68 lines
1.3 KiB
Go
68 lines
1.3 KiB
Go
package urlshortener
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import (
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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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"fmt"
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"io"
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)
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// this class works with AES. This solution without database.
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type LinkEncryption struct {
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Key string // this is secret key, must be 32-bit, if you want to use it
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}
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func (l *LinkEncryption) Shorten(plainText string) (string, error) {
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block, err := aes.NewCipher([]byte(l.Key))
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if err != nil {
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return "", err
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}
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gcm, err := cipher.NewGCM(block)
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if err != nil {
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return "", err
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}
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nonce := make([]byte, gcm.NonceSize())
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if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
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return "", err
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}
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cipherText := gcm.Seal(nonce, nonce, []byte(plainText), nil)
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return base64.URLEncoding.EncodeToString(cipherText), nil
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}
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func (l *LinkEncryption) Unshorten(encryptedText string) (string, error) {
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data, err := base64.URLEncoding.DecodeString(encryptedText)
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if err != nil {
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return "", err
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}
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block, err := aes.NewCipher([]byte(l.Key))
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if err != nil {
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return "", err
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}
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gcm, err := cipher.NewGCM(block)
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if err != nil {
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return "", err
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}
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nonceSize := gcm.NonceSize()
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if len(data) < nonceSize {
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return "", fmt.Errorf("ciphertext too short")
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}
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nonce, cipherText := data[:nonceSize], data[nonceSize:]
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plainText, err := gcm.Open(nil, nonce, cipherText, nil)
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if err != nil {
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return "", err
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}
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return string(plainText), nil
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}
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