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I have a host machine with several lxc containers. I am trying to give ssh access to containers directly based on domain names. For this I have tried setting up HAProxy. Could achieve this easily with ACLs in http mode. When I try the same with tcp mode for ssh based on acls, I am not able to achieve giving ssh access to containers directly. Following is the snippet I am using in the haproxy.cfg.

listen SSHD :2200
    mode tcp
    acl is_apple hdr_dom i apple
    acl is_orange hdr_dom -i orange
    use_backend apple if is_apple
    use_backend orange if is_orange

backend apple
    mode tcp
    server apple 10.0.3.221:22

backend orange
    mode tcp
    server orange 10.0.3.222:22

Where apple.myhost.com and orange.myhost.com are the domain names for reaching each of the containers. HTTP proxying works fine with these acls but I am facing problem with SSH traffic.

I am getting the following error.

ssh_exchange_identification: Connection closed by remote host

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4 Answers 4

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10

I am using an HAproxy instance running on pfSense for exactly that purpose you were looking for.

I wrote a detailed description here: https://julian.pawlowski.me/geeking-out-with-haproxy-on-pfsense-the-ultimate/

I'm going even further with this setup: Port 443 is being shared for SSH, SSL/TLS and OpenVPN traffic while SSH is being protected using a X.509 client certificate:

  • normal HTTPS traffic (acting as normal reverse proxy for securing web traffic)
  • normal HTTPS traffic with X509 user certificate authentication
  • OpenVPN dial-in traffic
  • TLS-tunneled SSH traffic including X509 user certificate authentication (SSLH Gateway)

This also protects against port scans to SSH entry points. Furthermore it can help with IPv4-to-IPv6 (and vice versa) transition, flexible collaboration and homeoffice solutions for admins, etc pp.

I know there is this shiny litte tool SSLH out there but this solution is much more flexible due to the power of HAproxy.

This is a haproxy.cfg file created by pfSense based on my blog post for your reference:

global
    maxconn         2000
    stats socket /tmp/haproxy.socket level admin
    uid         80
    gid         80
    nbproc          1
    chroot          /tmp/haproxy_chroot
    daemon
    tune.ssl.default-dh-param   2048
    # Modern browser compatibility only as mentioned here:
    # https://wiki.mozilla.org/Security/Server_Side_TLS
    ssl-default-bind-ciphers ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-DSS-AES128-GCM-SHA256:kEDH+AESGCM:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-DSS-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-DSS-AES256-SHA:DHE-RSA-AES256-SHA:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!3DES:!MD5:!PSK

    # Time-to-first-Byte (TTFB) value needs to be optimized based on
    # the actual public certificate chain
    # see https://www.igvita.com/2013/10/24/optimizing-tls-record-size-and-buffering-latency/
    tune.ssl.maxrecord 1370

listen HAProxyLocalStats
    bind 127.0.0.1:2200 name localstats
    mode http
    stats enable
    stats admin if TRUE
    stats uri /haproxy_stats.php?haproxystats=1
    timeout client 5000
    timeout connect 5000
    timeout server 5000

frontend HTTP_redirect
    bind            0.0.0.0:80 name 0.0.0.0:80   
    mode            http
    log         global
    option          http-keep-alive
    timeout client      30000
    default_backend     _ssl-redirect_http_ipvANY

frontend LAN_HTTPS
    bind            10.108.2.1:443 name 10.108.2.1:443 ssl no-sslv3 no-tls-tickets no-tlsv10 no-tlsv11 crt /var/etc/haproxy/LAN_HTTPS.pem  
    mode            http
    log         global
    option          http-keep-alive
    option          forwardfor
    acl https ssl_fc
    reqadd X-Forwarded-Proto:\ http if !https
    reqadd X-Forwarded-Proto:\ https if https
    timeout client      30000
    # Remove headers that expose security-sensitive information.
    rspidel ^Server:.*$
    rspidel ^X-Powered-By:.*$
    rspidel ^X-AspNet-Version:.*$
    default_backend     gwsch01_http_ipvANY

frontend WAN_443-merged
    bind            178.26.150.88:443 name 178.26.150.88:443   
    mode            tcp
    log         global
    timeout client      7200000
    tcp-request inspect-delay 5s

    # block SSLv3 as early as possible
    acl sslv3 req.ssl_ver 3
    tcp-request content reject if sslv3
    tcp-request content accept if { req.ssl_hello_type 1 } or !{ req.ssl_hello_type 1 }
    acl         aclusr_custom_req.ssl_hello_type_201    req.ssl_hello_type 1
    acl         aclusr_custom_req.ssl_sni_20-m_20end_20-i_20.ssh.example.com    req.ssl_sni -m end -i .ssh.example.com
    acl         aclusr_custom_req.ssl_sni_20-m_20end_20-i_20.vpn.example.com    req.ssl_sni -m end -i .vpn.example.com
    acl         aclusr_custom_req.len_200   req.len 0
    use_backend     _WAN_HTTPS_tcp_ipvANY if aclusr_custom_req.ssl_hello_type_201 !aclusr_custom_req.ssl_sni_20-m_20end_20-i_20.ssh.example.com !aclusr_custom_req.ssl_sni_20-m_20end_20-i_20.vpn.example.com 
    use_backend     _WAN_HTTPS_auth_tcp_ipvANY if aclusr_custom_req.ssl_hello_type_201 aclusr_custom_req.ssl_sni_20-m_20end_20-i_20.vpn.example.com 
    use_backend     _openvpn_tcp_ipvANY if aclusr_custom_req.len_200 aclusr_custom_req.ssl_hello_type_201 
    use_backend     _WAN_SSLH_tcp_ipvANY if aclusr_custom_req.ssl_hello_type_201 aclusr_custom_req.ssl_sni_20-m_20end_20-i_20.ssh.example.com 
    default_backend     _none_tcp_ipvANY

frontend WAN_HTTPS
    bind            127.0.0.1:2043 name 127.0.0.1:2043 ssl no-sslv3 no-tls-tickets no-tlsv10 no-tlsv11 crt /var/etc/haproxy/WAN_HTTPS.pem  accept-proxy npn http/1.1
    mode            http
    log         global
    option          http-keep-alive
    option          forwardfor
    acl https ssl_fc
    reqadd X-Forwarded-Proto:\ http if !https
    reqadd X-Forwarded-Proto:\ https if https
    timeout client      7200000
    # Remove headers that expose security-sensitive information.
    rspidel ^Server:.*$
    rspidel ^X-Powered-By:.*$
    rspidel ^X-AspNet-Version:.*$
    default_backend     _none_http_ipvANY

frontend WAN_HTTPS_auth-merged
    bind            127.0.0.1:2044 name 127.0.0.1:2044 ssl no-sslv3 no-tls-tickets no-tlsv10 no-tlsv11 crt /var/etc/haproxy/WAN_HTTPS_auth.pem ca-file /var/etc/haproxy/clientca_WAN_HTTPS_auth.pem verify required  accept-proxy npn http/1.1
    mode            http
    log         global
    option          http-keep-alive
    option          forwardfor
    acl https ssl_fc
    reqadd X-Forwarded-Proto:\ http if !https
    reqadd X-Forwarded-Proto:\ https if https
    timeout client      7200000
    # Remove headers that expose security-sensitive information.
    rspidel ^Server:.*$
    rspidel ^X-Powered-By:.*$
    rspidel ^X-AspNet-Version:.*$
    acl         aclusr_host_matches_gwsch01.vpn.example.com hdr(host) -i gwsch01.vpn.example.com
    use_backend     gwsch01_http_ipvANY if aclusr_host_matches_gwsch01.vpn.example.com 
    default_backend     _none_http_ipvANY

frontend WAN_SSLH-merged
    bind            127.0.0.1:2022 name 127.0.0.1:2022 ssl no-sslv3 no-tls-tickets no-tlsv10 no-tlsv11 crt /var/etc/haproxy/WAN_SSLH.pem ca-file /var/etc/haproxy/clientca_WAN_SSLH.pem verify required  accept-proxy npn ssh/2.0
    mode            tcp
    log         global
    timeout client      7200000
    acl         aclusr_custom_ssl_fc_sni_reg_20gwsch01.ssh.example.com  ssl_fc_sni_reg gwsch01.ssh.example.com
    acl         aclusr_custom_ssl_fc_npn_20-i_20ssh_2f2.0   ssl_fc_npn -i ssh/2.0
    use_backend     SSH_gwsch01_https_ipvANY if aclusr_custom_ssl_fc_sni_reg_20gwsch01.ssh.example.com aclusr_custom_ssl_fc_npn_20-i_20ssh_2f2.0 
    default_backend     _none_https_ipvANY

backend _ssl-redirect_http_ipvANY
    mode            http
    timeout connect     30000
    timeout server      30000
    retries         3
    option          httpchk
    redirect scheme https code 301

backend gwsch01_http_ipvANY
    mode            http
    rspadd Strict-Transport-Security:\ max-age=31536000;
    rspirep ^(Set-Cookie:((?!;\ secure).)*)$ \1;\ secure if { ssl_fc }
    timeout connect     3000
    timeout server      7200000
    retries         2
    option          httpchk
    server          gwsch01 127.0.0.1:8443 ssl  verify none 

backend _none_tcp_ipvANY
    mode            tcp
    timeout connect     30000
    timeout server      30000
    retries         3
    option          httpchk OPTIONS / 
    server          none 127.0.0.1:61235 check inter 1000 disabled 

backend _WAN_HTTPS_tcp_ipvANY
    mode            tcp
    timeout connect     30000
    timeout server      7200000
    retries         3
    option          httpchk
    server          WAN_HTTPS 127.0.0.1:2043 check-ssl  verify none send-proxy 

backend _WAN_HTTPS_auth_tcp_ipvANY
    mode            tcp
    timeout connect     30000
    timeout server      7200000
    retries         3
    option          httpchk
    server          WAN_HTTPS_auth 127.0.0.1:2044 check-ssl  verify none send-proxy 

backend _openvpn_tcp_ipvANY
    mode            tcp
    timeout connect     3000
    timeout server      7200000
    retries         2
    option          httpchk
    server          openvpn1 127.0.0.1:1194  

backend _WAN_SSLH_tcp_ipvANY
    mode            tcp
    timeout connect     30000
    timeout server      7200000
    retries         3
    option          httpchk
    server          WAN_SSLH 127.0.0.1:2022 check-ssl  verify none send-proxy 

backend _none_http_ipvANY
    mode            http
    timeout connect     30000
    timeout server      30000
    retries         3
    option          httpchk OPTIONS / 
    server          none 127.0.0.1:61235 check inter 1000 disabled 

backend _none_https_ipvANY
    mode            tcp
    timeout connect     30000
    timeout server      30000
    retries         3
    option          httpchk OPTIONS / 
    server          none 127.0.0.1:61235 check inter 1000 disabled 

backend SSH_gwsch01_https_ipvANY
    mode            tcp
    timeout connect     3000
    timeout server      7200000
    retries         2
    option          httpchk
    server          ssh_gwsch01 127.0.0.1:22
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  • 1
    Welcome to Super User! Please quote the essential parts of the answer from the reference link(s), as the answer can become invalid if the linked page(s) change.
    – DavidPostill ♦
    Oct 9, 2015 at 15:54
  • 1
    Where is the final HAProxy configuration in that article? I second @DavidPostill, you must copy the essential parts for the answer to be valid here.
    – Amir
    Jan 2, 2016 at 20:48
  • 1
    Folks, just added a reference file.
    – Julian Pawlowski
    Jan 4, 2016 at 17:13
1

This is impossible. HTTP protocol is different, because there is a "virtual host" concept and HAProxy can differentiate different hosts using "Host:" header. SSH has nothing like this and so the lxc-host is unable to know the container, you are trying to connect.

But you can use another SSH feature called "SSH gateway". Inside ~/.ssh/authorized_keys there is a command= option. Firts setup key-based ssh from your lxc-host to apple and orange. Then put these lines into lxc's authorized_keys file:

command="ssh -q -t user@apple $SSH_ORIGINAL_COMMAND" ssh-rsa AAAAsomeB3N...== user@client
command="ssh -q -t user@orange $SSH_ORIGINAL_COMMAND" ssh-rsa AAAAanotherB3N...== user@client

Now the lxs host can automatically connect to apple and orange, based on the client key.

See more:

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0
0

I am afraid this is impossible. The SSH protocol has no support for hostnames. It just connects to an IP (after resolving ofcourse) and sets up the encrypted connection. There is no concept of 'virtual hosts'.

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HAProxy's blog offers an interesting approach: Route SSH Connections with HAProxy | Dec 21, 2020

In order to route the SSH connections to different servers, you have to know which server the user wants to access. As said previously, HAProxy doesn’t analyze the SSH protocol and, anyway, this protocol doesn’t provide any hint about the destination. So, we have to wrap the connections inside another protocol that will help on that point.

We’ll use the TLS protocol and its SNI extension together with the SSH ProxyCommand feature. Or, said another way, we will wrap our connections with TLS, but we do so simply to leverage SNI so that the client can tell us which server they want to connect to. We will make no use of TLS’s cryptographic features.

[...]

From your clients, you can reach your SSH servers with these commands:

$ ssh -o ProxyCommand="openssl s_client -quiet -connect 172.16.0.10:2222 -servername server1" dummyName1 
$ ssh -o ProxyCommand="openssl s_client -quiet -connect 172.16.0.10:2222 -servername server2" dummyName2 
$ ssh -o ProxyCommand="openssl s_client -quiet -connect 172.16.0.10:2222 -servername server3" dummyName3

Note that the ssh command requires you to send the name of the server that you wish to connect to. We set it to dummyName because we’re specifying the server name using the ProxyCommand field instead. The servername switch lets you set the SNI field content. To make this command shorter, consider creating a bash alias or a script.

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