feat: 🎸 add integrity check on read

docs/casfs/index.md

@@ -53,7 +53,7 @@ const blob2 = await cas.get(hash);
 You can also delete blobs:
 
 ```js
-await cas.delete(hash);
+await cas.del(hash);
 ```
 
 And retrieve information about blobs:

src/crud-to-cas/CrudCas.ts

@@ -1,5 +1,5 @@
 import { hashToLocation } from './util';
-import type { CasApi } from '../cas/types';
+import type { CasApi, CasGetOptions } from '../cas/types';
 import type { CrudApi, CrudResourceInfo } from '../crud/types';
 
 export interface CrudCasOptions {
@@ -31,10 +31,15 @@ export class CrudCas implements CasApi {
     return digest;
   };
 
-  public readonly get = async (hash: string): Promise<Uint8Array> => {
+  public readonly get = async (hash: string, options?: CasGetOptions): Promise<Uint8Array> => {
     const [collection, resource] = hashToLocation(hash);
     return await normalizeErrors(async () => {
-      return await this.crud.get(collection, resource);
+      const blob = await this.crud.get(collection, resource);
+      if (!options?.skipVerification) {
+        const digest = await this.options.hash(blob);
+        if (hash !== digest) throw new DOMException('Blob contents does not match hash', 'Integrity');
+      }
+      return blob;
     });
   };
 

src/crud-to-cas/__tests__/CrudCas.test.ts

@@ -5,6 +5,7 @@ import { onlyOnNode20 } from '../../__tests__/util';
 import { NodeFileSystemDirectoryHandle } from '../../node-to-fsa';
 import { FsaCrud } from '../../fsa-to-crud/FsaCrud';
 import { CrudCas } from '../CrudCas';
+import { hashToLocation } from '../util';
 
 const hash = async (blob: Uint8Array): Promise<string> => {
   const shasum = createHash('sha1');
@@ -53,6 +54,27 @@ onlyOnNode20('CrudCas', () => {
       expect(err).toBeInstanceOf(DOMException);
       expect((<any>err).name).toBe('BlobNotFound');
     });
+
+    test('throws if blob contents does not match the hash', async () => {
+      const blob = b('hello world');
+      const { cas, crud } = setup();
+      const hash = await cas.put(blob);
+      const location = hashToLocation(hash);
+      await crud.put(location[0], location[1], b('hello world!'));
+      const [, err] = await of(cas.get(hash));
+      expect(err).toBeInstanceOf(DOMException);
+      expect((<any>err).name).toBe('Integrity');
+    });
+
+    test('does not throw if integrity check is skipped', async () => {
+      const blob = b('hello world');
+      const { cas, crud } = setup();
+      const hash = await cas.put(blob);
+      const location = hashToLocation(hash);
+      await crud.put(location[0], location[1], b('hello world!'));
+      const blob2 = await cas.get(hash, { skipVerification: true });
+      expect(blob2).toStrictEqual(b('hello world!'));
+    });
   });
 
   describe('.info()', () => {