||Home||Switchboard||Unix Administration||Red Hat||TCP/IP Networks||Neoliberalism||Toxic Managers|
|(slightly skeptical) Educational society promoting "Back to basics" movement against IT overcomplexity and bastardization of classic Unix|
|News||SSH||Recommended Links||Password-less SSH login||Mini-tutorial||FAQs|
|ssh-keygen man page||Procedure||Tips||humor||Etc|
There are two types of keys that are used: server keys and user keys.
When the OpenSSH server package is installed, server authentication keys are generated. They are unique to the server. They are used to verify that the client is connected to the intended server not its imposter. The first time a client connects to an OpenSSH server, it must accept the server public key. If accepted, the client stores the server public key and uses it to verify the identity of the server with each connection.
User keys mechanism is different. To use public key authentication, the public key of the user has to be stored on the server in the home directory of the user account being accessed. These public keys are stored on the server in the file ~/.ssh/authorized_keys.
The corresponding private key must be stored on the client computer. With the keys stored in the appropriate places, the following occurs
In the public key authentication process:
Instead of using a password to authenticate, OpenSSH allows the use of a passphrase. Why use a passphrase? Unlike a password, a passphrase can contain spaces and tabs and is usually much longer than a password, hence the word phrase in the name. The added length along with the spaces and tabs makes a passphrase more secure and harder to guess.
Passphrases are unique per user and must be created by each user while logged in with the corresponding username. Most modern Linuxes uses SSH Protocol 2 and RSA keys by default. To generate an RSA key pair for SSH version 2, use the following command:
ssh-keygen -t rsa
Press Enter to accept the default location of $HOME/.ssh/id_rsa after the key pair is generated. When prompted for a passphrase, type a passphrase to use and type it again to confirm. The passphrase should be different from the user's password and should contain a combination of numbers and letters to make it more secure. Remember it can contain spaces and tabs. The RSA public key is then written to $HOME/.ssh/id_rsa.pub while the private key is written to $HOME/.ssh/id_rsa.
Note: The private key file should never be accessible by anyone other than the user who created it. It is created with read-write file permissions for the user (600) only. These permissions should never be altered.
After successfully generating the key pair, copy the contents of the public key file $HOME/.ssh/id_rsa.pub to $HOME/.ssh/authorized_keys on all the systems you want to connect to with the SSH.
If the authorized_keys file already exists, append it with the contents of $HOME/.ssh/id_rsa.pub. If the .ssh/ directory does not exist in your home directory on the remote systems, it must be created so that only you, the owner, can access it.
To change the permissions for it, execute the command chmod 0700 $HOME/.ssh on the remote system. The $HOME/.ssh/authorized_keys file on each remote system must have the same permissions as the $HOME/.ssh/id_rsa.pub file created by ssh-keygen.
Change its permissions with the chmod 644 $HOME/.ssh/authorized_keys command on each remote system to which you will be connecting.
After creating an RSA key pair and distributing the public key to the remote systems, when the ssh <hostname> command is executed, the user will be prompted for the passphrase used to create the key pair instead of being prompted for a password for authentication.
Instead of entering the passphrase each time you connect to a remote system, the ssh-agent utility from the openssh-clients package can be used to remember the passphrase.
Additionally, if a graphical desktop is used and the openssh-askpass package is installed, the desktop can be configured to prompt the user for the passphrase after the user logs in to the graphical interface. While that graphical login session is active, the passphrase will be remembered for all terminals opened within that graphical session. To configure ssh-agent as a startup program, use the following steps:
|1.||Verify that the openssh-askpass package is installed. If it isn't, install it|
|2.||From the System menu on the top panel of the desktop, select Preferences, More Preferences, Sessions.|
|3.||When the Sessions window appears, select the Startup Programs tab.|
|4.||Click Add and enter /usr/bin/ssh-add as the startup command. Click OK|
|5.||Click Close to save the settings and exit.|
The next time the user logs in to the GUI, a dialog window will appear prompting the user for the passphrase. If the correct passphrase is entered, the user will not have to type the passphrase again when connecting to systems that contain the corresponding $HOME/.ssh/authorized_keys file.
If a graphical interface is not being used, the passphrase can be remembered by executing the following commands:
exec /usr/bin/ssh-agent $SHELL ssh-add
After you enter the correct passphrase, it will be remembered for that session or terminal window.
1. We assume that the user name is the same in both machines.
2. The user keys will be stored in ~/.ssh in both machines.
3. At the client, run 'ssh-keygen -t dsa' to generate a key pair. Accept default options by pressing return. Specially, do not enter any passphrase. (Option -d seems to be an alias of -t dsa in some platforms).
4. Change the permissions of the generated .pub file to 600 by commanding chmod 600 id_dsa.pub
5. Copy the public key to the server with scp id_dsa.pub '[email protected]:~/.ssh/authorized_keys'. (Caution: if that destination file already exists on the server, copy first to a different file foo and then append the contents with cat foo >> authorized_keys executed on the server).
6. Done! Verify that now you can connect directly from the client with ssh [email protected] without being prompted for a password.
7. If it doesn't work, verify that in the server your home directory, the .ssh subdirectory, and the authorized_keys file do not have writing permissions to others. If they do, they won't be considered to grant access. You can correct this with something like:
chmod 755 ~ chmod 700 ~/.ssh chmod 600 ~/.ssh/authorized_keys
8. If it still doesn't work, try changing the authorized_keys file name to authorized_keys2, or ask your system administrator what file name is ssh actually using.
9. If it worked, you can now run SCP in batch mode with the -B option, as in scp -B foofile '[email protected]:~/foodir/'.
Groupthink : Two Party System as Polyarchy : Corruption of Regulators : Bureaucracies : Understanding Micromanagers and Control Freaks : Toxic Managers : Harvard Mafia : Diplomatic Communication : Surviving a Bad Performance Review : Insufficient Retirement Funds as Immanent Problem of Neoliberal Regime : PseudoScience : Who Rules America : Neoliberalism : The Iron Law of Oligarchy : Libertarian Philosophy
War and Peace : Skeptical Finance : John Kenneth Galbraith :Talleyrand : Oscar Wilde : Otto Von Bismarck : Keynes : George Carlin : Skeptics : Propaganda : SE quotes : Language Design and Programming Quotes : Random IT-related quotes : Somerset Maugham : Marcus Aurelius : Kurt Vonnegut : Eric Hoffer : Winston Churchill : Napoleon Bonaparte : Ambrose Bierce : Bernard Shaw : Mark Twain Quotes
Vol 25, No.12 (December, 2013) Rational Fools vs. Efficient Crooks The efficient markets hypothesis : Political Skeptic Bulletin, 2013 : Unemployment Bulletin, 2010 : Vol 23, No.10 (October, 2011) An observation about corporate security departments : Slightly Skeptical Euromaydan Chronicles, June 2014 : Greenspan legacy bulletin, 2008 : Vol 25, No.10 (October, 2013) Cryptolocker Trojan (Win32/Crilock.A) : Vol 25, No.08 (August, 2013) Cloud providers as intelligence collection hubs : Financial Humor Bulletin, 2010 : Inequality Bulletin, 2009 : Financial Humor Bulletin, 2008 : Copyleft Problems Bulletin, 2004 : Financial Humor Bulletin, 2011 : Energy Bulletin, 2010 : Malware Protection Bulletin, 2010 : Vol 26, No.1 (January, 2013) Object-Oriented Cult : Political Skeptic Bulletin, 2011 : Vol 23, No.11 (November, 2011) Softpanorama classification of sysadmin horror stories : Vol 25, No.05 (May, 2013) Corporate bullshit as a communication method : Vol 25, No.06 (June, 2013) A Note on the Relationship of Brooks Law and Conway Law
Fifty glorious years (1950-2000): the triumph of the US computer engineering : Donald Knuth : TAoCP and its Influence of Computer Science : Richard Stallman : Linus Torvalds : Larry Wall : John K. Ousterhout : CTSS : Multix OS Unix History : Unix shell history : VI editor : History of pipes concept : Solaris : MS DOS : Programming Languages History : PL/1 : Simula 67 : C : History of GCC development : Scripting Languages : Perl history : OS History : Mail : DNS : SSH : CPU Instruction Sets : SPARC systems 1987-2006 : Norton Commander : Norton Utilities : Norton Ghost : Frontpage history : Malware Defense History : GNU Screen : OSS early history
The Peter Principle : Parkinson Law : 1984 : The Mythical Man-Month : How to Solve It by George Polya : The Art of Computer Programming : The Elements of Programming Style : The Unix Haterís Handbook : The Jargon file : The True Believer : Programming Pearls : The Good Soldier Svejk : The Power Elite
Most popular humor pages:
Manifest of the Softpanorama IT Slacker Society : Ten Commandments of the IT Slackers Society : Computer Humor Collection : BSD Logo Story : The Cuckoo's Egg : IT Slang : C++ Humor : ARE YOU A BBS ADDICT? : The Perl Purity Test : Object oriented programmers of all nations : Financial Humor : Financial Humor Bulletin, 2008 : Financial Humor Bulletin, 2010 : The Most Comprehensive Collection of Editor-related Humor : Programming Language Humor : Goldman Sachs related humor : Greenspan humor : C Humor : Scripting Humor : Real Programmers Humor : Web Humor : GPL-related Humor : OFM Humor : Politically Incorrect Humor : IDS Humor : "Linux Sucks" Humor : Russian Musical Humor : Best Russian Programmer Humor : Microsoft plans to buy Catholic Church : Richard Stallman Related Humor : Admin Humor : Perl-related Humor : Linus Torvalds Related humor : PseudoScience Related Humor : Networking Humor : Shell Humor : Financial Humor Bulletin, 2011 : Financial Humor Bulletin, 2012 : Financial Humor Bulletin, 2013 : Java Humor : Software Engineering Humor : Sun Solaris Related Humor : Education Humor : IBM Humor : Assembler-related Humor : VIM Humor : Computer Viruses Humor : Bright tomorrow is rescheduled to a day after tomorrow : Classic Computer Humor
The Last but not Least Technology is dominated by two types of people: those who understand what they do not manage and those who manage what they do not understand ~Archibald Putt. Ph.D
Copyright © 1996-2021 by Softpanorama Society. www.softpanorama.org was initially created as a service to the (now defunct) UN Sustainable Development Networking Programme (SDNP) without any remuneration. This document is an industrial compilation designed and created exclusively for educational use and is distributed under the Softpanorama Content License. Original materials copyright belong to respective owners. Quotes are made for educational purposes only in compliance with the fair use doctrine.
FAIR USE NOTICE This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available to advance understanding of computer science, IT technology, economic, scientific, and social issues. We believe this constitutes a 'fair use' of any such copyrighted material as provided by section 107 of the US Copyright Law according to which such material can be distributed without profit exclusively for research and educational purposes.
This is a Spartan WHYFF (We Help You For Free) site written by people for whom English is not a native language. Grammar and spelling errors should be expected. The site contain some broken links as it develops like a living tree...
|You can use PayPal to to buy a cup of coffee for authors of this site|
Last modified: March 12, 2019