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feat(mcp): OAuth 2.1 support for outbound MCP servers
Adds full MCP OAuth 2.1 + PKCE + Dynamic Client Registration (RFC 7591) support for outbound MCP servers via the SDK's `authProvider` interface. - `mcp_server_oauth` table holds per-server SDK OAuth artifacts (client info, encrypted tokens, PKCE verifier, state) workspace-scoped and shared across workspace members. - `mcp_servers.{auth_type, oauth_client_id, oauth_client_secret}` columns capture probe result and optional pre-registered credentials for ASes that don't support DCR. - `SimMcpOauthProvider` implements the SDK's `OAuthClientProvider` with a storage-backed redirect-sentinel pattern; the popup flow runs through `/api/mcp/oauth/{start,callback}` and posts back to the opener. - Unauthorized errors during tool execution surface as `reauth_required` so the UI can re-prompt without a stale-server flicker. - Tests, audit script baseline, and turbo bump included.
1 parent 22b5a1e commit 800676b

39 files changed

Lines changed: 19279 additions & 956 deletions

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‎apps/sim/app/api/mcp/oauth/callback/route.ts‎

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import { auth as mcpAuth } from '@modelcontextprotocol/sdk/client/auth.js'
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import { db } from '@sim/db'
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import { mcpServers } from '@sim/db/schema'
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import { createLogger } from '@sim/logger'
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import { toError } from '@sim/utils/errors'
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import { and, eq, isNull } from 'drizzle-orm'
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import type { NextRequest } from 'next/server'
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import { NextResponse } from 'next/server'
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import { getSession } from '@/lib/auth'
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import { withRouteHandler } from '@/lib/core/utils/with-route-handler'
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import {
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clearState,
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clearVerifier,
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loadOauthRowByState,
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loadPreregisteredClient,
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SimMcpOauthProvider,
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} from '@/lib/mcp/oauth'
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import { mcpService } from '@/lib/mcp/service'
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const logger = createLogger('McpOauthCallbackAPI')
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export const dynamic = 'force-dynamic'
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function escapeHtml(value: string): string {
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return value
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.replace(/&/g, '&')
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.replace(/</g, '&lt;')
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.replace(/>/g, '&gt;')
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.replace(/"/g, '&quot;')
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.replace(/'/g, '&#39;')
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}
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function htmlClose(message: string, ok: boolean, serverId?: string): NextResponse {
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const safeMessage = escapeHtml(message)
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const title = ok ? 'Connected' : 'Connection failed'
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const serverIdLiteral = serverId
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? JSON.stringify(serverId).replace(/</g, '\\u003c').replace(/>/g, '\\u003e')
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: 'undefined'
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const body = `<!doctype html><html><head><meta charset="utf-8"><title>${title}</title></head><body style="font-family: system-ui; padding: 24px"><p>${safeMessage}</p><script>
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try { window.opener && window.opener.postMessage({ type: 'mcp-oauth', ok: ${ok ? 'true' : 'false'}, serverId: ${serverIdLiteral} }, window.location.origin) } catch (e) {}
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setTimeout(function () { window.close() }, 800)
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</script></body></html>`
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return new NextResponse(body, {
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headers: { 'Content-Type': 'text/html; charset=utf-8' },
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})
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}
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export const GET = withRouteHandler(async (request: NextRequest) => {
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const url = new URL(request.url)
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const state = url.searchParams.get('state')
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const code = url.searchParams.get('code')
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const errorParam = url.searchParams.get('error')
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if (errorParam) {
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logger.warn(`MCP OAuth callback received error: ${errorParam}`)
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return htmlClose(`Authorization failed: ${errorParam}`, false)
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}
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if (!state || !code) {
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return htmlClose('Missing state or code in callback URL.', false)
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}
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let serverId: string | undefined
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try {
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const session = await getSession()
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if (!session?.user?.id) {
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return htmlClose('You must be signed in to complete authorization.', false)
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}
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const row = await loadOauthRowByState(state)
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if (!row) {
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return htmlClose('Invalid or expired authorization state.', false)
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}
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serverId = row.mcpServerId
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if (session.user.id !== row.userId) {
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return htmlClose(
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'You must be signed in as the same user that initiated the flow.',
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false,
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serverId
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)
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}
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const [server] = await db
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.select({ id: mcpServers.id, url: mcpServers.url, workspaceId: mcpServers.workspaceId })
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.from(mcpServers)
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.where(and(eq(mcpServers.id, row.mcpServerId), isNull(mcpServers.deletedAt)))
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.limit(1)
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if (!server || !server.url) {
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return htmlClose('Server no longer exists.', false, serverId)
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}
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// Burn state before token exchange so a replayed callback cannot reuse it.
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await clearState(row.id)
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const preregistered = await loadPreregisteredClient(server.id)
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const provider = new SimMcpOauthProvider({ row, preregistered })
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let result: Awaited<ReturnType<typeof mcpAuth>>
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try {
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result = await mcpAuth(provider, {
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serverUrl: server.url,
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authorizationCode: code,
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})
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} finally {
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await clearVerifier(row.id)
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}
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if (result !== 'AUTHORIZED') {
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return htmlClose('Authorization did not complete.', false, server.id)
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}
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try {
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await mcpService.clearCache(server.workspaceId)
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await mcpService.discoverServerTools(session.user.id, server.id, server.workspaceId)
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} catch (e) {
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logger.warn('Post-auth tools refresh failed', toError(e).message)
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}
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return htmlClose('Connected. You can close this window.', true, server.id)
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} catch (error) {
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logger.error('MCP OAuth callback failed', error)
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return htmlClose('Authorization failed. Please try again.', false, serverId)
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}
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})

‎apps/sim/app/api/mcp/oauth/start/route.test.ts‎

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/**
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* @vitest-environment node
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*/
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import {
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dbChainMock,
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dbChainMockFns,
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hybridAuthMock,
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hybridAuthMockFns,
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permissionsMock,
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permissionsMockFns,
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resetDbChainMock,
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schemaMock,
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} from '@sim/testing'
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import { NextRequest } from 'next/server'
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import { beforeEach, describe, expect, it, vi } from 'vitest'
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const {
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mockMcpAuth,
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mockGetOrCreateOauthRow,
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mockLoadPreregisteredClient,
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mockSetOauthRowUser,
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MockMcpOauthRedirectRequired,
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} = vi.hoisted(() => ({
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mockMcpAuth: vi.fn(),
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mockGetOrCreateOauthRow: vi.fn(),
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mockLoadPreregisteredClient: vi.fn(),
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mockSetOauthRowUser: vi.fn(),
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MockMcpOauthRedirectRequired: class MockMcpOauthRedirectRequired extends Error {
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constructor(public readonly authorizationUrl: string) {
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super('redirect required')
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}
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},
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}))
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vi.mock('@sim/db', () => dbChainMock)
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vi.mock('@sim/db/schema', () => schemaMock)
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vi.mock('drizzle-orm', () => ({
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and: vi.fn(),
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eq: vi.fn(),
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isNull: vi.fn(),
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}))
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vi.mock('@modelcontextprotocol/sdk/client/auth.js', () => ({
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auth: mockMcpAuth,
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}))
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vi.mock('@/lib/auth/hybrid', () => hybridAuthMock)
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vi.mock('@/lib/workspaces/permissions/utils', () => permissionsMock)
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vi.mock('@/lib/mcp/oauth', () => ({
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getOrCreateOauthRow: mockGetOrCreateOauthRow,
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loadPreregisteredClient: mockLoadPreregisteredClient,
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McpOauthRedirectRequired: MockMcpOauthRedirectRequired,
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setOauthRowUser: mockSetOauthRowUser,
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SimMcpOauthProvider: vi.fn().mockImplementation((value) => value),
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}))
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import { GET } from './route'
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describe('MCP OAuth start route', () => {
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beforeEach(() => {
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vi.clearAllMocks()
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resetDbChainMock()
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hybridAuthMockFns.mockCheckSessionOrInternalAuth.mockResolvedValue({
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success: true,
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userId: 'user-2',
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userName: 'User Two',
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userEmail: 'user2@example.com',
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authType: 'session',
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})
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permissionsMockFns.mockGetUserEntityPermissions.mockResolvedValue('write')
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dbChainMockFns.limit.mockResolvedValue([
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{
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id: 'server-1',
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name: 'Exa',
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url: 'https://mcp.exa.ai/mcp',
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workspaceId: 'workspace-1',
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authType: 'oauth',
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deletedAt: null,
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},
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])
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mockGetOrCreateOauthRow.mockResolvedValue({
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id: 'oauth-row-1',
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mcpServerId: 'server-1',
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userId: 'user-1',
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workspaceId: 'workspace-1',
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clientInformation: null,
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tokens: null,
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codeVerifier: null,
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state: null,
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updatedAt: new Date(),
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})
90+
mockLoadPreregisteredClient.mockResolvedValue(undefined)
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mockMcpAuth.mockRejectedValue(new MockMcpOauthRedirectRequired('https://mcp.exa.ai/authorize'))
92+
})
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it('requires workspace write permission via MCP auth middleware', async () => {
95+
const request = new NextRequest(
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'http://localhost:3000/api/mcp/oauth/start?workspaceId=workspace-1&serverId=server-1'
97+
)
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await GET(request)
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expect(permissionsMockFns.mockGetUserEntityPermissions).toHaveBeenCalledWith(
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'user-2',
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'workspace',
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'workspace-1'
105+
)
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})
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108+
it('uses a workspace-scoped OAuth row and stamps the latest authorizing user', async () => {
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const request = new NextRequest(
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'http://localhost:3000/api/mcp/oauth/start?workspaceId=workspace-1&serverId=server-1'
111+
)
112+
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const response = await GET(request)
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const body = await response.json()
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expect(response.status).toBe(200)
117+
expect(body).toEqual({
118+
status: 'redirect',
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authorizationUrl: 'https://mcp.exa.ai/authorize',
120+
})
121+
expect(mockGetOrCreateOauthRow).toHaveBeenCalledWith({
122+
mcpServerId: 'server-1',
123+
userId: 'user-2',
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workspaceId: 'workspace-1',
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})
126+
expect(mockSetOauthRowUser).toHaveBeenCalledWith('oauth-row-1', 'user-2')
127+
})
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129+
it('rejects a second user starting OAuth while another authorization is active', async () => {
130+
mockGetOrCreateOauthRow.mockResolvedValueOnce({
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id: 'oauth-row-1',
132+
mcpServerId: 'server-1',
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userId: 'user-1',
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workspaceId: 'workspace-1',
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clientInformation: null,
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tokens: null,
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codeVerifier: null,
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state: 'hashed-active-state',
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updatedAt: new Date(),
140+
})
141+
const request = new NextRequest(
142+
'http://localhost:3000/api/mcp/oauth/start?workspaceId=workspace-1&serverId=server-1'
143+
)
144+
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const response = await GET(request)
146+
const body = await response.json()
147+
148+
expect(response.status).toBe(409)
149+
expect(body.error).toBe('OAuth authorization already in progress for this server')
150+
expect(mockMcpAuth).not.toHaveBeenCalled()
151+
})
152+
})

‎apps/sim/app/api/mcp/oauth/start/route.ts‎

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1+
import { auth as mcpAuth } from '@modelcontextprotocol/sdk/client/auth.js'
2+
import { db } from '@sim/db'
3+
import { mcpServers } from '@sim/db/schema'
4+
import { createLogger } from '@sim/logger'
5+
import { toError } from '@sim/utils/errors'
6+
import { and, eq, isNull } from 'drizzle-orm'
7+
import type { NextRequest } from 'next/server'
8+
import { NextResponse } from 'next/server'
9+
import { startMcpOauthQuerySchema } from '@/lib/api/contracts/mcp'
10+
import { validationErrorResponse } from '@/lib/api/server'
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import { withRouteHandler } from '@/lib/core/utils/with-route-handler'
12+
import { withMcpAuth } from '@/lib/mcp/middleware'
13+
import {
14+
getOrCreateOauthRow,
15+
loadPreregisteredClient,
16+
McpOauthRedirectRequired,
17+
SimMcpOauthProvider,
18+
setOauthRowUser,
19+
} from '@/lib/mcp/oauth'
20+
import { createMcpErrorResponse } from '@/lib/mcp/utils'
21+
22+
const logger = createLogger('McpOauthStartAPI')
23+
const OAUTH_START_TTL_MS = 10 * 60 * 1000
24+
25+
export const dynamic = 'force-dynamic'
26+
27+
export const GET = withRouteHandler(
28+
withMcpAuth('write')(async (request: NextRequest, { userId, workspaceId, requestId }) => {
29+
try {
30+
const queryResult = startMcpOauthQuerySchema.safeParse(
31+
Object.fromEntries(new URL(request.url).searchParams)
32+
)
33+
if (!queryResult.success) {
34+
return validationErrorResponse(queryResult.error)
35+
}
36+
const { serverId } = queryResult.data
37+
38+
const [server] = await db
39+
.select()
40+
.from(mcpServers)
41+
.where(
42+
and(
43+
eq(mcpServers.id, serverId),
44+
eq(mcpServers.workspaceId, workspaceId),
45+
isNull(mcpServers.deletedAt)
46+
)
47+
)
48+
.limit(1)
49+
50+
if (!server) {
51+
return createMcpErrorResponse(new Error('Server not found'), 'Server not found', 404)
52+
}
53+
if (server.authType !== 'oauth') {
54+
return createMcpErrorResponse(
55+
new Error(`Server authType is "${server.authType}", not oauth`),
56+
'Server is not configured for OAuth',
57+
400
58+
)
59+
}
60+
if (!server.url) {
61+
return createMcpErrorResponse(new Error('Server has no URL'), 'Missing server URL', 400)
62+
}
63+
64+
const row = await getOrCreateOauthRow({
65+
mcpServerId: server.id,
66+
userId,
67+
workspaceId,
68+
})
69+
const hasActiveFlow = !!row.state && row.updatedAt.getTime() > Date.now() - OAUTH_START_TTL_MS
70+
if (hasActiveFlow && row.userId && row.userId !== userId) {
71+
return createMcpErrorResponse(
72+
new Error('OAuth authorization already in progress'),
73+
'OAuth authorization already in progress for this server',
74+
409
75+
)
76+
}
77+
if (row.userId !== userId) {
78+
await setOauthRowUser(row.id, userId)
79+
row.userId = userId
80+
}
81+
const preregistered = await loadPreregisteredClient(server.id)
82+
const provider = new SimMcpOauthProvider({ row, preregistered })
83+
84+
try {
85+
const result = await mcpAuth(provider, { serverUrl: server.url })
86+
if (result === 'AUTHORIZED') {
87+
return NextResponse.json({ status: 'already_authorized' })
88+
}
89+
return createMcpErrorResponse(
90+
new Error('Provider did not capture redirect URL'),
91+
'Failed to start OAuth flow',
92+
500
93+
)
94+
} catch (e) {
95+
if (e instanceof McpOauthRedirectRequired) {
96+
logger.info(`[${requestId}] OAuth redirect for server ${serverId}`)
97+
return NextResponse.json({
98+
status: 'redirect',
99+
authorizationUrl: e.authorizationUrl,
100+
})
101+
}
102+
throw e
103+
}
104+
} catch (error) {
105+
logger.error(`[${requestId}] Error starting MCP OAuth flow:`, error)
106+
return createMcpErrorResponse(toError(error), 'Failed to start OAuth flow', 500)
107+
}
108+
})
109+
)

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