feat(dynamodb): imported tables always grant permissions for indexes (#20682)

When we use imported tables, grant methods don't grant permissions for indexes unless local indexes or global secondary indexes are specified. The information for indexes is used only for grant permissions now. Users either keep track of index information of the imported tables or specify random index (e.g. `*`) as a workaround to obtain the permissions. This PR let imported tables grant permissions for indexes without providing indexes.

close #13703 

----

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### Adding new Unconventional Dependencies:

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: i05nagai

packages/@aws-cdk/aws-dynamodb/README.md

@@ -36,6 +36,8 @@ If you intend to use the `tableStreamArn` (including indirectly, for example by
 `@aws-cdk/aws-lambda-event-source.DynamoEventSource` on the imported table), you *must* use the
 `Table.fromTableAttributes` method and the `tableStreamArn` property *must* be populated.
 
+In order to grant permissions to indexes on imported tables you can either set `grantIndexPermissions` to `true`, or you can provide the indexes via the `globalIndexes` or `localIndexes` properties. This will enable `grant*` methods to also grant permissions to *all* table indexes.
+
 ## Keys
 
 When a table is defined, you must define it's schema using the `partitionKey`

packages/@aws-cdk/aws-dynamodb/lib/table.ts

@@ -599,6 +599,15 @@ export interface TableAttributes {
    * @default - no local indexes
    */
   readonly localIndexes?: string[];
+
+  /**
+   * If set to true, grant methods always grant permissions for all indexes.
+   * If false is provided, grant methods grant the permissions
+   * only when {@link globalIndexes} or {@link localIndexes} is specified.
+   *
+   * @default - false
+   */
+  readonly grantIndexPermissions?: boolean;
 }
 
 abstract class TableBase extends Resource implements ITable {
@@ -1078,7 +1087,8 @@ export class Table extends TableBase {
       public readonly tableArn: string;
       public readonly tableStreamArn?: string;
       public readonly encryptionKey?: kms.IKey;
-      protected readonly hasIndex = (attrs.globalIndexes ?? []).length > 0 ||
+      protected readonly hasIndex = (attrs.grantIndexPermissions ?? false) ||
+        (attrs.globalIndexes ?? []).length > 0 ||
         (attrs.localIndexes ?? []).length > 0;
 
       constructor(_tableArn: string, tableName: string, tableStreamArn?: string) {

packages/@aws-cdk/aws-dynamodb/test/dynamodb.test.ts

@@ -2508,6 +2508,64 @@ describe('import', () => {
         },
       });
     });
+
+    test('creates the index permissions if grantIndexPermissions is provided', () => {
+      const stack = new Stack();
+
+      const table = Table.fromTableAttributes(stack, 'ImportedTable', {
+        tableName: 'MyTableName',
+        grantIndexPermissions: true,
+      });
+
+      const role = new iam.Role(stack, 'Role', {
+        assumedBy: new iam.AnyPrincipal(),
+      });
+
+      table.grantReadData(role);
+
+      Template.fromStack(stack).hasResourceProperties('AWS::IAM::Policy', {
+        PolicyDocument: {
+          Statement: [
+            {
+              Action: [
+                'dynamodb:BatchGetItem',
+                'dynamodb:GetRecords',
+                'dynamodb:GetShardIterator',
+                'dynamodb:Query',
+                'dynamodb:GetItem',
+                'dynamodb:Scan',
+                'dynamodb:ConditionCheckItem',
+                'dynamodb:DescribeTable',
+              ],
+              Resource: [
+                {
+                  'Fn::Join': ['', [
+                    'arn:',
+                    { Ref: 'AWS::Partition' },
+                    ':dynamodb:',
+                    { Ref: 'AWS::Region' },
+                    ':',
+                    { Ref: 'AWS::AccountId' },
+                    ':table/MyTableName',
+                  ]],
+                },
+                {
+                  'Fn::Join': ['', [
+                    'arn:',
+                    { Ref: 'AWS::Partition' },
+                    ':dynamodb:',
+                    { Ref: 'AWS::Region' },
+                    ':',
+                    { Ref: 'AWS::AccountId' },
+                    ':table/MyTableName/index/*',
+                  ]],
+                },
+              ],
+            },
+          ],
+        },
+      });
+    });
   });
 });