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crypto/tls: add Config.GetConfigForClient
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GetConfigForClient allows the tls.Config to be updated on a per-client
basis.

Fixes golang#16066.
Fixes golang#15707.
Fixes golang#15699.

Change-Id: I2c675a443d557f969441226729f98502b38901ea
Reviewed-on: https://go-review.googlesource.com/30790
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
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@agl @bradfitz
agl authored and bradfitz committed Oct 18, 2016
1 parent 51fad12 commit 0b98d05
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Showing 4 changed files with 225 additions and 32 deletions.
53 changes: 49 additions & 4 deletions common.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -303,7 +303,27 @@ type Config struct {
// If GetCertificate is nil or returns nil, then the certificate is
// retrieved from NameToCertificate. If NameToCertificate is nil, the
// first element of Certificates will be used.
GetCertificate func(clientHello *ClientHelloInfo) (*Certificate, error)
GetCertificate func(*ClientHelloInfo) (*Certificate, error)

// GetConfigForClient, if not nil, is called after a ClientHello is
// received from a client. It may return a non-nil Config in order to
// change the Config that will be used to handle this connection. If
// the returned Config is nil, the original Config will be used. The
// Config returned by this callback may not be subsequently modified.
//
// If GetConfigForClient is nil, the Config passed to Server() will be
// used for all connections.
//
// Uniquely for the fields in the returned Config, session ticket keys
// will be duplicated from the original Config if not set.
// Specifically, if SetSessionTicketKeys was called on the original
// config but not on the returned config then the ticket keys from the
// original config will be copied into the new config before use.
// Otherwise, if SessionTicketKey was set in the original config but
// not in the returned config then it will be copied into the returned
// config before use. If neither of those cases applies then the key
// material from the returned config will be used for session tickets.
GetConfigForClient func(*ClientHelloInfo) (*Config, error)

// RootCAs defines the set of root certificate authorities
// that clients use when verifying server certificates.
Expand Down Expand Up @@ -398,13 +418,17 @@ type Config struct {

serverInitOnce sync.Once // guards calling (*Config).serverInit

// mutex protects sessionTicketKeys
// mutex protects sessionTicketKeys and originalConfig.
mutex sync.RWMutex
// sessionTicketKeys contains zero or more ticket keys. If the length
// is zero, SessionTicketsDisabled must be true. The first key is used
// for new tickets and any subsequent keys can be used to decrypt old
// tickets.
sessionTicketKeys []ticketKey
// originalConfig is set to the Config that was passed to Server if
// this Config is returned by a GetConfigForClient callback. It's used
// by serverInit in order to copy session ticket keys if needed.
originalConfig *Config
}

// ticketKeyNameLen is the number of bytes of identifier that is prepended to
Expand Down Expand Up @@ -434,12 +458,18 @@ func ticketKeyFromBytes(b [32]byte) (key ticketKey) {
// Clone returns a shallow clone of c.
// Only the exported fields are copied.
func (c *Config) Clone() *Config {
var sessionTicketKeys []ticketKey
c.mutex.RLock()
sessionTicketKeys = c.sessionTicketKeys
c.mutex.RUnlock()

return &Config{
Rand: c.Rand,
Time: c.Time,
Certificates: c.Certificates,
NameToCertificate: c.NameToCertificate,
GetCertificate: c.GetCertificate,
GetConfigForClient: c.GetConfigForClient,
RootCAs: c.RootCAs,
NextProtos: c.NextProtos,
ServerName: c.ServerName,
Expand All @@ -457,6 +487,8 @@ func (c *Config) Clone() *Config {
DynamicRecordSizingDisabled: c.DynamicRecordSizingDisabled,
Renegotiation: c.Renegotiation,
KeyLogWriter: c.KeyLogWriter,
sessionTicketKeys: sessionTicketKeys,
// originalConfig is deliberately not duplicated.
}
}

Expand All @@ -465,6 +497,11 @@ func (c *Config) serverInit() {
return
}

var originalConfig *Config
c.mutex.Lock()
originalConfig, c.originalConfig = c.originalConfig, nil
c.mutex.Unlock()

alreadySet := false
for _, b := range c.SessionTicketKey {
if b != 0 {
Expand All @@ -474,13 +511,21 @@ func (c *Config) serverInit() {
}

if !alreadySet {
if _, err := io.ReadFull(c.rand(), c.SessionTicketKey[:]); err != nil {
if originalConfig != nil {
copy(c.SessionTicketKey[:], originalConfig.SessionTicketKey[:])
} else if _, err := io.ReadFull(c.rand(), c.SessionTicketKey[:]); err != nil {
c.SessionTicketsDisabled = true
return
}
}

c.sessionTicketKeys = []ticketKey{ticketKeyFromBytes(c.SessionTicketKey)}
if originalConfig != nil {
originalConfig.mutex.RLock()
c.sessionTicketKeys = originalConfig.sessionTicketKeys
originalConfig.mutex.RUnlock()
} else {
c.sessionTicketKeys = []ticketKey{ticketKeyFromBytes(c.SessionTicketKey)}
}
}

func (c *Config) ticketKeys() []ticketKey {
Expand Down
67 changes: 40 additions & 27 deletions handshake_server.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -37,11 +37,9 @@ type serverHandshakeState struct {
// serverHandshake performs a TLS handshake as a server.
// c.out.Mutex <= L; c.handshakeMutex <= L.
func (c *Conn) serverHandshake() error {
config := c.config

// If this is the first server handshake, we generate a random key to
// encrypt the tickets with.
config.serverInitOnce.Do(config.serverInit)
c.config.serverInitOnce.Do(c.config.serverInit)

hs := serverHandshakeState{
c: c,
Expand Down Expand Up @@ -112,7 +110,6 @@ func (c *Conn) serverHandshake() error {
// readClientHello reads a ClientHello message from the client and decides
// whether we will perform session resumption.
func (hs *serverHandshakeState) readClientHello() (isResume bool, err error) {
config := hs.c.config
c := hs.c

msg, err := c.readHandshake()
Expand All @@ -125,7 +122,29 @@ func (hs *serverHandshakeState) readClientHello() (isResume bool, err error) {
c.sendAlert(alertUnexpectedMessage)
return false, unexpectedMessageError(hs.clientHello, msg)
}
c.vers, ok = config.mutualVersion(hs.clientHello.vers)

clientHelloInfo := &ClientHelloInfo{
CipherSuites: hs.clientHello.cipherSuites,
ServerName: hs.clientHello.serverName,
SupportedCurves: hs.clientHello.supportedCurves,
SupportedPoints: hs.clientHello.supportedPoints,
}

if c.config.GetConfigForClient != nil {
if newConfig, err := c.config.GetConfigForClient(clientHelloInfo); err != nil {
c.sendAlert(alertInternalError)
return false, err
} else if newConfig != nil {
newConfig.mutex.Lock()
newConfig.originalConfig = c.config
newConfig.mutex.Unlock()

newConfig.serverInitOnce.Do(newConfig.serverInit)
c.config = newConfig
}
}

c.vers, ok = c.config.mutualVersion(hs.clientHello.vers)
if !ok {
c.sendAlert(alertProtocolVersion)
return false, fmt.Errorf("tls: client offered an unsupported, maximum protocol version of %x", hs.clientHello.vers)
Expand All @@ -135,7 +154,7 @@ func (hs *serverHandshakeState) readClientHello() (isResume bool, err error) {
hs.hello = new(serverHelloMsg)

supportedCurve := false
preferredCurves := config.curvePreferences()
preferredCurves := c.config.curvePreferences()
Curves:
for _, curve := range hs.clientHello.supportedCurves {
for _, supported := range preferredCurves {
Expand Down Expand Up @@ -171,7 +190,7 @@ Curves:

hs.hello.vers = c.vers
hs.hello.random = make([]byte, 32)
_, err = io.ReadFull(config.rand(), hs.hello.random)
_, err = io.ReadFull(c.config.rand(), hs.hello.random)
if err != nil {
c.sendAlert(alertInternalError)
return false, err
Expand All @@ -196,20 +215,15 @@ Curves:
} else {
// Although sending an empty NPN extension is reasonable, Firefox has
// had a bug around this. Best to send nothing at all if
// config.NextProtos is empty. See
// c.config.NextProtos is empty. See
// https://golang.org/issue/5445.
if hs.clientHello.nextProtoNeg && len(config.NextProtos) > 0 {
if hs.clientHello.nextProtoNeg && len(c.config.NextProtos) > 0 {
hs.hello.nextProtoNeg = true
hs.hello.nextProtos = config.NextProtos
hs.hello.nextProtos = c.config.NextProtos
}
}

hs.cert, err = config.getCertificate(&ClientHelloInfo{
CipherSuites: hs.clientHello.cipherSuites,
ServerName: hs.clientHello.serverName,
SupportedCurves: hs.clientHello.supportedCurves,
SupportedPoints: hs.clientHello.supportedPoints,
})
hs.cert, err = c.config.getCertificate(clientHelloInfo)
if err != nil {
c.sendAlert(alertInternalError)
return false, err
Expand Down Expand Up @@ -354,18 +368,17 @@ func (hs *serverHandshakeState) doResumeHandshake() error {
}

func (hs *serverHandshakeState) doFullHandshake() error {
config := hs.c.config
c := hs.c

if hs.clientHello.ocspStapling && len(hs.cert.OCSPStaple) > 0 {
hs.hello.ocspStapling = true
}

hs.hello.ticketSupported = hs.clientHello.ticketSupported && !config.SessionTicketsDisabled
hs.hello.ticketSupported = hs.clientHello.ticketSupported && !c.config.SessionTicketsDisabled
hs.hello.cipherSuite = hs.suite.id

hs.finishedHash = newFinishedHash(hs.c.vers, hs.suite)
if config.ClientAuth == NoClientCert {
if c.config.ClientAuth == NoClientCert {
// No need to keep a full record of the handshake if client
// certificates won't be used.
hs.finishedHash.discardHandshakeBuffer()
Expand Down Expand Up @@ -394,7 +407,7 @@ func (hs *serverHandshakeState) doFullHandshake() error {
}

keyAgreement := hs.suite.ka(c.vers)
skx, err := keyAgreement.generateServerKeyExchange(config, hs.cert, hs.clientHello, hs.hello)
skx, err := keyAgreement.generateServerKeyExchange(c.config, hs.cert, hs.clientHello, hs.hello)
if err != nil {
c.sendAlert(alertHandshakeFailure)
return err
Expand All @@ -406,7 +419,7 @@ func (hs *serverHandshakeState) doFullHandshake() error {
}
}

if config.ClientAuth >= RequestClientCert {
if c.config.ClientAuth >= RequestClientCert {
// Request a client certificate
certReq := new(certificateRequestMsg)
certReq.certificateTypes = []byte{
Expand All @@ -423,8 +436,8 @@ func (hs *serverHandshakeState) doFullHandshake() error {
// to our request. When we know the CAs we trust, then
// we can send them down, so that the client can choose
// an appropriate certificate to give to us.
if config.ClientCAs != nil {
certReq.certificateAuthorities = config.ClientCAs.Subjects()
if c.config.ClientCAs != nil {
certReq.certificateAuthorities = c.config.ClientCAs.Subjects()
}
hs.finishedHash.Write(certReq.marshal())
if _, err := c.writeRecord(recordTypeHandshake, certReq.marshal()); err != nil {
Expand Down Expand Up @@ -452,7 +465,7 @@ func (hs *serverHandshakeState) doFullHandshake() error {
var ok bool
// If we requested a client certificate, then the client must send a
// certificate message, even if it's empty.
if config.ClientAuth >= RequestClientCert {
if c.config.ClientAuth >= RequestClientCert {
if certMsg, ok = msg.(*certificateMsg); !ok {
c.sendAlert(alertUnexpectedMessage)
return unexpectedMessageError(certMsg, msg)
Expand All @@ -461,7 +474,7 @@ func (hs *serverHandshakeState) doFullHandshake() error {

if len(certMsg.certificates) == 0 {
// The client didn't actually send a certificate
switch config.ClientAuth {
switch c.config.ClientAuth {
case RequireAnyClientCert, RequireAndVerifyClientCert:
c.sendAlert(alertBadCertificate)
return errors.New("tls: client didn't provide a certificate")
Expand All @@ -487,13 +500,13 @@ func (hs *serverHandshakeState) doFullHandshake() error {
}
hs.finishedHash.Write(ckx.marshal())

preMasterSecret, err := keyAgreement.processClientKeyExchange(config, hs.cert, ckx, c.vers)
preMasterSecret, err := keyAgreement.processClientKeyExchange(c.config, hs.cert, ckx, c.vers)
if err != nil {
c.sendAlert(alertHandshakeFailure)
return err
}
hs.masterSecret = masterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret, hs.clientHello.random, hs.hello.random)
if err := config.writeKeyLog(hs.clientHello.random, hs.masterSecret); err != nil {
if err := c.config.writeKeyLog(hs.clientHello.random, hs.masterSecret); err != nil {
c.sendAlert(alertInternalError)
return err
}
Expand Down
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