Questions about the OpenSSH implementation of the ssh protocol.

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2
votes
1answer
81 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 ...
0
votes
2answers
20 views

downloading sshd logs from remote centos 7 server

When I log into a remote centos 7 server as root, I am able to see the sshd logs by typing journalctl _COMM=sshd in the terminal. But the logs are massive. How can I download all the logs into a ...
0
votes
0answers
28 views

SSH client connection not working to remote servers not working

I am unable to connect to other machines from one of my servers. Here is the verbose output (IP, domain, port are masked. OpenSSH version info removed): $ ssh -vvv user@example.com -p yyyy debug1: ...
0
votes
1answer
55 views

CentOS 7 VPN server

How do I set up a remote internet web server using CentOS 7 so that it is completely shielded by a VPN? Here is the use case: 1.) This means that ALL requests for ANY interaction with the web ...
2
votes
1answer
443 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) ...
0
votes
1answer
26 views

SSH connection gets lost, but not when logged in to MySQL

When I open an SSH connection to our database server and leave it open for a longer time, the connection gets lost at some point. I don't know why or how, but this happens a lot. I still see the ...
2
votes
1answer
23 views

Programatically / dynamically adjust SSH session port forwards

I have a workflow where I am trying to do the following: For a given existing SSH session, access the remote machinne and perform a process from which a port is returned (e.g. a remote daemon has ...
1
vote
1answer
34 views

restricting remote vpn login to ip address in CentOS 7

I have read that OpenSSH itself does not support authentication via specific IP address. In a CentOS 7 installation on a web server, how would one configure the login so that a user would not only ...
1
vote
2answers
77 views

SSH PC at office in local network from home

My office has one default gateway and behind that is a local network with locally assigned IP addresses to all computers including mine. I hold admin in my Ubuntu installed office PC and is it ...
2
votes
2answers
33 views

temporarily disable login using one specific ssh key

On my server, I have several public SSH keys in ~/.ssh/authorized_keys. I would like to temporarily block/disallow/deactivate one key. I want to prevent the user to log in using this key now. but I ...
2
votes
0answers
40 views

How to find out what triggers ssh-askpass prompting for passphrase periodically

I recently deleted the contents of my ~/.ssh directory and generated new keys. They new ones work fine, but every once in a while I am getting a gui dialog titled OpenSHH from asking for the ...
0
votes
0answers
28 views

Cannot connect to OpenSSH when compiled with the gcc option: -finstrument-functions

I want to make custom traces of sshd. So, I have added the source file ptrace.c from here. This file enables to trace function calls (but this is not the subject of my question). So, I have modified ...
2
votes
1answer
42 views

update openssh and openssl on solaris

I got a nexenta system, I updated openssl to 1.0.1j, which I compiled from source code. I updated openssh to 6.7, from source code as well, and I get this: root@cteraportal:/root# openssl version ...
6
votes
2answers
256 views

Determine dynamically allocated port for OpenSSH RemoteForward

Question (TL;DR) When assigning ports dynamically for remote forwarding (a.k.a. -R option), how can a script on the remote machine (for instance sourced from .bashrc) determine which ports were ...
1
vote
2answers
443 views

Help updating OpenSSH to v6.6

My system is vulnerable to OpenSSH Wildcards on AcceptEnv Vulnerability, CVE-2014-2532. I have tried to update openssh to version 6.6 for centos but I can not get repository[sic] for that version. ...
2
votes
1answer
236 views

public key authentication without authorized_keys file

I have a lot of ssh public key logins on a Linux server, e.g.: Jul 25 11:41:01 host sshd[24594]: Accepted publickey for root from xxx.xxx.xx.xx port 33374 ssh2 This is strange for me since there's ...
0
votes
1answer
50 views

Specifying a random monitoring port with autossh

I have many reverse ssh tunnels and because monitoring ports can't be reused, I am trying to find a free random port for monitoring. Meanwhile I specified -M 0 and the forwards work great and in ...
2
votes
1answer
123 views

Is there a way to run a privileged command upon successful SSH login (not necessarily with shell or PTY)?

I'd like to run a privileged command upon successful SSH logins at the server's end. However, this has to be in the server configuration (sshd_config or anything else that cannot be manipulated or ...
5
votes
5answers
1k 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 ...
0
votes
0answers
15 views

OpenSSH: UseDNS is not enforced

I cannot get the UseDNS constraint to work. It is set to UseDNS=yes on the server running sshd. That server queries a local DNS server which is the authority for each host on the network. Each host ...
0
votes
1answer
322 views

Intermittent 'ssh_exchange_identification: Connection closed by remote host' error

While there are many questions on this site and others addressing this very issue, I haven't yet found one that seems to address what I'm experiencing. When trying to ssh a linux box from a MBpro ...
1
vote
3answers
198 views

Can't ssh to a machine

All of a sudden, I couldn't ssh to a machine to which I used to ssh earlier. Consider I am ssh-ing from A to B. Output when I run ssh root@ip_addr_of_B I get: Permission denied ...
3
votes
1answer
156 views

How to know which public key was used when someone used passwordless ssh login?

Say for some reason, there is only a "user" account on a shhd server. Everyone has his own private key to ssh to the server, as "user". Then, is there a way to see who is he (during or after his ...
0
votes
0answers
71 views

Problem with OpenSSH

I think I got an OpenSSH-problem with my Ubuntu Server 14.04.1. Let me explain my setup: For development, I use Git and Gitolite. I have 3 server: server A ( master-server for git-mirroring) ...
4
votes
0answers
850 views

Can't figure out why ssh_exchange_identification: Connection closed by remote host appear

At home, I have setup a Raspberry Pi with the latest version of Raspbian and with ssh enabled. I also use a Mac Book Pro with OS X 10.9.3. I use ssh pi@192.168.0.22 to do some work on the Raspberry ...
0
votes
1answer
2k views

What is the default idle timeout for OpenSSH?

I can't seem to find an answer to this simple question, which I need for some compliance documentation. On a default install of CentOS 6.5 (OpenSSH 5.3p1-94.el6), after how long of being idle will ...
2
votes
1answer
99 views

Only apply Match keyword to single Host in ssh config

I have a host which I ssh into. Sometimes I'm inside the same network, and can ssh directly into it, other times I'm outside it and I need to use a proxy. Because ssh via the proxy server is much ...
24
votes
4answers
22k views

What is the point of sshd “UseDNS” option?

I know what it does, but i don't know why. What attack(s) does it prevent ? Is it relevant for all kind of authentication methods ? (hostbased, password, publickey, keyboard-interactive ...)
18
votes
2answers
788 views

What's the purpose of the randomart image for user (not host) SSH keys?

The ssh-keygen generates the following output: The key fingerprint is: dd:e7:25:b3:e2:5b:d9:f0:25:28:9d:50:a2:c9:44:97 user@machine The key's randomart image is: +--[ RSA 2048]----+ | .o o.. ...
9
votes
3answers
2k views

Local, timestamped logging of all ssh commands?

How can I keep a local, timestamped record of all remote commands I use in ssh (command-line openssh client started through bash)? Requirements: Essential: 100% client-side without relying on ...
4
votes
2answers
263 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. ...
1
vote
1answer
1k views

ssh_exchange_identification: Connection closed by remote host on vnx machine (linux)

I changed the password of my linux machine . I was able to login for sometime and after that I am not able to ssh. I am getting the following error: ssh es4042cs -v OpenSSH_5.1p1, OpenSSL ...
3
votes
1answer
71 views

openSuse, new user cannot login

I am using openSuse 12.3. I have created a new user using: linux-amvn:~ # useradd -m -G users,dev -s /bin/bash -p pass123 harbir-PC The user harbir-PC is not able to login, when I try to log using ...
13
votes
3answers
16k views

How do I convert a ssh-keygen public key into a format that openssl PEM_read_bio_RSA_PUBKEY() function will consume?

I'm having an issue generating a public key that the openssl PEM_read_bio_RSA_PUBKEY() function can consume. I keep getting errors. Obviously I cannot simply use the ASCII string in the ssh-keygen ...
1
vote
0answers
48 views

How to get information from sshd about established remote tunnels

I have a server running on which from many different places people log on via ssh and open remote ssh-tunnels to other places behind different firewalls. Now I want to try to get an overview, which ...
1
vote
0answers
14 views

Why does wget return a HTTP 403 error to download openSSH pet? [duplicate]

I am trying to learn how I would get OpenSSH using the command line. I found a *.pet link on this webpage: http://puppylinux.org/wikka/OpenSSH which says: Installation Install an appropriate ...
2
votes
1answer
135 views

how to connect ssh 'with' specified port?

I know how to connect 'to' a certain port when ssh'ing. ssh user@remotehostip -p XXX but is there a way to establish a ssh 'with' a certain port? I mean, is there a way to specify the port which ...
4
votes
1answer
187 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 ...
1
vote
1answer
204 views

Compiling OpenSSH client or Dropbear for Android

I have an interesting problem. I'd like to use a private SSH key with my Android Terminal Emulator (jackpal.androidterm). I'd like to install the private key in a fairly-secure location and be able ...
2
votes
1answer
460 views

Are dropbear and OpenSSH host keys compatible?

The title basically says it all. But mind: host key, not the login key. And if they're not compatible out of the box, is there a way to convert between them - and what would be the steps in that ...
0
votes
0answers
57 views

Proxy from OSX laptop to debian server for web browsing

I want to setup a proxy from my OSX laptop (10.9) to a debian server via SSH, to browse the net via that server. The debian server has an openssh-server running, and I can login. I tried several ...
6
votes
3answers
703 views

How to prevent “Last Login:” message from showing up when using sftp?

In Ubuntu GNU/Linux 12.04, I have a user johndoe that is part of an sftponly group, set up to sftp to a chroot jail using Subsystem sftp internal-sftp Match Group sftponly ChrootDirectory %h ...
2
votes
2answers
2k views

check if latest openssh patch provided by RHEL is installed

We have encountered a security threat in one of our RHEL servers which says the SSH server is configured to use Cipher Block Chaining. As far as I know, the RHEL systems provide security updates ...
3
votes
1answer
633 views

Generate own (stronger) RSA host key for OpenSSH?

I would like to replace the default 2048 bit host key generated when installing OpenSSH or starting it the first time with one of 4096 bit length. This leads to two questions: Does OpenSSH allow ...
1
vote
2answers
114 views

using ssh-agent

I have my desktop in the office. When X starts, ssh-agent starts automatically. I have to add my SSH key once, at the beginning, and then I can use ssh without having to enter my password each time. ...
0
votes
3answers
1k views

How I Determine The latest OpenSSL patch is installed?

This post is about applying the latest patch for OpenSSL to protect our port 443 web traffic, not using ssh to log into these systems. I went and obtained the lastest OpenSSL tarball source patch ...
1
vote
0answers
854 views

Force ssh to always use SSH_ASKPASS

I want to force ssh to always use the program specified by SSH_ASKPASS. In my case the program is just a bash script returning the passphrase. The problem is, as the ssh documentation says: If ...
1
vote
0answers
227 views

SSH to Windows 7 with cygwin openSSH freezes when remote conection [closed]

When I SSH into Windows 7(Cygwin) from a remote, the session freezes after few seconds or up to two minutes. This can happen while I'm typing and it can happen when idle. This is still happening after ...
3
votes
1answer
61 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. ...
3
votes
2answers
160 views

Denying “/opt/” access for SFTP Users other than particular dir

This is my first (newbie) post here in unix stackexchange. I want to use my WebServer (Debian) as SFTPServer giving access to particular employees. The dir structure is as follows under root: ...