63 lines
1.7 KiB
Go
63 lines
1.7 KiB
Go
package extension
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import (
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"encoding/binary"
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"github.com/pion/dtls/v2/pkg/crypto/elliptic"
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)
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const (
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supportedGroupsHeaderSize = 6
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)
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// SupportedEllipticCurves allows a Client/Server to communicate
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// what curves they both support
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//
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// https://tools.ietf.org/html/rfc8422#section-5.1.1
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type SupportedEllipticCurves struct {
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EllipticCurves []elliptic.Curve
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}
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// TypeValue returns the extension TypeValue
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func (s SupportedEllipticCurves) TypeValue() TypeValue {
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return SupportedEllipticCurvesTypeValue
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}
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// Marshal encodes the extension
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func (s *SupportedEllipticCurves) Marshal() ([]byte, error) {
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out := make([]byte, supportedGroupsHeaderSize)
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binary.BigEndian.PutUint16(out, uint16(s.TypeValue()))
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binary.BigEndian.PutUint16(out[2:], uint16(2+(len(s.EllipticCurves)*2)))
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binary.BigEndian.PutUint16(out[4:], uint16(len(s.EllipticCurves)*2))
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for _, v := range s.EllipticCurves {
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out = append(out, []byte{0x00, 0x00}...)
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binary.BigEndian.PutUint16(out[len(out)-2:], uint16(v))
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}
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return out, nil
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}
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// Unmarshal populates the extension from encoded data
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func (s *SupportedEllipticCurves) Unmarshal(data []byte) error {
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if len(data) <= supportedGroupsHeaderSize {
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return errBufferTooSmall
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} else if TypeValue(binary.BigEndian.Uint16(data)) != s.TypeValue() {
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return errInvalidExtensionType
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}
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groupCount := int(binary.BigEndian.Uint16(data[4:]) / 2)
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if supportedGroupsHeaderSize+(groupCount*2) > len(data) {
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return errLengthMismatch
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}
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for i := 0; i < groupCount; i++ {
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supportedGroupID := elliptic.Curve(binary.BigEndian.Uint16(data[(supportedGroupsHeaderSize + (i * 2)):]))
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if _, ok := elliptic.Curves()[supportedGroupID]; ok {
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s.EllipticCurves = append(s.EllipticCurves, supportedGroupID)
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}
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}
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return nil
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}
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