split up computeDirId and computeDirIdHash

cryptomator · May 21, 2024 · 81e9ab4 · 81e9ab4
1 parent 7224b46
commit 81e9ab4
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Showing 2 changed files with 20 additions and 5 deletions.
diff --git a/frontend/src/common/universalVaultFormat.ts b/frontend/src/common/universalVaultFormat.ts
@@ -413,18 +413,25 @@ export class UniversalVaultFormat implements AccessTokenProducing, VaultTemplate
     return this.metadata.encrypt(apiURL, vault, this.memberKey, this.recoveryKey);
   }
 
-  public async computeRootDirIdHash(): Promise<string> {
+  public async computeRootDirId(): Promise<Uint8Array> {
     const textencoder = new TextEncoder();
-    const initialSeed = await crypto.subtle.importKey('raw', this.metadata.initialSeed, { name: 'HKDF' }, false, ['deriveBits', 'deriveKey']);
+    const initialSeed = await crypto.subtle.importKey('raw', this.metadata.initialSeed, { name: 'HKDF' }, false, ['deriveBits']);
     const rootDirId = await crypto.subtle.deriveBits({ name: 'HKDF', hash: 'SHA-512', salt: this.metadata.kdfSalt, info: textencoder.encode('rootDirId') }, initialSeed, 256);
+    return new Uint8Array(rootDirId);
+  }
+
+  public async computeRootDirIdHash(rootDirId: Uint8Array): Promise<string> {
+    const textencoder = new TextEncoder();
+    const initialSeed = await crypto.subtle.importKey('raw', this.metadata.initialSeed, { name: 'HKDF' }, false, ['deriveKey']);
     const hmacKey = await crypto.subtle.deriveKey({ name: 'HKDF', hash: 'SHA-512', salt: this.metadata.kdfSalt, info: textencoder.encode('hmac') }, initialSeed, { name: 'HMAC', hash: 'SHA-256' }, false, ['sign']);
     const rootDirHash = await crypto.subtle.sign("HMAC", hmacKey, rootDirId);
     return base32.stringify(new Uint8Array(rootDirHash).slice(0, 20));
   }
 
   /** @inheritdoc */
   public async exportTemplate(apiURL: string, vault: VaultDto): Promise<Blob> {
-    const rootDirHash = await this.computeRootDirIdHash();
+    const rootDirId = await this.computeRootDirId();
+    const rootDirHash = await this.computeRootDirIdHash(rootDirId);
     const zip = new JSZip();
     zip.file('vault.uvf', this.createMetadataFile(apiURL, vault));
     zip.folder('d')?.folder(rootDirHash.substring(0, 2))?.folder(rootDirHash.substring(2)); // TODO verify after merging https://github.com/encryption-alliance/unified-vault-format/pull/24

diff --git a/frontend/test/common/universalVaultFormat.spec.ts b/frontend/test/common/universalVaultFormat.spec.ts
@@ -270,8 +270,16 @@ describe('UVF', () => {
         expect(jwk.kid).to.not.be.empty;
       });
 
-      it('computeRootDirIdHash() creates a hash', async () => {
-        const hash = await uvf.computeRootDirIdHash();
+      it('computeRootDirId() deterministically creates a dir ID', async () => {
+        const dirId = await uvf.computeRootDirId();
+        expect(dirId).to.have.a.lengthOf(32);
+        expect(base64.stringify(dirId)).to.eq('24UBEDeGu5taq7U4GqyA0MXUXb9HTYS6p3t9vvHGJAc=');
+      });
+
+      it('computeRootDirIdHash() creates a truncated hmac', async () => {
+        const rootDirId = base64.parse('24UBEDeGu5taq7U4GqyA0MXUXb9HTYS6p3t9vvHGJAc=');
+        const hash = await uvf.computeRootDirIdHash(rootDirId);
+        expect(hash).to.have.a.lengthOf(32);
         expect(hash).to.eq('6DYU3E5BTPAZ4DWEQPQK3AIHX2DXSPHG');
       });
     });