingMaterial returns length bytes of exported key material in a new
304 // slice as defined in RFC 5705. If context is nil, it is not used as part of
305 // the seed. If the connection was set to allow renegotiation via
306 // Config.Renegotiation, this function will return an error.
308 // There are conditions in which the returned values might not be unique to a
309 // connection. See the Security Considerations sections of RFC 5705 and RFC 7627,
310 // and https://mitls.org/pages/attacks/3SHAKE#channelbindings.
311 func (cs *ConnectionState) ExportKeyingMaterial(label string, context []byte, length int) ([]byte, error) {
312 return cs.ekm(label, context, length)
315 // ClientAuthType declares the policy the server will follow for
316 // TLS Client Authentication.
317 type ClientAuthType int
320 // NoClientCert indicates that no client certificate should be requested
321 // during the handshake, and if any certificates are sent they will not
323 NoClientCert ClientAuthType = iota
324 // RequestClientCert indicates that a client certificate should be requested
325 // during the handshake, but does not require that the client send any
328 // RequireAnyClientCert indicates that a client certificate should be requested
329 // during the handshake, and that at least one certificate is required to be
330 // sent by the client, but that certificate is not required to be valid.
332 // VerifyClientCertIfGiven indicates that a client certificate should be requested
333 // during the handshake, but does not require that the client sends a
334 // certificate. If the client does send a certificate it is required to be
336 VerifyClientCertIfGiven
337 // RequireAndVerifyClientCert indicates that a client certificate should be requested
338 // during the handshake, and that at least one valid certificate is required
339 // to be sent by the client.
340 RequireAndVerifyClientCert
343 // requiresClientCert reports whether the ClientAuthType requires a client
344 // certificate to be provided.
345 func requiresClientCert(c ClientAuthType) bool {
347 case RequireAnyClientCert, RequireAndVerifyClientCert:
354 // ClientSessionCache is a cache of ClientSessionState objects that can be used
355 // by a client to resume a TLS session with a given server. ClientSessionCache
356 // implementations should expect to be called concurrently from different
357 // goroutines. Up to TLS 1.2, only ticket-based resumption is supported, not
358 // SessionID-based resumption. In TLS 1.3 they were merged into PSK modes, which
359 // are supported via this interface.
360 type ClientSessionCache interface {
361 // Get searches for a ClientSessionState associated with the given key.
362 // On return, ok is true if one was found.
363 Get(sessionKey string) (session *ClientSessionState, ok bool)
365 // Put adds the ClientSessionState to the cache with the given key. It might
366 // get called multiple times in a connection if a TLS 1.3 server provides
367 // more than one session ticket. If called with a nil *ClientSessionState,
368 // it should remove the cache entry.
369 Put(sessionKey string, cs *ClientSessionState)
372 //go:generate stringer -type=SignatureScheme,CurveID,ClientAuthType -output=common_string.go
374 // SignatureScheme identifies a signature algorithm supported by TLS. See
375 // RFC 8446, Section 4.2.3.
376 type SignatureScheme uint16
379 // RSASSA-PKCS1-v1_5 algorithms.
380 PKCS1WithSHA256 SignatureScheme = 0x0401
381 PKCS1WithSHA384 SignatureScheme = 0x0501
382 PKCS1WithSHA512 SignatureScheme = 0x0601
384 // RSASSA-PSS algorithms with public key OID rsaEncryption.
385 PSSWithSHA256 SignatureScheme = 0x0804
386 PSSWithSHA384 SignatureScheme = 0x0805
387 PSSWithSHA512 SignatureScheme = 0x0806
389 // ECDSA algorithms. Only constrained to a specific curve in TLS 1.3.
390 ECDSAWithP256AndSHA256 SignatureScheme = 0x0403
391 ECDSAWithP384AndSHA384 SignatureScheme = 0x0503
392 ECDSAWithP521AndSHA512 SignatureScheme = 0x0603
395 Ed25519 SignatureScheme = 0x0807
397 // Legacy signature and hash algorithms for TLS 1.2.
398 PKCS1WithSHA1 SignatureScheme = 0x0201
399 ECDSAWithSHA1 SignatureScheme = 0x0203
402 // ClientHelloInfo contains information from a ClientHello message in order to
403 // guide application logic in the GetCertificate and GetConfigForClient callbacks.
404 type ClientHelloInfo struct {
405 // CipherSuites lists the CipherSuites supported by the client (e.g.
406 // TLS_AES_128_GCM_SHA256, TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256).
407 CipherSuites []uint16
409 // ServerName indicates the name of the server requested by the client
410 // in order to support virtual hosting. ServerName is only set if the
411 // client is using SNI (see RFC 4366, Section 3.1).
414 // SupportedCurves lists the elliptic curves supported by the client.
415 // SupportedCurves is set only if the Supported Elliptic Curves
416 // Extension is being used (see RFC 4492, Section 5.1.1).
417 SupportedCurves []CurveID
419 // SupportedPoints lists the point formats supported by the client.
420 // SupportedPoints is set only if the Supported Point Formats Extension
421 // is being used (see RFC 4492, Section 5.1.2).
422 SupportedPoints []uint8
424 // SignatureSchemes lists the signature and hash schemes that the client
425 // is willing to verify. SignatureSchemes is set only if the Signature
426 // Algorithms Extension is being used (see RFC 5246, Section 7.4.1.4.1).
427 SignatureSchemes []SignatureScheme
429 // SupportedProtos lists the application protocols supported by the client.
430 // SupportedProtos is set only if the Application-Layer Protocol
431 // Negotiation Extension is being used (see RFC 7301, Section 3.1).
433 // Servers can select a protocol by setting Config.NextProtos in a
434 // GetConfigForClient return value.
435 SupportedProtos []string
437 // SupportedVersions lists the TLS versions supported by the client.
438 // For TLS versions less than 1.3, this is extrapolated from the max
439 // version advertised by the client, so values other than the greatest
440 // might be rejected if used.
441 SupportedVersions []uint16
443 // Conn is the underlying net.Conn for the connection. Do not read
444 // from, or write to, this connection; that will cause the TLS
445 // connection to fail.
448 // config is embedded by the GetCertificate or GetConfigForClient caller,
449 // for use with SupportsCertificate.
452 // ctx is the context of the handshake that is in progress.
456 // Context returns the context of the handshake that is in progress.
457 // This context is a child of the context passed to HandshakeContext,
458 // if any, and is canceled when the handshake concludes.
459 func (c *ClientHelloInfo) Context() context.Context {
463 // CertificateRequestInfo contains information from a server's
464 // CertificateRequest message, which is used to demand a certificate and proof
465 // of control from a client.
466 type CertificateRequestInfo struct {
467 // AcceptableCAs contains zero or more, DER-encoded, X.501
468 // Distinguished Names. These are the names of root or intermediate CAs
469 // that the server wishes the returned certificate to be signed by. An
470 // empty slice indicates that the server has no preference.
471 AcceptableCAs [][]byte
473 // SignatureSchemes lists the signature schemes that the server is
474 // willing to verify.
475 SignatureSchemes []SignatureScheme
477 // Version is the TLS version that was negotiated for this connection.
480 // ctx is the context of the handshake that is in progress.
484 // Context returns the context of the handshake that is in progress.
485 // This context is a child of the context passed to HandshakeContext,
486 // if any, and is canceled when the handshake concludes.
487 func (c *CertificateRequestInfo) Context() context.Context {
491 // RenegotiationSupport enumerates the different levels of support for TLS
492 // renegotiation. TLS renegotiation is the act of performing subsequent
493 // handshakes on a connection after the first. This significantly complicates
494 // the state machine and has been the source of numerous, subtle security
495 // issues. Initiating a renegotiation is not supported, but support for
496 // accepting renegotiation requests may be enabled.
498 // Even when enabled, the server may not change its identity between handshakes
499 // (i.e. the leaf certificate must be the same). Additionally, concurrent
500 // handshake and application data flow is not permitted so renegotiation can
501 // only be used with protocols that synchronise with the renegotiation, such as
504 // Renegotiation is not defined in TLS 1.3.
505 type RenegotiationSupport int
508 // RenegotiateNever disables renegotiation.
509 RenegotiateNever RenegotiationSupport = iota
511 // RenegotiateOnceAsClient allows a remote server to request
512 // renegotiation once per connection.
513 RenegotiateOnceAsClient
515 // RenegotiateFreelyAsClient allows a remote server to repeatedly
516 // request renegotiation.
517 RenegotiateFreelyAsClient
520 // A Config structure is used to configure a TLS client or server.
521 // After one has been passed to a TLS function it must not be
522 // modified. A Config may be reused; the tls package will also not
525 // Rand provides the source of entropy for nonces and RSA blinding.
526 // If Rand is nil, TLS uses the cryptographic random reader in package
528 // The Reader must be safe for use by multiple goroutines.
531 // Time returns the current time as the number of seconds since the epoch.
532 // If Time is nil, TLS uses time.Now.
533 Time func() time.Time
535 // Certificates contains one or more certificate chains to present to the
536 // other side of the connection. The first certificate compatible with the
537 // peer's requirements is selected automatically.
539 // Server configurations must set one of Certificates, GetCertificate or
540 // GetConfigForClient. Clients doing client-authentication may set either
541 // Certificates or GetClientCertificate.
543 // Note: if there are multiple Certificates, and they don't have the
544 // optional field Leaf set, certificate selection will incur a significant
545 // per-handshake performance cost.
546 Certificates []Certificate
548 // NameToCertificate maps from a certificate name to an element of
549 // Certificates. Note that a certificate name can be of the form
550 // '*.example.com' and so doesn't have to be a domain name as such.
552 // Deprecated: NameToCertificate only allows associating a single
553 // certificate with a given name. Leave this field nil to let the library
554 // select the first compatible chain from Certificates.
555 NameToCertificate map[string]*Certificate
557 // GetCertificate returns a Certificate based on the given
558 // ClientHelloInfo. It will only be called if the client supplies SNI
559 // information or if Certificates is empty.
561 // If GetCertificate is nil or returns nil, then the certificate is
562 // retrieved from NameToCertificate. If NameToCertificate is nil, the
563 // best element of Certificates will be used.
565 // Once a Certificate is returned it should not be modified.
566 GetCertificate func(*ClientHelloInfo) (*Certificate, error)
568 // GetClientCertificate, if not nil, is called when a server requests a
569 // certificate from a client. If set, the contents of Certificates will
572 // If GetClientCertificate returns an error, the handshake will be
573 // aborted and that error will be returned. Otherwise
574 // GetClientCertificate must return a non-nil Certificate. If
575 // Certificate.Certificate is empty then no certificate will be sent to
576 // the server. If this is unacceptable to the server then it may abort
579 // GetClientCertificate may be called multiple times for the same
580 // connection if renegotiation occurs or if TLS 1.3 is in use.
582 // Once a Certificate is returned it should not be modified.
583 GetClientCertificate func(*CertificateRequestInfo) (*Certificate, error)
585 // GetConfigForClient, if not nil, is called after a ClientHello is
586 // received from a client. It may return a non-nil Config in order to
587 // change the Config that will be used to handle this connection. If
588 // the returned Config is nil, the original Config will be used. The
589 // Config returned by this callback may not be subsequently modified.
591 // If GetConfigForClient is nil, the Config passed to Server() will be
592 // used for all connections.
594 // If SessionTicketKey was explicitly set on the returned Config, or if
595 // SetSessionTicketKeys was called on the returned Config, those keys will
596 // be used. Otherwise, the original Config keys will be used (and possibly
597 // rotated if they are automatically managed).
598 GetConfigForClient func(*ClientHelloInfo) (*Config, error)
600 // VerifyPeerCertificate, if not nil, is called after normal
601 // certificate verification by either a TLS client or server. It
602 // receives the raw ASN.1 certificates provided by the peer and also
603 // any verified chains that normal processing found. If it returns a
604 // non-nil error, the handshake is aborted and that error results.
606 // If normal verification fails then the handshake will abort before
607 // considering this callback. If normal verification is disabled (on the
608 // client when InsecureSkipVerify is set, or on a server when ClientAuth is
609 // RequestClientCert or RequireAnyClientCert), then this callback will be
610 // considered but the verifiedChains argument will always be nil. When
611 // ClientAuth is NoClientCert, this callback is not called on the server.
612 // rawCerts may be empty on the server if ClientAuth is RequestClientCert or
613 // VerifyClientCertIfGiven.
615 // This callback is not invoked on resumed connections, as certificates are
616 // not re-verified on resumption.
618 // verifiedChains and its contents should not be modified.
619 VerifyPeerCertificate func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error
621 // VerifyConnection, if not nil, is called after normal certificate
622 // verification and after VerifyPeerCertificate by either a TLS client
623 // or server. If it returns a non-nil error, the handshake is aborted
624 // and that error results.
626 // If normal verification fails then the handshake will abort before
627 // considering this callback. This callback will run for all connections,
628 // including resumptions, regardless of InsecureSkipVerify or ClientAuth
630 VerifyConnection func(ConnectionState) error
632 // RootCAs defines the set of root certificate authorities
633 // that clients use when verifying server certificates.
634 // If RootCAs is nil, TLS uses the host's root CA set.
635 RootCAs *x509.CertPool
637 // NextProtos is a list of supported application level protocols, in
638 // order of preference. If both peers support ALPN, the selected
639 // protocol will be one from this list, and the connection will fail
640 // if there is no mutually supported protocol. If NextProtos is empty
641 // or the peer doesn't support ALPN, the connection will succeed and
642 // ConnectionState.NegotiatedProtocol will be empty.
645 // ServerName is used to verify the hostname on the returned
646 // certificates unless InsecureSkipVerify is given. It is also included
647 // in the client's handshake to support virtual hosting unless it is
651 // ClientAuth determines the server's policy for
652 // TLS Client Authentication. The default is NoClientCert.
653 ClientAuth ClientAuthType
655 // ClientCAs defines the set of root certificate authorities
656 // that servers use if required to verify a client certificate
657 // by the policy in ClientAuth.
658 ClientCAs *x509.CertPool
660 // InsecureSkipVerify controls whether a client verifies the server's
661 // certificate chain and host name. If InsecureSkipVerify is true, crypto/tls
662 // accepts any certificate presented by the server and any host name in that
663 // certificate. In this mode, TLS is susceptible to machine-in-the-middle
664 // attacks unless custom verification is used. This should be used only for
665 // testing or in combination with VerifyConnection or VerifyPeerCertificate.
666 InsecureSkipVerify bool
668 // CipherSuites is a list of enabled TLS 1.0–1.2 cipher suites. The order of
669 // the list is ignored. Note that TLS 1.3 ciphersuites are not configurable.
671 // If CipherSuites is nil, a safe default list is used. The default cipher
672 // suites might change over time.
673 CipherSuites []uint16
675 // PreferServerCipherSuites is a legacy field and has no effect.
677 // It used to control whether the server would follow the client's or the
678 // server's preference. Servers now select the best mutually supported
679 // cipher suite based on logic that takes into account inferred client
680 // hardware, server hardware, and security.
682 // Deprecated: PreferServerCipherSuites is ignored.
683 PreferServerCipherSuites bool
685 // SessionTicketsDisabled may be set to true to disable session ticket and
686 // PSK (resumption) support. Note that on clients, session ticket support is
687 // also disabled if ClientSessionCache is nil.
688 SessionTicketsDisabled bool
690 // SessionTicketKey is used by TLS servers to provide session resumption.
691 // See RFC 5077 and the PSK mode of RFC 8446. If zero, it will be filled
692 // with random data before the first server handshake.
694 // Deprecated: if this field is left at zero, session ticket keys will be
695 // automatically rotated every day and dropped after seven days. For
696 // customizing the rotation schedule or synchronizing servers that are
697 // terminating connections for the same host, use SetSessionTicketKeys.
698 SessionTicketKey [32]byte
700 // ClientSessionCache is a cache of ClientSessionState entries for TLS
701 // session resumption. It is only used by clients.
702 ClientSessionCache ClientSessionCache
704 // UnwrapSession is called on the server to turn a ticket/identity
705 // previously produced by [WrapSession] into a usable session.
707 // UnwrapSession will usually either decrypt a session state in the ticket
708 // (for example with [Config.EncryptTicket]), or use the ticket as a handle
709 // to recover a previously stored state. It must use [ParseSessionState] to
710 // deserialize the session state.
712 // If UnwrapSession returns an error, the connection is terminated. If it
713 // returns (nil, nil), the session is ignored. crypto/tls may still choose
714 // not to resume the returned session.
715 UnwrapSession func(identity []byte, cs ConnectionState) (*SessionState, error)
717 // WrapSession is called on the server to produce a session ticket/identity.
719 // WrapSession must serialize the session state with [SessionState.Bytes].
720 // It may then encrypt the serialized state (for example with
721 // [Config.DecryptTicket]) and use it as the ticket, or store the state and
722 // return a handle for it.
724 // If WrapSession returns an error, the connection is terminated.
726 // Warning: the return value will be exposed on the wire and to clients in
727 // plaintext. The application is in charge of encrypting and authenticating
728 // it (and rotating keys) or returning high-entropy identifiers. Failing to
729 // do so correctly can compromise current, previous, and future connections
730 // depending on the protocol version.
731 WrapSession func(ConnectionState, *SessionState) ([]byte, error)
733 // MinVersion contains the minimum TLS version that is acceptable.
735 // By default, TLS 1.2 is currently used as the minimum when acting as a
736 // client, and TLS 1.0 when acting as a server. TLS 1.0 is the minimum
737 // supported by this package, both as a client and as a server.
739 // The client-side default can temporarily be reverted to TLS 1.0 by
740 // including the value "x509sha1=1" in the GODEBUG environment variable.
741 // Note that this option will be removed in Go 1.19 (but it will still be
742 // possible to set this field to VersionTLS10 explicitly).
745 // MaxVersion contains the maximum TLS version that is acceptable.
747 // By default, the maximum version supported by this package is used,
748 // which is currently TLS 1.3.
751 // CurvePreferences contains the elliptic curves that will be used in
752 // an ECDHE handshake, in preference order. If empty, the default will
753 // be used. The client will use the first preference as the type for
754 // its key share in TLS 1.3. This may change in the future.
755 CurvePreferences []CurveID
757 // DynamicRecordSizingDisabled disables adaptive sizing of TLS records.
758 // When true, the largest possible TLS record size is always used. When
759 // false, the size of TLS records may be adjusted in an attempt to
761 DynamicRecordSizingDisabled bool
763 // Renegotiation controls what types of renegotiation are supported.
764 // The default, none, is correct for the vast majority of applications.
765 Renegotiation RenegotiationSupport
767 // KeyLogWriter optionally specifies a destination for TLS master secrets
768 // in NSS key log format that can be used to allow external programs
769 // such as Wireshark to decrypt TLS connections.
770 // See https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/Key_Log_Format.
771 // Use of KeyLogWriter compromises security and should only be
772 // used for debugging.
773 KeyLogWriter io.Writer
775 // mutex protects sessionTicketKeys and autoSessionTicketKeys.
777 // sessionTicketKeys contains zero or more ticket keys. If set, it means
778 // the keys were set with SessionTicketKey or SetSessionTicketKeys. The
779 // first key is used for new tickets and any subsequent keys can be used to
780 // decrypt old tickets. The slice contents are not protected by the mutex
781 // and are immutable.
782 sessionTicketKeys []ticketKey
783 // autoSessionTicketKeys is like sessionTicketKeys but is owned by the
784 // auto-rotation logic. See Config.ticketKeys.
785 autoSessionTicketKeys []ticketKey
789 // ticketKeyLifetime is how long a ticket key remains valid and can be used to
790 // resume a client connection.
791 ticketKeyLifetime = 7 * 24 * time.Hour // 7 days
793 // ticketKeyRotation is how often the server should rotate the session ticket key
794 // that is used for new tickets.
795 ticketKeyRotation = 24 * time.Hour
798 // ticketKey is the internal representation of a session ticket key.
799 type ticketKey struct {
802 // created is the time at which this ticket key was created. See Config.ticketKeys.
806 // ticketKeyFromBytes converts from the external representation of a session
807 // ticket key to a ticketKey. Externally, session ticket keys are 32 random
808 // bytes and this function expands that into sufficient name and key material.
809 func (c *Config) ticketKeyFromBytes(b [32]byte) (key ticketKey) {
810 hashed := sha512.Sum512(b[:])
811 // The first 16 bytes of the hash used to be exposed on the wire as a ticket
812 // prefix. They MUST NOT be used as a secret. In the future, it would make
813 // sense to use a proper KDF here, like HKDF with a fixed salt.
814 const legacyTicketKeyNameLen = 16
815 copy(key.aesKey[:], hashed[legacyTicketKeyNameLen:])
816 copy(key.hmacKey[:], hashed[legacyTicketKeyNameLen+len(key.aesKey):])
817 key.created = c.time()
821 // maxSessionTicketLifetime is the maximum allowed lifetime of a TLS 1.3 session
822 // ticket, and the lifetime we set for all tickets we send.
823 const maxSessionTicketLifetime = 7 * 24 * time.Hour
825 // Clone returns a shallow clone of c or nil if c is nil. It is safe to clone a [Config] that is
826 // being used concurrently by a TLS client or server.
827 func (c *Config) Clone() *Config {
832 defer c.mutex.RUnlock()
836 Certificates: c.Certificates,
837 NameToCertificate: c.NameToCertificate,
838 GetCertificate: c.GetCertificate,
839 GetClientCertificate: c.GetClientCertificate,
840 GetConfigForClient: c.GetConfigForClient,
841 VerifyPeerCertificate: c.VerifyPeerCertificate,
842 VerifyConnection: c.VerifyConnection,
844 NextProtos: c.NextProtos,
845 ServerName: c.ServerName,
846 ClientAuth: c.ClientAuth,
847 ClientCAs: c.ClientCAs,
848 InsecureSkipVerify: c.InsecureSkipVerify,
849 CipherSuites: c.CipherSuites,
850 PreferServerCipherSuites: c.PreferServerCipherSuites,
851 SessionTicketsDisabled: c.SessionTicketsDisabled,
852 SessionTicketKey: c.SessionTicketKey,
853 ClientSessionCache: c.ClientSessionCache,
854 UnwrapSession: c.UnwrapSession,
855 WrapSession: c.WrapSession,
856 MinVersion: c.MinVersion,
857 MaxVersion: c.MaxVersion,
858 CurvePreferences: c.CurvePreferences,
859 DynamicRecordSizingDisabled: c.DynamicRecordSizingDisabled,
860 Renegotiation: c.Renegotiation,
861 KeyLogWriter: c.KeyLogWriter,
862 sessionTicketKeys: c.sessionTicketKeys,
863 autoSessionTicketKeys: c.autoSessionTicketKeys,
867 // deprecatedSessionTicketKey is set as the prefix of SessionTicketKey if it was
868 // randomized for backwards compatibility but is not in use.
869 var deprecatedSessionTicketKey = []byte("DEPRECATED")
871 // initLegacySessionTicketKeyRLocked ensures the legacy SessionTicketKey field is
872 // randomized if empty, and that sessionTicketKeys is populated from it otherwise.
873 func (c *Config) initLegacySessionTicketKeyRLocked() {
874 // Don't write if SessionTicketKey is already defined as our deprecated string,
875 // or if it is defined by the user but sessionTicketKeys is already set.
876 if c.SessionTicketKey != [32]byte{} &&
877 (bytes.HasPrefix(c.SessionTicketKey[:], deprecatedSessionTicketKey) || len(c.sessionTicketKeys) > 0) {
881 // We need to write some data, so get an exclusive lock and re-check any conditions.
883 defer c.mutex.RLock()
885 defer c.mutex.Unlock()
886 if c.SessionTicketKey == [32]byte{} {
887 if _, err := io.ReadFull(c.rand(), c.SessionTicketKey[:]); err != nil {
888 panic(fmt.Sprintf("tls: unable to generate random session ticket key: %v", err))
890 // Write the deprecated prefix at the beginning so we know we created
891 // it. This key with the DEPRECATED prefix isn't used as an actual
892 // session ticket key, and is only randomized in case the application
893 // reuses it for some reason.
894 copy(c.SessionTicketKey[:], deprecatedSessionTicketKey)
895 } else if !bytes.HasPrefix(c.SessionTicketKey[:], deprecatedSessionTicketKey) && len(c.sessionTicketKeys) == 0 {
896 c.sessionTicketKeys = []ticketKey{c.ticketKeyFromBytes(c.SessionTicketKey)}
901 // ticketKeys returns the ticketKeys for this connection.
902 // If configForClient has explicitly set keys, those will
903 // be returned. Otherwise, the keys on c will be used and
904 // may be rotated if auto-managed.
905 // During rotation, any expired session ticket keys are deleted from
906 // c.sessionTicketKeys. If the session ticket key that is currently
907 // encrypting tickets (ie. the first ticketKey in c.sessionTicketKeys)
908 // is not fresh, then a new session ticket key will be
909 // created and prepended to c.sessionTicketKeys.
910 func (c *Config) ticketKeys(configForClient *Config) []ticketKey {
911 // If the ConfigForClient callback returned a Config with explicitly set
912 // keys, use those, otherwise just use the original Config.
913 if configForClient != nil {
914 configForClient.mutex.RLock()
915 if configForClient.SessionTicketsDisabled {
918 configForClient.initLegacySessionTicketKeyRLocked()
919 if len(configForClient.sessionTicketKeys) != 0 {
920 ret := configForClient.sessionTicketKeys
921 configForClient.mutex.RUnlock()
924 configForClient.mutex.RUnlock()
928 defer c.mutex.RUnlock()
929 if c.SessionTicketsDisabled {
932 c.initLegacySessionTicketKeyRLocked()
933 if len(c.sessionTicketKeys) != 0 {
934 return c.sessionTicketKeys
936 // Fast path for the common case where the key is fresh enough.
937 if len(c.autoSessionTicketKeys) > 0 && c.time().Sub(c.autoSessionTicketKeys[0].created) < ticketKeyRotation {
938 return c.autoSessionTicketKeys
941 // autoSessionTicketKeys are managed by auto-rotation.
943 defer c.mutex.RLock()
945 defer c.mutex.Unlock()
946 // Re-check the condition in case it changed since obtaining the new lock.
947 if len(c.autoSessionTicketKeys) == 0 || c.time().Sub(c.autoSessionTicketKeys[0].created) >= ticketKeyRotation {
949 if _, err := io.ReadFull(c.rand(), newKey[:]); err != nil {
950 panic(fmt.Sprintf("unable to generate random session ticket key: %v", err))
952 valid := make([]ticketKey, 0, len(c.autoSessionTicketKeys)+1)
953 valid = append(valid, c.ticketKeyFromBytes(newKey))
954 for _, k := range c.autoSessionTicketKeys {
955 // While rotating the current key, also remove any expired ones.
956 if c.time().Sub(k.created) < ticketKeyLifetime {
957 valid = append(valid, k)
960 c.autoSessionTicketKeys = valid
962 return c.autoSessionTicketKeys
965 // SetSessionTicketKeys updates the session ticket keys for a server.
967 // The first key will be used when creating new tickets, while all keys can be
968 // used for decrypting tickets. It is safe to call this function while the
969 // server is running in order to rotate the session ticket keys. The function
970 // will panic if keys is empty.
972 // Calling this function will turn off automatic session ticket key rotation.
974 // If multiple servers are terminating connections for the same host they should
975 // all have the same session ticket keys. If the session ticket keys leaks,
976 // previously recorded and future TLS connections using those keys might be
978 func (c *Config) SetSessionTicketKeys(keys [][32]byte) {
980 panic("tls: keys must have at least one key")
983 newKeys := make([]ticketKey, len(keys))
984 for i, bytes := range keys {
985 newKeys[i] = c.ticketKeyFromBytes(bytes)
989 c.sessionTicketKeys = newKeys
993 func (c *Config) rand() io.Reader {
1001 func (c *Config) time() time.Time {
1009 func (c *Config) cipherSuites() []uint16 {
1011 return fipsCipherSuites(c)
1013 if c.CipherSuites != nil {
1014 return c.CipherSuites
1016 return defaultCipherSuites
1019 var supportedVersions = []uint16{
1026 // roleClient and roleServer are meant to call supportedVersions and parents
1027 // with more readability at the callsite.
1028 const roleClient = true
1029 const roleServer = false
1031 func (c *Config) supportedVersions(isClient bool) []uint16 {
1032 versions := make([]uint16, 0, len(supportedVersions))
1033 for _, v := range supportedVersions {
1034 if needFIPS() && (v < fipsMinVersion(c) || v > fipsMaxVersion(c)) {
1037 if (c == nil || c.MinVersion == 0) &&
1038 isClient && v < VersionTLS12 {
1041 if c != nil && c.MinVersion != 0 && v < c.MinVersion {
1044 if c != nil && c.MaxVersion != 0 && v > c.MaxVersion {
1047 versions = append(versions, v)
1052 func (c *Config) maxSupportedVersion(isClient bool) uint16 {
1053 supportedVersions := c.supportedVersions(isClient)
1054 if len(supportedVersions) == 0 {
1057 return supportedVersions[0]
1060 // supportedVersionsFromMax returns a list of supported versions derived from a
1061 // legacy maximum version value. Note that only versions supported by this
1062 // library are returned. Any newer peer will use supportedVersions anyway.
1063 func supportedVersionsFromMax(maxVersion uint16) []uint16 {
1064 versions := make([]uint16, 0, len(supportedVersions))
1065 for _, v := range supportedVersions {
1069 versions = append(versions, v)
1074 var defaultCurvePreferences = []CurveID{X25519, CurveP256, CurveP384, CurveP521}
1076 func (c *Config) curvePreferences() []CurveID {
1078 return fipsCurvePreferences(c)
1080 if c == nil || len(c.CurvePreferences) == 0 {
1081 return defaultCurvePreferences
1083 return c.CurvePreferences
1086 func (c *Config) supportsCurve(curve CurveID) bool {
1087 for _, cc := range c.curvePreferences() {
1095 // mutualVersion returns the protocol version to use given the advertised
1096 // versions of the peer. Priority is given to the peer preference order.
1097 func (c *Config) mutualVersion(isClient bool, peerVersions []uint16) (uint16, bool) {
1098 supportedVersions := c.supportedVersions(isClient)
1099 for _, peerVersion := range peerVersions {
1100 for _, v := range supportedVersions {
1101 if v == peerVersion {
1109 var errNoCertificates = errors.New("tls: no certificates configured")
1111 // getCertificate returns the best certificate for the given ClientHelloInfo,
1112 // defaulting to the first element of c.Certificates.
1113 func (c *Config) getCertificate(clientHello *ClientHelloInfo) (*Certificate, error) {
1114 if c.GetCertificate != nil &&
1115 (len(c.Certificates) == 0 || len(clientHello.ServerName) > 0) {
1116 cert, err := c.GetCertificate(clientHello)
1117 if cert != nil || err != nil {
1122 if len(c.Certificates) == 0 {
1123 return nil, errNoCertificates
1126 if len(c.Certificates) == 1 {
1127 // There's only one choice, so no point doing any work.
1128 return &c.Certificates[0], nil
1131 if c.NameToCertificate != nil {
1132 name := strings.ToLower(clientHello.ServerName)
1133 if cert, ok := c.NameToCertificate[name]; ok {
1137 labels := strings.Split(name, ".")
1139 wildcardName := strings.Join(labels, ".")
1140 if cert, ok := c.NameToCertificate[wildcardName]; ok {
1146 for _, cert := range c.Certificates {
1147 if err := clientHello.SupportsCertificate(&cert); err == nil {
1152 // If nothing matches, return the first certificate.
1153 return &c.Certificates[0], nil
1156 // SupportsCertificate returns nil if the provided certificate is supported by
1157 // the client that sent the ClientHello. Otherwise, it returns an error
1158 // describing the reason for the incompatibility.
1160 // If this [ClientHelloInfo] was passed to a GetConfigForClient or GetCertificate
1161 // callback, this method will take into account the associated [Config]. Note that
1162 // if GetConfigForClient returns a different [Config], the change can't be
1163 // accounted for by this method.
1165 // This function will call x509.ParseCertificate unless c.Leaf is set, which can
1166 // incur a significant performance cost.
1167 func (chi *ClientHelloInfo) SupportsCertificate(c *Certificate) error {
1168 // Note we don't currently support certificate_authorities nor
1169 // signature_algorithms_cert, and don't check the algorithms of the
1170 // signatures on the chain (which anyway are a SHOULD, see RFC 8446,
1171 // Section 4.4.2.2).
1173 config := chi.config
1177 vers, ok := config.mutualVersion(roleServer, chi.SupportedVersions)
1179 return errors.New("no mutually supported protocol versions")
1182 // If the client specified the name they are trying to connect to, the
1183 // certificate needs to be valid for it.
1184 if chi.ServerName != "" {
1185 x509Cert, err := c.leaf()
1187 return fmt.Errorf("failed to parse certificate: %w", err)
1189 if err := x509Cert.VerifyHostname(chi.ServerName); err != nil {
1190 return fmt.Errorf("certificate is not valid for requested server name: %w", err)
1194 // supportsRSAFallback returns nil if the certificate and connection support
1195 // the static RSA key exchange, and unsupported otherwise. The logic for
1196 // supporting static RSA is completely disjoint from the logic for
1197 // supporting signed key exchanges, so we just check it as a fallback.
1198 supportsRSAFallback := func(unsupported error) error {
1199 // TLS 1.3 dropped support for the static RSA key exchange.
1200 if vers == VersionTLS13 {
1203 // The static RSA key exchange works by decrypting a challenge with the
1204 // RSA private key, not by signing, so check the PrivateKey implements
1205 // crypto.Decrypter, like *rsa.PrivateKey does.
1206 if priv, ok := c.PrivateKey.(crypto.Decrypter); ok {
1207 if _, ok := priv.Public().(*rsa.PublicKey); !ok {
1213 // Finally, there needs to be a mutual cipher suite that uses the static
1214 // RSA key exchange instead of ECDHE.
1215 rsaCipherSuite := selectCipherSuite(chi.CipherSuites, config.cipherSuites(), func(c *cipherSuite) bool {
1216 if c.flags&suiteECDHE != 0 {
1219 if vers < VersionTLS12 && c.flags&suiteTLS12 != 0 {
1224 if rsaCipherSuite == nil {
1230 // If the client sent the signature_algorithms extension, ensure it supports
1231 // schemes we can use with this certificate and TLS version.
1232 if len(chi.SignatureSchemes) > 0 {
1233 if _, err := selectSignatureScheme(vers, c, chi.SignatureSchemes); err != nil {
1234 return supportsRSAFallback(err)
1238 // In TLS 1.3 we are done because supported_groups is only relevant to the
1239 // ECDHE computation, point format negotiation is removed, cipher suites are
1240 // only relevant to the AEAD choice, and static RSA does not exist.
1241 if vers == VersionTLS13 {
1245 // The only signed key exchange we support is ECDHE.
1246 if !supportsECDHE(config, chi.SupportedCurves, chi.SupportedPoints) {
1247 return supportsRSAFallback(errors.New("client doesn't support ECDHE, can only use legacy RSA key exchange"))
1250 var ecdsaCipherSuite bool
1251 if priv, ok := c.PrivateKey.(crypto.Signer); ok {
1252 switch pub := priv.Public().(type) {
1253 case *ecdsa.PublicKey:
1256 case elliptic.P256():
1258 case elliptic.P384():
1260 case elliptic.P521():
1263 return supportsRSAFallback(unsupportedCertificateError(c))
1266 for _, c := range chi.SupportedCurves {
1267 if c == curve && config.supportsCurve(c) {
1273 return errors.New("client doesn't support certificate curve")
1275 ecdsaCipherSuite = true
1276 case ed25519.PublicKey:
1277 if vers < VersionTLS12 || len(chi.SignatureSchemes) == 0 {
1278 return errors.New("connection doesn't support Ed25519")
1280 ecdsaCipherSuite = true
1281 case *rsa.PublicKey:
1283 return supportsRSAFallback(unsupportedCertificateError(c))
1286 return supportsRSAFallback(unsupportedCertificateError(c))
1289 // Make sure that there is a mutually supported cipher suite that works with
1290 // this certificate. Cipher suite selection will then apply the logic in
1291 // reverse to pick it. See also serverHandshakeState.cipherSuiteOk.
1292 cipherSuite := selectCipherSuite(chi.CipherSuites, config.cipherSuites(), func(c *cipherSuite) bool {
1293 if c.flags&suiteECDHE == 0 {
1296 if c.flags&suiteECSign != 0 {
1297 if !ecdsaCipherSuite {
1301 if ecdsaCipherSuite {
1305 if vers < VersionTLS12 && c.flags&suiteTLS12 != 0 {
1310 if cipherSuite == nil {
1311 return supportsRSAFallback(errors.New("client doesn't support any cipher suites compatible with the certificate"))
1317 // SupportsCertificate returns nil if the provided certificate is supported by
1318 // the server that sent the CertificateRequest. Otherwise, it returns an error
1319 // describing the reason for the incompatibility.
1320 func (cri *CertificateRequestInfo) SupportsCertificate(c *Certificate) error {
1321 if _, err := selectSignatureScheme(cri.Version, c, cri.SignatureSchemes); err != nil {
1325 if len(cri.AcceptableCAs) == 0 {
1329 for j, cert := range c.Certificate {
1331 // Parse the certificate if this isn't the leaf node, or if
1332 // chain.Leaf was nil.
1333 if j != 0 || x509Cert == nil {
1335 if x509Cert, err = x509.ParseCertificate(cert); err != nil {
1336 return fmt.Errorf("failed to parse certificate #%d in the chain: %w", j, err)
1340 for _, ca := range cri.AcceptableCAs {
1341 if bytes.Equal(x509Cert.RawIssuer, ca) {
1346 return errors.New("chain is not signed by an acceptable CA")
1349 // BuildNameToCertificate parses c.Certificates and builds c.NameToCertificate
1350 // from the CommonName and SubjectAlternateName fields of each of the leaf
1353 // Deprecated: NameToCertificate only allows associating a single certificate
1354 // with a given name. Leave that field nil to let the library select the first
1355 // compatible chain from Certificates.
1356 func (c *Config) BuildNameToCertificate() {
1357 c.NameToCertificate = make(map[string]*Certificate)
1358 for i := range c.Certificates {
1359 cert := &c.Certificates[i]
1360 x509Cert, err := cert.leaf()
1364 // If SANs are *not* present, some clients will consider the certificate
1365 // valid for the name in the Common Name.
1366 if x509Cert.Subject.CommonName != "" && len(x509Cert.DNSNames) == 0 {
1367 c.NameToCertificate[x509Cert.Subject.CommonName] = cert
1369 for _, san := range x509Cert.DNSNames {
1370 c.NameToCertificate[san] = cert
1376 keyLogLabelTLS12 = "CLIENT_RANDOM"
1377 keyLogLabelClientHandshake = "CLIENT_HANDSHAKE_TRAFFIC_SECRET"
1378 keyLogLabelServerHandshake = "SERVER_HANDSHAKE_TRAFFIC_SECRET"
1379 keyLogLabelClientTraffic = "CLIENT_TRAFFIC_SECRET_0"
1380 keyLogLabelServerTraffic = "SERVER_TRAFFIC_SECRET_0"
1383 func (c *Config) writeKeyLog(label string, clientRandom, secret []byte) error {
1384 if c.KeyLogWriter == nil {
1388 logLine := fmt.Appendf(nil, "%s %x %x\n", label, clientRandom, secret)
1391 _, err := c.KeyLogWriter.Write(logLine)
1392 writerMutex.Unlock()
1397 // writerMutex protects all KeyLogWriters globally. It is rarely enabled,
1398 // and is only for debugging, so a global mutex saves space.
1399 var writerMutex sync.Mutex
1401 // A Certificate is a chain of one or more certificates, leaf first.
1402 type Certificate struct {
1403 Certificate [][]byte
1404 // PrivateKey contains the private key corresponding to the public key in
1405 // Leaf. This must implement crypto.Signer with an RSA, ECDSA or Ed25519 PublicKey.
1406 // For a server up to TLS 1.2, it can also implement crypto.Decrypter with
1407 // an RSA PublicKey.
1408 PrivateKey crypto.PrivateKey
1409 // SupportedSignatureAlgorithms is an optional list restricting what
1410 // signature algorithms the PrivateKey can be used for.
1411 SupportedSignatureAlgorithms []SignatureScheme
1412 // OCSPStaple contains an optional OCSP response which will be served
1413 // to clients that request it.
1415 // SignedCertificateTimestamps contains an optional list of Signed
1416 // Certificate Timestamps which will be served to clients that request it.
1417 SignedCertificateTimestamps [][]byte
1418 // Leaf is the parsed form of the leaf certificate, which may be initialized
1419 // using x509.ParseCertificate to reduce per-handshake processing. If nil,
1420 // the leaf certificate will be parsed as needed.
1421 Leaf *x509.Certificate
1424 // leaf returns the parsed leaf certificate, either from c.Leaf or by parsing
1425 // the corresponding c.Certificate[0].
1426 func (c *Certificate) leaf() (*x509.Certificate, error) {
1430 return x509.ParseCertificate(c.Certificate[0])
1433 type handshakeMessage interface {
1434 marshal() ([]byte, error)
1435 unmarshal([]byte) bool
1438 // lruSessionCache is a ClientSessionCache implementation that uses an LRU
1439 // caching strategy.
1440 type lruSessionCache struct {
1443 m map[string]*list.Element
1448 type lruSessionCacheEntry struct {
1450 state *ClientSessionState
1453 // NewLRUClientSessionCache returns a [ClientSessionCache] with the given
1454 // capacity that uses an LRU strategy. If capacity is < 1, a default capacity
1456 func NewLRUClientSessionCache(capacity int) ClientSessionCache {
1457 const defaultSessionCacheCapacity = 64
1460 capacity = defaultSessionCacheCapacity
1462 return &lruSessionCache{
1463 m: make(map[string]*list.Element),
1469 // Put adds the provided (sessionKey, cs) pair to the cache. If cs is nil, the entry
1470 // corresponding to sessionKey is removed from the cache instead.
1471 func (c *lruSessionCache) Put(sessionKey string, cs *ClientSessionState) {
1475 if elem, ok := c.m[sessionKey]; ok {
1478 delete(c.m, sessionKey)
1480 entry := elem.Value.(*lruSessionCacheEntry)
1482 c.q.MoveToFront(elem)
1487 if c.q.Len() < c.capacity {
1488 entry := &lruSessionCacheEntry{sessionKey, cs}
1489 c.m[sessionKey] = c.q.PushFront(entry)
1494 entry := elem.Value.(*lruSessionCacheEntry)
1495 delete(c.m, entry.sessionKey)
1496 entry.sessionKey = sessionKey
1498 c.q.MoveToFront(elem)
1499 c.m[sessionKey] = elem
1502 // Get returns the [ClientSessionState] value associated with a given key. It
1503 // returns (nil, false) if no value is found.
1504 func (c *lruSessionCache) Get(sessionKey string) (*ClientSessionState, bool) {
1508 if elem, ok := c.m[sessionKey]; ok {
1509 c.q.MoveToFront(elem)
1510 return elem.Value.(*lruSessionCacheEntry).state, true
1515 var emptyConfig Config
1517 func defaultConfig() *Config {
1521 func unexpectedMessageError(wanted, got any) error {
1522 return fmt.Errorf("tls: received unexpected handshake message of type %T when waiting for %T", got, wanted)
1525 func isSupportedSignatureAlgorithm(sigAlg SignatureScheme, supportedSignatureAlgorithms []SignatureScheme) bool {
1526 for _, s := range supportedSignatureAlgorithms {
1534 // CertificateVerificationError is returned when certificate verification fails during the handshake.
1535 type CertificateVerificationError struct {
1536 // UnverifiedCertificates and its contents should not be modified.
1537 UnverifiedCertificates []*x509.Certificate
1541 func (e *CertificateVerificationError) Error() string {
1542 return fmt.Sprintf("tls: failed to verify certificate: %s", e.Err)
1545 func (e *CertificateVerificationError) Unwrap() error {