package faketls

import (
	crand "crypto/rand"

	"golang.org/x/crypto/curve25519"
)

// GenX25519PublicKey returns a valid X25519 public key (32 bytes) for the ClientHello key_share extension.
// Some MTProxy builds validate the point; a random quadratic residue mod P (older telethon-faketls trick) is rejected.
func GenX25519PublicKey() ([]byte, error) {
	var priv, pub [32]byte
	if _, err := crand.Read(priv[:]); err != nil {
		return nil, err
	}
	curve25519.ScalarBaseMult(&pub, &priv)
	return pub[:], nil
}

// Rand32 returns 32 random bytes (session id).
func Rand32() ([]byte, error) {
	b := make([]byte, 32)
	if _, err := crand.Read(b); err != nil {
		return nil, err
	}
	return b, nil
}