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66 lines
1.5 KiB
66 lines
1.5 KiB
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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