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package tls

import ""

Package tls partially implements TLS 1.2, as specified in RFC 5246, and TLS 1.3, as specified in RFC 8446.


Package Files

alert.go auth.go cipher_suites.go common.go conn.go handshake_client.go handshake_client_tls13.go handshake_messages.go handshake_server.go handshake_server_tls13.go key_agreement.go key_schedule.go prf.go ticket.go tls.go u_common.go u_conn.go u_parrots.go u_public.go u_roller.go u_tls_extensions.go


const (
    // TLS 1.0 - 1.2 cipher suites.
    TLS_RSA_WITH_RC4_128_SHA                uint16 = 0x0005
    TLS_RSA_WITH_3DES_EDE_CBC_SHA           uint16 = 0x000a
    TLS_RSA_WITH_AES_128_CBC_SHA            uint16 = 0x002f
    TLS_RSA_WITH_AES_256_CBC_SHA            uint16 = 0x0035
    TLS_RSA_WITH_AES_128_CBC_SHA256         uint16 = 0x003c
    TLS_RSA_WITH_AES_128_GCM_SHA256         uint16 = 0x009c
    TLS_RSA_WITH_AES_256_GCM_SHA384         uint16 = 0x009d
    TLS_ECDHE_ECDSA_WITH_RC4_128_SHA        uint16 = 0xc007
    TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA    uint16 = 0xc009
    TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA    uint16 = 0xc00a
    TLS_ECDHE_RSA_WITH_RC4_128_SHA          uint16 = 0xc011
    TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA     uint16 = 0xc012
    TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA      uint16 = 0xc013
    TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA      uint16 = 0xc014
    TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 uint16 = 0xc023
    TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256   uint16 = 0xc027
    TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256   uint16 = 0xc02f
    TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 uint16 = 0xc02b
    TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384   uint16 = 0xc030
    TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 uint16 = 0xc02c
    TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305    uint16 = 0xcca8
    TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305  uint16 = 0xcca9

    // TLS 1.3 cipher suites.
    TLS_AES_128_GCM_SHA256       uint16 = 0x1301
    TLS_AES_256_GCM_SHA384       uint16 = 0x1302
    TLS_CHACHA20_POLY1305_SHA256 uint16 = 0x1303

    // TLS_FALLBACK_SCSV isn't a standard cipher suite but an indicator
    // that the client is doing version fallback. See RFC 7507.
    TLS_FALLBACK_SCSV uint16 = 0x5600

A list of cipher suite IDs that are, or have been, implemented by this package.

Taken from

const (
    VersionSSL30 = 0x0300
    VersionTLS10 = 0x0301
    VersionTLS11 = 0x0302
    VersionTLS12 = 0x0303
    VersionTLS13 = 0x0304
const (
    OLD_TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256   = uint16(0xcc13)
    OLD_TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 = uint16(0xcc14)

    DISABLED_TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 = uint16(0xc024)
    DISABLED_TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384   = uint16(0xc028)
    DISABLED_TLS_RSA_WITH_AES_256_CBC_SHA256         = uint16(0x003d)

    FAKE_OLD_TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256 = uint16(0xcc15) // we can try to craft these ciphersuites
    FAKE_TLS_DHE_RSA_WITH_AES_128_GCM_SHA256           = uint16(0x009e) // from existing pieces, if needed

    FAKE_TLS_DHE_RSA_WITH_AES_128_CBC_SHA  = uint16(0x0033)
    FAKE_TLS_DHE_RSA_WITH_AES_256_CBC_SHA  = uint16(0x0039)
    FAKE_TLS_RSA_WITH_RC4_128_MD5          = uint16(0x0004)

based on spec's GreaseStyle, GREASE_PLACEHOLDER may be replaced by another GREASE value


var (
    FakeFFDHE2048 = uint16(0x0100)
    FakeFFDHE3072 = uint16(0x0101)

fake curves(groups)

var (
    // HelloGolang will use default "crypto/tls" handshake marshaling codepath, which WILL
    // overwrite your changes to Hello(Config, Session are fine).
    // You might want to call BuildHandshakeState() before applying any changes.
    // UConn.Extensions will be completely ignored.
    HelloGolang = ClientHelloID{helloGolang, helloAutoVers}

    // HelloCustom will prepare ClientHello with empty uconn.Extensions so you can fill it with
    // TLSExtensions manually or use ApplyPreset function
    HelloCustom = ClientHelloID{helloCustom, helloAutoVers}

    // HelloRandomized* randomly adds/reorders extensions, ciphersuites, etc.
    HelloRandomized       = ClientHelloID{helloRandomized, helloAutoVers}
    HelloRandomizedALPN   = ClientHelloID{helloRandomized, helloRandomizedALPN}
    HelloRandomizedNoALPN = ClientHelloID{helloRandomized, helloRandomizedNoALPN}

    // The rest will will parrot given browser.
    HelloFirefox_Auto = HelloFirefox_63
    HelloFirefox_55   = ClientHelloID{helloFirefox, 55}
    HelloFirefox_56   = ClientHelloID{helloFirefox, 56}
    HelloFirefox_63   = ClientHelloID{helloFirefox, 63}

    HelloChrome_Auto = HelloChrome_70
    HelloChrome_58   = ClientHelloID{helloChrome, 58}
    HelloChrome_62   = ClientHelloID{helloChrome, 62}
    HelloChrome_70   = ClientHelloID{helloChrome, 70}

    HelloIOS_Auto = HelloIOS_11_1
    HelloIOS_11_1 = ClientHelloID{helloIOS, 111}

func BoringPaddingStyle Uses

func BoringPaddingStyle(unpaddedLen int) (int, bool)

func EnableWeakCiphers Uses

func EnableWeakCiphers()

EnableWeakCiphers allows utls connections to continue in some cases, when weak cipher was chosen. This provides better compatibility with servers on the web, but weakens security. Feel free to use this option if you establish additional secure connection inside of utls connection. This option does not change the shape of parrots (i.e. same ciphers will be offered either way). Must be called before establishing any connections.

func GetBoringGREASEValue Uses

func GetBoringGREASEValue(greaseSeed [ssl_grease_last_index]uint16, index int) uint16

will panic if ssl_grease_last_index[index] is out of bounds.

func Listen Uses

func Listen(network, laddr string, config *Config) (net.Listener, error)

Listen creates a TLS listener accepting connections on the given network address using net.Listen. The configuration config must be non-nil and must include at least one certificate or else set GetCertificate.

func NewListener Uses

func NewListener(inner net.Listener, config *Config) net.Listener

NewListener creates a Listener which accepts connections from an inner Listener and wraps each connection with Server. The configuration config must be non-nil and must include at least one certificate or else set GetCertificate.

type ALPNExtension Uses

type ALPNExtension struct {
    AlpnProtocols []string

func (*ALPNExtension) Len Uses

func (e *ALPNExtension) Len() int

func (*ALPNExtension) Read Uses

func (e *ALPNExtension) Read(b []byte) (int, error)

type Certificate Uses

type Certificate struct {
    Certificate [][]byte
    // PrivateKey contains the private key corresponding to the public key
    // in Leaf. For a server, this must implement crypto.Signer and/or
    // crypto.Decrypter, with an RSA or ECDSA PublicKey. For a client
    // (performing client authentication), this must be a crypto.Signer
    // with an RSA or ECDSA PublicKey.
    PrivateKey crypto.PrivateKey
    // 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 for TLS clients doing client authentication. If nil, the
    // leaf certificate will be parsed as needed.
    Leaf *x509.Certificate

A Certificate is a chain of one or more certificates, leaf first.

func LoadX509KeyPair Uses

func LoadX509KeyPair(certFile, keyFile string) (Certificate, error)

LoadX509KeyPair reads and parses a public/private key pair from a pair of files. The files must contain PEM encoded data. The certificate file may contain intermediate certificates following the leaf certificate to form a certificate chain. On successful return, Certificate.Leaf will be nil because the parsed form of the certificate is not retained.

func X509KeyPair Uses

func X509KeyPair(certPEMBlock, keyPEMBlock []byte) (Certificate, error)

X509KeyPair parses a public/private key pair from a pair of PEM encoded data. On successful return, Certificate.Leaf will be nil because the parsed form of the certificate is not retained.

type CertificateRequestInfo Uses

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

CertificateRequestInfo contains information from a server's CertificateRequest message, which is used to demand a certificate and proof of control from a client.

type CertificateRequestMsgTLS13 Uses

type CertificateRequestMsgTLS13 struct {
    Raw                              []byte
    OcspStapling                     bool
    Scts                             bool
    SupportedSignatureAlgorithms     []SignatureScheme
    SupportedSignatureAlgorithmsCert []SignatureScheme
    CertificateAuthorities           [][]byte

type CipherSuite Uses

type CipherSuite struct {
    Id  uint16
    // the lengths, in bytes, of the key material needed for each component.
    KeyLen int
    MacLen int
    IvLen  int
    Ka     func(version uint16) keyAgreement
    // flags is a bitmask of the suite* values, above.
    Flags  int
    Cipher func(key, iv []byte, isRead bool) interface{}
    Mac    func(version uint16, macKey []byte) macFunction
    Aead   func(key, fixedNonce []byte) aead

A CipherSuite is a specific combination of key agreement, cipher and MAC function. All cipher suites currently assume RSA key agreement.

type CipherSuiteTLS13 Uses

type CipherSuiteTLS13 struct {
    Id     uint16
    KeyLen int
    Aead   func(key, fixedNonce []byte) aead
    Hash   crypto.Hash

type ClientAuthType Uses

type ClientAuthType int

ClientAuthType declares the policy the server will follow for TLS Client Authentication.

const (
    NoClientCert ClientAuthType = iota

type ClientHandshakeState Uses

type ClientHandshakeState struct {
    C            *Conn
    ServerHello  *ServerHelloMsg
    Hello        *ClientHelloMsg
    MasterSecret []byte
    Session      *ClientSessionState

    State12 TLS12OnlyState
    State13 TLS13OnlyState

ClientHandshakeState includes both TLS 1.3-only and TLS 1.2-only states, only one of them will be used, depending on negotiated version.

ClientHandshakeState will be converted into and from either

- clientHandshakeState      (TLS 1.2)
- clientHandshakeStateTLS13 (TLS 1.3)

uTLS will call .handshake() on one of these private internal states, to perform TLS handshake using standard crypto/tls implementation.

type ClientHelloID Uses

type ClientHelloID struct {
    Browser string
    Version uint16

func (*ClientHelloID) Str Uses

func (p *ClientHelloID) Str() string

type ClientHelloInfo Uses

type ClientHelloInfo struct {
    // CipherSuites lists the CipherSuites supported by the client (e.g.
    // TLS_RSA_WITH_RC4_128_SHA).
    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
    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

ClientHelloInfo contains information from a ClientHello message in order to guide certificate selection in the GetCertificate callback.

type ClientHelloMsg Uses

type ClientHelloMsg struct {
    Raw                          []byte
    Vers                         uint16
    Random                       []byte
    SessionId                    []byte
    CipherSuites                 []uint16
    CompressionMethods           []uint8
    NextProtoNeg                 bool
    ServerName                   string
    OcspStapling                 bool
    Scts                         bool
    Ems                          bool // [UTLS] actually implemented due to its prevalence
    SupportedCurves              []CurveID
    SupportedPoints              []uint8
    TicketSupported              bool
    SessionTicket                []uint8
    SupportedSignatureAlgorithms []SignatureScheme
    SecureRenegotiation          []byte
    SecureRenegotiationSupported bool
    AlpnProtocols                []string

    // 1.3
    SupportedSignatureAlgorithmsCert []SignatureScheme
    SupportedVersions                []uint16
    Cookie                           []byte
    KeyShares                        []KeyShare
    EarlyData                        bool
    PskModes                         []uint8
    PskIdentities                    []pskIdentity
    PskBinders                       [][]byte

type ClientHelloSpec Uses

type ClientHelloSpec struct {
    CipherSuites       []uint16       // nil => default
    CompressionMethods []uint8        // nil => no compression
    Extensions         []TLSExtension // nil => no extensions

    TLSVersMin uint16 // [1.0-1.3]
    TLSVersMax uint16 // [1.2-1.3]

    // GreaseStyle: currently only random
    // sessionID may or may not depend on ticket; nil => random
    GetSessionID func(ticket []byte) [32]byte

type ClientSessionCache Uses

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)

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.

func NewLRUClientSessionCache Uses

func NewLRUClientSessionCache(capacity int) ClientSessionCache

NewLRUClientSessionCache returns a ClientSessionCache with the given capacity that uses an LRU strategy. If capacity is < 1, a default capacity is used instead.

type ClientSessionState Uses

type ClientSessionState struct {
    // contains filtered or unexported fields

ClientSessionState contains the state needed by clients to resume TLS sessions.

func MakeClientSessionState Uses

func MakeClientSessionState(
    SessionTicket []uint8,
    Vers uint16,
    CipherSuite uint16,
    MasterSecret []byte,
    ServerCertificates []*x509.Certificate,
    VerifiedChains [][]*x509.Certificate) *ClientSessionState

ClientSessionState contains the state needed by clients to resume TLS sessions.

func (*ClientSessionState) CipherSuite Uses

func (css *ClientSessionState) CipherSuite() uint16

Ciphersuite negotiated for the session

func (*ClientSessionState) MasterSecret Uses

func (css *ClientSessionState) MasterSecret() []byte

MasterSecret generated by client on a full handshake

func (*ClientSessionState) ServerCertificates Uses

func (css *ClientSessionState) ServerCertificates() []*x509.Certificate

Certificate chain presented by the server

func (*ClientSessionState) SessionTicket Uses

func (css *ClientSessionState) SessionTicket() []uint8

Encrypted ticket used for session resumption with server

func (*ClientSessionState) SetCipherSuite Uses

func (css *ClientSessionState) SetCipherSuite(CipherSuite uint16)

func (*ClientSessionState) SetMasterSecret Uses

func (css *ClientSessionState) SetMasterSecret(MasterSecret []byte)

func (*ClientSessionState) SetServerCertificates Uses

func (css *ClientSessionState) SetServerCertificates(ServerCertificates []*x509.Certificate)

func (*ClientSessionState) SetSessionTicket Uses

func (css *ClientSessionState) SetSessionTicket(SessionTicket []uint8)

func (*ClientSessionState) SetVerifiedChains Uses

func (css *ClientSessionState) SetVerifiedChains(VerifiedChains [][]*x509.Certificate)

func (*ClientSessionState) SetVers Uses

func (css *ClientSessionState) SetVers(Vers uint16)

func (*ClientSessionState) VerifiedChains Uses

func (css *ClientSessionState) VerifiedChains() [][]*x509.Certificate

Certificate chains we built for verification

func (*ClientSessionState) Vers Uses

func (css *ClientSessionState) Vers() uint16

SSL/TLS version negotiated for the session

type Config Uses

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. Server configurations must include
    // at least one certificate or else set GetCertificate. Clients doing
    // client-authentication may set either Certificates or
    // GetClientCertificate.
    Certificates []Certificate

    // NameToCertificate maps from a certificate name to an element of
    // Certificates. Note that a certificate name can be of the form
    // '*' and so doesn't have to be a domain name as such.
    // See Config.BuildNameToCertificate
    // The nil value causes the first element of Certificates to be used
    // for all connections.
    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
    // first 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.
    // Uniquely for the fields in the returned Config, session ticket keys
    // will be duplicated from the original Config if not set.
    // Specifically, if SetSessionTicketKeys was called on the original
    // config but not on the returned config then the ticket keys from the
    // original config will be copied into the new config before use.
    // Otherwise, if SessionTicketKey was set in the original config but
    // not in the returned config then it will be copied into the returned
    // config before use. If neither of those cases applies then the key
    // material from the returned config will be used for session tickets.
    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

    // 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.
    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, TLS accepts any certificate
    // presented by the server and any host name in that certificate.
    // In this mode, TLS is susceptible to man-in-the-middle attacks.
    // This should be used only for testing.
    InsecureSkipVerify bool

    // CipherSuites is a list of supported cipher suites. If CipherSuites
    // is nil, TLS uses a list of suites supported by the implementation.
    CipherSuites []uint16

    // PreferServerCipherSuites controls whether the server selects the
    // client's most preferred ciphersuite, or the server's most preferred
    // ciphersuite. If true then the server's preference, as expressed in
    // the order of elements in CipherSuites, is used.
    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.
    // If multiple servers are terminating connections for the same host
    // they should all have the same SessionTicketKey. If the
    // SessionTicketKey leaks, previously recorded and future TLS
    // connections using that key might be compromised.
    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 SSL/TLS version that is acceptable.
    // If zero, then TLS 1.0 is taken as the minimum.
    MinVersion uint16

    // MaxVersion contains the maximum SSL/TLS version that is acceptable.
    // If zero, then 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
    // Use of KeyLogWriter compromises security and should only be
    // used for debugging.
    KeyLogWriter io.Writer
    // contains filtered or unexported fields

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.

func (*Config) BuildNameToCertificate Uses

func (c *Config) BuildNameToCertificate()

BuildNameToCertificate parses c.Certificates and builds c.NameToCertificate from the CommonName and SubjectAlternateName fields of each of the leaf certificates.

func (*Config) Clone Uses

func (c *Config) Clone() *Config

Clone returns a shallow clone of c. It is safe to clone a Config that is being used concurrently by a TLS client or server.

func (*Config) SetSessionTicketKeys Uses

func (c *Config) SetSessionTicketKeys(keys [][32]byte)

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.

type Conn Uses

type Conn struct {
    // contains filtered or unexported fields

A Conn represents a secured connection. It implements the net.Conn interface.

func Client Uses

func Client(conn net.Conn, config *Config) *Conn

Client returns a new TLS client side connection using conn as the underlying transport. The config cannot be nil: users must set either ServerName or InsecureSkipVerify in the config.

func Dial Uses

func Dial(network, addr string, config *Config) (*Conn, error)

Dial connects to the given network address using net.Dial and then initiates a TLS handshake, returning the resulting TLS connection. Dial interprets a nil configuration as equivalent to the zero configuration; see the documentation of Config for the defaults.

func DialWithDialer Uses

func DialWithDialer(dialer *net.Dialer, network, addr string, config *Config) (*Conn, error)

DialWithDialer connects to the given network address using dialer.Dial and then initiates a TLS handshake, returning the resulting TLS connection. Any timeout or deadline given in the dialer apply to connection and TLS handshake as a whole.

DialWithDialer interprets a nil configuration as equivalent to the zero configuration; see the documentation of Config for the defaults.

func MakeConnWithCompleteHandshake Uses

func MakeConnWithCompleteHandshake(tcpConn net.Conn, version uint16, cipherSuite uint16, masterSecret []byte, clientRandom []byte, serverRandom []byte, isClient bool) *Conn

MakeConnWithCompleteHandshake allows to forge both server and client side TLS connections. Major Hack Alert.

func Server Uses

func Server(conn net.Conn, config *Config) *Conn

Server returns a new TLS server side connection using conn as the underlying transport. The configuration config must be non-nil and must include at least one certificate or else set GetCertificate.

func (*Conn) Close Uses

func (c *Conn) Close() error

Close closes the connection.

func (*Conn) CloseWrite Uses

func (c *Conn) CloseWrite() error

CloseWrite shuts down the writing side of the connection. It should only be called once the handshake has completed and does not call CloseWrite on the underlying connection. Most callers should just use Close.

func (*Conn) ConnectionState Uses

func (c *Conn) ConnectionState() ConnectionState

ConnectionState returns basic TLS details about the connection.

func (*Conn) Handshake Uses

func (c *Conn) Handshake() error

Handshake runs the client or server handshake protocol if it has not yet been run. Most uses of this package need not call Handshake explicitly: the first Read or Write will call it automatically.

func (*Conn) LocalAddr Uses

func (c *Conn) LocalAddr() net.Addr

LocalAddr returns the local network address.

func (*Conn) OCSPResponse Uses

func (c *Conn) OCSPResponse() []byte

OCSPResponse returns the stapled OCSP response from the TLS server, if any. (Only valid for client connections.)

func (*Conn) Read Uses

func (c *Conn) Read(b []byte) (int, error)

Read can be made to time out and return a net.Error with Timeout() == true after a fixed time limit; see SetDeadline and SetReadDeadline.

func (*Conn) RemoteAddr Uses

func (c *Conn) RemoteAddr() net.Addr

RemoteAddr returns the remote network address.

func (*Conn) SetDeadline Uses

func (c *Conn) SetDeadline(t time.Time) error

SetDeadline sets the read and write deadlines associated with the connection. A zero value for t means Read and Write will not time out. After a Write has timed out, the TLS state is corrupt and all future writes will return the same error.

func (*Conn) SetReadDeadline Uses

func (c *Conn) SetReadDeadline(t time.Time) error

SetReadDeadline sets the read deadline on the underlying connection. A zero value for t means Read will not time out.

func (*Conn) SetWriteDeadline Uses

func (c *Conn) SetWriteDeadline(t time.Time) error

SetWriteDeadline sets the write deadline on the underlying connection. A zero value for t means Write will not time out. After a Write has timed out, the TLS state is corrupt and all future writes will return the same error.

func (*Conn) VerifyHostname Uses

func (c *Conn) VerifyHostname(host string) error

VerifyHostname checks that the peer certificate chain is valid for connecting to host. If so, it returns nil; if not, it returns an error describing the problem.

func (*Conn) Write Uses

func (c *Conn) Write(b []byte) (int, error)

Write writes data to the connection.

type ConnectionState Uses

type ConnectionState struct {
    Version                     uint16                // TLS version used by the connection (e.g. VersionTLS12)
    HandshakeComplete           bool                  // TLS handshake is complete
    DidResume                   bool                  // connection resumes a previous TLS connection
    CipherSuite                 uint16                // cipher suite in use (TLS_RSA_WITH_RC4_128_SHA, ...)
    NegotiatedProtocol          string                // negotiated next protocol (not guaranteed to be from Config.NextProtos)
    NegotiatedProtocolIsMutual  bool                  // negotiated protocol was advertised by server (client side only)
    ServerName                  string                // server name requested by client, if any (server side only)
    PeerCertificates            []*x509.Certificate   // certificate chain presented by remote peer
    VerifiedChains              [][]*x509.Certificate // verified chains built from PeerCertificates
    SignedCertificateTimestamps [][]byte              // SCTs from the peer, if any
    OCSPResponse                []byte                // stapled OCSP response from peer, if any

    // TLSUnique contains the "tls-unique" channel binding value (see RFC
    // 5929, section 3). For resumed sessions this value will be nil
    // because resumption does not include enough context (see
    // This will
    // change in future versions of Go once the TLS master-secret fix has
    // been standardized and implemented. It is not defined in TLS 1.3.
    TLSUnique []byte
    // contains filtered or unexported fields

ConnectionState records basic TLS details about the connection.

func (*ConnectionState) ExportKeyingMaterial Uses

func (cs *ConnectionState) ExportKeyingMaterial(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.

type CurveID Uses

type CurveID uint16

CurveID is the type of a TLS identifier for an elliptic curve. See

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.

const (
    CurveP256 CurveID = 23
    CurveP384 CurveID = 24
    CurveP521 CurveID = 25
    X25519    CurveID = 29

type EcdheParameters Uses

type EcdheParameters interface {
    // contains filtered or unexported methods

type FakeChannelIDExtension Uses

type FakeChannelIDExtension struct {

func (*FakeChannelIDExtension) Len Uses

func (e *FakeChannelIDExtension) Len() int

func (*FakeChannelIDExtension) Read Uses

func (e *FakeChannelIDExtension) Read(b []byte) (int, error)

type FinishedHash Uses

type FinishedHash struct {
    Client hash.Hash
    Server hash.Hash

    // Prior to TLS 1.2, an additional MD5 hash is required.
    ClientMD5 hash.Hash
    ServerMD5 hash.Hash

    // In TLS 1.2, a full buffer is sadly required.
    Buffer []byte

    Version uint16
    Prf     func(result, secret, label, seed []byte)

A FinishedHash calculates the hash of a set of handshake messages suitable for including in a Finished message.

type GenericExtension Uses

type GenericExtension struct {
    // contains filtered or unexported fields

func (*GenericExtension) Len Uses

func (e *GenericExtension) Len() int

func (*GenericExtension) Read Uses

func (e *GenericExtension) Read(b []byte) (int, error)

type KeyShare Uses

type KeyShare struct {
    Group CurveID
    Data  []byte

TLS 1.3 Key Share. See RFC 8446, Section 4.2.8.

type KeyShareExtension Uses

type KeyShareExtension struct {
    KeyShares []KeyShare

TLS 1.3

func (*KeyShareExtension) Len Uses

func (e *KeyShareExtension) Len() int

func (*KeyShareExtension) Read Uses

func (e *KeyShareExtension) Read(b []byte) (int, error)

type KeyShares Uses

type KeyShares []KeyShare

func (KeyShares) ToPrivate Uses

func (KSS KeyShares) ToPrivate() []keyShare

type NPNExtension Uses

type NPNExtension struct {
    NextProtos []string

func (*NPNExtension) Len Uses

func (e *NPNExtension) Len() int

func (*NPNExtension) Read Uses

func (e *NPNExtension) Read(b []byte) (int, error)

type PSKKeyExchangeModesExtension Uses

type PSKKeyExchangeModesExtension struct {
    Modes []uint8

func (*PSKKeyExchangeModesExtension) Len Uses

func (e *PSKKeyExchangeModesExtension) Len() int

func (*PSKKeyExchangeModesExtension) Read Uses

func (e *PSKKeyExchangeModesExtension) Read(b []byte) (int, error)

type RecordHeaderError Uses

type RecordHeaderError struct {
    // Msg contains a human readable string that describes the error.
    Msg string
    // RecordHeader contains the five bytes of TLS record header that
    // triggered the error.
    RecordHeader [5]byte
    // Conn provides the underlying net.Conn in the case that a client
    // sent an initial handshake that didn't look like TLS.
    // It is nil if there's already been a handshake or a TLS alert has
    // been written to the connection.
    Conn net.Conn

RecordHeaderError is returned when a TLS record header is invalid.

func (RecordHeaderError) Error Uses

func (e RecordHeaderError) Error() string

type RenegotiationInfoExtension Uses

type RenegotiationInfoExtension struct {
    SecureRenegotiation []byte // if empty, default []byte{0} is assumed
    // contains filtered or unexported fields

func (*RenegotiationInfoExtension) Len Uses

func (e *RenegotiationInfoExtension) Len() int

func (*RenegotiationInfoExtension) Read Uses

func (e *RenegotiationInfoExtension) Read(b []byte) (int, error)

type RenegotiationSupport Uses

type RenegotiationSupport int

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.

const (
    // RenegotiateNever disables renegotiation.
    RenegotiateNever RenegotiationSupport = iota

    // RenegotiateOnceAsClient allows a remote server to request
    // renegotiation once per connection.

    // RenegotiateFreelyAsClient allows a remote server to repeatedly
    // request renegotiation.

type Roller Uses

type Roller struct {
    HelloIDs            []ClientHelloID
    HelloIDMu           sync.Mutex
    WorkingHelloID      *ClientHelloID
    TcpDialTimeout      time.Duration
    TlsHandshakeTimeout time.Duration

func NewRoller Uses

func NewRoller() (*Roller, error)

NewRoller creates Roller object with default range of HelloIDs to cycle through until a working/unblocked one is found.

func (*Roller) Dial Uses

func (c *Roller) Dial(network, addr, serverName string) (*UConn, error)

Dial attempts to establish connection to given address using different HelloIDs. If a working HelloID is found, it is used again for subsequent Dials. If tcp connection fails or all HelloIDs are tried, returns with last error.

Usage examples:

Dial("tcp4", "", "")
Dial("tcp", "", "")

type SCTExtension Uses

type SCTExtension struct {

func (*SCTExtension) Len Uses

func (e *SCTExtension) Len() int

func (*SCTExtension) Read Uses

func (e *SCTExtension) Read(b []byte) (int, error)

type SNIExtension Uses

type SNIExtension struct {
    ServerName string // not an array because go crypto/tls doesn't support multiple SNIs

func (*SNIExtension) Len Uses

func (e *SNIExtension) Len() int

func (*SNIExtension) Read Uses

func (e *SNIExtension) Read(b []byte) (int, error)

type ServerHelloMsg Uses

type ServerHelloMsg struct {
    Raw                          []byte
    Vers                         uint16
    Random                       []byte
    SessionId                    []byte
    CipherSuite                  uint16
    CompressionMethod            uint8
    NextProtoNeg                 bool
    NextProtos                   []string
    OcspStapling                 bool
    Scts                         [][]byte
    Ems                          bool
    TicketSupported              bool
    SecureRenegotiation          []byte
    SecureRenegotiationSupported bool
    AlpnProtocol                 string

    // 1.3
    SupportedVersion        uint16
    ServerShare             keyShare
    SelectedIdentityPresent bool
    SelectedIdentity        uint16
    Cookie                  []byte  // HelloRetryRequest extension
    SelectedGroup           CurveID // HelloRetryRequest extension


type SessionTicketExtension Uses

type SessionTicketExtension struct {
    Session *ClientSessionState

func (*SessionTicketExtension) Len Uses

func (e *SessionTicketExtension) Len() int

func (*SessionTicketExtension) Read Uses

func (e *SessionTicketExtension) Read(b []byte) (int, error)

type SignatureAlgorithmsExtension Uses

type SignatureAlgorithmsExtension struct {
    SupportedSignatureAlgorithms []SignatureScheme

func (*SignatureAlgorithmsExtension) Len Uses

func (e *SignatureAlgorithmsExtension) Len() int

func (*SignatureAlgorithmsExtension) Read Uses

func (e *SignatureAlgorithmsExtension) Read(b []byte) (int, error)

type SignatureScheme Uses

type SignatureScheme uint16

SignatureScheme identifies a signature algorithm supported by TLS. See RFC 8446, Section 4.2.3.

const (
    PKCS1WithSHA1   SignatureScheme = 0x0201
    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

    ECDSAWithP256AndSHA256 SignatureScheme = 0x0403
    ECDSAWithP384AndSHA384 SignatureScheme = 0x0503
    ECDSAWithP521AndSHA512 SignatureScheme = 0x0603

    // Legacy signature and hash algorithms for TLS 1.2.
    ECDSAWithSHA1 SignatureScheme = 0x0203
var (
    FakePKCS1WithSHA224 SignatureScheme = 0x0301
    FakeECDSAWithSHA224 SignatureScheme = 0x0303

newest signatures

type StatusRequestExtension Uses

type StatusRequestExtension struct {

func (*StatusRequestExtension) Len Uses

func (e *StatusRequestExtension) Len() int

func (*StatusRequestExtension) Read Uses

func (e *StatusRequestExtension) Read(b []byte) (int, error)

type SupportedCurvesExtension Uses

type SupportedCurvesExtension struct {
    Curves []CurveID

func (*SupportedCurvesExtension) Len Uses

func (e *SupportedCurvesExtension) Len() int

func (*SupportedCurvesExtension) Read Uses

func (e *SupportedCurvesExtension) Read(b []byte) (int, error)

type SupportedPointsExtension Uses

type SupportedPointsExtension struct {
    SupportedPoints []uint8

func (*SupportedPointsExtension) Len Uses

func (e *SupportedPointsExtension) Len() int

func (*SupportedPointsExtension) Read Uses

func (e *SupportedPointsExtension) Read(b []byte) (int, error)

type SupportedVersionsExtension Uses

type SupportedVersionsExtension struct {
    Versions []uint16

func (*SupportedVersionsExtension) Len Uses

func (e *SupportedVersionsExtension) Len() int

func (*SupportedVersionsExtension) Read Uses

func (e *SupportedVersionsExtension) Read(b []byte) (int, error)

type TLS12OnlyState Uses

type TLS12OnlyState struct {
    FinishedHash FinishedHash
    Suite        CipherSuite

TLS 1.2 and before only

type TLS13OnlyState Uses

type TLS13OnlyState struct {
    Suite         *CipherSuiteTLS13
    EcdheParams   EcdheParameters
    EarlySecret   []byte
    BinderKey     []byte
    CertReq       *CertificateRequestMsgTLS13
    UsingPSK      bool
    SentDummyCCS  bool
    Transcript    hash.Hash
    TrafficSecret []byte // client_application_traffic_secret_0

TLS 1.3 only

type TLSExtension Uses

type TLSExtension interface {
    Len() int // includes header

    // Read reads up to len(p) bytes into p.
    // It returns the number of bytes read (0 <= n <= len(p)) and any error encountered.
    Read(p []byte) (n int, err error) // implements io.Reader
    // contains filtered or unexported methods

type UConn Uses

type UConn struct {

    Extensions []TLSExtension

    ClientHelloBuilt bool
    HandshakeState   ClientHandshakeState

    // sessionID may or may not depend on ticket; nil => random
    GetSessionID func(ticket []byte) [32]byte
    // contains filtered or unexported fields

func UClient Uses

func UClient(conn net.Conn, config *Config, clientHelloID ClientHelloID) *UConn

UClient returns a new uTLS client, with behavior depending on clientHelloID. Config CAN be nil, but make sure to eventually specify ServerName.

func (*UConn) ApplyConfig Uses

func (uconn *UConn) ApplyConfig() error

func (*UConn) ApplyPreset Uses

func (uconn *UConn) ApplyPreset(p *ClientHelloSpec) error

ApplyPreset should only be used in conjunction with HelloCustom to apply custom specs. Fields of TLSExtensions that are slices/pointers are shared across different connections with same ClientHelloSpec. It is advised to use different specs and avoid any shared state.

func (*UConn) BuildHandshakeState Uses

func (uconn *UConn) BuildHandshakeState() error

BuildHandshakeState behavior varies based on ClientHelloID and whether it was already called before. If HelloGolang:

[only once] make default ClientHello and overwrite existing state

If any other mimicking ClientHelloID is used:

[only once] make ClientHello based on ID and overwrite existing state
[each call] apply uconn.Extensions config to internal crypto/tls structures
[each call] marshal ClientHello.

BuildHandshakeState is automatically called before uTLS performs handshake, amd should only be called explicitly to inspect/change fields of default/mimicked ClientHello.

func (*UConn) GetOutKeystream Uses

func (uconn *UConn) GetOutKeystream(length int) ([]byte, error)

get current state of cipher and encrypt zeros to get keystream

func (*UConn) GetUnderlyingConn Uses

func (uconn *UConn) GetUnderlyingConn() net.Conn

func (*UConn) Handshake Uses

func (c *UConn) Handshake() error

Handshake runs the client handshake using given clientHandshakeState Requires hs.hello, and, optionally, hs.session to be set.

func (*UConn) MarshalClientHello Uses

func (uconn *UConn) MarshalClientHello() error

func (*UConn) SetClientRandom Uses

func (uconn *UConn) SetClientRandom(r []byte) error

SetClientRandom sets client random explicitly. BuildHandshakeFirst() must be called before SetClientRandom. r must to be 32 bytes long.

func (*UConn) SetSNI Uses

func (uconn *UConn) SetSNI(sni string)

func (*UConn) SetSessionCache Uses

func (uconn *UConn) SetSessionCache(cache ClientSessionCache)

If you want session tickets to be reused - use same cache on following connections

func (*UConn) SetSessionState Uses

func (uconn *UConn) SetSessionState(session *ClientSessionState) error

SetSessionState sets the session ticket, which may be preshared or fake. If session is nil, the body of session ticket extension will be unset, but the extension itself still MAY be present for mimicking purposes. Session tickets to be reused - use same cache on following connections.

func (*UConn) SetTLSVers Uses

func (uconn *UConn) SetTLSVers(minTLSVers, maxTLSVers uint16) error

SetVersCreateState set min and max TLS version in all appropriate places.

func (*UConn) SetUnderlyingConn Uses

func (uconn *UConn) SetUnderlyingConn(c net.Conn)

func (*UConn) Write Uses

func (c *UConn) Write(b []byte) (int, error)

Copy-pasted from tls.Conn in its entirety. But c.Handshake() is now utls' one, not tls. Write writes data to the connection.

type UtlsExtendedMasterSecretExtension Uses

type UtlsExtendedMasterSecretExtension struct {

func (*UtlsExtendedMasterSecretExtension) Len Uses

func (e *UtlsExtendedMasterSecretExtension) Len() int

func (*UtlsExtendedMasterSecretExtension) Read Uses

func (e *UtlsExtendedMasterSecretExtension) Read(b []byte) (int, error)

type UtlsGREASEExtension Uses

type UtlsGREASEExtension struct {
    Value uint16
    Body  []byte // in Chrome first grease has empty body, second grease has a single zero byte

it is responsibility of user not to generate multiple grease extensions with same value

func (*UtlsGREASEExtension) Len Uses

func (e *UtlsGREASEExtension) Len() int

func (*UtlsGREASEExtension) Read Uses

func (e *UtlsGREASEExtension) Read(b []byte) (int, error)

type UtlsPaddingExtension Uses

type UtlsPaddingExtension struct {
    PaddingLen int
    WillPad    bool // set to false to disable extension

    // Functor for deciding on padding length based on unpadded ClientHello length.
    // If willPad is false, then this extension should not be included.
    GetPaddingLen func(clientHelloUnpaddedLen int) (paddingLen int, willPad bool)

func (*UtlsPaddingExtension) Len Uses

func (e *UtlsPaddingExtension) Len() int

func (*UtlsPaddingExtension) Read Uses

func (e *UtlsPaddingExtension) Read(b []byte) (int, error)

func (*UtlsPaddingExtension) Update Uses

func (e *UtlsPaddingExtension) Update(clientHelloUnpaddedLen int)


The crypto/tls package only implements some countermeasures against Lucky13 attacks on CBC-mode encryption, and only on SHA1 variants. See and


cpuPackage cpu implements processor feature detection used by the Go standard library.

Package tls imports 40 packages (graph) and is imported by 2 packages. Updated 2019-03-27. Refresh now. Tools for package owners.