I' m sure you will find the question similar to many other posts on stackoverflow or on internet. However, I could not find the solution to my problem precisely. I have list of task to be run on remote server, and passing the script is OK! however does not suit to the requirement.
I' m running following from my server to connect to remote server;
ssh -t user#server << 'HERE'
sudo su - <diff_user>
do task as diff_user
HERE
ssh -tt user#server << 'HERE'
sudo su - <diff_user>
do task as diff_user
HERE
With first option (-t), I' m still not able to do sudo, it says below;
sudo: sorry, you must have a tty to run sudo
With second option above (-tt), I' m getting reverse input/output to current server session, total mess.
I tried passing the content as an script to SSH to run on remote host, however, getting similar results.
Is there a way other than commenting out below?
Defaults requiretty in /etc/sudoers file
I have not tried above though, I know RedHat approved it to be removed/ commented out in future version, whenever that is. If I go with step, I will have get above done in 100's of VM's (moreover, I dont have permission to edit the file on VM's and give it a try).
Bug 1020147
Hence, my issue remains the same, as before. It would be great if I can get some input from experts here :)
Addition Info : Using RedHat RHEL 6, 2.6.32-573.3.1
I do have access to the remote host and once I' m in, my ID does not require password to switch to diff_user.
When you are asking this way, I guess you don't have passwordless sudo.
You can't communicate with the remote process (sudo), when you put the script on stdin.
You should rather use the ssh and su command:
ssh -t user#server "sudo su - <diff_user> -c do task as diff_user"
but it might not work. Interactive session can be initiated using expect (a lot of questions around here).
I was trying to connect to another machine in an automated fashion and check some logs only accessible to root/sudo.
This was done by passing the password, server, user, etc. in a file — I know this is not safe and neither a good practice, but this is the way it will be done in my company.
I have several problems:
tcgetattr: Inappropriate ioctl for device;
tty related problems that I don't remember exactly;
sudo: sorry, you must have a tty to run sudo, etc..
Here is the code that worked for me:
#!/bin/bash
function checkLog(){
FILE=$1
readarray -t LINES < "$FILE"
machine=${LINES[4]}
user=${LINES[5]}
password=${LINES[6]}
fileName=${LINES[7]}
numberOfLines=${LINES[8]}
IFS='' read -r -d '' SSH_COMMAND <<EOT
sudo -S <<< '$password' tail $fileName -n $numberOfLines
EOT
RESULTS=$(sshpass -p $password ssh -tt $user#$machine "${SSH_COMMAND}")
echo "$RESULTS"
}
checkLog $1
Related
I'm using flask with apache(mod_wsgi).
When I use ssh module with external command subprocess.call("ssh ......",shell=True)
(My Python Flask code : Not wrong)
ssh = "sshpass -p \""+password+"\" ssh -p 6001 "+username+"#"+servername+" \"mkdir ~/MY_SERVER\""
subprocess.call(ssh, shell=True)
I got this error on Apache error_log : Failed to get a pseudo terminal: Permission denied
How can I fix this?
I've had this problem under RHEL 7. It's due to SELinux blocking apache user to access pty. To solve:
Disable or set SELinux as permissive (check your security needs): edit /etc/selinux/config and reboot.
Allow apache to control its directory for storing SSH keys:
sudo -u apache
chown apache /etc/share/httpd
ssh to desired host, accept key.
I think apache's login shell is "/sbin/nologin".
If you want to allow apache to use shell command, modify /etc/passwd and change the login shell to another shell like "/bin/bash".
However, this method is vulnerable to security. Many python ssh modules are available in internet. Use one of them.
What you are doing seems frightfully insecure. If you cannot use a Python library for your SSH connections, then you should at least plug the hole that is shell=True. There is very little here which is done by the shell anyway; doing it in Python affords you more control, and removes a big number of moving parts.
subprocess.call(['/usr/bin/sshpass', '-p', password,
'/usr/bin/ssh', '-T', '-p', '6001', '{0}#{1}'.format(username, servername),
'mkdir ~/MY_SERVER'])
If you cannot hard-code the paths to sshpass and ssh, you should at least make sure you have a limited, controlled PATH variable in your environment before doing any of this.
The fix for Failed to get a pseudo-terminal is usually to add a -T flag to the ssh command line. I did that above. If your real code actually requires a tty (which mkdir obviously does not), perhaps experiment with -t instead, and/or redirecting standard input and standard output.
I am trying to connect to a remote host from my local host through the below command.But there was a setting in the remote host that soon after we login it will prompt to enter a badge ID,password and reason for logging in, because it was coded like that in profile file on remote-host How can I overcome those steps and login directly non-interactively, without disturbing the code in profile.
jsmith#local-host$ ssh -t -t generic_userID#remote-host
Enter your badgeID, < exit > to abort:
Enter your password for <badgeID> :
Enter a one line justification for your interactive login to generic_userID
Small amendment: to overcome remote server expect approach is required, but in case local script connects to bunch of remote servers, which configuration may be broken, just use SSH options:
ssh -f -q -o BatchMode=yes -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null USER#TARGETSYSTEM
This will omit ask for password in case there is no ssh_key setup, exit silently and continue with script/other hosts.
Puts ssh to background with -f, which is required when calling ssh command from sh (batch) file to remove local console redirect to remote input (implies -n).
Look into setting up a wrapper script around expect. This should do exactly what you're looking for.
Here are a few examples you can work from.
I have upvoted Marvin Pinto's answer because there is every reason to script this, in case there are other features in the profile that you need, such as Message of the Day motd.
However, there is a quick and dirty alternative if you don't want to make a script and you don't want other features from the profile. Depending on your preferred shell on the remote host, you can insist that the shell bypasses the profile files. For example, if bash is available on the remote host, you can invoke it with:
ssh -t -t generic_userID#remote-host bash --noprofile
I tested the above on the macOS 10.13 version of OpenSSH. Normally the command at the end of the ssh invocation is run non-interactively, but the -t flag allows bash to start an interactive shell.
Details are in the Start-up files section of the Bash Reference Manual.
I want to dump a tables backup on another server and I am using ssh for doing it.
when I run the below command, it gives an error but dump file is copied to destination.
mysqldump -u username -ppassword dbname tablename | ssh -t -t servers_username#domain_name 'cat > /tmp/bckp.sql';
tcgetattr: Invalid argument
If I press CTRL+c then it appends error message with Killed by signal 2.
Why is this error?
I've seen this error when forcing pseudo-terminal allocation using ssh -t -t or ssh -tt.
The tcgetattr function is used to look up the attributes of the pseudoterminal represented by a file descriptor; it takes a file descriptor and a pointer to a termios structure to store the terminal metadata in. It looks to me from the stub code in glibc that this error represents a null pointer for the termios struct. I am not sure whether these same error handling semantics are in place for the platform-specific implementations of tcgetattr.
If you want to suppress this error, invoke ssh like so:
ssh 2>/dev/null
This will redirect STDERR to /dev/null; you won't see the error when invoking with this redirection. Note that this will mask other errors with ssh; you may need to remove this for debugging purposes.
In my case, forcing pty allocation on the outer ssh of a two-level ssh invocation fixed the problem.
Details:
When you provide a command for ssh to run ( e.g. ssh some_server "do_some_command" ), then ssh assumes you won't need an interactive session, and it will not allocate a pty as it submits the "do_some_command" job you asked it to.
However, things get interesting if you have two layers of ssh (e.g. let's say you want to ssh into a "gateway" machine first, and from there you ssh into an "inner" machine and run some "inner_command").
The thing is, with a two-layer ssh'ing job, from the perspective of the outer ssh, you are requesting that the outer ssh run a non-interactive command, hence the outer ssh will not allocate a tty.
If the command you are running in the inner ssh is meant to be interactive, it will probably want to query tty attributes and it will (righteously) complain that it is not being run on a tty.
The solution in my case was to force the outer ssh to allocate a pty, by using the -t argument. So it looked like this:
ssh -t <gateway_machine> "ssh <inner_machine> \"<inner_interactive_command>\" "
Greetings to the sysadmins out there
I'm using cygrunsrv and autossh on windows XP to create a service building a tunnel to a remote server but i also want to create another tunnel from the remote server to another server.
I can achieve it with this command line :
autossh -M 5432 serverA -t 'autossh -M 4321 serverB -N'
but when I want to set it up in cygwin through cygrunsrv to make it works as a service :
cygrunsrv -I TUNNEL -p /usr/bin/autossh -a "-M 5432 serverA -t 'autossh -M 4321 serverB -N'" -e AUTOSSH_NTSERVICE=yes -e AUTOSSH_POLL=20 -e AUTOSSH_GATETIME=30
It's not fully working. The service is creating the tunnel correctly to ServerA but it's not sending the autossh command "autossh -M 4321 serverB -N" to ServerA.
I tried to escape the quote but all my efforts didn't make any difference and I'm not seeing any command sent in the autossh logs.
I think the problem is related to pseudo terminal that is not created through the cygrunsrv.
I'd like to know if there's a way to fix my cygrunsrv command line to make it work or should I consider a different approach ?
Lionel, try removing the AUTOSSH_NTSERVICE=yes from the cygrunsrv invocation. As /usr/share/doc/autossh/README.Cygwin explains:
Setting AUTOSSH_NTSERVICE=yes in the calling environment ...
change[s] autossh's behavior in three useful
ways:
(1) Add an -N flag to each invocation of ssh, thus disabling shell
access. The idea is that if you're running autossh as a system
service, you're using it to forward ports; it wouldn't make sense to
run a shell session as a system service. (If you think this reasoning
is wrong, please send a bug report to the author or Cygwin maintainer,
and tell us what you're trying to do.)
Despite what the above says, it seems that you may have a good reason for not wanting -N (which suppresses command execution) in your service's ssh invocation. Removing AUTOSSH_NTSERVICE=yes should take care of it. It will have a couple of other minor disadvantages, but you can probably live with it. Read the rest of README.Cygwin for the details.
How can you make SSH read the password from stdin, which it doesn't do by default?
based on this post you can do:
Create a command which open a ssh session using SSH_ASKPASS (seek SSH_ASKPASS on man ssh)
$ cat > ssh_session <<EOF
export SSH_ASKPASS="/path/to/script_returning_pass"
setsid ssh "your_user"#"your_host"
EOF
NOTE: To avoid ssh to try to ask on tty we use setsid
Create a script which returns your password (note echo "echo)
$ echo "echo your_ssh_password" > /path/to/script_returning_pass
Make them executable
$ chmod +x ssh_session
$ chmod +x /path/to/script_returning_pass
try it
$ ./ssh_session
Keep in mind that ssh stands for secure shell, and if you store your user, host and password in plain text files you are misleading the tool an creating a possible security gap
You can use sshpass which is for example in the offical debian repositories. Example:
$ apt-get install sshpass
$ sshpass -p 'password' ssh username#server
You can't with most SSH clients. You can work around it with by using SSH API's, like Paramiko for Python. Be careful not to overrule all security policies.
Distilling this answer leaves a simple and generic script:
#!/bin/bash
[[ $1 =~ password: ]] && cat || SSH_ASKPASS="$0" DISPLAY=nothing:0 exec setsid "$#"
Save it as pass, do a chmod +x pass and then use it like this:
$ echo mypass | pass ssh user#host ...
If its first argument contains password: then it passes its input to its output (cat) otherwise it launches whatver was presented after setting itself as the SSH_ASKPASS program.
When ssh encounters both SSH_ASKPASS AND DISPLAY set, it will launch the program referred to by SSH_ASKPASS, passing it the prompt user#host's password:
An old post reviving...
I found this one while looking for a solution to the exact same problem, I found something and I hope someone will one day find it useful:
Install ssh-askpass program (apt-get, yum ...)
Set the SSH_ASKPASS variable (export SSH_ASKPASS=/usr/bin/ssh-askpass)
From a terminal open a new ssh connection without an undefined TERMINAL variable (setsid ssh user#host)
This looks simple enough to be secure but did not check yet (just using in a local secure context).
Here we are.
FreeBSD mailing list recommends the expect library.
If you need a programmatic ssh login, you really ought to be using public key logins, however -- obviously there are a lot fewer security holes this way as compared to using an external library to pass a password through stdin.
a better sshpass alternative is :
https://github.com/clarkwang/passh
I got problems with sshpass, if ssh server is not added to my known_hosts sshpass will not show me any message, passh do not have this problem.
I'm not sure the reason you need this functionality but it seems you can get this behavior with ssh-keygen.
It allows you to login to a server without using a password by having a private RSA key on your computer and a public RSA key on the server.
http://www.linuxproblem.org/art_9.html