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Diffstat (limited to 'src/crypto/tls/common.go')
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diff --git a/src/crypto/tls/common.go b/src/crypto/tls/common.go new file mode 100644 index 0000000..e6e7598 --- /dev/null +++ b/src/crypto/tls/common.go @@ -0,0 +1,1480 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package tls + +import ( + "bytes" + "container/list" + "context" + "crypto" + "crypto/ecdsa" + "crypto/ed25519" + "crypto/elliptic" + "crypto/rand" + "crypto/rsa" + "crypto/sha512" + "crypto/x509" + "errors" + "fmt" + "internal/godebug" + "io" + "net" + "strings" + "sync" + "time" +) + +const ( + VersionTLS10 = 0x0301 + VersionTLS11 = 0x0302 + VersionTLS12 = 0x0303 + VersionTLS13 = 0x0304 + + // Deprecated: SSLv3 is cryptographically broken, and is no longer + // supported by this package. See golang.org/issue/32716. + VersionSSL30 = 0x0300 +) + +const ( + maxPlaintext = 16384 // maximum plaintext payload length + maxCiphertext = 16384 + 2048 // maximum ciphertext payload length + maxCiphertextTLS13 = 16384 + 256 // maximum ciphertext length in TLS 1.3 + recordHeaderLen = 5 // record header length + maxHandshake = 65536 // maximum handshake we support (protocol max is 16 MB) + maxUselessRecords = 16 // maximum number of consecutive non-advancing records +) + +// TLS record types. +type recordType uint8 + +const ( + recordTypeChangeCipherSpec recordType = 20 + recordTypeAlert recordType = 21 + recordTypeHandshake recordType = 22 + recordTypeApplicationData recordType = 23 +) + +// TLS handshake message types. +const ( + typeHelloRequest uint8 = 0 + typeClientHello uint8 = 1 + typeServerHello uint8 = 2 + typeNewSessionTicket uint8 = 4 + typeEndOfEarlyData uint8 = 5 + typeEncryptedExtensions uint8 = 8 + typeCertificate uint8 = 11 + typeServerKeyExchange uint8 = 12 + typeCertificateRequest uint8 = 13 + typeServerHelloDone uint8 = 14 + typeCertificateVerify uint8 = 15 + typeClientKeyExchange uint8 = 16 + typeFinished uint8 = 20 + typeCertificateStatus uint8 = 22 + typeKeyUpdate uint8 = 24 + typeNextProtocol uint8 = 67 // Not IANA assigned + typeMessageHash uint8 = 254 // synthetic message +) + +// TLS compression types. +const ( + compressionNone uint8 = 0 +) + +// TLS extension numbers +const ( + extensionServerName uint16 = 0 + extensionStatusRequest uint16 = 5 + extensionSupportedCurves uint16 = 10 // supported_groups in TLS 1.3, see RFC 8446, Section 4.2.7 + extensionSupportedPoints uint16 = 11 + extensionSignatureAlgorithms uint16 = 13 + extensionALPN uint16 = 16 + extensionSCT uint16 = 18 + extensionSessionTicket uint16 = 35 + extensionPreSharedKey uint16 = 41 + extensionEarlyData uint16 = 42 + extensionSupportedVersions uint16 = 43 + extensionCookie uint16 = 44 + extensionPSKModes uint16 = 45 + extensionCertificateAuthorities uint16 = 47 + extensionSignatureAlgorithmsCert uint16 = 50 + extensionKeyShare uint16 = 51 + extensionRenegotiationInfo uint16 = 0xff01 +) + +// TLS signaling cipher suite values +const ( + scsvRenegotiation uint16 = 0x00ff +) + +// CurveID is the type of a TLS identifier for an elliptic curve. See +// https://www.iana.org/assignments/tls-parameters/tls-parameters.xml#tls-parameters-8. +// +// In TLS 1.3, this type is called NamedGroup, but at this time this library +// only supports Elliptic Curve based groups. See RFC 8446, Section 4.2.7. +type CurveID uint16 + +const ( + CurveP256 CurveID = 23 + CurveP384 CurveID = 24 + CurveP521 CurveID = 25 + X25519 CurveID = 29 +) + +// TLS 1.3 Key Share. See RFC 8446, Section 4.2.8. +type keyShare struct { + group CurveID + data []byte +} + +// TLS 1.3 PSK Key Exchange Modes. See RFC 8446, Section 4.2.9. +const ( + pskModePlain uint8 = 0 + pskModeDHE uint8 = 1 +) + +// TLS 1.3 PSK Identity. Can be a Session Ticket, or a reference to a saved +// session. See RFC 8446, Section 4.2.11. +type pskIdentity struct { + label []byte + obfuscatedTicketAge uint32 +} + +// TLS Elliptic Curve Point Formats +// https://www.iana.org/assignments/tls-parameters/tls-parameters.xml#tls-parameters-9 +const ( + pointFormatUncompressed uint8 = 0 +) + +// TLS CertificateStatusType (RFC 3546) +const ( + statusTypeOCSP uint8 = 1 +) + +// Certificate types (for certificateRequestMsg) +const ( + certTypeRSASign = 1 + certTypeECDSASign = 64 // ECDSA or EdDSA keys, see RFC 8422, Section 3. +) + +// Signature algorithms (for internal signaling use). Starting at 225 to avoid overlap with +// TLS 1.2 codepoints (RFC 5246, Appendix A.4.1), with which these have nothing to do. +const ( + signaturePKCS1v15 uint8 = iota + 225 + signatureRSAPSS + signatureECDSA + signatureEd25519 +) + +// directSigning is a standard Hash value that signals that no pre-hashing +// should be performed, and that the input should be signed directly. It is the +// hash function associated with the Ed25519 signature scheme. +var directSigning crypto.Hash = 0 + +// supportedSignatureAlgorithms contains the signature and hash algorithms that +// the code advertises as supported in a TLS 1.2+ ClientHello and in a TLS 1.2+ +// CertificateRequest. The two fields are merged to match with TLS 1.3. +// Note that in TLS 1.2, the ECDSA algorithms are not constrained to P-256, etc. +var supportedSignatureAlgorithms = []SignatureScheme{ + PSSWithSHA256, + ECDSAWithP256AndSHA256, + Ed25519, + PSSWithSHA384, + PSSWithSHA512, + PKCS1WithSHA256, + PKCS1WithSHA384, + PKCS1WithSHA512, + ECDSAWithP384AndSHA384, + ECDSAWithP521AndSHA512, + PKCS1WithSHA1, + ECDSAWithSHA1, +} + +// helloRetryRequestRandom is set as the Random value of a ServerHello +// to signal that the message is actually a HelloRetryRequest. +var helloRetryRequestRandom = []byte{ // See RFC 8446, Section 4.1.3. + 0xCF, 0x21, 0xAD, 0x74, 0xE5, 0x9A, 0x61, 0x11, + 0xBE, 0x1D, 0x8C, 0x02, 0x1E, 0x65, 0xB8, 0x91, + 0xC2, 0xA2, 0x11, 0x16, 0x7A, 0xBB, 0x8C, 0x5E, + 0x07, 0x9E, 0x09, 0xE2, 0xC8, 0xA8, 0x33, 0x9C, +} + +const ( + // downgradeCanaryTLS12 or downgradeCanaryTLS11 is embedded in the server + // random as a downgrade protection if the server would be capable of + // negotiating a higher version. See RFC 8446, Section 4.1.3. + downgradeCanaryTLS12 = "DOWNGRD\x01" + downgradeCanaryTLS11 = "DOWNGRD\x00" +) + +// testingOnlyForceDowngradeCanary is set in tests to force the server side to +// include downgrade canaries even if it's using its highers supported version. +var testingOnlyForceDowngradeCanary bool + +// ConnectionState records basic TLS details about the connection. +type ConnectionState struct { + // Version is the TLS version used by the connection (e.g. VersionTLS12). + Version uint16 + + // HandshakeComplete is true if the handshake has concluded. + HandshakeComplete bool + + // DidResume is true if this connection was successfully resumed from a + // previous session with a session ticket or similar mechanism. + DidResume bool + + // CipherSuite is the cipher suite negotiated for the connection (e.g. + // TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, TLS_AES_128_GCM_SHA256). + CipherSuite uint16 + + // NegotiatedProtocol is the application protocol negotiated with ALPN. + NegotiatedProtocol string + + // NegotiatedProtocolIsMutual used to indicate a mutual NPN negotiation. + // + // Deprecated: this value is always true. + NegotiatedProtocolIsMutual bool + + // ServerName is the value of the Server Name Indication extension sent by + // the client. It's available both on the server and on the client side. + ServerName string + + // PeerCertificates are the parsed certificates sent by the peer, in the + // order in which they were sent. The first element is the leaf certificate + // that the connection is verified against. + // + // On the client side, it can't be empty. On the server side, it can be + // empty if Config.ClientAuth is not RequireAnyClientCert or + // RequireAndVerifyClientCert. + PeerCertificates []*x509.Certificate + + // VerifiedChains is a list of one or more chains where the first element is + // PeerCertificates[0] and the last element is from Config.RootCAs (on the + // client side) or Config.ClientCAs (on the server side). + // + // On the client side, it's set if Config.InsecureSkipVerify is false. On + // the server side, it's set if Config.ClientAuth is VerifyClientCertIfGiven + // (and the peer provided a certificate) or RequireAndVerifyClientCert. + VerifiedChains [][]*x509.Certificate + + // SignedCertificateTimestamps is a list of SCTs provided by the peer + // through the TLS handshake for the leaf certificate, if any. + SignedCertificateTimestamps [][]byte + + // OCSPResponse is a stapled Online Certificate Status Protocol (OCSP) + // response provided by the peer for the leaf certificate, if any. + OCSPResponse []byte + + // TLSUnique contains the "tls-unique" channel binding value (see RFC 5929, + // Section 3). This value will be nil for TLS 1.3 connections and for all + // resumed connections. + // + // Deprecated: there are conditions in which this value might not be unique + // to a connection. See the Security Considerations sections of RFC 5705 and + // RFC 7627, and https://mitls.org/pages/attacks/3SHAKE#channelbindings. + TLSUnique []byte + + // ekm is a closure exposed via ExportKeyingMaterial. + ekm func(label string, context []byte, length int) ([]byte, error) +} + +// ExportKeyingMaterial returns length bytes of exported key material in a new +// slice as defined in RFC 5705. If context is nil, it is not used as part of +// the seed. If the connection was set to allow renegotiation via +// Config.Renegotiation, this function will return an error. +func (cs *ConnectionState) ExportKeyingMaterial(label string, context []byte, length int) ([]byte, error) { + return cs.ekm(label, context, length) +} + +// ClientAuthType declares the policy the server will follow for +// TLS Client Authentication. +type ClientAuthType int + +const ( + // NoClientCert indicates that no client certificate should be requested + // during the handshake, and if any certificates are sent they will not + // be verified. + NoClientCert ClientAuthType = iota + // RequestClientCert indicates that a client certificate should be requested + // during the handshake, but does not require that the client send any + // certificates. + RequestClientCert + // RequireAnyClientCert indicates that a client certificate should be requested + // during the handshake, and that at least one certificate is required to be + // sent by the client, but that certificate is not required to be valid. + RequireAnyClientCert + // VerifyClientCertIfGiven indicates that a client certificate should be requested + // during the handshake, but does not require that the client sends a + // certificate. If the client does send a certificate it is required to be + // valid. + VerifyClientCertIfGiven + // RequireAndVerifyClientCert indicates that a client certificate should be requested + // during the handshake, and that at least one valid certificate is required + // to be sent by the client. + RequireAndVerifyClientCert +) + +// requiresClientCert reports whether the ClientAuthType requires a client +// certificate to be provided. +func requiresClientCert(c ClientAuthType) bool { + switch c { + case RequireAnyClientCert, RequireAndVerifyClientCert: + return true + default: + return false + } +} + +// ClientSessionState contains the state needed by clients to resume TLS +// sessions. +type ClientSessionState struct { + sessionTicket []uint8 // Encrypted ticket used for session resumption with server + vers uint16 // TLS version negotiated for the session + cipherSuite uint16 // Ciphersuite negotiated for the session + masterSecret []byte // Full handshake MasterSecret, or TLS 1.3 resumption_master_secret + serverCertificates []*x509.Certificate // Certificate chain presented by the server + verifiedChains [][]*x509.Certificate // Certificate chains we built for verification + receivedAt time.Time // When the session ticket was received from the server + ocspResponse []byte // Stapled OCSP response presented by the server + scts [][]byte // SCTs presented by the server + + // TLS 1.3 fields. + nonce []byte // Ticket nonce sent by the server, to derive PSK + useBy time.Time // Expiration of the ticket lifetime as set by the server + ageAdd uint32 // Random obfuscation factor for sending the ticket age +} + +// ClientSessionCache is a cache of ClientSessionState objects that can be used +// by a client to resume a TLS session with a given server. ClientSessionCache +// implementations should expect to be called concurrently from different +// goroutines. Up to TLS 1.2, only ticket-based resumption is supported, not +// SessionID-based resumption. In TLS 1.3 they were merged into PSK modes, which +// are supported via this interface. +type ClientSessionCache interface { + // Get searches for a ClientSessionState associated with the given key. + // On return, ok is true if one was found. + Get(sessionKey string) (session *ClientSessionState, ok bool) + + // Put adds the ClientSessionState to the cache with the given key. It might + // get called multiple times in a connection if a TLS 1.3 server provides + // more than one session ticket. If called with a nil *ClientSessionState, + // it should remove the cache entry. + Put(sessionKey string, cs *ClientSessionState) +} + +//go:generate stringer -type=SignatureScheme,CurveID,ClientAuthType -output=common_string.go + +// SignatureScheme identifies a signature algorithm supported by TLS. See +// RFC 8446, Section 4.2.3. +type SignatureScheme uint16 + +const ( + // RSASSA-PKCS1-v1_5 algorithms. + PKCS1WithSHA256 SignatureScheme = 0x0401 + PKCS1WithSHA384 SignatureScheme = 0x0501 + PKCS1WithSHA512 SignatureScheme = 0x0601 + + // RSASSA-PSS algorithms with public key OID rsaEncryption. + PSSWithSHA256 SignatureScheme = 0x0804 + PSSWithSHA384 SignatureScheme = 0x0805 + PSSWithSHA512 SignatureScheme = 0x0806 + + // ECDSA algorithms. Only constrained to a specific curve in TLS 1.3. + ECDSAWithP256AndSHA256 SignatureScheme = 0x0403 + ECDSAWithP384AndSHA384 SignatureScheme = 0x0503 + ECDSAWithP521AndSHA512 SignatureScheme = 0x0603 + + // EdDSA algorithms. + Ed25519 SignatureScheme = 0x0807 + + // Legacy signature and hash algorithms for TLS 1.2. + PKCS1WithSHA1 SignatureScheme = 0x0201 + ECDSAWithSHA1 SignatureScheme = 0x0203 +) + +// ClientHelloInfo contains information from a ClientHello message in order to +// guide application logic in the GetCertificate and GetConfigForClient callbacks. +type ClientHelloInfo struct { + // CipherSuites lists the CipherSuites supported by the client (e.g. + // TLS_AES_128_GCM_SHA256, TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256). + CipherSuites []uint16 + + // ServerName indicates the name of the server requested by the client + // in order to support virtual hosting. ServerName is only set if the + // client is using SNI (see RFC 4366, Section 3.1). + ServerName string + + // SupportedCurves lists the elliptic curves supported by the client. + // SupportedCurves is set only if the Supported Elliptic Curves + // Extension is being used (see RFC 4492, Section 5.1.1). + SupportedCurves []CurveID + + // SupportedPoints lists the point formats supported by the client. + // SupportedPoints is set only if the Supported Point Formats Extension + // is being used (see RFC 4492, Section 5.1.2). + SupportedPoints []uint8 + + // SignatureSchemes lists the signature and hash schemes that the client + // is willing to verify. SignatureSchemes is set only if the Signature + // Algorithms Extension is being used (see RFC 5246, Section 7.4.1.4.1). + SignatureSchemes []SignatureScheme + + // SupportedProtos lists the application protocols supported by the client. + // SupportedProtos is set only if the Application-Layer Protocol + // Negotiation Extension is being used (see RFC 7301, Section 3.1). + // + // Servers can select a protocol by setting Config.NextProtos in a + // GetConfigForClient return value. + SupportedProtos []string + + // SupportedVersions lists the TLS versions supported by the client. + // For TLS versions less than 1.3, this is extrapolated from the max + // version advertised by the client, so values other than the greatest + // might be rejected if used. + SupportedVersions []uint16 + + // Conn is the underlying net.Conn for the connection. Do not read + // from, or write to, this connection; that will cause the TLS + // connection to fail. + Conn net.Conn + + // config is embedded by the GetCertificate or GetConfigForClient caller, + // for use with SupportsCertificate. + config *Config + + // ctx is the context of the handshake that is in progress. + ctx context.Context +} + +// Context returns the context of the handshake that is in progress. +// This context is a child of the context passed to HandshakeContext, +// if any, and is canceled when the handshake concludes. +func (c *ClientHelloInfo) Context() context.Context { + return c.ctx +} + +// CertificateRequestInfo contains information from a server's +// CertificateRequest message, which is used to demand a certificate and proof +// of control from a client. +type CertificateRequestInfo struct { + // AcceptableCAs contains zero or more, DER-encoded, X.501 + // Distinguished Names. These are the names of root or intermediate CAs + // that the server wishes the returned certificate to be signed by. An + // empty slice indicates that the server has no preference. + AcceptableCAs [][]byte + + // SignatureSchemes lists the signature schemes that the server is + // willing to verify. + SignatureSchemes []SignatureScheme + + // Version is the TLS version that was negotiated for this connection. + Version uint16 + + // ctx is the context of the handshake that is in progress. + ctx context.Context +} + +// Context returns the context of the handshake that is in progress. +// This context is a child of the context passed to HandshakeContext, +// if any, and is canceled when the handshake concludes. +func (c *CertificateRequestInfo) Context() context.Context { + return c.ctx +} + +// RenegotiationSupport enumerates the different levels of support for TLS +// renegotiation. TLS renegotiation is the act of performing subsequent +// handshakes on a connection after the first. This significantly complicates +// the state machine and has been the source of numerous, subtle security +// issues. Initiating a renegotiation is not supported, but support for +// accepting renegotiation requests may be enabled. +// +// Even when enabled, the server may not change its identity between handshakes +// (i.e. the leaf certificate must be the same). Additionally, concurrent +// handshake and application data flow is not permitted so renegotiation can +// only be used with protocols that synchronise with the renegotiation, such as +// HTTPS. +// +// Renegotiation is not defined in TLS 1.3. +type RenegotiationSupport int + +const ( + // RenegotiateNever disables renegotiation. + RenegotiateNever RenegotiationSupport = iota + + // RenegotiateOnceAsClient allows a remote server to request + // renegotiation once per connection. + RenegotiateOnceAsClient + + // RenegotiateFreelyAsClient allows a remote server to repeatedly + // request renegotiation. + RenegotiateFreelyAsClient +) + +// A Config structure is used to configure a TLS client or server. +// After one has been passed to a TLS function it must not be +// modified. A Config may be reused; the tls package will also not +// modify it. +type Config struct { + // Rand provides the source of entropy for nonces and RSA blinding. + // If Rand is nil, TLS uses the cryptographic random reader in package + // crypto/rand. + // The Reader must be safe for use by multiple goroutines. + Rand io.Reader + + // Time returns the current time as the number of seconds since the epoch. + // If Time is nil, TLS uses time.Now. + Time func() time.Time + + // Certificates contains one or more certificate chains to present to the + // other side of the connection. The first certificate compatible with the + // peer's requirements is selected automatically. + // + // Server configurations must set one of Certificates, GetCertificate or + // GetConfigForClient. Clients doing client-authentication may set either + // Certificates or GetClientCertificate. + // + // Note: if there are multiple Certificates, and they don't have the + // optional field Leaf set, certificate selection will incur a significant + // per-handshake performance cost. + Certificates []Certificate + + // NameToCertificate maps from a certificate name to an element of + // Certificates. Note that a certificate name can be of the form + // '*.example.com' and so doesn't have to be a domain name as such. + // + // Deprecated: NameToCertificate only allows associating a single + // certificate with a given name. Leave this field nil to let the library + // select the first compatible chain from Certificates. + NameToCertificate map[string]*Certificate + + // GetCertificate returns a Certificate based on the given + // ClientHelloInfo. It will only be called if the client supplies SNI + // information or if Certificates is empty. + // + // If GetCertificate is nil or returns nil, then the certificate is + // retrieved from NameToCertificate. If NameToCertificate is nil, the + // best element of Certificates will be used. + GetCertificate func(*ClientHelloInfo) (*Certificate, error) + + // GetClientCertificate, if not nil, is called when a server requests a + // certificate from a client. If set, the contents of Certificates will + // be ignored. + // + // If GetClientCertificate returns an error, the handshake will be + // aborted and that error will be returned. Otherwise + // GetClientCertificate must return a non-nil Certificate. If + // Certificate.Certificate is empty then no certificate will be sent to + // the server. If this is unacceptable to the server then it may abort + // the handshake. + // + // GetClientCertificate may be called multiple times for the same + // connection if renegotiation occurs or if TLS 1.3 is in use. + GetClientCertificate func(*CertificateRequestInfo) (*Certificate, error) + + // GetConfigForClient, if not nil, is called after a ClientHello is + // received from a client. It may return a non-nil Config in order to + // change the Config that will be used to handle this connection. If + // the returned Config is nil, the original Config will be used. The + // Config returned by this callback may not be subsequently modified. + // + // If GetConfigForClient is nil, the Config passed to Server() will be + // used for all connections. + // + // If SessionTicketKey was explicitly set on the returned Config, or if + // SetSessionTicketKeys was called on the returned Config, those keys will + // be used. Otherwise, the original Config keys will be used (and possibly + // rotated if they are automatically managed). + GetConfigForClient func(*ClientHelloInfo) (*Config, error) + + // VerifyPeerCertificate, if not nil, is called after normal + // certificate verification by either a TLS client or server. It + // receives the raw ASN.1 certificates provided by the peer and also + // any verified chains that normal processing found. If it returns a + // non-nil error, the handshake is aborted and that error results. + // + // If normal verification fails then the handshake will abort before + // considering this callback. If normal verification is disabled by + // setting InsecureSkipVerify, or (for a server) when ClientAuth is + // RequestClientCert or RequireAnyClientCert, then this callback will + // be considered but the verifiedChains argument will always be nil. + VerifyPeerCertificate func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error + + // VerifyConnection, if not nil, is called after normal certificate + // verification and after VerifyPeerCertificate by either a TLS client + // or server. If it returns a non-nil error, the handshake is aborted + // and that error results. + // + // If normal verification fails then the handshake will abort before + // considering this callback. This callback will run for all connections + // regardless of InsecureSkipVerify or ClientAuth settings. + VerifyConnection func(ConnectionState) error + + // RootCAs defines the set of root certificate authorities + // that clients use when verifying server certificates. + // If RootCAs is nil, TLS uses the host's root CA set. + RootCAs *x509.CertPool + + // NextProtos is a list of supported application level protocols, in + // order of preference. If both peers support ALPN, the selected + // protocol will be one from this list, and the connection will fail + // if there is no mutually supported protocol. If NextProtos is empty + // or the peer doesn't support ALPN, the connection will succeed and + // ConnectionState.NegotiatedProtocol will be empty. + NextProtos []string + + // ServerName is used to verify the hostname on the returned + // certificates unless InsecureSkipVerify is given. It is also included + // in the client's handshake to support virtual hosting unless it is + // an IP address. + ServerName string + + // ClientAuth determines the server's policy for + // TLS Client Authentication. The default is NoClientCert. + ClientAuth ClientAuthType + + // ClientCAs defines the set of root certificate authorities + // that servers use if required to verify a client certificate + // by the policy in ClientAuth. + ClientCAs *x509.CertPool + + // InsecureSkipVerify controls whether a client verifies the server's + // certificate chain and host name. If InsecureSkipVerify is true, crypto/tls + // accepts any certificate presented by the server and any host name in that + // certificate. In this mode, TLS is susceptible to machine-in-the-middle + // attacks unless custom verification is used. This should be used only for + // testing or in combination with VerifyConnection or VerifyPeerCertificate. + InsecureSkipVerify bool + + // CipherSuites is a list of enabled TLS 1.0–1.2 cipher suites. The order of + // the list is ignored. Note that TLS 1.3 ciphersuites are not configurable. + // + // If CipherSuites is nil, a safe default list is used. The default cipher + // suites might change over time. + CipherSuites []uint16 + + // PreferServerCipherSuites is a legacy field and has no effect. + // + // It used to control whether the server would follow the client's or the + // server's preference. Servers now select the best mutually supported + // cipher suite based on logic that takes into account inferred client + // hardware, server hardware, and security. + // + // Deprecated: PreferServerCipherSuites is ignored. + PreferServerCipherSuites bool + + // SessionTicketsDisabled may be set to true to disable session ticket and + // PSK (resumption) support. Note that on clients, session ticket support is + // also disabled if ClientSessionCache is nil. + SessionTicketsDisabled bool + + // SessionTicketKey is used by TLS servers to provide session resumption. + // See RFC 5077 and the PSK mode of RFC 8446. If zero, it will be filled + // with random data before the first server handshake. + // + // Deprecated: if this field is left at zero, session ticket keys will be + // automatically rotated every day and dropped after seven days. For + // customizing the rotation schedule or synchronizing servers that are + // terminating connections for the same host, use SetSessionTicketKeys. + SessionTicketKey [32]byte + + // ClientSessionCache is a cache of ClientSessionState entries for TLS + // session resumption. It is only used by clients. + ClientSessionCache ClientSessionCache + + // MinVersion contains the minimum TLS version that is acceptable. + // + // By default, TLS 1.2 is currently used as the minimum when acting as a + // client, and TLS 1.0 when acting as a server. TLS 1.0 is the minimum + // supported by this package, both as a client and as a server. + // + // The client-side default can temporarily be reverted to TLS 1.0 by + // including the value "x509sha1=1" in the GODEBUG environment variable. + // Note that this option will be removed in Go 1.19 (but it will still be + // possible to set this field to VersionTLS10 explicitly). + MinVersion uint16 + + // MaxVersion contains the maximum TLS version that is acceptable. + // + // By default, the maximum version supported by this package is used, + // which is currently TLS 1.3. + MaxVersion uint16 + + // CurvePreferences contains the elliptic curves that will be used in + // an ECDHE handshake, in preference order. If empty, the default will + // be used. The client will use the first preference as the type for + // its key share in TLS 1.3. This may change in the future. + CurvePreferences []CurveID + + // DynamicRecordSizingDisabled disables adaptive sizing of TLS records. + // When true, the largest possible TLS record size is always used. When + // false, the size of TLS records may be adjusted in an attempt to + // improve latency. + DynamicRecordSizingDisabled bool + + // Renegotiation controls what types of renegotiation are supported. + // The default, none, is correct for the vast majority of applications. + Renegotiation RenegotiationSupport + + // KeyLogWriter optionally specifies a destination for TLS master secrets + // in NSS key log format that can be used to allow external programs + // such as Wireshark to decrypt TLS connections. + // See https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/Key_Log_Format. + // Use of KeyLogWriter compromises security and should only be + // used for debugging. + KeyLogWriter io.Writer + + // mutex protects sessionTicketKeys and autoSessionTicketKeys. + mutex sync.RWMutex + // sessionTicketKeys contains zero or more ticket keys. If set, it means the + // the keys were set with SessionTicketKey or SetSessionTicketKeys. The + // first key is used for new tickets and any subsequent keys can be used to + // decrypt old tickets. The slice contents are not protected by the mutex + // and are immutable. + sessionTicketKeys []ticketKey + // autoSessionTicketKeys is like sessionTicketKeys but is owned by the + // auto-rotation logic. See Config.ticketKeys. + autoSessionTicketKeys []ticketKey +} + +const ( + // ticketKeyNameLen is the number of bytes of identifier that is prepended to + // an encrypted session ticket in order to identify the key used to encrypt it. + ticketKeyNameLen = 16 + + // ticketKeyLifetime is how long a ticket key remains valid and can be used to + // resume a client connection. + ticketKeyLifetime = 7 * 24 * time.Hour // 7 days + + // ticketKeyRotation is how often the server should rotate the session ticket key + // that is used for new tickets. + ticketKeyRotation = 24 * time.Hour +) + +// ticketKey is the internal representation of a session ticket key. +type ticketKey struct { + // keyName is an opaque byte string that serves to identify the session + // ticket key. It's exposed as plaintext in every session ticket. + keyName [ticketKeyNameLen]byte + aesKey [16]byte + hmacKey [16]byte + // created is the time at which this ticket key was created. See Config.ticketKeys. + created time.Time +} + +// ticketKeyFromBytes converts from the external representation of a session +// ticket key to a ticketKey. Externally, session ticket keys are 32 random +// bytes and this function expands that into sufficient name and key material. +func (c *Config) ticketKeyFromBytes(b [32]byte) (key ticketKey) { + hashed := sha512.Sum512(b[:]) + copy(key.keyName[:], hashed[:ticketKeyNameLen]) + copy(key.aesKey[:], hashed[ticketKeyNameLen:ticketKeyNameLen+16]) + copy(key.hmacKey[:], hashed[ticketKeyNameLen+16:ticketKeyNameLen+32]) + key.created = c.time() + return key +} + +// maxSessionTicketLifetime is the maximum allowed lifetime of a TLS 1.3 session +// ticket, and the lifetime we set for tickets we send. +const maxSessionTicketLifetime = 7 * 24 * time.Hour + +// Clone returns a shallow clone of c or nil if c is nil. It is safe to clone a Config that is +// being used concurrently by a TLS client or server. +func (c *Config) Clone() *Config { + if c == nil { + return nil + } + c.mutex.RLock() + defer c.mutex.RUnlock() + return &Config{ + Rand: c.Rand, + Time: c.Time, + Certificates: c.Certificates, + NameToCertificate: c.NameToCertificate, + GetCertificate: c.GetCertificate, + GetClientCertificate: c.GetClientCertificate, + GetConfigForClient: c.GetConfigForClient, + VerifyPeerCertificate: c.VerifyPeerCertificate, + VerifyConnection: c.VerifyConnection, + RootCAs: c.RootCAs, + NextProtos: c.NextProtos, + ServerName: c.ServerName, + ClientAuth: c.ClientAuth, + ClientCAs: c.ClientCAs, + InsecureSkipVerify: c.InsecureSkipVerify, + CipherSuites: c.CipherSuites, + PreferServerCipherSuites: c.PreferServerCipherSuites, + SessionTicketsDisabled: c.SessionTicketsDisabled, + SessionTicketKey: c.SessionTicketKey, + ClientSessionCache: c.ClientSessionCache, + MinVersion: c.MinVersion, + MaxVersion: c.MaxVersion, + CurvePreferences: c.CurvePreferences, + DynamicRecordSizingDisabled: c.DynamicRecordSizingDisabled, + Renegotiation: c.Renegotiation, + KeyLogWriter: c.KeyLogWriter, + sessionTicketKeys: c.sessionTicketKeys, + autoSessionTicketKeys: c.autoSessionTicketKeys, + } +} + +// deprecatedSessionTicketKey is set as the prefix of SessionTicketKey if it was +// randomized for backwards compatibility but is not in use. +var deprecatedSessionTicketKey = []byte("DEPRECATED") + +// initLegacySessionTicketKeyRLocked ensures the legacy SessionTicketKey field is +// randomized if empty, and that sessionTicketKeys is populated from it otherwise. +func (c *Config) initLegacySessionTicketKeyRLocked() { + // Don't write if SessionTicketKey is already defined as our deprecated string, + // or if it is defined by the user but sessionTicketKeys is already set. + if c.SessionTicketKey != [32]byte{} && + (bytes.HasPrefix(c.SessionTicketKey[:], deprecatedSessionTicketKey) || len(c.sessionTicketKeys) > 0) { + return + } + + // We need to write some data, so get an exclusive lock and re-check any conditions. + c.mutex.RUnlock() + defer c.mutex.RLock() + c.mutex.Lock() + defer c.mutex.Unlock() + if c.SessionTicketKey == [32]byte{} { + if _, err := io.ReadFull(c.rand(), c.SessionTicketKey[:]); err != nil { + panic(fmt.Sprintf("tls: unable to generate random session ticket key: %v", err)) + } + // Write the deprecated prefix at the beginning so we know we created + // it. This key with the DEPRECATED prefix isn't used as an actual + // session ticket key, and is only randomized in case the application + // reuses it for some reason. + copy(c.SessionTicketKey[:], deprecatedSessionTicketKey) + } else if !bytes.HasPrefix(c.SessionTicketKey[:], deprecatedSessionTicketKey) && len(c.sessionTicketKeys) == 0 { + c.sessionTicketKeys = []ticketKey{c.ticketKeyFromBytes(c.SessionTicketKey)} + } + +} + +// ticketKeys returns the ticketKeys for this connection. +// If configForClient has explicitly set keys, those will +// be returned. Otherwise, the keys on c will be used and +// may be rotated if auto-managed. +// During rotation, any expired session ticket keys are deleted from +// c.sessionTicketKeys. If the session ticket key that is currently +// encrypting tickets (ie. the first ticketKey in c.sessionTicketKeys) +// is not fresh, then a new session ticket key will be +// created and prepended to c.sessionTicketKeys. +func (c *Config) ticketKeys(configForClient *Config) []ticketKey { + // If the ConfigForClient callback returned a Config with explicitly set + // keys, use those, otherwise just use the original Config. + if configForClient != nil { + configForClient.mutex.RLock() + if configForClient.SessionTicketsDisabled { + return nil + } + configForClient.initLegacySessionTicketKeyRLocked() + if len(configForClient.sessionTicketKeys) != 0 { + ret := configForClient.sessionTicketKeys + configForClient.mutex.RUnlock() + return ret + } + configForClient.mutex.RUnlock() + } + + c.mutex.RLock() + defer c.mutex.RUnlock() + if c.SessionTicketsDisabled { + return nil + } + c.initLegacySessionTicketKeyRLocked() + if len(c.sessionTicketKeys) != 0 { + return c.sessionTicketKeys + } + // Fast path for the common case where the key is fresh enough. + if len(c.autoSessionTicketKeys) > 0 && c.time().Sub(c.autoSessionTicketKeys[0].created) < ticketKeyRotation { + return c.autoSessionTicketKeys + } + + // autoSessionTicketKeys are managed by auto-rotation. + c.mutex.RUnlock() + defer c.mutex.RLock() + c.mutex.Lock() + defer c.mutex.Unlock() + // Re-check the condition in case it changed since obtaining the new lock. + if len(c.autoSessionTicketKeys) == 0 || c.time().Sub(c.autoSessionTicketKeys[0].created) >= ticketKeyRotation { + var newKey [32]byte + if _, err := io.ReadFull(c.rand(), newKey[:]); err != nil { + panic(fmt.Sprintf("unable to generate random session ticket key: %v", err)) + } + valid := make([]ticketKey, 0, len(c.autoSessionTicketKeys)+1) + valid = append(valid, c.ticketKeyFromBytes(newKey)) + for _, k := range c.autoSessionTicketKeys { + // While rotating the current key, also remove any expired ones. + if c.time().Sub(k.created) < ticketKeyLifetime { + valid = append(valid, k) + } + } + c.autoSessionTicketKeys = valid + } + return c.autoSessionTicketKeys +} + +// SetSessionTicketKeys updates the session ticket keys for a server. +// +// The first key will be used when creating new tickets, while all keys can be +// used for decrypting tickets. It is safe to call this function while the +// server is running in order to rotate the session ticket keys. The function +// will panic if keys is empty. +// +// Calling this function will turn off automatic session ticket key rotation. +// +// If multiple servers are terminating connections for the same host they should +// all have the same session ticket keys. If the session ticket keys leaks, +// previously recorded and future TLS connections using those keys might be +// compromised. +func (c *Config) SetSessionTicketKeys(keys [][32]byte) { + if len(keys) == 0 { + panic("tls: keys must have at least one key") + } + + newKeys := make([]ticketKey, len(keys)) + for i, bytes := range keys { + newKeys[i] = c.ticketKeyFromBytes(bytes) + } + + c.mutex.Lock() + c.sessionTicketKeys = newKeys + c.mutex.Unlock() +} + +func (c *Config) rand() io.Reader { + r := c.Rand + if r == nil { + return rand.Reader + } + return r +} + +func (c *Config) time() time.Time { + t := c.Time + if t == nil { + t = time.Now + } + return t() +} + +func (c *Config) cipherSuites() []uint16 { + if c.CipherSuites != nil { + return c.CipherSuites + } + return defaultCipherSuites +} + +var supportedVersions = []uint16{ + VersionTLS13, + VersionTLS12, + VersionTLS11, + VersionTLS10, +} + +// debugEnableTLS10 enables TLS 1.0. See issue 45428. +var debugEnableTLS10 = godebug.Get("tls10default") == "1" + +// roleClient and roleServer are meant to call supportedVersions and parents +// with more readability at the callsite. +const roleClient = true +const roleServer = false + +func (c *Config) supportedVersions(isClient bool) []uint16 { + versions := make([]uint16, 0, len(supportedVersions)) + for _, v := range supportedVersions { + if (c == nil || c.MinVersion == 0) && !debugEnableTLS10 && + isClient && v < VersionTLS12 { + continue + } + if c != nil && c.MinVersion != 0 && v < c.MinVersion { + continue + } + if c != nil && c.MaxVersion != 0 && v > c.MaxVersion { + continue + } + versions = append(versions, v) + } + return versions +} + +func (c *Config) maxSupportedVersion(isClient bool) uint16 { + supportedVersions := c.supportedVersions(isClient) + if len(supportedVersions) == 0 { + return 0 + } + return supportedVersions[0] +} + +// supportedVersionsFromMax returns a list of supported versions derived from a +// legacy maximum version value. Note that only versions supported by this +// library are returned. Any newer peer will use supportedVersions anyway. +func supportedVersionsFromMax(maxVersion uint16) []uint16 { + versions := make([]uint16, 0, len(supportedVersions)) + for _, v := range supportedVersions { + if v > maxVersion { + continue + } + versions = append(versions, v) + } + return versions +} + +var defaultCurvePreferences = []CurveID{X25519, CurveP256, CurveP384, CurveP521} + +func (c *Config) curvePreferences() []CurveID { + if c == nil || len(c.CurvePreferences) == 0 { + return defaultCurvePreferences + } + return c.CurvePreferences +} + +func (c *Config) supportsCurve(curve CurveID) bool { + for _, cc := range c.curvePreferences() { + if cc == curve { + return true + } + } + return false +} + +// mutualVersion returns the protocol version to use given the advertised +// versions of the peer. Priority is given to the peer preference order. +func (c *Config) mutualVersion(isClient bool, peerVersions []uint16) (uint16, bool) { + supportedVersions := c.supportedVersions(isClient) + for _, peerVersion := range peerVersions { + for _, v := range supportedVersions { + if v == peerVersion { + return v, true + } + } + } + return 0, false +} + +var errNoCertificates = errors.New("tls: no certificates configured") + +// getCertificate returns the best certificate for the given ClientHelloInfo, +// defaulting to the first element of c.Certificates. +func (c *Config) getCertificate(clientHello *ClientHelloInfo) (*Certificate, error) { + if c.GetCertificate != nil && + (len(c.Certificates) == 0 || len(clientHello.ServerName) > 0) { + cert, err := c.GetCertificate(clientHello) + if cert != nil || err != nil { + return cert, err + } + } + + if len(c.Certificates) == 0 { + return nil, errNoCertificates + } + + if len(c.Certificates) == 1 { + // There's only one choice, so no point doing any work. + return &c.Certificates[0], nil + } + + if c.NameToCertificate != nil { + name := strings.ToLower(clientHello.ServerName) + if cert, ok := c.NameToCertificate[name]; ok { + return cert, nil + } + if len(name) > 0 { + labels := strings.Split(name, ".") + labels[0] = "*" + wildcardName := strings.Join(labels, ".") + if cert, ok := c.NameToCertificate[wildcardName]; ok { + return cert, nil + } + } + } + + for _, cert := range c.Certificates { + if err := clientHello.SupportsCertificate(&cert); err == nil { + return &cert, nil + } + } + + // If nothing matches, return the first certificate. + return &c.Certificates[0], nil +} + +// SupportsCertificate returns nil if the provided certificate is supported by +// the client that sent the ClientHello. Otherwise, it returns an error +// describing the reason for the incompatibility. +// +// If this ClientHelloInfo was passed to a GetConfigForClient or GetCertificate +// callback, this method will take into account the associated Config. Note that +// if GetConfigForClient returns a different Config, the change can't be +// accounted for by this method. +// +// This function will call x509.ParseCertificate unless c.Leaf is set, which can +// incur a significant performance cost. +func (chi *ClientHelloInfo) SupportsCertificate(c *Certificate) error { + // Note we don't currently support certificate_authorities nor + // signature_algorithms_cert, and don't check the algorithms of the + // signatures on the chain (which anyway are a SHOULD, see RFC 8446, + // Section 4.4.2.2). + + config := chi.config + if config == nil { + config = &Config{} + } + vers, ok := config.mutualVersion(roleServer, chi.SupportedVersions) + if !ok { + return errors.New("no mutually supported protocol versions") + } + + // If the client specified the name they are trying to connect to, the + // certificate needs to be valid for it. + if chi.ServerName != "" { + x509Cert, err := c.leaf() + if err != nil { + return fmt.Errorf("failed to parse certificate: %w", err) + } + if err := x509Cert.VerifyHostname(chi.ServerName); err != nil { + return fmt.Errorf("certificate is not valid for requested server name: %w", err) + } + } + + // supportsRSAFallback returns nil if the certificate and connection support + // the static RSA key exchange, and unsupported otherwise. The logic for + // supporting static RSA is completely disjoint from the logic for + // supporting signed key exchanges, so we just check it as a fallback. + supportsRSAFallback := func(unsupported error) error { + // TLS 1.3 dropped support for the static RSA key exchange. + if vers == VersionTLS13 { + return unsupported + } + // The static RSA key exchange works by decrypting a challenge with the + // RSA private key, not by signing, so check the PrivateKey implements + // crypto.Decrypter, like *rsa.PrivateKey does. + if priv, ok := c.PrivateKey.(crypto.Decrypter); ok { + if _, ok := priv.Public().(*rsa.PublicKey); !ok { + return unsupported + } + } else { + return unsupported + } + // Finally, there needs to be a mutual cipher suite that uses the static + // RSA key exchange instead of ECDHE. + rsaCipherSuite := selectCipherSuite(chi.CipherSuites, config.cipherSuites(), func(c *cipherSuite) bool { + if c.flags&suiteECDHE != 0 { + return false + } + if vers < VersionTLS12 && c.flags&suiteTLS12 != 0 { + return false + } + return true + }) + if rsaCipherSuite == nil { + return unsupported + } + return nil + } + + // If the client sent the signature_algorithms extension, ensure it supports + // schemes we can use with this certificate and TLS version. + if len(chi.SignatureSchemes) > 0 { + if _, err := selectSignatureScheme(vers, c, chi.SignatureSchemes); err != nil { + return supportsRSAFallback(err) + } + } + + // In TLS 1.3 we are done because supported_groups is only relevant to the + // ECDHE computation, point format negotiation is removed, cipher suites are + // only relevant to the AEAD choice, and static RSA does not exist. + if vers == VersionTLS13 { + return nil + } + + // The only signed key exchange we support is ECDHE. + if !supportsECDHE(config, chi.SupportedCurves, chi.SupportedPoints) { + return supportsRSAFallback(errors.New("client doesn't support ECDHE, can only use legacy RSA key exchange")) + } + + var ecdsaCipherSuite bool + if priv, ok := c.PrivateKey.(crypto.Signer); ok { + switch pub := priv.Public().(type) { + case *ecdsa.PublicKey: + var curve CurveID + switch pub.Curve { + case elliptic.P256(): + curve = CurveP256 + case elliptic.P384(): + curve = CurveP384 + case elliptic.P521(): + curve = CurveP521 + default: + return supportsRSAFallback(unsupportedCertificateError(c)) + } + var curveOk bool + for _, c := range chi.SupportedCurves { + if c == curve && config.supportsCurve(c) { + curveOk = true + break + } + } + if !curveOk { + return errors.New("client doesn't support certificate curve") + } + ecdsaCipherSuite = true + case ed25519.PublicKey: + if vers < VersionTLS12 || len(chi.SignatureSchemes) == 0 { + return errors.New("connection doesn't support Ed25519") + } + ecdsaCipherSuite = true + case *rsa.PublicKey: + default: + return supportsRSAFallback(unsupportedCertificateError(c)) + } + } else { + return supportsRSAFallback(unsupportedCertificateError(c)) + } + + // Make sure that there is a mutually supported cipher suite that works with + // this certificate. Cipher suite selection will then apply the logic in + // reverse to pick it. See also serverHandshakeState.cipherSuiteOk. + cipherSuite := selectCipherSuite(chi.CipherSuites, config.cipherSuites(), func(c *cipherSuite) bool { + if c.flags&suiteECDHE == 0 { + return false + } + if c.flags&suiteECSign != 0 { + if !ecdsaCipherSuite { + return false + } + } else { + if ecdsaCipherSuite { + return false + } + } + if vers < VersionTLS12 && c.flags&suiteTLS12 != 0 { + return false + } + return true + }) + if cipherSuite == nil { + return supportsRSAFallback(errors.New("client doesn't support any cipher suites compatible with the certificate")) + } + + return nil +} + +// SupportsCertificate returns nil if the provided certificate is supported by +// the server that sent the CertificateRequest. Otherwise, it returns an error +// describing the reason for the incompatibility. +func (cri *CertificateRequestInfo) SupportsCertificate(c *Certificate) error { + if _, err := selectSignatureScheme(cri.Version, c, cri.SignatureSchemes); err != nil { + return err + } + + if len(cri.AcceptableCAs) == 0 { + return nil + } + + for j, cert := range c.Certificate { + x509Cert := c.Leaf + // Parse the certificate if this isn't the leaf node, or if + // chain.Leaf was nil. + if j != 0 || x509Cert == nil { + var err error + if x509Cert, err = x509.ParseCertificate(cert); err != nil { + return fmt.Errorf("failed to parse certificate #%d in the chain: %w", j, err) + } + } + + for _, ca := range cri.AcceptableCAs { + if bytes.Equal(x509Cert.RawIssuer, ca) { + return nil + } + } + } + return errors.New("chain is not signed by an acceptable CA") +} + +// BuildNameToCertificate parses c.Certificates and builds c.NameToCertificate +// from the CommonName and SubjectAlternateName fields of each of the leaf +// certificates. +// +// Deprecated: NameToCertificate only allows associating a single certificate +// with a given name. Leave that field nil to let the library select the first +// compatible chain from Certificates. +func (c *Config) BuildNameToCertificate() { + c.NameToCertificate = make(map[string]*Certificate) + for i := range c.Certificates { + cert := &c.Certificates[i] + x509Cert, err := cert.leaf() + if err != nil { + continue + } + // If SANs are *not* present, some clients will consider the certificate + // valid for the name in the Common Name. + if x509Cert.Subject.CommonName != "" && len(x509Cert.DNSNames) == 0 { + c.NameToCertificate[x509Cert.Subject.CommonName] = cert + } + for _, san := range x509Cert.DNSNames { + c.NameToCertificate[san] = cert + } + } +} + +const ( + keyLogLabelTLS12 = "CLIENT_RANDOM" + keyLogLabelClientHandshake = "CLIENT_HANDSHAKE_TRAFFIC_SECRET" + keyLogLabelServerHandshake = "SERVER_HANDSHAKE_TRAFFIC_SECRET" + keyLogLabelClientTraffic = "CLIENT_TRAFFIC_SECRET_0" + keyLogLabelServerTraffic = "SERVER_TRAFFIC_SECRET_0" +) + +func (c *Config) writeKeyLog(label string, clientRandom, secret []byte) error { + if c.KeyLogWriter == nil { + return nil + } + + logLine := []byte(fmt.Sprintf("%s %x %x\n", label, clientRandom, secret)) + + writerMutex.Lock() + _, err := c.KeyLogWriter.Write(logLine) + writerMutex.Unlock() + + return err +} + +// writerMutex protects all KeyLogWriters globally. It is rarely enabled, +// and is only for debugging, so a global mutex saves space. +var writerMutex sync.Mutex + +// A Certificate is a chain of one or more certificates, leaf first. +type Certificate struct { + Certificate [][]byte + // PrivateKey contains the private key corresponding to the public key in + // Leaf. This must implement crypto.Signer with an RSA, ECDSA or Ed25519 PublicKey. + // For a server up to TLS 1.2, it can also implement crypto.Decrypter with + // an RSA PublicKey. + PrivateKey crypto.PrivateKey + // SupportedSignatureAlgorithms is an optional list restricting what + // signature algorithms the PrivateKey can be used for. + SupportedSignatureAlgorithms []SignatureScheme + // OCSPStaple contains an optional OCSP response which will be served + // to clients that request it. + OCSPStaple []byte + // SignedCertificateTimestamps contains an optional list of Signed + // Certificate Timestamps which will be served to clients that request it. + SignedCertificateTimestamps [][]byte + // Leaf is the parsed form of the leaf certificate, which may be initialized + // using x509.ParseCertificate to reduce per-handshake processing. If nil, + // the leaf certificate will be parsed as needed. + Leaf *x509.Certificate +} + +// leaf returns the parsed leaf certificate, either from c.Leaf or by parsing +// the corresponding c.Certificate[0]. +func (c *Certificate) leaf() (*x509.Certificate, error) { + if c.Leaf != nil { + return c.Leaf, nil + } + return x509.ParseCertificate(c.Certificate[0]) +} + +type handshakeMessage interface { + marshal() []byte + unmarshal([]byte) bool +} + +// lruSessionCache is a ClientSessionCache implementation that uses an LRU +// caching strategy. +type lruSessionCache struct { + sync.Mutex + + m map[string]*list.Element + q *list.List + capacity int +} + +type lruSessionCacheEntry struct { + sessionKey string + state *ClientSessionState +} + +// NewLRUClientSessionCache returns a ClientSessionCache with the given +// capacity that uses an LRU strategy. If capacity is < 1, a default capacity +// is used instead. +func NewLRUClientSessionCache(capacity int) ClientSessionCache { + const defaultSessionCacheCapacity = 64 + + if capacity < 1 { + capacity = defaultSessionCacheCapacity + } + return &lruSessionCache{ + m: make(map[string]*list.Element), + q: list.New(), + capacity: capacity, + } +} + +// Put adds the provided (sessionKey, cs) pair to the cache. If cs is nil, the entry +// corresponding to sessionKey is removed from the cache instead. +func (c *lruSessionCache) Put(sessionKey string, cs *ClientSessionState) { + c.Lock() + defer c.Unlock() + + if elem, ok := c.m[sessionKey]; ok { + if cs == nil { + c.q.Remove(elem) + delete(c.m, sessionKey) + } else { + entry := elem.Value.(*lruSessionCacheEntry) + entry.state = cs + c.q.MoveToFront(elem) + } + return + } + + if c.q.Len() < c.capacity { + entry := &lruSessionCacheEntry{sessionKey, cs} + c.m[sessionKey] = c.q.PushFront(entry) + return + } + + elem := c.q.Back() + entry := elem.Value.(*lruSessionCacheEntry) + delete(c.m, entry.sessionKey) + entry.sessionKey = sessionKey + entry.state = cs + c.q.MoveToFront(elem) + c.m[sessionKey] = elem +} + +// Get returns the ClientSessionState value associated with a given key. It +// returns (nil, false) if no value is found. +func (c *lruSessionCache) Get(sessionKey string) (*ClientSessionState, bool) { + c.Lock() + defer c.Unlock() + + if elem, ok := c.m[sessionKey]; ok { + c.q.MoveToFront(elem) + return elem.Value.(*lruSessionCacheEntry).state, true + } + return nil, false +} + +var emptyConfig Config + +func defaultConfig() *Config { + return &emptyConfig +} + +func unexpectedMessageError(wanted, got any) error { + return fmt.Errorf("tls: received unexpected handshake message of type %T when waiting for %T", got, wanted) +} + +func isSupportedSignatureAlgorithm(sigAlg SignatureScheme, supportedSignatureAlgorithms []SignatureScheme) bool { + for _, s := range supportedSignatureAlgorithms { + if s == sigAlg { + return true + } + } + return false +} |