SSH (Secure shell) is a protocol for secure communication between computers to execute remote commands, transfer data and tunnel TCP connections.

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Why should you generate SSH keys on client devices?

Most tutorials for setting up SSH recommend generating the keypair on a client machine. Why exactly is this? Assuming your communication lines are not compromised, and you delete the private key from ...
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60 views

Is a password protected SSH key necessary on an encrypted system?

I have a laptop running Linux encrypted using dmcrypt. To use git, I just created an SSH key, but did not password-protect it. Since my hard drive is already encrypted, is there any benefit to ...
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Question about something found in pcap [on hold]

Looking at a pcap, an SSH scan was performed and in the pcap, there was a line that said "Linux 2.6, seldom 2.4". I'm assuming linux 2.6 is the older version of linux, but what is seldom 2.4 and how ...
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1answer
64 views

Which host key algorithm is best to use for SSH?

When you first connect to an SSH server that is not contained inside your known_hosts file your SSH client displays the fingerprint of the public key that the server gave. I found from this question ...
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Restricted bash circumvention via SSH command execution [migrated]

There seems to be a trivial rbash circumvention, whereby an SSH user can simply request that bash be executed. The environment consists of a restricted $PATH, with a tiny subset of commands available....
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Should a VPN user be allowed to bypass a SSH jump host?

I am setting up a computer network for software engineers. I currently have all SSH connections run through a jump / bastion host, with access to production servers requiring SSH agent forwarding. ...
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43 views

Secure channel without identifying information

Is there a way to establish a secure channel like ssl or ssh without leaking identifying information to an observer, especially the server's public key? Are there real implementations?
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28 views

Use Public Key or Password and PAM verification code

So I've been reading more and more about how (relatively) easy it is to have your Ubuntu server compromised and suffice to say have become a tad paranoid by this fact. I've setup Multi Factor ...
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1answer
42 views

ECDSA: Why do ssh-keygen and Java generated public keys have different sizes?

I am using ssh-keygen -t ecdsa -b 256 which generates this for the public part: ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBNaHgNjXShzF/hmZOuhTCCsokgpSCyFohETHT4+OQMxW5g+...
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33 views

Minimalistic operating system for enhancing ssh security?

As we know, although the SSH protocol is sound in theory, it can be compromised when the implementation is faulty or the underlying operating system is compromised in other ways that indirectly ...
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How to check if an SSH private key has passphrase or not?

Let's say I have access to the private portion of an RSA key-pair. How can I check if this key has associated passphrase or not?
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When using SSH agent forwarding, how can we sniff the traffic of the SSH session? [duplicate]

Related: MITM of the SSH connection? From: http://www.unixwiz.net/techtips/ssh-agent-forwarding.html#fwd Question: How can the "server" sniff the traffic of the "homepc"'s SSH session to server2? ...
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72 views

MITM of the SSH connection?

We connect to the servers via the "FOOBAR" machine. desktop -> FOOBAR(bar.com) -> server FOOBAR can log our SSH connections, what we type, etc. We log in via the following command: ssh -A -t ...
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1answer
46 views

Making SSH warn of MITM monitoring

I am a bit of a newbee with SSH+security, so I'm not sure if the assumptions in the following question are entirely correct... I am in a hotel which uses zscaler.com to monitor its guests' internet ...
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3answers
110 views

Where to find current information on cipher suite strength?

I am hardening the configuration for my /etc/ssh/sshd_config and have a few choices for Ciphers: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128, aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,...
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1answer
211 views

Should I worry about GitHub using IP addresses that are described as having an unknown host?

Today, I got a message while doing a git push, saying Warning: Permanently added the RSA host key for IP address '192.30.253.112' to the list of known hosts. It seems as if it's consistent with ...
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4answers
49 views

Is there a safe way use a private key from a shared server?

I am working remotely on a school server via SSH from home. I would like to access a private GitHub repository from the remote system with SSH. If I create a new public/private key pair on the remote ...
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2answers
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Why use dedicated SSH keys for different hosts (like GitHub)?

I recently discovered github-keygen, a tool that helps you set up SSH for use with GitHub. One of the things the tool does is to create a new SSH private key dedicated to GitHub exchanges; the manual ...
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30 views

Does Dropbear support SSH key revocation?

I'm using Dropbear as an SSH server in my embedded system. I want to know if Dropbear supports SSH key revocation? If yes, how I can do it?
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74 views

ssh-keygen: How is the seed generated?

How is the seed for ssh-keygen generated? I expect it will take information from /dev/random and request supplementation with system activity if we have insufficient random bits. An Instructor ...
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1answer
47 views

How to configure SSH public key per user?

I have an OpenSSH server running and different users can log into it with different privileges. I know you can enable public key authentication and place all the allowed public keys in the ...
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Why don't PGP and SSH keys see more widespread use as a second factor when authenticating?

One of the major up-and-coming MFA methods is U2F, which relies on an initial key exchange and challenge-response mechanism. It's a relatively new protocol, and is only starting to see more ...
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1answer
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Is there a way to know if a server is using ssh public key or password?

I am wondering is there a way for an attacker through finger printing to find out whether a server is using public-key versus password authentication method for establishing an SSH connection?
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3answers
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How do SSH keys work? [duplicate]

I'm just looking for a simplified explanation of the mechanics of SSH authorization. Basically, what makes it better then a really long password? And how does the public key play into things? I ...
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Enabling specific access with iptables on Debian

I am running a Debian server that hosts several Docker containers but also works as my router and internet gateway. I am having trouble getting SSH access from outside (specific ipaddresses) working ...
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Why SSL uses a third party (certificate authority) yet SSH does not [duplicate]

SSL operations require the use of a trusted third party -- the certificate authority to verify a public key presented by a server to a client. SSH on the other hand relies on the client having the ...
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Verifying SSH fingerprint of a public server

I have read somewhere that servers which have SSH access for users in the public can have their public key posted publicly (e.g., on a website), so that people who access such a server using SSH can ...
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1answer
52 views

Using SFTP or SSH [closed]

If both SFTP and SSH both runs on same port #22. Then in which case do we need to use each of them separately.
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1answer
59 views

Smartcard authentication SSH remote client

I want to use smartcard authentication for my SSH sessions. Now sometimes I want to use a ssh client within a ssh session. So this situation: My desktop computer with smartcard has a ssh session to ...
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1answer
19 views

What should I watch out for when using pam_ssh_agent_auth?

I got tired remembering passphrases for my SSH logins and heard about pam_ssh_agent_auth. Unfortunately I hadn't found any security audit of it and I don't know enough low-level details about SSH to ...
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1answer
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I have the ability to run arbitrary Python code on the 'apache' user. What damage can I do?

So, due to bad programming on the part of one of my former colleagues, one of our internal web apps allows the user to upload and run an arbitrary Python file. This recently came to light via an ...
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1answer
88 views

Robots trying to login to Azure VM when SSH port is closed in manager

I have many robots trying to do SSH login in a Azure VM. In the resource manager SSH is disabled but attacker IPs are public, as you can see below, where I copy a log for auth.log (I have an Ubuntu ...
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OpenSSH DOS exploit proof of concept [closed]

For some research I'm looking for a working DOS exploit for OpenSSH. The OpenSSH version, vulnerable to the exploit is irrelevant. The only requirement that I have is, that the exploit should work for ...
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What could cause “Bad packet length” with sshd?

I am getting a lot of failed ssh login attempts by one specific IP-Address with a strange error. I cannot make sense of the information found through google, so I was thinking it is maybe a new form ...
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1answer
87 views

How important is a static IP address when authenticating with my server?

I am looking to move my business into a small office. I have found somewhere very suitable but unfortunately they cannot provide a static IP address. Currently, to connect to my server from home I ...
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797 views

Can SSH tunneling over DNS tunnel work in China to use free WiFi at airport?

I have followed a tutorial here: http://ebnj.net/sshoverdns/ This tutorial tells us how to carry all internet traffic via DNS tunnel if your airport enables no-limit outgoing DNS. This guides us to ...
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Connected to my server through VPN. Should I change my key?

I am using an SSH key to connect to my server (I've got Pageant to authenticate my key) and I forgot that I had the VPN on so I connected to the server (SFTP) while I was on it. Should I change my ...
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Make my SSH I treat like VPN more anonymous [closed]

I have a VPS (although I could easily upgrade to a dedicated server) which I use as a "poor man's VPN" by tunneling through it. My aim is to improve this server so anyone attempting to track me has ...
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SSH certfificates generated on server user-creation + login scheme secure?

I'm sketching on a way to harden and automate server login using ssh-keygen with certificates where certificates, valid for e.g. 1 week, are generated on a trusted server and can be used to both ...
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Attacker's Potential Scope of Dmg if He/She can SSH into Android Phone

I've recently started researching the ability to SSH into an Android device. From what I've seen, this is a figured out challenge, which makes me wonder how much damage an attacker could do. Let's ...
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1answer
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AuthorizedKeysCommand of sshd_config getting called twice

AuthorizedKeysCommand paramter present in the file /etc/ssh/sshd_config. The bash script which i called using this command is getting called twice. The config file is as follows #RSAAuthentication ...
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1answer
109 views

Hidden service security SSH

Pretend I have a Tor hidden service. For ultimate security I would firewall the internet entirely, except for Tor, to try to reduce IP address leakage and other security risks. My problem is how ...
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1answer
37 views

Getting Operating System Username using MySQL SQLi

Suppose I have a website which has SQL injection vulnerability and I got the database schema etc. Is there any means by which I can get the operating system username or the SSH username? Asking from ...
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1answer
83 views

What is the best practice to secure an unattended Raspberry Pi?

I'm working on a project which involves mounting a Raspberry Pi on a self-moving vehicle. I'm looking for the best way to encrypt the Pi (entire file-system, swap, etc.), with the minimum possible ...
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38 views

What can possibly happen to a public SSH server?

I'm writing a console emulator in JQuery, which will connect to a server through SSH and dynamically send commands (through AJAX) and receive output. Basically it will be a remote ssh console on a ...
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5answers
5k views

Does FTPS (FTP+S) offer better security than SFTP on the server side?

I had an exchange with some third party sysadmin yesterday regarding the setup of a file transfer interface between our servers. I suggested using SFTP because our application has good support for it....
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5answers
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Advantages to killing sessions after 5 minutes?

I'm dealing with a server that isn't mine to configure. Something somewhere between me and this server kills any connection after 5 minutes if no traffic passes between the two machines. This includes ...
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Which ssh exploit works by changing the user name in the middle of the process?

Every few hours, I get a few of those in my server logs: sshd[...]: Disconnecting: Change of username or service not allowed: (httpd,ssh-connection) -> (http,ssh-connection) [preauth] sshd[...]: ...
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My server was hacked and I am asked to pay to recover my files

Today I got a message when I logged on the server: Hi, please view: http://pastie.org/private/tlixxvclirxmut6djqyacq for further in ...
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SSH Tunnels for Securing IoT Sensor-to-Server Connections (Many to One)

All, How bad (or good) an idea would it be to utilize SSH tunnels from my sensor gathering remote computers (imagine an "industrial" Raspberry Pi-like device w/ Linux) to my centralized server (also ...