Lighttpd

Is there a way to remove these headers?

No, not currently. However, you also have not established that this is a problem. You're guessing.

Also, the information in those headers is consistent and seemingly correct for
https://www.jenkins.io/doc/book/system-administration/reverse-proxy-configuration-troubleshooting/
As that page does not mention the Forwarded header, have you tried commenting out proxy.forwarded from your lighttpd config?

but Jenkins keeps showing a message telling me there is a problem in the reverse proxy configuration

How about sharing more concrete log messages?

This should be removed from your lighttpd.conf for jenkins.example.com:
setenv.set-request-header = ( "X-Host" => "", "X-Forwarded-Host" => "" )
Those headers are generated by lighttpd mod_proxy.

If jenkins is not properly using the headers added by lighttpd mod_proxy, then you might try adding a configuration using proxy.header
proxy.header = ("map-host-response" => ("-" => "-"), "https-remap" => "enable")
If Jenkins uses websockets then you need to enable that in proxy.header by adding , "upgrade" => "enable" inside the above parens for proxy.header

Hi gstrauss,

I was trying to remove the headers because they are the extra ones in comparison with ones from nginx, this is why I was using these config below:

What I understood of mod setenv page, particularly this phrase: "Set a blank value to remove request header or remove response header."

My line of thought was the emulation of nginx headers because they are working

I added this configuration proxy.header = ("map-host-response" => ("-" => "-"), "https-remap" => "enable") with and without the "upgrade" => "enable" but the result is the same.

I cannot find logs about this proxy behavior in Jenkins, but there is curl with a "Referrer Page" information we use to test, and maybe this can give some light. It should return a 200, but in Lighttpd is returning a 404. The output is weird here in the post, so I will attach these logs as files.

Thanks,

It looks like jenkins is encoding https:// in the URI with "%2F%2F", and lighttpd default normalization may normalize it to a single "/"
Try this:

server.http-parseopts += ( "url-path-2f-decode" => "disable" )
server.modules += ( "mod_proxy" )
$HTTP["host"] == "jenkins.example.com" {
        proxy.balance = "hash" 
        proxy.server  = ( "" => ( ( "host" => "127.0.0.1", "port" => "8080" ) ) )
        #proxy.forwarded = ( "for" => 1, "proto" => 1, "host" => 0, "by" => 0, "remote_user" => 0 )
}

gstrauss, you are a genius, it worked!

That url encoding in the curl response was invisible to my eyes.

I never paid attention to these configurations before, but there is a clear explanation in my default config file from Debian (I changed the configuration in this file):

# strict parsing and normalization of URL for consistency and security
# https://redmine.lighttpd.net/projects/lighttpd/wiki/Server_http-parseoptsDetails
# (might need to explicitly set "url-path-2f-decode" = "disable" 
#  if a specific application is encoding URLs inside url-path)
server.http-parseopts = (
  "header-strict"           => "enable",# default
  "host-strict"             => "enable",# default
  "host-normalize"          => "enable",# default
  "url-normalize-unreserved"=> "enable",# recommended highly
  "url-normalize-required"  => "enable",# recommended
  "url-ctrls-reject"        => "enable",# recommended
  "url-path-2f-decode"      => "disable",# recommended highly (unless breaks app, ex: Jenkins)
 #"url-path-2f-reject"      => "enable",
  "url-path-dotseg-remove"  => "enable",# recommended highly (unless breaks app)
 #"url-path-dotseg-reject"  => "enable",
 #"url-query-20-plus"       => "enable",# consistency in query string
)

I will try to add the lighttpd configuration in Jenkins examples page.

Thank you!

Best,