simstudioai · waleedlatif1 · May 17, 2026 · May 18, 2026 · May 18, 2026 · May 18, 2026
diff --git a/apps/sim/app/api/mcp/oauth/callback/route.ts b/apps/sim/app/api/mcp/oauth/callback/route.ts
@@ -0,0 +1,181 @@
+import { auth as mcpAuth } from '@modelcontextprotocol/sdk/client/auth.js'
+import { db } from '@sim/db'
+import { mcpServers } from '@sim/db/schema'
+import { createLogger } from '@sim/logger'
+import { toError } from '@sim/utils/errors'
+import { and, eq, isNull } from 'drizzle-orm'
+import type { NextRequest } from 'next/server'
+import { NextResponse } from 'next/server'
+import { mcpOauthCallbackContract } from '@/lib/api/contracts/mcp'
+import { parseRequest } from '@/lib/api/server'
+import { getSession } from '@/lib/auth'
+import { withRouteHandler } from '@/lib/core/utils/with-route-handler'
+import {
+  assertSafeOauthServerUrl,
+  clearState,
+  clearVerifier,
+  loadOauthRowByState,
+  loadPreregisteredClient,
+  type McpOauthCallbackReason,
+  SimMcpOauthProvider,
+} from '@/lib/mcp/oauth'
+import { mcpService } from '@/lib/mcp/service'
+
+const logger = createLogger('McpOauthCallbackAPI')
+
+export const dynamic = 'force-dynamic'
+
+function escapeHtml(value: string): string {
+  return value
+    .replace(/&/g, '&amp;')
+    .replace(/</g, '&lt;')
+    .replace(/>/g, '&gt;')
+    .replace(/"/g, '&quot;')
+    .replace(/'/g, '&#39;')
+}
+
+function jsonLiteral(value: string | undefined): string {
+  if (value === undefined) return 'undefined'
+  return JSON.stringify(value).replace(/</g, '\\u003c').replace(/>/g, '\\u003e')
+}
+
+function htmlClose(
+  message: string,
+  ok: boolean,
+  reason: McpOauthCallbackReason,
+  serverId?: string
+): NextResponse {
+  const safeMessage = escapeHtml(message)
+  const title = ok ? 'Connected' : 'Connection failed'
+  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>
+    try { window.opener && window.opener.postMessage({ type: 'mcp-oauth', ok: ${ok ? 'true' : 'false'}, serverId: ${jsonLiteral(serverId)}, reason: ${jsonLiteral(reason)} }, window.location.origin) } catch (e) {}
+    setTimeout(function () { window.close() }, 800)
+  </script></body></html>`
+  return new NextResponse(body, {
+    headers: { 'Content-Type': 'text/html; charset=utf-8' },
+  })
+}
+
+export const GET = withRouteHandler(async (request: NextRequest) => {
+  const parsed = await parseRequest(mcpOauthCallbackContract, request, {})
+  if (!parsed.success) {
+    return htmlClose('Malformed authorization callback.', false, 'missing_params')
+  }
+  const { state, code, error: errorParam } = parsed.data.query
+
+  const initialRow = state ? await loadOauthRowByState(state).catch(() => null) : null
+  const stateRowServerId = initialRow?.mcpServerId
+
+  if (errorParam) {
+    logger.warn(`MCP OAuth callback received error: ${errorParam}`)
+    if (initialRow) await clearState(initialRow.id).catch(() => {})
+    return htmlClose(
+      `Authorization failed: ${errorParam}`,
+      false,
+      'provider_error',
+      stateRowServerId
+    )
+  }
+  if (!state || !code) {
+    return htmlClose(
+      'Missing state or code in callback URL.',
+      false,
+      'missing_params',
+      stateRowServerId
+    )
+  }
+
+  let serverId: string | undefined
+  try {
+    const session = await getSession()
+    if (!session?.user?.id) {
+      return htmlClose(
+        'You must be signed in to complete authorization.',
+        false,
+        'unauthenticated',
+        stateRowServerId
+      )
+    }
+
+    const row = initialRow
+    if (!row) {
+      return htmlClose('Invalid or expired authorization state.', false, 'invalid_state')
+    }
+    serverId = row.mcpServerId
+
+    if (session.user.id !== row.userId) {
+      return htmlClose(
+        'You must be signed in as the same user that initiated the flow.',
+        false,
+        'user_mismatch',
+        serverId
+      )
+    }
+
+    const [server] = await db
+      .select({ id: mcpServers.id, url: mcpServers.url, workspaceId: mcpServers.workspaceId })
+      .from(mcpServers)
+      .where(and(eq(mcpServers.id, row.mcpServerId), isNull(mcpServers.deletedAt)))
+      .limit(1)
+    if (!server || !server.url) {
+      return htmlClose('Server no longer exists.', false, 'server_gone', serverId)
+    }
+    if (server.workspaceId !== row.workspaceId) {
+      return htmlClose(
+        'Workspace mismatch on authorization callback.',
+        false,
+        'invalid_state',
+        serverId
+      )
+    }
+    try {
+      assertSafeOauthServerUrl(server.url)
+    } catch {
+      return htmlClose(
+        'MCP OAuth requires https (or http://localhost for development).',
+        false,
+        'insecure_url',
+        serverId
+      )
+    }
+
+    // Burn state before token exchange so a replayed callback cannot reuse it.
+    await clearState(row.id)
+
+    const preregistered = await loadPreregisteredClient(server.id)
+    const provider = new SimMcpOauthProvider({ row, preregistered })
+    let result: Awaited<ReturnType<typeof mcpAuth>>
+    try {
+      result = await mcpAuth(provider, {
+        serverUrl: server.url,
+        authorizationCode: code,
+      })
+    } catch (e) {
+      logger.error('Token exchange failed during MCP OAuth callback', e)
+      return htmlClose(
+        'Token exchange failed. Please try again.',
+        false,
+        'token_exchange_failed',
+        server.id
+      )
+    } finally {
+      await clearVerifier(row.id)
+    }
+
+    if (result !== 'AUTHORIZED') {
+      return htmlClose('Authorization did not complete.', false, 'token_exchange_failed', server.id)
+    }
+
+    try {
+      await mcpService.clearCache(server.workspaceId)
+      await mcpService.discoverServerTools(session.user.id, server.id, server.workspaceId)
+    } catch (e) {
+      logger.warn('Post-auth tools refresh failed', toError(e).message)
+    }
+
+    return htmlClose('Connected. You can close this window.', true, 'authorized', server.id)
+  } catch (error) {
+    logger.error('MCP OAuth callback failed', error)
+    return htmlClose('Authorization failed. Please try again.', false, 'unknown', serverId)
+  }
+})
diff --git a/apps/sim/app/api/mcp/oauth/start/route.test.ts b/apps/sim/app/api/mcp/oauth/start/route.test.ts
@@ -0,0 +1,137 @@
+/**
+ * @vitest-environment node
+ */
+import {
+  dbChainMock,
+  dbChainMockFns,
+  hybridAuthMock,
+  hybridAuthMockFns,
+  McpOauthRedirectRequiredMock,
+  mcpOauthMock,
+  mcpOauthMockFns,
+  permissionsMock,
+  permissionsMockFns,
+  resetDbChainMock,
+  schemaMock,
+} from '@sim/testing'
+import { NextRequest } from 'next/server'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+const { mockMcpAuth } = vi.hoisted(() => ({
+  mockMcpAuth: vi.fn(),
+}))
+
+vi.mock('@sim/db', () => dbChainMock)
+vi.mock('@sim/db/schema', () => schemaMock)
+vi.mock('drizzle-orm', () => ({
+  and: vi.fn(),
+  eq: vi.fn(),
+  isNull: vi.fn(),
+}))
+vi.mock('@modelcontextprotocol/sdk/client/auth.js', () => ({
+  auth: mockMcpAuth,
+}))
+vi.mock('@/lib/auth/hybrid', () => hybridAuthMock)
+vi.mock('@/lib/workspaces/permissions/utils', () => permissionsMock)
+vi.mock('@/lib/mcp/oauth', () => mcpOauthMock)
+
+import { GET } from './route'
+
+describe('MCP OAuth start route', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    resetDbChainMock()
+    hybridAuthMockFns.mockCheckSessionOrInternalAuth.mockResolvedValue({
+      success: true,
+      userId: 'user-2',
+      userName: 'User Two',
+      userEmail: 'user2@example.com',
+      authType: 'session',
+    })
+    permissionsMockFns.mockGetUserEntityPermissions.mockResolvedValue('write')
+    dbChainMockFns.limit.mockResolvedValue([
+      {
+        id: 'server-1',
+        name: 'Exa',
+        url: 'https://mcp.exa.ai/mcp',
+        workspaceId: 'workspace-1',
+        authType: 'oauth',
+        deletedAt: null,
+      },
+    ])
+    mcpOauthMockFns.mockGetOrCreateOauthRow.mockResolvedValue({
+      id: 'oauth-row-1',
+      mcpServerId: 'server-1',
+      userId: 'user-1',
+      workspaceId: 'workspace-1',
+      clientInformation: null,
+      tokens: null,
+      codeVerifier: null,
+      state: null,
+      stateCreatedAt: null,
+      updatedAt: new Date(),
+    })
+    mcpOauthMockFns.mockLoadPreregisteredClient.mockResolvedValue(undefined)
+    mockMcpAuth.mockRejectedValue(new McpOauthRedirectRequiredMock('https://mcp.exa.ai/authorize'))
+  })
+
+  it('requires workspace write permission via MCP auth middleware', async () => {
+    const request = new NextRequest(
+      'http://localhost:3000/api/mcp/oauth/start?workspaceId=workspace-1&serverId=server-1'
+    )
+
+    await GET(request)
+
+    expect(permissionsMockFns.mockGetUserEntityPermissions).toHaveBeenCalledWith(
+      'user-2',
+      'workspace',
+      'workspace-1'
+    )
+  })
+
+  it('uses a workspace-scoped OAuth row and stamps the latest authorizing user', async () => {
+    const request = new NextRequest(
+      'http://localhost:3000/api/mcp/oauth/start?workspaceId=workspace-1&serverId=server-1'
+    )
+
+    const response = await GET(request)
+    const body = await response.json()
+
+    expect(response.status).toBe(200)
+    expect(body).toEqual({
+      status: 'redirect',
+      authorizationUrl: 'https://mcp.exa.ai/authorize',
+    })
+    expect(mcpOauthMockFns.mockGetOrCreateOauthRow).toHaveBeenCalledWith({
+      mcpServerId: 'server-1',
+      userId: 'user-2',
+      workspaceId: 'workspace-1',
+    })
+    expect(mcpOauthMockFns.mockSetOauthRowUser).toHaveBeenCalledWith('oauth-row-1', 'user-2')
+  })
+
+  it('rejects a second user starting OAuth while another authorization is active', async () => {
+    mcpOauthMockFns.mockGetOrCreateOauthRow.mockResolvedValueOnce({
+      id: 'oauth-row-1',
+      mcpServerId: 'server-1',
+      userId: 'user-1',
+      workspaceId: 'workspace-1',
+      clientInformation: null,
+      tokens: null,
+      codeVerifier: null,
+      state: 'hashed-active-state',
+      stateCreatedAt: new Date(),
+      updatedAt: new Date(),
+    })
+    const request = new NextRequest(
+      'http://localhost:3000/api/mcp/oauth/start?workspaceId=workspace-1&serverId=server-1'
+    )
+
+    const response = await GET(request)
+    const body = await response.json()
+
+    expect(response.status).toBe(409)
+    expect(body.error).toBe('OAuth authorization already in progress for this server')
+    expect(mockMcpAuth).not.toHaveBeenCalled()
+  })
+})