/** * **The `node:wasi` module does not currently provide the** * **comprehensive file system security properties provided by some WASI runtimes.** * **Full support for secure file system sandboxing may or may not be implemented in** * **future. In the mean time, do not rely on it to run untrusted code.** * * The WASI API provides an implementation of the [WebAssembly System Interface](https://wasi.dev/) specification. WASI gives WebAssembly applications access to the underlying * operating system via a collection of POSIX-like functions. * * ```js * import { readFile } from 'node:fs/promises'; * import { WASI } from 'wasi'; * import { argv, env } from 'node:process'; * * const wasi = new WASI({ * version: 'preview1', * args: argv, * env, * preopens: { * '/local': '/some/real/path/that/wasm/can/access', * }, * }); * * const wasm = await WebAssembly.compile( * await readFile(new URL('./demo.wasm', import.meta.url)), * ); * const instance = await WebAssembly.instantiate(wasm, wasi.getImportObject()); * * wasi.start(instance); * ``` * * To run the above example, create a new WebAssembly text format file named `demo.wat`: * * ```text * (module * ;; Import the required fd_write WASI function which will write the given io vectors to stdout * ;; The function signature for fd_write is: * ;; (File Descriptor, *iovs, iovs_len, nwritten) -> Returns number of bytes written * (import "wasi_snapshot_preview1" "fd_write" (func $fd_write (param i32 i32 i32 i32) (result i32))) * * (memory 1) * (export "memory" (memory 0)) * * ;; Write 'hello world\n' to memory at an offset of 8 bytes * ;; Note the trailing newline which is required for the text to appear * (data (i32.const 8) "hello world\n") * * (func $main (export "_start") * ;; Creating a new io vector within linear memory * (i32.store (i32.const 0) (i32.const 8)) ;; iov.iov_base - This is a pointer to the start of the 'hello world\n' string * (i32.store (i32.const 4) (i32.const 12)) ;; iov.iov_len - The length of the 'hello world\n' string * * (call $fd_write * (i32.const 1) ;; file_descriptor - 1 for stdout * (i32.const 0) ;; *iovs - The pointer to the iov array, which is stored at memory location 0 * (i32.const 1) ;; iovs_len - We're printing 1 string stored in an iov - so one. * (i32.const 20) ;; nwritten - A place in memory to store the number of bytes written * ) * drop ;; Discard the number of bytes written from the top of the stack * ) * ) * ``` * * Use [wabt](https://github.com/WebAssembly/wabt) to compile `.wat` to `.wasm` * * ```bash * wat2wasm demo.wat * ``` * @experimental * @see [source](https://github.com/nodejs/node/blob/v22.x/lib/wasi.js) */ declare module "wasi" { interface WASIOptions { /** * An array of strings that the WebAssembly application will * see as command line arguments. The first argument is the virtual path to the * WASI command itself. * @default [] */ args?: string[] | undefined; /** * An object similar to `process.env` that the WebAssembly * application will see as its environment. * @default {} */ env?: object | undefined; /** * This object represents the WebAssembly application's * sandbox directory structure. The string keys of `preopens` are treated as * directories within the sandbox. The corresponding values in `preopens` are * the real paths to those directories on the host machine. */ preopens?: NodeJS.Dict | undefined; /** * By default, when WASI applications call `__wasi_proc_exit()` * `wasi.start()` will return with the exit code specified rather than terminatng the process. * Setting this option to `false` will cause the Node.js process to exit with * the specified exit code instead. * @default true */ returnOnExit?: boolean | undefined; /** * The file descriptor used as standard input in the WebAssembly application. * @default 0 */ stdin?: number | undefined; /** * The file descriptor used as standard output in the WebAssembly application. * @default 1 */ stdout?: number | undefined; /** * The file descriptor used as standard error in the WebAssembly application. * @default 2 */ stderr?: number | undefined; /** * The version of WASI requested. * Currently the only supported versions are `'unstable'` and `'preview1'`. This option is mandatory. * @since v19.8.0 */ version: "unstable" | "preview1"; } /** * The `WASI` class provides the WASI system call API and additional convenience * methods for working with WASI-based applications. Each `WASI` instance * represents a distinct environment. * @since v13.3.0, v12.16.0 */ class WASI { constructor(options?: WASIOptions); /** * Return an import object that can be passed to `WebAssembly.instantiate()` if no other WASM imports are needed beyond those provided by WASI. * * If version `unstable` was passed into the constructor it will return: * * ```js * { wasi_unstable: wasi.wasiImport } * ``` * * If version `preview1` was passed into the constructor or no version was specified it will return: * * ```js * { wasi_snapshot_preview1: wasi.wasiImport } * ``` * @since v19.8.0 */ getImportObject(): object; /** * Attempt to begin execution of `instance` as a WASI command by invoking its `_start()` export. If `instance` does not contain a `_start()` export, or if `instance` contains an `_initialize()` * export, then an exception is thrown. * * `start()` requires that `instance` exports a [`WebAssembly.Memory`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Memory) named `memory`. If * `instance` does not have a `memory` export an exception is thrown. * * If `start()` is called more than once, an exception is thrown. * @since v13.3.0, v12.16.0 */ start(instance: object): number; // TODO: avoid DOM dependency until WASM moved to own lib. /** * Attempt to initialize `instance` as a WASI reactor by invoking its `_initialize()` export, if it is present. If `instance` contains a `_start()` export, then an exception is thrown. * * `initialize()` requires that `instance` exports a [`WebAssembly.Memory`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Memory) named `memory`. * If `instance` does not have a `memory` export an exception is thrown. * * If `initialize()` is called more than once, an exception is thrown. * @since v14.6.0, v12.19.0 */ initialize(instance: object): void; // TODO: avoid DOM dependency until WASM moved to own lib. /** * `wasiImport` is an object that implements the WASI system call API. This object * should be passed as the `wasi_snapshot_preview1` import during the instantiation * of a [`WebAssembly.Instance`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Instance). * @since v13.3.0, v12.16.0 */ readonly wasiImport: NodeJS.Dict; // TODO: Narrow to DOM types } } declare module "node:wasi" { export * from "wasi"; }