psiphon-tunnel-core/replace/dtls/pkg/protocol/change_cipher_spec.go

// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
// SPDX-License-Identifier: MIT

package protocol

// ChangeCipherSpec protocol exists to signal transitions in
// ciphering strategies.  The protocol consists of a single message,
// which is encrypted and compressed under the current (not the pending)
// connection state.  The message consists of a single byte of value 1.
// https://tools.ietf.org/html/rfc5246#section-7.1
type ChangeCipherSpec struct{}

// ContentType returns the ContentType of this content
func (c ChangeCipherSpec) ContentType() ContentType {
	return ContentTypeChangeCipherSpec
}

// Marshal encodes the ChangeCipherSpec to binary
func (c *ChangeCipherSpec) Marshal() ([]byte, error) {
	return []byte{0x01}, nil
}

// Unmarshal populates the ChangeCipherSpec from binary
func (c *ChangeCipherSpec) Unmarshal(data []byte) error {
	if len(data) == 1 && data[0] == 0x01 {
		return nil
	}

	return errInvalidCipherSpec
}