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 ...
6
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3answers
804 views

SSH key auth, but still need password for sudo?

SSH with public-private key authentication comes enabled by default with most Linux distributions. This is great because when I create accounts for remote users I don't have to email them sensitive ...
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1answer
35 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 ...
4
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1answer
36 views

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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1answer
72 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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1answer
18 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 ...
5
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1answer
106 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 ...
2
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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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1answer
39 views

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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2answers
104 views

Expiration / enforce change of passphrase for private ssh keys

Out of curiosity, and also to check whether this is doable at all: Is there any way using standard tools to assign an expiry date [only] to the passphrase of an ssh private key, or to enforce the ...
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2answers
17k views

How is OpenSSL related to OpenSSH?

Is OpenSSH using OpenSSL to encrypt traffic? Or something else?
7
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1answer
60 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, ...
0
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0answers
34 views

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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3answers
275 views

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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5answers
6k views

SSH password vs. key authentication

I've usually been told that public key authentication is strongly preferred over password authentication for SSH. However our previous admin was against public keys and only issued passwords and took ...
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0answers
34 views

Suppose rc4 cipher is insecure. How much does it affect the default openssh service on Ubuntu 14.04? [closed]

There are credible reports indicating that rc4 is insecure or will be in a very near future. Suppose there are villains that are already capable of breaking it. How much does it affect the default ...
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0answers
40 views

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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3answers
611 views

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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2answers
60 views

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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2answers
120 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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2answers
26 views

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. ...
3
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1answer
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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2answers
54 views

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 ...
4
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2answers
106 views

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 ...
2
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1answer
143 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 ...
0
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1answer
209 views

SSH scan against D-Link routers: is there a (new) exploit?

TL;DR if you have a D-Link router perhaps it wouldn't be a bad idea to check its SSH settings and/or username/passwords. I am a long-time user of fail2ban on several machines, almost all Ubuntu 12 ...
230
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7answers
176k views

RSA vs. DSA for SSH authentication keys

When generating SSH authentication keys on a Unix/Linux system with ssh-keygen, you're given the choice of creating a RSA or DSA key pair (using -t type). What is the difference between RSA and DSA ...
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3answers
693 views

PCI DSS 2.0 and ssh keys

I know the real answer to the auditor. We are a smaller company under 40 total employees that is also PCI level 1 compliant. We've always used ssh keys on internal servers. You can't ssh in from the ...
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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
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 ...
1
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1answer
60 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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1answer
514 views

Digital Ocean “Droplet” allgedly compromised for trivial, unpublicized website. Should I be worried abouty my own machine?

I got a message from D.O. about my Droplet saying they shut it down because there was a lot of outgoing traffic that looked like an attack. The site I had on that server was not very known at all. ...
0
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2answers
143 views

What are the risks associated with SSH'in from corporate LAN to untrusted server on the Internet

At work (a huge organisation) I found a server on the LAN that opens SFTP connections to 2 servers across the Internet. I assume the remote hosts are in the other parties DMZ. I know you are not ...
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0answers
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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 ...
7
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1answer
197 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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4answers
13k views

Brute-force an SSH-login that has only a 4-letter password

Suppose, you know that a certain computer is only protected by such a short password, then you could just try every possible combination easily. How would a script look like, that tries to crack that ...
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2answers
186 views

How can I block certain IP addresses from my router?

I have done some basic things protect my router like disabling wps setting strong passwords and stuff. However, I am using a virgin media superhub 2 where it does not seem to be possible to ssh into ...
8
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1answer
240 views

Visual fingerprint verification

OpenSSH allows to show a visual representation of fingerprints with the VisualHostKey, see announcement at O'Reilly and here. The output looks approximately like this: # Host github.com found: line ...
4
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1answer
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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1answer
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
44 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
50 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: ...
6
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2answers
104 views

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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2answers
31 views

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
123 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 ...
11
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2answers
705 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 ...
33
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3answers
65k views

What is the difference between authorized_key and known_host file for SSH?

I am learning basics of SSH protocol. I am confused between the contents of the following 2 files: ~/.ssh/authorized_keys: Holds a list of authorized public keys for servers. When the client ...
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2answers
432 views

Does public key auth in SSH prevent most MITM attacks?

I found this article that claims asymmetric crypto signature of DH-obtained key prevents MITM: http://www.gremwell.com/ssh-mitm-public-key-authentication Key idea: The value of 'signature' is a ...
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4answers
135 views

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 ...
3
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1answer
118 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 ...