116 lines
2.8 KiB
Go
116 lines
2.8 KiB
Go
package shadowstream
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import (
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"crypto/aes"
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"crypto/cipher"
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"crypto/md5"
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"crypto/rc4"
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"strconv"
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"golang.org/x/crypto/chacha20"
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)
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// Cipher generates a pair of stream ciphers for encryption and decryption.
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type Cipher interface {
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IVSize() int
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Encrypter(iv []byte) cipher.Stream
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Decrypter(iv []byte) cipher.Stream
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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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// CTR mode
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type ctrStream struct{ cipher.Block }
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func (b *ctrStream) IVSize() int { return b.BlockSize() }
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func (b *ctrStream) Decrypter(iv []byte) cipher.Stream { return b.Encrypter(iv) }
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func (b *ctrStream) Encrypter(iv []byte) cipher.Stream { return cipher.NewCTR(b, iv) }
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func AESCTR(key []byte) (Cipher, 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 &ctrStream{blk}, nil
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}
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// CFB mode
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type cfbStream struct{ cipher.Block }
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func (b *cfbStream) IVSize() int { return b.BlockSize() }
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func (b *cfbStream) Decrypter(iv []byte) cipher.Stream { return cipher.NewCFBDecrypter(b, iv) }
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func (b *cfbStream) Encrypter(iv []byte) cipher.Stream { return cipher.NewCFBEncrypter(b, iv) }
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func AESCFB(key []byte) (Cipher, 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 &cfbStream{blk}, nil
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}
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// IETF-variant of chacha20
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type chacha20ietfkey []byte
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func (k chacha20ietfkey) IVSize() int { return chacha20.NonceSize }
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func (k chacha20ietfkey) Decrypter(iv []byte) cipher.Stream { return k.Encrypter(iv) }
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func (k chacha20ietfkey) Encrypter(iv []byte) cipher.Stream {
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ciph, err := chacha20.NewUnauthenticatedCipher(k, iv)
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if err != nil {
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panic(err) // should never happen
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}
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return ciph
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}
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func Chacha20IETF(key []byte) (Cipher, error) {
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if len(key) != chacha20.KeySize {
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return nil, KeySizeError(chacha20.KeySize)
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}
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return chacha20ietfkey(key), nil
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}
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type xchacha20key []byte
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func (k xchacha20key) IVSize() int { return chacha20.NonceSizeX }
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func (k xchacha20key) Decrypter(iv []byte) cipher.Stream { return k.Encrypter(iv) }
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func (k xchacha20key) Encrypter(iv []byte) cipher.Stream {
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ciph, err := chacha20.NewUnauthenticatedCipher(k, iv)
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if err != nil {
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panic(err) // should never happen
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}
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return ciph
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}
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func Xchacha20(key []byte) (Cipher, error) {
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if len(key) != chacha20.KeySize {
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return nil, KeySizeError(chacha20.KeySize)
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}
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return xchacha20key(key), nil
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}
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type rc4Md5Key []byte
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func (k rc4Md5Key) IVSize() int {
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return 16
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}
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func (k rc4Md5Key) Encrypter(iv []byte) cipher.Stream {
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h := md5.New()
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h.Write([]byte(k))
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h.Write(iv)
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rc4key := h.Sum(nil)
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c, _ := rc4.NewCipher(rc4key)
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return c
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}
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func (k rc4Md5Key) Decrypter(iv []byte) cipher.Stream {
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return k.Encrypter(iv)
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}
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func RC4MD5(key []byte) (Cipher, error) {
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return rc4Md5Key(key), nil
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}
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