Questions tagged [openssh]

Questions about the OpenSSH implementation of the ssh protocol.

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18 views

SSH connection freezes on 4G Hotspot but not on any Wifi

Short Description I have been seeing an strange behaviour on my SSH connection for years but never thought of raising a question until today. I tried to search a lot about this but couldn't find any ...
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27 views

“Warning: untrusted X11 forwarding setup failed” on nested ssh

I have a gateway to ssh into from the bad world wide web. No problem, I get: remote ~$ ssh -X ingo@gateway Debian GNU/Linux 10 (buster) 0:ingo@gateway ~$ Now I manage my other hosts, for example the ...
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34 views

OpenSSH not respecting $HOME when searching for ssh config files

I'm writing some integration tests, that test SSH connections between servers. For the time being the tests are run from people's laptops. In order not to muck around in the user's (the user running ...
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7 views

Access NATed remote system through an existing ssh connection

There is a machine RemoteA that is behind a NAT somewhere on the internet. It can connect to an ssh server. There is another machine called RemoteB that also has a connection to the same ssh server. ...
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Double hop scp - OpenSSH error [duplicate]

I am trying to copy a file from my local machine A to a server C through server B using scp. I have read a couple of things on this, and came up with this: scp -o ProxyCommand="ssh -J user@serverB:...
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What kind of an sshd attack is this?

I have never seen this before in my sshd logs: Mar 16 17:21:48 x-server sshd[9848]: Bad protocol version identification '\026\003\001' from 45.143.221.50 port 35026 Mar 16 17:21:48 x-server sshd[9849]...
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29 views

How to install OpenSSH on stripped down Linux OS without a package manager

I have a satellite box that uses a stripped down version of linux OS. It runs enigma2 SVN-2860 based on GIT-5580 used for watching satellite and terrestrial digital tv. It's a PKT Hyperion enigma2 ...
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2answers
43 views

How to remove (not override, not create new) options from systemd unit files?

How are lines removed from a standard (system) systemd unit file? Here are the details: ls -la /etc/ssh/ssh_host_*key* This shows I have unused and unwanted host key types. They are not configured ...
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1answer
44 views

Can you use both + and - to edit sshd_config option

The answers here helped me a lot. However, in my case, I want to disable some MACs and add a few new ones. Is there a way to do this without hardcoding the options? The following doesn't work. MACs ...
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OpenSSH Http proxy can't connect

I am using Kitty for my SSH connection with HTTP proxy. The telnet command used is: connect %host %port\n I want to use OpenSSH, but I am struggling to make .config work. I even tried netcat but ...
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38 views

Why does reverse SSH tunnel endpoint server crash?

UPDATE: This may be an ISP or routing issue. The crash appears to happen only with specific user locations. Not browser dependent, but maybe ISP dependent. I'm using an Amazon Web Services virtual ...
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19 views

How to make ssh local forward through intermediate server's port

I want to connect to target_server from local_pc through jump_server. Besides, I also want local forward the specified ports of each machine, i.e. local_pc:port1 --> jump_server:port2 --> ...
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48 views

Is there a way to daisy-chain SSH commands using ssh config?

I am trying to SSH from a docker container to a remote server. The docker container is on a Mac. All the authentication to connect to the remote server is done from the Mac, not the docker container. ...
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60 views

Failed to validate path /var/run/sshd: too many levels of symbolic links while Installing OpenSSH

I want To Install OpenSSH via this command sudo apt-get install openssh-server in XUbuntu but I'm getting this error again and again! Failed to validate path /var/run/sshd: Too many levels of ...
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22 views

Make ssh client process end once the connection to server was lost!

I have a ssh process hanging around (i.e., does not exit and end). I can test that no connection with the sshd server exists anymore ss -t | grep [SERVERIP] yields no results. Additionally, being ...
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72 views

Non-root SSH key authentication problems with DSM 6

With Synology DSM 6 it seems that SSH requires users to be members of the admin group. However, even in this case there seem to be problems with file/directory permissions that prevent key-based ...
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63 views

OpenSSH: What is the interval for TCPKeepAlive option?

In sshd config you can specify the option TCPKeepAlive yes. These Pakets are not encrypted so the could be spoofed. With the options ClientAliveInterval ClientAliveCountMax ServerAliveInterval ...
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1answer
41 views

Installing and running ssh server from bash script

I want to be able to install openSSH package and enable and disable it from the script. I have tried doing it like this: elif [[ $1 = "-ss" ]]; then echo "Manage SSH Server" apt-get install ...
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35 views

Script fails when run over inline ssh but not locally or over full ssh session

I have a script on a server that pulls from a remote git repo then compiles the code with make and presents a compiled file to download. When I run locally on the machine or through a regular ssh ...
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1answer
70 views

Can BusyBox do something similar to tmux/dtach?

I need to establish a persistent disconnection-proof terminal session similar to what the dtach, abduco or tmux tools provide, but with a big constraint: I cannot install any software and the only ...
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2answers
53 views

scripted ssh should not ask for a password if public key authentication fails

Here is my use case: I have a script that lists through hundreds of servers and tests whether or not they allow logins using public key authentication using a specific private key (in the ssh client's ...
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11 views

SSH Tunneling, using one server for and splitting to remote hosts

I have a central server, I have 3 raspbery pi's The 3 pi's are on local networks and port forwarding is not possible so I figure a cronjob to connect outward to a central server is the way to go Is ...
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39 views

sshd - Block login via ssh (sshd) for a certain period of time

I use CentOS 7 and would like to know if it is possible to block login via ssh (sshd) for a certain period of time after a certain amount of attempts. EXAMPLE: After 3 wrong attempts the login is ...
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22 views

Ksh/Bash History for jailed SSH users

How can I keep a history of activities for chroot'd SSH (not SFTP) users? I've tried: created a .sh_history in their home with the proper permissions created a custom $HISTFILE in .profile and in its ...
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1answer
58 views

Relationship between options in authorized_keys and options in sshd_config?

I'd like to configure an SSH Daemon on one of my servers so that certain users on remote clients can execute certain commands on the server. Each user, identified by a certain public key, must be able ...
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42 views

DDNS ssh gets stuck after “SSH2_MSG_KEXINIT sent” message

I am trying to set up ssh logging from across the internet. I have a DDNS noip.com domain which I can successfully ping and it reaches my host. The DDNS is configured straight on my router and the ...
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111 views

How can I provide the authorized_keys path in sshd that allows normal users, system users, and a root user?

Is it possible to set the AuthorizedKeysFile setting explicitly such that it covers the following cases: standard user under /home/%u/.ssh/authorized_keys system user under /var/lib/%u/.ssh/...
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75 views

SSH ProxyJump applies wrong username

Given the following ssh.cfg: Host bastion Hostname xx.yyy.169.100 User ubuntu IdentityFile ./the-key.pem Host 10.250.*.* ProxyJump %r@bastion User core IdentityFile ./the-key.pem The ...
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1answer
71 views

My custom SFTP config allows for file creation but no modification or deletion. Can this be done to directories?

I've figured out how to accomplish a "create-but-don't-modify" permission scheme using SFTP. But it works for files only; I'd like to expand it to directories. Background: I have an SFTP server (...
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133 views

channel 84: open failed: administratively prohibited: open failed

I'm trying to ssh via port forwarding. This is my ssh config file: HOST A HostName B user C DynamicForward 0.0.0.0:1081 When I run "ssh A" I get: channel 5: open failed: ...
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37 views

Is there something like HTTP Digest access authentication for SSH?

Apparently, SSH does send (albeit using an encrypted connection) the client's login password to the server if password authentication is being used instead of a pair of public and private keys: Does ...
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93 views

sshd_config: using only the most secure ciphers, KexAlgorithms, MACs

In /etc/ssh/sshd_config I am using the following configuration settings. Can this be further hardened? KexAlgorithms curve25519-sha256@libssh.org MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-512 ...
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49 views

Working with SSH/SSL

I'm not really sure where or to whom I should ask this question, so hopefully you all can help me. I am working on a project that I would like to add data to the end of each packet before encryption ...
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1answer
42 views

ssh using different key when forwarding authentication agent [closed]

I am trying to convince ssh to use my ed25519 id file whenever possible. In order to achieve this and according to this stackexchange question and the man page which states It is possible to have ...
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163 views

SSH add key to known_hosts from ssh-keyscan

I keep a local git repo at a remote host gitserver deployed to my LAN. When I am away from home I have to access that server through the LAN's external IP. (The router does not offer loopback). At ...
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1answer
78 views

CentOS 7 black screen after installing openssh server

My cent OS 7 VM goes into blank screen after installation of openssh server.I tried to try this on another centos7 VM ,same issue occured. Every time when I do yum install openssh-server,all the ...
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45 views

SSH: A to B works, B to A does not

I have two machines A and B within the organization network. I have openssh-server installed and ssh running on both the machines. Both the machines have Ubuntu 16.04. I am able to ssh from A to B ...
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113 views

SSH User CA: Sign a user certificate with selected hosts instead of all hosts?

I have many servers that shares a common TrustedUserCAKeys. I want to sign a user certificate so it grants some access on specific servers instead of all of them. For example, the following command ...
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26 views

SFTP randomly closes out customer SFTP connection from IBM Sterling

I'm at a bit of loss in troubleshooting this issue. We run an Ubuntu 14 server which functions as an SFTP server. OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.10, OpenSSL 1.0.1f 6 Jan 2014 The customer gets ...
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48 views

SSH CA: How to sign a host key with custom port?

I have a server whose sshd listens on a non-standard port, say for example, 8022. I tried to sign its host key like this: ssh-keygen -s ibug_ca -I example -h -n '[example.com]:8022' ssh_host_rsa_key....
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1answer
70 views

How to escape linux character over ssh

I am trying to figure out exactly what is sent to an SSH host when I press CTL-C in either putty or open ssh. All I am trying to do is send control codes pragmatically that are equivalent to when a ...
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1answer
40 views

How to unbottleneck cpu-bound OpenSSH?

sneak@nostromo-2:~$ for i in 3des-cbc aes128-cbc aes128-ctr aes128-gcm@openssh.com aes192-cbc aes192-ctr aes256-cbc aes256-ctr aes256-gcm@openssh.com chacha20-poly1305@openssh.com; do openssl rand ...
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1answer
64 views

ControlMaster conflicts with ForwardAgent

I have set up agent forwarding on my ssh client: Host * ForwardAgent yes User somebody IdentityFile ~/.ssh/id_rsa AddKeysToAgent yes When I log in to the remote system, I see the following ...
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1answer
67 views

Trying to connect to remote server via SSH but still prompts for password

I generated a ssh key pair with ssh-keygen, use ssh-copy-id to the server and checked that the public key was added to authorized_keys, but then when i try to connect with ssh -i ~/.ssh/MY_KEY user@...
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432 views

Install openssh-server 8.0p1 on Ubuntu 18.04.3 LTS

Ubuntu 18.04.3 LTS (bionic) have OpenSSH server version 7.6p1 but that release is 2 years old by now. On my local Arch Linux machine I'm running 8.0p1 but Ubuntu naturally have slower pace. The ...
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1answer
27 views

SSH only working shortly after router reboot

I am trying to create a homemade server. I'm running Ubuntu 18.04 and have an Xfinity router. I've forwarded port 22 to a reserved local IP for my server. The problem is that I can connect via a ...
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44 views

How does the SSH-CA Authentication works in detail?

I know how to Setup the whole SSH-CA Stuff, with Configuration of sshd and signing of the Keys. But what i wondering is, how does the Authentication works in detail? Like it is described here in the ...
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1answer
189 views

OpenBSD - How to manage users that can be SSH into?

Question: How do I disable/enable which users can be connected to via SSH? Can all users be connected into SSH by default or do I need to enable it for the user first?
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1answer
67 views

How Does SSH Chroot Works

When I setup chroot directory for SSH user, I set root as owner of this directory and set permissions to 755. Why must these directories be owned by root and have 755 permissions? Why can't the ...
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1answer
254 views

Provide get commands to SFTP from a script file but keep interactive password login

I have an FTP server that allows only SFTP connection – and only via password. I have a list of files on the server - hundreds and thousands of files in many directories. And the directories contain ...

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