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crypto/tls: client certificate support.

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This changeset implements client certificate support in crypto/tls
for both handshake_server.go and handshake_client.go

The updated server implementation sends an empty CertificateAuthorities
field in the CertificateRequest, thus allowing clients to send any
certificates they wish. Likewise, the client code will only respond
with its certificate when the server requests a certificate with this
field empty.

R=agl, rsc, agl1
CC=golang-dev
https://golang.org/cl/1975042
This commit is contained in:
Mikkel Krautz 2010-08-16 11:22:22 -04:00 committed by Adam Langley
parent 10589a7c24
commit e85c1c3393
6 changed files with 348 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
common.go
View File

@ -38,10 +38,12 @@ const (
typeClientHello uint8 = 1
typeServerHello uint8 = 2
typeCertificate uint8 = 11
typeCertificateStatus uint8 = 22
typeCertificateRequest uint8 = 13
typeServerHelloDone uint8 = 14
typeCertificateVerify uint8 = 15
typeClientKeyExchange uint8 = 16
typeFinished uint8 = 20
typeCertificateStatus uint8 = 22
typeNextProtocol uint8 = 67 // Not IANA assigned
)
@ -67,6 +69,15 @@ const (
statusTypeOCSP uint8 = 1
)
// Certificate types (for certificateRequestMsg)
const (
certTypeRSASign = 1 // A certificate containing an RSA key
certTypeDSSSign = 2 // A certificate containing a DSA key
certTypeRSAFixedDH = 3 // A certificate containing a static DH key
certTypeDSSFixedDH = 4 // A certficiate containing a static DH key
// Rest of these are reserved by the TLS spec
)
type ConnectionState struct {
HandshakeComplete bool
CipherSuite uint16
@ -80,6 +91,7 @@ type Config struct {
Rand io.Reader
// Time returns the current time as the number of seconds since the epoch.
Time func() int64
// Certificates contains one or more certificate chains.
Certificates []Certificate
RootCAs *CASet
// NextProtos is a list of supported, application level protocols.
@ -88,9 +100,16 @@ type Config struct {
// ServerName is included in the client's handshake to support virtual
// hosting.
ServerName string
// AuthenticateClient determines if a server will request a certificate
// from the client. It does not require that the client send a
// certificate nor, if it does, that the certificate is anything more
// than self-signed.
AuthenticateClient bool
}
type Certificate struct {
// Certificate contains a chain of one or more certificates. Leaf
// certificate first.
Certificate [][]byte
PrivateKey *rsa.PrivateKey
}

4
conn.go
View File

@ -534,12 +534,16 @@ func (c *Conn) readHandshake() (interface{}, os.Error) {
m = new(serverHelloMsg)
case typeCertificate:
m = new(certificateMsg)
case typeCertificateRequest:
m = new(certificateRequestMsg)
case typeCertificateStatus:
m = new(certificateStatusMsg)
case typeServerHelloDone:
m = new(serverHelloDoneMsg)
case typeClientKeyExchange:
m = new(clientKeyExchangeMsg)
case typeCertificateVerify:
m = new(certificateVerifyMsg)
case typeNextProtocol:
m = new(nextProtoMsg)
case typeFinished:

67
handshake_client.go
View File

@ -130,12 +130,64 @@ func (c *Conn) clientHandshake() os.Error {
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)
@ -153,6 +205,21 @@ func (c *Conn) clientHandshake() os.Error {
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)

150
handshake_messages.go
View File

@ -668,3 +668,153 @@ func (m *nextProtoMsg) unmarshal(data []byte) bool {
return true
}
type certificateRequestMsg struct {
raw []byte
certificateTypes []byte
certificateAuthorities [][]byte
}
func (m *certificateRequestMsg) marshal() (x []byte) {
if m.raw != nil {
return m.raw
}
// See http://tools.ietf.org/html/rfc4346#section-7.4.4
length := 1 + len(m.certificateTypes) + 2
for _, ca := range m.certificateAuthorities {
length += 2 + len(ca)
}
x = make([]byte, 4+length)
x[0] = typeCertificateRequest
x[1] = uint8(length >> 16)
x[2] = uint8(length >> 8)
x[3] = uint8(length)
x[4] = uint8(len(m.certificateTypes))
copy(x[5:], m.certificateTypes)
y := x[5+len(m.certificateTypes):]
numCA := len(m.certificateAuthorities)
y[0] = uint8(numCA >> 8)
y[1] = uint8(numCA)
y = y[2:]
for _, ca := range m.certificateAuthorities {
y[0] = uint8(len(ca) >> 8)
y[1] = uint8(len(ca))
y = y[2:]
copy(y, ca)
y = y[len(ca):]
}
m.raw = x
return
}
func (m *certificateRequestMsg) unmarshal(data []byte) bool {
m.raw = data
if len(data) < 5 {
return false
}
length := uint32(data[1])<<16 | uint32(data[2])<<8 | uint32(data[3])
if uint32(len(data))-4 != length {
return false
}
numCertTypes := int(data[4])
data = data[5:]
if numCertTypes == 0 || len(data) <= numCertTypes {
return false
}
m.certificateTypes = make([]byte, numCertTypes)
if copy(m.certificateTypes, data) != numCertTypes {
return false
}
data = data[numCertTypes:]
if len(data) < 2 {
return false
}
numCAs := uint16(data[0])<<16 | uint16(data[1])
data = data[2:]
m.certificateAuthorities = make([][]byte, numCAs)
for i := uint16(0); i < numCAs; i++ {
if len(data) < 2 {
return false
}
caLen := uint16(data[0])<<16 | uint16(data[1])
data = data[2:]
if len(data) < int(caLen) {
return false
}
ca := make([]byte, caLen)
copy(ca, data)
m.certificateAuthorities[i] = ca
data = data[caLen:]
}
if len(data) > 0 {
return false
}
return true
}
type certificateVerifyMsg struct {
raw []byte
signature []byte
}
func (m *certificateVerifyMsg) marshal() (x []byte) {
if m.raw != nil {
return m.raw
}
// See http://tools.ietf.org/html/rfc4346#section-7.4.8
siglength := len(m.signature)
length := 2 + siglength
x = make([]byte, 4+length)
x[0] = typeCertificateVerify
x[1] = uint8(length >> 16)
x[2] = uint8(length >> 8)
x[3] = uint8(length)
x[4] = uint8(siglength >> 8)
x[5] = uint8(siglength)
copy(x[6:], m.signature)
m.raw = x
return
}
func (m *certificateVerifyMsg) unmarshal(data []byte) bool {
m.raw = data
if len(data) < 6 {
return false
}
length := uint32(data[1])<<16 | uint32(data[2])<<8 | uint32(data[3])
if uint32(len(data))-4 != length {
return false
}
siglength := int(data[4])<<8 + int(data[5])
if len(data)-6 != siglength {
return false
}
m.signature = data[6:]
return true
}

19
handshake_messages_test.go
View File

@ -16,6 +16,8 @@ var tests = []interface{}{
&serverHelloMsg{},
&certificateMsg{},
&certificateRequestMsg{},
&certificateVerifyMsg{},
&certificateStatusMsg{},
&clientKeyExchangeMsg{},
&finishedMsg{},
@ -148,6 +150,23 @@ func (*certificateMsg) Generate(rand *rand.Rand, size int) reflect.Value {
return reflect.NewValue(m)
}
func (*certificateRequestMsg) Generate(rand *rand.Rand, size int) reflect.Value {
m := &certificateRequestMsg{}
m.certificateTypes = randomBytes(rand.Intn(5)+1, rand)
numCAs := rand.Intn(100)
m.certificateAuthorities = make([][]byte, numCAs)
for i := 0; i < numCAs; i++ {
m.certificateAuthorities[i] = randomBytes(rand.Intn(15)+1, rand)
}
return reflect.NewValue(m)
}
func (*certificateVerifyMsg) Generate(rand *rand.Rand, size int) reflect.Value {
m := &certificateVerifyMsg{}
m.signature = randomBytes(rand.Intn(15)+1, rand)
return reflect.NewValue(m)
}
func (*certificateStatusMsg) Generate(rand *rand.Rand, size int) reflect.Value {
m := &certificateStatusMsg{}
if rand.Intn(10) > 5 {

80
handshake_server.go
View File

@ -18,6 +18,7 @@ import (
"crypto/rsa"
"crypto/sha1"
"crypto/subtle"
"crypto/x509"
"io"
"os"
)
@ -112,10 +113,62 @@ func (c *Conn) serverHandshake() os.Error {
finishedHash.Write(certMsg.marshal())
c.writeRecord(recordTypeHandshake, certMsg.marshal())
if config.AuthenticateClient {
// Request a client certificate
certReq := new(certificateRequestMsg)
certReq.certificateTypes = []byte{certTypeRSASign}
// An empty list of certificateAuthorities signals to
// the client that it may send any certificate in response
// to our request.
finishedHash.Write(certReq.marshal())
c.writeRecord(recordTypeHandshake, certReq.marshal())
}
helloDone := new(serverHelloDoneMsg)
finishedHash.Write(helloDone.marshal())
c.writeRecord(recordTypeHandshake, helloDone.marshal())
var pub *rsa.PublicKey
if config.AuthenticateClient {
// Get client certificate
msg, err = c.readHandshake()
if err != nil {
return err
}
certMsg, ok = msg.(*certificateMsg)
if !ok {
return c.sendAlert(alertUnexpectedMessage)
}
finishedHash.Write(certMsg.marshal())
certs := make([]*x509.Certificate, len(certMsg.certificates))
for i, asn1Data := range certMsg.certificates {
cert, err := x509.ParseCertificate(asn1Data)
if err != nil {
return c.sendAlert(alertBadCertificate)
}
certs[i] = cert
}
// TODO(agl): do better validation of certs: max path length, name restrictions etc.
for i := 1; i < len(certs); i++ {
if err := certs[i-1].CheckSignatureFrom(certs[i]); err != nil {
return c.sendAlert(alertBadCertificate)
}
}
if len(certs) > 0 {
key, ok := certs[0].PublicKey.(*rsa.PublicKey)
if !ok {
return c.sendAlert(alertUnsupportedCertificate)
}
pub = key
c.peerCertificates = certs
}
}
// Get client key exchange
msg, err = c.readHandshake()
if err != nil {
return err
@ -126,6 +179,33 @@ func (c *Conn) serverHandshake() os.Error {
}
finishedHash.Write(ckx.marshal())
// If we received a client cert in response to our certificate request message,
// the client will send us a certificateVerifyMsg immediately after the
// clientKeyExchangeMsg. This message is a MD5SHA1 digest of all preceeding
// handshake-layer messages that is signed using the private key corresponding
// to the client's certificate. This allows us to verify that the client is in
// posession of the private key of the certificate.
if len(c.peerCertificates) > 0 {
msg, err = c.readHandshake()
if err != nil {
return err
}
certVerify, ok := msg.(*certificateVerifyMsg)
if !ok {
return c.sendAlert(alertUnexpectedMessage)
}
digest := make([]byte, 36)
copy(digest[0:16], finishedHash.serverMD5.Sum())
copy(digest[16:36], finishedHash.serverSHA1.Sum())
err = rsa.VerifyPKCS1v15(pub, rsa.HashMD5SHA1, digest, certVerify.signature)
if err != nil {
return c.sendAlert(alertBadCertificate)
}
finishedHash.Write(certVerify.marshal())
}
preMasterSecret := make([]byte, 48)
_, err = io.ReadFull(config.Rand, preMasterSecret[2:])
if err != nil {