91 lines
2.1 KiB
Go
91 lines
2.1 KiB
Go
package secretbox
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import (
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"crypto/rand"
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"errors"
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"fmt"
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"io"
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"golang.org/x/crypto/nacl/secretbox"
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)
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const keySize = 32 // secretbox allows only 32-byte keys
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var ErrShortCipherText = errors.New("ciphertext too short")
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var ErrNoEncryptionKey = errors.New("encryption key is required")
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var ErrInvalidKeySize = errors.New("invalid key size: must be 32 bytes")
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var ErrZeroKey = errors.New("encryption key cannot be all zeros")
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// GenerateKey generates a random 32-byte key to be used by EncryptWithKey and DecryptWithKey
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func GenerateKey() ([]byte, error) {
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key := make([]byte, keySize)
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if _, err := io.ReadFull(rand.Reader, key); err != nil {
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return nil, fmt.Errorf("failed to generate key: %w", err)
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}
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return key, nil
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}
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// EncryptWithKey encrypts data using NaCl's secretbox with the provided key.
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// 40 bytes of overhead (24-byte nonce + 16-byte MAC) are added to the plaintext size.
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func EncryptWithKey(data, key []byte) ([]byte, error) {
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if err := validateKey(key); err != nil {
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return nil, err
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}
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var secretKey [keySize]byte
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copy(secretKey[:], key)
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// Generate 24 bytes of random data as nonce
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var nonce [24]byte
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if _, err := io.ReadFull(rand.Reader, nonce[:]); err != nil {
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return nil, err
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}
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// Encrypt and authenticate data
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encrypted := secretbox.Seal(nonce[:], data, &nonce, &secretKey)
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return encrypted, nil
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}
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// DecryptStringWithKey decrypts data using secretbox with the provided key
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func DecryptStringWithKey(data, key []byte) ([]byte, error) {
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if err := validateKey(key); err != nil {
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return nil, err
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}
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if len(data) < 24 {
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return nil, ErrShortCipherText
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}
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var secretKey [keySize]byte
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copy(secretKey[:], key)
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var nonce [24]byte
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copy(nonce[:], data[:24])
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decrypted, ok := secretbox.Open(nil, data[24:], &nonce, &secretKey)
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if !ok {
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return nil, errors.New("decryption failed")
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}
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return decrypted, nil
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}
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func validateKey(key []byte) error {
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if key == nil {
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return ErrNoEncryptionKey
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}
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if len(key) != keySize {
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return ErrInvalidKeySize
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}
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// check if key is all zeros
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for _, b := range key {
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if b != 0 {
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return nil
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}
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}
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return ErrZeroKey
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}
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