blob: 4cddba3303079355679525cc9b270952dbc12880 [file] [log] [blame]
// 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
import (
"crypto/hmac"
"crypto/rc4"
"crypto/rsa"
"crypto/subtle"
"crypto/x509"
"io"
"os"
)
func (c *Conn) clientHandshake() os.Error {
finishedHash := newFinishedHash()
if c.config == nil {
c.config = defaultConfig()
}
hello := &clientHelloMsg{
vers: maxVersion,
cipherSuites: []uint16{TLS_RSA_WITH_RC4_128_SHA},
compressionMethods: []uint8{compressionNone},
random: make([]byte, 32),
ocspStapling: true,
serverName: c.config.ServerName,
}
t := uint32(c.config.time())
hello.random[0] = byte(t >> 24)
hello.random[1] = byte(t >> 16)
hello.random[2] = byte(t >> 8)
hello.random[3] = byte(t)
_, err := io.ReadFull(c.config.rand(), hello.random[4:])
if err != nil {
c.sendAlert(alertInternalError)
return os.ErrorString("short read from Rand")
}
finishedHash.Write(hello.marshal())
c.writeRecord(recordTypeHandshake, hello.marshal())
msg, err := c.readHandshake()
if err != nil {
return err
}
serverHello, ok := msg.(*serverHelloMsg)
if !ok {
return c.sendAlert(alertUnexpectedMessage)
}
finishedHash.Write(serverHello.marshal())
vers, ok := mutualVersion(serverHello.vers)
if !ok {
c.sendAlert(alertProtocolVersion)
}
c.vers = vers
c.haveVers = true
if serverHello.cipherSuite != TLS_RSA_WITH_RC4_128_SHA ||
serverHello.compressionMethod != compressionNone {
return c.sendAlert(alertUnexpectedMessage)
}
msg, err = c.readHandshake()
if err != nil {
return err
}
certMsg, ok := msg.(*certificateMsg)
if !ok || len(certMsg.certificates) == 0 {
return c.sendAlert(alertUnexpectedMessage)
}
finishedHash.Write(certMsg.marshal())
certs := make([]*x509.Certificate, len(certMsg.certificates))
chain := NewCASet()
for i, asn1Data := range certMsg.certificates {
cert, err := x509.ParseCertificate(asn1Data)
if err != nil {
c.sendAlert(alertBadCertificate)
return os.ErrorString("failed to parse certificate from server: " + err.String())
}
certs[i] = cert
chain.AddCert(cert)
}
// If we don't have a root CA set configured then anything is accepted.
// TODO(rsc): Find certificates for OS X 10.6.
for cur := certs[0]; c.config.RootCAs != nil; {
parent := c.config.RootCAs.FindVerifiedParent(cur)
if parent != nil {
break
}
parent = chain.FindVerifiedParent(cur)
if parent == nil {
c.sendAlert(alertBadCertificate)
return os.ErrorString("could not find root certificate for chain")
}
if !parent.BasicConstraintsValid || !parent.IsCA {
c.sendAlert(alertBadCertificate)
return os.ErrorString("intermediate certificate does not have CA bit set")
}
// KeyUsage status flags are ignored. From Engineering
// Security, Peter Gutmann: A European government CA marked its
// signing certificates as being valid for encryption only, but
// no-one noticed. Another European CA marked its signature
// keys as not being valid for signatures. A different CA
// marked its own trusted root certificate as being invalid for
// certificate signing. Another national CA distributed a
// certificate to be used to encrypt data for the country’s tax
// authority that was marked as only being usable for digital
// signatures but not for encryption. Yet another CA reversed
// the order of the bit flags in the keyUsage due to confusion
// over encoding endianness, essentially setting a random
// keyUsage in certificates that it issued. Another CA created
// a self-invalidating certificate by adding a certificate
// policy statement stipulating that the certificate had to be
// used strictly as specified in the keyUsage, and a keyUsage
// containing a flag indicating that the RSA encryption key
// could only be used for Diffie-Hellman key agreement.
cur = parent
}
pub, ok := certs[0].PublicKey.(*rsa.PublicKey)
if !ok {
return c.sendAlert(alertUnsupportedCertificate)
}
c.peerCertificates = certs
if serverHello.certStatus {
msg, err = c.readHandshake()
if err != nil {
return err
}
cs, ok := msg.(*certificateStatusMsg)
if !ok {
return c.sendAlert(alertUnexpectedMessage)
}
finishedHash.Write(cs.marshal())
if cs.statusType == statusTypeOCSP {
c.ocspResponse = cs.response
}
}
msg, err = c.readHandshake()
if err != nil {
return err
}
transmitCert := false
certReq, ok := msg.(*certificateRequestMsg)
if ok {
// We only accept certificates with RSA keys.
rsaAvail := false
for _, certType := range certReq.certificateTypes {
if certType == certTypeRSASign {
rsaAvail = true
break
}
}
// For now, only send a certificate back if the server gives us an
// empty list of certificateAuthorities.
//
// RFC 4346 on the certificateAuthorities field:
// A list of the distinguished names of acceptable certificate
// authorities. These distinguished names may specify a desired
// distinguished name for a root CA or for a subordinate CA; thus,
// this message can be used to describe both known roots and a
// desired authorization space. If the certificate_authorities
// list is empty then the client MAY send any certificate of the
// appropriate ClientCertificateType, unless there is some
// external arrangement to the contrary.
if rsaAvail && len(certReq.certificateAuthorities) == 0 {
transmitCert = true
}
finishedHash.Write(certReq.marshal())
msg, err = c.readHandshake()
if err != nil {
return err
}
}
shd, ok := msg.(*serverHelloDoneMsg)
if !ok {
return c.sendAlert(alertUnexpectedMessage)
}
finishedHash.Write(shd.marshal())
var cert *x509.Certificate
if transmitCert {
certMsg = new(certificateMsg)
if len(c.config.Certificates) > 0 {
cert, err = x509.ParseCertificate(c.config.Certificates[0].Certificate[0])
if err == nil && cert.PublicKeyAlgorithm == x509.RSA {
certMsg.certificates = c.config.Certificates[0].Certificate
} else {
cert = nil
}
}
finishedHash.Write(certMsg.marshal())
c.writeRecord(recordTypeHandshake, certMsg.marshal())
}
ckx := new(clientKeyExchangeMsg)
preMasterSecret := make([]byte, 48)
preMasterSecret[0] = byte(hello.vers >> 8)
preMasterSecret[1] = byte(hello.vers)
_, err = io.ReadFull(c.config.rand(), preMasterSecret[2:])
if err != nil {
return c.sendAlert(alertInternalError)
}
ckx.ciphertext, err = rsa.EncryptPKCS1v15(c.config.rand(), pub, preMasterSecret)
if err != nil {
return c.sendAlert(alertInternalError)
}
finishedHash.Write(ckx.marshal())
c.writeRecord(recordTypeHandshake, ckx.marshal())
if cert != nil {
certVerify := new(certificateVerifyMsg)
var digest [36]byte
copy(digest[0:16], finishedHash.serverMD5.Sum())
copy(digest[16:36], finishedHash.serverSHA1.Sum())
signed, err := rsa.SignPKCS1v15(c.config.rand(), c.config.Certificates[0].PrivateKey, rsa.HashMD5SHA1, digest[0:])
if err != nil {
return c.sendAlert(alertInternalError)
}
certVerify.signature = signed
finishedHash.Write(certVerify.marshal())
c.writeRecord(recordTypeHandshake, certVerify.marshal())
}
suite := cipherSuites[0]
masterSecret, clientMAC, serverMAC, clientKey, serverKey :=
keysFromPreMasterSecret11(preMasterSecret, hello.random, serverHello.random, suite.hashLength, suite.cipherKeyLength)
cipher, _ := rc4.NewCipher(clientKey)
c.out.prepareCipherSpec(cipher, hmac.NewSHA1(clientMAC))
c.writeRecord(recordTypeChangeCipherSpec, []byte{1})
finished := new(finishedMsg)
finished.verifyData = finishedHash.clientSum(masterSecret)
finishedHash.Write(finished.marshal())
c.writeRecord(recordTypeHandshake, finished.marshal())
cipher2, _ := rc4.NewCipher(serverKey)
c.in.prepareCipherSpec(cipher2, hmac.NewSHA1(serverMAC))
c.readRecord(recordTypeChangeCipherSpec)
if c.err != nil {
return c.err
}
msg, err = c.readHandshake()
if err != nil {
return err
}
serverFinished, ok := msg.(*finishedMsg)
if !ok {
return c.sendAlert(alertUnexpectedMessage)
}
verify := finishedHash.serverSum(masterSecret)
if len(verify) != len(serverFinished.verifyData) ||
subtle.ConstantTimeCompare(verify, serverFinished.verifyData) != 1 {
return c.sendAlert(alertHandshakeFailure)
}
c.handshakeComplete = true
c.cipherSuite = TLS_RSA_WITH_RC4_128_SHA
return nil
}