tls.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

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

// BUG(agl): The crypto/tls package only implements some countermeasures
// against Lucky13 attacks on CBC-mode encryption, and only on SHA1
// variants. See http://www.isg.rhul.ac.uk/tls/TLStiming.pdf and
// https://www.imperialviolet.org/2013/02/04/luckythirteen.html.

import (
	"bytes"
	"crypto"
	"crypto/ecdsa"
	"crypto/ed25519"
	"crypto/rsa"
	"crypto/x509"
	"encoding/pem"
	"errors"
	"fmt"
	"io/ioutil"
	"net"
	"strings"
)

type conn interface {
	Write([]byte) (int, error)
	RemoteAddr() net.Addr
}

// 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 Server(c conn, in, out **MsgBuffer, config *Config) (*Conn, error) {
	tlsconn := &Conn{
		conn:    c,
		config:  config,
		input:   in,
		sendBuf: out,
		outBuf:  []byte{0, 3, 3, 0, 0},
	}

	return tlsconn, nil
}
func Client(c conn, in, out **MsgBuffer, config *Config) *Conn {
	tlsconn := &Conn{
		conn:     c,
		config:   config,
		input:    in,
		sendBuf:  out,
		outBuf:   []byte{0, 3, 3, 0, 0},
		isClient: true,
	}
	return tlsconn
}

// 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.

type timeoutError struct{}

func (timeoutError) Error() string   { return "tls: DialWithDialer timed out" }
func (timeoutError) Timeout() bool   { return true }
func (timeoutError) Temporary() bool { return true }

// 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 LoadX509KeyPair(certFile, keyFile string) (Certificate, error) {
	certPEMBlock, err := ioutil.ReadFile(certFile)
	if err != nil {
		return Certificate{}, err
	}
	keyPEMBlock, err := ioutil.ReadFile(keyFile)
	if err != nil {
		return Certificate{}, err
	}
	return X509KeyPair(certPEMBlock, keyPEMBlock)
}

// 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.
func X509KeyPair(certPEMBlock, keyPEMBlock []byte) (Certificate, error) {
	fail := func(err error) (Certificate, error) { return Certificate{}, err }

	var cert Certificate
	var skippedBlockTypes []string
	for {
		var certDERBlock *pem.Block
		certDERBlock, certPEMBlock = pem.Decode(certPEMBlock)
		if certDERBlock == nil {
			break
		}
		if certDERBlock.Type == "CERTIFICATE" {
			cert.Certificate = append(cert.Certificate, certDERBlock.Bytes)
		} else {
			skippedBlockTypes = append(skippedBlockTypes, certDERBlock.Type)
		}
	}

	if len(cert.Certificate) == 0 {
		if len(skippedBlockTypes) == 0 {
			return fail(errors.New("tls: failed to find any PEM data in certificate input"))
		}
		if len(skippedBlockTypes) == 1 && strings.HasSuffix(skippedBlockTypes[0], "PRIVATE KEY") {
			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"))
		}
		return fail(fmt.Errorf("tls: failed to find \"CERTIFICATE\" PEM block in certificate input after skipping PEM blocks of the following types: %v", skippedBlockTypes))
	}

	skippedBlockTypes = skippedBlockTypes[:0]
	var keyDERBlock *pem.Block
	for {
		keyDERBlock, keyPEMBlock = pem.Decode(keyPEMBlock)
		if keyDERBlock == nil {
			if len(skippedBlockTypes) == 0 {
				return fail(errors.New("tls: failed to find any PEM data in key input"))
			}
			if len(skippedBlockTypes) == 1 && skippedBlockTypes[0] == "CERTIFICATE" {
				return fail(errors.New("tls: found a certificate rather than a key in the PEM for the private key"))
			}
			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))
		}
		if keyDERBlock.Type == "PRIVATE KEY" || strings.HasSuffix(keyDERBlock.Type, " PRIVATE KEY") {
			break
		}
		skippedBlockTypes = append(skippedBlockTypes, keyDERBlock.Type)
	}

	// We don't need to parse the public key for TLS, but we so do anyway
	// to check that it looks sane and matches the private key.
	x509Cert, err := x509.ParseCertificate(cert.Certificate[0])
	if err != nil {
		return fail(err)
	}

	cert.PrivateKey, err = parsePrivateKey(keyDERBlock.Bytes)
	if err != nil {
		return fail(err)
	}

	switch pub := x509Cert.PublicKey.(type) {
	case *rsa.PublicKey:
		priv, ok := cert.PrivateKey.(*rsa.PrivateKey)
		if !ok {
			return fail(errors.New("tls: private key type does not match public key type"))
		}
		if pub.N.Cmp(priv.N) != 0 {
			return fail(errors.New("tls: private key does not match public key"))
		}
	case *ecdsa.PublicKey:
		priv, ok := cert.PrivateKey.(*ecdsa.PrivateKey)
		if !ok {
			return fail(errors.New("tls: private key type does not match public key type"))
		}
		if pub.X.Cmp(priv.X) != 0 || pub.Y.Cmp(priv.Y) != 0 {
			return fail(errors.New("tls: private key does not match public key"))
		}
	case ed25519.PublicKey:
		priv, ok := cert.PrivateKey.(ed25519.PrivateKey)
		if !ok {
			return fail(errors.New("tls: private key type does not match public key type"))
		}
		if !bytes.Equal(priv.Public().(ed25519.PublicKey), pub) {
			return fail(errors.New("tls: private key does not match public key"))
		}
	default:
		return fail(errors.New("tls: unknown public key algorithm"))
	}

	return cert, nil
}

// Attempt to parse the given private key DER block. OpenSSL 0.9.8 generates
// PKCS#1 private keys by default, while OpenSSL 1.0.0 generates PKCS#8 keys.
// OpenSSL ecparam generates SEC1 EC private keys for ECDSA. We try all three.
func parsePrivateKey(der []byte) (crypto.PrivateKey, error) {
	if key, err := x509.ParsePKCS1PrivateKey(der); err == nil {
		return key, nil
	}
	if key, err := x509.ParsePKCS8PrivateKey(der); err == nil {
		switch key := key.(type) {
		case *rsa.PrivateKey, *ecdsa.PrivateKey, ed25519.PrivateKey:
			return key, nil
		default:
			return nil, errors.New("tls: found unknown private key type in PKCS#8 wrapping")
		}
	}
	if key, err := x509.ParseECPrivateKey(der); err == nil {
		return key, nil
	}

	return nil, errors.New("tls: failed to parse private key")
}