Add device IDs endowment

Author: Mrtenz

packages/examples/packages/ledger/snap.manifest.json

@@ -1,7 +1,7 @@
 {
   "version": "2.1.3",
-  "description": "MetaMask example snap demonstrating the use of the `onInstall` and `onUpdate` lifecycle hooks.",
-  "proposedName": "Lifecycle Hooks Example Snap",
+  "description": "MetaMask example Snap demonstrating how to communicate with a Ledger hardware wallet.",
+  "proposedName": "Ledger Example Snap",
   "repository": {
     "type": "git",
     "url": "https://github.com/MetaMask/snaps.git"
@@ -11,14 +11,13 @@
     "location": {
       "npm": {
         "filePath": "dist/bundle.js",
-        "packageName": "@metamask/lifecycle-hooks-example-snap",
+        "packageName": "@metamask/ledger-example-snap",
         "registry": "https://registry.npmjs.org"
       }
     }
   },
   "initialPermissions": {
-    "snap_dialog": {},
-    "endowment:lifecycle-hooks": {}
+    "endowment:devices": {}
   },
   "manifestVersion": "0.1"
 }

packages/snaps-rpc-methods/src/endowments/devices.ts

@@ -0,0 +1,126 @@
+import type {
+  Caveat,
+  CaveatSpecificationConstraint,
+  EndowmentGetterParams,
+  PermissionConstraint,
+  PermissionSpecificationBuilder,
+  ValidPermissionSpecification,
+} from '@metamask/permission-controller';
+import { PermissionType, SubjectType } from '@metamask/permission-controller';
+import { rpcErrors } from '@metamask/rpc-errors';
+import type { DeviceSpecification } from '@metamask/snaps-utils';
+import {
+  SnapCaveatType,
+  isDeviceSpecificationArray,
+} from '@metamask/snaps-utils';
+import { hasProperty, isPlainObject, assert } from '@metamask/utils';
+
+import { SnapEndowments } from './enum';
+
+const permissionName = SnapEndowments.Devices;
+
+type DevicesEndowmentSpecification = ValidPermissionSpecification<{
+  permissionType: PermissionType.Endowment;
+  targetName: typeof permissionName;
+  endowmentGetter: (_options?: any) => null;
+  allowedCaveats: [SnapCaveatType.DeviceIds];
+}>;
+
+/**
+ * The `endowment:devices` permission is intended to be used as a flag to
+ * determine whether the Snap wants to access the devices API.
+ *
+ * @param _builderOptions - Optional specification builder options.
+ * @returns The specification for the network endowment.
+ */
+const specificationBuilder: PermissionSpecificationBuilder<
+  PermissionType.Endowment,
+  any,
+  DevicesEndowmentSpecification
+> = (_builderOptions?: any) => {
+  return {
+    permissionType: PermissionType.Endowment,
+    targetName: permissionName,
+    allowedCaveats: [SnapCaveatType.DeviceIds],
+    endowmentGetter: (_getterOptions?: EndowmentGetterParams) => null,
+    subjectTypes: [SubjectType.Snap],
+  };
+};
+
+export const devicesEndowmentBuilder = Object.freeze({
+  targetName: permissionName,
+  specificationBuilder,
+} as const);
+
+/**
+ * Getter function to get the permitted device IDs from a permission
+ * specification.
+ *
+ * This does basic validation of the caveat, but does not validate the type or
+ * value of the namespaces object itself, as this is handled by the
+ * `PermissionsController` when the permission is requested.
+ *
+ * @param permission - The permission to get the keyring namespaces from.
+ * @returns The device IDs, or `null` if the permission does not have a
+ * device IDs caveat.
+ */
+export function getPermittedDeviceIds(
+  permission?: PermissionConstraint,
+): DeviceSpecification[] | null {
+  if (!permission?.caveats) {
+    return null;
+  }
+
+  assert(permission.caveats.length === 1);
+  assert(permission.caveats[0].type === SnapCaveatType.DeviceIds);
+
+  const caveat = permission.caveats[0] as Caveat<
+    string,
+    { devices: DeviceSpecification[] }
+  >;
+
+  return caveat.value?.devices ?? null;
+}
+
+/**
+ * Validate the cronjob specification values associated with a caveat.
+ * This validates that the value is a non-empty array with valid device
+ * specification objects.
+ *
+ * @param caveat - The caveat to validate.
+ * @throws If the value is invalid.
+ */
+export function validateDeviceIdsCaveat(caveat: Caveat<string, any>) {
+  if (!hasProperty(caveat, 'value') || !isPlainObject(caveat.value)) {
+    throw rpcErrors.invalidParams({
+      message: 'Expected a plain object.',
+    });
+  }
+
+  const { value } = caveat;
+
+  if (!hasProperty(value, 'devices') || !isPlainObject(value)) {
+    throw rpcErrors.invalidParams({
+      message: 'Expected a plain object.',
+    });
+  }
+
+  if (!isDeviceSpecificationArray(value.jobs)) {
+    throw rpcErrors.invalidParams({
+      message: 'Expected a valid device specification array.',
+    });
+  }
+}
+
+/**
+ * Caveat specification for the device IDs caveat.
+ */
+export const deviceIdsCaveatSpecifications: Record<
+  SnapCaveatType.DeviceIds,
+  CaveatSpecificationConstraint
+> = {
+  [SnapCaveatType.DeviceIds]: Object.freeze({
+    type: SnapCaveatType.DeviceIds,
+    validator: (caveat) => validateDeviceIdsCaveat(caveat),
+  }),
+};

packages/snaps-rpc-methods/src/endowments/enum.ts

@@ -10,4 +10,5 @@ export enum SnapEndowments {
   LifecycleHooks = 'endowment:lifecycle-hooks',
   Keyring = 'endowment:keyring',
   HomePage = 'endowment:page-home',
+  Devices = 'endowment:devices',
 }

packages/snaps-rpc-methods/src/endowments/index.ts

@@ -12,6 +12,10 @@ import {
   cronjobEndowmentBuilder,
   getCronjobCaveatMapper,
 } from './cronjob';
+import {
+  deviceIdsCaveatSpecifications,
+  devicesEndowmentBuilder,
+} from './devices';
 import { ethereumProviderEndowmentBuilder } from './ethereum-provider';
 import { homePageEndowmentBuilder } from './home-page';
 import {
@@ -48,6 +52,7 @@ export const endowmentPermissionBuilders = {
   [transactionInsightEndowmentBuilder.targetName]:
     transactionInsightEndowmentBuilder,
   [cronjobEndowmentBuilder.targetName]: cronjobEndowmentBuilder,
+  [devicesEndowmentBuilder.targetName]: devicesEndowmentBuilder,
   [ethereumProviderEndowmentBuilder.targetName]:
     ethereumProviderEndowmentBuilder,
   [rpcEndowmentBuilder.targetName]: rpcEndowmentBuilder,
@@ -62,6 +67,7 @@ export const endowmentPermissionBuilders = {
 
 export const endowmentCaveatSpecifications = {
   ...cronjobCaveatSpecifications,
+  ...deviceIdsCaveatSpecifications,
   ...transactionInsightCaveatSpecifications,
   ...rpcCaveatSpecifications,
   ...nameLookupCaveatSpecifications,

packages/snaps-utils/src/caveats.ts

@@ -53,4 +53,9 @@ export enum SnapCaveatType {
    * Caveat specifying the max request time for a handler endowment.
    */
   MaxRequestTime = 'maxRequestTime',
+
+  /**
+   * Caveat specifying the device IDs that can be interacted with.
+   */
+  DeviceIds = 'deviceIds',
 }

packages/snaps-utils/src/devices.ts

@@ -0,0 +1,50 @@
+import { deviceId } from '@metamask/snaps-sdk';
+import type { Infer } from '@metamask/superstruct';
+import { array, is, object } from '@metamask/superstruct';
+
+export const DeviceSpecificationStruct = object({
+  /**
+   * The device ID that the Snap has permission to access.
+   */
+  deviceId: deviceId(),
+});
+
+/**
+ * A device specification, which is used as caveat value.
+ */
+export type DeviceSpecification = Infer<typeof DeviceSpecificationStruct>;
+
+/**
+ * Check if the given value is a {@link DeviceSpecification} object.
+ *
+ * @param value - The value to check.
+ * @returns Whether the value is a {@link DeviceSpecification} object.
+ */
+export function isDeviceSpecification(
+  value: unknown,
+): value is DeviceSpecification {
+  return is(value, DeviceSpecificationStruct);
+}
+
+export const DeviceSpecificationArrayStruct = object({
+  devices: array(DeviceSpecificationStruct),
+});
+
+/**
+ * A device specification array, which is used as caveat value.
+ */
+export type DeviceSpecificationArray = Infer<
+  typeof DeviceSpecificationArrayStruct
+>;
+
+/**
+ * Check if the given value is a {@link DeviceSpecificationArray} object.
+ *
+ * @param value - The value to check.
+ * @returns Whether the value is a {@link DeviceSpecificationArray} object.
+ */
+export function isDeviceSpecificationArray(
+  value: unknown,
+): value is DeviceSpecificationArray {
+  return is(value, DeviceSpecificationArrayStruct);
+}

packages/snaps-utils/src/index.ts

@@ -10,6 +10,7 @@ export * from './currency';
 export * from './deep-clone';
 export * from './default-endowments';
 export * from './derivation-paths';
+export * from './devices';
 export * from './entropy';
 export * from './errors';
 export * from './handlers';