Using Plugin Permissions

The goal of this exercise is to get a better understanding on how plugin permissions can be enabled or disabled, where they are described and how to use default permissions of plugins.

At the end you will have the ability to find and use permissions of arbitrary plugins and understand how to custom tailor existing permissions. You will have an example Tauri application where a plugin and plugin specific permissions are used.

1. Create Tauri Application

   Create your Tauri application. In our example we will facilitate create-tauri-app:

   Bash

   sh <(curl https://create.tauri.app/sh) --beta

   PowerShell

   $env:CTA_ARGS="--beta"; irm https://create.tauri.app/ps | iex

   npm

   npm create tauri-app@latest -- --beta

   Yarn

   yarn create tauri-app --beta

   pnpm

   pnpm create tauri-app --beta

   bun

   bun create tauri-app --beta

   Cargo

   cargo install create-tauri-app
   cargo create-tauri-app --beta

   We will proceed in this step-by-step explanation with pnpm but you can choose another package manager and replace it in the commands accordingly.

   Show solution

   pnpm create tauri-app

   ✔ Project name · plugin-permission-demo
   ✔ Choose which language to use for your frontend · TypeScript / JavaScript - (pnpm, yarn, npm, bun)
   ✔ Choose your package manager · pnpm
   ✔ Choose your UI template · Vanilla
   ✔ Choose your UI flavor · TypeScript
   
   Template created! To get started run:
   cd plugin-permission-demo
   pnpm install
   pnpm tauri dev

2. Add the file-system Plugin to Your Application

   To search for existing plugins you can use multiple resources.

   The most straight forward way would be to check out if your plugin is already in the Plugins section of the documentation and therefore part of Tauri’s maintained plugin set. The Filesystem plugin is part of the Tauri plugin workspace and you can add it to your project by following the instructions.

   If the plugin is part of the community effort you can most likely find it on crates.io when searching for tauri-plugin-<your plugin name>.

   Show solution

   If it is an existing plugin from our workspace you can use the automated way:

   pnpm tauri add fs

   If you have found it on crates.io you need to manually add it as a dependency and modify the Tauri builder to initialize the plugin:

   cargo add tauri-plugin-fs

   Modify lib.rs to initialize the plugin:

   src-tauri/src/lib.rs

   #[cfg_attr(mobile, tauri::mobile_entry_point)]
   fn run() {
     tauri::Builder::default()
       .plugin(tauri_plugin_fs::init())
       .run(tauri::generate_context!())
       .expect("error while running tauri application");
   }

3. Understand the Default Permissions of the fs Plugin

   Each plugin has a default permission set, which contains all permissions and scopes to use the plugin out of the box with a reasonable minimal feature set.

   In the case of official maintained plugins you can find a rendered description in the documentation (eg. fs default).

   In case you are figuring this out for a community plugin you need to check out the source code of the plugin. This should be defined in your-plugin/permissions/default.toml.

   Show solution

   "$schema" = "schemas/schema.json"
   
   [default]
   description = """
   # Tauri `fs` default permissions
   
   This configuration file defines the default permissions granted
   to the filesystem.
   
   ### Granted Permissions
   
   This default permission set enables all read-related commands and
   allows access to the `$APP` folder and sub directories created in it.
   The location of the `$APP` folder depends on the operating system,
   where the application is run.
   
   In general the `$APP` folder needs to be manually created
   by the application at runtime, before accessing files or folders
   in it is possible.
   
   ### Denied Permissions
   
   This default permission set prevents access to critical components
   of the Tauri application by default.
   On Windows the webview data folder access is denied.
   
   """
   permissions = ["read-all", "scope-app-recursive", "deny-default"]

4. Find the Right Permissions

   This step is all about finding the permissions you need to for your commands to be exposed to the frontend with the minimal access to your system.

   The fs plugin has autogenerated permissions which will disable or enable individual commands and allow or disable global scopes.

   These can be found in the documentation or in the source code of the plugin (fs/permissions/autogenerated).

   Let us assume we want to enable writing to a text file test.txt located in the users $HOME folder.

   For this we would search in the autogenerated permissions for a permission to enable writing to text files like allow-write-text-file and then for a scope which would allow us to access the $HOME/test.txt file.

   We need to add these to our capabilities section in our src-tauri/tauri.conf.json or in a file in the src-tauri/capabilities/ folder. By default there is already a capability in src-tauri/capabilities/main.json we can modify.

   Show solution

   src-tauri/capabilities/default.json

   {
     "$schema": "../gen/schemas/desktop-schema.json",
     "identifier": "default",
     "description": "Capability for the main window",
     "windows": [
       "main"
     ],
     "permissions": [
       "path:default",
       "event:default",
       "window:default",
       "app:default",
       "image:default",
       "resources:default",
       "menu:default",
       "tray:default",
       "shell:allow-open",
       "fs:default",
       "fs:allow-write-text-file",
     ]
   }

   Since there are only autogenerated scopes in the fs plugin to access the full $HOME folder, we need to configure our own scope. This scope should be only enabled for the write-text-file command and should only expose our test.txt file.

   Show solution

   src-tauri/capabilities/default.json

      {
     "$schema": "../gen/schemas/desktop-schema.json",
     "identifier": "default",
     "description": "Capability for the main window",
     "windows": [
       "main"
     ],
     "permissions": [
       "path:default",
       "event:default",
       "window:default",
       "app:default",
       "image:default",
       "resources:default",
       "menu:default",
       "tray:default",
       "shell:allow-open",
       "fs:allow-write-text-file",
       {
         "identifier": "fs:allow-write-text-file",
         "allow": [{ "path": "$HOME/test.txt" }]
       },
     ]
   }

5. Test Permissions in Practice

   After we have added the necessary permission we want to confirm that our application can access the file and write it’s content.

   Show solution

   We can use this snippet in our application to write to the file:

   src/main.ts

   import { writeTextFile, BaseDirectory } from '@tauri-apps/plugin-fs';
   
   let greetInputEl: HTMLInputElement | null;
   
   async function write(message: string) {
       await writeTextFile('test.txt', message, { baseDir: BaseDirectory.Home });
   }
   
   window.addEventListener("DOMContentLoaded", () => {
     greetInputEl = document.querySelector("#greet-input");
     document.querySelector("#greet-form")?.addEventListener("submit", (e) => {
       e.preventDefault();
       if (!greetInputEl )
         return;
   
       write(greetInputEl.value == "" ? "No input provided": greetInputEl.value);
   
     });
   });

   Replacing the src/main.ts with this snippet means we do not need to modify the default index.html, when using the plain Vanilla+Typescript app. Entering any input into the input field of the running app will be written to the file on submit.

   Let’s test now in practice:

   pnpm run tauri dev

   After writing into the input and clicking “Submit”, we can check via our terminal emulator or by manually opening the file in your home folder.

   cat $HOME/test.txt

   You should be presented with your input and finished learning about using permissions from plugins in Tauri applications. 🥳

   If you encountered this error:

   [Error] Unhandled Promise Rejection: fs.write_text_file not allowed. Permissions associated with this command: fs:allow-app-write, fs:allow-app-write-recursive, fs:allow-appcache-write, fs:allow-appcache-write-recursive, fs:allow-appconf...
   (anonymous function) (main.ts:5)

   Then you very likely did not properly follow the previous instructions.