0
votes
1answer
29 views

User-friendly public/private manual authentication protocol

I have a remote service which allows users to SSH login to the machine and they're automatically sent to the (command line) application (without access to a bash prompt, for instance). In the course ...
0
votes
2answers
69 views

OTP vs. Keyfile

I have been wondering what are the benefits and cons of using an OTP (one time password) versus a keyfile to, for example, decrypt a keepass database, connect to a server via SSH, or other uses. ...
0
votes
2answers
72 views

Why does ssh `known_hosts` file need server name?

When I push/pull repos on GitHub over SSH, sometimes there will a message about unidentified server and asks if I want to trust and add it to known_hosts. Apparently this is because GitHub has ...
2
votes
7answers
322 views

Is it wrong to root login with SSH?

I've long been under the impression that with unix, you should never login as root. Now I've started using Virtual Private Servers over at DigitalOcean, and some advice is to use SSH keys to login as ...
0
votes
2answers
79 views

How to transfer securely a file between servers?

Let's say I have two Linux servers. One containing a desktop app database (running on a local network) and a webserver. I want to automatically transfer each hour a database file (with a size of a ...
0
votes
1answer
163 views

ssh always too many authentication failures

No matter on which server I try to connect via password login, I always get the error message Too many authentication failures for If I have exchanged the ssh-keys, I can login without password as ...
0
votes
1answer
77 views

Should I use the root account on my Digital Ocean server?

I have set up an SSH key with Digital Ocean that is automatically added to any servers I create. Is it okay to use this root account for SFTP and daily use or should I create another user account and ...
1
vote
1answer
586 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 ...
6
votes
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 ...
0
votes
2answers
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 ...
0
votes
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 ...
0
votes
1answer
773 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 ...
1
vote
0answers
49 views

Considerations when implementing a key based SSH-like auth scheme

I have a SMTP server where all the users (for an unrelated reason) will have public keys tied to their username and registered with the server. I want to add a non-standard extension that uses these ...
1
vote
2answers
65 views

How to setup cronjobs that do scp without saving the .pem file on either of the machines

I have the following situation and want to know what are the best practices to do such things without exposing myself to security issues I have two servers both use the same private key for login. ...
2
votes
1answer
170 views

2-Factor Auth with SSH

I recently acquired a Synology NAS (DS1513+). I am looking to expose SSH access remotely and to that end would like to harden SSH as much as possible. Is 2 Factor auth possible and if so what are the ...
0
votes
1answer
174 views

Building an VM with Vagrant and connecting with ssh+2FA to protect a bitcoin wallet?

I would like to try to build a Virtualbox image to use with Vagrant. This is the features: Login with SSH + 2FA (Google Auth) No X No internet connection Copy unsigned transaction, sign it and ...
0
votes
2answers
439 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 ...
6
votes
1answer
1k views

What does chacha20-poly1305@openssh.com mean for me?

OpenSSH just introduced a new protocol, chacha20-poly1305@openssh.com, which combines the two algorithms from DJB: ChaCha20 and Poly1305-AES. It was inspired by a similar proposal for TLS, which ...
13
votes
2answers
447 views

Why should one avoid chains of SSH sessions?

In this document on Security on NSC computing resources, there are several obvious pieces of advice (use a strong password, don't repeat passwords, etc.). One piece of advice I have not seen before, ...
4
votes
3answers
852 views

In what ways does increasing SSH host key length increase security

I have read on a few guides on "how to secure SSH servers" that it is a good thing to increase ServerKeyBits from the default of 768 to 2048. Most of these guides seem to be for the entry ...
5
votes
3answers
1k views

Is it possible to use a GPG or SSH key for web based authentication in a secure fashion?

Let's say hypothetically I am writing a web application targeting technically inclined, security-conscious users who have no problems generating and using GPG or SSH keys. Is it possible to use said ...
6
votes
2answers
3k views

Best way to allow sudo access when using ssh keys

Probably a simple question, but I can't seem to find any actual best practices out there. I manage a handful of servers and I am really getting sick of tracking my passwords in pwsafe. I've been ...
2
votes
4answers
370 views

Is there a way to keep sudoers from editing stuff in /etc/ssh/sshd_config?

I have root login disabled in SSH and I want to be able to eliminate the possibility of a sudo user editing the /etc/ssh/sshd_config file and enabling root ssh login. Is this possible?
1
vote
1answer
159 views

Do I need logging enabled in my rules in IPFW for sshguard-ipfw to work/blacklist ip's?

From the FreeBSD handbook: Even with the logging facility enabled, IPFW will not generate any rule logging on its own. The firewall administrator decides which rules in the ruleset will be ...
1
vote
1answer
147 views

Simple and secure remote installation method that accepts input via a web page?

When installing software on a remote server: Is it possible to let the admin (i.e. the user that installs the software) define admin username and password via a HTML page, in a secure manner? ...
8
votes
5answers
4k views

What are the ways to implement two factor authentication?

We have devices that can generate tokens. So we can use tokens with passwords to perform two factor authentication. There are many ways to implement such systems to enhance security. One of two I ...
35
votes
4answers
5k views

Should I change the default SSH port on linux servers?

Is there any advantage in changing the SSH port, I've seen people do that, but I can't seem to find the reason why. If you have a strong password and/or a certificate, is it useful for anything? ...
9
votes
2answers
4k views

How to set up OpenSSH to use x509 PKI for authentication?

I do not mean simply putting the public RSA key of a x.509 certificate into ~/.ssh/authorized_keys - I'm looking for a way to set up a ssh such that x.509 certificates signed by a pre-defined CA will ...
2
votes
4answers
1k views

SSH: reusing public keys and known-man-in-the-middle

Usually, people recommend to use a single private-public key pair everywhere (if we're not talking about a possibility of compromising the private key): Best Practice: “One per-user ssh key” or ...
4
votes
2answers
3k views

Disabling authentication via DSA keys in OpenSSH?

How can I disable DSA and ECDSA authentication on my server with OpenSSH 5.9? Sifting through the documentation material and doing a web search didn't yield any results - only an old bug report for ...
11
votes
2answers
12k views

How does ssh public key authentication work?

My basic understanding is this: The (connected to) server's sshd uses the public key to encrypt some message The client's ssh or ssh-agent decrypts it and sends something back (the message's ...
27
votes
3answers
49k 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 ...
8
votes
5answers
866 views

How do RSA fingerprints protect from MITM attacks?

I understand that RSA fingerprints are used to verify that you are really connecting directly to who you want to connect to, and not someone else posing as that site. Like when you do a git push, it ...
5
votes
2answers
5k views

Creating user specific authentication methods in SSH

I have configured sshd on an Ubuntu server to use key authentication and it is working fine. I had to disable password authentication for key authentication to work. Server is always accessed via ...
5
votes
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 ...
2
votes
2answers
111 views

Does TLS-OBC only improve security of Web Browsers? Does it improve the security of SSH?

I'm studying the TLS-OBC extension and would like to know if it improves security of non Web-based protocols? Specifically, would it be of any benefit to SSH clients? (version 1 or version 2.x/secsh) ...
17
votes
9answers
3k views

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 ...
1
vote
3answers
172 views

Smartphone SSH clients with shared user

I am writing an application for smartphones to provide very limited SSH usage. The user cannot perform arbitrary actions when logged in. They can run a specific script(s) only. For various reasons ...
7
votes
4answers
1k views

can ssh passwordless public key authentication be ok if combined with a VPN?

Having a debate with a coworker about the merits & faults of public key authentication with ssh. I'm basically wondering what all the possible merits and faults are, especially in regards to ...
50
votes
7answers
6k views

Are passwordless SSH logins more secure?

I had a long discussion with my co-workers whether key-based SSH authentication (particularly for OpenSSH) is more secure than authentication using passwords. My co-workers always connect to servers ...
7
votes
2answers
2k views

ssh public/private key pair

I am having problems understanding how ssh really works. I know it uses a public key cryptography to encrypt messages. However, I can ssh to a server without first generating a public/private key pair ...
191
votes
7answers
141k 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 ...
37
votes
6answers
4k views

Is using a public-key for logging in to SSH any better than saving a password?

Using a public/private key pair is fairly convenient for logging in to frequented hosts, but if I'm using a key pair with no password, is that any safer (or less safe) than a password? The security ...
6
votes
2answers
498 views

How can I authenticate a client connection in a secure way?

Let's say I have a server listening on port 1234. I have some client software that needs to be able to connect to this port. But I want to prevent malicious users from bypassing the client software ...