Broken parsing of HTTP headers

[abouvier]

The parsing of HTTP headers is broken for certain value of Accept-Encoding when Hefur is behind a reverse proxy.

Apache config:

<VirtualHost *:443>
        ServerName tracker.domain.com
        (...)
        <Location />
                ProxyPass http://localhost:6969/
                ProxyPassReverse http://localhost:6969/
                ProxyPreserveHost On
        </Location>
</VirtualHost>

Hefur is launched like this:
$ hefurd -torrent-dir /srv/tracker -bind-addr 127.0.0.1 -reverse-proxy-from 127.0.0.1 -reverse-proxy-header X-Forwarded-For

The problem arise here:

hefur/hefur/log-handler.cc

Lines 24 to 25 in 5136250

	auto headers = request.unparsedHeaders();
	auto header = headers.find(REVERSE_PROXY_HEADER);

With qBittorrent, Apache sends the following request to Hefur:

Host: tracker.domain.com
User-Agent: qBittorrent/4.3.9
Accept-Encoding: gzip
X-Forwarded-For: 42.42.42.42
(...)

request.unparsedHeaders() returns all headers and X-Forwarded-For is found.

With Transmission, Apache sends the following request to Hefur:

Host: tracker.domain.com
User-Agent: Transmission/3.00
Accept: */*
Accept-Encoding: deflate, gzip, br, zstd
X-Forwarded-For: 42.42.42.42
(...)

request.unparsedHeaders() returns only Accept: */*

If I remove Accept-Encoding from the request sent by Apache (with RequestHeader unset Accept-Encoding in <Location />), then the request is parsed correctly and the real IP is found, but Hefur crash soon after with:

hefurd[28911]: hefurd: hefur/address.cc:133: hefur::Address& hefur::Address::operator=(const sockaddr*): Assertion 'false' failed.

So an announce request from Transmission seems totally broken: the real IP is not found, the response is bad (wrong values of seeders/leechers) and Transmission try to announce again every 8 seconds in a loop.
Everything is working fine with qBittorrent.

OS: Arch Linux
Hefur: 1.0
Apache: 2.4.51
qBittorrent: 4.3.9
Transmission: 3.00

[abique]

Thank you very much!
I'll look into it soon.

[batkom]

I think the problem in https://github.com/abique/mimosa/blob/42c0041b570b55a24c606a7da79c70c9933c07d4/mimosa/http/request-parser.y#L98
abouvier, can you test it please?

--- request-parser.y	2021-02-01 20:32:00.000000000 +0300
+++ request-parser.y	2022-06-07 13:22:20.739899488 +0300
@@ -95,8 +95,8 @@
 kvs: kv kvs | /* epsilon */ ;
 
 kv:
-  KEY VALUE { rq.addHeader(*$1, *$2); delete $1; delete $2; }
-| KEY_ACCEPT_ENCODING accept_encodings
+  KEY_ACCEPT_ENCODING accept_encodings
+| KEY VALUE { rq.addHeader(*$1, *$2); delete $1; delete $2; }
 | KEY_CONNECTION VALUE_CONNECTION { rq.setKeepAlive($2); }
 | KEY_COOKIE cookies
 | KEY_CONTENT_LENGTH VAL64 { rq.setContentLength($2); }

[abique]

KEY_ACCEPT_ENCODING shows up first in the lexer, but does not hurt to move it down.
Then maybe I could move the KEY VALUE option at the end.

[abique]

I've added a unit test with your example, and updated mimosa.
@abouvier does it fixes it for you?
PS: sorry for the long delay...

[abouvier]

The new commit of mimosa submodule is non existent. Did you forget to push something on the mimosa repository?

[abique]

Super strange I get timeout to push and pull to mimosa...

[abique]

You can try again now.

[abouvier]

hefur now crashes immediately when I try to load https://tracker.domain.com/stat, with the same error:

hefurd: hefur/address.cc:133: hefur::Address& hefur::Address::operator=(const sockaddr*): Assertion 'false' failed.

[abique]

I've pushed some changes, that assertion wasn't correct.

[abouvier]

It's better. The client's public address is correctly registered in hefur, but the response sent by hefur to Transmission is still bogus, with nonsensical values. File sharing with other peers works though.

[abique]

Yeah something must have gone wrong, because it is a strange error to have a inet addr that isn't ipv4 or ipv6.
I'll have to take a deeper look I suppose.

[abouvier]

It may be because hefur and Transmission are on the same host?

[abique]

Still it should be using ipv4/6