the secure shell (SSH) daemon

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49
votes
2answers
154k views

How can I restart the SSH daemon on Ubuntu?

When I type in service sshd restart I get a sshd: unrecognized service error. I do have, in /etc/ssh/ a file sshd_config that I use to set config. I can also putty into the Ubuntu box (it is remote). ...
46
votes
1answer
51k views

How does tcp-keepalive work in ssh?

I am trying to code a shell-script that uses a ssh-connection for doing "heartbeats". I want to terminate the client- and server-side of that connection after a certain timeout (after the connection ...
26
votes
5answers
68k views

Where are my sshd logs?

I can't find my sshd logs in the standard places. What I've tried: Not in /var/log/auth.log Not in /var/log/secure Did a system search for 'auth.log' and found nothing I've set /etc/ssh/sshd_config ...
17
votes
2answers
3k views

SSH ignores characters after correct password string?

Remote machine 10.10.10.1 has password "asdFGH12" for user named "user". I'm able to log in even if I type in password "asdFGH12dasdkjlkjasdus" or any other characters after the "asdFGH12" string. $ ...
15
votes
2answers
354 views

What is the difference between these two SSHD configs?

1 Match Group GROUPNAME, User *,!root 2 Match Group GROUPNAME User !root My question: What is the difference between #1 and #2 in the SSHD_CONFIG?
13
votes
5answers
1k views

what's the purpose of ssh-agent?

I've read the official definition: ssh-agent is a program to hold private keys used for public key authentication (RSA, DSA, ECDSA). The idea is that ssh-agent is started in the beginning of an X-...
12
votes
3answers
2k views

tmux session killed when disconnecting from ssh

Summary: I'm trying to figure out why my tmux session dies when I disconnect from ssh Details: I have tmux installed on an Arch Linux system. When I start a tmux session I can detach from it and ...
11
votes
1answer
25k views

Installing fail2ban on CentOS 7

I am using @GarethTheRed 's answer to this question to install fail2ban on a remote CentOS 7 server. I am able to complete all the steps up until tail -f /var/log/fail2ban.log, at which point I get ...
11
votes
5answers
88k views

X client forwarded over SSH “cannot open display: localhost:11.0”

I have enabled X forwarding on remote machine where SSH server is running: # grep -i forward /etc/ssh/sshd_config X11Forwarding yes # On local machine, I have started SSH client with -X flag ...
11
votes
2answers
14k views

Why does sshd requires an absolute path?

Why does sshd require an absolute path when restarting, e.g /usr/sbin/sshd rather than sshd Are there any security implications? P.S the error message: # sshd sshd re-exec requires execution with ...
10
votes
2answers
20k views

What do the channel numbers in ssh error message refer to?

In the example below what do the channel numbers correspond to? Which are on the server? Which are on the client? $ ssh -L1570:127.0.0.1:8899 root@thehost Password: Last login: Fri Aug 9 ...
9
votes
5answers
1k views

Failing to block brute force ssh with iptables

I'm trying to block (slow down) brute force attacks on my sshd server. I'm following this guide http://www.rackaid.com/resources/how-to-block-ssh-brute-force-attacks/ which basically says I need to ...
8
votes
3answers
13k views

Allowing only specific users to login via ssh at one port and others to login via another port

I have the following use case: Need to allow users to login from a secured, trusted network and then allowing a couple (only two) mobile users to login remotely on a Linux Centos machine. I can make ...
8
votes
2answers
15k views

Change default path for when I SSH in to CentOS server?

I have a CentOS 5.7 web server, and I want to change the default place I land in when connecting using SSH. Currently I land in /home/username, and I want to land in /home instead. I've gone in as ...
8
votes
1answer
6k views

How to use ssh over http or https?

I have a linux fedora21 client laptop behind a corporate firewall (which lets through http and https ports but not ssh 22) and I have a linux fedora21 server at home behind my own router. Browsing ...
8
votes
1answer
496 views

Blocking SSH Brute Force attacks on IPv6

I recently had to work with some servers that have an IPv6 connection and I was surprised to find out that fail2ban does not have IPv6 support, neither does denyhosts. Searching on google I found that ...
7
votes
2answers
8k views

Can't login to a remote machine with key

I used to login to a remote machine( I have to root of this machine) using key. Both my local machine and remote machine is in f23. From last few days, I can't login to this machine using key. It is ...
7
votes
4answers
3k views

How to debug SSH port forwarding

This is an extension to ssh port forward to access my home machine from anywhere I tried things mentioned there but I am not able to ssh to my machine. Netgear router settings for port forwarding: ...
7
votes
2answers
5k views

How to Provide login delay in ssh

I wanted to provide login delay while login through ssh .I tried couple of ways of doing same but couldn't find desired result. I tried steps provided by given link. http://hostingfu.com/article/ssh-...
7
votes
1answer
395 views

Enable Massive Concurrent SSH to a single server

My goal is to allow 10000 concurrent sshs running on a single server. For simplicity I am ssh-ing to localhost: for i in `seq 1 10000`; do ssh localhost "echo ${i}; sleep 100" >>./info 2&...
6
votes
5answers
2k views

ssh command unexpectedly continues on other system after ssh terminates

I'm running the below command, and monitoring the output file on the other system: ssh $ip_address 'for n in 1 2 3 4 5; do sleep 10; echo $n >>/tmp/count; done' If I kill the ssh command ...
6
votes
4answers
5k views

How to setup password-less ssh with RSA keys

I am trying to setup a password-less SSH configuration between two machines and I am having a problem. There are a ton of howtos out there that I have followed and have had no success. Here are the ...
6
votes
1answer
3k views

How to exclude from a “Match Group” in SSHD?

There is a Match group in the SSHD config: cat /etc/ssh/sshd_config ... Match Group FOOGROUP ForceCommand /bin/customshell ... There are many users on the machine that are in the "FOOGROUP"...
6
votes
1answer
3k views

My reverse-ssh tunnel is using keepalives but they're not helping

I have an ssh client machine picard behind multiple unreliable internet connections - all with NAT. I have my server time, reliable with a static IP. I want to be able to access picard thorugh time. ...
5
votes
3answers
10k views

Authentication refused: bad ownership or modes for file /var/git/.ssh/authorized_keys [duplicate]

EDIT The issue as exposed here is solved (about files modes of the .ssh folder. But an other issue persists so I create a new question : > Unable to login with SSH-RSA key I can no longer ...
5
votes
2answers
74 views

Isolate SSH Authentication Failures into Own Log File on RHEL 6.6

This may be impossible, but I've got a case where we want to log SSH authentication failures separately from standard SSH logging on a RHEL 6.6 box. I am aware we can use SyslogFacility with ...
5
votes
1answer
3k views

Uselogin in sshd_config

I was looking through my sshd_config file and I found this: #Uselogin no I know it's commented but there is no explanation above it and when I google it, I get this: Don't use the traditional ...
5
votes
2answers
8k views

Fedora 18 - Start sshd on boot

I've just installed Fedora 18, and trying to configure sshd - I used chkconfig but this is only starting sshd when a user is logged in. How do I change so that sshd starts on system boot?
5
votes
1answer
2k views

Can sshd restrict client tunnel endpoints to localhost?

Normally an ssh client can request TCP forwarding using the -L command line option. The server can disable this completely using AllowTcpForwarding no. If enabled, the client can request to connect ...
5
votes
1answer
601 views

Linux: $SSH_CONNECTION is set even without SSHing to the server

I have a remote server and I am writing a script in the server and want it to fire only when I SSH. I thought of using the $SSH_CONNECTION and $SSH_TTY for this purpose. I found out that when I have ...
5
votes
1answer
2k views

Logging ssh remote commands to `bash_history`

SSH allows a remote user to issue some command without interactively logging in to the server, as the last line of ssh usage indicates: usage: ssh [-1246AaCfgKkMNnqsTtVvXxYy] [-b bind_address] [-c ...
5
votes
2answers
4k views

ssh-add -D doesn't erase stored keys from the ssh-agent

How come this happens?: stan@tcpc:~/.ssh$ ssh-add -l 8192 e0:45:5e:cc:45:3e:17:2b:a6:54:6f:8d:53:1b:j2:e3 github (RSA) 2048 25:41:53:a6:45:5d:ac:eb:5c:45:f8:ce:42:a9:he:aa BITBUCKET (RSA) stan@tcpc:~/...
4
votes
4answers
263 views

Internet SSH Server Security Considerations

What steps should I take to reasonably secure my linux desktop before opening sshd to the Internet so I can connect from anywhere?
4
votes
2answers
315 views

which config file is openssh sshd using?

Where can i check/verify which config file sshd is using? I know you can change the config file to use by using -f command, but is there a way to echo which config file is currently being used or is ...
4
votes
2answers
4k views

Disable ssh banner for specific users or ips

I've enabled the banner that appears before the password prompt by setting it it sshd_config. However certain users (especially me) really don't need to see the banner (it also screws up a lot of ...
4
votes
1answer
222 views

hosts.allow: %u not working (log username)

I need to keep track of all SSH connections on my server. In my /etc/hosts.allow I have something like this: sshd: ALL : spawn ( echo "`date` from %u %a " >> /var/log/ssh/%d.log ) & where ...
4
votes
1answer
230 views

sudo command inside heredoc block in a ssh session is not working

When i use heredoc and put all the commands inside heredoc as, ssh -t -i master.pem cloud-user@$1 <<EOSSH sudo service x restart sudo service y restart EOSSH it throws error as, Pseudo-...
4
votes
1answer
160 views

Accept any private key for authentication

Is it possible to configure OpenSSH (or any other standard sshd) to accept any key offered by a connecting client? EG ssh -i ~/arbitraryKey hostname grants a login shell while ssh hostanme doesn't. ...
4
votes
1answer
694 views

Executing a remote command on SSH connection, before login

I am trying to find a way to execute a specific command when connecting to a server via SSH. By this I mean, the command will execute unconditionally on opening a connection, so this would preferably ...
4
votes
3answers
987 views

Is there an easy way to not log a specific sshd event?

The monitoring tool of my hoster is making regular connections with ssh on port 22 to see or the service is up. This is cluttering my /var/log/messages with this kind of messages: Dec 13 22:20:17 ...
4
votes
1answer
58 views

How to avoid calling 'startx' upon ssh login

my current situation is that in my .zprofile file I have the following line I found somewhere on the internet [[ -z $DISPLAY && $XDG_VTNR -eq 1 ]] && exec startx I think it's ...
4
votes
1answer
11k views

Activity Logging Level in SFTP

I'm using CentOS, i have already figured out how to enable the SFTP Logging. After that when i test it by using FileZilla (from User-end) and tail -f /var/log/sftp.log from the Server, all the ...
4
votes
2answers
61 views

Understand the PasswordAuthentication in sshd configuration

I have an OpenSSH server which supports only password authentication: [martin@ ~]$ ssh -v 10.10.1.183 -l root OpenSSH_5.2p1 FreeBSD-20090522, OpenSSL 0.9.8k 25 Mar 2009 debug1: Reading configuration ...
4
votes
1answer
737 views

Why did sshd delete my /dev/zero?

When I do lsof +c 0 | grep /dev/zero, I see the following two lines: sshd 19064 root DEL REG 0,4 497862 /dev/zero sshd 19064 root DEL REG 0,4 498725 /dev/zero ...
4
votes
1answer
116 views

Separate messages of multiple sshds in syslog-ng

Is there a common way of distinguishing between the messages of multiple processes in syslog-ng beside setting different facilities? +1 if filtering and therefore logging in different files would be ...
4
votes
3answers
6k views

How to start SSH daemon on boot on Linux Mint Debian v2

I'm using Linux Mint Debian v2, 64-bit. I noticed recently that my ssh daemon does not start automatically on boot. It used to. I'm not sure if it had to do with my UFW configuration or sshd_config ...
4
votes
5answers
305 views

Multiline Text Processing : Editing sshd_config

I have multiple blocks at the end of my sshd_config files like theses: Match User FOO ChrootDirectory /srv/www/FOO AllowTCPForwarding no X11Forwarding no ForceCommand internal-sftp ...
4
votes
2answers
113 views

How to change service type of well defined ports in SElinux (centOS 6.5)

I need to be able to run SSH on port 23 instead of 22 on CentOS 6.5. SElinux won't allow that, as it has it as tcp/23 defined in policy. Any steps on how can I go about changing service type from ...
4
votes
2answers
1k views

Starting SSH server after VPN starts

I am running an OpenVPN server on Ubuntu 14.04 as well as OpenSSH. I have my SSH server configured to bind to an IP address on my VPN interface. Once my machine boots, binding to that IP fails. ...
4
votes
0answers
819 views

SSH AuthorizedKeysCommand and SELinux

I'm trying to use the SSH AuthorizedKeysCommand in a CentOS 6.5 machine, but I'm encountering an SELinux error. When I switch SELinux to permissive mode - using setenforce 0 - it works, but when I ...