ssh-

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package crypt
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import (
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	"bytes"
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	"crypto/aes"
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	"crypto/cipher"
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	"crypto/rand"
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	"encoding/base64"
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	"errors"
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	"io"
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	"strings"
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)
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func addBase64Padding(value string) string {
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	m := len(value) % 4
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	if m != 0 {
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		value += strings.Repeat("=", 4-m)
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	}
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	return value
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}
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func removeBase64Padding(value string) string {
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	return strings.Replace(value, "=", "", -1)
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}
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func Pad(src []byte) []byte {
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	padding := aes.BlockSize - len(src)%aes.BlockSize
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	padtext := bytes.Repeat([]byte{byte(padding)}, padding)
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	return append(src, padtext...)
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}
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func Unpad(src []byte) ([]byte, error) {
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	length := len(src)
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	unpadding := int(src[length-1])
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	if unpadding > length {
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		return nil, errors.New("unpad error. This could happen when incorrect encryption key is used")
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	}
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	return src[:(length - unpadding)], nil
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}
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func encrypt(key []byte, text string) (string, error) {
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	block, err := aes.NewCipher(key)
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	if err != nil {
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		return "", err
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	}
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	msg := Pad([]byte(text))
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	ciphertext := make([]byte, aes.BlockSize+len(msg))
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	iv := ciphertext[:aes.BlockSize]
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	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
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		return "", err
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	}
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	cfb := cipher.NewCFBEncrypter(block, iv)
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	cfb.XORKeyStream(ciphertext[aes.BlockSize:], []byte(msg))
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	finalMsg := removeBase64Padding(base64.URLEncoding.EncodeToString(ciphertext))
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	return finalMsg, nil
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}
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func decrypt(key []byte, text string) (string, error) {
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	block, err := aes.NewCipher(key)
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	if err != nil {
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		return "", err
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	}
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	decodedMsg, err := base64.URLEncoding.DecodeString(addBase64Padding(text))
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	if err != nil {
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		return "", err
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	}
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	if (len(decodedMsg) % aes.BlockSize) != 0 {
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		return "", errors.New("blocksize must be multipe of decoded message length")
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	}
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	iv := decodedMsg[:aes.BlockSize]
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	msg := decodedMsg[aes.BlockSize:]
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	cfb := cipher.NewCFBDecrypter(block, iv)
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	cfb.XORKeyStream(msg, msg)
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	unpadMsg, err := Unpad(msg)
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	if err != nil {
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		return "", err
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	}
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	return string(unpadMsg), nil
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}
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