Manual:IP/SOCKS

Applies to RouterOS: all

MikroTik RouterOS supports SOCKS proxy server, version 4.

About SOCKS

SOCKS is a proxy server that allows TCP based application data to relay across the firewall, even if the firewall would block the packets. The SOCKS protocol is independent from application protocols, so it can be used for many services, e.g, WWW, FTP, TELNET, and others.

At first, an application client connects to the SOCKS proxy server, then the proxy server looks in its access list to see whether the client is permited to access the remote application resource or not, if it is permitted, the proxy server relies the packet to the application server and creates a connection between the application server and client.

Remember to configure your application client to use SOCKS version 4.

You should secure the SOCKS proxy using its access list and/or firewall to disallow access from outisde. Failing to secure the proxy server may introduce security issues to your network, and may provide a way for spammers to send junk mail through the router.

Property Description

• connection-idle-timeout (time; default: 2m) - time after which idle connections are terminated
• enabled (yes | no; default: no) - whether to enable or no the SOCKS proxy
• max-connections (integer: 1..500; default: 200) - maxumum number of simultaneous connections
• port (integer: 1..65535; default: 1080) - TCP port on which the SOCKS server listens for connections

Access List

Submenu level: /ip socks access

Description

In the SOCKS access list you can add rules which will control access to SOCKS server. This list is similar to firewall lists.

Property Description

• action (allow | deny; default: allow) - action to be performed for this rule
• allow - allow packets, matching this rule, to be forwarded for further processing
• deny - deny access for packets, matching this rule
• dst-address (IP address/netmask) - destination (server's) address
• dst-port (port) - destination TCP port
• src-address (IP address/netmask) - source (client's) address for a packet
• src-port (port) - source TCP port

Active Connections

Submenu level: /ip socks connections

Description

The Active Connection list shows all established TCP connections, which are maintained through the SOCKS proxy server.

Property Description

• dst-address (read-only: IP address) - destination (application server) IP address
• rx (read-only: integer) - bytes received
• src-address (read-only: IP address) - source (application client) IP address
• tx (read-only: integer) - bytes sent
• type (read-only: in | out | unknown) - connection type
  • in - incoming connection
  • out - outgoing connection
  • unknown - connection has just been initiated

Example

To see current TCP connections:

[admin@MikroTik] ip socks connections> print
 # SRC-ADDRESS                DST-ADDRESS                TX         RX
 0 192.168.0.2:3242           159.148.147.196:80         4847       2880
 1 192.168.0.2:3243           159.148.147.196:80         3408       2127
 2 192.168.0.2:3246           159.148.95.16:80           10172      25207
 3 192.168.0.2:3248           194.8.18.26:80             474        1629
 4 192.168.0.2:3249           159.148.95.16:80           6477       18695
 5 192.168.0.2:3250           159.148.95.16:80           4137       27568
 6 192.168.0.2:3251           159.148.95.16:80           1712       14296
 7 192.168.0.2:3258           80.91.34.241:80            314        208
 8 192.168.0.2:3259           80.91.34.241:80            934        524
 9 192.168.0.2:3260           80.91.34.241:80            930        524
10 192.168.0.2:3261           80.91.34.241:80            312        158
11 192.168.0.2:3262           80.91.34.241:80            312        158
[admin@MikroTik] ip socks connections>

Application Examples

FTP service through SOCKS server

Let us consider that we have a network 192.168.0.0/24 which is masqueraded, using a router with a public IP 10.1.0.104/24 and a private IP 192.168.0.1/24. Somewhere in the network is an FTP server with IP address 10.5.8.8. We want to allow access to this FTP server for a client in our local network with IP address 192.168.0.2/24.

We have already masqueraded our local network:

[admin@MikroTik] ip firewall nat> print
Flags: X - disabled, I - invalid, D - dynamic
 0   chain=srcnat action=masquerade src-address=192.168.0.0/24
[admin@MikroTik] ip firewall nat>

And the access to public FTP servers is denied in firewall:

[admin@MikroTik] ip firewall filter> print
Flags: X - disabled, I - invalid, D - dynamic
 0   chain=forward action=drop src-address=192.168.0.0/24 dst-port=21 protocol=tcp
[admin@MikroTik] ip firewall filter>

We need to enable the SOCKS server:

[admin@MikroTik] ip socks> set enabled=yes
[admin@MikroTik] ip socks> print
                    enabled: yes
                       port: 1080
    connection-idle-timeout: 2m
            max-connections: 200
[admin@MikroTik] ip socks>

Add access to a client with an IP address 192.168.0.2/32 to SOCKS access list, allow data transfer from FTP server to client (allow destionation ports from 1024 to 65535 for any IP address), and drop everything else:

[admin@MikroTik] ip socks access> add src-address=192.168.0.2 dst-port=21 \
\... action=allow
[admin@MikroTik] ip socks access> add dst-port=1024-65535 action=allow
[admin@MikroTik] ip socks access> add action=deny
[admin@MikroTik] ip socks access> print
Flags: X - disabled
 0   src-address=192.168.0.2 dst-port=21 action=allow
 1   dst-port=1024-65535 action=allow
 2   action=deny
[admin@MikroTik] ip socks access>

That's all - the SOCKS server is configured. To see active connections and data transmitted and received:

[admin@MikroTik] ip socks connections> print
 # SRC-ADDRESS                DST-ADDRESS                TX         RX
 0 192.168.0.2:1238           10.5.8.8:21                1163       4625
 1 192.168.0.2:1258           10.5.8.8:3423              0          3231744
[admin@MikroTik] ip socks connections>

Note! In order to use SOCKS proxy server, you have to specify its IP address and port in your FTP client. In this case IP address would be 192.168.0.1 (local IP address of the router/SOCKS server) and TCP port 1080.