Remote Wiz MCP OAuth2 configuration returns 404 / “Unexpected end of JSON input”

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Summary

The issue at hand is an OAuth2 configuration problem with Wiz as a remote MCP server using Model Context Protocol. The error message indicates an HTTP 404 with an “Unexpected end of JSON input” error, suggesting a problem with the OAuth error response. The MCP configuration used is mostly correct, but there might be an issue with the token request encoding, headers, or auth fields.

Root Cause

The root cause of this issue can be attributed to several factors, including:

  • Incorrect OAuth2 token request: The request might not be formatted correctly, leading to an invalid response.
  • Missing or incorrect headers: The Content-Type header might not be set correctly, causing the server to misinterpret the request.
  • Invalid auth fields: The client_id, client_secret, or audience might be incorrect or not properly formatted.

Why This Happens in Real Systems

This issue can occur in real systems due to:

  • Misconfiguration: Human error can lead to incorrect configuration of the MCP server or OAuth2 settings.
  • Version incompatibility: Different versions of the MCP server or OAuth2 libraries might have different requirements or behaviors.
  • Network issues: Problems with the network connection can cause errors in the OAuth2 token request or response.

Real-World Impact

The impact of this issue can be significant, including:

  • Failed authentication: Users might not be able to authenticate with the MCP server, leading to access denied errors.
  • System downtime: The issue can cause the entire system to become unavailable, leading to downtime and lost productivity.
  • Security risks: If the OAuth2 configuration is not properly secured, it can lead to security vulnerabilities and data breaches.

Example or Code

import requests

# Set the OAuth2 token request parameters
token_url = "https://auth.app.wiz.io/oauth/token"
client_id = ""
client_secret = ""
audience = "wiz-api"
grant_type = "client_credentials"

# Set the headers and data for the token request
headers = {"Content-Type": "application/x-www-form-urlencoded"}
data = f"grant_type={grant_type}&client_id={client_id}&client_secret={client_secret}&audience={audience}"

# Send the token request
response = requests.post(token_url, headers=headers, data=data)

# Check if the response was successful
if response.status_code == 200:
    # Get the access token from the response
    access_token = response.json()["access_token"]
    # Use the access token to make a GraphQL query
    graphql_url = "https://api.us63.app.wiz.io/graphql"
    headers = {"Authorization": f"Bearer {access_token}"}
    response = requests.post(graphql_url, headers=headers, json={"query": "projects"})
    # Check if the response was successful
    if response.status_code == 200:
        print("GraphQL query successful")
    else:
        print("GraphQL query failed")
else:
    print("OAuth2 token request failed")

How Senior Engineers Fix It

Senior engineers can fix this issue by:

  • Verifying the MCP configuration: Double-checking the MCP server configuration and OAuth2 settings to ensure they are correct.
  • Checking the network connection: Verifying that the network connection is stable and not causing any issues with the OAuth2 token request or response.
  • Testing the OAuth2 token request: Using tools like curl or Postman to test the OAuth2 token request and verify that it is working correctly.
  • Reviewing the OAuth2 documentation: Checking the OAuth2 documentation to ensure that the token request is formatted correctly and that all required headers and auth fields are included.

Why Juniors Miss It

Junior engineers might miss this issue due to:

  • Lack of experience: Limited experience with OAuth2 and MCP servers can make it difficult to identify and troubleshoot the issue.
  • Insufficient knowledge: Not being familiar with the OAuth2 protocol and MCP server configuration can lead to mistakes and misconfigurations.
  • Inadequate testing: Not thoroughly testing the OAuth2 token request and MCP server configuration can cause issues to go unnoticed.

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