HAProxy with SNI and different SSL Settings

Question

I have HAProxy for my two sites, one of them public and one private.

www.mysite.com private.mysite.com

Atm, I'm using haproxy like this:

frontend mysite_https
  bind *.443 ssl crt /etc/mycert.pem ca-file /etc/myca.pem verify optional no-sslv3
  mode http
  acl domain_www     hdr_beg(host) -i www.
  acl domain_private hdr_beg(host) -i private.
  acl path_ghost     path_beg         /ghost/
  acl clientcert     ssl_c_used

  redirect location https://www.example.com if path_ghost !clientcert
  redirect location https://www.example.com if !domain_www !clientcert

  use_backend bknd_private if domain_private
  use_backend bknd_www     if domain_www

  default_backend bknd_www

What this should do is ask for a client certificate (optionally) and proceed. If the domain is not www.example.com and the visitor cannot provide the right certificate or the path is /ghost/ and the visitor cannot provide the right certificate, it should be redirected to https://www.example.com

So far, this works fine. However, I got complaints by Mac users browsing my site with Safari that they keep getting asked for the certificate when there browsing on https://www.example.com/ whereas for example Firefox only asks when browsing https://private.example.com/ or https://www.example.com/ghost/.

Appearently that's just how Safari works so I can't fix that. My idea was to use SNI to divide between different frontends

frontend mysite_https
  bind *.443 ssl crt /etc/mycert.pem no-sslv3

frontend private_https
  bind *.443 ssl crt /etc/mycert.pem ca-file /etc/myca.pem verify optional no-sslv3

Of course that doesn't work because

a. I can't have two frontends listening on port 443 with only one public IP b. I haven't found a way yet to say "use_frontend if domain_www" or something like that. (Only use_backend or use-server)

I also tried doing it with three haproxy servers

frontend haproxy-sni
bind *:443 ssl crt /etc/mycert.pem no-sslv3
mode tcp

tcp-request inspect-delay 5s
tcp-request content accept if { req.ssl_hello_type 1 }

acl domain_www ssl_fc_sni_end -i www.example.com

use-server server1 haproxy-private.lan  if !domain_www
use-server server2 haproxy-public.lan   if domain_www

This works, the problem here however is that haproxy-private asks for the client certificate, but the request doesn't reach the browser. Somehow haproxy-sni drops the request.

Also, I now have three haproxy servers which is not desirable (although a possible option if I can't find a better solution).

Preferably I would like something like this (made up.. don't know the real options)

frontend mysite_https
  bind *.443 ssl crt /etc/mycert.pem no-sslv3
  mode http

  acl domain_www     hdr_beg(host) -i www.
  acl domain_private hdr_beg(host) -i private.
  acl path_ghost     path_beg         /ghost/

  ssl_options ca-file /etc/myca.pem verify optional if !www_domain          # made up!
  ssl_options ca-file /etc/myca.pem verify optional if !path_ghost          # made up!

  acl clientcert     ssl_c_used

  redirect location https://www.example.com if path_ghost !clientcert
  redirect location https://www.example.com if !domain_www !clientcert
  ...

I hope someone can help me with this...

Answer 1

I found a solution to this problem, that doesn't require additional servers or services. I'm not entirely sure if this doesn't spawn new problems though. For me it seems to work right now.

The way I did it, was to create a frontend for each domain that required different ssl settings. I then set the bind option of those frontends to high ports (these are not reachable from public!).

I created another frontend listening on port :443 to divide traffic based on SNI, and set the backend servers to 127.0.0.1:high-port.

This way, I created sort of a loop in haproxy

[incoming]->[haproxy:443]->[haproxy:7000]->[www.intern.lan]
[incoming]->[haproxy:443]->[haproxy:8000]->[private.intern.lan]

Here is the config part.

frontend frnd_snipt                                             # Frontend_SNI-PassThrough (snipt)
  bind *:443                                                    # Do not use bind *:8443 ssl crt etc....!
  option tcplog
  mode tcp 

  tcp-request inspect-delay 5s
  tcp-request content accept if { req_ssl_hello_type 1 } 

  acl subdomain_is_www   req_ssl_sni -i www.example.com
  acl subdomain_is_www   req_ssl_sni -i example.com
  acl subdomain_is_private req_ssl_sni -i private.example.com

  use_backend bknd_snipt_private if subdomain_is_private
  use_backend bknd_snipt_www  if subdomain_is_www

backend bknd_snipt_www
  mode tcp                                              # tcp mode must match the frontend mode - already set as default in [global]
  server snipt-www 127.0.0.1:7000                       # run without "check", otherwise haproxy checks itself all the time!

backend bknd_snipt_private
  mode tcp     
  server snipt-private 127.0.0.1:8000                   # also, don't add "ssl" when in tcp mode. "ssl" is an http mode option (result in "NO-SRV" when set in tcp)

##### NORMAL HAPROXY PART #####
frontend www_example_com                                # this frontend can be in tcp or http mode...
  bind *:7000 ssl crt /etc/mycert.pem no-sslv3          # www. frontend with normal https
  mode http
  option httplog


frontend private_example_com
  bind *:8000 ssl crt /etc/mycert.pem ca-file /etc/myca.pem verify optional no-sslv3        # private. frontend with client certificate request.
  mode http
  option httplog
  ... # whatever you have in your frontend

If anyone has thoughts on this, or any idea why this could be a bad idea please let me know. It works, but I'm wondering why use_frontend isn't an option. Maybe because it's something that shouldn't be done for whatever reasons.

Answer 2

recent versions of haproxy support a setting called crt-list which allows you to specify different TLS settings based on the matched certificate

you can use it like this:

haproxy.conf:

frontend https
    mode http
    bind *:443 ssl crt-list /etc/haproxy/crt-list.conf ca-file ca.pem

    use_backend test if { ssl_fc_sni -i test.area.example.org }
    use_backend private if { ssl_fc_sni -i private.example.org }
    default_backend www

crt-list.conf:

www.pem [verify none]
www.pem [verify required] *.area.example.org
private.pem [verify required]

more info: https://cbonte.github.io/haproxy-dconv/1.9/configuration.html#5.1-crt-list

note on security: always match your (sensitive) hostnames against SNI ssl_fc_sni, not the HTTP hostname. Otherwise an attacker could possibly bypass your client cert auth by sending the TLS SNI of www.example.org but set the HTTP hostname to private.example.org!