mirror of
https://github.com/fumiama/WireGold.git
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107 lines
2.7 KiB
Go
107 lines
2.7 KiB
Go
package algo
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import (
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"crypto/cipher"
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"crypto/rand"
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"encoding/binary"
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"errors"
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)
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var (
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ErrCipherTextTooShort = errors.New("ciphertext too short")
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)
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func EncodeAEAD(aead cipher.AEAD, additional uint16, b []byte) []byte {
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nsz := aead.NonceSize()
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// Accocate capacity for all the stuffs.
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buf := make([]byte, 2+nsz+len(b)+aead.Overhead())
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n := 0
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binary.LittleEndian.PutUint16(buf[:2], additional)
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nonce := buf[2 : 2+nsz]
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// Select a random nonce
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_, err := rand.Read(nonce)
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if err != nil {
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panic(err)
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}
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// Encrypt the message and append the ciphertext to the nonce.
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eb := aead.Seal(nonce[nsz:nsz], nonce, b, buf[:2])
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n = len(eb)
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return buf[2 : 2+nsz+n]
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}
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func DecodeAEAD(aead cipher.AEAD, additional uint16, b []byte) (data []byte, err error) {
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nsz := aead.NonceSize()
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if len(b) < nsz {
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return nil, ErrCipherTextTooShort
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}
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// Split nonce and ciphertext.
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nonce, ciphertext := b[:nsz], b[nsz:]
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if len(ciphertext) == 0 {
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return nil, nil
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}
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// Decrypt the message and check it wasn't tampered with.
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var buf [2]byte
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binary.LittleEndian.PutUint16(buf[:], additional)
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data = make([]byte, len(ciphertext))
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n := 0
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d, err := aead.Open(data[:0], nonce, ciphertext, buf[:])
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n = len(d)
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if err != nil {
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return
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}
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return data[:n], nil
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}
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func EncodeXORLen(datalen int) int {
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batchsz := datalen / 8
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return 8 + batchsz*8 + 8 // seqrand dat tail
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}
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// EncodeXOR 按 8 字节, 以初始 mask 循环异或编码 data
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func EncodeXOR(data []byte, mask uint64, seq uint32) []byte {
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batchsz := len(data) / 8
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remain := len(data) % 8
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sum := mask
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buf := make([]byte, EncodeXORLen(len(data)))
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binary.LittleEndian.PutUint32(buf[:4], seq)
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_, _ = rand.Read(buf[4:8]) // seqrand
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sum ^= binary.LittleEndian.Uint64(buf[:8]) // init from seqrand
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binary.LittleEndian.PutUint64(buf[:8], sum)
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for i := 0; i < batchsz; i++ { // range on batch data
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a := i * 8
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b := (i + 1) * 8
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sum ^= binary.LittleEndian.Uint64(data[a:b])
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binary.LittleEndian.PutUint64(buf[a+8:b+8], sum)
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}
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p := batchsz * 8
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copy(buf[8+p:], data[p:])
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buf[len(buf)-1] = byte(remain)
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sum ^= binary.LittleEndian.Uint64(buf[8+p:])
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binary.LittleEndian.PutUint64(buf[8+p:], sum)
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return buf
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}
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// DecodeXOR 按 8 字节, 以初始 mask 循环异或解码 data,
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// 解码结果完全覆盖 data.
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func DecodeXOR(data []byte, mask uint64) (uint32, []byte) {
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if len(data) < 16 || len(data)%8 != 0 {
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return 0, nil
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}
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batchsz := len(data) / 8
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sum := mask
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for i := 0; i < batchsz; i++ {
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a := i * 8
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b := (i + 1) * 8
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x := binary.LittleEndian.Uint64(data[a:b])
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sum ^= x
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binary.LittleEndian.PutUint64(data[a:b], sum)
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sum = x
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}
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remain := data[len(data)-1]
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if remain >= 8 {
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return 0, nil
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}
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return binary.LittleEndian.Uint32(data[:4]),
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data[8 : len(data)-8+int(remain)]
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}
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