spring-web CORS requires X-Forwarded-Port [SPR-16262]

[spring-projects-issues]

simon Kitching opened SPR-16262 and commented

I am running a spring-boot app within Google AppEngine behind an IAP proxy which terminates https connections. The proxy sets X-Forwarded-Proto=https on requests, but does not set X-Forwarded-Port. The result is that the spring-web CORS filter rejects requests with "not same origin" even though the origin actually is the same.

This is made worse by the fact that the Chrome browser sends the "origin" header on many different request types, including all POST requests and all resources referenced from a css-file (eg fonts) - ie on requests which are NOT cross-origin.

While it may be argued that Google should add a header, this is a problem that may hit many users. It is also really really nasty to actually figure out the real cause of the problem..

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Affects: 4.3.12

Issue Links:

• UriComponentsBuilder#fromHttpRequest should consider RFC-7239 Forwarded headers [SPR-11856] #16475 UriComponentsBuilder#fromHttpRequest should consider RFC-7239 Forwarded headers
• UriComponentsBuilder's fromHttpRequest uses server port as host port when handling the Forwarded header [SPR-15504] #20063 UriComponentsBuilder's fromHttpRequest uses server port as host port when handling the Forwarded header
• Check scheme in WebUtils#isSameOrigin [SPR-16362] #20909 Check scheme in WebUtils#isSameOrigin

Referenced from: commits 9c7de23, c326e44, 1b3b058

Backported to: 4.3.14

[spring-projects-issues]

simon Kitching commented

Class UriComponentsBuilder has separate fields for port and scheme. Method UriComponentsBuilder.adaptFromForwardedHeaders checks for "X-Forwarded-*" headers and modifies those fields. However when X-Forwarded-Proto is present then ONLY field "scheme" is updated, not field "port". The result is that a request which has been forwarded by the Google IAP proxy, and thus has X-Forwarded-Proto but not X-Forwarded-Port, has the original "https" scheme but port 80.

Method WebUtils.isSameOrigin calls getPort() which returns port 80 for the incoming request, but deduces port 443 from the "origin" http header, and thus rejects the incoming request.

I think a good argument could be made for method adaptFromForwardedHeaders to set field port (in same way as WebUtils.getPort) when X-Forwarded-Proto is present.

At the very least, please add some suitable logging to indicate this problem - it has sucked up 2 days of my time tracking this down. In particular, this only occurs behind a proxy - local testing shows no problem.

[spring-projects-issues]

simon Kitching commented

As mentioned in spring-projects/spring-boot#10965, Traefik is another proxy which fails to set X-Forwarded-Port.

[spring-projects-issues]

simon Kitching commented

For anyone else looking for a solution for this problem, I have implemented a single-class workaround documented here: http://moi.vonos.net/java/spring-forward/
Basically, it provides a ServletFilter which sets header X-Forwarded-Port=443 if X-Forwarded-Proto="https", and solves the problem for me behind Google IAP.

[spring-projects-issues]

Sébastien Deleuze commented

I will shortly merge this pull-request after some remaining polish. Feel free to have a look.

[spring-projects-issues]

Sébastien Deleuze commented

Commits merged in both 4.3.x and master branches, with additional optimizations on master.