chore(general): check bounds for memory allocation (#4995)

internal/crypto/aesgcm.go

@@ -40,6 +40,8 @@ func initCrypto(masterKey, salt []byte) (cipher.AEAD, []byte, error) {
 	return aead, authData, nil
 }
 
+var errPlaintextTooLarge = errors.New("plaintext data is too large to be encrypted")
+
 // EncryptAes256Gcm encrypts data with AES 256 GCM.
 func EncryptAes256Gcm(data, masterKey, salt []byte) ([]byte, error) {
 	aead, authData, err := initCrypto(masterKey, salt)
@@ -48,8 +50,14 @@ func EncryptAes256Gcm(data, masterKey, salt []byte) ([]byte, error) {
 	}
 
 	nonceLength := aead.NonceSize()
-	noncePlusContentLength := nonceLength + len(data)
-	cipherText := make([]byte, noncePlusContentLength+aead.Overhead())
+	noncePlusOverhead := nonceLength + aead.Overhead()
+
+	const maxInt = int(^uint(0) >> 1)
+	if len(data) > maxInt-noncePlusOverhead {
+		return nil, errPlaintextTooLarge
+	}
+
+	cipherText := make([]byte, len(data)+noncePlusOverhead)
 
 	// Store nonce at the beginning of ciphertext.
 	nonce := cipherText[0:nonceLength]
@@ -70,11 +78,12 @@ func DecryptAes256Gcm(data, masterKey, salt []byte) ([]byte, error) {
 		return nil, errors.Wrap(err, "cannot initialize cipher")
 	}
 
-	data = append([]byte(nil), data...)
 	if len(data) < aead.NonceSize() {
 		return nil, errors.New("invalid encrypted payload, too short")
 	}
 
+	data = append([]byte(nil), data...)
+
 	nonce := data[0:aead.NonceSize()]
 	payload := data[aead.NonceSize():]