Provide Internet to an isolated Machine via SSH

Setup on Host A:

1. Install proxy server Squid on Host A . By default Squid listens on port 3128.
   yum install squid
2. Comment the http_access deny all then add http_access allow all in /etc/squid/squid.conf
3. If Host A itself uses some proxy say 10.140.78.130:8080 to connect to internet then also add that proxy to /etc/squid/squid.conf as follows:

refresh_pattern (Release|Packages(.gz)*)$ 0 20% 2880
cache_peer 10.140.78.130 parent 8080 0 no-query default
never_direct allow all

Setup on Host B:

1. Add the following entries to /etc/environment

export http_proxy=http://127.0.0.1:3129
export https_proxy=http://127.0.0.1:3129

1. source /etc/environment

Now our setup is complete.

Creating SSH tunnel with Remote port forwarding

1. Make sure the server is started on Host A (e.g. sudo service squid start).

2. Run the following SSH command from Host A
   ssh -R 3129:localhost:3128 user@HostB

   If you want to make persistent SSH tunnel, you can use autossh as follows:
   autossh -M 20000 -f -NT -R 3129:localhost:3128 user@HostB
   For above autossh command to work, you should be having SSH Keys setup from HostA to HostB

3. This will allow Host B to access the internet through Host A.

Checking the internet:

1. Run the following command from Host B
   wget https://google.com

Traffic flow diagram :

![[Pasted image 20250319123749.png]]

Reference - https://unix.stackexchange.com/questions/116191/give-server-access-to-internet-via-client-connecting-by-ssh