67 lines
1.5 KiB
Go
67 lines
1.5 KiB
Go
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package service
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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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)
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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 (s *Service) encrypt(text string) (string, error) {
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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(s.AESBlock, iv)
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cfb.XORKeyStream(cipherText[aes.BlockSize:], []byte(msg))
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finalMsg := base64.URLEncoding.EncodeToString(cipherText)
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return finalMsg, nil
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}
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func (s *Service) decrypt(text string) (string, error) {
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decodedMsg, err := base64.URLEncoding.DecodeString(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(s.AESBlock, 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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