When something doesn't work, look up here... and if it still doesn't work, report how what was suggested here went.
It's also worth reading how to ask questions before posting on the mailing list or opening an issue in GitHub.
In general, if something doesn't work, you'll want to run
sslh
with lots of logging, and the logging directly in
the terminal (Otherwise, logs are sent to syslog
, and
usually end up in /var/log/auth.log
). You will achieve
this by running sslh
in foreground with verbose:
sslh -v 1 -f -F myconfig.cfg
Higher values of verbose
produce more information. 1 is
usually sufficient. 2 will also print incoming packets used
for probing.
Usually this means sslh
is configured to forward a
protocol somewhere, but no service is listening on the
target address. Check your sslh
configuration, check the
corresponding server really is listening and running.
Finally, check the server is listening where you expect it
to:
netstat -lpt
Well, it's not yours (fault): a segfault is always a bug in the programme. Usually standard use cases are well tested, so it may be related to something unusual in your configuration, or even something wrong, but it should still never result in a segfault.
Thankfully, when they are deterministic, segfaults are usually fairly easy to fix if you're willing to run a few diagnostics to help the developer.
First, make sure you have debug symbols:
$ file sslh-select
sslh-select: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=a758ac75ff11f1ace577705b4d6627e301940b59, with debug_info, not stripped
Note with debug_info, not stripped
at the end. If you
don't have that, your distribution stripped the binary: you
will need to get the source code and compile it yourself
(that way, you will also get the latest version).
Install valgrind
and run sslh
under it:
valgrind --leak-check=full ./sslh-fork -v 2 -f -F yourconfig.cfg
Report the full output to the mailing list or github.
Valgrind is very powerful and gives precise hints of what is
wrong and why. For example on sslh
issue
(#273)[yrutschle#273]:
sudo valgrind --leak-check=full ./sslh-fork -v 2 -f -F /etc/sslh.cfg
==20037== Memcheck, a memory error detector
==20037== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==20037== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==20037== Command: ./sslh-fork -v 2 -f -F /etc/sslh.cfg
==20037==
sslh-fork v1.21b-1-g2c93a01-dirty started
--20037-- WARNING: unhandled arm-linux syscall: 403
--20037-- You may be able to write your own handler.
--20037-- Read the file README_MISSING_SYSCALL_OR_IOCTL.
--20037-- Nevertheless we consider this a bug. Please report
--20037-- it at http://valgrind.org/support/bug_reports.html.
==20040== Conditional jump or move depends on uninitialised value(s)
==20040== at 0x112A3C: parse_tls_header (tls.c:162)
==20040== by 0x111CEF: is_tls_protocol (probe.c:214)
==20040== by 0x11239F: probe_client_protocol (probe.c:366)
==20040== by 0x10A8F7: start_shoveler (sslh-fork.c:98)
==20040== by 0x10AE9B: main_loop (sslh-fork.c:200)
==20040== by 0x1114FB: main (sslh-main.c:322)
==20040==
Here we see that something wrong is happening at tls.c
line 162, and it's linked to an uninitialised value.
Virtual hosting refers to having several domain names behind
a single IP address. All Web servers handle this, but
sometimes it can be useful to do it with sslh
.
For TLS, this is done very simply using Server Name
Indication, SNI for short, which is a TLS extension whereby
the client indicates the name of the server it wishes to
connect to. This can be a very powerful way to separate
several TLS-based services hosted behind the same port:
simply name each service with its own hostname. For example,
we could define mail.rutschle.net
, im.rutschle.net
,
www.rutschle.net
, all of which point to the same IP
address. sslh
uses the sni_hostnames
setting of the
TLS probe to do this, e.g.:
protocols: (
{ name: "tls";
host: "localhost";
port: "993";
sni_hostnames: [ "mail.rutschle.net" ];
},
{ name: "tls";
host: "localhost";
port: "xmpp-client";
sni_hostnames: [ "im.rutschle.net" ];
},
{ name: "tls";
host: "localhost";
port: "4443";
sni_hostnames: [ "www.rutschle.net" ];
}
);
If you wish to serve several Web domains over HTTP through
sslh
, you can do this simply by using regular expressions
on the Host specification part of the HTTP query.
The following example forwards connections to host_A.acme
to 192.168.0.2, and connections to host_B.acme
to
192.168.0.3.
protocols: (
{ name: "regex";
host: "192.168.0.2";
port: "80";
regex_patterns:
["^(GET|POST|PUT|OPTIONS|DELETE|HEADER) [^ ]* HTTP/[0-9.]*[\r\n]*Host: host_A.acme"] },
{ name: "regex";
host: "192.168.0.3";
port: "80";
regex_patterns:
["^(GET|POST|PUT|OPTIONS|DELETE|HEADER) [^ ]* HTTP/[0-9.]*[\r\n]*Host: host_B.acme"] }
);