How to tunnel through a computer under Win7?

Question

Windows

Good afternoon.
The essence of the problem.
1. There is a private intranet
2. There is a CentOS server accessible only from this intranet (A)
3. There is a Win7 computer that can access this intranet through a specific VPN (custom corporate solution, binding to a poppy address, run on another machine is impossible) (B).
4. (B) has free Internet access via office WiFi
Objective: to make it possible for any computer on the same network as (B) to work with the server (A) using VPN connection (B). Probably some tricky ssh tunnel or something. On (B) you can install software. On (A) - very limited (it is impossible to raise a separate VPN).
I would be grateful for any hint.

Answer 1

In theory, it is enough to enable routing to B (a setting in the registry, it may already be enabled) and configure B on all computers in its subnet as a gateway for subnet A (prescribe a route to A through B).