tls.go

     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 partially implements TLS 1.2, as specified in RFC 5246,
     6  // and TLS 1.3, as specified in RFC 8446.
     7  package tls
     8  
     9  // BUG(agl): The crypto/tls package only implements some countermeasures
    10  // against Lucky13 attacks on CBC-mode encryption, and only on SHA1
    11  // variants. See http://www.isg.rhul.ac.uk/tls/TLStiming.pdf and
    12  // https://www.imperialviolet.org/2013/02/04/luckythirteen.html.
    13  
    14  import (
    15  	"bytes"
    16  	"context"
    17  	"crypto"
    18  	"crypto/ecdsa"
    19  	"crypto/ed25519"
    20  	"crypto/rsa"
    21  	"crypto/x509"
    22  	"encoding/pem"
    23  	"errors"
    24  	"fmt"
    25  	"internal/godebug"
    26  	"net"
    27  	"os"
    28  	"strings"
    29  )
    30  
    31  // Server returns a new TLS server side connection
    32  // using conn as the underlying transport.
    33  // The configuration config must be non-nil and must include
    34  // at least one certificate or else set GetCertificate.
    35  func Server(conn net.Conn, config *Config) *Conn {
    36  	c := &Conn{
    37  		conn:   conn,
    38  		config: config,
    39  	}
    40  	c.handshakeFn = c.serverHandshake
    41  	return c
    42  }
    43  
    44  // Client returns a new TLS client side connection
    45  // using conn as the underlying transport.
    46  // The config cannot be nil: users must set either ServerName or
    47  // InsecureSkipVerify in the config.
    48  func Client(conn net.Conn, config *Config) *Conn {
    49  	c := &Conn{
    50  		conn:     conn,
    51  		config:   config,
    52  		isClient: true,
    53  	}
    54  	c.handshakeFn = c.clientHandshake
    55  	return c
    56  }
    57  
    58  // A listener implements a network listener (net.Listener) for TLS connections.
    59  type listener struct {
    60  	net.Listener
    61  	config *Config
    62  }
    63  
    64  // Accept waits for and returns the next incoming TLS connection.
    65  // The returned connection is of type *Conn.
    66  func (l *listener) Accept() (net.Conn, error) {
    67  	c, err := l.Listener.Accept()
    68  	if err != nil {
    69  		return nil, err
    70  	}
    71  	return Server(c, l.config), nil
    72  }
    73  
    74  // NewListener creates a Listener which accepts connections from an inner
    75  // Listener and wraps each connection with [Server].
    76  // The configuration config must be non-nil and must include
    77  // at least one certificate or else set GetCertificate.
    78  func NewListener(inner net.Listener, config *Config) net.Listener {
    79  	l := new(listener)
    80  	l.Listener = inner
    81  	l.config = config
    82  	return l
    83  }
    84  
    85  // Listen creates a TLS listener accepting connections on the
    86  // given network address using net.Listen.
    87  // The configuration config must be non-nil and must include
    88  // at least one certificate or else set GetCertificate.
    89  func Listen(network, laddr string, config *Config) (net.Listener, error) {
    90  	// If this condition changes, consider updating http.Server.ServeTLS too.
    91  	if config == nil || len(config.Certificates) == 0 &&
    92  		config.GetCertificate == nil && config.GetConfigForClient == nil {
    93  		return nil, errors.New("tls: neither Certificates, GetCertificate, nor GetConfigForClient set in Config")
    94  	}
    95  	l, err := net.Listen(network, laddr)
    96  	if err != nil {
    97  		return nil, err
    98  	}
    99  	return NewListener(l, config), nil
   100  }
   101  
   102  type timeoutError struct{}
   103  
   104  func (timeoutError) Error() string   { return "tls: DialWithDialer timed out" }
   105  func (timeoutError) Timeout() bool   { return true }
   106  func (timeoutError) Temporary() bool { return true }
   107  
   108  // DialWithDialer connects to the given network address using dialer.Dial and
   109  // then initiates a TLS handshake, returning the resulting TLS connection. Any
   110  // timeout or deadline given in the dialer apply to connection and TLS
   111  // handshake as a whole.
   112  //
   113  // DialWithDialer interprets a nil configuration as equivalent to the zero
   114  // configuration; see the documentation of [Config] for the defaults.
   115  //
   116  // DialWithDialer uses context.Background internally; to specify the context,
   117  // use [Dialer.DialContext] with NetDialer set to the desired dialer.
   118  func DialWithDialer(dialer *net.Dialer, network, addr string, config *Config) (*Conn, error) {
   119  	return dial(context.Background(), dialer, network, addr, config)
   120  }
   121  
   122  func dial(ctx context.Context, netDialer *net.Dialer, network, addr string, config *Config) (*Conn, error) {
   123  	if netDialer.Timeout != 0 {
   124  		var cancel context.CancelFunc
   125  		ctx, cancel = context.WithTimeout(ctx, netDialer.Timeout)
   126  		defer cancel()
   127  	}
   128  
   129  	if !netDialer.Deadline.IsZero() {
   130  		var cancel context.CancelFunc
   131  		ctx, cancel = context.WithDeadline(ctx, netDialer.Deadline)
   132  		defer cancel()
   133  	}
   134  
   135  	rawConn, err := netDialer.DialContext(ctx, network, addr)
   136  	if err != nil {
   137  		return nil, err
   138  	}
   139  
   140  	colonPos := strings.LastIndex(addr, ":")
   141  	if colonPos == -1 {
   142  		colonPos = len(addr)
   143  	}
   144  	hostname := addr[:colonPos]
   145  
   146  	if config == nil {
   147  		config = defaultConfig()
   148  	}
   149  	// If no ServerName is set, infer the ServerName
   150  	// from the hostname we're connecting to.
   151  	if config.ServerName == "" {
   152  		// Make a copy to avoid polluting argument or default.
   153  		c := config.Clone()
   154  		c.ServerName = hostname
   155  		config = c
   156  	}
   157  
   158  	conn := Client(rawConn, config)
   159  	if err := conn.HandshakeContext(ctx); err != nil {
   160  		rawConn.Close()
   161  		return nil, err
   162  	}
   163  	return conn, nil
   164  }
   165  
   166  // Dial connects to the given network address using net.Dial
   167  // and then initiates a TLS handshake, returning the resulting
   168  // TLS connection.
   169  // Dial interprets a nil configuration as equivalent to
   170  // the zero configuration; see the documentation of Config
   171  // for the defaults.
   172  func Dial(network, addr string, config *Config) (*Conn, error) {
   173  	return DialWithDialer(new(net.Dialer), network, addr, config)
   174  }
   175  
   176  // Dialer dials TLS connections given a configuration and a Dialer for the
   177  // underlying connection.
   178  type Dialer struct {
   179  	// NetDialer is the optional dialer to use for the TLS connections'
   180  	// underlying TCP connections.
   181  	// A nil NetDialer is equivalent to the net.Dialer zero value.
   182  	NetDialer *net.Dialer
   183  
   184  	// Config is the TLS configuration to use for new connections.
   185  	// A nil configuration is equivalent to the zero
   186  	// configuration; see the documentation of Config for the
   187  	// defaults.
   188  	Config *Config
   189  }
   190  
   191  // Dial connects to the given network address and initiates a TLS
   192  // handshake, returning the resulting TLS connection.
   193  //
   194  // The returned [Conn], if any, will always be of type *[Conn].
   195  //
   196  // Dial uses context.Background internally; to specify the context,
   197  // use [Dialer.DialContext].
   198  func (d *Dialer) Dial(network, addr string) (net.Conn, error) {
   199  	return d.DialContext(context.Background(), network, addr)
   200  }
   201  
   202  func (d *Dialer) netDialer() *net.Dialer {
   203  	if d.NetDialer != nil {
   204  		return d.NetDialer
   205  	}
   206  	return new(net.Dialer)
   207  }
   208  
   209  // DialContext connects to the given network address and initiates a TLS
   210  // handshake, returning the resulting TLS connection.
   211  //
   212  // The provided Context must be non-nil. If the context expires before
   213  // the connection is complete, an error is returned. Once successfully
   214  // connected, any expiration of the context will not affect the
   215  // connection.
   216  //
   217  // The returned [Conn], if any, will always be of type *[Conn].
   218  func (d *Dialer) DialContext(ctx context.Context, network, addr string) (net.Conn, error) {
   219  	c, err := dial(ctx, d.netDialer(), network, addr, d.Config)
   220  	if err != nil {
   221  		// Don't return c (a typed nil) in an interface.
   222  		return nil, err
   223  	}
   224  	return c, nil
   225  }
   226  
   227  // LoadX509KeyPair reads and parses a public/private key pair from a pair of
   228  // files. The files must contain PEM encoded data. The certificate file may
   229  // contain intermediate certificates following the leaf certificate to form a
   230  // certificate chain. On successful return, Certificate.Leaf will be populated.
   231  //
   232  // Before Go 1.23 Certificate.Leaf was left nil, and the parsed certificate was
   233  // discarded. This behavior can be re-enabled by setting "x509keypairleaf=0"
   234  // in the GODEBUG environment variable.
   235  func LoadX509KeyPair(certFile, keyFile string) (Certificate, error) {
   236  	certPEMBlock, err := os.ReadFile(certFile)
   237  	if err != nil {
   238  		return Certificate{}, err
   239  	}
   240  	keyPEMBlock, err := os.ReadFile(keyFile)
   241  	if err != nil {
   242  		return Certificate{}, err
   243  	}
   244  	return X509KeyPair(certPEMBlock, keyPEMBlock)
   245  }
   246  
   247  var x509keypairleaf = godebug.New("x509keypairleaf")
   248  
   249  // X509KeyPair parses a public/private key pair from a pair of
   250  // PEM encoded data. On successful return, Certificate.Leaf will be populated.
   251  //
   252  // Before Go 1.23 Certificate.Leaf was left nil, and the parsed certificate was
   253  // discarded. This behavior can be re-enabled by setting "x509keypairleaf=0"
   254  // in the GODEBUG environment variable.
   255  func X509KeyPair(certPEMBlock, keyPEMBlock []byte) (Certificate, error) {
   256  	fail := func(err error) (Certificate, error) { return Certificate{}, err }
   257  
   258  	var cert Certificate
   259  	var skippedBlockTypes []string
   260  	for {
   261  		var certDERBlock *pem.Block
   262  		certDERBlock, certPEMBlock = pem.Decode(certPEMBlock)
   263  		if certDERBlock == nil {
   264  			break
   265  		}
   266  		if certDERBlock.Type == "CERTIFICATE" {
   267  			cert.Certificate = append(cert.Certificate, certDERBlock.Bytes)
   268  		} else {
   269  			skippedBlockTypes = append(skippedBlockTypes, certDERBlock.Type)
   270  		}
   271  	}
   272  
   273  	if len(cert.Certificate) == 0 {
   274  		if len(skippedBlockTypes) == 0 {
   275  			return fail(errors.New("tls: failed to find any PEM data in certificate input"))
   276  		}
   277  		if len(skippedBlockTypes) == 1 && strings.HasSuffix(skippedBlockTypes[0], "PRIVATE KEY") {
   278  			return fail(errors.New("tls: failed to find certificate PEM data in certificate input, but did find a private key; PEM inputs may have been switched"))
   279  		}
   280  		return fail(fmt.Errorf("tls: failed to find \"CERTIFICATE\" PEM block in certificate input after skipping PEM blocks of the following types: %v", skippedBlockTypes))
   281  	}
   282  
   283  	skippedBlockTypes = skippedBlockTypes[:0]
   284  	var keyDERBlock *pem.Block
   285  	for {
   286  		keyDERBlock, keyPEMBlock = pem.Decode(keyPEMBlock)
   287  		if keyDERBlock == nil {
   288  			if len(skippedBlockTypes) == 0 {
   289  				return fail(errors.New("tls: failed to find any PEM data in key input"))
   290  			}
   291  			if len(skippedBlockTypes) == 1 && skippedBlockTypes[0] == "CERTIFICATE" {
   292  				return fail(errors.New("tls: found a certificate rather than a key in the PEM for the private key"))
   293  			}
   294  			return fail(fmt.Errorf("tls: failed to find PEM block with type ending in \"PRIVATE KEY\" in key input after skipping PEM blocks of the following types: %v", skippedBlockTypes))
   295  		}
   296  		if keyDERBlock.Type == "PRIVATE KEY" || strings.HasSuffix(keyDERBlock.Type, " PRIVATE KEY") {
   297  			break
   298  		}
   299  		skippedBlockTypes = append(skippedBlockTypes, keyDERBlock.Type)
   300  	}
   301  
   302  	// We don't need to parse the public key for TLS, but we so do anyway
   303  	// to check that it looks sane and matches the private key.
   304  	x509Cert, err := x509.ParseCertificate(cert.Certificate[0])
   305  	if err != nil {
   306  		return fail(err)
   307  	}
   308  
   309  	if x509keypairleaf.Value() != "0" {
   310  		cert.Leaf = x509Cert
   311  	} else {
   312  		x509keypairleaf.IncNonDefault()
   313  	}
   314  
   315  	cert.PrivateKey, err = parsePrivateKey(keyDERBlock.Bytes)
   316  	if err != nil {
   317  		return fail(err)
   318  	}
   319  
   320  	switch pub := x509Cert.PublicKey.(type) {
   321  	case *rsa.PublicKey:
   322  		priv, ok := cert.PrivateKey.(*rsa.PrivateKey)
   323  		if !ok {
   324  			return fail(errors.New("tls: private key type does not match public key type"))
   325  		}
   326  		if pub.N.Cmp(priv.N) != 0 {
   327  			return fail(errors.New("tls: private key does not match public key"))
   328  		}
   329  	case *ecdsa.PublicKey:
   330  		priv, ok := cert.PrivateKey.(*ecdsa.PrivateKey)
   331  		if !ok {
   332  			return fail(errors.New("tls: private key type does not match public key type"))
   333  		}
   334  		if pub.X.Cmp(priv.X) != 0 || pub.Y.Cmp(priv.Y) != 0 {
   335  			return fail(errors.New("tls: private key does not match public key"))
   336  		}
   337  	case ed25519.PublicKey:
   338  		priv, ok := cert.PrivateKey.(ed25519.PrivateKey)
   339  		if !ok {
   340  			return fail(errors.New("tls: private key type does not match public key type"))
   341  		}
   342  		if !bytes.Equal(priv.Public().(ed25519.PublicKey), pub) {
   343  			return fail(errors.New("tls: private key does not match public key"))
   344  		}
   345  	default:
   346  		return fail(errors.New("tls: unknown public key algorithm"))
   347  	}
   348  
   349  	return cert, nil
   350  }
   351  
   352  // Attempt to parse the given private key DER block. OpenSSL 0.9.8 generates
   353  // PKCS #1 private keys by default, while OpenSSL 1.0.0 generates PKCS #8 keys.
   354  // OpenSSL ecparam generates SEC1 EC private keys for ECDSA. We try all three.
   355  func parsePrivateKey(der []byte) (crypto.PrivateKey, error) {
   356  	if key, err := x509.ParsePKCS1PrivateKey(der); err == nil {
   357  		return key, nil
   358  	}
   359  	if key, err := x509.ParsePKCS8PrivateKey(der); err == nil {
   360  		switch key := key.(type) {
   361  		case *rsa.PrivateKey, *ecdsa.PrivateKey, ed25519.PrivateKey:
   362  			return key, nil
   363  		default:
   364  			return nil, errors.New("tls: found unknown private key type in PKCS#8 wrapping")
   365  		}
   366  	}
   367  	if key, err := x509.ParseECPrivateKey(der); err == nil {
   368  		return key, nil
   369  	}
   370  
   371  	return nil, errors.New("tls: failed to parse private key")
   372  }
   373
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