ssh.0 revision 218769
1203945SweongyoSSH(1) OpenBSD Reference Manual SSH(1) 2203945Sweongyo 3203945SweongyoNAME 4203945Sweongyo ssh - OpenSSH SSH client (remote login program) 5203945Sweongyo 6203945SweongyoSYNOPSIS 7203945Sweongyo ssh [-1246AaCfgKkMNnqsTtVvXxYy] [-b bind_address] [-c cipher_spec] 8203945Sweongyo [-D [bind_address:]port] [-e escape_char] [-F configfile] [-I pkcs11] 9203945Sweongyo [-i identity_file] [-L [bind_address:]port:host:hostport] 10203945Sweongyo [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port] 11203945Sweongyo [-R [bind_address:]port:host:hostport] [-S ctl_path] [-W host:port] 12203945Sweongyo [-w local_tun[:remote_tun]] [user@]hostname [command] 13203945Sweongyo 14203945SweongyoDESCRIPTION 15203945Sweongyo ssh (SSH client) is a program for logging into a remote machine and for 16203945Sweongyo executing commands on a remote machine. It is intended to replace rlogin 17203945Sweongyo and rsh, and provide secure encrypted communications between two 18203945Sweongyo untrusted hosts over an insecure network. X11 connections and arbitrary 19203945Sweongyo TCP ports can also be forwarded over the secure channel. 20203945Sweongyo 21203945Sweongyo ssh connects and logs into the specified hostname (with optional user 22203945Sweongyo name). The user must prove his/her identity to the remote machine using 23203945Sweongyo one of several methods depending on the protocol version used (see 24203945Sweongyo below). 25203945Sweongyo 26203945Sweongyo If command is specified, it is executed on the remote host instead of a 27203945Sweongyo login shell. 28203945Sweongyo 29203945Sweongyo The options are as follows: 30203945Sweongyo 31203945Sweongyo -1 Forces ssh to try protocol version 1 only. 32203945Sweongyo 33203945Sweongyo -2 Forces ssh to try protocol version 2 only. 34203945Sweongyo 35203945Sweongyo -4 Forces ssh to use IPv4 addresses only. 36203945Sweongyo 37203945Sweongyo -6 Forces ssh to use IPv6 addresses only. 38203945Sweongyo 39203945Sweongyo -A Enables forwarding of the authentication agent connection. This 40203945Sweongyo can also be specified on a per-host basis in a configuration 41203945Sweongyo file. 42203945Sweongyo 43203945Sweongyo Agent forwarding should be enabled with caution. Users with the 44203945Sweongyo ability to bypass file permissions on the remote host (for the 45203945Sweongyo agent's UNIX-domain socket) can access the local agent through 46203945Sweongyo the forwarded connection. An attacker cannot obtain key material 47203945Sweongyo from the agent, however they can perform operations on the keys 48203945Sweongyo that enable them to authenticate using the identities loaded into 49203945Sweongyo the agent. 50203945Sweongyo 51203945Sweongyo -a Disables forwarding of the authentication agent connection. 52203945Sweongyo 53203945Sweongyo -b bind_address 54203945Sweongyo Use bind_address on the local machine as the source address of 55203945Sweongyo the connection. Only useful on systems with more than one 56203945Sweongyo address. 57203945Sweongyo 58203945Sweongyo -C Requests compression of all data (including stdin, stdout, 59203945Sweongyo stderr, and data for forwarded X11 and TCP connections). The 60203945Sweongyo compression algorithm is the same used by gzip(1), and the 61203945Sweongyo ``level'' can be controlled by the CompressionLevel option for 62203945Sweongyo protocol version 1. Compression is desirable on modem lines and 63203945Sweongyo other slow connections, but will only slow down things on fast 64203945Sweongyo networks. The default value can be set on a host-by-host basis 65203945Sweongyo in the configuration files; see the Compression option. 66203945Sweongyo 67203945Sweongyo -c cipher_spec 68203945Sweongyo Selects the cipher specification for encrypting the session. 69203945Sweongyo 70203945Sweongyo Protocol version 1 allows specification of a single cipher. The 71206358Srpaulo supported values are ``3des'', ``blowfish'', and ``des''. 3des 72203945Sweongyo (triple-des) is an encrypt-decrypt-encrypt triple with three 73203945Sweongyo different keys. It is believed to be secure. blowfish is a fast 74203945Sweongyo block cipher; it appears very secure and is much faster than 75203945Sweongyo 3des. des is only supported in the ssh client for 76227309Sed interoperability with legacy protocol 1 implementations that do 77227309Sed not support the 3des cipher. Its use is strongly discouraged due 78203945Sweongyo to cryptographic weaknesses. The default is ``3des''. 79203945Sweongyo 80203945Sweongyo For protocol version 2, cipher_spec is a comma-separated list of 81203945Sweongyo ciphers listed in order of preference. See the Ciphers keyword 82203945Sweongyo in ssh_config(5) for more information. 83203945Sweongyo 84203945Sweongyo -D [bind_address:]port 85203945Sweongyo Specifies a local ``dynamic'' application-level port forwarding. 86203945Sweongyo This works by allocating a socket to listen to port on the local 87203945Sweongyo side, optionally bound to the specified bind_address. Whenever a 88203945Sweongyo connection is made to this port, the connection is forwarded over 89203945Sweongyo the secure channel, and the application protocol is then used to 90203945Sweongyo determine where to connect to from the remote machine. Currently 91203945Sweongyo the SOCKS4 and SOCKS5 protocols are supported, and ssh will act 92203945Sweongyo as a SOCKS server. Only root can forward privileged ports. 93203945Sweongyo Dynamic port forwardings can also be specified in the 94203945Sweongyo configuration file. 95203945Sweongyo 96203945Sweongyo IPv6 addresses can be specified by enclosing the address in 97203945Sweongyo square brackets. Only the superuser can forward privileged 98203945Sweongyo ports. By default, the local port is bound in accordance with 99203945Sweongyo the GatewayPorts setting. However, an explicit bind_address may 100203945Sweongyo be used to bind the connection to a specific address. The 101203945Sweongyo bind_address of ``localhost'' indicates that the listening port 102203945Sweongyo be bound for local use only, while an empty address or `*' 103203945Sweongyo indicates that the port should be available from all interfaces. 104203945Sweongyo 105203945Sweongyo -e escape_char 106203945Sweongyo Sets the escape character for sessions with a pty (default: `~'). 107203945Sweongyo The escape character is only recognized at the beginning of a 108203945Sweongyo line. The escape character followed by a dot (`.') closes the 109203945Sweongyo connection; followed by control-Z suspends the connection; and 110203945Sweongyo followed by itself sends the escape character once. Setting the 111203945Sweongyo character to ``none'' disables any escapes and makes the session 112203945Sweongyo fully transparent. 113203945Sweongyo 114203945Sweongyo -F configfile 115203945Sweongyo Specifies an alternative per-user configuration file. If a 116203945Sweongyo configuration file is given on the command line, the system-wide 117203945Sweongyo configuration file (/etc/ssh/ssh_config) will be ignored. The 118203945Sweongyo default for the per-user configuration file is ~/.ssh/config. 119203945Sweongyo 120203945Sweongyo -f Requests ssh to go to background just before command execution. 121203945Sweongyo This is useful if ssh is going to ask for passwords or 122203945Sweongyo passphrases, but the user wants it in the background. This 123203945Sweongyo implies -n. The recommended way to start X11 programs at a 124203945Sweongyo remote site is with something like ssh -f host xterm. 125203945Sweongyo 126203945Sweongyo If the ExitOnForwardFailure configuration option is set to 127203945Sweongyo ``yes'', then a client started with -f will wait for all remote 128203945Sweongyo port forwards to be successfully established before placing 129203945Sweongyo itself in the background. 130203945Sweongyo 131203945Sweongyo -g Allows remote hosts to connect to local forwarded ports. 132203945Sweongyo 133203945Sweongyo -I pkcs11 134203945Sweongyo Specify the PKCS#11 shared library ssh should use to communicate 135203945Sweongyo with a PKCS#11 token providing the user's private RSA key. 136203945Sweongyo 137203945Sweongyo -i identity_file 138204922Sweongyo Selects a file from which the identity (private key) for public 139203945Sweongyo key authentication is read. The default is ~/.ssh/identity for 140203945Sweongyo protocol version 1, and ~/.ssh/id_dsa, ~/.ssh/id_ecdsa and 141203945Sweongyo ~/.ssh/id_rsa for protocol version 2. Identity files may also be 142203945Sweongyo specified on a per-host basis in the configuration file. It is 143203945Sweongyo possible to have multiple -i options (and multiple identities 144203945Sweongyo specified in configuration files). ssh will also try to load 145203945Sweongyo certificate information from the filename obtained by appending 146203945Sweongyo -cert.pub to identity filenames. 147203945Sweongyo 148203945Sweongyo -K Enables GSSAPI-based authentication and forwarding (delegation) 149203945Sweongyo of GSSAPI credentials to the server. 150203945Sweongyo 151203945Sweongyo -k Disables forwarding (delegation) of GSSAPI credentials to the 152203945Sweongyo server. 153203945Sweongyo 154203945Sweongyo -L [bind_address:]port:host:hostport 155203945Sweongyo Specifies that the given port on the local (client) host is to be 156203945Sweongyo forwarded to the given host and port on the remote side. This 157203945Sweongyo works by allocating a socket to listen to port on the local side, 158203945Sweongyo optionally bound to the specified bind_address. Whenever a 159203945Sweongyo connection is made to this port, the connection is forwarded over 160203945Sweongyo the secure channel, and a connection is made to host port 161203945Sweongyo hostport from the remote machine. Port forwardings can also be 162203945Sweongyo specified in the configuration file. IPv6 addresses can be 163203945Sweongyo specified by enclosing the address in square brackets. Only the 164203945Sweongyo superuser can forward privileged ports. By default, the local 165203945Sweongyo port is bound in accordance with the GatewayPorts setting. 166203945Sweongyo However, an explicit bind_address may be used to bind the 167203945Sweongyo connection to a specific address. The bind_address of 168203945Sweongyo ``localhost'' indicates that the listening port be bound for 169203945Sweongyo local use only, while an empty address or `*' indicates that the 170203945Sweongyo port should be available from all interfaces. 171203945Sweongyo 172203945Sweongyo -l login_name 173203945Sweongyo Specifies the user to log in as on the remote machine. This also 174203945Sweongyo may be specified on a per-host basis in the configuration file. 175203945Sweongyo 176203945Sweongyo -M Places the ssh client into ``master'' mode for connection 177203945Sweongyo sharing. Multiple -M options places ssh into ``master'' mode 178203945Sweongyo with confirmation required before slave connections are accepted. 179203945Sweongyo Refer to the description of ControlMaster in ssh_config(5) for 180203945Sweongyo details. 181203945Sweongyo 182203945Sweongyo -m mac_spec 183203945Sweongyo Additionally, for protocol version 2 a comma-separated list of 184203945Sweongyo MAC (message authentication code) algorithms can be specified in 185203945Sweongyo order of preference. See the MACs keyword for more information. 186203945Sweongyo 187203945Sweongyo -N Do not execute a remote command. This is useful for just 188203945Sweongyo forwarding ports (protocol version 2 only). 189203945Sweongyo 190203945Sweongyo -n Redirects stdin from /dev/null (actually, prevents reading from 191203945Sweongyo stdin). This must be used when ssh is run in the background. A 192203945Sweongyo common trick is to use this to run X11 programs on a remote 193203945Sweongyo machine. For example, ssh -n shadows.cs.hut.fi emacs & will 194203945Sweongyo start an emacs on shadows.cs.hut.fi, and the X11 connection will 195203945Sweongyo be automatically forwarded over an encrypted channel. The ssh 196228621Sbschmidt program will be put in the background. (This does not work if 197228621Sbschmidt ssh needs to ask for a password or passphrase; see also the -f 198203945Sweongyo option.) 199203945Sweongyo 200203945Sweongyo -O ctl_cmd 201203945Sweongyo Control an active connection multiplexing master process. When 202203945Sweongyo the -O option is specified, the ctl_cmd argument is interpreted 203203945Sweongyo and passed to the master process. Valid commands are: ``check'' 204203945Sweongyo (check that the master process is running), ``forward'' (request 205203945Sweongyo forwardings without command execution) and ``exit'' (request the 206203945Sweongyo master to exit). 207203945Sweongyo 208203945Sweongyo -o option 209203945Sweongyo Can be used to give options in the format used in the 210203945Sweongyo configuration file. This is useful for specifying options for 211203945Sweongyo which there is no separate command-line flag. For full details 212203945Sweongyo of the options listed below, and their possible values, see 213203945Sweongyo ssh_config(5). 214203945Sweongyo 215203945Sweongyo AddressFamily 216203945Sweongyo BatchMode 217203945Sweongyo BindAddress 218203945Sweongyo ChallengeResponseAuthentication 219203945Sweongyo CheckHostIP 220203945Sweongyo Cipher 221203945Sweongyo Ciphers 222203945Sweongyo ClearAllForwardings 223203945Sweongyo Compression 224203945Sweongyo CompressionLevel 225203945Sweongyo ConnectionAttempts 226203945Sweongyo ConnectTimeout 227203945Sweongyo ControlMaster 228203945Sweongyo ControlPath 229203945Sweongyo DynamicForward 230203945Sweongyo EscapeChar 231203945Sweongyo ExitOnForwardFailure 232203945Sweongyo ForwardAgent 233203945Sweongyo ForwardX11 234203945Sweongyo ForwardX11Trusted 235203945Sweongyo GatewayPorts 236203945Sweongyo GlobalKnownHostsFile 237203945Sweongyo GSSAPIAuthentication 238203945Sweongyo GSSAPIDelegateCredentials 239203945Sweongyo HashKnownHosts 240203945Sweongyo Host 241203945Sweongyo HostbasedAuthentication 242203945Sweongyo HostKeyAlgorithms 243203945Sweongyo HostKeyAlias 244203945Sweongyo HostName 245203945Sweongyo IdentityFile 246203945Sweongyo IdentitiesOnly 247203945Sweongyo IPQoS 248203945Sweongyo KbdInteractiveDevices 249203945Sweongyo KexAlgorithms 250203945Sweongyo LocalCommand 251203945Sweongyo LocalForward 252203945Sweongyo LogLevel 253203945Sweongyo MACs 254203945Sweongyo NoHostAuthenticationForLocalhost 255203945Sweongyo NumberOfPasswordPrompts 256203945Sweongyo PasswordAuthentication 257203945Sweongyo PermitLocalCommand 258203945Sweongyo PKCS11Provider 259203945Sweongyo Port 260203945Sweongyo PreferredAuthentications 261203945Sweongyo Protocol 262203945Sweongyo ProxyCommand 263203945Sweongyo PubkeyAuthentication 264203945Sweongyo RekeyLimit 265203945Sweongyo RemoteForward 266203945Sweongyo RhostsRSAAuthentication 267203945Sweongyo RSAAuthentication 268203945Sweongyo SendEnv 269203945Sweongyo ServerAliveInterval 270203945Sweongyo ServerAliveCountMax 271203945Sweongyo StrictHostKeyChecking 272203945Sweongyo TCPKeepAlive 273203945Sweongyo Tunnel 274203945Sweongyo TunnelDevice 275203945Sweongyo UsePrivilegedPort 276203945Sweongyo User 277203945Sweongyo UserKnownHostsFile 278203945Sweongyo VerifyHostKeyDNS 279203945Sweongyo VisualHostKey 280203945Sweongyo XAuthLocation 281203945Sweongyo 282203945Sweongyo -p port 283203945Sweongyo Port to connect to on the remote host. This can be specified on 284203945Sweongyo a per-host basis in the configuration file. 285203945Sweongyo 286203945Sweongyo -q Quiet mode. Causes most warning and diagnostic messages to be 287203945Sweongyo suppressed. 288203945Sweongyo 289203945Sweongyo -R [bind_address:]port:host:hostport 290203945Sweongyo Specifies that the given port on the remote (server) host is to 291203945Sweongyo be forwarded to the given host and port on the local side. This 292203945Sweongyo works by allocating a socket to listen to port on the remote 293203945Sweongyo side, and whenever a connection is made to this port, the 294203945Sweongyo connection is forwarded over the secure channel, and a connection 295203945Sweongyo is made to host port hostport from the local machine. 296203945Sweongyo 297203945Sweongyo Port forwardings can also be specified in the configuration file. 298203945Sweongyo Privileged ports can be forwarded only when logging in as root on 299203945Sweongyo the remote machine. IPv6 addresses can be specified by enclosing 300203945Sweongyo the address in square braces. 301203945Sweongyo 302203945Sweongyo By default, the listening socket on the server will be bound to 303203945Sweongyo the loopback interface only. This may be overridden by 304203945Sweongyo specifying a bind_address. An empty bind_address, or the address 305203945Sweongyo `*', indicates that the remote socket should listen on all 306203945Sweongyo interfaces. Specifying a remote bind_address will only succeed 307203945Sweongyo if the server's GatewayPorts option is enabled (see 308203945Sweongyo sshd_config(5)). 309203945Sweongyo 310203945Sweongyo If the port argument is `0', the listen port will be dynamically 311203945Sweongyo allocated on the server and reported to the client at run time. 312203945Sweongyo When used together with -O forward the allocated port will be 313203945Sweongyo printed to the standard output. 314203945Sweongyo 315203945Sweongyo -S ctl_path 316203945Sweongyo Specifies the location of a control socket for connection 317203945Sweongyo sharing, or the string ``none'' to disable connection sharing. 318203945Sweongyo Refer to the description of ControlPath and ControlMaster in 319203945Sweongyo ssh_config(5) for details. 320203945Sweongyo 321203945Sweongyo -s May be used to request invocation of a subsystem on the remote 322203945Sweongyo system. Subsystems are a feature of the SSH2 protocol which 323203945Sweongyo facilitate the use of SSH as a secure transport for other 324203945Sweongyo applications (eg. sftp(1)). The subsystem is specified as the 325203945Sweongyo remote command. 326203945Sweongyo 327203945Sweongyo -T Disable pseudo-tty allocation. 328203945Sweongyo 329203945Sweongyo -t Force pseudo-tty allocation. This can be used to execute 330203945Sweongyo arbitrary screen-based programs on a remote machine, which can be 331203945Sweongyo very useful, e.g. when implementing menu services. Multiple -t 332203945Sweongyo options force tty allocation, even if ssh has no local tty. 333203945Sweongyo 334203945Sweongyo -V Display the version number and exit. 335203945Sweongyo 336203945Sweongyo -v Verbose mode. Causes ssh to print debugging messages about its 337203945Sweongyo progress. This is helpful in debugging connection, 338203945Sweongyo authentication, and configuration problems. Multiple -v options 339203945Sweongyo increase the verbosity. The maximum is 3. 340203945Sweongyo 341203945Sweongyo -W host:port 342203945Sweongyo Requests that standard input and output on the client be 343203945Sweongyo forwarded to host on port over the secure channel. Implies -N, 344203945Sweongyo -T, ExitOnForwardFailure and ClearAllForwardings and works with 345203945Sweongyo Protocol version 2 only. 346203945Sweongyo 347203945Sweongyo -w local_tun[:remote_tun] 348203945Sweongyo Requests tunnel device forwarding with the specified tun(4) 349203945Sweongyo devices between the client (local_tun) and the server 350203945Sweongyo (remote_tun). 351203945Sweongyo 352203945Sweongyo The devices may be specified by numerical ID or the keyword 353203945Sweongyo ``any'', which uses the next available tunnel device. If 354203945Sweongyo remote_tun is not specified, it defaults to ``any''. See also 355203945Sweongyo the Tunnel and TunnelDevice directives in ssh_config(5). If the 356203945Sweongyo Tunnel directive is unset, it is set to the default tunnel mode, 357203945Sweongyo which is ``point-to-point''. 358203945Sweongyo 359203945Sweongyo -X Enables X11 forwarding. This can also be specified on a per-host 360203945Sweongyo basis in a configuration file. 361203945Sweongyo 362203945Sweongyo X11 forwarding should be enabled with caution. Users with the 363203945Sweongyo ability to bypass file permissions on the remote host (for the 364203945Sweongyo user's X authorization database) can access the local X11 display 365203945Sweongyo through the forwarded connection. An attacker may then be able 366203945Sweongyo to perform activities such as keystroke monitoring. 367203945Sweongyo 368203945Sweongyo For this reason, X11 forwarding is subjected to X11 SECURITY 369203945Sweongyo extension restrictions by default. Please refer to the ssh -Y 370203945Sweongyo option and the ForwardX11Trusted directive in ssh_config(5) for 371203945Sweongyo more information. 372203945Sweongyo 373203945Sweongyo -x Disables X11 forwarding. 374203945Sweongyo 375203945Sweongyo -Y Enables trusted X11 forwarding. Trusted X11 forwardings are not 376203945Sweongyo subjected to the X11 SECURITY extension controls. 377203945Sweongyo 378203945Sweongyo -y Send log information using the syslog(3) system module. By 379203945Sweongyo default this information is sent to stderr. 380203945Sweongyo 381203945Sweongyo ssh may additionally obtain configuration data from a per-user 382203945Sweongyo configuration file and a system-wide configuration file. The file format 383203945Sweongyo and configuration options are described in ssh_config(5). 384203945Sweongyo 385203945SweongyoAUTHENTICATION 386203945Sweongyo The OpenSSH SSH client supports SSH protocols 1 and 2. The default is to 387203945Sweongyo use protocol 2 only, though this can be changed via the Protocol option 388203945Sweongyo in ssh_config(5) or the -1 and -2 options (see above). Both protocols 389203945Sweongyo support similar authentication methods, but protocol 2 is the default 390203945Sweongyo since it provides additional mechanisms for confidentiality (the traffic 391203945Sweongyo is encrypted using AES, 3DES, Blowfish, CAST128, or Arcfour) and 392203945Sweongyo integrity (hmac-md5, hmac-sha1, umac-64, hmac-ripemd160). Protocol 1 393203945Sweongyo lacks a strong mechanism for ensuring the integrity of the connection. 394203945Sweongyo 395203945Sweongyo The methods available for authentication are: GSSAPI-based 396203945Sweongyo authentication, host-based authentication, public key authentication, 397203945Sweongyo challenge-response authentication, and password authentication. 398203945Sweongyo Authentication methods are tried in the order specified above, though 399203945Sweongyo protocol 2 has a configuration option to change the default order: 400203945Sweongyo PreferredAuthentications. 401203945Sweongyo 402203945Sweongyo Host-based authentication works as follows: If the machine the user logs 403203945Sweongyo in from is listed in /etc/hosts.equiv or /etc/shosts.equiv on the remote 404203945Sweongyo machine, and the user names are the same on both sides, or if the files 405203945Sweongyo ~/.rhosts or ~/.shosts exist in the user's home directory on the remote 406203945Sweongyo machine and contain a line containing the name of the client machine and 407203945Sweongyo the name of the user on that machine, the user is considered for login. 408203945Sweongyo Additionally, the server must be able to verify the client's host key 409203945Sweongyo (see the description of /etc/ssh/ssh_known_hosts and ~/.ssh/known_hosts, 410203945Sweongyo below) for login to be permitted. This authentication method closes 411203945Sweongyo security holes due to IP spoofing, DNS spoofing, and routing spoofing. 412203945Sweongyo [Note to the administrator: /etc/hosts.equiv, ~/.rhosts, and the 413203945Sweongyo rlogin/rsh protocol in general, are inherently insecure and should be 414203945Sweongyo disabled if security is desired.] 415203945Sweongyo 416203945Sweongyo Public key authentication works as follows: The scheme is based on 417203945Sweongyo public-key cryptography, using cryptosystems where encryption and 418203945Sweongyo decryption are done using separate keys, and it is unfeasible to derive 419203945Sweongyo the decryption key from the encryption key. The idea is that each user 420203945Sweongyo creates a public/private key pair for authentication purposes. The 421203945Sweongyo server knows the public key, and only the user knows the private key. 422203945Sweongyo ssh implements public key authentication protocol automatically, using 423203945Sweongyo one of the DSA, ECDSA or RSA algorithms. Protocol 1 is restricted to 424203945Sweongyo using only RSA keys, but protocol 2 may use any. The HISTORY section of 425203945Sweongyo ssl(8) contains a brief discussion of the DSA and RSA algorithms. 426203945Sweongyo 427203945Sweongyo The file ~/.ssh/authorized_keys lists the public keys that are permitted 428203945Sweongyo for logging in. When the user logs in, the ssh program tells the server 429203945Sweongyo which key pair it would like to use for authentication. The client 430203945Sweongyo proves that it has access to the private key and the server checks that 431203945Sweongyo the corresponding public key is authorized to accept the account. 432203945Sweongyo 433203945Sweongyo The user creates his/her key pair by running ssh-keygen(1). This stores 434203945Sweongyo the private key in ~/.ssh/identity (protocol 1), ~/.ssh/id_dsa (protocol 435203945Sweongyo 2 DSA), ~/.ssh/id_ecdsa (protocol 2 ECDSA), or ~/.ssh/id_rsa (protocol 2 436203945Sweongyo RSA) and stores the public key in ~/.ssh/identity.pub (protocol 1), 437203945Sweongyo ~/.ssh/id_dsa.pub (protocol 2 DSA), ~/.ssh/id_ecdsa.pub (protocol 2 438203945Sweongyo ECDSA), or ~/.ssh/id_rsa.pub (protocol 2 RSA) in the user's home 439203945Sweongyo directory. The user should then copy the public key to 440203945Sweongyo ~/.ssh/authorized_keys in his/her home directory on the remote machine. 441203945Sweongyo The authorized_keys file corresponds to the conventional ~/.rhosts file, 442203945Sweongyo and has one key per line, though the lines can be very long. After this, 443203945Sweongyo the user can log in without giving the password. 444203945Sweongyo 445203945Sweongyo A variation on public key authentication is available in the form of 446203945Sweongyo certificate authentication: instead of a set of public/private keys, 447203945Sweongyo signed certificates are used. This has the advantage that a single 448203945Sweongyo trusted certification authority can be used in place of many 449203945Sweongyo public/private keys. See the CERTIFICATES section of ssh-keygen(1) for 450203945Sweongyo more information. 451203945Sweongyo 452203945Sweongyo The most convenient way to use public key or certificate authentication 453203945Sweongyo may be with an authentication agent. See ssh-agent(1) for more 454203945Sweongyo information. 455203945Sweongyo 456203945Sweongyo Challenge-response authentication works as follows: The server sends an 457203945Sweongyo arbitrary "challenge" text, and prompts for a response. Protocol 2 458203945Sweongyo allows multiple challenges and responses; protocol 1 is restricted to 459203945Sweongyo just one challenge/response. Examples of challenge-response 460203945Sweongyo authentication include BSD Authentication (see login.conf(5)) and PAM 461203945Sweongyo (some non-OpenBSD systems). 462203945Sweongyo 463203945Sweongyo Finally, if other authentication methods fail, ssh prompts the user for a 464203945Sweongyo password. The password is sent to the remote host for checking; however, 465203945Sweongyo since all communications are encrypted, the password cannot be seen by 466203945Sweongyo someone listening on the network. 467203945Sweongyo 468203945Sweongyo ssh automatically maintains and checks a database containing 469203945Sweongyo identification for all hosts it has ever been used with. Host keys are 470203945Sweongyo stored in ~/.ssh/known_hosts in the user's home directory. Additionally, 471203945Sweongyo the file /etc/ssh/ssh_known_hosts is automatically checked for known 472203945Sweongyo hosts. Any new hosts are automatically added to the user's file. If a 473203945Sweongyo host's identification ever changes, ssh warns about this and disables 474203945Sweongyo password authentication to prevent server spoofing or man-in-the-middle 475203945Sweongyo attacks, which could otherwise be used to circumvent the encryption. The 476203945Sweongyo StrictHostKeyChecking option can be used to control logins to machines 477203945Sweongyo whose host key is not known or has changed. 478203945Sweongyo 479203945Sweongyo When the user's identity has been accepted by the server, the server 480203945Sweongyo either executes the given command, or logs into the machine and gives the 481203945Sweongyo user a normal shell on the remote machine. All communication with the 482203945Sweongyo remote command or shell will be automatically encrypted. 483203945Sweongyo 484203945Sweongyo If a pseudo-terminal has been allocated (normal login session), the user 485203945Sweongyo may use the escape characters noted below. 486203945Sweongyo 487203945Sweongyo If no pseudo-tty has been allocated, the session is transparent and can 488203945Sweongyo be used to reliably transfer binary data. On most systems, setting the 489203945Sweongyo escape character to ``none'' will also make the session transparent even 490203945Sweongyo if a tty is used. 491203945Sweongyo 492203945Sweongyo The session terminates when the command or shell on the remote machine 493203945Sweongyo exits and all X11 and TCP connections have been closed. 494203945Sweongyo 495203945SweongyoESCAPE CHARACTERS 496203945Sweongyo When a pseudo-terminal has been requested, ssh supports a number of 497203945Sweongyo functions through the use of an escape character. 498203945Sweongyo 499203945Sweongyo A single tilde character can be sent as ~~ or by following the tilde by a 500203945Sweongyo character other than those described below. The escape character must 501203945Sweongyo always follow a newline to be interpreted as special. The escape 502203945Sweongyo character can be changed in configuration files using the EscapeChar 503203945Sweongyo configuration directive or on the command line by the -e option. 504203945Sweongyo 505203945Sweongyo The supported escapes (assuming the default `~') are: 506203945Sweongyo 507203945Sweongyo ~. Disconnect. 508203945Sweongyo 509203945Sweongyo ~^Z Background ssh. 510203945Sweongyo 511203945Sweongyo ~# List forwarded connections. 512203945Sweongyo 513203945Sweongyo ~& Background ssh at logout when waiting for forwarded connection / 514203945Sweongyo X11 sessions to terminate. 515203945Sweongyo 516203945Sweongyo ~? Display a list of escape characters. 517203945Sweongyo 518203945Sweongyo ~B Send a BREAK to the remote system (only useful for SSH protocol 519203945Sweongyo version 2 and if the peer supports it). 520203945Sweongyo 521203945Sweongyo ~C Open command line. Currently this allows the addition of port 522203945Sweongyo forwardings using the -L, -R and -D options (see above). It also 523203945Sweongyo allows the cancellation of existing remote port-forwardings using 524203945Sweongyo -KR[bind_address:]port. !command allows the user to execute a 525203945Sweongyo local command if the PermitLocalCommand option is enabled in 526203945Sweongyo ssh_config(5). Basic help is available, using the -h option. 527203945Sweongyo 528203945Sweongyo ~R Request rekeying of the connection (only useful for SSH protocol 529203945Sweongyo version 2 and if the peer supports it). 530203945Sweongyo 531203945SweongyoTCP FORWARDING 532203945Sweongyo Forwarding of arbitrary TCP connections over the secure channel can be 533203945Sweongyo specified either on the command line or in a configuration file. One 534204257Sweongyo possible application of TCP forwarding is a secure connection to a mail 535203945Sweongyo server; another is going through firewalls. 536203945Sweongyo 537203945Sweongyo In the example below, we look at encrypting communication between an IRC 538203945Sweongyo client and server, even though the IRC server does not directly support 539203945Sweongyo encrypted communications. This works as follows: the user connects to 540203945Sweongyo the remote host using ssh, specifying a port to be used to forward 541203945Sweongyo connections to the remote server. After that it is possible to start the 542203945Sweongyo service which is to be encrypted on the client machine, connecting to the 543203945Sweongyo same local port, and ssh will encrypt and forward the connection. 544203945Sweongyo 545203945Sweongyo The following example tunnels an IRC session from client machine 546203945Sweongyo ``127.0.0.1'' (localhost) to remote server ``server.example.com'': 547203945Sweongyo 548203945Sweongyo $ ssh -f -L 1234:localhost:6667 server.example.com sleep 10 549203945Sweongyo $ irc -c '#users' -p 1234 pinky 127.0.0.1 550203945Sweongyo 551203945Sweongyo This tunnels a connection to IRC server ``server.example.com'', joining 552203945Sweongyo channel ``#users'', nickname ``pinky'', using port 1234. It doesn't 553203945Sweongyo matter which port is used, as long as it's greater than 1023 (remember, 554203945Sweongyo only root can open sockets on privileged ports) and doesn't conflict with 555203945Sweongyo any ports already in use. The connection is forwarded to port 6667 on 556203945Sweongyo the remote server, since that's the standard port for IRC services. 557203945Sweongyo 558203945Sweongyo The -f option backgrounds ssh and the remote command ``sleep 10'' is 559203945Sweongyo specified to allow an amount of time (10 seconds, in the example) to 560203945Sweongyo start the service which is to be tunnelled. If no connections are made 561203945Sweongyo within the time specified, ssh will exit. 562203945Sweongyo 563203945SweongyoX11 FORWARDING 564203945Sweongyo If the ForwardX11 variable is set to ``yes'' (or see the description of 565203945Sweongyo the -X, -x, and -Y options above) and the user is using X11 (the DISPLAY 566203945Sweongyo environment variable is set), the connection to the X11 display is 567203945Sweongyo automatically forwarded to the remote side in such a way that any X11 568203945Sweongyo programs started from the shell (or command) will go through the 569203945Sweongyo encrypted channel, and the connection to the real X server will be made 570203945Sweongyo from the local machine. The user should not manually set DISPLAY. 571203945Sweongyo Forwarding of X11 connections can be configured on the command line or in 572203945Sweongyo configuration files. 573203945Sweongyo 574203945Sweongyo The DISPLAY value set by ssh will point to the server machine, but with a 575203945Sweongyo display number greater than zero. This is normal, and happens because 576203945Sweongyo ssh creates a ``proxy'' X server on the server machine for forwarding the 577203945Sweongyo connections over the encrypted channel. 578203945Sweongyo 579203945Sweongyo ssh will also automatically set up Xauthority data on the server machine. 580203945Sweongyo For this purpose, it will generate a random authorization cookie, store 581203945Sweongyo it in Xauthority on the server, and verify that any forwarded connections 582203945Sweongyo carry this cookie and replace it by the real cookie when the connection 583203945Sweongyo is opened. The real authentication cookie is never sent to the server 584203945Sweongyo machine (and no cookies are sent in the plain). 585203945Sweongyo 586203945Sweongyo If the ForwardAgent variable is set to ``yes'' (or see the description of 587203945Sweongyo the -A and -a options above) and the user is using an authentication 588203945Sweongyo agent, the connection to the agent is automatically forwarded to the 589203945Sweongyo remote side. 590203945Sweongyo 591203945SweongyoVERIFYING HOST KEYS 592203945Sweongyo When connecting to a server for the first time, a fingerprint of the 593203945Sweongyo server's public key is presented to the user (unless the option 594203945Sweongyo StrictHostKeyChecking has been disabled). Fingerprints can be determined 595203945Sweongyo using ssh-keygen(1): 596203945Sweongyo 597203945Sweongyo $ ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key 598203945Sweongyo 599203945Sweongyo If the fingerprint is already known, it can be matched and the key can be 600203945Sweongyo accepted or rejected. Because of the difficulty of comparing host keys 601203945Sweongyo just by looking at hex strings, there is also support to compare host 602203945Sweongyo keys visually, using random art. By setting the VisualHostKey option to 603203945Sweongyo ``yes'', a small ASCII graphic gets displayed on every login to a server, 604203945Sweongyo no matter if the session itself is interactive or not. By learning the 605203945Sweongyo pattern a known server produces, a user can easily find out that the host 606203945Sweongyo key has changed when a completely different pattern is displayed. 607203945Sweongyo Because these patterns are not unambiguous however, a pattern that looks 608203945Sweongyo similar to the pattern remembered only gives a good probability that the 609203945Sweongyo host key is the same, not guaranteed proof. 610203945Sweongyo 611203945Sweongyo To get a listing of the fingerprints along with their random art for all 612203945Sweongyo known hosts, the following command line can be used: 613203945Sweongyo 614203945Sweongyo $ ssh-keygen -lv -f ~/.ssh/known_hosts 615203945Sweongyo 616203945Sweongyo If the fingerprint is unknown, an alternative method of verification is 617203945Sweongyo available: SSH fingerprints verified by DNS. An additional resource 618203945Sweongyo record (RR), SSHFP, is added to a zonefile and the connecting client is 619203945Sweongyo able to match the fingerprint with that of the key presented. 620203945Sweongyo 621203945Sweongyo In this example, we are connecting a client to a server, 622203945Sweongyo ``host.example.com''. The SSHFP resource records should first be added 623203945Sweongyo to the zonefile for host.example.com: 624203945Sweongyo 625203945Sweongyo $ ssh-keygen -r host.example.com. 626203945Sweongyo 627203945Sweongyo The output lines will have to be added to the zonefile. To check that 628203945Sweongyo the zone is answering fingerprint queries: 629203945Sweongyo 630203945Sweongyo $ dig -t SSHFP host.example.com 631203945Sweongyo 632203945Sweongyo Finally the client connects: 633203945Sweongyo 634203945Sweongyo $ ssh -o "VerifyHostKeyDNS ask" host.example.com 635203945Sweongyo [...] 636203945Sweongyo Matching host key fingerprint found in DNS. 637203945Sweongyo Are you sure you want to continue connecting (yes/no)? 638203945Sweongyo 639203945Sweongyo See the VerifyHostKeyDNS option in ssh_config(5) for more information. 640203945Sweongyo 641203945SweongyoSSH-BASED VIRTUAL PRIVATE NETWORKS 642203945Sweongyo ssh contains support for Virtual Private Network (VPN) tunnelling using 643203945Sweongyo the tun(4) network pseudo-device, allowing two networks to be joined 644203945Sweongyo securely. The sshd_config(5) configuration option PermitTunnel controls 645203945Sweongyo whether the server supports this, and at what level (layer 2 or 3 646203945Sweongyo traffic). 647203945Sweongyo 648203945Sweongyo The following example would connect client network 10.0.50.0/24 with 649203945Sweongyo remote network 10.0.99.0/24 using a point-to-point connection from 650203945Sweongyo 10.1.1.1 to 10.1.1.2, provided that the SSH server running on the gateway 651203945Sweongyo to the remote network, at 192.168.1.15, allows it. 652203945Sweongyo 653203945Sweongyo On the client: 654203945Sweongyo 655203945Sweongyo # ssh -f -w 0:1 192.168.1.15 true 656203945Sweongyo # ifconfig tun0 10.1.1.1 10.1.1.2 netmask 255.255.255.252 657203945Sweongyo # route add 10.0.99.0/24 10.1.1.2 658203945Sweongyo 659203945Sweongyo On the server: 660203945Sweongyo 661203945Sweongyo # ifconfig tun1 10.1.1.2 10.1.1.1 netmask 255.255.255.252 662203945Sweongyo # route add 10.0.50.0/24 10.1.1.1 663203945Sweongyo 664203945Sweongyo Client access may be more finely tuned via the /root/.ssh/authorized_keys 665203945Sweongyo file (see below) and the PermitRootLogin server option. The following 666203945Sweongyo entry would permit connections on tun(4) device 1 from user ``jane'' and 667203945Sweongyo on tun device 2 from user ``john'', if PermitRootLogin is set to 668203945Sweongyo ``forced-commands-only'': 669203945Sweongyo 670203945Sweongyo tunnel="1",command="sh /etc/netstart tun1" ssh-rsa ... jane 671203945Sweongyo tunnel="2",command="sh /etc/netstart tun2" ssh-rsa ... john 672203945Sweongyo 673203945Sweongyo Since an SSH-based setup entails a fair amount of overhead, it may be 674203945Sweongyo more suited to temporary setups, such as for wireless VPNs. More 675203945Sweongyo permanent VPNs are better provided by tools such as ipsecctl(8) and 676203945Sweongyo isakmpd(8). 677203945Sweongyo 678203945SweongyoENVIRONMENT 679203945Sweongyo ssh will normally set the following environment variables: 680203945Sweongyo 681203945Sweongyo DISPLAY The DISPLAY variable indicates the location of the 682203945Sweongyo X11 server. It is automatically set by ssh to 683203945Sweongyo point to a value of the form ``hostname:n'', where 684203945Sweongyo ``hostname'' indicates the host where the shell 685203945Sweongyo runs, and `n' is an integer >= 1. ssh uses this 686203945Sweongyo special value to forward X11 connections over the 687203945Sweongyo secure channel. The user should normally not set 688203945Sweongyo DISPLAY explicitly, as that will render the X11 689203945Sweongyo connection insecure (and will require the user to 690203945Sweongyo manually copy any required authorization cookies). 691203945Sweongyo 692203945Sweongyo HOME Set to the path of the user's home directory. 693203945Sweongyo 694203945Sweongyo LOGNAME Synonym for USER; set for compatibility with 695203945Sweongyo systems that use this variable. 696203945Sweongyo 697203945Sweongyo MAIL Set to the path of the user's mailbox. 698203945Sweongyo 699203945Sweongyo PATH Set to the default PATH, as specified when 700203945Sweongyo compiling ssh. 701203945Sweongyo 702203945Sweongyo SSH_ASKPASS If ssh needs a passphrase, it will read the 703203945Sweongyo passphrase from the current terminal if it was run 704203945Sweongyo from a terminal. If ssh does not have a terminal 705203945Sweongyo associated with it but DISPLAY and SSH_ASKPASS are 706203945Sweongyo set, it will execute the program specified by 707203945Sweongyo SSH_ASKPASS and open an X11 window to read the 708203945Sweongyo passphrase. This is particularly useful when 709203945Sweongyo calling ssh from a .xsession or related script. 710203945Sweongyo (Note that on some machines it may be necessary to 711203945Sweongyo redirect the input from /dev/null to make this 712203945Sweongyo work.) 713203945Sweongyo 714203945Sweongyo SSH_AUTH_SOCK Identifies the path of a UNIX-domain socket used to 715203945Sweongyo communicate with the agent. 716203945Sweongyo 717203945Sweongyo SSH_CONNECTION Identifies the client and server ends of the 718203945Sweongyo connection. The variable contains four space- 719203945Sweongyo separated values: client IP address, client port 720203945Sweongyo number, server IP address, and server port number. 721203945Sweongyo 722203945Sweongyo SSH_ORIGINAL_COMMAND This variable contains the original command line if 723203945Sweongyo a forced command is executed. It can be used to 724203945Sweongyo extract the original arguments. 725203945Sweongyo 726203945Sweongyo SSH_TTY This is set to the name of the tty (path to the 727203945Sweongyo device) associated with the current shell or 728203945Sweongyo command. If the current session has no tty, this 729203945Sweongyo variable is not set. 730203945Sweongyo 731203945Sweongyo TZ This variable is set to indicate the present time 732203945Sweongyo zone if it was set when the daemon was started 733203945Sweongyo (i.e. the daemon passes the value on to new 734203945Sweongyo connections). 735203945Sweongyo 736203945Sweongyo USER Set to the name of the user logging in. 737203945Sweongyo 738203945Sweongyo Additionally, ssh reads ~/.ssh/environment, and adds lines of the format 739203945Sweongyo ``VARNAME=value'' to the environment if the file exists and users are 740203945Sweongyo allowed to change their environment. For more information, see the 741203945Sweongyo PermitUserEnvironment option in sshd_config(5). 742203945Sweongyo 743203945SweongyoFILES 744203945Sweongyo ~/.rhosts 745203945Sweongyo This file is used for host-based authentication (see above). On 746203945Sweongyo some machines this file may need to be world-readable if the 747203945Sweongyo user's home directory is on an NFS partition, because sshd(8) 748203945Sweongyo reads it as root. Additionally, this file must be owned by the 749203945Sweongyo user, and must not have write permissions for anyone else. The 750203945Sweongyo recommended permission for most machines is read/write for the 751203945Sweongyo user, and not accessible by others. 752203945Sweongyo 753203945Sweongyo ~/.shosts 754203945Sweongyo This file is used in exactly the same way as .rhosts, but allows 755203945Sweongyo host-based authentication without permitting login with 756203945Sweongyo rlogin/rsh. 757203945Sweongyo 758203945Sweongyo ~/.ssh/ 759203945Sweongyo This directory is the default location for all user-specific 760203945Sweongyo configuration and authentication information. There is no 761203945Sweongyo general requirement to keep the entire contents of this directory 762203945Sweongyo secret, but the recommended permissions are read/write/execute 763203945Sweongyo for the user, and not accessible by others. 764203945Sweongyo 765203945Sweongyo ~/.ssh/authorized_keys 766203945Sweongyo Lists the public keys (DSA/ECDSA/RSA) that can be used for 767203945Sweongyo logging in as this user. The format of this file is described in 768203945Sweongyo the sshd(8) manual page. This file is not highly sensitive, but 769203945Sweongyo the recommended permissions are read/write for the user, and not 770203945Sweongyo accessible by others. 771203945Sweongyo 772203945Sweongyo ~/.ssh/config 773203945Sweongyo This is the per-user configuration file. The file format and 774203945Sweongyo configuration options are described in ssh_config(5). Because of 775203945Sweongyo the potential for abuse, this file must have strict permissions: 776203945Sweongyo read/write for the user, and not accessible by others. 777203945Sweongyo 778203945Sweongyo ~/.ssh/environment 779203945Sweongyo Contains additional definitions for environment variables; see 780203945Sweongyo ENVIRONMENT, above. 781203945Sweongyo 782203945Sweongyo ~/.ssh/identity 783203945Sweongyo ~/.ssh/id_dsa 784203945Sweongyo ~/.ssh/id_ecdsa 785203945Sweongyo ~/.ssh/id_rsa 786203945Sweongyo Contains the private key for authentication. These files contain 787203945Sweongyo sensitive data and should be readable by the user but not 788203945Sweongyo accessible by others (read/write/execute). ssh will simply 789203945Sweongyo ignore a private key file if it is accessible by others. It is 790203945Sweongyo possible to specify a passphrase when generating the key which 791203945Sweongyo will be used to encrypt the sensitive part of this file using 792203945Sweongyo 3DES. 793203945Sweongyo 794203945Sweongyo ~/.ssh/identity.pub 795203945Sweongyo ~/.ssh/id_dsa.pub 796203945Sweongyo ~/.ssh/id_ecdsa.pub 797203945Sweongyo ~/.ssh/id_rsa.pub 798203945Sweongyo Contains the public key for authentication. These files are not 799203945Sweongyo sensitive and can (but need not) be readable by anyone. 800203945Sweongyo 801203945Sweongyo ~/.ssh/known_hosts 802203945Sweongyo Contains a list of host keys for all hosts the user has logged 803203945Sweongyo into that are not already in the systemwide list of known host 804203945Sweongyo keys. See sshd(8) for further details of the format of this 805203945Sweongyo file. 806203945Sweongyo 807203945Sweongyo ~/.ssh/rc 808203945Sweongyo Commands in this file are executed by ssh when the user logs in, 809203945Sweongyo just before the user's shell (or command) is started. See the 810203945Sweongyo sshd(8) manual page for more information. 811203945Sweongyo 812203945Sweongyo /etc/hosts.equiv 813203945Sweongyo This file is for host-based authentication (see above). It 814203945Sweongyo should only be writable by root. 815203945Sweongyo 816203945Sweongyo /etc/shosts.equiv 817203945Sweongyo This file is used in exactly the same way as hosts.equiv, but 818203945Sweongyo allows host-based authentication without permitting login with 819203945Sweongyo rlogin/rsh. 820203945Sweongyo 821203945Sweongyo /etc/ssh/ssh_config 822203945Sweongyo Systemwide configuration file. The file format and configuration 823203945Sweongyo options are described in ssh_config(5). 824203945Sweongyo 825203945Sweongyo /etc/ssh/ssh_host_key 826203945Sweongyo /etc/ssh/ssh_host_dsa_key 827203945Sweongyo /etc/ssh/ssh_host_ecdsa_key 828203945Sweongyo /etc/ssh/ssh_host_rsa_key 829203945Sweongyo These three files contain the private parts of the host keys and 830203945Sweongyo are used for host-based authentication. If protocol version 1 is 831203945Sweongyo used, ssh must be setuid root, since the host key is readable 832203945Sweongyo only by root. For protocol version 2, ssh uses ssh-keysign(8) to 833203945Sweongyo access the host keys, eliminating the requirement that ssh be 834203945Sweongyo setuid root when host-based authentication is used. By default 835203945Sweongyo ssh is not setuid root. 836203945Sweongyo 837203945Sweongyo /etc/ssh/ssh_known_hosts 838203945Sweongyo Systemwide list of known host keys. This file should be prepared 839203945Sweongyo by the system administrator to contain the public host keys of 840203945Sweongyo all machines in the organization. It should be world-readable. 841203945Sweongyo See sshd(8) for further details of the format of this file. 842203945Sweongyo 843203945Sweongyo /etc/ssh/sshrc 844203945Sweongyo Commands in this file are executed by ssh when the user logs in, 845203945Sweongyo just before the user's shell (or command) is started. See the 846203945Sweongyo sshd(8) manual page for more information. 847203945Sweongyo 848203945SweongyoEXIT STATUS 849203945Sweongyo ssh exits with the exit status of the remote command or with 255 if an 850203945Sweongyo error occurred. 851203945Sweongyo 852203945SweongyoSEE ALSO 853203945Sweongyo scp(1), sftp(1), ssh-add(1), ssh-agent(1), ssh-keygen(1), ssh-keyscan(1), 854203945Sweongyo tun(4), hosts.equiv(5), ssh_config(5), ssh-keysign(8), sshd(8) 855203945Sweongyo 856203945Sweongyo The Secure Shell (SSH) Protocol Assigned Numbers, RFC 4250, 2006. 857203945Sweongyo 858203945Sweongyo The Secure Shell (SSH) Protocol Architecture, RFC 4251, 2006. 859203945Sweongyo 860203945Sweongyo The Secure Shell (SSH) Authentication Protocol, RFC 4252, 2006. 861203945Sweongyo 862203945Sweongyo The Secure Shell (SSH) Transport Layer Protocol, RFC 4253, 2006. 863203945Sweongyo 864203945Sweongyo The Secure Shell (SSH) Connection Protocol, RFC 4254, 2006. 865203945Sweongyo 866203945Sweongyo Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints, RFC 867203945Sweongyo 4255, 2006. 868203945Sweongyo 869203945Sweongyo Generic Message Exchange Authentication for the Secure Shell Protocol 870203945Sweongyo (SSH), RFC 4256, 2006. 871203945Sweongyo 872203945Sweongyo The Secure Shell (SSH) Session Channel Break Extension, RFC 4335, 2006. 873203945Sweongyo 874203945Sweongyo The Secure Shell (SSH) Transport Layer Encryption Modes, RFC 4344, 2006. 875203945Sweongyo 876203945Sweongyo Improved Arcfour Modes for the Secure Shell (SSH) Transport Layer 877203945Sweongyo Protocol, RFC 4345, 2006. 878203945Sweongyo 879203945Sweongyo Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer 880203945Sweongyo Protocol, RFC 4419, 2006. 881203945Sweongyo 882203945Sweongyo The Secure Shell (SSH) Public Key File Format, RFC 4716, 2006. 883203945Sweongyo 884203945Sweongyo Elliptic Curve Algorithm Integration in the Secure Shell Transport Layer, 885203945Sweongyo RFC 5656, 2009. 886203945Sweongyo 887203945Sweongyo A. Perrig and D. Song, Hash Visualization: a New Technique to improve 888203945Sweongyo Real-World Security, 1999, International Workshop on Cryptographic 889203945Sweongyo Techniques and E-Commerce (CrypTEC '99). 890203945Sweongyo 891203945SweongyoAUTHORS 892203945Sweongyo OpenSSH is a derivative of the original and free ssh 1.2.12 release by 893203945Sweongyo Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo 894203945Sweongyo de Raadt and Dug Song removed many bugs, re-added newer features and 895203945Sweongyo created OpenSSH. Markus Friedl contributed the support for SSH protocol 896203945Sweongyo versions 1.5 and 2.0. 897203945Sweongyo 898203945SweongyoOpenBSD 4.9 November 18, 2010 OpenBSD 4.9 899203945Sweongyo