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crypto/tls: make 1.3 version negotiation more robust

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BoGo: IgnoreClientVersionOrder
BoGO: *VersionTolerance
BoGo: RejectFinalTLS13
This commit is contained in:
Filippo Valsorda 2017-01-16 12:29:54 +00:00 committed by Peter Wu
parent 58aab36b6e
commit 922b99e473
2 changed files with 35 additions and 9 deletions
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34
common.go
View File

@ -785,11 +785,16 @@ func (c *Config) curvePreferences() []CurveID {
}
// mutualVersion returns the protocol version to use given the advertised
// version of the peer.
// version of the peer using the legacy non-extension methods.
func (c *Config) mutualVersion(vers uint16) (uint16, bool) {
minVersion := c.minVersion()
maxVersion := c.maxVersion()
// Version 1.3 and higher are not negotiated via this mechanism.
if maxVersion > VersionTLS12 {
maxVersion = VersionTLS12
}
if vers < minVersion {
return 0, false
}
@ -799,6 +804,33 @@ func (c *Config) mutualVersion(vers uint16) (uint16, bool) {
return vers, true
}
// pickVersion returns the protocol version to use given the advertised
// versions of the peer using the Supported Versions extension.
func (c *Config) pickVersion(supportedVersions []uint16) (uint16, bool) {
minVersion := c.minVersion()
maxVersion := c.maxVersion()
if c == nil || c.MaxVersion == 0 {
maxVersion = VersionTLS13 // override the default if pickVersion is used
}
tls13Enabled := maxVersion >= VersionTLS13
if maxVersion > VersionTLS12 {
maxVersion = VersionTLS12
}
var vers uint16
for _, v := range supportedVersions {
if v >= minVersion && v <= maxVersion ||
(tls13Enabled && v == VersionTLS13Draft18) {
if v > vers {
vers = v
}
}
}
return vers, vers != 0
}
// getCertificate returns the best certificate for the given ClientHelloInfo,
// defaulting to the first element of c.Certificates.
func (c *Config) getCertificate(clientHello *ClientHelloInfo) (*Certificate, error) {

10
handshake_server.go
View File

@ -171,14 +171,8 @@ func (hs *serverHandshakeState) readClientHello() (isResume bool, err error) {
}
if hs.clientHello.supportedVersions != nil {
for _, v := range hs.clientHello.supportedVersions {
if (v >= c.config.minVersion() && v <= c.config.maxVersion()) ||
v == VersionTLS13Draft18 {
c.vers = v
break
}
}
if c.vers == 0 {
c.vers, ok = c.config.pickVersion(hs.clientHello.supportedVersions)
if !ok {
c.sendAlert(alertProtocolVersion)
return false, fmt.Errorf("tls: none of the client versions (%x) are supported", hs.clientHello.supportedVersions)
}