SSH (Secure shell) is a protocol for secure communication between computers to execute remote commands, transfer data and tunnel TCP connections.

learn more… | top users | synonyms

4
votes
2answers
275 views

Recently set up a server, Need security help

I set up a server running debian I opened port 22 allowing access to ssh into the port. I keep getting weird messages in my router log saying: [LAN access from remote] from 211.161.46.101:57201 to ...
0
votes
1answer
80 views

how to create an encrypted ssh tunnel between local machine and final machine?

My machine at work is behind a firewall. To connect to it first i need to connect (ssh) on another machine and then through this machine i make the ssh on my machine. In other words, there is a middle ...
0
votes
2answers
191 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 ...
18
votes
5answers
4k views

How often should an SSH key pair be changed?

I've been using a 1024-bit RSA key for passwordless SSH between my own systems for years. More recently I've also started using it for passwordless access to my hosting providers and to source code ...
0
votes
1answer
493 views

Is sshpass utility insecure than manual ssh password authentication?

I'm planning to automate copying a large file to a remote server over ssh using rsync, using following command : sshpass -p '<PASS>' rsync --partial -av --progress --inplace --rsh='ssh -p 22' ...
-2
votes
1answer
121 views

Surfing web anonymously on a mac using Firefox SSH and Tor [duplicate]

I want to download and upload to the internet anonymously. I have successfully configured Forefox to access internet through a secure SSH tunnel service (and remote server). I use 'SSH Tunnel Manager' ...
1
vote
1answer
175 views

How do I find out if I'm connecting to a spoofed server after getting “The authenticity of host [hostname] can't be estabilished”?

I've been SSHing into my VPS for months with no problems and this morning it returned this familiar message: The authenticity of host '[hostname]' can't be established. ECDSA key fingerprint is ...
1
vote
2answers
219 views

Someone logged on my Centos VM; Can they attack the host OS?

I'm using Windows 7 and decided to learn Linux Administration (Centos 6.4) using Oracle VirtualBox to host the Linux system. In my network configuration I choose "Bridged Adapter". I set the VM's IP ...
1
vote
2answers
287 views

Is SSH secure and what are the recommended modes of operation?

Given the recent confirmation of weakened and broken encryption schemes and implementations, how does the community feel about the security of SSH? It seems there has been very little discussion ...
38
votes
3answers
881 views

Is an SSH session to a mistaken site a security exposure?

A few minutes ago I attempted to ssh to a server I have at my office. Since it is a new server my public key has not been set up there so I had to type my password in manually. After three times of ...
6
votes
1answer
530 views

What's the hash for in ECDHE-RSA-AES-GCM-SHA?

Presumably the SHA is for deriving the AES key from the shared secret. Where else is the hash used? ECDH just does ECC (no hashing). RSA does masking and padding but this doesn't involve the ...
1
vote
3answers
167 views

What is the safest way to copy a file from an untrusted system?

Scenario: There are two computers running GNU/Linux, U and T. U is untrusted and T is trusted. A non-executable file F (which may however have been infected with malware) resides on U. (For ...
2
votes
1answer
41 views

“holding open” encrypted home with local ssh

I have a couple of machines that I use for purely automated stuff, with home directories encrypted using ecryptfs. So even if the machine is powered on, those directories aren't decrypted unless that ...
4
votes
2answers
95 views

Privacy/Security with SSH Tunnels and QuickVPN

I currently use QuickVPN, however, it does not seem to route my web browsing traffic through a tunnel. Am I correct? It only opens up a tunnel for accessing windows shares and documents back at the ...
8
votes
2answers
136 views

How does SSH defend against keystroke-timing attacks?

This paper: https://www.usenix.org/legacy/events/sec01/full_papers/song/song.pdf Explains how SSH can be compromised by analyzing the timing of the keystrokes to guess what the user is typing. It's ...
41
votes
5answers
38k views

What is the difference between SSL vs SSH? Which is more secure?

What is the difference between SSH and SSL? Which one is more secure, if you can compare them together? Which has more potential vulnerabilities?
6
votes
1answer
657 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 ...
0
votes
1answer
61 views

Safe to utilize “unknown” SSH-server? [duplicate]

I've been offered a free Secure Shell at a friends server. However, I was wondering if it might be insecure to join this server from my personal computer at home - may my computer pose any security ...
2
votes
1answer
153 views

For remotely unlocking LUKS volumes via SSH, how can I verify integrity before sending passphrase?

Although this is closely related to the recently closed question Evil maids in the server room [closed], I believe that it's more answerable. I'd like to unlock LUKS volumes on remotely hosted ...
1
vote
1answer
42 views

Does having non-ECC SDRAM affect security of the system?

If I don't have SECDED ECC DRAM, is it possible or realistic that a bit could flip around sshd, and grant a lucky lurker access to my system without requiring a valid password?
7
votes
2answers
1k views

Taxonomy of Ciphers/MACs/Kex available in SSH?

SSH offers a large variety of algorithms for Ciphers, MACs and KexAlgorithms configuration options. Sometimes I need quick and light (my own internal network), and sometimes I want all the ...
13
votes
2answers
439 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, ...
18
votes
7answers
12k views

Invalid users trying to log in to my server

I'm seeing a lot of log entries that appear to be failed login attempts from unknown IP addresses. I am using private and public keys to log in with SSH but I have noticed that even with private ...
1
vote
1answer
158 views

Evil maids in the server room [closed]

I am well aware of the fact that physical insecurity in principle means no security. But let´s say I own a root server with full disk encryption which is unlocked/booted via dropbear ssh. In which ...
2
votes
2answers
346 views

Attacks in SSL and SSH

Assume that we have two end-host A and B connected by two routers R1 and R2. A wants to send a large file to B. A decides to establish SSH connection with host B using public key authentication. ...
3
votes
1answer
164 views

ISP and ssh tunneling

I have a question about ssh tunneling. Is it possible for the ISP to realize the destination server which I want to connect it via ssh tunneling? I mean the destination website which I want to visit ...
3
votes
2answers
716 views

What is the difference between SSH and IPsec?

There seems to be similar encryption going into both. They both use asymmetric (RSA, elliptic curves, etc) for the initial key exchange, then go to some symmetric (AES, Blowfish, etc) protocol. I'm ...
1
vote
2answers
129 views

Securing multiple connections with different protocols all together

I need to secure the communication between an application (runs on any PC and has been designed for Windows) and an external device (runs on UNIX). The application is running on Windows while the ...
5
votes
1answer
89 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 ...
0
votes
1answer
379 views

Exploiting SUID Binary that connects to SSH server

While conducting a pentest on a Linux machine, I have a limited shell and trying to escalate privileges. One interesting thing that i have found is a binary called connect installed under ...
1
vote
2answers
133 views

PCI-DSS - key-based shell access to internal servers?

In the following PCI 2.0 requirement, I am not sure how to interpret computer access to internal machines (not remotely accessible): Requirement 8: Assign a unique ID to each person with computer ...
5
votes
3answers
814 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 ...
7
votes
2answers
2k views

What's the purpose? Strange login attemps “sshd[***] Received disconnect from **.**.**.**: 11: Bye Bye [preauth]”

I've seen something like: sshd[***]: Invalid user oracle from **.**.**.** // 1st line sshd[***]: input_userauth_request: invalid user oracle [preauth] // 2nd line ...
17
votes
3answers
34k 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 ...
1
vote
2answers
292 views

SSH Access using private keys

I am trying to practice ethical hacking in my own lab. I have got limited shell in a fedora box in addition I am able to read root files like /etc/shadow trough another vulnerability. Now, I need to ...
2
votes
3answers
229 views

Is there an internal equivalent to fail2ban?

fail2ban is a protection against brute-force that locks a user out after a definable maximum failed login-attempts. But if a user already has access to a server with another username already fail2ban ...
-2
votes
4answers
5k views

How do i brute-force an SSH-login which has an only 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 ...
11
votes
1answer
8k views

Secure Configuration of Ciphers/MACs/Kex available in SSH

Following on the heels of the previously posted question here, Taxonomy of Ciphers/MACs/Kex available in SSH?, I need some help to obtain the following design goals: Disable any 96-bit HMAC ...
4
votes
2answers
1k 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 ...
3
votes
2answers
287 views

Plausibly deniable SSH - does it make sense?

My colleague just told me he can't make outbound SSH connections in his corporate networks, so I advised him to set up a server on 443 port and it worked. I then started thinking that the ...
-1
votes
1answer
455 views

Afraid about SSH on my Linux system

I've checked my Linux server (Centos 6) with rkhunter. I found the following in rkhunter log [14:38:54] Checking if SSH protocol v1 is allowed [ Warning ] [14:38:54] Warning: The SSH ...
29
votes
3answers
16k views

SSH key-type, rsa, dsa, ecdsa, are there easy answers for which to choose when?

As someone who knows little about cryptography, I wonder about the choice I make when creating ssh-keys. ssh-keygen -t type, where type is either of dsa,rsa and ecdsa. Googling can give some ...
1
vote
1answer
205 views

SSH authorized_keys

Can you correct me on this. I create a keypair on my PC. Copy the public key (append to authorized_keys) on the server. Disable password auth on the server, and SSH to server from my PC. I have ...
7
votes
3answers
283 views

Why is RFC4255 (SSHFP) not used for https?

I had this idea a few hours ago, but of course it already exists and there is even an RFC... Why don't we publish the fingerprint for the SSL/TLS certificate via DNS? We need DNSSEC to make sure the ...
1
vote
1answer
68 views

Securing WebHosting Shell Access

If I provide SSH access to users who has paid webhosting service, what security measures should be applied ? What I can think of: SSH keys RSA of 4096 size (shall be secure for a while) Apache ...
4
votes
2answers
2k views

How do I get the RSA bit length with the pubkey and openssl?

I have a public key generated with ssh-keygen and I'm just wondering how I get information on the keylength with openssl?
1
vote
1answer
1k views

What effect has MaxAuthTries=1?

I configure a new server right now and ask myself what is the internally effect if I set MaxAuthTries=1 in sshd_config. The server only accept key authentication an no root logins. Has this setting ...
0
votes
3answers
123 views

Securely transferring data from service provider to client

Suppose a client C wants to transfer form a service provider P, who collected data on behave of C using a web-application. Additionally, suppose the amount of data is larger than 100 MByte and ...
5
votes
1answer
2k views

Consequences of tampered /etc/ssh/moduli

What are the consequences if an attacker is able to modify the /etc/ssh/moduli file?
1
vote
0answers
88 views

Why my proxy is still having some connections blocked

I am behind a firewall in France. I connect to proxy A, in Ireland with Dante via SSH port 22 and make a tunnel forwarding port 1080. The proxy works as expected but still having a port range ...