[feat] [biometric] Adding the capability of encrypting/decrypting data using biometric authentication on Android (Ref. #2306) (#2454)

* –feat: adding the ability to encrypt/decrypt data based on the biometric auth

Adding the method biometricCipher() that allows to use the biometric authentication to use a generated key from android that can be accessed only through the biometric authentication. The method uses this key to encrypt/decrypt the data provided by the caller in the "options" parameter, with "dataToEncrypt" or "dataToDecrypt" filled.

Changes were done both on Kotlin, Rust and JS sides.

* Improving the way we encrypt data by allowing only if the biometric was successful.

* Adding a warning on the JS side

* Adding doc changes in readme.md

* Adding doc changes in readme.md

* Update README.md - it was updated incomplete

* update docs

* enhance error handling

* update example

---------

Co-authored-by: Lucas Nogueira <lucas@tauri.app>

examples/api/src-tauri/capabilities/mobile.json

@@ -8,6 +8,8 @@
     "nfc:allow-write",
     "nfc:allow-scan",
     "biometric:allow-authenticate",
+    "biometric:allow-status",
+    "biometric:allow-biometric-cipher",
     "barcode-scanner:allow-scan",
     "barcode-scanner:allow-cancel",
     "barcode-scanner:allow-request-permissions",

examples/api/src/views/Biometric.svelte

@@ -1,9 +1,14 @@
 <script>
-  import { authenticate } from "@tauri-apps/plugin-biometric";
+  import { authenticate, biometricCipher } from "@tauri-apps/plugin-biometric";
+  import * as os from "@tauri-apps/plugin-os";
 
   export let onMessage;
   let allowDeviceCredential = true;
 
+  const isAndroid = os.platform() === "android";
+  let plainText = "";
+  let encryptedData = "";
+
   function auth() {
     authenticate("Tauri API wants to show it is awesome :)", {
       allowDeviceCredential,
@@ -17,14 +22,62 @@
       .then(onMessage)
       .catch(onMessage);
   }
+
+  function encrypt() {
+    biometricCipher("Authenticate to encrypt the data", {
+      title: "Tauri API Encrypt",
+      cancelTitle: "Cancel",
+      dataToEncrypt: plainText,
+    })
+      .then(({ data }) => {
+        encryptedData = data;
+        onMessage(`Encrypted: ${data}`);
+      })
+      .catch(onMessage);
+  }
+
+  function decrypt() {
+    biometricCipher("Authenticate to decrypt the data", {
+      title: "Tauri API Decrypt",
+      cancelTitle: "Cancel",
+      dataToDecrypt: encryptedData,
+    })
+      .then(({ data }) => onMessage(`Decrypted: ${data}`))
+      .catch(onMessage);
+  }
 </script>
 
 <div>
   <input
     type="checkbox"
-    id="dllowDeviceCredential"
+    id="allowDeviceCredential"
     bind:checked={allowDeviceCredential}
   />
-  <label for="allowDeviceCredentiale">Allow device credential</label>
+  <label for="allowDeviceCredential">Allow device credential</label>
 </div>
-<button class="btn" id="cli-matches" on:click={auth}> Authenticate </button>
+<button class="btn" id="biometric-authenticate" on:click={auth}>
+  Authenticate
+</button>
+
+{#if isAndroid}
+  <div class="flex flex-col gap-2 mt-4">
+    <h3>Biometric cipher</h3>
+    <input class="input" placeholder="Data to encrypt" bind:value={plainText} />
+    <button class="btn" id="biometric-encrypt" on:click={encrypt}>
+      Encrypt
+    </button>
+    <input
+      class="input"
+      placeholder="Encrypted data"
+      bind:value={encryptedData}
+    />
+    <button
+      class="btn"
+      id="biometric-decrypt"
+      disabled={!encryptedData}
+      on:click={decrypt}
+    >
+      Decrypt
+    </button>
+  </div>
+{/if}