Migrate tests away from S3 SDK MD5DigestCalculatingInputStream (elastic#126099)

`S3BlobContainerRetriesTests` uses `MD5DigestCalculatingInputStream`
from the AWS v1 SDK to compute a MD5 checksum, but this feature is not
available in the v2 SDK. With this commit we remove this dependency and
compute the MD5 checksums directly instead.

Author: DaveCTurner

modules/repository-s3/src/test/java/org/elasticsearch/repositories/s3/S3BlobContainerRetriesTests.java

@@ -14,9 +14,7 @@
 import com.amazonaws.DnsResolver;
 import com.amazonaws.SdkClientException;
 import com.amazonaws.services.s3.AmazonS3ClientBuilder;
-import com.amazonaws.services.s3.internal.MD5DigestCalculatingInputStream;
 import com.amazonaws.services.s3.model.AmazonS3Exception;
-import com.amazonaws.util.Base16;
 import com.sun.net.httpserver.HttpExchange;
 import com.sun.net.httpserver.HttpHandler;
 
@@ -30,7 +28,9 @@
 import org.elasticsearch.common.blobstore.BlobPath;
 import org.elasticsearch.common.blobstore.OperationPurpose;
 import org.elasticsearch.common.blobstore.OptionalBytesReference;
+import org.elasticsearch.common.bytes.BytesArray;
 import org.elasticsearch.common.bytes.BytesReference;
+import org.elasticsearch.common.hash.MessageDigests;
 import org.elasticsearch.common.io.Streams;
 import org.elasticsearch.common.lucene.store.ByteArrayIndexInput;
 import org.elasticsearch.common.lucene.store.InputStreamIndexInput;
@@ -377,13 +377,12 @@ public void testWriteLargeBlob() throws Exception {
                 }
             } else if (s3Request.isUploadPartRequest()) {
                 // upload part request
-                MD5DigestCalculatingInputStream md5 = new MD5DigestCalculatingInputStream(exchange.getRequestBody());
-                BytesReference bytes = Streams.readFully(md5);
+                BytesReference bytes = Streams.readFully(exchange.getRequestBody());
                 assertThat((long) bytes.length(), anyOf(equalTo(lastPartSize), equalTo(bufferSize.getBytes())));
                 assertThat(contentLength, anyOf(equalTo(lastPartSize), equalTo(bufferSize.getBytes())));
 
                 if (countDownUploads.decrementAndGet() % 2 == 0) {
-                    exchange.getResponseHeaders().add("ETag", Base16.encodeAsString(md5.getMd5Digest()));
+                    exchange.getResponseHeaders().add("ETag", getBase16MD5Digest(bytes));
                     exchange.sendResponseHeaders(HttpStatus.SC_OK, -1);
                     exchange.close();
                     return;
@@ -475,12 +474,11 @@ public void testWriteLargeBlobStreaming() throws Exception {
                 }
             } else if (s3Request.isUploadPartRequest()) {
                 // upload part request
-                MD5DigestCalculatingInputStream md5 = new MD5DigestCalculatingInputStream(exchange.getRequestBody());
-                BytesReference bytes = Streams.readFully(md5);
+                BytesReference bytes = Streams.readFully(exchange.getRequestBody());
 
                 if (counterUploads.incrementAndGet() % 2 == 0) {
                     bytesReceived.addAndGet(bytes.length());
-                    exchange.getResponseHeaders().add("ETag", Base16.encodeAsString(md5.getMd5Digest()));
+                    exchange.getResponseHeaders().add("ETag", getBase16MD5Digest(bytes));
                     exchange.sendResponseHeaders(HttpStatus.SC_OK, -1);
                     exchange.close();
                     return;
@@ -1105,6 +1103,21 @@ public void testTrimmedLogAndCappedSuppressedErrorOnMultiObjectDeletionException
         }
     }
 
+    private static String getBase16MD5Digest(BytesReference bytesReference) {
+        return MessageDigests.toHexString(MessageDigests.digest(bytesReference, MessageDigests.md5()));
+    }
+
+    public void testGetBase16MD5Digest() {
+        // from Wikipedia, see also org.elasticsearch.common.hash.MessageDigestsTests.testMd5
+        assertBase16MD5Digest("", "d41d8cd98f00b204e9800998ecf8427e");
+        assertBase16MD5Digest("The quick brown fox jumps over the lazy dog", "9e107d9d372bb6826bd81d3542a419d6");
+        assertBase16MD5Digest("The quick brown fox jumps over the lazy dog.", "e4d909c290d0fb1ca068ffaddf22cbd0");
+    }
+
+    private static void assertBase16MD5Digest(String input, String expectedDigestString) {
+        assertEquals(expectedDigestString, getBase16MD5Digest(new BytesArray(input)));
+    }
+
     @Override
     protected Matcher<Integer> getMaxRetriesMatcher(int maxRetries) {
         // some attempts make meaningful progress and do not count towards the max retry limit