SSH-Tunneling hints

=== {{id name="SSH-Tunnelinghints-Motivation"/}}Motivation ===

Sometimes it's very useful to directly connect tools (i.e. a database management tool) that runs on a developer or administrator PC, to a daemon on a server (i.e. mysql server) that is only available locally with the server for security reasons.

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=== {{id name="SSH-Tunnelinghints-Exampleintroduction"/}}Example introduction ===

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For the following tunnel examples we assume:

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* A server, {{code language="none"}}www.clazzes.org{{/code}}, runs a mysql server listening on {{code language="none"}}127.0.0.1:3306{{/code}}

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* It provides a database {{code language="none"}}testdb{{/code}}, accessible for user {{code language="none"}}dbtester{{/code}} with password {{code language="none"}}testsecret{{/code}}.

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* The server provides a unix account, {{code language="none"}}webadmin{{/code}}, and we have a ssh key allowed to connect to {{code language="none"}}webadmin@www.clazzes.org{{/code}} (or we have password based ssh access)

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* We want to access to the database {{code language="none"}}testdb{{/code}} through an ssh tunnel

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* When logged in to the server, the local mysql client can connect to the database with: {{code language="none"}}mysql -h 127.0.0.1 -u dbtester --password=testsecret testdb{{/code}}

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* We want to create a tunnel so when connection to port {{code language="none"}}3333{{/code}} on our local system, we actually connect to mysql-server's port {{code language="none"}}3306{{/code}} on {{code language="none"}}www.clazzes.org{{/code}}

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DO NOT bother to try using those credentials, it might get your IP blocked!

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=== {{id name="SSH-Tunnelinghints-OpenSSH"/}}OpenSSH ===

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OpenSSH is the default ssh implementation for most Linux distros, and even Microsoft has announced an agreement to include it in Windows.

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I'm not sure how equal or similar other Unix ssh clients (like BSD, MacOS) are.

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To create a tunnel that stays in foreground:

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# stay in forground, may be put in background by pressing Ctrl-Z and the command bg

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ssh root@clazzes.org -L 3333:127.0.0.1:3306 -N

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# go in background, a bit difficult to stop

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ssh -f root@clazzes.org -L 3333:127.0.0.1:3306 -N

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# evtl. check that ssh listens on 3333

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lsof -i -n |grep -i listen |grep 3333

Test connect to the database:

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mysql -h 127.0.0.1 -P 3333 -u dbtester --password=testsecret testdb

Voila!

To close the tunnel, abort or kill the according {{code language="none"}}ssh{{/code}} process ({{code language="none"}}ctrl-c{{/code}}, evtl. after {{code language="none"}}fg{{/code}} to get it back to the foreground).

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=== {{id name="SSH-Tunnelinghints-Putty"/}}Putty ===

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Putty is the most common ssh client for Windows. Hints for setting up key-based ssh access with Putty can be found everywhere on the internet, we'll focus on tunneling here.

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Just one hint anyway: With ssh keys, have {{code language="none"}}pagent{{/code}} running. Simply double-klick the {{code language="none"}}.ppk{{/code}} file or even put it in your autostart group.

To setup the tunnel:

* Start Putty

* If you don't have a session yet (% style="line-height: 1.4285715;" %)that allows you to connect to (% style="line-height: 1.4285715;" %){{code language="none"}}www.clazzes.org{{/code}} as (% style="line-height: 1.4285715;" %){{code language="none"}}webadmin{{/code}}, set one up and don't forget to save the session before (re)trying to connect.

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* In Session, load the session that allows you to connect to {{code language="none"}}www.clazzes.org{{/code}} as {{code language="none"}}webadmin{{/code}}.

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* In "{{code language="none"}}Category{{/code}}", open {{code language="none"}}Connection{{/code}}, {{code language="none"}}SSH{{/code}}, {{code language="none"}}Tunnels{{/code}}

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* In "{{code language="none"}}Source port{{/code}}", enter {{code language="none"}}3333{{/code}}

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* In "{{code language="none"}}Destincation{{/code}}", enter {{code language="none"}}127.0.0.1:3306{{/code}} as shown in this screenshot (click to enlarge):

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[[image:attach:putty-tunnel-example.png||thumbnail="true" height="150"]]

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* If you really really want to DANGEROUSLY provide the tunnel for other colleages in you LAN, check "Local ports accept connections from other hosts".

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* Click "{{code language="none"}}Add{{/code}}"

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* In "{{code language="none"}}Category{{/code}}", click on "{{code language="none"}}Session{{/code}}", "{{code language="none"}}Save{{/code}}", then "{{code language="none"}}Open{{/code}}"

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Now a putty window should open, you should be on {{code language="none"}}www.clazzes.org{{/code}} as {{code language="none"}}webadmin{{/code}}., and the tunnel should be up.

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To check if there's a tunnel, open a Command window and use netstat like this:

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netstat -a -n |find "3333"

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# output should show something like

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TCP 0.0.0.0:3333 0.0.0.0:0 LISTENING