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The following task map points to user procedures for using Secure Shell.
Users must generate a public/private key pair when their site implements host-based authentication or user public-key authentication. For additional options, see the ssh-keygen(1) man page.
Before You Begin
Determine from your system administrator if host-based authentication is configured.
myLocalHost% ssh-keygen -t rsa Generating public/private rsa key pair. …
where -t is the type of algorithm, one of rsa, dsa, or rsa1.
By default, the file name id_rsa, which represents an RSA v2 key, appears in parentheses. You can select this file by pressing the Return key. Or, you can type an alternative file name.
Enter file in which to save the key (/home/jdoe/.ssh/id_rsa):<Press Return>
The file name of the public key is created automatically by appending the string .pub to the name of the private key file.
This passphrase is used for encrypting your private key. A null entry is strongly discouraged. Note that the passphrase is not displayed when you type it in.
Enter passphrase (empty for no passphrase): <Type passphrase>
Enter same passphrase again: <Type passphrase> Your identification has been saved in /home/jdoe/.ssh/id_rsa. Your public key has been saved in /home/jdoe/.ssh/id_rsa.pub. The key fingerprint is: 0e:fb:3d:57:71:73:bf:58:b8:eb:f3:a3:aa:df:e0:d1 jdoe@myLocalHost
Check that the path to the key file is correct.
% ls ~/.ssh id_rsa id_rsa.pub
At this point, you have created a public/private key pair.
You can now log in to the remote host. For details, see How to Log In to a Remote Host With Secure Shell.
% cat /etc/ssh/ssh_host_dsa_key.pub | ssh RemoteHost \ 'cat >> ~./ssh/known_hosts && echo "Host key copied"'
Enter password: <Type password> Host key copied %
Type the command on one line with no backslash.
myLocalHost% cat $HOME/.ssh/id_rsa.pub | ssh myRemoteHost \ 'cat >> .ssh/authorized_keys && echo "Key copied"'
When the file is copied, the message “Key copied” is displayed.
Enter password: Type login password Key copied myLocalHost%
The following procedure does not change the private key. The procedure changes the authentication mechanism for the private key, the passphrase. For more information, see the ssh-keygen(1) man page.
Type the ssh-keygen command with the -p option, and answer the prompts.
myLocalHost% ssh-keygen -p Enter file which contains the private key (/home/jdoe/.ssh/id_rsa):<Press Return> Enter passphrase (empty for no passphrase): <Type passphrase> Enter same passphrase again: <Type passphrase>
where -p requests changing the passphrase of a private key file.
Type the ssh command, and specify the name of the remote host and your login.
myLocalHost% ssh myRemoteHost -l username
A prompt questions the authenticity of the remote host:
The authenticity of host 'myRemoteHost' can't be established. RSA key fingerprint in md5 is: 04:9f:bd:fc:3d:3e:d2:e7:49:fd:6e:18:4f:9c:26 Are you sure you want to continue connecting(yes/no)?
This prompt is normal for initial connections to remote hosts.
Are you sure you want to continue connecting(yes/no)? no
The administrator is responsible for updating the global /etc/ssh/ssh_known_hosts file. An updated ssh_known_hosts file prevents this prompt from appearing.
Are you sure you want to continue connecting(yes/no)? yes
Enter passphrase for key '/home/jdoe/.ssh/id_rsa': <Type passphrase>
jdoe@myRemoteHost's password: <Type password> Last login: Wed Sep 7 09:07:49 2011 from myLocalHost Oracle Corporation SunOS 5.11 September 2011 myRemoteHost%
The commands that you send are encrypted. Any responses that you receive are encrypted.
When you are finished, type exit or use your usual method for exiting your shell.
myRemoteHost% exit myRemoteHost% logout Connection to myRemoteHost closed myLocalHost%
If you do not want to type your passphrase and your password to use Secure Shell, you can use the agent daemon. Start the daemon at the beginning of the session. Then, store your private keys with the agent daemon by using the ssh-add command. If you have different accounts on different hosts, add the keys that you need for the session.
You can start the agent daemon manually when needed, as described in the following procedure.
myLocalHost% eval `ssh-agent` Agent pid 9892
myLocalHost% pgrep ssh-agent 9892
Type the ssh-add command.
myLocalHost% ssh-add Enter passphrase for /home/jdoe/.ssh/id_rsa: <Type passphrase> Identity added: /home/jdoe/.ssh/id_rsa(/home/jdoe/.ssh/id_rsa) myLocalHost%
myLocalHost% ssh myRemoteHost -l jdoe
You are not prompted for a passphrase.
Example 17-2 Using ssh-add Options
In this example, jdoe adds two keys to the agent daemon. The -l option is used to list all keys that are stored in the daemon. At the end of the session, the -D option is used to remove all the keys from the agent daemon.
myLocalHost% ssh-agent myLocalHost% ssh-add Enter passphrase for /home/jdoe/.ssh/id_rsa: <Type passphrase> Identity added: /home/jdoe/.ssh/id_rsa(/home/jdoe/.ssh/id_rsa) myLocalHost% ssh-add /home/jdoe/.ssh/id_dsa Enter passphrase for /home/jdoe/.ssh/id_dsa: <Type passphrase> Identity added: /home/jdoe/.ssh/id_dsa(/home/jdoe/.ssh/id_dsa) myLocalHost% ssh-add -l md5 1024 0e:fb:3d:53:71:77:bf:57:b8:eb:f7:a7:aa:df:e0:d1 /home/jdoe/.ssh/id_rsa(RSA) md5 1024 c1:d3:21:5e:40:60:c5:73:d8:87:09:3a:fa:5f:32:53 /home/jdoe/.ssh/id_dsa(DSA) User conducts Oracle Solaris Secure Shell transactions
myLocalHost% ssh-add -D Identity removed: /home/jdoe/.ssh/id_rsa(/home/jdoe/.ssh/id_rsa.pub) /home/jdoe/.ssh/id_dsa(DSA)
You can specify that a local port be forwarded to a remote host. Effectively, a socket is allocated to listen to the port on the local side. The connection from this port is made over a secure channel to the remote host. For example, you might specify port 143 to obtain email remotely with IMAP4. Similarly, a port can be specified on the remote side.
Before You Begin
To use port forwarding, the administrator must have enabled port forwarding on the remote Secure Shell server. For details, see How to Configure Port Forwarding in Secure Shell.
Specify the local port that listens for remote communication. Also, specify the remote host and the remote port that forward the communication.
myLocalHost% ssh -L localPort:remoteHost:remotePort
Specify the remote port that listens for remote communication. Also, specify the local host and the local port that forward the communication.
myLocalHost% ssh -R remotePort:localhost:localPort
Example 17-3 Using Local Port Forwarding to Receive Mail
The following example demonstrates how you can use local port forwarding to receive mail securely from a remote server.
myLocalHost% ssh -L 9143:myRemoteHost:143 myRemoteHost
This command forwards connections from port 9143 on myLocalHost to port 143. Port 143 is the IMAP v2 server port on myRemoteHost. When the user launches a mail application, the user specifies the local port number for the IMAP server, as in localhost:9143.
Do not confuse localhost with myLocalHost. myLocalHost is a hypothetical host name. localhost is a keyword that identifies your local system.
Example 17-4 Using Remote Port Forwarding to Communicate Outside of a Firewall
This example demonstrates how a user in an enterprise environment can forward connections from a host on an external network to a host inside a corporate firewall.
myLocalHost% ssh -R 9022:myLocalHost:22 myOutsideHost
This command forwards connections from port 9022 on myOutsideHost to port 22, the sshd server, on the local host.
myOutsideHost% ssh -p 9022 localhost myLocalHost%
The following procedure shows how to use the scp command to copy encrypted files between hosts. You can copy encrypted files either between a local host and a remote host, or between two remote hosts. The scp command prompts for authentication. For more information, see the scp(1) man page.
Note - The audit service can audit sftp transactions through the ft audit class. For scp, the audit service can audit access and exit for the ssh session.
Specify the source file, the user name at the remote destination, and the destination directory.
myLocalHost% scp myfile.1 jdoe@myRemoteHost:~
Enter passphrase for key '/home/jdoe/.ssh/id_rsa': <Type passphrase> myfile.1 25% |******* | 640 KB 0:20 ETA myfile.1
After you type the passphrase, a progress meter is displayed. See the second line in the preceding output. The progress meter displays:
The file name
The percentage of the file that has been transferred
A series of asterisks that indicate the percentage of the file that has been transferred
The quantity of data transferred
The estimated time of arrival, or ETA, of the complete file (that is, the remaining amount of time)
Example 17-5 Specifying a Port When Using the sftp Command
In this example, the user wants the sftp command to use a specific port. The user uses the -o option to specify the port.
% sftp -o port=2222 guest@RemoteFileServer
You can use Secure Shell to make a connection from a host inside a firewall to a host outside the firewall. This task is done by specifying a proxy command for ssh either in a configuration file or as an option on the command line. For the command-line option, see Example 17-6.
In general, you can customize your ssh interactions through a configuration file.
You can customize either your own personal file in ~/.ssh/config.
Or, you can use the settings in the administrative configuration file, /etc/ssh/ssh_config.
The files can be customized with two types of proxy commands. One proxy command is for HTTP connections. The other proxy command is for SOCKS5 connections. For more information, see the ssh_config(4) man page.
Use the following syntax to add as many lines as you need:
[Host outside-host] ProxyCommand proxy-command [-h proxy-server] \ [-p proxy-port] outside-host|%h outside-port|%p
Limits the proxy command specification to instances when a remote host name is specified on the command line. If you use a wildcard for outside-host, you apply the proxy command specification to a set of hosts.
Specifies the proxy command.
The command can be either of the following:
/usr/lib/ssh/ssh-http-proxy-connect for HTTP connections
/usr/lib/ssh/ssh-socks5-proxy-connect for SOCKS5 connections
These options specify a proxy server and a proxy port, respectively. If present, the proxies override any environment variables that specify proxy servers and proxy ports, such as HTTPPROXY, HTTPPROXYPORT, SOCKS5_PORT, SOCKS5_SERVER, and http_proxy. The http_proxy variable specifies a URL. If the options are not used, then the relevant environment variables must be set. For more information, see the ssh-socks5-proxy-connect(1) and ssh-http-proxy-connect(1) man pages.
Designates a specific host to connect to. Use the %h substitution argument to specify the host on the command line.
Designates a specific port to connect to. Use the %p substitution argument to specify the port on the command line. By specifying %h and %p without using the Host outside-host option, the proxy command is applied to the host argument whenever the ssh command is invoked.
For example, type the following:
myLocalHost% ssh myOutsideHost
This command looks for a proxy command specification for myOutsideHost in your personal configuration file. If the specification is not found, then the command looks in the system-wide configuration file, /etc/ssh/ssh_config. The proxy command is substituted for the ssh command.
Example 17-6 Connecting to Hosts Outside a Firewall From the Command Line
How to Set Up Default Connections to Hosts Outside a Firewall explains how to specify a proxy command in a configuration file. In this example, a proxy command is specified on the ssh command line.
% ssh -o'Proxycommand=/usr/lib/ssh/ssh-http-proxy-connect \ -h myProxyServer -p 8080 myOutsideHost 22' myOutsideHost
The -o option to the ssh command provides a command-line method of specifying a proxy command. This example command does the following:
Substitutes the HTTP proxy command for ssh
Uses port 8080 and myProxyServer as the proxy server
Connects to port 22 on myOutsideHost