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In order to gain web access from the perspective of a remote device, it is very common to use the SOCKS5 to SSH Tunnel capability built into OpenSSH Client and Putty (detailed here). Both clients establish an SSH transport to the remote device and open a local port that accepts SOCKS5 requests that translates the request to a direct-tcpip SSH Channel. This then allows modern web browsers to speak to the SOCKS5 port and render web pages being requested by the remote device.

The main problem to this approach is that SSH clients' open a port for SOCKS5 that is accessible to everyone. Even if it is only opened on the loopback, other local users may be able to use the port.

At first I thought about trying to secure the SOCKS5 traffic with using User/Pass Auth, but this is not supported by the SSH Clients or the Web Browsers. I then thought about using a Unix sockets instead of an open port, but it is unclear if they are supported by the browsers and/or clients and will definitely not work on most version on Windows (my primary target).

Is there any way to lock down the open SOCKS5 port more than restricting it to the loopback, specifically on Windows?

Liam Kelly
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  • possible solution is to lock the port to users or group using Windows 10/2016 firewall features: https://docs.microsoft.com/en-us/windows/security/threat-protection/windows-firewall/restrict-server-access-to-members-of-a-group-only – Liam Kelly Aug 20 '19 at 19:28

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