[GitHub] [spark] cloud-fan commented on a diff in pull request #40704: [SPARK-43038][SQL] Support the CBC mode by `aes_encrypt()`/`aes_decrypt()`

["cloud-fan (via GitHub)" <gi...@apache.org>]

cloud-fan commented on code in PR #40704:
URL: https://github.com/apache/spark/pull/40704#discussion_r1163568739


##########
sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/ExpressionImplUtils.java:
##########
@@ -115,11 +128,74 @@ private static byte[] aesInternal(
           cipher.init(Cipher.DECRYPT_MODE, secretKey, parameterSpec);
           return cipher.doFinal(input, GCM_IV_LEN, input.length - GCM_IV_LEN);
         }
+      } else if (mode.equalsIgnoreCase("CBC") &&
+          (padding.equalsIgnoreCase("PKCS") || padding.equalsIgnoreCase("DEFAULT"))) {
+        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
+        if (opmode == Cipher.ENCRYPT_MODE) {
+          byte[] salt = new byte[CBC_SALT_LEN];
+          secureRandom.nextBytes(salt);
+          final byte[] keyAndIv = getKeyAndIv(key, salt);
+          final byte[] keyValue = Arrays.copyOfRange(keyAndIv, 0, key.length);
+          final byte[] iv = Arrays.copyOfRange(keyAndIv, key.length, key.length + CBC_IV_LEN);
+          cipher.init(
+            Cipher.ENCRYPT_MODE,
+            new SecretKeySpec(keyValue, "AES"),
+            new IvParameterSpec(iv));
+          byte[] encrypted = cipher.doFinal(input, 0, input.length);
+          ByteBuffer byteBuffer = ByteBuffer.allocate(
+            SALTED_MAGIC.length + CBC_SALT_LEN + encrypted.length);
+          byteBuffer.put(SALTED_MAGIC);
+          byteBuffer.put(salt);
+          byteBuffer.put(encrypted);
+          return byteBuffer.array();
+        } else {
+          assert(opmode == Cipher.DECRYPT_MODE);
+          final byte[] shouldBeMagic = Arrays.copyOfRange(input, 0, SALTED_MAGIC.length);
+          if (!Arrays.equals(shouldBeMagic, SALTED_MAGIC)) {
+            throw QueryExecutionErrors.aesInvalidSalt(shouldBeMagic);
+          }
+          final byte[] salt = Arrays.copyOfRange(
+            input, SALTED_MAGIC.length, SALTED_MAGIC.length + CBC_SALT_LEN);
+          final byte[] keyAndIv = getKeyAndIv(key, salt);
+          final byte[] keyValue = Arrays.copyOfRange(keyAndIv, 0, key.length);
+          final byte[] iv = Arrays.copyOfRange(keyAndIv, key.length, key.length + CBC_IV_LEN);
+          cipher.init(
+            Cipher.DECRYPT_MODE,
+            new SecretKeySpec(keyValue, "AES"),
+            new IvParameterSpec(iv, 0, CBC_IV_LEN));
+          return cipher.doFinal(input, CBC_IV_LEN, input.length - CBC_IV_LEN);
+        }
       } else {
         throw QueryExecutionErrors.aesModeUnsupportedError(mode, padding);
       }
     } catch (GeneralSecurityException e) {
       throw QueryExecutionErrors.aesCryptoError(e.getMessage());
     }
   }
+
+  // Derive the key and init vector in the same way as OpenSSL's EVP_BytesToKey
+  // since the version 1.1.0c which switched to SHA-256 as the hash.
+  private static byte[] getKeyAndIv(byte[] key, byte[] salt) {
+    final byte[] keyAndSalt = arrConcat(key, salt);
+    byte[] hash = new byte[0];
+    byte[] keyAndIv = new byte[0];
+    for (int i = 0; i < 3 && keyAndIv.length < key.length + CBC_IV_LEN; i++) {
+      final byte[] hashData = arrConcat(hash, keyAndSalt);
+      try {
+        final MessageDigest md = MessageDigest.getInstance("SHA-256");
+        hash = md.digest(hashData);
+        keyAndIv = arrConcat(keyAndIv, hash);
+      } catch (NoSuchAlgorithmException e) {
+        // Double-check the used algorithm in the message digest.

Review Comment:
   if we swallow the error, does it mean this method can return an empty array?



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