Function fileResourceHandler

mcp/server.go:850–877

fileResourceHandler returns a ReadResourceHandler that reads paths using dir as a base directory. It honors client roots and protects against path traversal attacks. The dir argument should be a filesystem path. It need not be absolute, but that is recommended to avoid a dependency on the current w

(dir string)

// are always caught. The SDK also protects against symlink-based attacks,
// where symlinks under dir lead out of the tree.
func fileResourceHandler(dir string) ResourceHandler {
	// Convert dir to an absolute path.
	dirFilepath, err := filepath.Abs(dir)
	if err != nil {
		panic(err)
	}
	return func(ctx context.Context, req *ReadResourceRequest) (_ *ReadResourceResult, err error) {
		defer util.Wrapf(&err, "reading resource %s", req.Params.URI)

		// TODO(#25): use a memoizing API here.
		rootRes, err := req.Session.ListRoots(ctx, nil)
		if err != nil {
			return nil, fmt.Errorf("listing roots: %w", err)
		}
		roots, err := fileRoots(rootRes.Roots)
		if err != nil {
			return nil, err
		}
		data, err := readFileResource(req.Params.URI, dirFilepath, roots)
		if err != nil {
			return nil, err
		}
		// TODO(jba): figure out mime type. Omit for now: Server.readResource will fill it in.
		return &ReadResourceResult{Contents: []*ResourceContents{
			{URI: req.Params.URI, Blob: data},
		}}, nil
	}
}

// ResourceUpdated sends a notification to all clients that have subscribed to the
// resource specified in params. This method is the primary way for a