feature: add nonceless/tokenless CSRF protection Add tokenless CSRF protection following: https://words.filippo.io/csrf/ Must be enabled using use_tokenless_csrf_protection in config.ini. By default it's off. If enabled the older csrf_* settings are ignored. The allowed_api_origins setting is still used for Origin comparisons. This should also improve performance as a nonce isn't required so generating random nonce and saving it to the otks database is eliminated. doc/admin_guide.txt, doc/reference.txt doc/upgrading.txt doc updates. roundup/configuration.py add use_tokenless_csrf_protection setting. move allowed_api_origins directly after use_tokenless_csrf_protection and before the older csrf_* settings. It's used by both of them. Rewrite description of allowed_api_origins as its applied to all URLs with tokenless protection, not just API URLs. roundup/anypy/urllib_.py import urlsplit, it is used in new code. urlparse() is less efficient and splits params out of the path component. Since Roundup doesn't require that params be split from the path. I expect future patch will replace urlparse() with urlsplit() globally and not need urlparse(). roundup/cgi/client.py add handle_csrf_tokenless() and call from handle_csrf() if use_tokenless_csrf_protection is enabled. refactor code that expires csrf tokens when used with the wrong methods (i.e. GET) into expire_exposed_keys(). Call same from handle_csrf and handle_csrf_tokenless. Also improve logging if this happens including both Referer and Origin headers if available. Arguably we dont care about CSRF tokens exposed via GET/HEAD/OPTIONS in the tokenless case, but this cleans them up in case the admin has to switch back. At some future date we can delete all the nonce based CSRF from 2018. Update handle_csrf() docstring about calling/returning handle_csrf_tokenless() when enabled. Call expire_exposed_keys(method) if token is supplied with wrong method. roundup/cgi/templating.py disable nonce generation/save and always return "0" when use_tokenless_csrf_protection enabled.