133 lines
3.1 KiB
Go
133 lines
3.1 KiB
Go
package crypto
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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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"errors"
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"fmt"
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"io"
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)
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// KeySize represents valid AES key sizes
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type KeySize int
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const (
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KeySize128 KeySize = 16 // AES-128
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KeySize192 KeySize = 24 // AES-192
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KeySize256 KeySize = 32 // AES-256 (recommended)
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)
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// IsValid returns true if the key size is valid for AES
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func (ks KeySize) IsValid() bool {
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switch ks {
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case KeySize128, KeySize192, KeySize256:
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return true
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default:
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return false
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}
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}
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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 16, 24, or 32 bytes")
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var ErrZeroKey = errors.New("encryption key cannot be all zeros")
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// GenerateKey generates a random AES key of default size KeySize256 (32 bytes).
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// Returns an error if the specified size is invalid or if key generation fails.
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func GenerateKey() ([]byte, error) {
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return GenerateKeyWithSize(KeySize256)
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}
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// GenerateKeyWithSize generates a random AES key of the specified size.
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// Returns an error if the specified size is invalid or if key generation fails.
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func GenerateKeyWithSize(size KeySize) ([]byte, error) {
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if !size.IsValid() {
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return nil, ErrInvalidKeySize
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}
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key := make([]byte, size)
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if _, err := io.ReadFull(rand.Reader, key); err != nil {
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return nil, fmt.Errorf("failed to generate AES key: %w", err)
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}
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return key, nil
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}
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// EncryptWithAESKey encrypts data using AES-GCM with the provided key.
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// The key must be 16, 24, or 32 bytes long (for AES-128, AES-192, or AES-256).
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// Returns the encrypted data with the nonce prepended, or an error if encryption fails.
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func EncryptWithAESKey(data, key []byte) ([]byte, error) {
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if err := validateAESKey(key); err != nil {
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return nil, err
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}
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, 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 nil, 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 nil, err
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}
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return gcm.Seal(nonce, nonce, data, nil), nil
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}
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// DecryptStringWithAESKey decrypts data that was encrypted with EncryptWithAESKey.
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// The key must match the one used for encryption.
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// Expects the input to have a prepended nonce.
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// Returns the decrypted data or an error if decryption fails.
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func DecryptStringWithAESKey(data, key []byte) ([]byte, error) {
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if err := validateAESKey(key); err != nil {
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return nil, err
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}
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, 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 nil, err
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}
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if len(data) < gcm.NonceSize() {
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return nil, ErrShortCipherText
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}
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nonce, ciphertext := data[:gcm.NonceSize()], data[gcm.NonceSize():]
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decrypted, err := gcm.Open(nil, nonce, ciphertext, nil)
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if err != nil {
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return nil, err
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}
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return decrypted, nil
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}
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func validateAESKey(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 !KeySize(len(key)).IsValid() {
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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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