generalize auth provider stuff

src/lib/server/auth/discord.ts

@@ -4,24 +4,71 @@
 // file lmao. also hopefully i will rewrite this to be better at extending to
 // other oauth providers in the future
 
+import type {AuthProviderImplementation} from '.';
+
 import {env} from '$env/dynamic/private';
 
-/** The redirect URI for Discord to send the user back to. */
-const discordRedirectURI = `${env.HOST}/auth/discord/callback`;
+const redirectURI = `${env.HOST}/auth/discord/callback`;
+const scopes = ['identify'];
 
-/** The base of the URI that starts the OAuth flow. State is attached later. */
-// Long URIs suck
-const discordAuthURIBase = 'https://discordapp.com/api/oauth2/authorize'
-	+ `?client_id=${env.DISCORD_CLIENT_ID}`
-	+ '&response_type=code'
-	+ `&redirect_uri=${encodeURIComponent(discordRedirectURI)}`
-	+ `&scope=${encodeURIComponent(['identify', 'guilds'].join(' '))}`
-	+ '&prompt=consent'; // Special Discord-only thing to always show prompt
+export default {
+	redirectURI,
+	buildAuthURI: state =>
+		'https://discordapp.com/api/oauth2/authorize'
+		+ `?client_id=${env.DISCORD_CLIENT_ID}`
+		+ '&response_type=code'
+		+ `&redirect_uri=${encodeURIComponent(redirectURI)}`
+		+ `&scope=${encodeURIComponent(scopes.join(' '))}`
+		+ '&prompt=consent' // Special Discord-only thing to always show prompt
+		+ `&state=${encodeURIComponent(state)}`,
+	async getUserIdentifier (code, {fetch}) {
+		// exchange code for tokens
+		const tokenResponse = await fetch(
+			'https://discordapp.com/api/oauth2/token',
+			{
+				method: 'POST',
+				headers: {
+					'Content-Type': 'application/x-www-form-urlencoded',
+				},
+				body: formData({
+					client_id: env.DISCORD_CLIENT_ID,
+					client_secret: env.DISCORD_CLIENT_SECRET,
+					grant_type: 'authorization_code',
+					code,
+					redirect_uri: redirectURI,
+					// Discord-specific: scope is required here and must match
+					scope: scopes.join(' '),
+				}),
+			},
+		);
+		if (tokenResponse.status !== 200) {
+			throw new Error(`error requesting tokens: ${tokenResponse.status}`);
+		}
+		const tokensData = await tokenResponse.json();
+		if (tokensData.error) {
+			throw new Error(`error requesting tokens: ${tokensData.error}`);
+		}
 
-/** Generates an auth URI to redirect the user to given a state. */
-function authURI (state: string) {
-	return `${discordAuthURIBase}&state=${encodeURIComponent(state)}`;
-}
+		// use access token to get user info
+		const userInfoResponse = await fetch(
+			'https://discordapp.com/api/v6/users/@me',
+			{
+				headers: {
+					Authorization: `Bearer ${tokensData.access_token}`,
+				},
+			},
+		);
+		if (userInfoResponse.status !== 200) {
+			throw new Error(
+				`error requesting user info: ${tokenResponse.status}`,
+			);
+		}
+		const userInfo = await userInfoResponse.json();
+
+		// return the user's service-unique ID
+		return userInfo.id;
+	},
+} satisfies AuthProviderImplementation;
 
 /** Generates a formdata body from key-value pairs. */
 function formData (content: Record<string, string>) {
@@ -29,114 +76,3 @@ function formData (content: Record<string, string>) {
 		.map(([k, v]) => `${encodeURIComponent(k)}=${encodeURIComponent(v)}`)
 		.join('&');
 }
-
-/**
- * Generates an avatar URL for the user. Discord avatars are weird so I split
- * this out.
- * @see https://discordapp.com/developers/docs/reference#image-formatting
- */
-export function discordAvatarURL (userInfo: {
-	id: string;
-	avatar?: string;
-	discriminator: string;
-}) {
-	if (userInfo.avatar) {
-		return `https://cdn.discordapp.com/avatars/${userInfo.id}/${userInfo.avatar}.png`;
-	}
-	return `https://cdn.discordapp.com/embed/avatars/${
-		parseInt(userInfo.discriminator, 10) % 5
-	}.png`;
-}
-
-/** OAuth tokens returned by Discord. */
-export interface DiscordTokens {
-	/** The access token used to authorize to Discord */
-	accessToken: string;
-	/** The refresh token used to get a new access token when the current one expires */
-	refreshToken: string;
-	/** The string "Bearer"; other token types aren't relevant here */
-	tokenType: string;
-	/** space-separated list of authorized scopes */
-	scope: string;
-	/** Expiration date of the access token */
-	expiresAt: Date;
-}
-
-/** Exchanges a code for an access/refresh token pair. */
-export async function fetchDiscordTokens (
-	code: string,
-): Promise<DiscordTokens> {
-	const response = await fetch('https://discordapp.com/api/oauth2/token', {
-		method: 'POST',
-		headers: {
-			'Content-Type': 'application/x-www-form-urlencoded',
-		},
-		body: formData({
-			client_id: env.DISCORD_CLIENT_ID,
-			client_secret: env.DISCORD_CLIENT_SECRET,
-			grant_type: 'authorization_code',
-			code,
-			redirect_uri: discordRedirectURI,
-			scope: 'identify', // Discord-specific: scope is required here too and must match
-		}),
-	});
-
-	if (response.status !== 200) {
-		throw new Error(
-			`Discord gave non-200 response status when requesting tokens: ${response.status}`,
-		);
-	}
-
-	const data = await response.json();
-	if (data.error) {
-		throw new Error(
-			`Discord gave an error when requesting tokens: ${data.error}`,
-		);
-	}
-	return {
-		accessToken: data.access_token,
-		refreshToken: data.refresh_token,
-		tokenType: data.token_type,
-		scope: data.scope,
-		expiresAt: new Date(Date.now() + data.expires_in * 1000),
-	};
-}
-
-/** Information about a Discord user. */
-export interface DiscordUserInfo {
-	id: string;
-	username: string;
-	discriminator: string;
-	avatarURL: string;
-}
-
-/**
- * Fetches information about the user given their access token.
- * @param {string} accessToken
- * @returns {Promise<object>} Object has keys `name`, `avatarURL`, and
- * `created`.
- */
-export async function fetchDiscordUserInfo (
-	fetch: any,
-	accessToken: string,
-): Promise<DiscordUserInfo> {
-	const response = await fetch('https://discordapp.com/api/v6/users/@me', {
-		headers: {
-			Authorization: `Bearer ${accessToken}`,
-		},
-	});
-
-	if (response.status !== 200) {
-		throw new Error(
-			`Discord gave non-200 status when fetching user info: ${response.status}`,
-		);
-	}
-
-	const data = await response.json();
-	return {
-		username: data.username,
-		discriminator: data.discriminator,
-		id: data.id,
-		avatarURL: discordAvatarURL(data),
-	};
-}

src/lib/server/auth/index.ts

@@ -0,0 +1,22 @@
+import type {ServerLoadEvent} from '@sveltejs/kit';
+import DiscordAuthImplementation from './discord';
+
+export enum AuthProvider {
+	DISCORD,
+}
+
+export interface AuthProviderImplementation {
+	redirectURI: string;
+	buildAuthURI: (state: string) => string;
+	getUserIdentifier: (
+		code: string,
+		event: ServerLoadEvent,
+	) => Promise<string>;
+}
+
+export const authProviderImplementations: Record<
+	AuthProvider,
+	AuthProviderImplementation
+> = {
+	[AuthProvider.DISCORD]: DiscordAuthImplementation,
+};

src/lib/server/entity/AuthMethod.ts

@@ -1,11 +1,8 @@
 import {BeforeInsert, Column, Entity, ManyToOne, PrimaryColumn} from 'typeorm';
 
+import {AuthProvider} from '$lib/server/auth';
+import {User} from '$lib/server/entity/User';
 import {ulidMonotonic} from '$lib/server/ulid';
-import {User} from './User';
-
-export enum AuthProvider {
-	DISCORD,
-}
 
 @Entity()
 export class AuthMethod {

src/lib/server/entity/AuthSession.ts

@@ -1,51 +1,19 @@
-import {BeforeInsert, Column, Entity, ManyToOne, PrimaryColumn} from 'typeorm';
-import {EncryptionTransformer} from 'typeorm-encrypted';
+import {BeforeInsert, Entity, ManyToOne, PrimaryColumn} from 'typeorm';
 
-import {AuthProvider} from '$lib/server/entity/AuthMethod';
+import {AuthMethod} from '$lib/server/entity/AuthMethod';
 import {ulidMonotonic} from '$lib/server/ulid';
 
-import {env} from '$env/dynamic/private';
-
 @Entity()
 export class AuthSession {
 	/** The ID of the session */
-	// TODO should we be using ulids for this or something totally random
+	// TODO should we be using ulids for this or something crypt-random
 	@PrimaryColumn({type: 'varchar', length: 26, nullable: false})
 	id = ulidMonotonic();
 
-	/** The authentication provider used to start this session */
-	@Column({type: 'enum', enum: AuthProvider, nullable: false})
-	provider!: AuthProvider;
+	@ManyToOne(() => AuthMethod, authMethod => authMethod.id, {nullable: false})
+	authMethod!: AuthMethod;
 
-	/** The access token */
-	@Column({
-		type: 'varchar',
-		length: 300,
-		nullable: false,
-		transformer: new EncryptionTransformer({
-			algorithm: 'aes-256-cbc',
-			key: env.ENCRYPTION_KEY!,
-			ivLength: 16,
-		}),
-	})
-	accessToken!: string;
-
-	/** The refresh token */
-	@Column({
-		type: 'varchar',
-		length: 300,
-		nullable: true,
-		transformer: new EncryptionTransformer({
-			algorithm: 'aes-256-cbc',
-			key: env.ENCRYPTION_KEY!,
-			ivLength: 16,
-		}),
-	})
-	refreshToken!: string;
-
-	/** When the access token expires */
-	@Column({type: 'timestamptz', nullable: true})
-	accessTokenExpiresAt!: Date;
+	// TODO expiration of sessions?
 
 	@BeforeInsert()
 	private beforeInsert () {

src/lib/server/entity/AuthState.ts

@@ -1,7 +1,7 @@
 import * as crypto from 'node:crypto';
 import {BeforeInsert, Column, Entity, ManyToOne, PrimaryColumn} from 'typeorm';
 
-import {AuthProvider} from '$lib/server/entity/AuthMethod';
+import {AuthProvider} from '$lib/server/auth';
 import {ulidMonotonic} from '$lib/server/ulid';
 
 @Entity()

src/routes/+layout.server.ts

@@ -1,4 +1,3 @@
-import {discordAvatarURL} from '$lib/server/auth/discord';
 import {getDataSource} from '$lib/server/db';
 import {AuthSession} from '$lib/server/entity/AuthSession';
 
@@ -14,38 +13,22 @@ async function findSession (sessionID?: string) {
 
 export const load: LayoutServerLoad = async ({cookies}) => {
 	const sessionID = cookies.get('sessionid');
-	let session = await findSession(sessionID);
-	if (!session) {
-		return {};
-	}
-	console.log('i am happening');
-
-	const response = await fetch('https://discordapp.com/api/v6/users/@me', {
-		headers: {
-			Authorization: `Bearer ${session.accessToken}`,
-		},
-	});
-
-	if (response.status !== 200) {
-		console.log(await response.text());
-		return {
-			error: {
-				code: 'user_info_fetch_failed',
-				description:
-					`Discord gave non-200 status when fetching user info: ${response.status}`,
+	const dataSource = await getDataSource();
+	const sessionsRepo = dataSource.getRepository(AuthSession);
+	const session = sessionID
+		? await sessionsRepo.findOne({
+			where: {id: sessionID},
+			relations: {
+				authMethod: {
+					user: true,
+				},
 			},
-		};
-	}
-
-	const data = await response.json();
-	console.log('have data', data.username);
+		})
+		: null;
 
 	return {
-		user: {
-			username: data.username,
-			discriminator: data.discriminator,
-			id: data.id,
-			avatarURL: discordAvatarURL(data),
-		},
+		user: session
+			? JSON.parse(JSON.stringify(session.authMethod.user))
+			: null,
 	};
 };

src/routes/+page.svelte

@@ -5,8 +5,7 @@
 
 {#if data.user}
 	<h1>Success!</h1>
-	<p>You are {data.user.username}#{data.user.discriminator} and your ID is {data.user.id}</p>
-	<img src={data.user.avatarURL} alt="Discord avatar of {data.user.username}">
+	<p>You are {data.user.name} and your ID is {data.user.id}</p>
 {:else}
 	<h1>Hello</h1>
 	<p>I do not know you</p>

src/routes/auth/[provider]/+page.server.ts

@@ -0,0 +1,38 @@
+import {redirect} from '@sveltejs/kit';
+import * as crypto from 'node:crypto';
+
+import {getDataSource} from '$lib/server/db';
+import {AuthState} from '$lib/server/entity/AuthState';
+
+import {env} from '$env/dynamic/private';
+import {
+	AuthProvider,
+	type AuthProviderImplementation,
+	authProviderImplementations,
+} from '$lib/server/auth';
+import type {PageServerLoad} from './$types';
+
+export const load: PageServerLoad = async ({cookies, params}) => {
+	// figure out what auth provider the user wanted to try
+	let provider: AuthProvider;
+	if (params.provider === 'discord') {
+		provider = AuthProvider.DISCORD;
+	} else {
+		// idk thats not a valid provider, uhh,
+		throw redirect(302, '/');
+	}
+
+	const dataSource = await getDataSource();
+	const providerImpl = authProviderImplementations[provider];
+
+	// store a state for this login attempt
+	const authStatesRepo = await dataSource.getRepository(AuthState);
+	const state = authStatesRepo.create({provider});
+	await authStatesRepo.save(state);
+
+	// set the state ID as a cookie so we can retrieve it later and compare
+	cookies.set('stateid', state.id, {path: '/auth/discord'});
+
+	// redirect to the provider with the state
+	throw redirect(302, providerImpl.buildAuthURI(state.state));
+};

src/routes/auth/[provider]/callback/+page.server.ts

@@ -0,0 +1,108 @@
+import {getDataSource} from '$lib/server/db';
+import {AuthSession} from '$lib/server/entity/AuthSession';
+import {AuthState} from '$lib/server/entity/AuthState';
+import {redirect} from '@sveltejs/kit';
+import type {PageServerLoad} from './$types';
+
+import {AuthProvider, authProviderImplementations} from '$lib/server/auth';
+import {AuthMethod} from '$lib/server/entity/AuthMethod';
+import {User} from '$lib/server/entity/User';
+
+export const load: PageServerLoad = async event => {
+	// figure out what auth provider has redirected the user here
+	let provider: AuthProvider;
+	if (event.params.provider === 'discord') {
+		provider = AuthProvider.DISCORD;
+	} else {
+		// idk thats not a valid provider, uhh,
+		throw redirect(302, '/');
+	}
+
+	// check for errors from the provider
+	// TODO: this is still technically provider-specific and should be split out
+	// into the provider implementations since different providers can call back
+	// with different parameters
+	const errorCode = event.url.searchParams.get('error');
+	const errorDescription = event.url.searchParams.get('error_description');
+
+	// if the user cancelled the login, redirect home gracefully
+	if (errorCode === 'access_denied') {
+		throw redirect(302, '/');
+	}
+
+	// if another error was encountered, return the error information only
+	if (errorCode) {
+		return {
+			error: {
+				code: errorCode,
+				description: errorDescription ?? '',
+			},
+		};
+	}
+
+	const providerImpl = authProviderImplementations[provider];
+
+	// retrieve the state we stored for this session and compare against the
+	// state we received from the provider
+	const dataSource = await getDataSource();
+	const statesRepo = dataSource.getRepository(AuthState);
+
+	const stateID = event.cookies.get('stateid');
+	let storedState: AuthState | null = null;
+	if (stateID) {
+		storedState = await statesRepo.findOne({where: {id: stateID}});
+	}
+
+	const receivedState = event.url.searchParams.get('state');
+
+	if (!storedState || !receivedState || storedState.state !== receivedState) {
+		return {
+			error: {
+				code: 'consumer_state_mismatch',
+				description:
+					`Expected state ${storedState?.state}, received ${receivedState}`,
+			},
+		};
+	}
+
+	const code = event.url.searchParams.get('code');
+	if (!code) {
+		return {
+			error: {
+				code: 'no_code',
+				description: 'No code was received',
+			},
+		};
+	}
+
+	// trade in the code for a user identifier
+	const userIdentifier = await providerImpl.getUserIdentifier(code, event);
+
+	// see if any users have registered matching authentication methods
+	const authMethodsRepo = dataSource.getRepository(AuthMethod);
+	let authMethod = await authMethodsRepo.findOne({
+		where: {
+			provider,
+			userIdentifier,
+		},
+	});
+
+	// if there is not yet anyone registered using this auth method, create a
+	// new user and a new auth method for that user
+	if (!authMethod) {
+		throw redirect(302, '/'); // TODO
+	}
+
+	// Create a new auth session for this auth method and save it
+	const authSessionRepo = dataSource.getRepository(AuthSession);
+	const authSession = authSessionRepo.create({authMethod});
+	await authSessionRepo.save(authSession);
+	event.cookies.set('sessionid', authSession.id, {path: '/'});
+
+	// remove the state we were using now that we're done with it
+	await statesRepo.remove(storedState);
+	event.cookies.delete('stateid');
+
+	// Woo we did it, redirect on to wherever we were trying to go before
+	throw redirect(302, '/');
+};

src/routes/auth/discord/+page.server.ts

@@ -1,40 +0,0 @@
-import {redirect} from '@sveltejs/kit';
-import * as crypto from 'node:crypto';
-
-import {getDataSource} from '$lib/server/db';
-import {AuthState} from '$lib/server/entity/AuthState';
-
-import {env} from '$env/dynamic/private';
-import {AuthProvider} from '$lib/server/entity/AuthMethod.js';
-
-/**
- * The redirect URI for Discord to send the user back to after auth. This must
- * match what's configured for the OAuth application in the dev applications
- * panel in order to fetch tokens.
- */
-const discordRedirectURI = `${env.HOST}/auth/discord/callback`;
-
-/** The base of the URI that starts the OAuth flow. State is attached later. */
-const authURIBase = 'https://discordapp.com/api/oauth2/authorize'
-	+ `?client_id=${env.DISCORD_CLIENT_ID}`
-	+ '&response_type=code'
-	+ `&redirect_uri=${encodeURIComponent(discordRedirectURI)}`
-	+ `&scope=${encodeURIComponent(['identify', 'guilds'].join(' '))}`
-	+ '&prompt=consent'; // Special Discord-only thing to always show prompt
-
-/** Generates a complete auth URI given a state. */
-const buildAuthURI = (state: string) =>
-	`${authURIBase}&state=${encodeURIComponent(state)}`;
-
-export async function load ({cookies}) {
-	const dataSource = await getDataSource();
-
-	const authStatesRepo = await dataSource.getRepository(AuthState);
-	const state = authStatesRepo.create({
-		provider: AuthProvider.DISCORD,
-	});
-	await authStatesRepo.save(state);
-
-	cookies.set('stateid', state.id, {path: '/auth/discord'});
-	throw redirect(302, buildAuthURI(state.state));
-}

src/routes/auth/discord/callback/+page.server.ts

@@ -1,97 +0,0 @@
-import {
-	discordAvatarURL,
-	type DiscordUserInfo,
-	fetchDiscordTokens,
-	fetchDiscordUserInfo,
-} from '$lib/server/auth/discord';
-import {getDataSource} from '$lib/server/db';
-import {AuthProvider} from '$lib/server/entity/AuthMethod';
-import {AuthSession} from '$lib/server/entity/AuthSession';
-import {AuthState} from '$lib/server/entity/AuthState';
-import {redirect} from '@sveltejs/kit';
-import type {PageServerLoad} from './$types';
-
-export const load: PageServerLoad = async ({cookies, url, fetch}) => {
-	const errorCode = url.searchParams.get('error');
-	const errorDescription = url.searchParams.get('error_description');
-
-	// if the user cancelled the login, redirect home gracefully
-	if (errorCode === 'access_denied') {
-		throw redirect(302, '/');
-	}
-
-	// if another error was encountered, return the error information only
-	if (errorCode) {
-		return {
-			error: {
-				code: errorCode,
-				description: errorDescription ?? '',
-			},
-		};
-	}
-
-	// retrieve the state we stored for this session and compare against the
-	// state we received from the provider
-	const dataSource = await getDataSource();
-	const statesRepo = dataSource.getRepository(AuthState);
-
-	const stateID = cookies.get('stateid');
-	let storedState: AuthState | null = null;
-	if (stateID) {
-		storedState = await statesRepo.findOne({where: {id: stateID}});
-	}
-
-	const receivedState = url.searchParams.get('state');
-
-	if (!storedState || !receivedState || storedState.state !== receivedState) {
-		return {
-			error: {
-				code: 'consumer_state_mismatch',
-				description:
-					`Expected state ${storedState?.state}, received ${receivedState}`,
-			},
-		};
-	}
-
-	// everything checks out - exchange code for tokens
-	const code = url.searchParams.get('code');
-	if (!code) {
-		return {
-			error: {
-				code: 'no_code',
-				description: 'No code was received',
-			},
-		};
-	}
-
-	let tokens;
-	try {
-		tokens = await fetchDiscordTokens(code);
-	} catch (tokenError) {
-		return {
-			error: {
-				code: 'token_exchange_failed',
-				description:
-					`Failed to exchange code for tokens: ${tokenError}`,
-			},
-		};
-	}
-
-	// Create a new auth session from the tokens and save it
-	const authSessionRepo = dataSource.getRepository(AuthSession);
-	const authSession = authSessionRepo.create({
-		provider: AuthProvider.DISCORD,
-		accessToken: tokens.accessToken,
-		refreshToken: tokens.refreshToken,
-		accessTokenExpiresAt: tokens.expiresAt,
-	});
-	await authSessionRepo.save(authSession);
-	cookies.set('sessionid', authSession.id, {path: '/'});
-
-	// remove the state we were using now that we're done with it
-	await statesRepo.remove(storedState);
-	cookies.delete('stateid');
-
-	// Woo we did it, redirect on to wherever we were trying to go before
-	throw redirect(302, '/');
-};