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Source file src/crypto/tls/tls.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 partially implements TLS 1.2, as specified in RFC 5246,
     6  // and TLS 1.3, as specified in RFC 8446.
     7  //
     8  // TLS 1.3 is available only on an opt-in basis in Go 1.12. To enable
     9  // it, set the GODEBUG environment variable (comma-separated key=value
    10  // options) such that it includes "tls13=1". To enable it from within
    11  // the process, set the environment variable before any use of TLS:
    12  //
    13  //     func init() {
    14  //         os.Setenv("GODEBUG", os.Getenv("GODEBUG")+",tls13=1")
    15  //     }
    16  package tls
    17  
    18  // BUG(agl): The crypto/tls package only implements some countermeasures
    19  // against Lucky13 attacks on CBC-mode encryption, and only on SHA1
    20  // variants. See http://www.isg.rhul.ac.uk/tls/TLStiming.pdf and
    21  // https://www.imperialviolet.org/2013/02/04/luckythirteen.html.
    22  
    23  import (
    24  	"crypto"
    25  	"crypto/ecdsa"
    26  	"crypto/rsa"
    27  	"crypto/x509"
    28  	"encoding/pem"
    29  	"errors"
    30  	"fmt"
    31  	"io/ioutil"
    32  	"net"
    33  	"strings"
    34  	"time"
    35  )
    36  
    37  // Server returns a new TLS server side connection
    38  // using conn as the underlying transport.
    39  // The configuration config must be non-nil and must include
    40  // at least one certificate or else set GetCertificate.
    41  func Server(conn net.Conn, config *Config) *Conn {
    42  	return &Conn{conn: conn, config: config}
    43  }
    44  
    45  // Client returns a new TLS client side connection
    46  // using conn as the underlying transport.
    47  // The config cannot be nil: users must set either ServerName or
    48  // InsecureSkipVerify in the config.
    49  func Client(conn net.Conn, config *Config) *Conn {
    50  	return &Conn{conn: conn, config: config, isClient: true}
    51  }
    52  
    53  // A listener implements a network listener (net.Listener) for TLS connections.
    54  type listener struct {
    55  	net.Listener
    56  	config *Config
    57  }
    58  
    59  // Accept waits for and returns the next incoming TLS connection.
    60  // The returned connection is of type *Conn.
    61  func (l *listener) Accept() (net.Conn, error) {
    62  	c, err := l.Listener.Accept()
    63  	if err != nil {
    64  		return nil, err
    65  	}
    66  	return Server(c, l.config), nil
    67  }
    68  
    69  // NewListener creates a Listener which accepts connections from an inner
    70  // Listener and wraps each connection with Server.
    71  // The configuration config must be non-nil and must include
    72  // at least one certificate or else set GetCertificate.
    73  func NewListener(inner net.Listener, config *Config) net.Listener {
    74  	l := new(listener)
    75  	l.Listener = inner
    76  	l.config = config
    77  	return l
    78  }
    79  
    80  // Listen creates a TLS listener accepting connections on the
    81  // given network address using net.Listen.
    82  // The configuration config must be non-nil and must include
    83  // at least one certificate or else set GetCertificate.
    84  func Listen(network, laddr string, config *Config) (net.Listener, error) {
    85  	if config == nil || (len(config.Certificates) == 0 && config.GetCertificate == nil) {
    86  		return nil, errors.New("tls: neither Certificates nor GetCertificate set in Config")
    87  	}
    88  	l, err := net.Listen(network, laddr)
    89  	if err != nil {
    90  		return nil, err
    91  	}
    92  	return NewListener(l, config), nil
    93  }
    94  
    95  type timeoutError struct{}
    96  
    97  func (timeoutError) Error() string   { return "tls: DialWithDialer timed out" }
    98  func (timeoutError) Timeout() bool   { return true }
    99  func (timeoutError) Temporary() bool { return true }
   100  
   101  // DialWithDialer connects to the given network address using dialer.Dial and
   102  // then initiates a TLS handshake, returning the resulting TLS connection. Any
   103  // timeout or deadline given in the dialer apply to connection and TLS
   104  // handshake as a whole.
   105  //
   106  // DialWithDialer interprets a nil configuration as equivalent to the zero
   107  // configuration; see the documentation of Config for the defaults.
   108  func DialWithDialer(dialer *net.Dialer, network, addr string, config *Config) (*Conn, error) {
   109  	// We want the Timeout and Deadline values from dialer to cover the
   110  	// whole process: TCP connection and TLS handshake. This means that we
   111  	// also need to start our own timers now.
   112  	timeout := dialer.Timeout
   113  
   114  	if !dialer.Deadline.IsZero() {
   115  		deadlineTimeout := time.Until(dialer.Deadline)
   116  		if timeout == 0 || deadlineTimeout < timeout {
   117  			timeout = deadlineTimeout
   118  		}
   119  	}
   120  
   121  	var errChannel chan error
   122  
   123  	if timeout != 0 {
   124  		errChannel = make(chan error, 2)
   125  		time.AfterFunc(timeout, func() {
   126  			errChannel <- timeoutError{}
   127  		})
   128  	}
   129  
   130  	rawConn, err := dialer.Dial(network, addr)
   131  	if err != nil {
   132  		return nil, err
   133  	}
   134  
   135  	colonPos := strings.LastIndex(addr, ":")
   136  	if colonPos == -1 {
   137  		colonPos = len(addr)
   138  	}
   139  	hostname := addr[:colonPos]
   140  
   141  	if config == nil {
   142  		config = defaultConfig()
   143  	}
   144  	// If no ServerName is set, infer the ServerName
   145  	// from the hostname we're connecting to.
   146  	if config.ServerName == "" {
   147  		// Make a copy to avoid polluting argument or default.
   148  		c := config.Clone()
   149  		c.ServerName = hostname
   150  		config = c
   151  	}
   152  
   153  	conn := Client(rawConn, config)
   154  
   155  	if timeout == 0 {
   156  		err = conn.Handshake()
   157  	} else {
   158  		go func() {
   159  			errChannel <- conn.Handshake()
   160  		}()
   161  
   162  		err = <-errChannel
   163  	}
   164  
   165  	if err != nil {
   166  		rawConn.Close()
   167  		return nil, err
   168  	}
   169  
   170  	return conn, nil
   171  }
   172  
   173  // Dial connects to the given network address using net.Dial
   174  // and then initiates a TLS handshake, returning the resulting
   175  // TLS connection.
   176  // Dial interprets a nil configuration as equivalent to
   177  // the zero configuration; see the documentation of Config
   178  // for the defaults.
   179  func Dial(network, addr string, config *Config) (*Conn, error) {
   180  	return DialWithDialer(new(net.Dialer), network, addr, config)
   181  }
   182  
   183  // LoadX509KeyPair reads and parses a public/private key pair from a pair
   184  // of files. The files must contain PEM encoded data. The certificate file
   185  // may contain intermediate certificates following the leaf certificate to
   186  // form a certificate chain. On successful return, Certificate.Leaf will
   187  // be nil because the parsed form of the certificate is not retained.
   188  func LoadX509KeyPair(certFile, keyFile string) (Certificate, error) {
   189  	certPEMBlock, err := ioutil.ReadFile(certFile)
   190  	if err != nil {
   191  		return Certificate{}, err
   192  	}
   193  	keyPEMBlock, err := ioutil.ReadFile(keyFile)
   194  	if err != nil {
   195  		return Certificate{}, err
   196  	}
   197  	return X509KeyPair(certPEMBlock, keyPEMBlock)
   198  }
   199  
   200  // X509KeyPair parses a public/private key pair from a pair of
   201  // PEM encoded data. On successful return, Certificate.Leaf will be nil because
   202  // the parsed form of the certificate is not retained.
   203  func X509KeyPair(certPEMBlock, keyPEMBlock []byte) (Certificate, error) {
   204  	fail := func(err error) (Certificate, error) { return Certificate{}, err }
   205  
   206  	var cert Certificate
   207  	var skippedBlockTypes []string
   208  	for {
   209  		var certDERBlock *pem.Block
   210  		certDERBlock, certPEMBlock = pem.Decode(certPEMBlock)
   211  		if certDERBlock == nil {
   212  			break
   213  		}
   214  		if certDERBlock.Type == "CERTIFICATE" {
   215  			cert.Certificate = append(cert.Certificate, certDERBlock.Bytes)
   216  		} else {
   217  			skippedBlockTypes = append(skippedBlockTypes, certDERBlock.Type)
   218  		}
   219  	}
   220  
   221  	if len(cert.Certificate) == 0 {
   222  		if len(skippedBlockTypes) == 0 {
   223  			return fail(errors.New("tls: failed to find any PEM data in certificate input"))
   224  		}
   225  		if len(skippedBlockTypes) == 1 && strings.HasSuffix(skippedBlockTypes[0], "PRIVATE KEY") {
   226  			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"))
   227  		}
   228  		return fail(fmt.Errorf("tls: failed to find \"CERTIFICATE\" PEM block in certificate input after skipping PEM blocks of the following types: %v", skippedBlockTypes))
   229  	}
   230  
   231  	skippedBlockTypes = skippedBlockTypes[:0]
   232  	var keyDERBlock *pem.Block
   233  	for {
   234  		keyDERBlock, keyPEMBlock = pem.Decode(keyPEMBlock)
   235  		if keyDERBlock == nil {
   236  			if len(skippedBlockTypes) == 0 {
   237  				return fail(errors.New("tls: failed to find any PEM data in key input"))
   238  			}
   239  			if len(skippedBlockTypes) == 1 && skippedBlockTypes[0] == "CERTIFICATE" {
   240  				return fail(errors.New("tls: found a certificate rather than a key in the PEM for the private key"))
   241  			}
   242  			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))
   243  		}
   244  		if keyDERBlock.Type == "PRIVATE KEY" || strings.HasSuffix(keyDERBlock.Type, " PRIVATE KEY") {
   245  			break
   246  		}
   247  		skippedBlockTypes = append(skippedBlockTypes, keyDERBlock.Type)
   248  	}
   249  
   250  	// We don't need to parse the public key for TLS, but we so do anyway
   251  	// to check that it looks sane and matches the private key.
   252  	x509Cert, err := x509.ParseCertificate(cert.Certificate[0])
   253  	if err != nil {
   254  		return fail(err)
   255  	}
   256  
   257  	cert.PrivateKey, err = parsePrivateKey(keyDERBlock.Bytes)
   258  	if err != nil {
   259  		return fail(err)
   260  	}
   261  
   262  	switch pub := x509Cert.PublicKey.(type) {
   263  	case *rsa.PublicKey:
   264  		priv, ok := cert.PrivateKey.(*rsa.PrivateKey)
   265  		if !ok {
   266  			return fail(errors.New("tls: private key type does not match public key type"))
   267  		}
   268  		if pub.N.Cmp(priv.N) != 0 {
   269  			return fail(errors.New("tls: private key does not match public key"))
   270  		}
   271  	case *ecdsa.PublicKey:
   272  		priv, ok := cert.PrivateKey.(*ecdsa.PrivateKey)
   273  		if !ok {
   274  			return fail(errors.New("tls: private key type does not match public key type"))
   275  		}
   276  		if pub.X.Cmp(priv.X) != 0 || pub.Y.Cmp(priv.Y) != 0 {
   277  			return fail(errors.New("tls: private key does not match public key"))
   278  		}
   279  	default:
   280  		return fail(errors.New("tls: unknown public key algorithm"))
   281  	}
   282  
   283  	return cert, nil
   284  }
   285  
   286  // Attempt to parse the given private key DER block. OpenSSL 0.9.8 generates
   287  // PKCS#1 private keys by default, while OpenSSL 1.0.0 generates PKCS#8 keys.
   288  // OpenSSL ecparam generates SEC1 EC private keys for ECDSA. We try all three.
   289  func parsePrivateKey(der []byte) (crypto.PrivateKey, error) {
   290  	if key, err := x509.ParsePKCS1PrivateKey(der); err == nil {
   291  		return key, nil
   292  	}
   293  	if key, err := x509.ParsePKCS8PrivateKey(der); err == nil {
   294  		switch key := key.(type) {
   295  		case *rsa.PrivateKey, *ecdsa.PrivateKey:
   296  			return key, nil
   297  		default:
   298  			return nil, errors.New("tls: found unknown private key type in PKCS#8 wrapping")
   299  		}
   300  	}
   301  	if key, err := x509.ParseECPrivateKey(der); err == nil {
   302  		return key, nil
   303  	}
   304  
   305  	return nil, errors.New("tls: failed to parse private key")
   306  }
   307  

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