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Source file src/crypto/tls/common.go

Documentation: crypto/tls

     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.
     4  
     5  package tls
     6  
     7  import (
     8  	"container/list"
     9  	"crypto"
    10  	"crypto/internal/cipherhw"
    11  	"crypto/rand"
    12  	"crypto/sha512"
    13  	"crypto/x509"
    14  	"errors"
    15  	"fmt"
    16  	"io"
    17  	"math/big"
    18  	"net"
    19  	"strings"
    20  	"sync"
    21  	"time"
    22  )
    23  
    24  const (
    25  	VersionSSL30 = 0x0300
    26  	VersionTLS10 = 0x0301
    27  	VersionTLS11 = 0x0302
    28  	VersionTLS12 = 0x0303
    29  )
    30  
    31  const (
    32  	maxPlaintext      = 16384        // maximum plaintext payload length
    33  	maxCiphertext     = 16384 + 2048 // maximum ciphertext payload length
    34  	recordHeaderLen   = 5            // record header length
    35  	maxHandshake      = 65536        // maximum handshake we support (protocol max is 16 MB)
    36  	maxWarnAlertCount = 5            // maximum number of consecutive warning alerts
    37  
    38  	minVersion = VersionTLS10
    39  	maxVersion = VersionTLS12
    40  )
    41  
    42  // TLS record types.
    43  type recordType uint8
    44  
    45  const (
    46  	recordTypeChangeCipherSpec recordType = 20
    47  	recordTypeAlert            recordType = 21
    48  	recordTypeHandshake        recordType = 22
    49  	recordTypeApplicationData  recordType = 23
    50  )
    51  
    52  // TLS handshake message types.
    53  const (
    54  	typeHelloRequest       uint8 = 0
    55  	typeClientHello        uint8 = 1
    56  	typeServerHello        uint8 = 2
    57  	typeNewSessionTicket   uint8 = 4
    58  	typeCertificate        uint8 = 11
    59  	typeServerKeyExchange  uint8 = 12
    60  	typeCertificateRequest uint8 = 13
    61  	typeServerHelloDone    uint8 = 14
    62  	typeCertificateVerify  uint8 = 15
    63  	typeClientKeyExchange  uint8 = 16
    64  	typeFinished           uint8 = 20
    65  	typeCertificateStatus  uint8 = 22
    66  	typeNextProtocol       uint8 = 67 // Not IANA assigned
    67  )
    68  
    69  // TLS compression types.
    70  const (
    71  	compressionNone uint8 = 0
    72  )
    73  
    74  // TLS extension numbers
    75  const (
    76  	extensionServerName          uint16 = 0
    77  	extensionStatusRequest       uint16 = 5
    78  	extensionSupportedCurves     uint16 = 10
    79  	extensionSupportedPoints     uint16 = 11
    80  	extensionSignatureAlgorithms uint16 = 13
    81  	extensionALPN                uint16 = 16
    82  	extensionSCT                 uint16 = 18 // https://tools.ietf.org/html/rfc6962#section-6
    83  	extensionSessionTicket       uint16 = 35
    84  	extensionNextProtoNeg        uint16 = 13172 // not IANA assigned
    85  	extensionRenegotiationInfo   uint16 = 0xff01
    86  )
    87  
    88  // TLS signaling cipher suite values
    89  const (
    90  	scsvRenegotiation uint16 = 0x00ff
    91  )
    92  
    93  // CurveID is the type of a TLS identifier for an elliptic curve. See
    94  // http://www.iana.org/assignments/tls-parameters/tls-parameters.xml#tls-parameters-8
    95  type CurveID uint16
    96  
    97  const (
    98  	CurveP256 CurveID = 23
    99  	CurveP384 CurveID = 24
   100  	CurveP521 CurveID = 25
   101  	X25519    CurveID = 29
   102  )
   103  
   104  // TLS Elliptic Curve Point Formats
   105  // http://www.iana.org/assignments/tls-parameters/tls-parameters.xml#tls-parameters-9
   106  const (
   107  	pointFormatUncompressed uint8 = 0
   108  )
   109  
   110  // TLS CertificateStatusType (RFC 3546)
   111  const (
   112  	statusTypeOCSP uint8 = 1
   113  )
   114  
   115  // Certificate types (for certificateRequestMsg)
   116  const (
   117  	certTypeRSASign    = 1 // A certificate containing an RSA key
   118  	certTypeDSSSign    = 2 // A certificate containing a DSA key
   119  	certTypeRSAFixedDH = 3 // A certificate containing a static DH key
   120  	certTypeDSSFixedDH = 4 // A certificate containing a static DH key
   121  
   122  	// See RFC 4492 sections 3 and 5.5.
   123  	certTypeECDSASign      = 64 // A certificate containing an ECDSA-capable public key, signed with ECDSA.
   124  	certTypeRSAFixedECDH   = 65 // A certificate containing an ECDH-capable public key, signed with RSA.
   125  	certTypeECDSAFixedECDH = 66 // A certificate containing an ECDH-capable public key, signed with ECDSA.
   126  
   127  	// Rest of these are reserved by the TLS spec
   128  )
   129  
   130  // Signature algorithms for TLS 1.2 (See RFC 5246, section A.4.1)
   131  const (
   132  	signatureRSA   uint8 = 1
   133  	signatureECDSA uint8 = 3
   134  )
   135  
   136  // supportedSignatureAlgorithms contains the signature and hash algorithms that
   137  // the code advertises as supported in a TLS 1.2 ClientHello and in a TLS 1.2
   138  // CertificateRequest. The two fields are merged to match with TLS 1.3.
   139  // Note that in TLS 1.2, the ECDSA algorithms are not constrained to P-256, etc.
   140  var supportedSignatureAlgorithms = []SignatureScheme{
   141  	PKCS1WithSHA256,
   142  	ECDSAWithP256AndSHA256,
   143  	PKCS1WithSHA384,
   144  	ECDSAWithP384AndSHA384,
   145  	PKCS1WithSHA512,
   146  	ECDSAWithP521AndSHA512,
   147  	PKCS1WithSHA1,
   148  	ECDSAWithSHA1,
   149  }
   150  
   151  // ConnectionState records basic TLS details about the connection.
   152  type ConnectionState struct {
   153  	Version                     uint16                // TLS version used by the connection (e.g. VersionTLS12)
   154  	HandshakeComplete           bool                  // TLS handshake is complete
   155  	DidResume                   bool                  // connection resumes a previous TLS connection
   156  	CipherSuite                 uint16                // cipher suite in use (TLS_RSA_WITH_RC4_128_SHA, ...)
   157  	NegotiatedProtocol          string                // negotiated next protocol (not guaranteed to be from Config.NextProtos)
   158  	NegotiatedProtocolIsMutual  bool                  // negotiated protocol was advertised by server (client side only)
   159  	ServerName                  string                // server name requested by client, if any (server side only)
   160  	PeerCertificates            []*x509.Certificate   // certificate chain presented by remote peer
   161  	VerifiedChains              [][]*x509.Certificate // verified chains built from PeerCertificates
   162  	SignedCertificateTimestamps [][]byte              // SCTs from the server, if any
   163  	OCSPResponse                []byte                // stapled OCSP response from server, if any
   164  
   165  	// TLSUnique contains the "tls-unique" channel binding value (see RFC
   166  	// 5929, section 3). For resumed sessions this value will be nil
   167  	// because resumption does not include enough context (see
   168  	// https://mitls.org/pages/attacks/3SHAKE#channelbindings). This will
   169  	// change in future versions of Go once the TLS master-secret fix has
   170  	// been standardized and implemented.
   171  	TLSUnique []byte
   172  }
   173  
   174  // ClientAuthType declares the policy the server will follow for
   175  // TLS Client Authentication.
   176  type ClientAuthType int
   177  
   178  const (
   179  	NoClientCert ClientAuthType = iota
   180  	RequestClientCert
   181  	RequireAnyClientCert
   182  	VerifyClientCertIfGiven
   183  	RequireAndVerifyClientCert
   184  )
   185  
   186  // ClientSessionState contains the state needed by clients to resume TLS
   187  // sessions.
   188  type ClientSessionState struct {
   189  	sessionTicket      []uint8               // Encrypted ticket used for session resumption with server
   190  	vers               uint16                // SSL/TLS version negotiated for the session
   191  	cipherSuite        uint16                // Ciphersuite negotiated for the session
   192  	masterSecret       []byte                // MasterSecret generated by client on a full handshake
   193  	serverCertificates []*x509.Certificate   // Certificate chain presented by the server
   194  	verifiedChains     [][]*x509.Certificate // Certificate chains we built for verification
   195  }
   196  
   197  // ClientSessionCache is a cache of ClientSessionState objects that can be used
   198  // by a client to resume a TLS session with a given server. ClientSessionCache
   199  // implementations should expect to be called concurrently from different
   200  // goroutines. Only ticket-based resumption is supported, not SessionID-based
   201  // resumption.
   202  type ClientSessionCache interface {
   203  	// Get searches for a ClientSessionState associated with the given key.
   204  	// On return, ok is true if one was found.
   205  	Get(sessionKey string) (session *ClientSessionState, ok bool)
   206  
   207  	// Put adds the ClientSessionState to the cache with the given key.
   208  	Put(sessionKey string, cs *ClientSessionState)
   209  }
   210  
   211  // SignatureScheme identifies a signature algorithm supported by TLS. See
   212  // https://tools.ietf.org/html/draft-ietf-tls-tls13-18#section-4.2.3.
   213  type SignatureScheme uint16
   214  
   215  const (
   216  	PKCS1WithSHA1   SignatureScheme = 0x0201
   217  	PKCS1WithSHA256 SignatureScheme = 0x0401
   218  	PKCS1WithSHA384 SignatureScheme = 0x0501
   219  	PKCS1WithSHA512 SignatureScheme = 0x0601
   220  
   221  	PSSWithSHA256 SignatureScheme = 0x0804
   222  	PSSWithSHA384 SignatureScheme = 0x0805
   223  	PSSWithSHA512 SignatureScheme = 0x0806
   224  
   225  	ECDSAWithP256AndSHA256 SignatureScheme = 0x0403
   226  	ECDSAWithP384AndSHA384 SignatureScheme = 0x0503
   227  	ECDSAWithP521AndSHA512 SignatureScheme = 0x0603
   228  
   229  	// Legacy signature and hash algorithms for TLS 1.2.
   230  	ECDSAWithSHA1 SignatureScheme = 0x0203
   231  )
   232  
   233  // ClientHelloInfo contains information from a ClientHello message in order to
   234  // guide certificate selection in the GetCertificate callback.
   235  type ClientHelloInfo struct {
   236  	// CipherSuites lists the CipherSuites supported by the client (e.g.
   237  	// TLS_RSA_WITH_RC4_128_SHA).
   238  	CipherSuites []uint16
   239  
   240  	// ServerName indicates the name of the server requested by the client
   241  	// in order to support virtual hosting. ServerName is only set if the
   242  	// client is using SNI (see
   243  	// http://tools.ietf.org/html/rfc4366#section-3.1).
   244  	ServerName string
   245  
   246  	// SupportedCurves lists the elliptic curves supported by the client.
   247  	// SupportedCurves is set only if the Supported Elliptic Curves
   248  	// Extension is being used (see
   249  	// http://tools.ietf.org/html/rfc4492#section-5.1.1).
   250  	SupportedCurves []CurveID
   251  
   252  	// SupportedPoints lists the point formats supported by the client.
   253  	// SupportedPoints is set only if the Supported Point Formats Extension
   254  	// is being used (see
   255  	// http://tools.ietf.org/html/rfc4492#section-5.1.2).
   256  	SupportedPoints []uint8
   257  
   258  	// SignatureSchemes lists the signature and hash schemes that the client
   259  	// is willing to verify. SignatureSchemes is set only if the Signature
   260  	// Algorithms Extension is being used (see
   261  	// https://tools.ietf.org/html/rfc5246#section-7.4.1.4.1).
   262  	SignatureSchemes []SignatureScheme
   263  
   264  	// SupportedProtos lists the application protocols supported by the client.
   265  	// SupportedProtos is set only if the Application-Layer Protocol
   266  	// Negotiation Extension is being used (see
   267  	// https://tools.ietf.org/html/rfc7301#section-3.1).
   268  	//
   269  	// Servers can select a protocol by setting Config.NextProtos in a
   270  	// GetConfigForClient return value.
   271  	SupportedProtos []string
   272  
   273  	// SupportedVersions lists the TLS versions supported by the client.
   274  	// For TLS versions less than 1.3, this is extrapolated from the max
   275  	// version advertised by the client, so values other than the greatest
   276  	// might be rejected if used.
   277  	SupportedVersions []uint16
   278  
   279  	// Conn is the underlying net.Conn for the connection. Do not read
   280  	// from, or write to, this connection; that will cause the TLS
   281  	// connection to fail.
   282  	Conn net.Conn
   283  }
   284  
   285  // CertificateRequestInfo contains information from a server's
   286  // CertificateRequest message, which is used to demand a certificate and proof
   287  // of control from a client.
   288  type CertificateRequestInfo struct {
   289  	// AcceptableCAs contains zero or more, DER-encoded, X.501
   290  	// Distinguished Names. These are the names of root or intermediate CAs
   291  	// that the server wishes the returned certificate to be signed by. An
   292  	// empty slice indicates that the server has no preference.
   293  	AcceptableCAs [][]byte
   294  
   295  	// SignatureSchemes lists the signature schemes that the server is
   296  	// willing to verify.
   297  	SignatureSchemes []SignatureScheme
   298  }
   299  
   300  // RenegotiationSupport enumerates the different levels of support for TLS
   301  // renegotiation. TLS renegotiation is the act of performing subsequent
   302  // handshakes on a connection after the first. This significantly complicates
   303  // the state machine and has been the source of numerous, subtle security
   304  // issues. Initiating a renegotiation is not supported, but support for
   305  // accepting renegotiation requests may be enabled.
   306  //
   307  // Even when enabled, the server may not change its identity between handshakes
   308  // (i.e. the leaf certificate must be the same). Additionally, concurrent
   309  // handshake and application data flow is not permitted so renegotiation can
   310  // only be used with protocols that synchronise with the renegotiation, such as
   311  // HTTPS.
   312  type RenegotiationSupport int
   313  
   314  const (
   315  	// RenegotiateNever disables renegotiation.
   316  	RenegotiateNever RenegotiationSupport = iota
   317  
   318  	// RenegotiateOnceAsClient allows a remote server to request
   319  	// renegotiation once per connection.
   320  	RenegotiateOnceAsClient
   321  
   322  	// RenegotiateFreelyAsClient allows a remote server to repeatedly
   323  	// request renegotiation.
   324  	RenegotiateFreelyAsClient
   325  )
   326  
   327  // A Config structure is used to configure a TLS client or server.
   328  // After one has been passed to a TLS function it must not be
   329  // modified. A Config may be reused; the tls package will also not
   330  // modify it.
   331  type Config struct {
   332  	// Rand provides the source of entropy for nonces and RSA blinding.
   333  	// If Rand is nil, TLS uses the cryptographic random reader in package
   334  	// crypto/rand.
   335  	// The Reader must be safe for use by multiple goroutines.
   336  	Rand io.Reader
   337  
   338  	// Time returns the current time as the number of seconds since the epoch.
   339  	// If Time is nil, TLS uses time.Now.
   340  	Time func() time.Time
   341  
   342  	// Certificates contains one or more certificate chains to present to
   343  	// the other side of the connection. Server configurations must include
   344  	// at least one certificate or else set GetCertificate. Clients doing
   345  	// client-authentication may set either Certificates or
   346  	// GetClientCertificate.
   347  	Certificates []Certificate
   348  
   349  	// NameToCertificate maps from a certificate name to an element of
   350  	// Certificates. Note that a certificate name can be of the form
   351  	// '*.example.com' and so doesn't have to be a domain name as such.
   352  	// See Config.BuildNameToCertificate
   353  	// The nil value causes the first element of Certificates to be used
   354  	// for all connections.
   355  	NameToCertificate map[string]*Certificate
   356  
   357  	// GetCertificate returns a Certificate based on the given
   358  	// ClientHelloInfo. It will only be called if the client supplies SNI
   359  	// information or if Certificates is empty.
   360  	//
   361  	// If GetCertificate is nil or returns nil, then the certificate is
   362  	// retrieved from NameToCertificate. If NameToCertificate is nil, the
   363  	// first element of Certificates will be used.
   364  	GetCertificate func(*ClientHelloInfo) (*Certificate, error)
   365  
   366  	// GetClientCertificate, if not nil, is called when a server requests a
   367  	// certificate from a client. If set, the contents of Certificates will
   368  	// be ignored.
   369  	//
   370  	// If GetClientCertificate returns an error, the handshake will be
   371  	// aborted and that error will be returned. Otherwise
   372  	// GetClientCertificate must return a non-nil Certificate. If
   373  	// Certificate.Certificate is empty then no certificate will be sent to
   374  	// the server. If this is unacceptable to the server then it may abort
   375  	// the handshake.
   376  	//
   377  	// GetClientCertificate may be called multiple times for the same
   378  	// connection if renegotiation occurs or if TLS 1.3 is in use.
   379  	GetClientCertificate func(*CertificateRequestInfo) (*Certificate, error)
   380  
   381  	// GetConfigForClient, if not nil, is called after a ClientHello is
   382  	// received from a client. It may return a non-nil Config in order to
   383  	// change the Config that will be used to handle this connection. If
   384  	// the returned Config is nil, the original Config will be used. The
   385  	// Config returned by this callback may not be subsequently modified.
   386  	//
   387  	// If GetConfigForClient is nil, the Config passed to Server() will be
   388  	// used for all connections.
   389  	//
   390  	// Uniquely for the fields in the returned Config, session ticket keys
   391  	// will be duplicated from the original Config if not set.
   392  	// Specifically, if SetSessionTicketKeys was called on the original
   393  	// config but not on the returned config then the ticket keys from the
   394  	// original config will be copied into the new config before use.
   395  	// Otherwise, if SessionTicketKey was set in the original config but
   396  	// not in the returned config then it will be copied into the returned
   397  	// config before use. If neither of those cases applies then the key
   398  	// material from the returned config will be used for session tickets.
   399  	GetConfigForClient func(*ClientHelloInfo) (*Config, error)
   400  
   401  	// VerifyPeerCertificate, if not nil, is called after normal
   402  	// certificate verification by either a TLS client or server. It
   403  	// receives the raw ASN.1 certificates provided by the peer and also
   404  	// any verified chains that normal processing found. If it returns a
   405  	// non-nil error, the handshake is aborted and that error results.
   406  	//
   407  	// If normal verification fails then the handshake will abort before
   408  	// considering this callback. If normal verification is disabled by
   409  	// setting InsecureSkipVerify, or (for a server) when ClientAuth is
   410  	// RequestClientCert or RequireAnyClientCert, then this callback will
   411  	// be considered but the verifiedChains argument will always be nil.
   412  	VerifyPeerCertificate func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error
   413  
   414  	// RootCAs defines the set of root certificate authorities
   415  	// that clients use when verifying server certificates.
   416  	// If RootCAs is nil, TLS uses the host's root CA set.
   417  	RootCAs *x509.CertPool
   418  
   419  	// NextProtos is a list of supported, application level protocols.
   420  	NextProtos []string
   421  
   422  	// ServerName is used to verify the hostname on the returned
   423  	// certificates unless InsecureSkipVerify is given. It is also included
   424  	// in the client's handshake to support virtual hosting unless it is
   425  	// an IP address.
   426  	ServerName string
   427  
   428  	// ClientAuth determines the server's policy for
   429  	// TLS Client Authentication. The default is NoClientCert.
   430  	ClientAuth ClientAuthType
   431  
   432  	// ClientCAs defines the set of root certificate authorities
   433  	// that servers use if required to verify a client certificate
   434  	// by the policy in ClientAuth.
   435  	ClientCAs *x509.CertPool
   436  
   437  	// InsecureSkipVerify controls whether a client verifies the
   438  	// server's certificate chain and host name.
   439  	// If InsecureSkipVerify is true, TLS accepts any certificate
   440  	// presented by the server and any host name in that certificate.
   441  	// In this mode, TLS is susceptible to man-in-the-middle attacks.
   442  	// This should be used only for testing.
   443  	InsecureSkipVerify bool
   444  
   445  	// CipherSuites is a list of supported cipher suites. If CipherSuites
   446  	// is nil, TLS uses a list of suites supported by the implementation.
   447  	CipherSuites []uint16
   448  
   449  	// PreferServerCipherSuites controls whether the server selects the
   450  	// client's most preferred ciphersuite, or the server's most preferred
   451  	// ciphersuite. If true then the server's preference, as expressed in
   452  	// the order of elements in CipherSuites, is used.
   453  	PreferServerCipherSuites bool
   454  
   455  	// SessionTicketsDisabled may be set to true to disable session ticket
   456  	// (resumption) support.
   457  	SessionTicketsDisabled bool
   458  
   459  	// SessionTicketKey is used by TLS servers to provide session
   460  	// resumption. See RFC 5077. If zero, it will be filled with
   461  	// random data before the first server handshake.
   462  	//
   463  	// If multiple servers are terminating connections for the same host
   464  	// they should all have the same SessionTicketKey. If the
   465  	// SessionTicketKey leaks, previously recorded and future TLS
   466  	// connections using that key are compromised.
   467  	SessionTicketKey [32]byte
   468  
   469  	// ClientSessionCache is a cache of ClientSessionState entries for TLS
   470  	// session resumption.
   471  	ClientSessionCache ClientSessionCache
   472  
   473  	// MinVersion contains the minimum SSL/TLS version that is acceptable.
   474  	// If zero, then TLS 1.0 is taken as the minimum.
   475  	MinVersion uint16
   476  
   477  	// MaxVersion contains the maximum SSL/TLS version that is acceptable.
   478  	// If zero, then the maximum version supported by this package is used,
   479  	// which is currently TLS 1.2.
   480  	MaxVersion uint16
   481  
   482  	// CurvePreferences contains the elliptic curves that will be used in
   483  	// an ECDHE handshake, in preference order. If empty, the default will
   484  	// be used.
   485  	CurvePreferences []CurveID
   486  
   487  	// DynamicRecordSizingDisabled disables adaptive sizing of TLS records.
   488  	// When true, the largest possible TLS record size is always used. When
   489  	// false, the size of TLS records may be adjusted in an attempt to
   490  	// improve latency.
   491  	DynamicRecordSizingDisabled bool
   492  
   493  	// Renegotiation controls what types of renegotiation are supported.
   494  	// The default, none, is correct for the vast majority of applications.
   495  	Renegotiation RenegotiationSupport
   496  
   497  	// KeyLogWriter optionally specifies a destination for TLS master secrets
   498  	// in NSS key log format that can be used to allow external programs
   499  	// such as Wireshark to decrypt TLS connections.
   500  	// See https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/Key_Log_Format.
   501  	// Use of KeyLogWriter compromises security and should only be
   502  	// used for debugging.
   503  	KeyLogWriter io.Writer
   504  
   505  	serverInitOnce sync.Once // guards calling (*Config).serverInit
   506  
   507  	// mutex protects sessionTicketKeys.
   508  	mutex sync.RWMutex
   509  	// sessionTicketKeys contains zero or more ticket keys. If the length
   510  	// is zero, SessionTicketsDisabled must be true. The first key is used
   511  	// for new tickets and any subsequent keys can be used to decrypt old
   512  	// tickets.
   513  	sessionTicketKeys []ticketKey
   514  }
   515  
   516  // ticketKeyNameLen is the number of bytes of identifier that is prepended to
   517  // an encrypted session ticket in order to identify the key used to encrypt it.
   518  const ticketKeyNameLen = 16
   519  
   520  // ticketKey is the internal representation of a session ticket key.
   521  type ticketKey struct {
   522  	// keyName is an opaque byte string that serves to identify the session
   523  	// ticket key. It's exposed as plaintext in every session ticket.
   524  	keyName [ticketKeyNameLen]byte
   525  	aesKey  [16]byte
   526  	hmacKey [16]byte
   527  }
   528  
   529  // ticketKeyFromBytes converts from the external representation of a session
   530  // ticket key to a ticketKey. Externally, session ticket keys are 32 random
   531  // bytes and this function expands that into sufficient name and key material.
   532  func ticketKeyFromBytes(b [32]byte) (key ticketKey) {
   533  	hashed := sha512.Sum512(b[:])
   534  	copy(key.keyName[:], hashed[:ticketKeyNameLen])
   535  	copy(key.aesKey[:], hashed[ticketKeyNameLen:ticketKeyNameLen+16])
   536  	copy(key.hmacKey[:], hashed[ticketKeyNameLen+16:ticketKeyNameLen+32])
   537  	return key
   538  }
   539  
   540  // Clone returns a shallow clone of c. It is safe to clone a Config that is
   541  // being used concurrently by a TLS client or server.
   542  func (c *Config) Clone() *Config {
   543  	// Running serverInit ensures that it's safe to read
   544  	// SessionTicketsDisabled.
   545  	c.serverInitOnce.Do(func() { c.serverInit(nil) })
   546  
   547  	var sessionTicketKeys []ticketKey
   548  	c.mutex.RLock()
   549  	sessionTicketKeys = c.sessionTicketKeys
   550  	c.mutex.RUnlock()
   551  
   552  	return &Config{
   553  		Rand:                        c.Rand,
   554  		Time:                        c.Time,
   555  		Certificates:                c.Certificates,
   556  		NameToCertificate:           c.NameToCertificate,
   557  		GetCertificate:              c.GetCertificate,
   558  		GetClientCertificate:        c.GetClientCertificate,
   559  		GetConfigForClient:          c.GetConfigForClient,
   560  		VerifyPeerCertificate:       c.VerifyPeerCertificate,
   561  		RootCAs:                     c.RootCAs,
   562  		NextProtos:                  c.NextProtos,
   563  		ServerName:                  c.ServerName,
   564  		ClientAuth:                  c.ClientAuth,
   565  		ClientCAs:                   c.ClientCAs,
   566  		InsecureSkipVerify:          c.InsecureSkipVerify,
   567  		CipherSuites:                c.CipherSuites,
   568  		PreferServerCipherSuites:    c.PreferServerCipherSuites,
   569  		SessionTicketsDisabled:      c.SessionTicketsDisabled,
   570  		SessionTicketKey:            c.SessionTicketKey,
   571  		ClientSessionCache:          c.ClientSessionCache,
   572  		MinVersion:                  c.MinVersion,
   573  		MaxVersion:                  c.MaxVersion,
   574  		CurvePreferences:            c.CurvePreferences,
   575  		DynamicRecordSizingDisabled: c.DynamicRecordSizingDisabled,
   576  		Renegotiation:               c.Renegotiation,
   577  		KeyLogWriter:                c.KeyLogWriter,
   578  		sessionTicketKeys:           sessionTicketKeys,
   579  	}
   580  }
   581  
   582  // serverInit is run under c.serverInitOnce to do initialization of c. If c was
   583  // returned by a GetConfigForClient callback then the argument should be the
   584  // Config that was passed to Server, otherwise it should be nil.
   585  func (c *Config) serverInit(originalConfig *Config) {
   586  	if c.SessionTicketsDisabled || len(c.ticketKeys()) != 0 {
   587  		return
   588  	}
   589  
   590  	alreadySet := false
   591  	for _, b := range c.SessionTicketKey {
   592  		if b != 0 {
   593  			alreadySet = true
   594  			break
   595  		}
   596  	}
   597  
   598  	if !alreadySet {
   599  		if originalConfig != nil {
   600  			copy(c.SessionTicketKey[:], originalConfig.SessionTicketKey[:])
   601  		} else if _, err := io.ReadFull(c.rand(), c.SessionTicketKey[:]); err != nil {
   602  			c.SessionTicketsDisabled = true
   603  			return
   604  		}
   605  	}
   606  
   607  	if originalConfig != nil {
   608  		originalConfig.mutex.RLock()
   609  		c.sessionTicketKeys = originalConfig.sessionTicketKeys
   610  		originalConfig.mutex.RUnlock()
   611  	} else {
   612  		c.sessionTicketKeys = []ticketKey{ticketKeyFromBytes(c.SessionTicketKey)}
   613  	}
   614  }
   615  
   616  func (c *Config) ticketKeys() []ticketKey {
   617  	c.mutex.RLock()
   618  	// c.sessionTicketKeys is constant once created. SetSessionTicketKeys
   619  	// will only update it by replacing it with a new value.
   620  	ret := c.sessionTicketKeys
   621  	c.mutex.RUnlock()
   622  	return ret
   623  }
   624  
   625  // SetSessionTicketKeys updates the session ticket keys for a server. The first
   626  // key will be used when creating new tickets, while all keys can be used for
   627  // decrypting tickets. It is safe to call this function while the server is
   628  // running in order to rotate the session ticket keys. The function will panic
   629  // if keys is empty.
   630  func (c *Config) SetSessionTicketKeys(keys [][32]byte) {
   631  	if len(keys) == 0 {
   632  		panic("tls: keys must have at least one key")
   633  	}
   634  
   635  	newKeys := make([]ticketKey, len(keys))
   636  	for i, bytes := range keys {
   637  		newKeys[i] = ticketKeyFromBytes(bytes)
   638  	}
   639  
   640  	c.mutex.Lock()
   641  	c.sessionTicketKeys = newKeys
   642  	c.mutex.Unlock()
   643  }
   644  
   645  func (c *Config) rand() io.Reader {
   646  	r := c.Rand
   647  	if r == nil {
   648  		return rand.Reader
   649  	}
   650  	return r
   651  }
   652  
   653  func (c *Config) time() time.Time {
   654  	t := c.Time
   655  	if t == nil {
   656  		t = time.Now
   657  	}
   658  	return t()
   659  }
   660  
   661  func (c *Config) cipherSuites() []uint16 {
   662  	s := c.CipherSuites
   663  	if s == nil {
   664  		s = defaultCipherSuites()
   665  	}
   666  	return s
   667  }
   668  
   669  func (c *Config) minVersion() uint16 {
   670  	if c == nil || c.MinVersion == 0 {
   671  		return minVersion
   672  	}
   673  	return c.MinVersion
   674  }
   675  
   676  func (c *Config) maxVersion() uint16 {
   677  	if c == nil || c.MaxVersion == 0 {
   678  		return maxVersion
   679  	}
   680  	return c.MaxVersion
   681  }
   682  
   683  var defaultCurvePreferences = []CurveID{X25519, CurveP256, CurveP384, CurveP521}
   684  
   685  func (c *Config) curvePreferences() []CurveID {
   686  	if c == nil || len(c.CurvePreferences) == 0 {
   687  		return defaultCurvePreferences
   688  	}
   689  	return c.CurvePreferences
   690  }
   691  
   692  // mutualVersion returns the protocol version to use given the advertised
   693  // version of the peer.
   694  func (c *Config) mutualVersion(vers uint16) (uint16, bool) {
   695  	minVersion := c.minVersion()
   696  	maxVersion := c.maxVersion()
   697  
   698  	if vers < minVersion {
   699  		return 0, false
   700  	}
   701  	if vers > maxVersion {
   702  		vers = maxVersion
   703  	}
   704  	return vers, true
   705  }
   706  
   707  // getCertificate returns the best certificate for the given ClientHelloInfo,
   708  // defaulting to the first element of c.Certificates.
   709  func (c *Config) getCertificate(clientHello *ClientHelloInfo) (*Certificate, error) {
   710  	if c.GetCertificate != nil &&
   711  		(len(c.Certificates) == 0 || len(clientHello.ServerName) > 0) {
   712  		cert, err := c.GetCertificate(clientHello)
   713  		if cert != nil || err != nil {
   714  			return cert, err
   715  		}
   716  	}
   717  
   718  	if len(c.Certificates) == 0 {
   719  		return nil, errors.New("tls: no certificates configured")
   720  	}
   721  
   722  	if len(c.Certificates) == 1 || c.NameToCertificate == nil {
   723  		// There's only one choice, so no point doing any work.
   724  		return &c.Certificates[0], nil
   725  	}
   726  
   727  	name := strings.ToLower(clientHello.ServerName)
   728  	for len(name) > 0 && name[len(name)-1] == '.' {
   729  		name = name[:len(name)-1]
   730  	}
   731  
   732  	if cert, ok := c.NameToCertificate[name]; ok {
   733  		return cert, nil
   734  	}
   735  
   736  	// try replacing labels in the name with wildcards until we get a
   737  	// match.
   738  	labels := strings.Split(name, ".")
   739  	for i := range labels {
   740  		labels[i] = "*"
   741  		candidate := strings.Join(labels, ".")
   742  		if cert, ok := c.NameToCertificate[candidate]; ok {
   743  			return cert, nil
   744  		}
   745  	}
   746  
   747  	// If nothing matches, return the first certificate.
   748  	return &c.Certificates[0], nil
   749  }
   750  
   751  // BuildNameToCertificate parses c.Certificates and builds c.NameToCertificate
   752  // from the CommonName and SubjectAlternateName fields of each of the leaf
   753  // certificates.
   754  func (c *Config) BuildNameToCertificate() {
   755  	c.NameToCertificate = make(map[string]*Certificate)
   756  	for i := range c.Certificates {
   757  		cert := &c.Certificates[i]
   758  		x509Cert, err := x509.ParseCertificate(cert.Certificate[0])
   759  		if err != nil {
   760  			continue
   761  		}
   762  		if len(x509Cert.Subject.CommonName) > 0 {
   763  			c.NameToCertificate[x509Cert.Subject.CommonName] = cert
   764  		}
   765  		for _, san := range x509Cert.DNSNames {
   766  			c.NameToCertificate[san] = cert
   767  		}
   768  	}
   769  }
   770  
   771  // writeKeyLog logs client random and master secret if logging was enabled by
   772  // setting c.KeyLogWriter.
   773  func (c *Config) writeKeyLog(clientRandom, masterSecret []byte) error {
   774  	if c.KeyLogWriter == nil {
   775  		return nil
   776  	}
   777  
   778  	logLine := []byte(fmt.Sprintf("CLIENT_RANDOM %x %x\n", clientRandom, masterSecret))
   779  
   780  	writerMutex.Lock()
   781  	_, err := c.KeyLogWriter.Write(logLine)
   782  	writerMutex.Unlock()
   783  
   784  	return err
   785  }
   786  
   787  // writerMutex protects all KeyLogWriters globally. It is rarely enabled,
   788  // and is only for debugging, so a global mutex saves space.
   789  var writerMutex sync.Mutex
   790  
   791  // A Certificate is a chain of one or more certificates, leaf first.
   792  type Certificate struct {
   793  	Certificate [][]byte
   794  	// PrivateKey contains the private key corresponding to the public key
   795  	// in Leaf. For a server, this must implement crypto.Signer and/or
   796  	// crypto.Decrypter, with an RSA or ECDSA PublicKey. For a client
   797  	// (performing client authentication), this must be a crypto.Signer
   798  	// with an RSA or ECDSA PublicKey.
   799  	PrivateKey crypto.PrivateKey
   800  	// OCSPStaple contains an optional OCSP response which will be served
   801  	// to clients that request it.
   802  	OCSPStaple []byte
   803  	// SignedCertificateTimestamps contains an optional list of Signed
   804  	// Certificate Timestamps which will be served to clients that request it.
   805  	SignedCertificateTimestamps [][]byte
   806  	// Leaf is the parsed form of the leaf certificate, which may be
   807  	// initialized using x509.ParseCertificate to reduce per-handshake
   808  	// processing for TLS clients doing client authentication. If nil, the
   809  	// leaf certificate will be parsed as needed.
   810  	Leaf *x509.Certificate
   811  }
   812  
   813  type handshakeMessage interface {
   814  	marshal() []byte
   815  	unmarshal([]byte) bool
   816  }
   817  
   818  // lruSessionCache is a ClientSessionCache implementation that uses an LRU
   819  // caching strategy.
   820  type lruSessionCache struct {
   821  	sync.Mutex
   822  
   823  	m        map[string]*list.Element
   824  	q        *list.List
   825  	capacity int
   826  }
   827  
   828  type lruSessionCacheEntry struct {
   829  	sessionKey string
   830  	state      *ClientSessionState
   831  }
   832  
   833  // NewLRUClientSessionCache returns a ClientSessionCache with the given
   834  // capacity that uses an LRU strategy. If capacity is < 1, a default capacity
   835  // is used instead.
   836  func NewLRUClientSessionCache(capacity int) ClientSessionCache {
   837  	const defaultSessionCacheCapacity = 64
   838  
   839  	if capacity < 1 {
   840  		capacity = defaultSessionCacheCapacity
   841  	}
   842  	return &lruSessionCache{
   843  		m:        make(map[string]*list.Element),
   844  		q:        list.New(),
   845  		capacity: capacity,
   846  	}
   847  }
   848  
   849  // Put adds the provided (sessionKey, cs) pair to the cache.
   850  func (c *lruSessionCache) Put(sessionKey string, cs *ClientSessionState) {
   851  	c.Lock()
   852  	defer c.Unlock()
   853  
   854  	if elem, ok := c.m[sessionKey]; ok {
   855  		entry := elem.Value.(*lruSessionCacheEntry)
   856  		entry.state = cs
   857  		c.q.MoveToFront(elem)
   858  		return
   859  	}
   860  
   861  	if c.q.Len() < c.capacity {
   862  		entry := &lruSessionCacheEntry{sessionKey, cs}
   863  		c.m[sessionKey] = c.q.PushFront(entry)
   864  		return
   865  	}
   866  
   867  	elem := c.q.Back()
   868  	entry := elem.Value.(*lruSessionCacheEntry)
   869  	delete(c.m, entry.sessionKey)
   870  	entry.sessionKey = sessionKey
   871  	entry.state = cs
   872  	c.q.MoveToFront(elem)
   873  	c.m[sessionKey] = elem
   874  }
   875  
   876  // Get returns the ClientSessionState value associated with a given key. It
   877  // returns (nil, false) if no value is found.
   878  func (c *lruSessionCache) Get(sessionKey string) (*ClientSessionState, bool) {
   879  	c.Lock()
   880  	defer c.Unlock()
   881  
   882  	if elem, ok := c.m[sessionKey]; ok {
   883  		c.q.MoveToFront(elem)
   884  		return elem.Value.(*lruSessionCacheEntry).state, true
   885  	}
   886  	return nil, false
   887  }
   888  
   889  // TODO(jsing): Make these available to both crypto/x509 and crypto/tls.
   890  type dsaSignature struct {
   891  	R, S *big.Int
   892  }
   893  
   894  type ecdsaSignature dsaSignature
   895  
   896  var emptyConfig Config
   897  
   898  func defaultConfig() *Config {
   899  	return &emptyConfig
   900  }
   901  
   902  var (
   903  	once                   sync.Once
   904  	varDefaultCipherSuites []uint16
   905  )
   906  
   907  func defaultCipherSuites() []uint16 {
   908  	once.Do(initDefaultCipherSuites)
   909  	return varDefaultCipherSuites
   910  }
   911  
   912  func initDefaultCipherSuites() {
   913  	var topCipherSuites []uint16
   914  	if cipherhw.AESGCMSupport() {
   915  		// If AES-GCM hardware is provided then prioritise AES-GCM
   916  		// cipher suites.
   917  		topCipherSuites = []uint16{
   918  			TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
   919  			TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
   920  			TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
   921  			TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
   922  			TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
   923  			TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
   924  		}
   925  	} else {
   926  		// Without AES-GCM hardware, we put the ChaCha20-Poly1305
   927  		// cipher suites first.
   928  		topCipherSuites = []uint16{
   929  			TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
   930  			TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
   931  			TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
   932  			TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
   933  			TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
   934  			TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
   935  		}
   936  	}
   937  
   938  	varDefaultCipherSuites = make([]uint16, 0, len(cipherSuites))
   939  	varDefaultCipherSuites = append(varDefaultCipherSuites, topCipherSuites...)
   940  
   941  NextCipherSuite:
   942  	for _, suite := range cipherSuites {
   943  		if suite.flags&suiteDefaultOff != 0 {
   944  			continue
   945  		}
   946  		for _, existing := range varDefaultCipherSuites {
   947  			if existing == suite.id {
   948  				continue NextCipherSuite
   949  			}
   950  		}
   951  		varDefaultCipherSuites = append(varDefaultCipherSuites, suite.id)
   952  	}
   953  }
   954  
   955  func unexpectedMessageError(wanted, got interface{}) error {
   956  	return fmt.Errorf("tls: received unexpected handshake message of type %T when waiting for %T", got, wanted)
   957  }
   958  
   959  func isSupportedSignatureAlgorithm(sigAlg SignatureScheme, supportedSignatureAlgorithms []SignatureScheme) bool {
   960  	for _, s := range supportedSignatureAlgorithms {
   961  		if s == sigAlg {
   962  			return true
   963  		}
   964  	}
   965  	return false
   966  }
   967  
   968  // signatureFromSignatureScheme maps a signature algorithm to the underlying
   969  // signature method (without hash function).
   970  func signatureFromSignatureScheme(signatureAlgorithm SignatureScheme) uint8 {
   971  	switch signatureAlgorithm {
   972  	case PKCS1WithSHA1, PKCS1WithSHA256, PKCS1WithSHA384, PKCS1WithSHA512:
   973  		return signatureRSA
   974  	case ECDSAWithSHA1, ECDSAWithP256AndSHA256, ECDSAWithP384AndSHA384, ECDSAWithP521AndSHA512:
   975  		return signatureECDSA
   976  	default:
   977  		return 0
   978  	}
   979  }
   980  

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