Expose the QR code parsing structs used by the QR login mechanism

Author: poljar

CHANGELOG.md

@@ -1,5 +1,9 @@
 # UNRELEASED
 
+-   Add `QrCodeData` and `QrCodeMode` classes which can be used to parse or
+    generate QR codes intended for the QR code login mechanism described in
+    [MSC4108](https://github.com/matrix-org/matrix-spec-proposals/pull/4108).
+
 -   Update matrix-rust-sdk to `35173347f`, which includes:
 
     -   Add data types to parse the QR code data for the QR code login defined in

Cargo.lock

@@ -67,6 +67,7 @@ serde_json = "1.0.91"
 serde-wasm-bindgen = "0.5.0"
 tracing = { version = "0.1.36", default-features = false, features = ["std"] }
 tracing-subscriber = { version = "0.3.14", default-features = false, features = ["registry", "std", "ansi"] }
+url = "2.5.0"
 wasm-bindgen = "0.2.89"
 wasm-bindgen-futures = "0.4.33"
 zeroize = "1.6.0"

Cargo.toml

@@ -32,6 +32,7 @@ pub mod libolm_migration;
 pub mod machine;
 mod macros;
 pub mod olm;
+pub mod qr_login;
 pub mod requests;
 pub mod responses;
 pub mod store;

src/lib.rs

@@ -0,0 +1,140 @@
+//! Types for QR code login
+
+use matrix_sdk_crypto::types::qr_login;
+use url::Url;
+use wasm_bindgen::prelude::*;
+
+use crate::vodozemac::Curve25519PublicKey;
+
+/// The mode of the QR code login.
+///
+/// The QR code login mechanism supports both, the new device, as well as the
+/// existing device to display the QR code.
+///
+/// The different modes have an explicit one-byte identifier which gets added to
+/// the QR code data.
+#[wasm_bindgen]
+#[derive(Debug)]
+pub enum QrCodeMode {
+    /// Enum variant for the case where the new device is displaying the QR
+    /// code.
+    Login,
+    /// Enum variant for the case where the existing device is displaying the QR
+    /// code.
+    Reciprocate,
+}
+
+impl From<qr_login::QrCodeMode> for QrCodeMode {
+    fn from(value: qr_login::QrCodeMode) -> Self {
+        match value {
+            qr_login::QrCodeMode::Login => Self::Login,
+            qr_login::QrCodeMode::Reciprocate => Self::Reciprocate,
+        }
+    }
+}
+
+/// Data for the QR code login mechanism.
+///
+/// The [`QrCodeData`] can be serialized and encoded as a QR code or it can be
+/// decoded from a QR code.
+#[wasm_bindgen]
+#[derive(Debug)]
+pub struct QrCodeData {
+    inner: qr_login::QrCodeData,
+}
+
+#[wasm_bindgen]
+impl QrCodeData {
+    /// Create new [`QrCodeData`] from a given public key, a rendezvous URL and,
+    /// optionally, a homeserver ULR.
+    ///
+    /// If a homeserver URL is given, then the [`QrCodeData`] mode will be
+    /// [`QrCodeMode::Reciprocate`], i.e. the QR code will contain data for the
+    /// existing device to display the QR code.
+    ///
+    /// If no homeserver is given, the [`QrCodeData`] mode will be
+    /// [`QrCodeMode::Login`], i.e. the QR code will contain data for the
+    /// new device to display the QR code.
+    #[wasm_bindgen(constructor)]
+    pub fn new(
+        public_key: Curve25519PublicKey,
+        rendezvous_url: &str,
+        homeserver_url: Option<String>,
+    ) -> Result<QrCodeData, JsError> {
+        let public_key = public_key.inner;
+        let rendezvous_url = Url::parse(rendezvous_url)?;
+
+        let mode_data = if let Some(homeserver_url) = homeserver_url {
+            qr_login::QrCodeModeData::Reciprocate { homeserver_url: Url::parse(&homeserver_url)? }
+        } else {
+            qr_login::QrCodeModeData::Login
+        };
+
+        let inner = qr_login::QrCodeData { public_key, rendezvous_url, mode_data };
+
+        Ok(QrCodeData { inner })
+    }
+
+    /// Attempt to decode a slice of bytes into a [`QrCodeData`] object.
+    ///
+    /// The slice of bytes would generally be returned by a QR code decoder.
+    pub fn from_bytes(bytes: &[u8]) -> Result<QrCodeData, JsError> {
+        Ok(Self { inner: qr_login::QrCodeData::from_bytes(bytes)? })
+    }
+
+    /// Encode the [`QrCodeData`] into a list of bytes.
+    ///
+    /// The list of bytes can be used by a QR code generator to create an image
+    /// containing a QR code.
+    pub fn to_bytes(&self) -> Vec<u8> {
+        self.inner.to_bytes()
+    }
+
+    /// Attempt to decode a base64 encoded string into a [`QrCodeData`] object.
+    pub fn from_base64(data: &str) -> Result<QrCodeData, JsError> {
+        Ok(Self { inner: qr_login::QrCodeData::from_base64(data)? })
+    }
+
+    /// Encode the [`QrCodeData`] into a list of bytes.
+    ///
+    /// The list of bytes can be used by a QR code generator to create an image
+    /// containing a QR code.
+    pub fn to_base64(&self) -> String {
+        self.inner.to_base64()
+    }
+
+    /// Get the Curve25519 public key embedded in the [`QrCodeData`].
+    ///
+    /// This Curve25519 public key should be used to establish an ECIES channel
+    /// with the other device.
+    #[wasm_bindgen(getter)]
+    pub fn public_key(&self) -> Curve25519PublicKey {
+        self.inner.public_key.into()
+    }
+
+    /// Get the URL of the rendezvous server which will be used to exchange
+    /// devices between the two devices.
+    #[wasm_bindgen(getter)]
+    pub fn rendezvous_url(&self) -> String {
+        self.inner.rendezvous_url.as_str().to_owned()
+    }
+
+    /// Get the homeserver URL which the new device will be logged in to.
+    ///
+    /// This will be only available if the existing device has generated the QR
+    /// code and the new device is the one scanning the QR code.
+    #[wasm_bindgen(getter)]
+    pub fn homeserver_url(&self) -> Option<String> {
+        if let qr_login::QrCodeModeData::Reciprocate { homeserver_url } = &self.inner.mode_data {
+            Some(homeserver_url.as_str().to_owned())
+        } else {
+            None
+        }
+    }
+
+    /// Get the mode of this [`QrCodeData`] instance.
+    #[wasm_bindgen(getter)]
+    pub fn mode(&self) -> QrCodeMode {
+        self.inner.mode().into()
+    }
+}

src/qr_login.rs

@@ -0,0 +1,36 @@
+const { QrCodeData, QrCodeMode, Curve25519PublicKey } = require("../pkg/matrix_sdk_crypto_wasm");
+
+describe(QrCodeData.name, () => {
+    test("can parse the QR code bytes from the MSC", () => {
+        const base64Data =
+            "TUFUUklYAgPYhmhqshl7eA4wCp1KIUdIBwDXkp85qzG55RQ3AkjtawBHaHR0cHM6Ly9yZW5kZXp2b3VzLmxhYi5lbGVtZW50LmRldi9lOGRhNjM1NS01NTBiLTRhMzItYTE5My0xNjE5ZDk4MzA2Njg";
+
+        const data = QrCodeData.from_base64(base64Data);
+
+        expect(data.public_key.toBase64()).toStrictEqual("2IZoarIZe3gOMAqdSiFHSAcA15KfOasxueUUNwJI7Ws");
+        expect(data.rendezvous_url).toStrictEqual(
+            "https://rendezvous.lab.element.dev/e8da6355-550b-4a32-a193-1619d9830668",
+        );
+        expect(data.mode).toStrictEqual(QrCodeMode.Login);
+
+        const encoded = data.to_base64();
+
+        expect(base64Data).toStrictEqual(encoded);
+    });
+
+    test("can construct a new QrCodeData class", () => {
+        const base64Data =
+            "TUFUUklYAgPYhmhqshl7eA4wCp1KIUdIBwDXkp85qzG55RQ3AkjtawBHaHR0cHM6Ly9yZW5kZXp2b3VzLmxhYi5lbGVtZW50LmRldi9lOGRhNjM1NS01NTBiLTRhMzItYTE5My0xNjE5ZDk4MzA2Njg";
+        const publicKey = new Curve25519PublicKey("2IZoarIZe3gOMAqdSiFHSAcA15KfOasxueUUNwJI7Ws");
+        const rendezvousUrl = "https://rendezvous.lab.element.dev/e8da6355-550b-4a32-a193-1619d9830668";
+
+        const data = new QrCodeData(publicKey, rendezvousUrl);
+
+        expect(data.public_key.toBase64()).toStrictEqual("2IZoarIZe3gOMAqdSiFHSAcA15KfOasxueUUNwJI7Ws");
+        expect(data.rendezvous_url).toStrictEqual(rendezvousUrl);
+        expect(data.mode).toStrictEqual(QrCodeMode.Login);
+
+        const encoded = data.to_base64();
+        expect(base64Data).toStrictEqual(encoded);
+    });
+});