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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Does SSH authorized_keys violate the principle of “re-authenticate before password change”?

It is generally accepted that password change mechanisms should ask the user for their old password (e.g. OWASP) The reason being that an attacker who has temporary access to a user's session (be it ...
10
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2answers
587 views

SSH connection attempts from China show different key; is China doing a MITM attack on SSH traffic?

I have a server located in the USA and SSH to it from various places around the world. When I SSH in from a computer I have never used before, I'll see something like this: The authenticity of host ...
4
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2answers
347 views

In there any point in passphrase-protecting an SSH private key that is used by a service account?

On my Linux machine (Alice), I am setting up a service account with an rsync cron job that will synchronise some files with a remote host (Bob). Obviously, I would want to make the rsync secure by ...
5
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3answers
506 views

Is piping a `ssh-agent` signed message as a password secure?

There's an encrypted filesystem on a server I ssh into using public key authentication. Since a forwarded ssh-agent can deterministically sign a message (see also the ssh-agent protocol section ...
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3answers
2k views

Is a passphrase-protected SSH private key susceptible to a dictionary attack?

If I have a passphrase-protected SSH private key, AND if this passphrase is sufficiently random and long (say, 20-, 30-, 40-characters long, or even more!), AND if I make this private key of ...
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1answer
54 views

Should statically-linked server binaries (daemons) be deemed more secure? [closed]

For a long time I've pondered this question. I am aware of the benefits and downsides of dynamic libraries (shared objects), including the infamous article by Drepper. All other things being equal, ...
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2answers
149 views

Creating port-specific SSH authentication for the same user

I have a Linux server running SSHD and would like to know if its possible to configure it, such that from within the LAN you only need a RSA key to authenticate (on port X), but from outside the LAN ...
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0answers
56 views

My server has been brute forced what now? [duplicate]

I have installed a raspberry pi for fun at home. I opened the port 22 and this morning I was concerned about someone brute forcing my server. I ran this query : cd /var/log;zgrep ssh auth*|grep ...
26
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1answer
3k views

Is all data sent over SSH encrypted?

When you are connected to another computer over SSH, is all data transferred between the two computers encrypted? Or is any data sent in plaintext or any other "easy to intercept" format?
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1answer
83 views

Simple way to protect ssh against man-in-the-middle attack? [duplicate]

If a narrow, trusted channel is needed (for example, there is an usb key to take data between the machines), it is okay. Although SSH will throw a big error if it tries to connect to a server ...
7
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2answers
540 views

How are two systems able to set up a secure SSH tunnel over a public connection?

As I understand it, when two systems create a secure SSH tunnel, the first step involves communicating the 'guidelines' for the encryption of that tunnel. If an third system is able to listen in on ...
3
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3answers
105 views

What benefit is there to adding a password to your SSH key?

If you run the following command on a Linux/Unix machine, among other things, you get a prompt for a password: $ ssh-keygen -t dsa Enter passphrase (empty for no passphrase): What does adding a ...
3
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1answer
173 views

SSH MITM attack underway

UPDATE: The source of this problem has thankfully turned out to be a buggy mobile SSH client used on 2 different devices not a MITM attack. However, I'd still appreciate a full answer to the original ...
3
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2answers
118 views

security via chsh

I am developing a program that I want people to be able to connect to and use via ssh. I've decided a simple way of doing this would be to create an account for them on my linux server, and change ...
2
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2answers
246 views

Is HTTPS as secure or more secure than SSH if both have an IP address whitelist?

I'm wondering whether an HTTPS API endpoint would be as secure as or more secure than SSH. API Endpoint The API endpoint would require HTTPS The API authentication would use a POST'd API key. The ...
2
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1answer
92 views

Security Implications of a ssh proxy vs ssh tunnel via a box I don't own

In order to access my desktop or the hpc cluster at my university, I need to go though an intermediary server managed by the university. Currently I use the "netcat method" (ssh -W) to access the ...
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0answers
179 views

SSH PermitLocalCommand Security

After a quick search, I haven't been able to find lay risk assessments of the PermitLocalCommand option in ssh. Are there known vulnerabilities that allow arbitrary code execution on the local host ...
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0answers
42 views

Pwn Plug like tunneling suite

Is there some sort of a (free) SSH tunneling suite like the one on the Pwnie Express' Pwn Plug (R2)? It has SSH over HTTP, DNS, ICMP, and other covert tunneling options and uses BackTrack 5 as a SSH ...
5
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5answers
2k views

Encryption laws in India — is it allowed to use ssh and VPN?

I have a very similar question to the one asked here (regarding Iran). However, I would like to use ssh and vpn while being in India. I found already this survey of cryptographic laws but I don't ...
0
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3answers
53 views

Restrict access to admin area by checking SSH connections

Assuming that the users have dynamic IPs (so I can't whitelist) and that setting up a VPN is not an option, is it a valid approach to restrict access to an administration area by only allowing IPs ...
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0answers
116 views

SSH using pre-existing session (symmetric) keys

Is there at present a way to open a SSH connection using pre-existing symmetric session keys? In other words, if I create a list of symmetric keys can I send that list to the recipient on a CD or USB ...
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0answers
67 views

Central Authentication Server

I have many client devices that I need to reverse SSH tunnel into. I am finding that managing all these certificate files are becoming cumbersome. I am looking into a centralized authentication ...
6
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4answers
9k views

Secure use of psexec or better alternative to it

I want to remotely start VMWare virtual machines (I own VMWare Workstation) and to this end I need to execute on host something like "vmrun -T ws H:\VMWare\VM1\VM1.vmx nogui" with user desktop ...
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9answers
3k views

Can IP address be a component of 2-factor authentication?

I have a bunch of Linux machines that I wish to administer over the Internet. I currently use SSH keys, but have been advised to use 2-factor authentication. SSH Keys are something you know. Is an IP ...
9
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4answers
3k views

Do I need to worry about my SSH keys if my system was vulnerable to Heartbleed?

So I'm getting conflicting information from members of my team. The premise is, if an attacker can keep requesting 64 kb chunks of memory from my server, they could get the entire memory footprint of ...
0
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1answer
1k views

Use SSH config file with Putty [closed]

I'm using SourceTree (a Git GUI) which uses PuTTY as SSH client. I need to push some code into a repository for which I need to tunnel through SSH to do so. The trouble is, the repository and SSH ...
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1answer
141 views

Most secure SSH server [closed]

Which SSH server (compatible with Debian Wheezy) has the fewest (if any) exploitable security bugs?
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2answers
505 views

How secure is OpenSSH on FreeBSD?

In a discussion about the recent OpenSSL information disclosure vulnerability, the subject of OpenSSH being vulnerable came up. While OpenSSH is not vulnerable due to the problem lying in the TLS ...
7
votes
1answer
256 views

SSH: benefits of using hashed known_hosts

What are the benefits of storing known_hosts in a hashed form? From what I read, it is supposed to protect the list of servers I am connecting to, presumably in a scenario where my account has been ...
0
votes
1answer
158 views

Python SSH vs SSL? [duplicate]

I read the What is the difference between SSL vs SSH? Which is more secure? , and it mentions there is the possibility they can be affected by similar attacks. Now that the heartbleed thing is out, ...
0
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1answer
205 views

Outbound Port 443 Open but Not Allowing SSH [closed]

My college wireless network has a firewall blocking all outbound ports except 443 and 80. The wired network, however, has none of these restrictions. I can connect to HTTPS sites (obviously). On my ...
4
votes
3answers
4k views

How does SFTP function without a manually generated public/private key pair

I am learning about SSH and how to use it to secure file transfers and commands between a windows machine and a Linux server. Everything that I have read so far indicates that I need to use an SFTP ...
2
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1answer
153 views

Is it possible to use SSH agent for generic data encryption? [closed]

Is it possible to use running SSH agent to decrypt some data (supplied as a string or read from file)?
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53 views

Considerations when implementing a key based SSH-like auth scheme

I have a SMTP server where all the users (for an unrelated reason) will have public keys tied to their username and registered with the server. I want to add a non-standard extension that uses these ...
6
votes
1answer
421 views

Harden a server against mass SSH DoS attacks

How can a Linux server be protected against an attacker that tries to open a large number of SSH sessions (probably trying to brute force a password) that no ports remain to be able to legitimately ...
0
votes
1answer
297 views

My machine is hacked by someone and used to attack others via ssh, how to stop it? [duplicate]

I host my personal website on digitalocean. Nowadays, I received many abuse complaints which finally make them shutdown my machine. I feel really sad and angry. Someone complaints that my machine is ...
2
votes
1answer
434 views

Lots of failed outgoing sshd attempts. Am I hacked?

For the last two days I've been seeing lots of lines in my /var/log/auth.log that look like: sshd[xxxxx]: error: connect_to 0.gravatar.com port 80: failed sshd[xxxxx]: error: connect_to ...
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3answers
269 views

Server side SSH keys compromised

I'm interested in knowing what could be the consequence if the server side SSH keys of a host were compromised. The situation would be: An attacker manages to read the SSH private keys of the ...
2
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4answers
389 views

Is there a way to keep sudoers from editing stuff in /etc/ssh/sshd_config?

I have root login disabled in SSH and I want to be able to eliminate the possibility of a sudo user editing the /etc/ssh/sshd_config file and enabling root ssh login. Is this possible?
0
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3answers
195 views

Is all RSA encryption now considered insecure? (Notably SSH and SSL)

Some of the leaks which emerged during/after Snowden concerned the fact that the NSA was paying the organization behind RSA a lot of money in order for them to systematically weaken the encryption by ...
3
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3answers
276 views

Is it advisable to fully record terminal interaction for incident response?

We are going to be using a jump box to serve as an SSH bridge to our production systems. Assuming that operators are actually logging in to a shell on the jump box and assuming that it is possible to ...
5
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3answers
143 views

Best approach for restricting remote ssh session

Using the following files, I have attempted to restrict the SSH remote login. Having lack of knowledge in linux environment, I don't know the drawbacks and vulnerabilities between the following ways. ...
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2answers
71 views

How to setup cronjobs that do scp without saving the .pem file on either of the machines

I have the following situation and want to know what are the best practices to do such things without exposing myself to security issues I have two servers both use the same private key for login. ...
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votes
1answer
981 views

Open ports and SSH Tunneling to shared hosting

I know your time is valuable so I'm not waiting for specific answers to my situation. I don't mind reading documentation, so pointers to something that converges would be greatly appreciated. I don't ...
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0answers
95 views

Test S/KEY support for PCI compliance - CVE-2007-2243

In order for our business to be PCI compliant, we need to prove that we are not vulnerable to CVE-2007-2243. This states that: OpenSSH 4.6 and earlier, when ChallengeResponseAuthentication is ...
4
votes
3answers
1k views

In what ways does increasing SSH host key length increase security

I have read on a few guides on "how to secure SSH servers" that it is a good thing to increase ServerKeyBits from the default of 768 to 2048. Most of these guides seem to be for the entry ...
1
vote
2answers
451 views

SSH Security allowing only certain users to connect to the server [closed]

I have set up a remote ssh server on the cloud. I am newb at these things and have managed to bypass the required firewall using SSH. Now I plan on giving the access to only 2 more friends of mine so ...
16
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2answers
5k views

stronger encryption for SSH keys

I configured my server to encrypt user passwords using 500,000 rounds of SHA-512. The question is, how does the standard AES-128-CBC encrypted SSH private key stack up to that, provided the same (or ...
3
votes
4answers
218 views

Are there Ciphers designed to be slow?

To safely store a passwords, it is better to store them hashed using a hashing function designed to be slow like bcrypt. The goal is to trump brute force attacks. Are there any ciphers slow enough to ...
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2answers
303 views

How do I determine where ssh login attempts are coming from?

We had been testing an AWS instance accessing an internal Ubuntu 10.04.3 server, so had modified our firewall to allow all ports from that specific IP address to the server. We then released the AWS ...