We're accumulating a significant number of bugs related to cross-linking between the content and the CGI not being as relative as we would like. This is an attempt to design a solution for them all in a unified way, rather than solving one bug at the cost of exacerbating another. --[[smcv]] # Terminology * Absolute: starts with a scheme, like `http://example.com/ikiwiki.cgi`, `https://www.example.org/` * Protocol-relative: starts with `//` like `//example.com/ikiwiki.cgi` * Host-relative: starts with `/` like `/ikiwiki.cgi` * Relative: starts with neither `/` nor a scheme, like `../ikiwiki.cgi` # What we need * Static content must be able to link to other static content * Static content must be able to link to the CGI * CGI-generated content must be able to link to arbitrary static content (it is sufficient for it to be able to link to the "root" of the `destdir`) * CGI-generated content must be able to link to the CGI # Constraints * URIs in RSS feeds must be absolute, because feed readers do not have any consistent semantics for the base of relative links * If we have a `` then HTML 4.01 says it must be absolute, although HTML 5 does relax this by defining semantics for a relative `` - it is interpreted relative to the "fallback base URL" which is the URL of the page being viewed ([[bugs/trouble_with_base_in_search]], [[bugs/preview_base_url_should_be_absolute]]) * It is currently possible for the static content and the CGI to be on different domains, e.g. `www.example.com` vs. `cgi.example.com`; this should be preserved * It is currently possible to serve static content "mostly over HTTP" (i.e. advertise a http URI to readers, and use a http URI in RSS feeds etc.) but use HTTPS for the CGI * If the static content is served over HTTPS, it must refer to other static content and the CGI via HTTPS (to avoid mixed content, which is a vulnerability); this may be either absolute, protocol-relative, host-relative or relative * If the CGI is served over HTTPS, it must refer to static content and the CGI via HTTPS; again, this may be either either absolute, protocol-relative, host-relative or relative ([[todo/Protocol_relative_urls_for_stylesheet_linking]]) * Because reverse proxies and `w3mmode` exist, it must be possible to configure ikiwiki to not believe the `HTTPS`, etc., CGI variables, and force a particular scheme or host ([[bugs/W3MMode_still_uses_http:__47____47__localhost__63__]], [[forum/Using_reverse_proxy__59___base_URL_is_http_instead_of_https]], [[forum/Dot_CGI_pointing_to_localhost._What_happened__63__]]) * For relative links in page-previews to work correctly without having to have global state or thread state through every use of `htmllink` etc., `cgitemplate` needs to make links in the page body work as if we were on the page being previewed. # "Would be nice" * In general, the more relative the better * [[schmonz]] wants to direct all CGI pageviews to https even if the visitor comes from http (but this can be done at the webserver level by making http://example.com/ikiwiki.cgi a redirect to https://example.com/ikiwiki.cgi, so is not necessarily mandatory) * [[smcv]] has some sites that have non-CA-cartel-approved certificates, with a limited number of editors who can be taught to add SSL policy exceptions and log in via https; anonymous/read-only actions like `do=goto` should not go via HTTPS, since random readers would get scary SSL warnings ([[todo/want_to_avoid_ikiwiki_using_http_or_https_in_urls_to_allow_serving_both]], [[forum/CGI_script_and_HTTPS]]) * It would be nice if the CGI did not need to use a `` so that we could use host-relative URI references (`/sandbox/`) or scheme-relative URI references (`//static.example.com/sandbox/`) (see [[bugs/trouble_with_base_in_search]]) As a consequence of the "no mixed content" constraint, I think we can make some assumptions: * if the `cgiurl` is http but the CGI discovers at runtime that it has been reached via https, we can assume that the https equivalent, or a host- or protocol-relative URI reference to itself, would work; * if the `url` is http but the CGI discovers at runtime that it has been reached via https, we can assume that the https equivalent of the `url` would work In other words, best-practice would be to list your `url` and `cgiurl` in the setup file as http if you intend that they will most commonly be accessed via http (e.g. the "my cert is not CA-cartel approved" use-case), or as https if you intend to force accesses into being via https (the "my wiki is secret" use-case).