Secure MCP servers with Access for SaaS

You can secure Model Context Protocol (MCP) servers ↗ by using Cloudflare Access as an OAuth Single Sign-On (SSO) provider.

This guide walks through how to deploy a remote MCP server on Cloudflare Workers that requires Cloudflare Access for authentication. When users connect to the MCP server using an MCP client, they will be prompted to log in to your identity provider and are only granted access if they pass your Access policies.

Prerequisites

Create a Zero Trust organization.
Configure One-time PIN or connect a third-party identity provider.

1. Deploy an example MCP server

To deploy our example MCP server ↗ to your Cloudflare account:

Dashboard
CLI

Select the following button to launch the quickstart flow:
Select the account that contains your Zero Trust organization.
On the Create an application page, configure the following fields:
- Git account: Select an existing account or connect a new GitHub or GitLab account.
- Create private Git repository: Choose whether the project repository should be public or private.
- Project name: mcp-server-cf-access
- Select KV namespace: Create new
- Name your KV namespace: OAUTH_KV
We will configure ACCESS_CLIENT_ID and the other secret values in a later step.
Select Create and deploy.

The MCP server will be deployed to your *.workers.dev subdomain at mcp-server-cf-access.<YOUR_SUBDOMAIN>.workers.dev. A new git repository will be set up on your GitHub or GitLab account for your MCP server, configured to automatically deploy to Cloudflare each time you push a change or merge a pull request to the main branch of the repository.

You can use the Wrangler CLI to create the MCP server on your local machine and deploy it to Cloudflare.

Open a terminal and clone our example project:
Terminal window
```
npm create cloudflare@latest -- mcp-server-cf-access --template=cloudflare/ai/demos/remote-mcp-cf-access
```
When asked if you want to deploy to Cloudflare, select No.
Go to the project directory:
Terminal window
```
cd mcp-server-cf-access
```
Create a Workers KV namespace to store the key. The binding name should be OAUTH_KV if you want to run the example as written.
Terminal window
```
npx wrangler kv namespace create "OAUTH_KV"
```
The command will output the binding name and KV namespace ID:
```
{
  "kv_namespaces": [
    {
      "binding": "OAUTH_KV",
      "id": "<YOUR_KV_NAMESPACE_ID>"
    }
  ]
}
```

Open wrangler.jsonc in an editor and insert your OAUTH_KV namespace ID:

"kv_namespaces": [
  {
    "binding": "OAUTH_KV",
    "id": "<YOUR_KV_NAMESPACE_ID>"
  }
],

You can now deploy the Worker to Cloudflare's global network:
Terminal window
```
npx wrangler deploy
```

The Worker will be deployed to your *.workers.dev subdomain at mcp-server-cf-access.<YOUR_SUBDOMAIN>.workers.dev.

In Cloudflare One ↗, go to Access controls > Applications.
Select Add an application.
Select SaaS.
In Application, enter a custom name (for example, MCP server) and select the textbox that appears below.
Select OIDC as the authentication protocol.
Select Add application.
In Redirect URLs, enter the authorization callback URL for your MCP server. The callback URL for our example MCP server is https://mcp-server-cf-access.<YOUR_SUBDOMAIN>.workers.dev/callback.
Copy the following values to input into our example MCP server. Other MCP servers may require different sets of input values.
- Client secret
- Client ID
- Token endpoint
- Authorization endpoint
- Key endpoint
(Optional) Under Advanced settings, turn on Refresh tokens if you want to reduce the number of times a user needs to log in to the identity provider.
Configure Access policies to define the users who can access the MCP server.
Save the application.

Make a POST request to the Access applications endpoint:

Required API token permissions

At least one of the following token permissions is required:

Access: Apps and Policies Write

curl "https://api.cloudflare.com/client/v4/accounts/$ACCOUNT_ID/access/apps" \
  --request POST \
  --header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \
  --json '{
    "name": "MCP server",
    "type": "saas",
    "saas_app": {
        "auth_type": "oidc",
        "redirect_uris": [
            "https://mcp-server-cf-access.<YOUR_SUBDOMAIN>.workers.dev/callback"
        ],
        "grant_type": [
            "authorization_code",
            "refresh_tokens"
        ],
        "refresh_token_options": {
            "lifetime": "90d"
        }
    },
    "policies": [
        "f174e90a-fafe-4643-bbbc-4a0ed4fc8415"
    ],
    "allowed_idps": []
  }'

Copy the client_id and client_secret returned in the response.
To determine the OAuth endpoint URLs for the SaaS application, refer to the generic OIDC documentation.

3. Configure your MCP server

Your MCP server needs to perform an OAuth 2.0 authorization flow to get an access_token from the SaaS app created in Step 1. When setting up the OAuth client on your MCP server, you will need to paste in the OAuth endpoints and credentials from the SaaS app.

To add OAuth endpoints and credentials to our example MCP server:

Dashboard
CLI

In the Cloudflare dashboard ↗, go to the Workers & Pages page.
Go to Workers & Pages
Select the mcp-server-cf-access Worker.
Go to Settings.
Under Variables and Secrets, update each secret with the corresponding value from your SaaS app:

Workers secret SaaS app field
ACCESS_CLIENT_ID Client ID
ACCESS_CLIENT_SECRET Client secret
ACCESS_TOKEN_URL Token endpoint
ACCESS_AUTHORIZATION_URL Authorization endpoint
ACCESS_JWKS_URL Key endpoint
For COOKIE_ENCRYPTION_KEY, you can use the following command to generate a random string:
Terminal window
```
openssl rand -hex 32
```
Enter the output of this command into COOKIE_ENCRYPTION_KEY.

Workers secret	SaaS app field
`ACCESS_CLIENT_ID`	Client ID
`ACCESS_CLIENT_SECRET`	Client secret
`ACCESS_TOKEN_URL`	Token endpoint
`ACCESS_AUTHORIZATION_URL`	Authorization endpoint
`ACCESS_JWKS_URL`	Key endpoint

Create the following Workers secrets:

wrangler secret put ACCESS_CLIENT_ID
wrangler secret put ACCESS_CLIENT_SECRET
wrangler secret put ACCESS_TOKEN_URL
wrangler secret put ACCESS_AUTHORIZATION_URL
wrangler secret put ACCESS_JWKS_URL

When prompted to enter a secret value, paste the corresponding values from your SaaS app:

Workers secret SaaS app field
ACCESS_CLIENT_ID Client ID
ACCESS_CLIENT_SECRET Client secret
ACCESS_TOKEN_URL Token endpoint
ACCESS_AUTHORIZATION_URL Authorization endpoint
ACCESS_JWKS_URL Key endpoint
Generate a random string for the cookie encryption key:
Terminal window
```
openssl rand -hex 32
```
Store the output of this command in a Workers secret:
Terminal window
```
wrangler secret put COOKIE_ENCRYPTION_KEY
```

Workers secret	SaaS app field
`ACCESS_CLIENT_ID`	Client ID
`ACCESS_CLIENT_SECRET`	Client secret
`ACCESS_TOKEN_URL`	Token endpoint
`ACCESS_AUTHORIZATION_URL`	Authorization endpoint
`ACCESS_JWKS_URL`	Key endpoint

4. Test the connection

You should now be able to connect to your MCP server using Workers AI Playground ↗, MCP inspector ↗, or other MCP clients that support remote MCP servers. The demo MCP server supports connections ↗ via either https://mcp-server-cf-access.<YOUR_SUBDOMAIN>.workers.dev/mcp or https://mcp-server-cf-access.<YOUR_SUBDOMAIN>.workers.dev/sse.

To test in Workers AI Playground:

Go to Workers AI Playground ↗.
Under MCP Servers, enter https://mcp-server-cf-access.<YOUR_SUBDOMAIN>.workers.dev/mcp for the MCP server URL.
Select Connect.
A popup window will appear requesting access to the MCP server. Select Approve.
Follow the prompts to log in to your identity provider.

Workers AI Playground will show a Connected status. The MCP server should successfully obtain an access_token from Cloudflare Access.