From 5b7d918f29423d9308ba80b7fefa9c2da1899b8f Mon Sep 17 00:00:00 2001
From: Oscar Hinton <oscar@oscarhinton.com>
Date: Wed, 28 Apr 2021 22:02:43 +0200
Subject: [PATCH] Validate key before using it (#366)

* Validate key before using it
---
 src/abstractions/crypto.service.ts |  1 +
 src/services/crypto.service.ts     | 48 ++++++++++++++++++++++++++----
 2 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/src/abstractions/crypto.service.ts b/src/abstractions/crypto.service.ts
index 3d5c0242fa..e10eb6ecb1 100644
--- a/src/abstractions/crypto.service.ts
+++ b/src/abstractions/crypto.service.ts
@@ -48,4 +48,5 @@ export abstract class CryptoService {
     decryptToUtf8: (encString: EncString, key?: SymmetricCryptoKey) => Promise<string>;
     decryptFromBytes: (encBuf: ArrayBuffer, key: SymmetricCryptoKey) => Promise<ArrayBuffer>;
     randomNumber: (min: number, max: number) => Promise<number>;
+    validateKey: (key: SymmetricCryptoKey) => Promise<boolean>;
 }
diff --git a/src/services/crypto.service.ts b/src/services/crypto.service.ts
index 958f38ab5d..e930cf9dcc 100644
--- a/src/services/crypto.service.ts
+++ b/src/services/crypto.service.ts
@@ -46,10 +46,7 @@ export class CryptoService implements CryptoServiceAbstraction {
     async setKey(key: SymmetricCryptoKey): Promise<any> {
         this.key = key;
 
-        const option = await this.storageService.get<number>(ConstantsService.vaultTimeoutKey);
-        const biometric = await this.storageService.get<boolean>(ConstantsService.biometricUnlockKey);
-        if (option != null && !(biometric && this.platformUtilService.supportsSecureStorage())) {
-            // if we have a lock option set, we do not store the key
+        if (!await this.shouldStoreKey()) {
             return;
         }
 
@@ -96,7 +93,21 @@ export class CryptoService implements CryptoServiceAbstraction {
 
         const key = await this.secureStorageService.get<string>(Keys.key);
         if (key != null) {
-            this.key = new SymmetricCryptoKey(Utils.fromB64ToArray(key).buffer);
+            if (!await this.shouldStoreKey()) {
+                this.logService.warning('Throwing away stored key since settings have changed');
+                this.secureStorageService.remove(Keys.key);
+                return null;
+            }
+
+            const symmetricKey = new SymmetricCryptoKey(Utils.fromB64ToArray(key).buffer);
+
+            if (!await this.validateKey(symmetricKey)) {
+                this.logService.warning('Wrong key, throwing away stored key');
+                this.secureStorageService.remove(Keys.key);
+                return null;
+            }
+
+            this.key = symmetricKey;
         }
 
         return key == null ? null : this.key;
@@ -580,8 +591,35 @@ export class CryptoService implements CryptoServiceAbstraction {
         return min + rval;
     }
 
+    async validateKey(key: SymmetricCryptoKey) {
+        try {
+            const encPrivateKey = await this.storageService.get<string>(Keys.encPrivateKey);
+            if (encPrivateKey == null) {
+                return false;
+            }
+
+            const encKey = await this.getEncKey(key);
+            const privateKey = await this.decryptToBytes(new EncString(encPrivateKey), encKey);
+            await this.cryptoFunctionService.rsaExtractPublicKey(privateKey);
+        } catch (e) {
+            return false;
+        }
+
+        return true;
+    }
+
     // Helpers
 
+    private async shouldStoreKey() {
+        const vaultTimeout = await this.storageService.get<number>(ConstantsService.vaultTimeoutKey);
+        const biometricUnlock = await this.storageService.get<boolean>(ConstantsService.biometricUnlockKey);
+
+        const biometricsEnabled = biometricUnlock && this.platformUtilService.supportsSecureStorage();
+        const noVaultTimeout = vaultTimeout == null;
+
+        return noVaultTimeout || biometricsEnabled;
+    }
+
     private async aesEncrypt(data: ArrayBuffer, key: SymmetricCryptoKey): Promise<EncryptedObject> {
         const obj = new EncryptedObject();
         obj.key = await this.getKeyForEncryption(key);