mirror of
https://github.com/MetaCubeX/mihomo.git
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94 lines
2.3 KiB
Go
94 lines
2.3 KiB
Go
package shadowaead
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import (
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"crypto/aes"
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"crypto/cipher"
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"crypto/sha1"
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"io"
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"strconv"
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"golang.org/x/crypto/chacha20poly1305"
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"golang.org/x/crypto/hkdf"
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)
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type Cipher interface {
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KeySize() int
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SaltSize() int
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Encrypter(salt []byte) (cipher.AEAD, error)
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Decrypter(salt []byte) (cipher.AEAD, error)
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}
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type KeySizeError int
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func (e KeySizeError) Error() string {
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return "key size error: need " + strconv.Itoa(int(e)) + " bytes"
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}
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func hkdfSHA1(secret, salt, info, outkey []byte) {
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r := hkdf.New(sha1.New, secret, salt, info)
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if _, err := io.ReadFull(r, outkey); err != nil {
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panic(err) // should never happen
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}
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}
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type metaCipher struct {
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psk []byte
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makeAEAD func(key []byte) (cipher.AEAD, error)
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}
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func (a *metaCipher) KeySize() int { return len(a.psk) }
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func (a *metaCipher) SaltSize() int {
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if ks := a.KeySize(); ks > 16 {
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return ks
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}
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return 16
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}
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func (a *metaCipher) Encrypter(salt []byte) (cipher.AEAD, error) {
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subkey := make([]byte, a.KeySize())
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hkdfSHA1(a.psk, salt, []byte("ss-subkey"), subkey)
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return a.makeAEAD(subkey)
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}
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func (a *metaCipher) Decrypter(salt []byte) (cipher.AEAD, error) {
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subkey := make([]byte, a.KeySize())
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hkdfSHA1(a.psk, salt, []byte("ss-subkey"), subkey)
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return a.makeAEAD(subkey)
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}
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func aesGCM(key []byte) (cipher.AEAD, error) {
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blk, err := aes.NewCipher(key)
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if err != nil {
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return nil, err
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}
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return cipher.NewGCM(blk)
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}
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// AESGCM creates a new Cipher with a pre-shared key. len(psk) must be
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// one of 16, 24, or 32 to select AES-128/196/256-GCM.
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func AESGCM(psk []byte) (Cipher, error) {
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switch l := len(psk); l {
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case 16, 24, 32: // AES 128/196/256
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default:
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return nil, aes.KeySizeError(l)
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}
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return &metaCipher{psk: psk, makeAEAD: aesGCM}, nil
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}
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// Chacha20Poly1305 creates a new Cipher with a pre-shared key. len(psk)
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// must be 32.
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func Chacha20Poly1305(psk []byte) (Cipher, error) {
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if len(psk) != chacha20poly1305.KeySize {
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return nil, KeySizeError(chacha20poly1305.KeySize)
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}
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return &metaCipher{psk: psk, makeAEAD: chacha20poly1305.New}, nil
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}
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// XChacha20Poly1305 creates a new Cipher with a pre-shared key. len(psk)
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// must be 32.
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func XChacha20Poly1305(psk []byte) (Cipher, error) {
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if len(psk) != chacha20poly1305.KeySize {
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return nil, KeySizeError(chacha20poly1305.KeySize)
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}
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return &metaCipher{psk: psk, makeAEAD: chacha20poly1305.NewX}, nil
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}
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