Source File
	random.go

Belonging Package
	github.com/pion/dtls/v3/pkg/protocol/handshake

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

package handshake

import (
	"crypto/rand"
	"encoding/binary"
	"time"
)

// Consts for Random in Handshake.
const (
	RandomBytesLength = 28
	RandomLength      = RandomBytesLength + 4
)

// Random value that is used in ClientHello and ServerHello
//
// https://tools.ietf.org/html/rfc4346#section-7.4.1.2
type Random struct {
	GMTUnixTime time.Time
	RandomBytes [RandomBytesLength]byte
}

// MarshalFixed encodes the Handshake.
func (r *Random) MarshalFixed() [RandomLength]byte {
	var out [RandomLength]byte

	binary.BigEndian.PutUint32(out[0:], uint32(r.GMTUnixTime.Unix())) //nolint:gosec // G115
	copy(out[4:], r.RandomBytes[:])

	return out
}

// UnmarshalFixed populates the message from encoded data.
func (r *Random) UnmarshalFixed(data [RandomLength]byte) {
	r.GMTUnixTime = time.Unix(int64(binary.BigEndian.Uint32(data[0:])), 0)
	copy(r.RandomBytes[:], data[4:])
}

// Populate fills the handshakeRandom with random values
// may be called multiple times.
func (r *Random) Populate() error {
	r.GMTUnixTime = time.Now()

	tmp := make([]byte, RandomBytesLength)
	_, err := rand.Read(tmp)
	copy(r.RandomBytes[:], tmp)

	return err
}

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