Class: MCP::Client::HTTP::OAuthURLGuard

Inherits:
Object
  • Object
show all
Defined in:
lib/mcp/client/http.rb

Overview

Faraday request middleware that compares the outgoing request URL against the URL snapshotted at MCP::Client::HTTP#initialize time. Registered after the user's customizer so it sees env.url after any custom middleware has had a chance to rewrite it - closing the Faraday env.url = URI("https://attacker...") bypass that a plain client.url_prefix check would miss. The comparison includes the query string, so a middleware that rewrites env.url.query to a different tenant (e.g. ?tenant=evil) is rejected as well; otherwise the audience-binding check on the OAuth side could be bypassed at the send step.

Instance Method Summary collapse

Constructor Details

#initialize(app, expected_url:) ⇒ OAuthURLGuard

Returns a new instance of OAuthURLGuard.



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# File 'lib/mcp/client/http.rb', line 38

def initialize(app, expected_url:)
  @app = app
  @expected_url = expected_url
end

Instance Method Details

#call(env) ⇒ Object 



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# File 'lib/mcp/client/http.rb', line 43

def call(env)
  effective = MCP::Client::OAuth::Discovery.canonicalize_url(env.url.to_s)
  unless effective == @expected_url
    # Surface the *canonicalized* form (no userinfo, no fragment) so
    # credentials like `user:pass@` cannot leak into logs, stack
    # traces, or exception reporters.
    raise InsecureURLError,
      "Effective request URL #{effective.inspect} does not match the URL " \
        "validated at initialize time (#{@expected_url.inspect}); refusing to send a bearer token."
  end
  @app.call(env)
end