func PickCipher(name string, key []byte, password string) (Cipher, error) {
	name = strings.ToUpper(name)
	switch name {
	case "DUMMY":
		return &dummy{}, nil
	case "CHACHA20-IETF-POLY1305":
		name = aeadChacha20Poly1305
	case "AES-128-GCM":
		name = aeadAes128Gcm
	case "AES-192-GCM":
		name = aeadAes192Gcm
	case "AES-256-GCM":
		name = aeadAes256Gcm
	}
	if choice, ok := aeadList[name]; ok {
		if len(key) == 0 {
			key = kdf(password, choice.KeySize)
		}
		if len(key) != choice.KeySize {
			return nil, shadowaead.KeySizeError(choice.KeySize)
		}
		aead, err := choice.New(key)
		return &aeadCipher{aead}, err
	}
	if choice, ok := streamList[name]; ok {
		if len(key) == 0 {
			key = kdf(password, choice.KeySize)
		}
		if len(key) != choice.KeySize {
			return nil, shadowstream.KeySizeError(choice.KeySize)
		}
		ciph, err := choice.New(key)
		return &streamCipher{ciph}, err
	}
	return nil, ErrCipherNotSupported
}
PickCipher returns a Cipher of the given name. Derive key from password if given key is empty.
package core
import (
	"crypto/md5"
	"errors"
	"net"
	"sort"
	"strings"
	"github.com/ihciah/go-shadowsocks-magic/shadowaead"
	"github.com/ihciah/go-shadowsocks-magic/shadowstream"
)
type Cipher interface {
	StreamConnCipher
	PacketConnCipher
}
type StreamConnCipher interface {
	StreamConn(net.Conn) net.Conn
}
type PacketConnCipher interface {
	PacketConn(net.PacketConn) net.PacketConn
}
var ErrCipherNotSupported = errors.New("cipher not supported")
const (
	aeadAes128Gcm        = "AEAD_AES_128_GCM"
	aeadAes192Gcm        = "AEAD_AES_192_GCM"
	aeadAes256Gcm        = "AEAD_AES_256_GCM"
	aeadChacha20Poly1305 = "AEAD_CHACHA20_POLY1305"
)
var aeadList = map[string]struct {
	KeySize int
	New     func([]byte) (shadowaead.Cipher, error)
}{
	aeadAes128Gcm:        {16, shadowaead.AESGCM},
	aeadAes192Gcm:        {24, shadowaead.AESGCM},
	aeadAes256Gcm:        {32, shadowaead.AESGCM},
	aeadChacha20Poly1305: {32, shadowaead.Chacha20Poly1305},
}
var streamList = map[string]struct {
	KeySize int
	New     func(key []byte) (shadowstream.Cipher, error)
}{
	"AES-128-CTR":   {16, shadowstream.AESCTR},
	"AES-192-CTR":   {24, shadowstream.AESCTR},
	"AES-256-CTR":   {32, shadowstream.AESCTR},
	"AES-128-CFB":   {16, shadowstream.AESCFB},
	"AES-192-CFB":   {24, shadowstream.AESCFB},
	"AES-256-CFB":   {32, shadowstream.AESCFB},
	"CHACHA20-IETF": {32, shadowstream.Chacha20IETF},
	"RC4-MD5":       {16, shadowstream.RC4MD5},
	"XCHACHA20":     {32, shadowstream.Xchacha20},
}
func ListCipher() []string {
	var l []string
	for k := range aeadList {
		l = append(l, k)
	}
	for k := range streamList {
		l = append(l, k)
	}
	sort.Strings(l)
	return l
}