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 are the security issues of a MITM on an ssh session with rsa keypair

If a user connects to an SSH server using an rsa private key, but does not confirm the server's fingerprint. What kind of information can a man in the middle attack get from the session?
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179 views

Should remote access (RDP/SSH) only be allowed for VPN clients? Or should RDP and SSH be opened the public?

I am about to push hard against the powers that be and strongly recommend that we shift our many (20+) consultants from direct public access to RDP & SSH to VPN clients (connecting to a ...
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86 views

Linux SSH and GPG

Can anyone please give me a quick crash course on SSH and GPG? SSH: What is the difference between public and private keys? Should I back up my ~/.ssh/ directory, what are the security implications ...
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192 views

Storing SSH private keys on an Android device

(I'm not sure if this better belongs on unix.se or android.se, but since it's primarily security-related, I'm asking it here) I use my Android device to access servers for quick on-the-go ...
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1answer
421 views

Open source solution to capture and decrypt SSH traffic (with private key)?

I am looking for a free open source solution that is able to capture and decrypt SSH traffic given the fact that I can provide the server's RSA private key (something like SSH CryptoAuditor). Please ...
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1answer
160 views

Bastion host that allows jailed users to SSH but protects private key

Basically, I'm trying to let the user use a private key without having read access to it. Use case: Employee needs to SSH to a server in the data center. There is 1 private key for all servers, ...
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17 views

Is Mosh as secure as SSH? [duplicate]

Mosh, from my limited understanding of it, is a service which operates a shell over UDP. It claims to use SSH to initiate the connection, then starts the Mosh service on the client, and then connects ...
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88 views

Should I use more than 2048 bits in my SSH-2 RAS Key?

I've been asked to generate a public key with PuTTY Key Generator. The default is 2048 bits, Should I add additional bits to the generated key? Or is it unnecessary?
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304 views

Given an IP address can you ssh into /tmp without password?

I'm a Software Engineer, but I have no experience in security, so i'm trying to learn by doing (woot Experiential learning!). I know that the permission settings on the tmp folder are very relaxed. ...
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2answers
88 views

Can a SSH server or client to initiate a unencrypted connection?

Several clarifying questions: Is it possible to disable the SSH encryption using options at the OpenSSH server/client or some appropriate hack? Is it possible to do this at the time of the ...
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3answers
173 views

Working from many places <-> being able to restrict SSH access to server to IP range

I administer a webserver, and while I'd like to restrict the SSH access to an IP range, I wouldn't be able to do so because a) I travel a lot and b) I don't have a static IP at my homeoffice. I've ...
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45 views

can ssh port forwarding be detected?

say there are three players: A, B, C where A is local machine, B is ssh server, C is the final destination. through ssh local port forwarding, A can connect to C via B. So then data will be ...
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37 views

what is a server fingerprint in ssh?

Is is the same as a public key in RSA, except they made it more suitable for self-signed hosts? What happens behind the scenes when our ssh client presents it to us?
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231 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 Keypass/Lastpass due to having to trust they ...
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2answers
64 views

Risk in connecting wrong ssh host?

I've a ssh host key login setup in a remote server, for some reason, the DNS of that host is mapped to another server. So assume the mistaken host cannot be trusted, should I change my key?
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58 views

unfamiliar IP when logging into ssh server

I just noticed something today, and Now I am curious... I was on my shell server, an i was wondering who was on, so I gave the command $w and saw this: j0h@server:~$ w 22:06:02 up 18 days, 7:02, ...
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1answer
236 views

Can an SSH server fingerprint be spoofed?

If I simply connect to an SSH server, get its key fingerprint, and immediately disconnect, does the SSH protocol ensure that the server also had the private key in order to get that far into the ...
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1answer
79 views

Practical advantage of requiring VPN for SSH

I have some VPS servers which I manage through ssh. However there are many ports which I want open during development, therefore I also have OpenVPN on them. Now I am wondering if it would make ...
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4answers
422 views

Is it secure to use *no authentication* for services listening only on localhost?

I have many applications installed on my server that use a webui frontend to control the application. Since I am the only user of the server, I usually bind these applications to 127.0.0.1. As the ...
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2answers
214 views

Encrypted offsite storage using sshfs and cryptsetup/dm-crypt/LUKS

I'm interested in an encrypted offsite storage scheme, but I don't want to depend on the vendor for encryption. I have an idea for doing so by combining sshfs with cryptsetup/dm-crypt/LUKS, but I'd ...
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1answer
943 views

How to use public key in ~/.ssh for asymmetrical encryption with OpenSSL

I want to do an asymmetrical file encryption: openssl genrsa -des3 -out private.key 4096 openssl rsa -in private.key -pubout -out public.key openssl rsautl -encrypt -pubin -inkey public.key -in a ...
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1answer
584 views

Bypassing CVE-2010-4478 (J-PAKE parameter validation) in OpenSSH 5.1

Did anyone successfully exploit CVE-2010-4478 in the past? This is insufficient validation of the J-PAKE public key parameters in OpenSSH up to 5.6. I'm dealing with a vulnerable machine running ...
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2answers
171 views

Checking if a server is compromised

I do free/low-cost web/shell hosting as a non-profit organization (With a the same friend and co-founder) since 2007. We're on CentOS 6 + CPanel, and unfortunately we're still funding the ...
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1answer
2k views

Two-factor authentication with ssh key authentication and yubikey?

OpenSSH won't invoke PAM at all if public key (RSA) authentication is configured and the client presents a valid key. So if you use key-based auth, you can't enforce 2FA easily. One workaround for ...
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105 views

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 ...
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514 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 ...
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339 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 ...
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484 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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1k 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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50 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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107 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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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 ...
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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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67 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 ...
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529 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 ...
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3answers
99 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 ...
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1answer
159 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 ...
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2answers
115 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 ...
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2answers
225 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 ...
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1answer
82 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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161 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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37 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 ...
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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 ...
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3answers
50 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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81 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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59 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 ...
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4answers
8k 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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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 ...
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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 ...
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771 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 ...