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Questions tagged [ssh]

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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What's the difference between SSH tunneling and login into the same SSH server and executing commands?

Consider these 2 scenarios. (1) Let's say I login into an SSH server named A normally using ssh [username] @ [IP address of A]. And now I connected to another server named B which is accepting ...
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Import ssh keys into gpg (openpgp) as mutliple authentication subkeys?

I have successfully converted ssh keys to gpg primary keys and then converted them to authentication subkeys using pem2openpgp. Unfortunately there is only one primary key and only one authentication ...
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SSH Authentication with Fido2 / Yubico Security Key [migrated]

I was wondering if it is possible to use FIDO2 to authenticate against an ssh server. There are many tutorials explaining how to use GPG and the newer Yubikeys for ssh auth, but i do not find any ...
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1answer
50 views

Can a SSH jump host act as MITM?

Let's say, for example, a company has a "centralised" SSH bastion/jump host on an untrusted server (e.g. a virtual machine in "the cloud"). Meanwhile the corporate/customer/whatever network(s) have ...
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100 views

How do I get back to a Meterpreter shell after backgrounding it?

Curious if any of you have an answer to this Metasploit question. It's an issue of a Metasploit session within another Metasploit session. In this lab I'm doing, I need to compromise a machine (10.10....
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3answers
142 views

Is it safe if SSH and HTTPS server share the same RSA/DSA keys?

I'm configuring an ssh server for an embedded device. This device already has an x.509 certificate and a pair of public key and private keys stored in it that is used for its HTTPS server. Is it safe ...
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170 views
+50

Are the sha1 hashes used by common ssh configurations insecure?

I got an automated PCI security test result that checked various server configurations. The automated test determined the server to be unsafe due to the use of sha1 algorithm in some elements of the ...
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281 views

Is PuttyGen secure?

I'm using PuttyGen to generate ssh keys for various windows computers. It requires a lot of manual user input, specifically in the form of swirling the mouse around in the window pane. I understand ...
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1answer
67 views

Is there any harm to writing a short plain-text string to authorized_keys?

I have a CFN template where I'm seeding an authorized key for testing via paramaters, through a build server. If this value is not provided by the build job, it defaults to a short, plain text string, ...
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1answer
88 views

Why does Cain and Abel downgrade SSH version 2 to v 1.51?

I am developing a lab exercise with Cain and Abel and want to know why it is necessary to downgrade SSH before attacking. Identification phase The server sends to the client an identification ...
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I think my ssh server is under attack and it's really trecherous [duplicate]

I'm new here so please bear with me. And thanks for the opportunity. This is an awesome resource. For the past few days, my ssh server (it's a small convenience I run just so that I can access my ...
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1answer
84 views

Should I treat my SSH username like a secret?

I'm trying to automate the deployment of my blog. Most CI providers are using virtual machines/Docker containers with Linux, so I'm learning about shell scripts and SSH now, which is all new to me. ...
3
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1answer
38 views

Providing access to Git repo behind a Firewall using Certs/Keys for Authentication

We have a Git repo sitting behind a firewall. As I see it, there are two ways of authenticating/accessing the Git repo: Add a Reverse HTTP Proxy in the DMZ that communicates with the Git repo. This ...
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1answer
51 views

Please may I know why I am getting this Sshd log

why I am getting this sshd log Feb 1 13:07:57 sshd[6453]: Failed password for root from 193.34.22.63 port 28980 ssh2 Feb 1 13:08:26 sshd[6897]: Failed password for root from 91.205.189.15 port 48155 ...
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2answers
94 views

Prey vs SSH for remote wipe of stolen laptop under Ubuntu

I have to be able to wipe a stolen laptop remotely (contractual obligation), and the only product I found that supports that on Ubuntu is Prey Project. (Also appears in some other stack exchange ...
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1answer
95 views

Sending Private Keys, does it make sense?

There's some logic that I'm not following whenever my organization sets up VMs for SSH access. Perhaps someone can help me understand. Our process is currently as follows Generate Keypair on Linux ...
45
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3answers
9k views

Does a fake SSH server have any purpose security-wise?

I stumbled upon this sshesame software which appears to imitate an SSH server accepting any username/password, only instead of executing the subsequent shell commands it logs them in a file. What I ...
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SIEM: Correlating remote logons to associate origin and target user

How is it possible to correlate or detect user logons eg via ssh/rdp to associate the origin user and target user. My use case is to know who actually (personal/identifiable) used a technical account ...
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1answer
37 views

Is it safe to browse the web through an SSH SOCKS5 connection to an untrusted proxy?

I have established an SSH tunnel to an untrusted machine: ssh -N -D 12345 john@example.com Next, I set up Firefox's connection settings to use the SSH tunnel by setting the SOCKS host to 127.0.0.1, ...
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1answer
80 views

How do these attackers find my IP? [duplicate]

Recently, I have been reading a lot of my ubuntu log files (in /var/log/auth.log), and I can see that some IP addresses are actually trying to 'brute-force' their ways into my VM using SSH by testing ...
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1answer
78 views

Use GPG smartcard and gpg-agent to protect multiple SSH keys

I have a Yubikey acting as a GPG smartcard. SSH is configured to use the smart card socket for authentication, and authenticating with the GPG key with Authentication capabilities work fine. ssh-add -...
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57 views

SSH-1 key length

What is the maximum size in bits of one SSH-1 key? 4096? I found some docs where this value is listed and others without limit
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1answer
103 views

Techniques used by highly sophisticated entities to snoop on VPN or SSH traffic?

It is mentioned in almost every where that very strong agencies, and governments are able to watch the online activity of the people. Aside from techniques like attacking computer networks, and ...
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1answer
141 views

Risk involved with using SSH for CTF challenges? [duplicate]

I'm new to the INFOSEC scene and was intrigued by the concept of CTF challenges. I was hoping to get started with OverTheWire.org which requires you to SSH to their server to complete the challenges. ...
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1answer
73 views

Why can I use 2 different private keys to connect to my SSH server storing only 1 public key?

On my server ~/.ssh/authorized_keys contains only 1 public key. However, I can connect to it using 2 different private keys. One private key looks like this: -----BEGIN RSA PRIVATE KEY----- ...
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2answers
7k views

How can SSH server know private key is incorrect if passphrase havent been provided yet?

I have server which I am accessing via SSH. I only allow the authentication to be made with private key. Normally when I login via PuTTY, I am first asked for username and then asked for passphrase ...
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1answer
121 views

How do I determine if an existing SSH private key is secure?

For an ordinary user, how would I verify that a private key file was generated using reasonably secure algorithms? In response to things like allegedly insecure ssh-keygen defaults.
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1answer
301 views

What are the best ciphers in terms of performance for SSH tunnel?

From a security standpoint, there are few good cipher options to use with SSH, such as ChaCha20, AES 128/256 GCM/CTR. As I understand (please correct me if I wrong), all of these offer pretty strong ...
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3answers
4k views

Is ssh with public key authentication, no passwords secure enough?

I have a web server set up and would like to connect to it from outside using Tor. The web server simply serves up a simple webpage that will act as an interface for a program running on the machine. ...
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5answers
434 views

Difference between SSH Tunnel / Proxy and VPN in terms of security

What benefits does a VPN have over just using a regular SSH Tunnel? I'm considering setting up OpenVPN on a server, but was wondering what benefits that would have over just using that same server as ...
4
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1answer
136 views

If my private key is password protected, then how is it used without asking me for it?

Relating to TLS and SSH. If my private key is password / passphrase protected, how is this then used automatically during TLS or SSH communication without asking me for the password?
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Using the same private key for both WSL-Ansible and Putty (or WSL-OpenSSH for that matter)

I use Windows 10 home on my PC and SSHing to up to 5 Linux IaaS machines with either Debian/ArchLinux as server environments. I use Ansible to orchestrate and continuously integrate and continuously ...
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1answer
54 views

How does the public key get authenticated during an ssh session

When using SSH, my private key is stored on my computer safely and my public key is given to the other party I wish to communicate with. I understand that the two keys are mathematically related, and ...
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1answer
25 views

Is it worthwhile to restrict SSH on home web server to local network? [duplicate]

First, some background: I have a web server (Linux) which I run from my house. I have a relatively small website, and have just set up SSH. While modifying the firewall, I had the choice to pick ...
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1answer
59 views

Looking for SSH key management tricks that apply to a large fleet of machines to reduce the 'trust of first use' attack surface?

If you have too many machines and you are nearly always asked about a host key when you connect, it leaves an opening that the first time you connect to a machine it's a security threat, but anytime ...
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1answer
88 views

Why are passphrases protecting GPG / SSH private keys needed? [duplicate]

SSH and GPG each ask for passphrases during key generation. GPG also (at least from my experience) displays warnings if one is not provided and asks for confirmation that no security is indeed ...
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2answers
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Possible to get sshd (openssh) to log the public key of failed key based login attempts?

As I understand sshd (openssh in my case) typically does/may log the fingerprint/hash of the public key of incoming connections which are attempting to authenticate via key. What I'm looking for is ...
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1answer
109 views

I think my raspberry was hacked, what should I do? [duplicate]

First of all, sorry if all of this seems a bit stupid, but my field of expertise is software development, not security. So, here is what happened. 1/ The breach I did something I really shouldn't ...
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Malware abusing SSH agent active keys

I am thinking about this lately a lot, so I wanted to get someone else's opinion. Let's say that I have an SSH key agent (e.g. Pageant or ssh-agent) running in background with loaded keys (keys were, ...
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2answers
122 views

How safe is it to allow key-based SSH access within LAN?

So this is my setup: We have a few machines in a LAN, used for computation, which me and my colleagues access from the outside with SSH. All our accounts on the LAN machines are managed and shared ...
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1answer
122 views

When first connecting via SSH to my server, the reported fingerprint does not match that given to me when I generated the SSH key

When I used ssh-genkey on macOS to generate the pair of key files (one named with .pub), that tool reported a SHA256 hash as a public key fingerprint. When first connecting to my server, a Digital ...
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2answers
55 views

Capture Response Attempting to Connect to Open SSH

I want to be able to attempt to connect to a host using password authentication and store the server's response in a variable. This is to see what hosts in my list accept passwords for their ssh ...
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1answer
162 views

Secure SSH host keys

I am trying to fix my SSH setup on Fedora and RedHat with ssh-audit. I managed to fix the ciphers and algorithms by setting KexAlgorithms diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,...
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1answer
55 views

SSH: Best practice for PublicKey Authentication from multiple Devices

I have a Server I want to access via ED2559 PublicKey Authentication. How would one do it so it is as safe as possible from multiple devices? Should I add multiple PublicKeys to my Server or should I ...
3
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1answer
918 views

How did a bug like CVE-2018-10933 (libssh authentication bypass) happen?

How did a bug like the recent libssh vulnerability come to exist? Exactly what is the nature and root cause of the bug? From libssh's website: libssh versions 0.6 and above have an authentication ...
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3answers
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CVE-2018-10933 - Bypass SSH Authentication - libssh vulnerability

Looks like CVE-2018-10933 was just released today and you can find a summary here from libssh here Summary: libssh versions 0.6 and above have an authentication bypass vulnerability in the server ...
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1answer
294 views

SSH over VPN blocked on certain networks

Why can I only access protected resources over VPN on some networks? Location | SSH to GitHub | SSH to private IP ------------------|---------------|------------------- On-campus Wi-Fi | ...
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1answer
111 views

Honeypot SSH connection attempts with no interaction

I am seeing a lot (>50% of total events) of connection events on a honeypot I have set up but there is no further interaction, no brute force, just a connect then disconnect. I'm thinking this is ...
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1answer
77 views

Why are SQL servers not attacked as frequently as ssh servers?

I have a server running with both SSH and MySQL accessible to the public internet. Both run on default ports (22 and 3306). The ssh server is attacked by bots all the time. This is the output of ...
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0answers
60 views

Could a running SSH server somehow fool connected SSH client to create a reverse port forward?

Let's be extra paranoid and assume that the SSH server my client is connected to, was "enhanced" so that every SSH client that establishes an connection with it, will be tricked into thinking that it ...