Adjust encoding of Azure block IDs (#68980)

Today we represent block IDs sent to Azure using the URL-safe base-64
encoding. This makes sense: these IDs appear in URLs. It turns out that
Azure rejects this encoding for block IDs and instead demands that they
are represented using the regular, URL-unsafe, base-64 encoding instead,
then further wrapped in %-encoding to deal with the URL-unsafe
characters that inevitably result.

Relates #66489
Backport of #68957

plugins/repository-azure/src/main/java/org/elasticsearch/repositories/azure/AzureBlobStore.java

@@ -61,6 +61,7 @@
 import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Base64;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
@@ -448,11 +449,13 @@ private void executeMultipartUpload(String blobName, InputStream inputStream, lo
             assert blobSize == (((nbParts - 1) * partSize) + lastPartSize) : "blobSize does not match multipart sizes";
 
             final List<String> blockIds = new ArrayList<>(nbParts);
+            final Base64.Encoder base64Encoder = Base64.getEncoder().withoutPadding();
+            final Base64.Decoder base64UrlDecoder = Base64.getUrlDecoder();
             for (int i = 0; i < nbParts; i++) {
                 final long length = i < nbParts - 1 ? partSize : lastPartSize;
                 Flux<ByteBuffer> byteBufferFlux = convertStreamToByteBuffer(inputStream, length, DEFAULT_UPLOAD_BUFFERS_SIZE);
 
-                final String blockId = UUIDs.base64UUID();
+                final String blockId = base64Encoder.encodeToString(base64UrlDecoder.decode(UUIDs.base64UUID()));
                 blockBlobAsyncClient.stageBlock(blockId, byteBufferFlux, length).block();
                 blockIds.add(blockId);
             }

plugins/repository-azure/src/test/java/org/elasticsearch/repositories/azure/AzureBlobContainerRetriesTests.java

@@ -341,9 +341,11 @@ public void testWriteLargeBlob() throws Exception {
 
             if ("PUT".equals(exchange.getRequestMethod())) {
                 final Map<String, String> params = new HashMap<>();
-                RestUtils.decodeQueryString(exchange.getRequestURI().getQuery(), 0, params);
+                RestUtils.decodeQueryString(exchange.getRequestURI().getRawQuery(), 0, params);
 
                 final String blockId = params.get("blockid");
+                assert Strings.hasText(blockId) == false || AzureFixtureHelper.assertValidBlockId(blockId);
+
                 if (Strings.hasText(blockId) && (countDownUploads.decrementAndGet() % 2 == 0)) {
                     blocks.put(blockId, Streams.readFully(exchange.getRequestBody()));
                     exchange.sendResponseHeaders(RestStatus.CREATED.getStatus(), -1);

test/fixtures/azure-fixture/build.gradle

@@ -13,6 +13,7 @@ tasks.named("test").configure { enabled = false }
 
 dependencies {
   api project(':server')
+  api project(':test:framework')
 }
 
 tasks.named("preProcessFixture").configure {

test/fixtures/azure-fixture/src/main/java/fixture/azure/AzureHttpHandler.java

@@ -22,22 +22,20 @@
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.nio.charset.StandardCharsets;
-import java.time.ZoneOffset;
-import java.time.ZonedDateTime;
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
-import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
+import static org.elasticsearch.repositories.azure.AzureFixtureHelper.assertValidBlockId;
+
 /**
  * Minimal HTTP handler that acts as an Azure compliant server
  */
@@ -64,9 +62,10 @@ public void handle(final HttpExchange exchange) throws IOException {
             if (Regex.simpleMatch("PUT /" + account + "/" + container + "/*blockid=*", request)) {
                 // Put Block (https://docs.microsoft.com/en-us/rest/api/storageservices/put-block)
                 final Map<String, String> params = new HashMap<>();
-                RestUtils.decodeQueryString(exchange.getRequestURI().getQuery(), 0, params);
+                RestUtils.decodeQueryString(exchange.getRequestURI().getRawQuery(), 0, params);
 
                 final String blockId = params.get("blockid");
+                assert assertValidBlockId(blockId);
                 blobs.put(blockId, Streams.readFully(exchange.getRequestBody()));
                 exchange.sendResponseHeaders(RestStatus.CREATED.getStatus(), -1);
 

test/framework/src/main/java/org/elasticsearch/repositories/azure/AzureFixtureHelper.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.repositories.azure;
+
+import org.elasticsearch.common.Strings;
+
+import java.util.Base64;
+
+public class AzureFixtureHelper {
+    private AzureFixtureHelper() {
+    }
+
+    public static boolean assertValidBlockId(String blockId) {
+        assert Strings.hasText(blockId) : "blockId missing";
+        try {
+            final byte[] decode = Base64.getDecoder().decode(blockId);
+            // all block IDs for a blob must be the same length and <64 bytes prior to decoding.
+            // Elasticsearch generates them all to be 15 bytes long so we can just assert that:
+            assert decode.length == 15 : "blockid [" + blockId + "] decodes to [" + decode.length + "] bytes";
+        } catch (Exception e) {
+            assert false : new AssertionError("blockid [" + blockId + "] is not in base64", e);
+        }
+        return true;
+    }
+}