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