46 lines
1.1 KiB
Go
46 lines
1.1 KiB
Go
package extension
|
|
|
|
import "encoding/binary"
|
|
|
|
const (
|
|
useExtendedMasterSecretHeaderSize = 4
|
|
)
|
|
|
|
// UseExtendedMasterSecret defines a TLS extension that contextually binds the
|
|
// master secret to a log of the full handshake that computes it, thus
|
|
// preventing MITM attacks.
|
|
type UseExtendedMasterSecret struct {
|
|
Supported bool
|
|
}
|
|
|
|
// TypeValue returns the extension TypeValue
|
|
func (u UseExtendedMasterSecret) TypeValue() TypeValue {
|
|
return UseExtendedMasterSecretTypeValue
|
|
}
|
|
|
|
// Marshal encodes the extension
|
|
func (u *UseExtendedMasterSecret) Marshal() ([]byte, error) {
|
|
if !u.Supported {
|
|
return []byte{}, nil
|
|
}
|
|
|
|
out := make([]byte, useExtendedMasterSecretHeaderSize)
|
|
|
|
binary.BigEndian.PutUint16(out, uint16(u.TypeValue()))
|
|
binary.BigEndian.PutUint16(out[2:], uint16(0)) // length
|
|
return out, nil
|
|
}
|
|
|
|
// Unmarshal populates the extension from encoded data
|
|
func (u *UseExtendedMasterSecret) Unmarshal(data []byte) error {
|
|
if len(data) < useExtendedMasterSecretHeaderSize {
|
|
return errBufferTooSmall
|
|
} else if TypeValue(binary.BigEndian.Uint16(data)) != u.TypeValue() {
|
|
return errInvalidExtensionType
|
|
}
|
|
|
|
u.Supported = true
|
|
|
|
return nil
|
|
}
|