Difference between revisions of "Ssh reverse tunnel"
From Teknologisk videncenter
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| Line 37: | Line 37: | ||
WantedBy=default.target | WantedBy=default.target | ||
RequiredBy=network.target | RequiredBy=network.target | ||
| + | </source> | ||
| + | =local machine= | ||
| + | On local machine you want to ssh from. | ||
| + | <source lang=bash> | ||
| + | #!/bin/bash | ||
| + | |||
| + | declare -A hosts | ||
| + | |||
| + | # machinename in /etc/hosts maps to portnumber | ||
| + | hosts["mars"]=9999 | ||
| + | hosts["mbus1"]=9998 | ||
| + | hosts["mars2"]=9997 | ||
| + | hosts["dhdc"]=9996 | ||
| + | |||
| + | host=$1 | ||
| + | user=$2 | ||
| + | ip="localhost" | ||
| + | |||
| + | echo "Value for $host is ${hosts[${host}]}" | ||
| + | echo "Value for $host is ${hosts[$host]}" | ||
| + | set -x | ||
| + | #ssh -p ${hosts[${host}]} ${user}@${localhost} | ||
| + | ssh $3 -p ${hosts[${host}]} ${user}@${ip} | ||
| + | |||
</source> | </source> | ||
=Links= | =Links= | ||
*https://qbee.io/misc/reverse-ssh-tunneling-the-ultimate-guide/ | *https://qbee.io/misc/reverse-ssh-tunneling-the-ultimate-guide/ | ||
[[Category:Linux]] | [[Category:Linux]] | ||
Revision as of 14:27, 22 January 2026
To ssh to a Linux server behind a firewall that doesn't allow incoming connections, a reverse ssh tunnel can be created from the server to a known client host. The client host should have a static IP address or a DNS hostname.
Remote server
To allow login without password create public/private rsa key pair on the client and copy the private key to the .ssh/authorized_keys file an set mod to 600
ssh -o TCPKeepAlive=yes -R 9000:localhost:22 heth@93.166.84.21
Establishing the reversed tunnel from a scriptfile. You probably needs to install autossh.
#!/usr/bin/bash
# See: https://medium.com/@souri.rv/autossh-for-keeping-ssh-tunnels-alive-5c14207c6ba9
REMOTE_HOST="222.2.2.2"
REMOTE_PORT="9000"
REMOTE_USER="steve"
autossh -M 0 -gNC $1 -o "ExitOnForwardFailure=yes" -o "ServerAliveInterval=10" -o "ServerAliveCountMax=3" -R ${REMOTE_PORT}:localhost:22 ${REMOTE_USER}@${REMOTE_USER}
/etc/systemd/system/reversessh.service
[Unit]
Description=Reverse SSH tunnel
After=network.target
StartLimitIntervalSec=60
StartLimitBurst=12
[Service]
ExecStart=/bin/bash /home/steve/bin/reversessh.sh
Type=simple
User=steve
Group=steve
Restart=on-failure
RestartSec=5
[Install]
WantedBy=default.target
RequiredBy=network.target
local machine
On local machine you want to ssh from.
#!/bin/bash
declare -A hosts
# machinename in /etc/hosts maps to portnumber
hosts["mars"]=9999
hosts["mbus1"]=9998
hosts["mars2"]=9997
hosts["dhdc"]=9996
host=$1
user=$2
ip="localhost"
echo "Value for $host is ${hosts[${host}]}"
echo "Value for $host is ${hosts[$host]}"
set -x
#ssh -p ${hosts[${host}]} ${user}@${localhost}
ssh $3 -p ${hosts[${host}]} ${user}@${ip}