92 lines
3.3 KiB
PHP
92 lines
3.3 KiB
PHP
 
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<?php
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namespace TinkerTickets\Mcp\Auth;
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use Psr\Http\Message\ResponseFactoryInterface;
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use Psr\Http\Message\ResponseInterface;
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use Psr\Http\Message\ServerRequestInterface;
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use Psr\Http\Server\MiddlewareInterface;
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use Psr\Http\Server\RequestHandlerInterface;
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use TinkerTickets\Mcp\ToolCatalog;
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/**
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* Per-operation scope enforcement, before anything is dispatched.
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*
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* - Lifecycle messages (initialize, ping, notifications/*, server/discover)
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* need only a valid token.
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* - tools/call on a write tool needs tickets:write.
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* - Everything else (tools/list, read tools, ...) needs tickets:read, which
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* tickets:write implies.
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*
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* Denials use the MCP spec's step-up challenge: HTTP 403 +
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* WWW-Authenticate: Bearer error="insufficient_scope", listing every scope
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* the request needs in one go.
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*/
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final class ToolScopeMiddleware implements MiddlewareInterface
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{
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private const LIFECYCLE_METHODS = ['initialize', 'ping', 'server/discover'];
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public function __construct(
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private readonly ResponseFactoryInterface $responseFactory,
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private readonly string $resourceMetadataUrl,
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) {
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}
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public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
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{
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if ($request->getMethod() !== 'POST') {
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return $handler->handle($request);
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}
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$payload = json_decode((string)$request->getBody(), true);
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$request->getBody()->rewind();
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if (!is_array($payload)) {
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return $handler->handle($request); // the SDK answers malformed JSON-RPC itself
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}
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$messages = array_is_list($payload) ? $payload : [$payload];
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$needWrite = false;
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$needRead = false;
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foreach ($messages as $message) {
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if (!is_array($message) || !is_string($message['method'] ?? null)) {
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continue; // responses to server->client requests carry no method
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}
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$method = $message['method'];
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if (in_array($method, self::LIFECYCLE_METHODS, true) || str_starts_with($method, 'notifications/')) {
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continue;
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}
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if ($method === 'tools/call' && ToolCatalog::isWriteTool((string)($message['params']['name'] ?? ''))) {
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$needWrite = true;
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} else {
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$needRead = true;
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}
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}
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$scopes = $request->getAttribute('oauth.scopes') ?? [];
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if ($needWrite && !McpIdentity::canWrite($scopes)) {
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return $this->insufficient(McpIdentity::SCOPE_WRITE, 'This operation requires the tickets:write scope.');
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}
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if ($needRead && !McpIdentity::canRead($scopes)) {
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return $this->insufficient(
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$needWrite ? McpIdentity::SCOPE_WRITE : McpIdentity::SCOPE_READ,
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'This operation requires the tickets:read scope.'
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);
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}
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return $handler->handle($request);
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}
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private function insufficient(string $scope, string $description): ResponseInterface
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{
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return $this->responseFactory->createResponse(403)->withHeader(
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'WWW-Authenticate',
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sprintf(
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'Bearer error="insufficient_scope", scope="%s", resource_metadata="%s", error_description="%s"',
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$scope,
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$this->resourceMetadataUrl,
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$description
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)
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);
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}
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}
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