fix: add Content-MD5 header for Object Lock compliance

app/server/appsmith-plugins/amazons3Plugin/src/main/java/com/external/plugins/AmazonS3Plugin.java

@@ -58,6 +58,8 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.URL;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
 import java.util.ArrayList;
@@ -1167,10 +1169,29 @@ void uploadFileInS3(
             TransferManager transferManager =
                     TransferManagerBuilder.standard().withS3Client(connection).build();
             final ObjectMetadata objectMetadata = new ObjectMetadata();
+
+            // Set content length
+            objectMetadata.setContentLength(payload.length);
+
             // Only add content type if the user has mentioned it in the body
             if (multipartFormDataDTO.getType() != null) {
                 objectMetadata.setContentType(multipartFormDataDTO.getType());
             }
+
+            // Calculate and set Content-MD5 header for Object Lock compliance
+            try {
+                MessageDigest md5Digest = MessageDigest.getInstance("MD5");
+                byte[] md5Hash = md5Digest.digest(payload);
+                String md5Base64 = Base64.getEncoder().encodeToString(md5Hash);
+                objectMetadata.setContentMD5(md5Base64);
+                log.debug("Set Content-MD5 header for S3 upload: {}", md5Base64);
+            } catch (NoSuchAlgorithmException e) {
+                log.warn(
+                        "Failed to calculate MD5 checksum for S3 upload. Object Lock enabled buckets may reject this upload.",
+                        e);
+                // Continue with upload without MD5 header - let AWS handle the error if Object Lock is enabled
+            }
+
             transferManager
                     .upload(bucketName, path, inputStream, objectMetadata)
                     .waitForUploadResult();

app/server/appsmith-plugins/amazons3Plugin/src/test/java/com/external/plugins/AmazonS3PluginTest.java

@@ -45,6 +45,8 @@
 import java.lang.reflect.Method;
 import java.net.MalformedURLException;
 import java.net.URL;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
@@ -1584,4 +1586,47 @@ public void verify_sanitizeGenerateCRUDPageTemplateInfo_addsInfoToReplaceTemplat
                 .block();
         assertEquals(userSelectedBucketName, mappedColumnsAndTableName.get("templateBucket"));
     }
+
+    @Test
+    public void testContentMD5CalculationForObjectLock() throws NoSuchAlgorithmException {
+        // Test that MD5 calculation works correctly for Object Lock compliance
+        String testContent = "Hello, World!";
+        byte[] payload = testContent.getBytes();
+
+        // Calculate MD5 hash using the same logic as in uploadFileInS3
+        MessageDigest md5Digest = MessageDigest.getInstance("MD5");
+        byte[] md5Hash = md5Digest.digest(payload);
+        String md5Base64 = java.util.Base64.getEncoder().encodeToString(md5Hash);
+
+        // Verify MD5 calculation is correct
+        assertNotNull(md5Base64);
+        assertTrue(md5Base64.length() > 0);
+
+        // For "Hello, World!" the MD5 hash should be deterministic
+        // Expected MD5 for "Hello, World!" is 65a8e27d8879283831b664bd8b7f0ad4
+        String expectedMd5Hex = "65a8e27d8879283831b664bd8b7f0ad4";
+        String actualMd5Hex = bytesToHex(md5Hash);
+        assertEquals(expectedMd5Hex, actualMd5Hex);
+
+        // Verify base64 encoding
+        String expectedBase64 = java.util.Base64.getEncoder().encodeToString(hexToBytes(expectedMd5Hex));
+        assertEquals(expectedBase64, md5Base64);
+    }
+
+    private String bytesToHex(byte[] bytes) {
+        StringBuilder result = new StringBuilder();
+        for (byte b : bytes) {
+            result.append(String.format("%02x", b));
+        }
+        return result.toString();
+    }
+
+    private byte[] hexToBytes(String hex) {
+        int len = hex.length();
+        byte[] data = new byte[len / 2];
+        for (int i = 0; i < len; i += 2) {
+            data[i / 2] = (byte) ((Character.digit(hex.charAt(i), 16) << 4) + Character.digit(hex.charAt(i + 1), 16));
+        }
+        return data;
+    }
 }