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crypto/tls: Use a backing array for getSupportedVersions

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Avoid runtime heap memory allocation.

Fixes: ("crypto/tls: allow client to pick TLS 1.3, do not enable it by default.")
This commit is contained in:
Tom Thorogood 2017-10-02 18:34:42 +10:30 committed by Peter Wu
parent 1192d2574f
commit 710e9e9631
1 changed files with 16 additions and 11 deletions
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25
common.go
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@ -836,6 +836,15 @@ func (c *Config) pickVersion(peerSupportedVersions []uint16) (uint16, bool) {
return 0, false return 0, false
} }
// configSuppVersArray is the backing array of Config.getSupportedVersions
var configSuppVersArray = [...]uint16{VersionTLS13, VersionTLS12, VersionTLS11, VersionTLS10, VersionSSL30}
// tls13DraftSuppVersArray is the backing array of Config.getSupportedVersions
// with TLS 1.3 draft versions included.
//
// TODO: remove once TLS 1.3 is finalised.
var tls13DraftSuppVersArray = [...]uint16{VersionTLS13Draft18, VersionTLS12, VersionTLS11, VersionTLS10, VersionSSL30}
// getSupportedVersions returns the protocol versions that are supported by the // getSupportedVersions returns the protocol versions that are supported by the
// current configuration. // current configuration.
func (c *Config) getSupportedVersions() []uint16 { func (c *Config) getSupportedVersions() []uint16 {
@ -848,18 +857,14 @@ func (c *Config) getSupportedVersions() []uint16 {
if maxVersion > VersionTLS13 { if maxVersion > VersionTLS13 {
maxVersion = VersionTLS13 maxVersion = VersionTLS13
} }
if maxVersion < minVersion {
supportedVersions := []uint16{} return nil
// Prefer newer versions over older versions.
for v := maxVersion; v >= minVersion; v-- {
if v == VersionTLS13 {
// Advertise all supported draft versions.
supportedVersions = append(supportedVersions, VersionTLS13Draft18)
continue // final TLS 1.3 version is not supported yet.
} }
supportedVersions = append(supportedVersions, v) // TODO: remove once TLS 1.3 is finalised.
if maxVersion == VersionTLS13 {
return tls13DraftSuppVersArray[:len(tls13DraftSuppVersArray)-int(minVersion-VersionSSL30)]
} }
return supportedVersions return configSuppVersArray[VersionTLS13-maxVersion : VersionTLS13-minVersion+1]
} }
// getCertificate returns the best certificate for the given ClientHelloInfo, // getCertificate returns the best certificate for the given ClientHelloInfo,