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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7
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2answers
81 views

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 ...
0
votes
2answers
299 views

Using given RSA private key without the associated public key

I'm currently following a small game to get more familar with linux and security and got the following task: The password for the next level is stored in /etc/bandit_pass/bandit14 and can only be ...
6
votes
3answers
679 views

Is it OK to use the same password for a Linux login and the SSH private key?

I want to remotely log in to my Linux server with SSH. Public/private key authentication is more secure than password authentication, so I have disabled password-based authentication for SSH on my ...
3
votes
3answers
796 views

I want to roll my personal cloud hosted Password Manager using pass. How secure/insecure would this be?

I've come to the conclusion that I need to up my security. I currently have a dozen memorized passwords I use for every device and website. I'm against KeePass/Lastpass due to having to trust they ...
2
votes
2answers
58 views

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 ...
3
votes
4answers
43 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 ...
4
votes
1answer
100 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 ...
19
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2answers
23k views
0
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1answer
21 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?
33
votes
6answers
2k views

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 ...
0
votes
1answer
59 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 ...
0
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1answer
43 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 ...
6
votes
1answer
83 views

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?
4
votes
1answer
210 views

Does RekeyLimit property in sshd_config enforce re-keying / key re-exchange?

I have set the RekeyLimit property in sshd_config and tried to perform a SSH. However, I could not see rekeying happening in the verbose logs, all I see is the log message below at the start of the ...
1
vote
3answers
106 views

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 ...
20
votes
2answers
5k views

Security Concerns with X11 Forwarding

What are some of the security concerns and reasons either for or against allowing X11 Forwarding. I have generally taken an approach of not allowing it under the blanket guise of security. Recently, ...
2
votes
0answers
744 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 ...
1
vote
0answers
28 views

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 ...
5
votes
1answer
131 views

System breach or OpenSSH glitch?

The system runs a SSH daemon, and a nginx web server, both ports being open to the internet. We are part of a university so our ports are forwarded from the main router to the intranet. At about 19:...
3
votes
1answer
190 views

Why does the server ssh public key not look like the key in client known hosts?

From my naive understanding of ssh, the server shares its public key ( /etc/shh/ssh_host_rsa_key.pub ) with the client, who then adds it to the list of known hosts ( /user/.ssh/known_hosts ). So, I ...
1
vote
2answers
12k views

SSH Bad Protocol Version Identification String- What is it?

I need some help identifying some Bad Protocol version identification errors from our server. We're getting the following: sshd[xxxx]: Bad protocol version identification '\200\342\001\003\001' ...
3
votes
1answer
45 views

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 ...
9
votes
2answers
528 views

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 ...
-4
votes
1answer
45 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.
3
votes
1answer
39 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 ...
-3
votes
0answers
72 views

Alternate SSH authenticate

I was doing a little bit of research on how SSH actually authenticates a user and different things. And I came across a document which nicely explains how SSH authentication works which is something ...
3
votes
3answers
202 views

Can you use ssh for secure inter app communication on the same device?

I use ssh to get an encrypted connection between servers and local machines all the time. It's fast, it's secure, and there's a way to do it in nearly every system programming language that I've used ...
1
vote
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 ...
20
votes
1answer
10k views

Should I publish my public SSH key with user@hostname at the end?

In ~/.ssh/id_rsa.pub my public key is stored as: ssh-rsa magicmagicmagicmagic...magicmagic username@hostname When publishing my public key, should I include the username@hostname bit? Can I ...
4
votes
1answer
221 views

Putty settings - Protocols and Algorithms to warn about

I specify "Putty" as otherwise I feel the question would be too broad. What are the algorithm (as of March 2016) that one needs to be warned about (ie, those that no longer are considered safe enough)...
43
votes
1answer
5k views

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 ...
0
votes
1answer
80 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 ...
24
votes
3answers
17k views

ECDSA Keys Changed, SSH insecure now?

I'm running some non-critical Ubuntu servers in my dorm room in college. Turned them off before break, come back, SSH in, and get a warning that the ECDSA keys have changed. It looked pretty much ...
6
votes
1answer
362 views

SSH ciphers, MAC and key-exchange (and pen-tests thereof)

At work we've been trying to move our external-facing services away from a policy of inclusivity (where we tried to accept as many people as possible) to a more security-focused setup. The first step ...
2
votes
1answer
240 views

There might be a man in the middle attack against my server

I have a little $7.20/y VPS, and the fingerprint for the ECDSA key has changed three times on me. This time, it happened shortly after I reinstalled the server (same day, in fact.) I always disable ...
1
vote
2answers
65 views

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 ...
2
votes
1answer
47 views

Can a user verify the quality/safety of pregenerated SSH moduli parameters?

Many tutorials about how to mitigate the Logjam recommend regenerating Diffie-Hellman moduli. This is a resource intensive operation, especially for high-bit groups. This made me think if it made ...
1
vote
1answer
77 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 ...
0
votes
1answer
44 views

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 ...
1
vote
0answers
44 views

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 ...
1
vote
0answers
26 views

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 ...
0
votes
0answers
13 views

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 ...
62
votes
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....
2
votes
1answer
47 views

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 ...
0
votes
4answers
138 views

Running SSH on a different port vs adding the port number to a password

So, a pretty typical piece of advice is to run SSH on a high port number, thus decreasing the chances of it being attacked. The thing I have always wondered about though is that it seems more secure ...
0
votes
0answers
15 views

Identify if Debian PC reachable with SSH is infected [duplicate]

I am operating a credit-card sized PC with Debian on it. For some time (before taking care of it) it was reachable with SSH over port 22, simply using root as username, and no password. How can I ...
51
votes
4answers
20k views

What is the best practice: separate ssh-key per host and user VS one ssh-key for all hosts?

Is it better to create a separate ssh-key for each host and user or just using the id_rsa key for all host to authenticate? Could one id_rsa be a malpractice for the privacy/anonymity policies? ...
23
votes
4answers
21k views

Possible to use both private key and password authentication for ssh login?

It seems that they are mutually exclusive, as disabling one gives me the other, and vice versa. Two-factor auth for my ssh servers sounds really nice, so is there any way to accomplish this?
0
votes
1answer
243 views

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 ...
0
votes
1answer
35 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 ...