fix(server-sdk): throw on failed auth requests instead of returning the error body

.changeset/server-auth-getuser-errors.md

@@ -0,0 +1,6 @@
+---
+"@crossmint/server-sdk": patch
+"@crossmint/common-sdk-auth": patch
+---
+
+`CrossmintAuth.getUser` now throws a `CrossmintAuthenticationError` when Crossmint rejects the request, instead of returning the API's error body as if it were the user. The error carries the HTTP `status` and the API's message, and on a 401 or 403 it says that `getUser` needs a server API key with the `users.read` scope. `getUser` now returns `SDKExternalUser` instead of `any`, and the server SDK exports `CrossmintAuthenticationError` and `SDKExternalUser`. Failed session refreshes and logouts also report the status and the API's message.

packages/common/auth/src/CrossmintAuth.ts

@@ -1,5 +1,6 @@
 import { type Crossmint, CrossmintApiClient } from "@crossmint/common-sdk-base";
 import { AUTH_SDK_ROOT_ENDPOINT, SDK_NAME, SDK_VERSION } from "./utils/constants";
+import { authErrorFromResponse } from "./utils/authErrorFromResponse";
 import { type AuthMaterialWithUser, CrossmintAuthenticationError, type AuthMaterialResponse } from "./types";
 
 export type CrossmintAuthOptions = {
@@ -51,7 +52,7 @@ export class CrossmintAuth {
         });
 
         if (!result.ok) {
-            throw new CrossmintAuthenticationError(result.statusText);
+            throw await authErrorFromResponse(result, "Failed to refresh the session");
         }
 
         const resultJson = (await result.json()) as AuthMaterialResponse;
@@ -76,12 +77,11 @@ export class CrossmintAuth {
             },
         });
 
-        const resultJson = await result.json();
         if (!result.ok) {
-            throw new CrossmintAuthenticationError(resultJson.message);
+            throw await authErrorFromResponse(result, "Failed to refresh the session from the custom refresh route");
         }
 
-        return resultJson;
+        return await result.json();
     }
 
     protected async logoutFromDefaultRoute(refreshToken: string) {

packages/common/auth/src/types/errors.ts

@@ -1 +1,9 @@
-export class CrossmintAuthenticationError extends Error {}
+export class CrossmintAuthenticationError extends Error {
+    /** HTTP status of the Crossmint API response that caused the error, when there was one. */
+    public readonly status?: number;
+
+    constructor(message?: string, options?: { status?: number }) {
+        super(message);
+        this.status = options?.status;
+    }
+}

packages/common/auth/src/utils/authErrorFromResponse.test.ts

@@ -0,0 +1,47 @@
+import { describe, expect, it } from "vitest";
+import { authErrorFromResponse } from "./authErrorFromResponse";
+
+describe("authErrorFromResponse", () => {
+    const cases: { name: string; response: Response; hint?: string; message: string }[] = [
+        {
+            name: "uses the API's message",
+            response: new Response(JSON.stringify({ message: "User not found" }), { status: 404 }),
+            message: "Failed to get user (404: User not found)",
+        },
+        {
+            name: "joins a list of validation messages",
+            response: new Response(JSON.stringify({ message: ["refresh must be a string", "refresh is required"] }), {
+                status: 400,
+            }),
+            message: "Failed to get user (400: refresh must be a string, refresh is required)",
+        },
+        {
+            name: "falls back to the error field",
+            response: new Response(JSON.stringify({ error: "Bad Gateway" }), { status: 502 }),
+            message: "Failed to get user (502: Bad Gateway)",
+        },
+        {
+            name: "falls back to the status text when the body is not JSON",
+            response: new Response("<html>nope</html>", { status: 503, statusText: "Service Unavailable" }),
+            message: "Failed to get user (503: Service Unavailable)",
+        },
+        {
+            name: "reports only the status when there is no body and no status text",
+            response: new Response(null, { status: 500 }),
+            message: "Failed to get user (500)",
+        },
+        {
+            name: "appends the hint",
+            response: new Response(JSON.stringify({ message: "Forbidden" }), { status: 403 }),
+            hint: "needs users.read",
+            message: "Failed to get user (403: Forbidden). needs users.read",
+        },
+    ];
+
+    it.each(cases)("$name", async ({ response, hint, message }) => {
+        const error = await authErrorFromResponse(response, "Failed to get user", hint);
+
+        expect(error.message).toBe(message);
+        expect(error.status).toBe(response.status);
+    });
+});

packages/common/auth/src/utils/authErrorFromResponse.ts

@@ -0,0 +1,31 @@
+import { CrossmintAuthenticationError } from "../types/errors";
+
+/**
+ * Build a `CrossmintAuthenticationError` from a failed Crossmint API response. The error keeps the HTTP status
+ * and the API's own message, so the caller sees why the request failed. `hint` is appended to the message.
+ */
+export async function authErrorFromResponse(
+    response: Response,
+    action: string,
+    hint?: string
+): Promise<CrossmintAuthenticationError> {
+    const details = (await readApiErrorMessage(response)) ?? response.statusText;
+    const message = `${action} (${response.status}${details ? `: ${details}` : ""})${hint ? `. ${hint}` : ""}`;
+    return new CrossmintAuthenticationError(message, { status: response.status });
+}
+
+async function readApiErrorMessage(response: Response): Promise<string | undefined> {
+    try {
+        const body = JSON.parse(await response.text());
+        const message = body?.message ?? body?.error;
+        if (typeof message === "string") {
+            return message;
+        }
+        if (Array.isArray(message)) {
+            return message.join(", ");
+        }
+    } catch (_) {
+        // The body is missing or not JSON: fall back to the status text.
+    }
+    return undefined;
+}

packages/common/auth/src/utils/index.ts

@@ -1,2 +1,3 @@
 export * from "./constants";
 export * from "./isEmailValid";
+export * from "./authErrorFromResponse";

packages/server/README.md

@@ -10,6 +10,17 @@ To install the SDK, you can use npm or yarn:
 npm install @crossmint/server-sdk
 ```
 
+## API key and scopes
+
+Use a server-side API key (`sk_...`) from the Crossmint Console. Which scopes it needs depends on the methods you call:
+
+| Method                                           | Scope        |
+| ------------------------------------------------ | ------------ |
+| `getSession`, `handleCustomRefresh`, `logout`    | None         |
+| `getUser`                                        | `users.read` |
+
+`getSession` verifies the JWT with Crossmint's public keys and refreshes the session through endpoints that do not check scopes. `getUser` reads the user's profile, so the key needs `users.read`. Without it, `getUser` throws a `CrossmintAuthenticationError` with `status` 403.
+
 ## Usage
 
 To use the SDK in your application, follow these steps:
@@ -49,15 +60,33 @@ const { jwt, userId } = await crossmintAuth.getSession({
 });
 ```
 
-3. Store the authentication material in cookies
+3. Get the user's profile
+
+`getSession` returns the user's ID. To get their email, phone number or linked X account, pass the ID to `getUser`. It needs the `users.read` scope on your API key:
+
+```ts
+import { CrossmintAuthenticationError } from "@crossmint/server-sdk";
+
+try {
+    const user = await crossmintAuth.getUser(userId); // { id, email?, phoneNumber?, twitter? }
+} catch (error) {
+    if (error instanceof CrossmintAuthenticationError) {
+        // error.status is 403 when the API key lacks users.read, 404 when the user has not signed in to this project
+        console.error(error.status, error.message);
+    }
+    throw error;
+}
+```
+
+4. Store the authentication material in cookies
 
 If you are using a framework with access to the response object, you can store the authentication material in cookies by passing the response object to the `getSession` method:
 
 ```ts
 const { jwt, userId } = await crossmintAuth.getSession(request, response);
 ```
 
-4. Logout
+5. Logout
 
 ```ts
 await crossmintAuth.logout(request);

packages/server/src/auth/CrossmintAuthServer.ts

@@ -8,6 +8,8 @@ import {
     type AuthMaterial,
     CROSSMINT_API_VERSION,
     type CookieOptions,
+    type SDKExternalUser,
+    authErrorFromResponse,
 } from "@crossmint/common-sdk-auth";
 import { validateAPIKey, type Crossmint, type CrossmintApiClient } from "@crossmint/common-sdk-base";
 import {
@@ -34,7 +36,8 @@ export type CrossmintAuthServerOptions = CrossmintAuthOptions & {
  * fetch users, and manage auth cookies. Works with both Node.js (`IncomingMessage`/`ServerResponse`)
  * and Fetch API (`Request`/`Response`) request/response objects.
  *
- * Create an instance with {@link CrossmintAuthServer.from}.
+ * Create an instance with {@link CrossmintAuthServer.from} and a server-side API key. Sessions, refreshes and
+ * logout need no API key scope; {@link CrossmintAuthServer.getUser} needs `users.read`.
  */
 export class CrossmintAuthServer extends CrossmintAuth {
     private cookieOptions: CookieOptions;
@@ -89,16 +92,32 @@ export class CrossmintAuthServer extends CrossmintAuth {
         }
     }
 
-    /** Fetch the Crossmint user associated with the given external user ID. */
-    public async getUser(externalUserId: string) {
-        const result = await this.apiClient.get(`api/${CROSSMINT_API_VERSION}/sdk/auth/user/${externalUserId}`, {
-            headers: {
-                "Content-Type": "application/json",
-            },
-        });
+    /**
+     * Fetch the user with the given ID (the `userId` from {@link CrossmintAuthServer.getSession}, the JWT's `sub`).
+     * Needs a server API key with the `users.read` scope.
+     *
+     * @throws CrossmintAuthenticationError with the HTTP `status` if Crossmint rejects the request, for example
+     * 403 when the API key lacks the `users.read` scope or 404 when the user has not signed in to this project.
+     */
+    public async getUser(externalUserId: string): Promise<SDKExternalUser> {
+        const result = await this.apiClient.get(
+            `api/${CROSSMINT_API_VERSION}/sdk/auth/user/${encodeURIComponent(externalUserId)}`,
+            {
+                headers: {
+                    "Content-Type": "application/json",
+                },
+            }
+        );
+
+        if (!result.ok) {
+            const hint =
+                result.status === 401 || result.status === 403
+                    ? "getUser needs a server API key with the users.read scope"
+                    : undefined;
+            throw await authErrorFromResponse(result, "Failed to get user", hint);
+        }
 
-        const user = await result.json();
-        return user;
+        return (await result.json()) as SDKExternalUser;
     }
 
     /**
@@ -185,7 +204,10 @@ export class CrossmintAuthServer extends CrossmintAuth {
             if (request != null) {
                 const authCookies = getAuthCookies(request);
                 if (authCookies != null) {
-                    await this.logoutFromDefaultRoute(authCookies.refreshToken);
+                    const result = await this.logoutFromDefaultRoute(authCookies.refreshToken);
+                    if (!result.ok) {
+                        throw await authErrorFromResponse(result, "Failed to log out");
+                    }
                 }
             }
         } catch (error) {

packages/server/src/auth/crossmint-auth-server.test.ts

@@ -457,9 +457,7 @@ describe("CrossmintAuthServer", () => {
         it("fetches user data for a given external user ID", async () => {
             const mockExternalUserId = "external-user-123";
             const mockUserData = { id: "user456", email: "user@example.com" };
-            mockApiClient.get.mockResolvedValue({
-                json: () => Promise.resolve(mockUserData),
-            });
+            mockApiClient.get.mockResolvedValue(new Response(JSON.stringify(mockUserData), { status: 200 }));
 
             const result = await crossmintAuthServer.getUser(mockExternalUserId);
 
@@ -469,6 +467,53 @@ describe("CrossmintAuthServer", () => {
                 expect.any(Object)
             );
         });
+
+        it("encodes the user ID so it cannot change the request path", async () => {
+            mockApiClient.get.mockResolvedValue(new Response(JSON.stringify({ id: "x" }), { status: 200 }));
+
+            await crossmintAuthServer.getUser("a/b?c");
+
+            expect(mockApiClient.get).toHaveBeenCalledWith(
+                "api/2024-09-26/sdk/auth/user/a%2Fb%3Fc",
+                expect.any(Object)
+            );
+        });
+
+        it("throws with the API message and the required scope when the API key lacks users.read", async () => {
+            const apiMessage =
+                "The API key provided doesn't have the required scopes to perform this action: users.read. It has the scopes: wallets.read.";
+            mockApiClient.get.mockResolvedValue(
+                new Response(JSON.stringify({ statusCode: 403, message: apiMessage, error: "Forbidden" }), {
+                    status: 403,
+                    statusText: "Forbidden",
+                })
+            );
+
+            const error = await crossmintAuthServer.getUser("external-user-123").catch((e) => e);
+
+            expect(error).toBeInstanceOf(CrossmintAuthenticationError);
+            expect(error.status).toBe(403);
+            expect(error.message).toContain(apiMessage);
+            expect(error.message).toContain("getUser needs a server API key with the users.read scope");
+        });
+
+        it("throws with the status and no scope hint when the user is not found", async () => {
+            mockApiClient.get.mockResolvedValue(
+                new Response(
+                    JSON.stringify({ statusCode: 404, message: "User with id external-user-123 not found." }),
+                    {
+                        status: 404,
+                        statusText: "Not Found",
+                    }
+                )
+            );
+
+            const error = await crossmintAuthServer.getUser("external-user-123").catch((e) => e);
+
+            expect(error).toBeInstanceOf(CrossmintAuthenticationError);
+            expect(error.status).toBe(404);
+            expect(error.message).toBe("Failed to get user (404: User with id external-user-123 not found.)");
+        });
     });
 
     describe("storeAuthMaterial", () => {
@@ -755,6 +800,27 @@ describe("CrossmintAuthServer", () => {
             );
         });
 
+        it("returns the API's reason when Crossmint rejects the refresh token", async () => {
+            const mockRequest = new Request("http://test.com", {
+                method: "POST",
+                body: JSON.stringify({ refresh: "mock-refresh-token" }),
+            });
+            mockApiClient.post.mockResolvedValue(
+                new Response(JSON.stringify({ statusCode: 401, message: "Invalid refresh token" }), {
+                    status: 401,
+                    statusText: "Unauthorized",
+                })
+            );
+
+            const result = (await crossmintAuthServer.handleCustomRefresh(mockRequest)) as Response;
+
+            expect(result.status).toBe(401);
+            expect(await result.json()).toEqual({
+                error: "Unauthorized",
+                message: "Failed to refresh the session (401: Invalid refresh token)",
+            });
+        });
+
         it("throws error when refresh token is missing", async () => {
             const mockRequest = new Request("http://test.com", {
                 method: "POST",

packages/server/src/auth/index.ts

@@ -1,3 +1,4 @@
 export { CrossmintAuthServer as CrossmintAuth, type CrossmintAuthServerOptions } from "./CrossmintAuthServer";
 export type { GenericRequest, GenericResponse } from "./types/request";
 export * from "./utils";
+export { CrossmintAuthenticationError, type SDKExternalUser } from "@crossmint/common-sdk-auth";