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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difference between public key and host key and security of host key

In SSH, what is the difference between host key and public key. Public key I believe that is part of private/public key pair, so, that anything sent by server(encrypted using private) can be ...
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37 views

Security of access to local network via VNC over SSH tunnel

I've just set up a Raspberry Pi 2 with the latest raspbian and installed some services. For remote access I've installed tightvnc server which I set up to only allow connections from localhost. I can ...
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Do GPG and OpenSSH use key stretching on their keypairs?

Both OpenSSH and GPG can generate key pairs which are stored as files in well-known paths inside the user directory. A passphrase is always asked for during the generation process, which is then used ...
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22 views

Choosing a cipher and MAC for an SSH connection

The cipher and mac selection according to this are in some sort of order in a config file. How do the client and server know that they are using the same ones though? Is this information exchanged in ...
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110 views

Is port forwarding inherently unsafe?

I had an argument with a person a few months ago when I proposed we forward port 12xyz to an internal SSH server. The target server was tied down in a manner similar to the one recommended by ...
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2answers
32 views

non-https winscp website

The whole point of WinSCP is to provide a secure channel between a computer and a server. "Secure" means that there is a possibility of an attacker that can view or modify bytes sent both ways. Let's ...
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75 views

How to deal with SSH keys in insecure environment

I am trying to find out a "safe" solution for the following situation. tl;dr how to keep things secure in an environment that is absolutely not? I work in a company where workstations are not safe ...
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63 views

RSA key generation: gpg vs openssh

When I generate RSA key for ssh (both server-side and client-side): dpkg-reconfigure openssh-server ssh-keygen the key generation is completed instantly. However, when I generate RSA key for gpg, ...
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SSH Public Key Authentication vs Username/password for API Access

I have a linux device that will be making periodic call to an API server, say everytime the system boots up. Everytime then it should authenticate itself and then do its thing. I can either store the ...
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Is there a risk in opening port 22 for ssh access with a network? [duplicate]

Background We have our own datacenter which houses platform specific environments and each environment is isolated. Eeach environment is also has 3 tiers (Web Servers, Application Servers & ...
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What can I do with a SSH certificate? [migrated]

Doing an information security project at the moment. After gaining access to ftp drive, there was a file simply called 'hackme' inside. It contains what looks like to me a SSH certificate, but not ...
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How secure is Visual host key, and how is SHA2 converted into that representation?

SHA2 has 256 bits of possibilities. Visual host key seems to have the following upper and lowercase = 26*2 numbers and symbols = 20 Additional symbols = 22 Total 94 characters represented in ...
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Is it always better to put authorized_keys in one's own .ssh directory rather than in root's .ssh directory? [duplicate]

I connect via ssh to multiple Linux servers during the day from my Mac's Terminal window. On my Mac I have the public and private keys in my .ssh directory. On the Linux servers I always use "sudo ...
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Determining a version of SSH from penetration testing?

I am a software developer -- but not a security specialist. A (legitimate) company that does security scans sent my company a notice that we are running an older version of SSH on our hosting server. ...
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2answers
101 views

Share root access without sharing password

I am looking for a way to share admin privileges on some hosts without providing the admin password. From his link, I was thinking of using a primary host from which every user can sudo -u user to ...
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1answer
147 views

Does OpenSSH use export ciphers?

With all of this talk of 'FREAK', no one has mentioned OpenSSH. It implements libraries from OpenSSL (until recently, anyway). Why aren't people talking about this? is there even a way to configure ...
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1answer
65 views

End-to-end encryption with a reverse proxy and an application server

Lets say that I have an nginx reverse proxy that proxies the traffic to a Tomcat on the same server. I think the most common way to configure this setup is to enable SSL on nginx and then proxy the ...
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Two keys in ~/.ssh directory [migrated]

I originally had a DSA public key in my ~/.ssh directory on my server id_dsa.pub. The corresponding private key id_dsa is stored on my local machine. I then generated an RSA key pair directly inside ...
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95 views

Linux/ssh - Forensic question

In a Linux terminal, I made a ssh connection from A to B and I used commands to read some files stored in B. Then I disconnected and I closed the terminal. Is it possible to find on A, informations ...
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51 views

Same RSA key pair for all users

Let's say in my computer running Debian i have an RSA key pair generated by user foo and copied the public key to server_A for allowing key based authentication in ssh for foo. Now my question is can ...
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1answer
45 views

Can a compromised OpenSSHD server be used to upload a malicious payload to a client?

Since I'm fairly unfamiliar with the specific details of the SSH protocol, I was wondering if it was possible for a compromised SSHd server to upload a malicious payload (like a Trojan or some other ...
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2answers
51 views

What are the real-world implications of duplicate SSH fingerprints across many devices?

There was a recent post on the Shodan blog showing that certain SSH fingerprints are common across thousands of devices. For example, this fingerprint is common across over 250,000 devices worldwide: ...
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Realistically, how much added security does having a passphrase on a ssh key have?

Let's assume ssh key brute force is unrealistic. It seems to me your greatest vulnerability would be someone gaining access to a client filesystem. If that's the case then key loggers and a host of ...
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PCI DSS and ssh keys for root

Referring to this PCI DSS 2.0 and ssh keys I want to ask Is this PCI section 8.2 only for individual users or also valid if a user connects via ssh to a root account? I prefer to ssh root@localhost ...
3
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1answer
125 views

Has the security of PuTTY been examined?

I am wondering how PuTTY stacks up against other SSH implementations with respect to scrutiny and security of its SSH2 protocol implementation. PuTTY is probably the most-used SSH client on the ...
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122 views

Is it safe to store a passphrase encrypted SSH key in git?

I have a bunch of servers that need to access somewhat sensitive data (passwords for ftps, api keys, etc). Currently I copy a plaintext file back-and-forth between the servers via ssh and encrypt all ...
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Management of server keys

I plan to put an SSH server on micro-controller devices. There shall be many devices distributed in a wide range. The identity of the server is checked with the server key. The server needs to store ...
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33 views

Can sshd block IPs with failed attempts or is a tool like denyhosts or fail2ban necessary?

I am only indirectly familiar with denyhosts (and only just discovered fail2ban) and they certainly seem like worthwhile tools. However, after looking through the options for sshd_config I am trying ...
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1answer
120 views

SSH raspberry pi security

I've setup an SSH server on my Raspberry Pi. I use RSA keys to login, I disabled root login, password authentication and I use port forwarding to login from outside my network. I can see the ...
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1answer
198 views

Are these SSH passwords of hacked servers?

I have been seeing persistent SSH connection attempts on my computer from a familiar IP address. I got curious and decided to do some Googling on the IP address. Turns out that someone from Indonesia ...
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How do I get the thumbprint of an SSH2 public key on windows?

I have a SSH2 public key with a .PUB extension and when viewed in notepad it has this header: ---- BEGIN SSH2 PUBLIC KEY ---- How do I view the thumbprint of this key? I've attempted ssh-keygen ...
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34 views

Using a custom authentication mechanism with SSH

I have a hardware device that can compute ECDSA signatures and generate ECDSA keys without exporting the private key (only public key is exported). I'm looking for a way to tie this into SSH. Is ...
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59 views

Mount ecryptfs directory via SSH

I have access to a server that I use for backups. I use rsync with the --delete flag to make an exact copy of my backup directory. I have no need for incremental backups. The backup directory on the ...
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121 views

Monitor SSH traffic

Hi Folks, I was monitoring my SSH port with tcpdump and have had a lot of activity as expected. When I look at the traffic I get the above image. What does it mean? Thanks
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SSH stealing files from client?

Is it technically possible for a ssh server to steal files from a connected client?.
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87 views

OpenSSH downgrade attack

I have tried to implement a downgrade attack against the SSH protocol as the first steps (encryption protocols exchange) are not signed, as per RFC4253. The idea is to intercept (mitm) these steps and ...
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1answer
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signing private openssl key for use with openssh

This is related to Converting keys between openssl and openssh . I have private keys generated by openssl that I want to use with SSH for connection authentication. I have no issue using ssh-keygen ...
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Single vs server specific ssh keys?

This question has a bit to do with procedure. Is it better for a person to have one single ssh key pair and share the public key where needed. Alternatively is it better to have server specific keys? ...
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Is password + second factor more secure than public key auth now? (SSH)

I ask this question because, I think, we now can reasonably assume the following: NSA can break VPN and SSH: This is stated many times in the unclassified slides. Also, GCHQ has demonstrated (and ...
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Why doesn't SSH use a better algorithm for encrypting keys?

According to the answers in this question, SSH still uses a very basic algorithm for encrypting keys with a passphrase, which can be attacked at a rate of billions tries per second using dedicated ...
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1answer
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Is it considered woth it to replace OpenSSH's moduli file?

Consequences of tampered /etc/ssh/moduli describes a possible risk if the moduli file for an OpenSSH server has been tampered with. Taking the logic a step further, is there any concern with the ...
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Malware known for stealing private ssh keys

The ssh private key file, stored under ~/.ssh/id_rsa in many *nix distros, is typically owned by the user, allowing any program invoked by that user to read the file, and perhaps upload it to a remote ...
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66 views

How can I prevent keys loaded into ssh-agent from being sent to a particular (insecure) server?

A particular server I need to interact with has an ancient or crippled sshd installed, and only supports SHA1 algorithms for key exchange. From information in the Snowden documents, I am leery that ...
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Is there any security risk with adding a **root's** public key to the local user's authorized_keys (so root to login as a user non-interactively?)

Background: I want to try unprivileged lxc containers a try on my small web server (hosting 2-4 users). Since the server is shared among friends, we decided to separate our services from the machine ...
2
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1answer
66 views

Allowing root login, but denying any actual logins

A friend told me a few months ago about an audit where he discovered root logins were enabled via SSH. This obviously ended up on the report, but when questioned the admin told him that he had set up ...
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1answer
214 views

Firewall and Torrent

I use my university internet network and all incoming connection is blocked on every port.(they use netasq firewall) They have no other restrictions which stops me from using a torrent client. Using ...
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Public key authentication: what gets signed?

I've just started reading about SSH and how it's used for authentication. From this website, it says: The private key is able to generate signatures. A signature created using your private key ...
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186 views

What kind of vulnerability it may have for known ssh-hostkey?

I saw there is NSE script in nmap that can retrieve the ssh-hostkey(RSA or DSA) from the target host. For example, 22/tcp open ssh | ssh-hostkey: 2048 ...
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642 views

How does SSH use both RSA and Diffie-Hellman?

SSH protocol 2 allows you to use DSA, ECDSA, ED25519 and RSA keys when establishing a secure connection to a server. (Keep in mind for this question that I'm only familiar with the procedure and ...
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Can I “hide” the private key, while still allowing it to be used?

Let's say you assign SSH keypairs to all users on your system; none of these "low trust" users have root privileges. You want the users to be able to use their keys in SSH connections, however, you ...