how to make ssh-agent automatically

Karl M karlm30@hotmail.com
Thu Dec 1 17:45:00 GMT 2005


Hi...

It is just a little program I wrote to send the message. It is attached.

The method I used works on XP and 2000. I have not tested on any other 
platforms.

HTH,

...Karl

>From: CyberZombie Subject: Re: how to make ssh-agent automatically
>Date: Thu, 01 Dec 2005 11:03:20 -0600
>
>I am unable to locate "sendchenv".  This tool looks like it solves a 
>frustrating problem I have been having (getting regtool changes to register 
>in any new Cygwin/Windows program).  Can you point out where to find it?
>
>Karl M wrote:
>>Hi H.S....
>>
>>Using keychain is only one way, it is not the only way. I no longer use 
>>keychain.
>>
>>I launch ssh-agent from a bash script that is run as a service from 
>>cygrunsrv; it is run as the user, not as SYSTEM. This makes the ssh-agent 
>>process survive Windows logout; I only have to enter a passphrase after 
>>reboot. The bash script edits the user registry to define the environment 
>>variable for the ssh-agent socket. It sends a message that the environment 
>>has been updated and then waits on a sleeping child to keep the service 
>>control manager happy.
>>
>>The script looks like
>>
>>$ cat /bin/secret-agent-service
>>#!/bin/bash
>># Launch the ssh-agent from a service so it survives logoff.
>>
>># When the service stops, kill the ssh-agent.
>>trap "ssh-agent -k;
>>  exit 0" TERM
>>
>># Clean up old files that may be left behind after a crash.
>>#   The file permissions make this safe to do in a multi-user
>>#   environment, but "/tmp" must be local to this host.
>>rm -rf /tmp/ssh-*
>>
>># Launch the ssh-agent.
>>eval $(ssh-agent)
>>
>># Provide the ssh-agent socket ID via the registry and broadcast
>>#   the change in case the user is logged before we finish.
>>#   Do not provide the ssh-agent PID to minimize the risk of
>>#   killing the ssh-agent.
>>regtool -s set /HKEY_CURRENT_USER/Environment/SSH_AUTH_SOCK $SSH_AUTH_SOCK
>>sendchenv
>>
>># Wait quietly until the service is stopped.
>>while true; do
>>  sleep 24h &
>>  wait
>>done
>>
>>In my .bash_profile I have
>>
>>ssh-add -l >/dev/null 2>&1
>>if [ $? -eq 1 ]; then
>>  ssh-add
>>fi
>>
>>which checks if the agent is there and needs a passphrase, and if so, 
>>invokes ssh-add and I enter my passphrase.
>>
>>I will look at the new cygrunsrv changes and see if I can simplify things 
>>and then propose a package.
>>
>>This saves almost one second of CPU time when I start a bash window, 
>>compared to using keychain (also launched as a service).
>>
>>HTH,
>>
>>...Karl
>>
>>>From: "H.S." Subject: Re: how to make ssh-agent automatically
>>>Date: Wed, 30 Nov 2005 21:24:20 -0500
>>>
>>>Hi Karl,
>>>
>>>Karl M wrote:
>>> > Hi HS...
>>> >
>>> > You can use keychain (a package available from setup.exe).
>>> >
>>> > I do something like
>>> >
>>> > ssh-add -l >/dev/null 2>&1
>>> > if [ $? -eq 1 ]; then
>>> >  ssh-add
>>> > fi
>>> >
>>> > in my .bash_profile, because keychain is slow when I launch several
>>> > windows.
>>>
>>>Okay, I will try that. BTW, just out of curosity, is using keychain only
>>>one of the methods to achieve this or is it the only method? I mean, is
>>>it possible to do this without keychain or any other packages and just
>>>with ssh and rsync and login/logout files and environment variables?
>>>
>>>
>>> >
>>> > Why do you kill the agent when you log out? (Windows will kill it when
>>> > you log off from windows.)
>>>
>>>Currently I was starting ssh-agent in cygwin command prompt window. And
>>>if I did not kill ssh-agent the window would not close upon exit. By
>>>killing if from .bash_logout solved that problem.
>>>
>>>thanks,
>>>->HS
>>>
>>> > If you want to keep the agent around from one login to the next, you 
>>>can
>>> > launch the agent as a service. I used to do that with keychain, but 
>>>for
>>> > performance reasons, I use ssh-agent and ssh-add directly. I plan on
>>> > proposing a package for doing this.
>>> >
>>> > HTH,
>>> >
>>> > ...Karl
>>> >
>>> >
>>>
>>>
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>>
>>
>>
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>>
>

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