X-Git-Url: http://andersk.mit.edu/gitweb/gssapi-openssh.git/blobdiff_plain/30460aeb3d3c027b85eba1e4d45de75fb4b9d356..352b92931a9b3d49170acfe3e7758f6f6a27f1bb:/openssh/ssh.1 diff --git a/openssh/ssh.1 b/openssh/ssh.1 index 6e41bcd..6c6271e 100644 --- a/openssh/ssh.1 +++ b/openssh/ssh.1 @@ -34,8 +34,8 @@ .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" -.\" $OpenBSD: ssh.1,v 1.263 2006/07/11 18:50:48 markus Exp $ -.Dd September 25, 1999 +.\" $OpenBSD: ssh.1,v 1.283 2009/03/19 15:15:09 jmc Exp $ +.Dd $Mdocdate: March 19 2009 $ .Dt SSH 1 .Os .Sh NAME @@ -43,7 +43,7 @@ .Nd OpenSSH SSH client (remote login program) .Sh SYNOPSIS .Nm ssh -.Op Fl 1246AaCfgkMNnqsTtVvXxY +.Op Fl 1246AaCfgKkMNnqsTtVvXxYy .Op Fl b Ar bind_address .Op Fl c Ar cipher_spec .Oo Fl D\ \& @@ -191,26 +191,9 @@ For protocol version 2, .Ar cipher_spec is a comma-separated list of ciphers listed in order of preference. -The supported ciphers are: -3des-cbc, -aes128-cbc, -aes192-cbc, -aes256-cbc, -aes128-ctr, -aes192-ctr, -aes256-ctr, -arcfour128, -arcfour256, -arcfour, -blowfish-cbc, -and -cast128-cbc. -The default is: -.Bd -literal -offset indent -aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128, -arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr, -aes192-ctr,aes256-ctr -.Ed +See the +.Cm Ciphers +keyword for more information. .It Fl D Xo .Sm off .Oo Ar bind_address : Oc @@ -290,6 +273,15 @@ This implies The recommended way to start X11 programs at a remote site is with something like .Ic ssh -f host xterm . +.Pp +If the +.Cm ExitOnForwardFailure +configuration option is set to +.Dq yes , +then a client started with +.Fl f +will wait for all remote port forwards to be successfully established +before placing itself in the background. .It Fl g Allows remote hosts to connect to local forwarded ports. .It Fl I Ar smartcard_device @@ -315,6 +307,9 @@ It is possible to have multiple .Fl i options (and multiple identities specified in configuration files). +.It Fl K +Enables GSSAPI-based authentication and forwarding (delegation) of GSSAPI +credentials to the server. .It Fl k Disables forwarding (delegation) of GSSAPI credentials to the server. .It Fl L Xo @@ -495,6 +490,7 @@ For full details of the options listed below, and their possible values, see .It User .It UserKnownHostsFile .It VerifyHostKeyDNS +.It VisualHostKey .It XAuthLocation .El .It Fl p Ar port @@ -503,7 +499,7 @@ This can be specified on a per-host basis in the configuration file. .It Fl q Quiet mode. -Causes all warning and diagnostic messages to be suppressed. +Causes most warning and diagnostic messages to be suppressed. .It Fl R Xo .Sm off .Oo Ar bind_address : Oc @@ -537,7 +533,7 @@ using an alternative syntax: .Pp By default, the listening socket on the server will be bound to the loopback interface only. -This may be overriden by specifying a +This may be overridden by specifying a .Ar bind_address . An empty .Ar bind_address , @@ -550,6 +546,13 @@ will only succeed if the server's .Cm GatewayPorts option is enabled (see .Xr sshd_config 5 ) . +.Pp +If the +.Ar port +argument is +.Ql 0 , +the listen port will be dynamically allocated on the server and reported +to the client at run time. .It Fl S Ar ctl_path Specifies the location of a control socket for connection sharing. Refer to the description of @@ -645,6 +648,11 @@ Disables X11 forwarding. Enables trusted X11 forwarding. Trusted X11 forwardings are not subjected to the X11 SECURITY extension controls. +.It Fl y +Send log information using the +.Xr syslog 3 +system module. +By default this information is sent to stderr. .El .Pp .Nm @@ -674,7 +682,7 @@ Both protocols support similar authentication methods, but protocol 2 is preferred since it provides additional mechanisms for confidentiality (the traffic is encrypted using AES, 3DES, Blowfish, CAST128, or Arcfour) -and integrity (hmac-md5, hmac-sha1, hmac-ripemd160). +and integrity (hmac-md5, hmac-sha1, umac-64, hmac-ripemd160). Protocol 1 lacks a strong mechanism for ensuring the integrity of the connection. .Pp @@ -880,9 +888,10 @@ Send a BREAK to the remote system .It Cm ~C Open command line. Currently this allows the addition of port forwardings using the -.Fl L -and +.Fl L , .Fl R +and +.Fl D options (see above). It also allows the cancellation of existing remote port-forwardings using @@ -1024,9 +1033,31 @@ Fingerprints can be determined using .Pp .Dl $ ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key .Pp -If the fingerprint is already known, -it can be matched and verified, -and the key can be accepted. +If the fingerprint is already known, it can be matched +and the key can be accepted or rejected. +Because of the difficulty of comparing host keys +just by looking at hex strings, +there is also support to compare host keys visually, +using +.Em random art . +By setting the +.Cm VisualHostKey +option to +.Dq yes , +a small ASCII graphic gets displayed on every login to a server, no matter +if the session itself is interactive or not. +By learning the pattern a known server produces, a user can easily +find out that the host key has changed when a completely different pattern +is displayed. +Because these patterns are not unambiguous however, a pattern that looks +similar to the pattern remembered only gives a good probability that the +host key is the same, not guaranteed proof. +.Pp +To get a listing of the fingerprints along with their random art for +all known hosts, the following command line can be used: +.Pp +.Dl $ ssh-keygen -lv -f ~/.ssh/known_hosts +.Pp If the fingerprint is unknown, an alternative method of verification is available: SSH fingerprints verified by DNS. @@ -1077,12 +1108,22 @@ controls whether the server supports this, and at what level (layer 2 or 3 traffic). .Pp The following example would connect client network 10.0.50.0/24 -with remote network 10.0.99.0/24, provided that the SSH server -running on the gateway to the remote network, -at 192.168.1.15, allows it: +with remote network 10.0.99.0/24 using a point-to-point connection +from 10.1.1.1 to 10.1.1.2, +provided that the SSH server running on the gateway to the remote network, +at 192.168.1.15, allows it. +.Pp +On the client: .Bd -literal -offset indent # ssh -f -w 0:1 192.168.1.15 true -# ifconfig tun0 10.0.50.1 10.0.99.1 netmask 255.255.255.252 +# ifconfig tun0 10.1.1.1 10.1.1.2 netmask 255.255.255.252 +# route add 10.0.99.0/24 10.1.1.2 +.Ed +.Pp +On the server: +.Bd -literal -offset indent +# ifconfig tun1 10.1.1.2 10.1.1.1 netmask 255.255.255.252 +# route add 10.0.50.0/24 10.1.1.1 .Ed .Pp Client access may be more finely tuned via the @@ -1105,7 +1146,7 @@ tunnel="1",command="sh /etc/netstart tun1" ssh-rsa ... jane tunnel="2",command="sh /etc/netstart tun2" ssh-rsa ... john .Ed .Pp -Since a SSH-based setup entails a fair amount of overhead, +Since an SSH-based setup entails a fair amount of overhead, it may be more suited to temporary setups, such as for wireless VPNs. More permanent VPNs are better provided by tools such as @@ -1232,6 +1273,13 @@ This file is used in exactly the same way as but allows host-based authentication without permitting login with rlogin/rsh. .Pp +.It ~/.ssh/ +This directory is the default location for all user-specific configuration +and authentication information. +There is no general requirement to keep the entire contents of this directory +secret, but the recommended permissions are read/write/execute for the user, +and not accessible by others. +.Pp .It ~/.ssh/authorized_keys Lists the public keys (RSA/DSA) that can be used for logging in as this user. The format of this file is described in the @@ -1408,6 +1456,18 @@ manual page for more information. .%T "Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol" .%D 2006 .Re +.Rs +.%R RFC 4716 +.%T "The Secure Shell (SSH) Public Key File Format" +.%D 2006 +.Re +.Rs +.%T "Hash Visualization: a New Technique to improve Real-World Security" +.%A A. Perrig +.%A D. Song +.%D 1999 +.%O "International Workshop on Cryptographic Techniques and E-Commerce (CrypTEC '99)" +.Re .Sh AUTHORS OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen.