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-rw-r--r--scp.1110
-rw-r--r--ssh-add.1116
-rw-r--r--ssh-agent.1163
-rw-r--r--ssh-keygen.1155
-rw-r--r--ssh.1966
-rw-r--r--sshd.8781
6 files changed, 2291 insertions, 0 deletions
diff --git a/scp.1 b/scp.1
new file mode 100644
index 00000000..5eedfdb9
--- /dev/null
+++ b/scp.1
@@ -0,0 +1,110 @@
+.\" -*- nroff -*-
+.\"
+.\" scp.1
+.\"
+.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
+.\"
+.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+.\" All rights reserved
+.\"
+.\" Created: Sun May 7 00:14:37 1995 ylo
+.\"
+.\" $Id: scp.1,v 1.3 1999/10/28 23:15:49 damien Exp $
+.\"
+.Dd September 25, 1999
+.Dt SCP 1
+.Os
+.Sh NAME
+.Nm scp
+.Nd secure copy (remote file copy program)
+.Sh SYNOPSIS
+.Nm scp
+.Op Fl pqrvC
+.Op Fl P Ar port
+.Op Fl c Ar cipher
+.Op Fl i Ar identity_file
+.Sm off
+.Oo
+.Op Ar user@
+.Ar host1 No :
+.Oc Ns Ar file1
+.Sm on
+.Op Ar ...
+.Sm off
+.Oo
+.Op Ar user@
+.Ar host2 No :
+.Oc Ar file2
+.Sm on
+.Sh DESCRIPTION
+.Nm
+copies files between hosts on a network. It uses
+.Xr ssh 1
+for data transfer, and uses the same authentication and provides the
+same security as
+.Xr ssh 1 .
+Unlike
+.Xr rcp 1 ,
+.Nm
+will ask for passwords or passphrases if they are needed for
+authentication.
+.Pp
+Any file name may contain a host and user specification to indicate
+that the file is to be copied to/from that host. Copies between two
+remote hosts are permitted.
+.Pp
+The options are as follows:
+.Bl -tag -width Ds
+.It Fl c Ar cipher
+Selects the cipher to use for encrypting the data transfer. This
+option is directly passed to
+.Xr ssh 1 .
+.It Fl i Ar identity_file
+Selects the file from which the identity (private key) for RSA
+authentication is read. This option is directly passed to
+.Xr ssh 1 .
+.It Fl p
+Preserves modification times, access times, and modes from the
+original file.
+.It Fl r
+Recursively copy entire directories.
+.It Fl v
+Verbose mode. Causes
+.Nm
+and
+.Xr ssh 1
+to print debugging messages about their progress. This is helpful in
+debugging connection, authentication, and configuration problems.
+.It Fl B
+Selects batch mode (prevents asking for passwords or passphrases).
+.It Fl q
+Disables the progress meter.
+.It Fl C
+Compression enable. Passes the
+.Fl C
+flag to
+.Xr ssh 1
+to enable compression.
+.It Fl P Ar port
+Specifies the port to connect to on the remote host. Note that this
+option is written with a capital
+.Sq P ,
+because
+.Fl p
+is already reserved for preserving the times and modes of the file in
+.Xr rcp 1 .
+.Sh AUTHORS
+Timo Rinne <tri@iki.fi> and Tatu Ylonen <ylo@cs.hut.fi>
+.Sh HISTORY
+.Nm
+is based on the
+.Xr rcp 1
+program in BSD source code from the Regents of the University of
+California.
+.Sh SEE ALSO
+.Xr rcp 1 ,
+.Xr ssh 1 ,
+.Xr ssh-add 1 ,
+.Xr ssh-agent 1 ,
+.Xr ssh-keygen 1 ,
+.Xr sshd 8
diff --git a/ssh-add.1 b/ssh-add.1
new file mode 100644
index 00000000..0ab93dc6
--- /dev/null
+++ b/ssh-add.1
@@ -0,0 +1,116 @@
+.\" -*- nroff -*-
+.\"
+.\" ssh-add.1
+.\"
+.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
+.\"
+.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+.\" All rights reserved
+.\"
+.\" Created: Sat Apr 22 23:55:14 1995 ylo
+.\"
+.\" $Id: ssh-add.1,v 1.3 1999/10/28 23:15:49 damien Exp $
+.\"
+.Dd September 25, 1999
+.Dt SSH-ADD 1
+.Os
+.Sh NAME
+.Nm ssh-add
+.Nd adds identities for the authentication agent
+.Sh SYNOPSIS
+.Nm ssh-add
+.Op Fl ldD
+.Op Ar
+.Sh DESCRIPTION
+.Nm
+adds identities to the authentication agent,
+.Xr ssh-agent 1 .
+When run without arguments, it adds the file
+.Pa $HOME/.ssh/identity .
+Alternative file names can be given on the
+command line. If any file requires a passphrase,
+.Nm
+asks for the passphrase from the user.
+The Passphrase it is read from the user's tty.
+.Pp
+The authentication agent must be running and must be an ancestor of
+the current process for
+.Nm
+to work.
+.Pp
+The options are as follows:
+.Bl -tag -width Ds
+.It Fl l
+Lists all identities currently represented by the agent.
+.It Fl d
+Instead of adding the identity, removes the identity from the agent.
+.It Fl D
+Deletes all identities from the agent.
+.El
+.Sh FILES
+.Bl -tag -width Ds
+.Pa $HOME/.ssh/identity
+Contains the RSA authentication identity of the user. This file
+should not be readable by anyone but the user.
+Note that
+.Nm
+ignores this file if it is accessible by others.
+It is possible to
+specify a passphrase when generating the key; that passphrase will be
+used to encrypt the private part of this file. This is the
+default file added by
+.Nm
+when no other files have been specified.
+.Pp
+If
+.Nm
+needs a passphrase, it will read the passphrase from the current
+terminal if it was run from a terminal. If
+.Nm
+does not have a terminal associated with it but
+.Ev DISPLAY
+is set, it
+will open an X11 window to read the passphrase. This is particularly
+useful when calling
+.Nm
+from a
+.Pa .Xsession
+or related script. (Note that on some machines it
+may be necessary to redirect the input from
+.Pa /dev/null
+to make this work.)
+.Sh AUTHOR
+Tatu Ylonen <ylo@cs.hut.fi>
+.Pp
+OpenSSH
+is a derivative of the original (free) ssh 1.2.12 release, but with bugs
+removed and newer features re-added. Rapidly after the 1.2.12 release,
+newer versions bore successively more restrictive licenses. This version
+of OpenSSH
+.Bl -bullet
+.It
+has all components of a restrictive nature (ie. patents, see
+.Xr ssl 8 )
+directly removed from the source code; any licensed or patented components
+are chosen from
+external libraries.
+.It
+has been updated to support ssh protocol 1.5.
+.It
+contains added support for
+.Xr kerberos 8
+authentication and ticket passing.
+.It
+supports one-time password authentication with
+.Xr skey 1 .
+.El
+.Pp
+The libraries described in
+.Xr ssl 8
+are required for proper operation.
+.Sh SEE ALSO
+.Xr ssh 1 ,
+.Xr ssh-agent 1 ,
+.Xr ssh-keygen 1 ,
+.Xr sshd 8 ,
+.Xr ssl 8
diff --git a/ssh-agent.1 b/ssh-agent.1
new file mode 100644
index 00000000..8b9504fa
--- /dev/null
+++ b/ssh-agent.1
@@ -0,0 +1,163 @@
+.\" $OpenBSD: ssh-agent.1,v 1.7 1999/10/28 08:43:10 markus Exp $
+.\"
+.\" -*- nroff -*-
+.\"
+.\" ssh-agent.1
+.\"
+.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
+pp.\"
+.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+.\" All rights reserved
+.\"
+.\" Created: Sat Apr 23 20:10:43 1995 ylo
+.\"
+.Dd September 25, 1999
+.Dt SSH-AGENT 1
+.Os
+.Sh NAME
+.Nm ssh-agent
+.Nd authentication agent
+.Sh SYNOPSIS
+.Nm ssh-agent
+.Op Fl c Li | Fl s
+.Op Fl k
+.Oo
+.Ar command
+.Op Ar args ...
+.Oc
+.Sh DESCRIPTION
+.Nm
+is a program to hold authentication private keys. The
+idea is that
+.Nm
+is started in the beginning of an X-session or a login session, and
+all other windows or programs are started as clients to the ssh-agent
+program. Through use of environment variables the agent can be located
+and automatically used for RSA authentication when logging in to other
+machines using
+.Xr ssh 1 .
+.Pp
+The options are as follows:
+.Bl -tag -width Ds
+.It Fl c
+Generate C-shell commands on
+.Dv stdout .
+This is the default if
+.Ev SHELL
+looks like it's a csh style of shell.
+.It Fl s
+Generate Bourne shell commands on
+.Dv stdout .
+This is the default if
+.Ev SHELL
+does not look like it's a csh style of shell.
+.It Fl k
+Kill the current agent (given by the
+.Ev SSH_AGENT_PID
+environment variable).
+.El
+.Pp
+If a commandline is given, this is executed as a subprocess of the agent.
+When the command dies, so does the agent.
+.Pp
+The agent initially does not have any private keys. Keys are added
+using
+.Xr ssh-add 1 .
+When executed without arguments,
+.Xr ssh-add 1
+adds the
+.Pa $HOME/.ssh/identity
+file. If the identity has a passphrase,
+.Xr ssh-add 1
+asks for the passphrase (using a small X11 application if running
+under X11, or from the terminal if running without X). It then sends
+the identity to the agent. Several identities can be stored in the
+agent; the agent can automatically use any of these identities.
+.Ic ssh-add -l
+displays the identities currently held by the agent.
+.Pp
+The idea is that the agent is run in the user's local PC, laptop, or
+terminal. Authentication data need not be stored on any other
+machine, and authentication passphrases never go over the network.
+However, the connection to the agent is forwarded over SSH
+remote logins, and the user can thus use the privileges given by the
+identities anywhere in the network in a secure way.
+.Pp
+There are two main ways to get an agent setup: Either you let the agent
+start a new subcommand into which some environment variables are exported, or
+you let the agent print the needed shell commands (either
+.Xr sh 1
+or
+.Xr csh 1
+syntax can be generated) which can be evalled in the calling shell.
+Later
+.Xr ssh 1
+look at these variables and use them to establish a connection to the agent.
+.Pp
+A unix-domain socket is created
+.Pq Pa /tmp/ssh-XXXXXXXX/agent.<pid> ,
+and the name of this socket is stored in the
+.Ev SSH_AUTH_SOCK
+environment
+variable. The socket is made accessible only to the current user.
+This method is easily abused by root or another instance of the same
+user.
+.Pp
+The
+.Ev SSH_AGENT_PID
+environment variable holds the agent's PID.
+.Pp
+The agent exits automatically when the command given on the command
+line terminates.
+.Sh FILES
+.Bl -tag -width Ds
+.It Pa $HOME/.ssh/identity
+Contains the RSA authentication identity of the user. This file
+should not be readable by anyone but the user. It is possible to
+specify a passphrase when generating the key; that passphrase will be
+used to encrypt the private part of this file. This file
+is not used by
+.Nm
+but is normally added to the agent using
+.Xr ssh-add 1
+at login time.
+.It Pa /tmp/ssh-XXXX/agent.<pid> ,
+Unix-domain sockets used to contain the connection to the
+authentication agent. These sockets should only be readable by the
+owner. The sockets should get automatically removed when the agent
+exits.
+.Sh AUTHOR
+Tatu Ylonen <ylo@cs.hut.fi>
+.Pp
+OpenSSH
+is a derivative of the original (free) ssh 1.2.12 release, but with bugs
+removed and newer features re-added. Rapidly after the 1.2.12 release,
+newer versions bore successively more restrictive licenses. This version
+of OpenSSH
+.Bl -bullet
+.It
+has all components of a restrictive nature (ie. patents, see
+.Xr ssl 8 )
+directly removed from the source code; any licensed or patented components
+are chosen from
+external libraries.
+.It
+has been updated to support ssh protocol 1.5.
+.It
+contains added support for
+.Xr kerberos 8
+authentication and ticket passing.
+.It
+supports one-time password authentication with
+.Xr skey 1 .
+.El
+.Pp
+The libraries described in
+.Xr ssl 8
+are required for proper operation.
+.Sh SEE ALSO
+.Xr ssh 1 ,
+.Xr ssh-add 1 ,
+.Xr ssh-keygen 1 ,
+.Xr sshd 8 ,
+.Xr ssl 8
diff --git a/ssh-keygen.1 b/ssh-keygen.1
new file mode 100644
index 00000000..2cbcfae1
--- /dev/null
+++ b/ssh-keygen.1
@@ -0,0 +1,155 @@
+.\" -*- nroff -*-
+.\"
+.\" ssh-keygen.1
+.\"
+.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
+.\"
+.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+.\" All rights reserved
+.\"
+.\" Created: Sat Apr 22 23:55:14 1995 ylo
+.\"
+.\" $Id: ssh-keygen.1,v 1.3 1999/10/28 23:15:49 damien Exp $
+.\"
+.Dd September 25, 1999
+.Dt SSH-KEYGEN 1
+.Os
+.Sh NAME
+.Nm ssh-keygen
+.Nd authentication key generation
+.Sh SYNOPSIS
+.Nm ssh-keygen
+.Op Fl q
+.Op Fl b Ar bits
+.Op Fl N Ar new_passphrase
+.Op Fl C Ar comment
+.Nm ssh-keygen
+.Fl p
+.Op Fl P Ar old_passphrase
+.Op Fl N Ar new_passphrase
+.Nm ssh-keygen
+.Fl c
+.Op Fl P Ar passphrase
+.Op Fl C Ar comment
+.Sh DESCRIPTION
+.Nm
+generates and manages authentication keys for
+.Xr ssh 1 .
+Normally each user wishing to use SSH
+with RSA authentication runs this once to create the authentication
+key in
+.Pa $HOME/.ssh/identity .
+Additionally, the system administrator may use this to generate host keys.
+.Pp
+Normally this program generates the key and asks for a file in which
+to store the private key. The public key is stored in a file with the
+same name but
+.Dq .pub
+appended. The program also asks for a
+passphrase. The passphrase may be empty to indicate no passphrase
+(host keys must have empty passphrase), or it may be a string of
+arbitrary length. Good passphrases are 10-30 characters long and are
+not simple sentences or otherwise easily guessable (English
+prose has only 1-2 bits of entropy per word, and provides very bad
+passphrases). The passphrase can be changed later by using the
+.Fl p
+option.
+.Pp
+There is no way to recover a lost passphrase. If the passphrase is
+lost or forgotten, you will have to generate a new key and copy the
+corresponding public key to other machines.
+.Pp
+There is also a comment field in the key file that is only for
+convenience to the user to help identify the key. The comment can
+tell what the key is for, or whatever is useful. The comment is
+initialized to
+.Dq user@host
+when the key is created, but can be changed using the
+.Fl c
+option.
+.Pp
+The options are as follows:
+.Bl -tag -width Ds
+.It Fl b Ar bits
+Specifies the number of bits in the key to create. Minimum is 512
+bits. Generally 1024 bits is considered sufficient, and key sizes
+above that no longer improve security but make things slower. The
+default is 1024 bits.
+.It Fl c
+Requests changing the comment in the private and public key files.
+The program will prompt for the file containing the private keys, for
+passphrase if the key has one, and for the new comment.
+.It Fl p
+Requests changing the passphrase of a private key file instead of
+creating a new private key. The program will prompt for the file
+containing the private key, for the old passphrase, and twice for the
+new passphrase.
+.It Fl q
+Silence
+.Nm ssh-keygen .
+Used by
+.Pa /etc/rc
+when creating a new key.
+.It Fl C Ar comment
+Provides the new comment.
+.It Fl N Ar new_passphrase
+Provides the new passphrase.
+.It Fl P Ar passphrase
+Provides the (old) passphrase.
+.El
+.Sh FILES
+.Bl -tag -width Ds
+.It Pa $HOME/.ssh/random_seed
+Used for seeding the random number generator. This file should not be
+readable by anyone but the user. This file is created the first time
+the program is run, and is updated every time.
+.It Pa $HOME/.ssh/identity
+Contains the RSA authentication identity of the user. This file
+should not be readable by anyone but the user. It is possible to
+specify a passphrase when generating the key; that passphrase will be
+used to encrypt the private part of this file using 3DES. This file
+is not automatically accessed by
+.Nm
+but it is offered as the default file for the private key.
+.It Pa $HOME/.ssh/identity.pub
+Contains the public key for authentication. The contents of this file
+should be added to
+.Pa $HOME/.ssh/authorized_keys
+on all machines
+where you wish to log in using RSA authentication. There is no
+need to keep the contents of this file secret.
+.Sh AUTHOR
+Tatu Ylonen <ylo@cs.hut.fi>
+.Pp
+OpenSSH
+is a derivative of the original (free) ssh 1.2.12 release, but with bugs
+removed and newer features re-added. Rapidly after the 1.2.12 release,
+newer versions bore successively more restrictive licenses. This version
+of OpenSSH
+.Bl -bullet
+.It
+has all components of a restrictive nature (ie. patents, see
+.Xr ssl 8 )
+directly removed from the source code; any licensed or patented components
+are chosen from
+external libraries.
+.It
+has been updated to support ssh protocol 1.5.
+.It
+contains added support for
+.Xr kerberos 8
+authentication and ticket passing.
+.It
+supports one-time password authentication with
+.Xr skey 1 .
+.El
+.Pp
+The libraries described in
+.Xr ssl 8
+are required for proper operation.
+.Sh SEE ALSO
+.Xr ssh 1 ,
+.Xr ssh-add 1 ,
+.Xr ssh-agent 1,
+.Xr sshd 8 ,
+.Xr ssl 8
diff --git a/ssh.1 b/ssh.1
new file mode 100644
index 00000000..36703e20
--- /dev/null
+++ b/ssh.1
@@ -0,0 +1,966 @@
+.\" -*- nroff -*-
+.\"
+.\" ssh.1.in
+.\"
+.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
+.\"
+.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+.\" All rights reserved
+.\"
+.\" Created: Sat Apr 22 21:55:14 1995 ylo
+.\"
+.\" $Id: ssh.1,v 1.3 1999/10/28 23:15:50 damien Exp $
+.\"
+.Dd September 25, 1999
+.Dt SSH 1
+.Os
+.Sh NAME
+.Nm ssh
+.Nd OpenSSH secure shell client (remote login program)
+.Sh SYNOPSIS
+.Nm ssh
+.Op Fl l Ar login_name
+.Op Ar hostname | user@hostname
+.Op Ar command
+.Pp
+.Nm ssh
+.Op Fl afgknqtvxCPX
+.Op Fl c Ar blowfish | 3des
+.Op Fl e Ar escape_char
+.Op Fl i Ar identity_file
+.Op Fl l Ar login_name
+.Op Fl o Ar option
+.Op Fl p Ar port
+.Oo Fl L Xo
+.Sm off
+.Ar host :
+.Ar port :
+.Ar hostport
+.Sm on
+.Xc
+.Oc
+.Oo Fl R Xo
+.Sm off
+.Ar host :
+.Ar port :
+.Ar hostport
+.Sm on
+.Xc
+.Oc
+.Op Ar hostname | user@hostname
+.Op Ar command
+.Sh DESCRIPTION
+.Nm
+(Secure Shell) is a program for logging into a remote machine and for
+executing commands on a remote machine. It is intended to replace
+rlogin and rsh, and provide secure encrypted communications between
+two untrusted hosts over an insecure network. X11 connections and
+arbitrary TCP/IP ports can also be forwarded over the secure channel.
+.Pp
+.Nm
+connects and logs into the specified
+.Ar hostname .
+The user must prove
+his/her identity to the remote machine using one of several methods.
+.Pp
+First, if the machine the user logs in from is listed in
+.Pa /etc/hosts.equiv
+or
+.Pa /etc/shosts.equiv
+on the remote machine, and the user names are
+the same on both sides, the user is immediately permitted to log in.
+Second, if
+.Pa \&.rhosts
+or
+.Pa \&.shosts
+exists in the user's home directory on the
+remote machine and contains a line containing the name of the client
+machine and the name of the user on that machine, the user is
+permitted to log in. This form of authentication alone is normally not
+allowed by the server because it is not secure.
+.Pp
+The second (and primary) authentication method is the
+.Pa rhosts
+or
+.Pa hosts.equiv
+method combined with RSA-based host authentication. It
+means that if the login would be permitted by
+.Pa \&.rhosts ,
+.Pa \&.shosts ,
+.Pa /etc/hosts.equiv ,
+or
+.Pa /etc/shosts.equiv ,
+and if additionally the server can verify the client's
+host key (see
+.Pa /etc/ssh_known_hosts
+in the
+.Sx FILES
+section), only then login is
+permitted. This authentication method closes security holes due to IP
+spoofing, DNS spoofing and routing spoofing. [Note to the
+administrator:
+.Pa /etc/hosts.equiv ,
+.Pa \&.rhosts ,
+and the rlogin/rsh protocol in general, are inherently insecure and should be
+disabled if security is desired.]
+.Pp
+As a third authentication method,
+.Nm
+supports RSA based authentication.
+The scheme is based on public-key cryptography: there are cryptosystems
+where encryption and decryption are done using separate keys, and it
+is not possible to derive the decryption key from the encryption key.
+RSA is one such system. The idea is that each user creates a public/private
+key pair for authentication purposes. The
+server knows the public key, and only the user knows the private key.
+The file
+.Pa $HOME/.ssh/authorized_keys
+lists the public keys that are permitted for logging
+in. When the user logs in, the
+.Nm
+program tells the server which key pair it would like to use for
+authentication. The server checks if this key is permitted, and if
+so, sends the user (actually the
+.Nm
+program running on behalf of the user) a challenge, a random number,
+encrypted by the user's public key. The challenge can only be
+decrypted using the proper private key. The user's client then decrypts the
+challenge using the private key, proving that he/she knows the private
+key but without disclosing it to the server.
+.Pp
+.Nm
+implements the RSA authentication protocol automatically. The user
+creates his/her RSA key pair by running
+.Xr ssh-keygen 1 .
+This stores the private key in
+.Pa \&.ssh/identity
+and the public key in
+.Pa \&.ssh/identity.pub
+in the user's home directory. The user should then
+copy the
+.Pa identity.pub
+to
+.Pa \&.ssh/authorized_keys
+in his/her home directory on the remote machine (the
+.Pa authorized_keys
+file corresponds to the conventional
+.Pa \&.rhosts
+file, and has one key
+per line, though the lines can be very long). After this, the user
+can log in without giving the password. RSA authentication is much
+more secure than rhosts authentication.
+.Pp
+The most convenient way to use RSA authentication may be with an
+authentication agent. See
+.Xr ssh-agent 1
+for more information.
+.Pp
+If other authentication methods fail,
+.Nm
+prompts the user for a password. The password is sent to the remote
+host for checking; however, since all communications are encrypted,
+the password cannot be seen by someone listening on the network.
+.Pp
+When the user's identity has been accepted by the server, the server
+either executes the given command, or logs into the machine and gives
+the user a normal shell on the remote machine. All communication with
+the remote command or shell will be automatically encrypted.
+.Pp
+If a pseudo-terminal has been allocated (normal login session), the
+user can disconnect with
+.Ic ~. ,
+and suspend
+.Nm
+with
+.Ic ~^Z .
+All forwarded connections can be listed with
+.Ic ~#
+and if
+the session blocks waiting for forwarded X11 or TCP/IP
+connections to terminate, it can be backgrounded with
+.Ic ~&
+(this should not be used while the user shell is active, as it can cause the
+shell to hang). All available escapes can be listed with
+.Ic ~? .
+.Pp
+A single tilde character can be sent as
+.Ic ~~
+(or by following the tilde by a character other than those described above).
+The escape character must always follow a newline to be interpreted as
+special. The escape character can be changed in configuration files
+or on the command line.
+.Pp
+If no pseudo tty has been allocated, the
+session is transparent and can be used to reliably transfer binary
+data. On most systems, setting the escape character to
+.Dq none
+will also make the session transparent even if a tty is used.
+.Pp
+The session terminates when the command or shell in on the remote
+machine exists and all X11 and TCP/IP connections have been closed.
+The exit status of the remote program is returned as the exit status
+of
+.Nm ssh .
+.Pp
+If the user is using X11 (the
+.Ev DISPLAY
+environment variable is set), the connection to the X11 display is
+automatically forwarded to the remote side in such a way that any X11
+programs started from the shell (or command) will go through the
+encrypted channel, and the connection to the real X server will be made
+from the local machine. The user should not manually set
+.Ev DISPLAY .
+Forwarding of X11 connections can be
+configured on the command line or in configuration files.
+.Pp
+The
+.Ev DISPLAY
+value set by
+.Nm
+will point to the server machine, but with a display number greater
+than zero. This is normal, and happens because
+.Nm
+creates a
+.Dq proxy
+X server on the server machine for forwarding the
+connections over the encrypted channel.
+.Pp
+.Nm
+will also automatically set up Xauthority data on the server machine.
+For this purpose, it will generate a random authorization cookie,
+store it in Xauthority on the server, and verify that any forwarded
+connections carry this cookie and replace it by the real cookie when
+the connection is opened. The real authentication cookie is never
+sent to the server machine (and no cookies are sent in the plain).
+.Pp
+If the user is using an authentication agent, the connection to the agent
+is automatically forwarded to the remote side unless disabled on
+command line or in a configuration file.
+.Pp
+Forwarding of arbitrary TCP/IP connections over the secure channel can
+be specified either on command line or in a configuration file. One
+possible application of TCP/IP forwarding is a secure connection to an
+electronic purse; another is going trough firewalls.
+.Pp
+.Nm
+automatically maintains and checks a database containing RSA-based
+identifications for all hosts it has ever been used with. The
+database is stored in
+.Pa \&.ssh/known_hosts
+in the user's home directory. Additionally, the file
+.Pa /etc/ssh_known_hosts
+is automatically checked for known hosts. Any new hosts are
+automatically added to the user's file. If a host's identification
+ever changes,
+.Nm
+warns about this and disables password authentication to prevent a
+trojan horse from getting the user's password. Another purpose of
+this mechanism is to prevent man-in-the-middle attacks which could
+otherwise be used to circumvent the encryption. The
+.Cm StrictHostKeyChecking
+option (see below) can be used to prevent logins to machines whose
+host key is not known or has changed.
+.Sh OPTIONS
+.Bl -tag -width Ds
+.It Fl a
+Disables forwarding of the authentication agent connection. This may
+also be specified on a per-host basis in the configuration file.
+.It Fl c Ar blowfish|3des
+Selects the cipher to use for encrypting the session.
+.Ar 3des
+is used by default. It is believed to be secure.
+.Ar 3des
+(triple-des) is an encrypt-decrypt-encrypt triple with three different keys.
+It is presumably more secure than the
+.Ar des
+cipher which is no longer supported in ssh.
+.Ar blowfish
+is a fast block cipher, it appears very secure and is much faster than
+.Ar 3des .
+.It Fl e Ar ch|^ch|none
+Sets the escape character for sessions with a pty (default:
+.Ql ~ ) .
+The escape character is only recognized at the beginning of a line. The
+escape character followed by a dot
+.Pq Ql \&.
+closes the connection, followed
+by control-Z suspends the connection, and followed by itself sends the
+escape character once. Setting the character to
+.Dq none
+disables any escapes and makes the session fully transparent.
+.It Fl f
+Requests
+.Nm
+to go to background after authentication. This is useful
+if
+.Nm
+is going to ask for passwords or passphrases, but the user
+wants it in the background. This implies
+.Fl n .
+The recommended way to start X11 programs at a remote site is with
+something like
+.Ic ssh -f host xterm .
+.It Fl i Ar identity_file
+Selects the file from which the identity (private key) for
+RSA authentication is read. Default is
+.Pa \&.ssh/identity
+in the user's home directory. Identity files may also be specified on
+a per-host basis in the configuration file. It is possible to have
+multiple
+.Fl i
+options (and multiple identities specified in
+configuration files).
+.It Fl g
+Allows remote hosts to connect to local forwarded ports.
+.It Fl k
+Disables forwarding of Kerberos tickets and AFS tokens. This may
+also be specified on a per-host basis in the configuration file.
+.It Fl l Ar login_name
+Specifies the user to log in as on the remote machine. This may also
+be specified on a per-host basis in the configuration file.
+.It Fl n
+Redirects stdin from
+.Pa /dev/null
+(actually, prevents reading from stdin).
+This must be used when
+.Nm
+is run in the background. A common trick is to use this to run X11
+programs in a remote machine. For example,
+.Ic ssh -n shadows.cs.hut.fi emacs &
+will start an emacs on shadows.cs.hut.fi, and the X11
+connection will be automatically forwarded over an encrypted channel.
+The
+.Nm
+program will be put in the background.
+(This does not work if
+.Nm
+needs to ask for a password or passphrase; see also the
+.Fl f
+option.)
+.It Fl o Ar option
+Can be used to give options in the format used in the config file.
+This is useful for specifying options for which there is no separate
+command-line flag. The option has the same format as a line in the
+configuration file.
+.It Fl p Ar port
+Port to connect to on the remote host. This can be specified on a
+per-host basis in the configuration file.
+.It Fl P
+Use a non-privileged port for outgoing connections.
+This can be used if your firewall does
+not permit connections from privileged ports.
+Note that this option turns of
+.Cm RhostsAuthentication
+and
+.Cm RhostsRSAAuthentication .
+.It Fl q
+Quiet mode. Causes all warning and diagnostic messages to be
+suppressed. Only fatal errors are displayed.
+.It Fl t
+Force pseudo-tty allocation. This can be used to execute arbitary
+screen-based programs on a remote machine, which can be very useful
+e.g. when implementing menu services.
+.It Fl v
+Verbose mode. Causes
+.Nm
+to print debugging messages about its progress. This is helpful in
+debugging connection, authentication, and configuration problems.
+The verbose mode is also used to display
+.Xr skey 1
+challenges, if the user entered "s/key" as password.
+.It Fl x
+Disables X11 forwarding. This can also be specified on a per-host
+basis in a configuration file.
+.It Fl X
+Enables X11 forwarding.
+.It Fl C
+Requests compression of all data (including stdin, stdout, stderr, and
+data for forwarded X11 and TCP/IP connections). The compression
+algorithm is the same used by gzip, and the
+.Dq level
+can be controlled by the
+.Cm CompressionLevel
+option (see below). Compression is desirable on modem lines and other
+slow connections, but will only slow down things on fast networks.
+The default value can be set on a host-by-host basis in the
+configuration files; see the
+.Cm Compress
+option below.
+.It Fl L Ar port:host:hostport
+Specifies that the given port on the local (client) host is to be
+forwarded to the given host and port on the remote side. This works
+by allocating a socket to listen to
+.Ar port
+on the local side, and whenever a connection is made to this port, the
+connection is forwarded over the secure channel, and a connection is
+made to
+.Ar host:hostport
+from the remote machine. Port forwardings can also be specified in the
+configuration file. Only root can forward privileged ports.
+.It Fl R Ar port:host:hostport
+Specifies that the given port on the remote (server) host is to be
+forwarded to the given host and port on the local side. This works
+by allocating a socket to listen to
+.Ar port
+on the remote side, and whenever a connection is made to this port, the
+connection is forwarded over the secure channel, and a connection is
+made to
+.Ar host:hostport
+from the local machine. Port forwardings can also be specified in the
+configuration file. Privileged ports can be forwarded only when
+logging in as root on the remote machine.
+.El
+.Sh CONFIGURATION FILES
+.Nm
+obtains configuration data from the following sources (in this order):
+command line options, user's configuration file
+.Pq Pa $HOME/.ssh/config ,
+and system-wide configuration file
+.Pq Pa /etc/ssh_config .
+For each parameter, the first obtained value
+will be used. The configuration files contain sections bracketed by
+"Host" specifications, and that section is only applied for hosts that
+match one of the patterns given in the specification. The matched
+host name is the one given on the command line.
+.Pp
+Since the first obtained value for each parameter is used, more
+host-specific declarations should be given near the beginning of the
+file, and general defaults at the end.
+.Pp
+The configuration file has the following format:
+.Pp
+Empty lines and lines starting with
+.Ql #
+are comments.
+.Pp
+Otherwise a line is of the format
+.Dq keyword arguments .
+The possible
+keywords and their meanings are as follows (note that the
+configuration files are case-sensitive):
+.Bl -tag -width Ds
+.It Cm Host
+Restricts the following declarations (up to the next
+.Cm Host
+keyword) to be only for those hosts that match one of the patterns
+given after the keyword.
+.Ql \&*
+and
+.Ql ?
+can be used as wildcards in the
+patterns. A single
+.Ql \&*
+as a pattern can be used to provide global
+defaults for all hosts. The host is the
+.Ar hostname
+argument given on the command line (i.e., the name is not converted to
+a canonicalized host name before matching).
+.It Cm AFSTokenPassing
+Specifies whether to pass AFS tokens to remote host. The argument to
+this keyword must be
+.Dq yes
+or
+.Dq no .
+.It Cm BatchMode
+If set to
+.Dq yes ,
+passphrase/password querying will be disabled. This
+option is useful in scripts and other batch jobs where you have no
+user to supply the password. The argument must be
+.Dq yes
+or
+.Dq no .
+.It Cm Cipher
+Specifies the cipher to use for encrypting the session. Currently,
+.Dq blowfish ,
+and
+.Dq 3des
+are supported. The default is
+.Dq 3des .
+.It Cm Compression
+Specifies whether to use compression. The argument must be
+.Dq yes
+or
+.Dq no .
+.It Cm CompressionLevel
+Specifies the compression level to use if compression is enable. The
+argument must be an integer from 1 (fast) to 9 (slow, best). The
+default level is 6, which is good for most applications. The meaning
+of the values is the same as in GNU GZIP.
+.It Cm ConnectionAttempts
+Specifies the number of tries (one per second) to make before falling
+back to rsh or exiting. The argument must be an integer. This may be
+useful in scripts if the connection sometimes fails.
+.It Cm EscapeChar
+Sets the escape character (default:
+.Ql ~ ) .
+The escape character can also
+be set on the command line. The argument should be a single
+character,
+.Ql ^
+followed by a letter, or
+.Dq none
+to disable the escape
+character entirely (making the connection transparent for binary
+data).
+.It Cm FallBackToRsh
+Specifies that if connecting via
+.Nm
+fails due to a connection refused error (there is no
+.Xr sshd 8
+listening on the remote host),
+.Xr rsh 1
+should automatically be used instead (after a suitable warning about
+the session being unencrypted). The argument must be
+.Dq yes
+or
+.Dq no .
+.It Cm ForwardAgent
+Specifies whether the connection to the authentication agent (if any)
+will be forwarded to the remote machine. The argument must be
+.Dq yes
+or
+.Dq no .
+.It Cm ForwardX11
+Specifies whether X11 connections will be automatically redirected
+over the secure channel and
+.Ev DISPLAY
+set. The argument must be
+.Dq yes
+or
+.Dq no .
+.It Cm GatewayPorts
+Specifies whether remote hosts are allowed to connect to local
+forwarded ports.
+The argument must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq no .
+.It Cm GlobalKnownHostsFile
+Specifies a file to use instead of
+.Pa /etc/ssh_known_hosts .
+.It Cm HostName
+Specifies the real host name to log into. This can be used to specify
+nicnames or abbreviations for hosts. Default is the name given on the
+command line. Numeric IP addresses are also permitted (both on the
+command line and in
+.Cm HostName
+specifications).
+.It Cm IdentityFile
+Specifies the file from which the user's RSA authentication identity
+is read (default
+.Pa .ssh/identity
+in the user's home directory).
+Additionally, any identities represented by the authentication agent
+will be used for authentication. The file name may use the tilde
+syntax to refer to a user's home directory. It is possible to have
+multiple identity files specified in configuration files; all these
+identities will be tried in sequence.
+.It Cm KeepAlive
+Specifies whether the system should send keepalive messages to the
+other side. If they are sent, death of the connection or crash of one
+of the machines will be properly noticed. However, this means that
+connections will die if the route is down temporarily, and some people
+find it annoying.
+.Pp
+The default is
+.Dq yes
+(to send keepalives), and the client will notice
+if the network goes down or the remote host dies. This is important
+in scripts, and many users want it too.
+.Pp
+To disable keepalives, the value should be set to
+.Dq no
+in both the server and the client configuration files.
+.It Cm KerberosAuthentication
+Specifies whether Kerberos authentication will be used. The argument to
+this keyword must be
+.Dq yes
+or
+.Dq no .
+.It Cm KerberosTgtPassing
+Specifies whether a Kerberos TGT will be forwarded to the server. This
+will only work if the Kerberos server is actually an AFS kaserver. The
+argument to this keyword must be
+.Dq yes
+or
+.Dq no .
+.It Cm LocalForward
+Specifies that a TCP/IP port on the local machine be forwarded over
+the secure channel to given host:port from the remote machine. The
+first argument must be a port number, and the second must be
+host:port. Multiple forwardings may be specified, and additional
+forwardings can be given on the command line. Only the root can
+forward privileged ports.
+.It Cm PasswordAuthentication
+Specifies whether to use password authentication. The argument to
+this keyword must be
+.Dq yes
+or
+.Dq no .
+.It Cm NumberOfPasswordPrompts
+Specifies the number of password prompts before giving up. The
+argument to this keyword must be an integer. Default is 3.
+.It Cm Port
+Specifies the port number to connect on the remote host. Default is
+22.
+.It Cm ProxyCommand
+Specifies the command to use to connect to the server. The command
+string extends to the end of the line, and is executed with /bin/sh.
+In the command string, %h will be substituted by the host name to
+connect and %p by the port. The command can be basically anything,
+and should read from its stdin and write to its stdout. It should
+eventually connect an
+.Xr sshd 8
+server running on some machine, or execute
+.Ic sshd -i
+somewhere. Host key management will be done using the
+HostName of the host being connected (defaulting to the name typed by
+the user).
+.Pp
+.It Cm RemoteForward
+Specifies that a TCP/IP port on the remote machine be forwarded over
+the secure channel to given host:port from the local machine. The
+first argument must be a port number, and the second must be
+host:port. Multiple forwardings may be specified, and additional
+forwardings can be given on the command line. Only the root can
+forward privileged ports.
+.It Cm RhostsAuthentication
+Specifies whether to try rhosts based authentication. Note that this
+declaration only affects the client side and has no effect whatsoever
+on security. Disabling rhosts authentication may reduce
+authentication time on slow connections when rhosts authentication is
+not used. Most servers do not permit RhostsAuthentication because it
+is not secure (see RhostsRSAAuthentication). The argument to this
+keyword must be
+.Dq yes
+or
+.Dq no .
+.It Cm RhostsRSAAuthentication
+Specifies whether to try rhosts based authentication with RSA host
+authentication. This is the primary authentication method for most
+sites. The argument must be
+.Dq yes
+or
+.Dq no .
+.It Cm RSAAuthentication
+Specifies whether to try RSA authentication. The argument to this
+keyword must be
+.Dq yes
+or
+.Dq no .
+RSA authentication will only be
+attempted if the identity file exists, or an authentication agent is
+running.
+.It Cm CheckHostIP
+If this flag is set to
+.Dq yes ,
+ssh will additionally check the host ip address in the
+.Pa known_hosts
+file. This allows ssh to detect if a host key changed due to DNS spoofing.
+If the option is set to
+.Dq no ,
+the check will not be executed.
+.It Cm StrictHostKeyChecking
+If this flag is set to
+.Dq yes ,
+.Nm
+ssh will never automatically add host keys to the
+.Pa $HOME/.ssh/known_hosts
+file, and refuses to connect hosts whose host key has changed. This
+provides maximum protection against trojan horse attacks. However, it
+can be somewhat annoying if you don't have good
+.Pa /etc/ssh_known_hosts
+files installed and frequently
+connect new hosts. Basically this option forces the user to manually
+add any new hosts. Normally this option is disabled, and new hosts
+will automatically be added to the known host files. The host keys of
+known hosts will be verified automatically in either case. The
+argument must be
+.Dq yes
+or
+.Dq no .
+.It Cm User
+Specifies the user to log in as. This can be useful if you have a
+different user name in different machines. This saves the trouble of
+having to remember to give the user name on the command line.
+.It Cm UserKnownHostsFile
+Specifies a file to use instead of
+.Pa $HOME/.ssh/known_hosts .
+.It Cm UsePrivilegedPort
+Specifies whether to use a privileged port for outgoing connections.
+The argument must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq yes .
+Note that setting this option to
+.Dq no
+turns of
+.Cm RhostsAuthentication
+and
+.Cm RhostsRSAAuthentication .
+.It Cm UseRsh
+Specifies that rlogin/rsh should be used for this host. It is
+possible that the host does not at all support the
+.Nm
+protocol. This causes
+.Nm
+to immediately exec
+.Xr rsh 1 .
+All other options (except
+.Cm HostName )
+are ignored if this has been specified. The argument must be
+.Dq yes
+or
+.Dq no .
+.Sh ENVIRONMENT
+.Nm
+will normally set the following environment variables:
+.Bl -tag -width Ds
+.It Ev DISPLAY
+The
+.Ev DISPLAY
+variable indicates the location of the X11 server. It is
+automatically set by
+.Nm
+to point to a value of the form
+.Dq hostname:n
+where hostname indicates
+the host where the shell runs, and n is an integer >= 1. Ssh uses
+this special value to forward X11 connections over the secure
+channel. The user should normally not set DISPLAY explicitly, as that
+will render the X11 connection insecure (and will require the user to
+manually copy any required authorization cookies).
+.It Ev HOME
+Set to the path of the user's home directory.
+.It Ev LOGNAME
+Synonym for
+.Ev USER ;
+set for compatibility with systems that use this variable.
+.It Ev MAIL
+Set to point the user's mailbox.
+.It Ev PATH
+Set to the default
+.Ev PATH ,
+as specified when compiling
+.Nm ssh .
+.It Ev SSH_AUTH_SOCK
+indicates the path of a unix-domain socket used to communicate with the
+agent.
+.It Ev SSH_CLIENT
+Identifies the client end of the connection. The variable contains
+three space-separated values: client ip-address, client port number,
+and server port number.
+.It Ev SSH_TTY
+This is set to the name of the tty (path to the device) associated
+with the current shell or command. If the current session has no tty,
+this variable is not set.
+.It Ev TZ
+The timezone variable is set to indicate the present timezone if it
+was set when the daemon was started (e.i., the daemon passes the value
+on to new connections).
+.It Ev USER
+Set to the name of the user logging in.
+.El
+.Pp
+Additionally,
+.Nm
+reads
+.Pa $HOME/.ssh/environment ,
+and adds lines of the format
+.Dq VARNAME=value
+to the environment.
+.Sh FILES
+.Bl -tag -width $HOME/.ssh/known_hosts
+.It Pa $HOME/.ssh/known_hosts
+Records host keys for all hosts the user has logged into (that are not
+in
+.Pa /etc/ssh_known_hosts ) .
+See
+.Xr sshd 8 .
+.It Pa $HOME/.ssh/random_seed
+Used for seeding the random number generator. This file contains
+sensitive data and should read/write for the user and not accessible
+for others. This file is created the first time the program is run
+and updated automatically. The user should never need to read or
+modify this file.
+.It Pa $HOME/.ssh/identity
+Contains the RSA authentication identity of the user. This file
+contains sensitive data and should be readable by the user but not
+accessible by others (read/write/execute).
+Note that
+.Nm
+ignores this file if it is accessible by others.
+It is possible to specify a passphrase when
+generating the key; the passphrase will be used to encrypt the
+sensitive part of this file using 3DES.
+.It Pa $HOME/.ssh/identity.pub
+Contains the public key for authentication (public part of the
+identity file in human-readable form). The contents of this file
+should be added to
+.Pa $HOME/.ssh/authorized_keys
+on all machines
+where you wish to log in using RSA authentication. This file is not
+sensitive and can (but need not) be readable by anyone. This file is
+never used automatically and is not necessary; it is only provided for
+the convenience of the user.
+.It Pa $HOME/.ssh/config
+This is the per-user configuration file. The format of this file is
+described above. This file is used by the
+.Nm
+client. This file does not usually contain any sensitive information,
+but the recommended permissions are read/write for the user, and not
+accessible by others.
+.It Pa $HOME/.ssh/authorized_keys
+Lists the RSA keys that can be used for logging in as this user. The
+format of this file is described in the
+.Xr sshd 8
+manual page. In the simplest form the format is the same as the .pub
+identity files (that is, each line contains the number of bits in
+modulus, public exponent, modulus, and comment fields, separated by
+spaces). This file is not highly sensitive, but the recommended
+permissions are read/write for the user, and not accessible by others.
+.It Pa /etc/ssh_known_hosts
+Systemwide list of known host keys. This file should be prepared by the
+system administrator to contain the public host keys of all machines in the
+organization. This file should be world-readable. This file contains
+public keys, one per line, in the following format (fields separated
+by spaces): system name, number of bits in modulus, public exponent,
+modulus, and optional comment field. When different names are used
+for the same machine, all such names should be listed, separated by
+commas. The format is described on the
+.Xr sshd 8
+manual page.
+.Pp
+The canonical system name (as returned by name servers) is used by
+.Xr sshd 8
+to verify the client host when logging in; other names are needed because
+.Nm
+does not convert the user-supplied name to a canonical name before
+checking the key, because someone with access to the name servers
+would then be able to fool host authentication.
+.It Pa /etc/ssh_config
+Systemwide configuration file. This file provides defaults for those
+values that are not specified in the user's configuration file, and
+for those users who do not have a configuration file. This file must
+be world-readable.
+.It Pa $HOME/.rhosts
+This file is used in
+.Pa \&.rhosts
+authentication to list the
+host/user pairs that are permitted to log in. (Note that this file is
+also used by rlogin and rsh, which makes using this file insecure.)
+Each line of the file contains a host name (in the canonical form
+returned by name servers), and then a user name on that host,
+separated by a space. One some machines this file may need to be
+world-readable if the user's home directory is on a NFS partition,
+because
+.Xr sshd 8
+reads it as root. Additionally, this file must be owned by the user,
+and must not have write permissions for anyone else. The recommended
+permission for most machines is read/write for the user, and not
+accessible by others.
+.Pp
+Note that by default
+.Xr sshd 8
+will be installed so that it requires successful RSA host
+authentication before permitting \s+2.\s0rhosts authentication. If your
+server machine does not have the client's host key in
+.Pa /etc/ssh_known_hosts ,
+you can store it in
+.Pa $HOME/.ssh/known_hosts .
+The easiest way to do this is to
+connect back to the client from the server machine using ssh; this
+will automatically add the host key inxi
+.Pa $HOME/.ssh/known_hosts .
+.It Pa $HOME/.shosts
+This file is used exactly the same way as
+.Pa \&.rhosts .
+The purpose for
+having this file is to be able to use rhosts authentication with
+.Nm
+without permitting login with
+.Xr rlogin 1
+or
+.Xr rsh 1 .
+.It Pa /etc/hosts.equiv
+This file is used during
+.Pa \&.rhosts authentication. It contains
+canonical hosts names, one per line (the full format is described on
+the
+.Xr sshd 8
+manual page). If the client host is found in this file, login is
+automatically permitted provided client and server user names are the
+same. Additionally, successful RSA host authentication is normally
+required. This file should only be writable by root.
+.It Pa /etc/shosts.equiv
+This file is processed exactly as
+.Pa /etc/hosts.equiv .
+This file may be useful to permit logins using
+.Nm
+but not using rsh/rlogin.
+.It Pa /etc/sshrc
+Commands in this file are executed by
+.Nm
+when the user logs in just before the user's shell (or command) is started.
+See the
+.Xr sshd 8
+manual page for more information.
+.It Pa $HOME/.ssh/rc
+Commands in this file are executed by
+.Nm
+when the user logs in just before the user's shell (or command) is
+started.
+See the
+.Xr sshd 8
+manual page for more information.
+.It Pa libcrypto.so.X.1
+A version of this library which includes support for the RSA algorithm
+is required for proper operation.
+.Sh AUTHOR
+Tatu Ylonen <ylo@cs.hut.fi>
+.Pp
+Issues can be found from the SSH WWW home page:
+.Pp
+.Dl http://www.cs.hut.fi/ssh
+.Pp
+OpenSSH
+is a derivative of the original (free) ssh 1.2.12 release, but with bugs
+removed and newer features re-added. Rapidly after the 1.2.12 release,
+newer versions bore successively more restrictive licenses. This version
+of OpenSSH
+.Bl -bullet
+.It
+has all components of a restrictive nature (ie. patents, see
+.Xr ssl 8 )
+directly removed from the source code; any licensed or patented components
+are chosen from
+external libraries.
+.It
+has been updated to support ssh protocol 1.5.
+.It
+contains added support for
+.Xr kerberos 8
+authentication and ticket passing.
+.It
+supports one-time password authentication with
+.Xr skey 1 .
+.El
+.Pp
+The libraries described in
+.Xr ssl 8
+are required for proper operation.
+.Sh SEE ALSO
+.Xr rlogin 1 ,
+.Xr rsh 1 ,
+.Xr scp 1 ,
+.Xr ssh-add 1 ,
+.Xr ssh-agent 1 ,
+.Xr ssh-keygen 1 ,
+.Xr telnet 1 ,
+.Xr sshd 8 ,
+.Xr ssl 8
diff --git a/sshd.8 b/sshd.8
new file mode 100644
index 00000000..a5c3f955
--- /dev/null
+++ b/sshd.8
@@ -0,0 +1,781 @@
+.\" -*- nroff -*-
+.\"
+.\" sshd.8.in
+.\"
+.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
+.\"
+.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+.\" All rights reserved
+.\"
+.\" Created: Sat Apr 22 21:55:14 1995 ylo
+.\"
+.\" $Id: sshd.8,v 1.3 1999/10/28 23:15:50 damien Exp $
+.\"
+.Dd September 25, 1999
+.Dt SSHD 8
+.Os
+.Sh NAME
+.Nm sshd
+.Nd secure shell daemon
+.Sh SYNOPSIS
+.Nm sshd
+.Op Fl diq
+.Op Fl b Ar bits
+.Op Fl f Ar config_file
+.Op Fl g Ar login_grace_time
+.Op Fl h Ar host_key_file
+.Op Fl k Ar key_gen_time
+.Op Fl p Ar port
+.Sh DESCRIPTION
+.Nm
+(Secure Shell Daemon) is the daemon program for
+.Xr ssh 1 .
+Together these programs replace rlogin and rsh programs, and
+provide secure encrypted communications between two untrusted hosts
+over an insecure network. The programs are intended to be as easy to
+install and use as possible.
+.Pp
+.Nm
+is the daemon that listens for connections from clients. It is
+normally started at boot from
+.Pa /etc/rc .
+It forks a new
+daemon for each incoming connection. The forked daemons handle
+key exchange, encryption, authentication, command execution,
+and data exchange.
+.Pp
+.Nm
+works as follows. Each host has a host-specific RSA key
+(normally 1024 bits) used to identify the host. Additionally, when
+the daemon starts, it generates a server RSA key (normally 768 bits).
+This key is normally regenerated every hour if it has been used, and
+is never stored on disk.
+.Pp
+Whenever a client connects the daemon, the daemon sends its host
+and server public keys to the client. The client compares the
+host key against its own database to verify that it has not changed.
+The client then generates a 256 bit random number. It encrypts this
+random number using both the host key and the server key, and sends
+the encrypted number to the server. Both sides then start to use this
+random number as a session key which is used to encrypt all further
+communications in the session. The rest of the session is encrypted
+using a conventional cipher, currently Blowfish and 3DES, with 3DES
+being is used by default. The client selects the encryption algorithm
+to use from those offered by the server.
+.Pp
+Next, the server and the client enter an authentication dialog. The
+client tries to authenticate itself using
+.Pa .rhosts
+authentication,
+.Pa .rhosts
+authentication combined with RSA host
+authentication, RSA challenge-response authentication, or password
+based authentication.
+.Pp
+Rhosts authentication is normally disabled
+because it is fundamentally insecure, but can be enabled in the server
+configuration file if desired. System security is not improved unless
+.Xr rshd 8 ,
+.Xr rlogind 8 ,
+.Xr rexecd 8 ,
+and
+.Xr rexd 8
+are disabled (thus completely disabling
+.Xr rlogin 1
+and
+.Xr rsh 1
+into that machine).
+.Pp
+If the client successfully authenticates itself, a dialog for
+preparing the session is entered. At this time the client may request
+things like allocating a pseudo-tty, forwarding X11 connections,
+forwarding TCP/IP connections, or forwarding the authentication agent
+connection over the secure channel.
+.Pp
+Finally, the client either requests a shell or execution of a command.
+The sides then enter session mode. In this mode, either side may send
+data at any time, and such data is forwarded to/from the shell or
+command on the server side, and the user terminal in the client side.
+.Pp
+When the user program terminates and all forwarded X11 and other
+connections have been closed, the server sends command exit status to
+the client, and both sides exit.
+.Pp
+.Nm
+can be configured using command-line options or a configuration
+file. Command-line options override values specified in the
+configuration file.
+.Pp
+The options are as follows:
+.Bl -tag -width Ds
+.It Fl b Ar bits
+Specifies the number of bits in the server key (default 768).
+.Pp
+.It Fl d
+Debug mode. The server sends verbose debug output to the system
+log, and does not put itself in the background. The server also will
+not fork and will only process one connection. This option is only
+intended for debugging for the server.
+.It Fl f Ar configuration_file
+Specifies the name of the configuration file. The default is
+.Pa /etc/sshd_config .
+.Nm
+refuses to start if there is no configuration file.
+.It Fl g Ar login_grace_time
+Gives the grace time for clients to authenticate themselves (default
+300 seconds). If the client fails to authenticate the user within
+this many seconds, the server disconnects and exits. A value of zero
+indicates no limit.
+.It Fl h Ar host_key_file
+Specifies the file from which the host key is read (default
+.Pa /etc/ssh_host_key ) .
+This option must be given if
+.Nm
+is not run as root (as the normal
+host file is normally not readable by anyone but root).
+.It Fl i
+Specifies that
+.Nm
+is being run from inetd.
+.Nm
+is normally not run
+from inetd because it needs to generate the server key before it can
+respond to the client, and this may take tens of seconds. Clients
+would have to wait too long if the key was regenerated every time.
+However, with small key sizes (e.g. 512) using
+.Nm
+from inetd may
+be feasible.
+.It Fl k Ar key_gen_time
+Specifies how often the server key is regenerated (default 3600
+seconds, or one hour). The motivation for regenerating the key fairly
+often is that the key is not stored anywhere, and after about an hour,
+it becomes impossible to recover the key for decrypting intercepted
+communications even if the machine is cracked into or physically
+seized. A value of zero indicates that the key will never be regenerated.
+.It Fl p Ar port
+Specifies the port on which the server listens for connections
+(default 22).
+.It Fl q
+Quiet mode. Nothing is sent to the system log. Normally the beginning,
+authentication, and termination of each connection is logged.
+.It Fl Q
+Do not print an error message if RSA support is missing.
+.El
+.Sh CONFIGURATION FILE
+.Nm
+reads configuration data from
+.Pa /etc/sshd_config
+(or the file specified with
+.Fl f
+on the command line). The file
+contains keyword-value pairs, one per line. Lines starting with
+.Ql #
+and empty lines are interpreted as comments.
+.Pp
+The following keywords are possible.
+.Bl -tag -width Ds
+.It Cm AFSTokenPassing
+Specifies whether an AFS token may be forwarded to the server. Default is
+.Dq yes .
+.It Cm AllowGroups
+This keyword can be followed by a number of group names, separated
+by spaces. If specified, login is allowed only for users whose primary
+group matches one of the patterns.
+.Ql \&*
+and
+.Ql ?
+can be used as
+wildcards in the patterns. Only group names are valid, a numerical group
+id isn't recognized. By default login is allowed regardless of
+the primary group.
+.Pp
+.It Cm AllowUsers
+This keyword can be followed by a number of user names, separated
+by spaces. If specified, login is allowed only for users names that
+match one of the patterns.
+.Ql \&*
+and
+.Ql ?
+can be used as
+wildcards in the patterns. Only user names are valid, a numerical user
+id isn't recognized. By default login is allowed regardless of
+the user name.
+.Pp
+.It Cm CheckMail
+Specifies whether
+.Nm
+should check for new mail for interactive logins.
+The default is
+.Dq no .
+.It Cm DenyGroups
+This keyword can be followed by a number of group names, separated
+by spaces. Users whose primary group matches one of the patterns
+aren't allowed to log in.
+.Ql \&*
+and
+.Ql ?
+can be used as
+wildcards in the patterns. Only group names are valid, a numerical group
+id isn't recognized. By default login is allowed regardless of
+the primary group.
+.Pp
+.It Cm DenyUsers
+This keyword can be followed by a number of user names, separated
+by spaces. Login is allowed disallowed for user names that match
+one of the patterns.
+.Ql \&*
+and
+.Ql ?
+can be used as
+wildcards in the patterns. Only user names are valid, a numerical user
+id isn't recognized. By default login is allowed regardless of
+the user name.
+.Pp
+.It Cm FascistLogging
+Specifies whether to use verbose logging. Verbose logging violates
+the privacy of users and is not recommended. The argument must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq no .
+.It Cm HostKey
+Specifies the file containing the private host key (default
+.Pa /etc/ssh_host_key ) .
+Note that
+.Nm
+does not start if this file is group/world-accessible.
+.It Cm IgnoreRhosts
+Specifies that rhosts and shosts files will not be used in
+authentication.
+.Pa /etc/hosts.equiv
+and
+.Pa /etc/shosts.equiv
+are still used. The default is
+.Dq no .
+.It Cm KeepAlive
+Specifies whether the system should send keepalive messages to the
+other side. If they are sent, death of the connection or crash of one
+of the machines will be properly noticed. However, this means that
+connections will die if the route is down temporarily, and some people
+find it annoying. On the other hand, if keepalives are not send,
+sessions may hang indefinitely on the server, leaving
+.Dq ghost
+users and consuming server resources.
+.Pp
+The default is
+.Dq yes
+(to send keepalives), and the server will notice
+if the network goes down or the client host reboots. This avoids
+infinitely hanging sessions.
+.Pp
+To disable keepalives, the value should be set to
+.Dq no
+in both the server and the client configuration files.
+.It Cm KerberosAuthentication
+Specifies whether Kerberos authentication is allowed. This can
+be in the form of a Kerberos ticket, or if
+.Cm PasswordAuthentication
+is yes, the password provided by the user will be validated through
+the Kerberos KDC. Default is
+.Dq yes .
+.It Cm KerberosOrLocalPasswd
+If set then if password authentication through Kerberos fails then
+the password will be validated via any additional local mechanism
+such as
+.Pa /etc/passwd
+or SecurID. Default is
+.Dq yes .
+.It Cm KerberosTgtPassing
+Specifies whether a Kerberos TGT may be forwarded to the server.
+Default is
+.Dq no ,
+as this only works when the Kerberos KDC is actually an AFS kaserver.
+.It Cm KerberosTicketCleanup
+Specifies whether to automatically destroy the user's ticket cache
+file on logout. Default is
+.Dq yes .
+.It Cm KeyRegenerationInterval
+The server key is automatically regenerated after this many seconds
+(if it has been used). The purpose of regeneration is to prevent
+decrypting captured sessions by later breaking into the machine and
+stealing the keys. The key is never stored anywhere. If the value is
+0, the key is never regenerated. The default is 3600
+(seconds).
+.It Cm ListenAddress
+Specifies what local address
+.Nm
+should listen on.
+The default is to listen to all local addresses.
+.It Cm LoginGraceTime
+The server disconnects after this time if the user has not
+successfully logged in. If the value is 0, there is no time limit.
+The default is 600 (seconds).
+.It Cm PasswordAuthentication
+Specifies whether password authentication is allowed.
+The default is
+.Dq yes .
+.It Cm PermitEmptyPasswords
+When password authentication is allowed, it specifies whether the
+server allows login to accounts with empty password strings. The default
+is
+.Dq yes .
+.It Cm PermitRootLogin
+Specifies whether the root can log in using
+.Xr ssh 1 .
+The argument must be
+.Dq yes ,
+.Dq without-password
+or
+.Dq no .
+The default is
+.Dq yes .
+If this options is set to
+.Dq without-password
+only password authentication is disabled for root.
+.Pp
+Root login with RSA authentication when the
+.Ar command
+option has been
+specified will be allowed regardless of the value of this setting
+(which may be useful for taking remote backups even if root login is
+normally not allowed).
+.It Cm Port
+Specifies the port number that
+.Nm
+listens on. The default is 22.
+.It Cm PrintMotd
+Specifies whether
+.Nm
+should print
+.Pa /etc/motd
+when a user logs in interactively. (On some systems it is also
+printed by the shell,
+.Pa /etc/profile ,
+or equivalent.) The default is
+.Dq yes .
+.It Cm QuietMode
+Specifies whether the system runs in quiet mode. In quiet mode,
+nothing is logged in the system log, except fatal errors. The default
+is
+.Dq no .
+.It Cm RandomSeed
+Obsolete. Random number generation uses other techniques.
+.It Cm RhostsAuthentication
+Specifies whether authentication using rhosts or /etc/hosts.equiv
+files is sufficient. Normally, this method should not be permitted
+because it is insecure.
+.Cm RhostsRSAAuthentication
+should be used
+instead, because it performs RSA-based host authentication in addition
+to normal rhosts or /etc/hosts.equiv authentication.
+The default is
+.Dq no .
+.It Cm RhostsRSAAuthentication
+Specifies whether rhosts or /etc/hosts.equiv authentication together
+with successful RSA host authentication is allowed. The default is
+.Dq yes .
+.It Cm RSAAuthentication
+Specifies whether pure RSA authentication is allowed. The default is
+.Dq yes .
+.It Cm ServerKeyBits
+Defines the number of bits in the server key. The minimum value is
+512, and the default is 768.
+.It Cm SkeyAuthentication
+Specifies whether
+.Xr skey 1
+authentication is allowed. The default is
+.Dq yes .
+Note that s/key authentication is enabled only if
+.Cm PasswordAuthentication
+is allowed, too.
+.It Cm StrictModes
+Specifies whether
+.Nm
+should check file modes and ownership of the
+user's files and home directory before accepting login. This
+is normally desirable because novices sometimes accidentally leave their
+directory or files world-writable. The default is
+.Dq yes .
+.It Cm SyslogFacility
+Gives the facility code that is used when logging messages from
+.Nm sshd .
+The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
+LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. The default is AUTH.
+.It Cm UseLogin
+Specifies whether
+.Xr login 1
+is used. The default is
+.Dq no .
+.It Cm X11Forwarding
+Specifies whether X11 forwarding is permitted. The default is
+.Dq yes .
+Note that disabling X11 forwarding does not improve security in any
+way, as users can always install their own forwarders.
+.It Cm X11DisplayOffset
+Specifies the first display number available for
+.Nm sshd Ns 's
+X11 forwarding. This prevents
+.Nm
+from interfering with real X11 servers.
+.El
+.Sh LOGIN PROCESS
+When a user successfully logs in,
+.Nm
+does the following:
+.Bl -enum -offset indent
+.It
+If the login is on a tty, and no command has been specified,
+prints last login time and
+.Pa /etc/motd
+(unless prevented in the configuration file or by
+.Pa $HOME/.hushlogin ;
+see the
+.Sx FILES
+section).
+.It
+If the login is on a tty, records login time.
+.It
+Checks
+.Pa /etc/nologin ;
+if it exists, prints contents and quits
+(unless root).
+.It
+Changes to run with normal user privileges.
+.It
+Sets up basic environment.
+.It
+Reads
+.Pa $HOME/.ssh/environment
+if it exists.
+.It
+Changes to user's home directory.
+.It
+If
+.Pa $HOME/.ssh/rc
+exists, runs it; else if
+.Pa /etc/sshrc
+exists, runs
+it; otherwise runs xauth. The
+.Dq rc
+files are given the X11
+authentication protocol and cookie in standard input.
+.It
+Runs user's shell or command.
+.El
+.Sh AUTHORIZED_KEYS FILE FORMAT
+The
+.Pa $HOME/.ssh/authorized_keys
+file lists the RSA keys that are
+permitted for RSA authentication. Each line of the file contains one
+key (empty lines and lines starting with a
+.Ql #
+are ignored as
+comments). Each line consists of the following fields, separated by
+spaces: options, bits, exponent, modulus, comment. The options field
+is optional; its presence is determined by whether the line starts
+with a number or not (the option field never starts with a number).
+The bits, exponent, modulus and comment fields give the RSA key; the
+comment field is not used for anything (but may be convenient for the
+user to identify the key).
+.Pp
+Note that lines in this file are usually several hundred bytes long
+(because of the size of the RSA key modulus). You don't want to type
+them in; instead, copy the
+.Pa identity.pub
+file and edit it.
+.Pp
+The options (if present) consists of comma-separated option
+specifications. No spaces are permitted, except within double quotes.
+The following option specifications are supported:
+.Bl -tag -width Ds
+.It Cm from="pattern-list"
+Specifies that in addition to RSA authentication, the canonical name
+of the remote host must be present in the comma-separated list of
+patterns ('*' and '?' serve as wildcards). The list may also contain
+patterns negated by prefixing them with '!'; if the canonical host
+name matches a negated pattern, the key is not accepted. The purpose
+of this option is to optionally increase security: RSA authentication
+by itself does not trust the network or name servers or anything (but
+the key); however, if somebody somehow steals the key, the key
+permits an intruder to log in from anywhere in the world. This
+additional option makes using a stolen key more difficult (name
+servers and/or routers would have to be compromised in addition to
+just the key).
+.It Cm command="command"
+Specifies that the command is executed whenever this key is used for
+authentication. The command supplied by the user (if any) is ignored.
+The command is run on a pty if the connection requests a pty;
+otherwise it is run without a tty. A quote may be included in the
+command by quoting it with a backslash. This option might be useful
+to restrict certain RSA keys to perform just a specific operation. An
+example might be a key that permits remote backups but nothing
+else. Notice that the client may specify TCP/IP and/or X11
+forwardings unless they are explicitly prohibited.
+.It Cm environment="NAME=value"
+Specifies that the string is to be added to the environment when
+logging in using this key. Environment variables set this way
+override other default environment values. Multiple options of this
+type are permitted.
+.It Cm no-port-forwarding
+Forbids TCP/IP forwarding when this key is used for authentication.
+Any port forward requests by the client will return an error. This
+might be used, e.g., in connection with the
+.Cm command
+option.
+.It Cm no-X11-forwarding
+Forbids X11 forwarding when this key is used for authentication.
+Any X11 forward requests by the client will return an error.
+.It Cm no-agent-forwarding
+Forbids authentication agent forwarding when this key is used for
+authentication.
+.It Cm no-pty
+Prevents tty allocation (a request to allocate a pty will fail).
+.El
+.Ss Examples
+1024 33 12121.\|.\|.\|312314325 ylo@foo.bar
+.Pp
+from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23.\|.\|.\|2334 ylo@niksula
+.Pp
+command="dump /home",no-pty,no-port-forwarding 1024 33 23.\|.\|.\|2323 backup.hut.fi
+.Sh SSH_KNOWN_HOSTS FILE FORMAT
+The
+.Pa /etc/ssh_known_hosts
+and
+.Pa $HOME/.ssh/known_hosts
+files contain host public keys for all known hosts. The global file should
+be prepared by the admistrator (optional), and the per-user file is
+maintained automatically: whenever the user connects an unknown host
+its key is added to the per-user file.
+.Pp
+Each line in these files contains the following fields: hostnames,
+bits, exponent, modulus, comment. The fields are separated by spaces.
+.Pp
+Hostnames is a comma-separated list of patterns ('*' and '?' act as
+wildcards); each pattern in turn is matched against the canonical host
+name (when authenticating a client) or against the user-supplied
+name (when authenticating a server). A pattern may also be preceded
+by
+.Ql !
+to indicate negation: if the host name matches a negated
+pattern, it is not accepted (by that line) even if it matched another
+pattern on the line.
+.Pp
+Bits, exponent, and modulus are taken directly from the host key; they
+can be obtained, e.g., from
+.Pa /etc/ssh_host_key.pub .
+The optional comment field continues to the end of the line, and is not used.
+.Pp
+Lines starting with
+.Ql #
+and empty lines are ignored as comments.
+.Pp
+When performing host authentication, authentication is accepted if any
+matching line has the proper key. It is thus permissible (but not
+recommended) to have several lines or different host keys for the same
+names. This will inevitably happen when short forms of host names
+from different domains are put in the file. It is possible
+that the files contain conflicting information; authentication is
+accepted if valid information can be found from either file.
+.Pp
+Note that the lines in these files are typically hundreds of characters
+long, and you definitely don't want to type in the host keys by hand.
+Rather, generate them by a script
+or by taking
+.Pa /etc/ssh_host_key.pub
+and adding the host names at the front.
+.Ss Examples
+closenet,closenet.hut.fi,.\|.\|.\|,130.233.208.41 1024 37 159.\|.\|.93 closenet.hut.fi
+.Sh FILES
+.Bl -tag -width Ds
+.It Pa /etc/sshd_config
+Contains configuration data for
+.Nm sshd .
+This file should be writable by root only, but it is recommended
+(though not necessary) that it be world-readable.
+.It Pa /etc/ssh_host_key
+Contains the private part of the host key.
+This file should only be owned by root, readable only by root, and not
+accessible to others.
+Note that
+.Nm
+does not start if this file is group/world-accessible.
+.It Pa /etc/ssh_host_key.pub
+Contains the public part of the host key.
+This file should be world-readable but writable only by
+root. Its contents should match the private part. This file is not
+really used for anything; it is only provided for the convenience of
+the user so its contents can be copied to known hosts files.
+These two files are created using
+.Xr ssh-keygen 1 .
+.It Pa /var/run/sshd.pid
+Contains the process ID of the
+.Nm
+listening for connections (if there are several daemons running
+concurrently for different ports, this contains the pid of the one
+started last). The contents of this file are not sensitive; it can be
+world-readable.
+.It Pa $HOME/.ssh/authorized_keys
+Lists the RSA keys that can be used to log into the user's account.
+This file must be readable by root (which may on some machines imply
+it being world-readable if the user's home directory resides on an NFS
+volume). It is recommended that it not be accessible by others. The
+format of this file is described above.
+.It Pa /etc/ssh_known_hosts
+This file is consulted when using rhosts with RSA host
+authentication to check the public key of the host. The key must be
+listed in this file to be accepted.
+.It Pa $HOME/.ssh/known_hosts
+The client uses this file
+and
+.Pa /etc/ssh_known_hosts
+to verify that the remote host is the one we intended to
+connect. These files should be writable only by root/the owner.
+.Pa /etc/ssh_known_hosts
+should be world-readable, and
+.Pa $HOME/.ssh/known_hosts
+can but need not be world-readable.
+.It Pa /etc/nologin
+If this file exists,
+.Nm
+refuses to let anyone except root log in. The contents of the file
+are displayed to anyone trying to log in, and non-root connections are
+refused. The file should be world-readable.
+.It Pa /etc/hosts.allow, /etc/hosts.deny
+If compiled with
+.Sy LIBWRAP
+support, tcp-wrappers access controls may be defined here as described in
+.Xr hosts_access 5 .
+.It Pa $HOME/.rhosts
+This file contains host-username pairs, separated by a space, one per
+line. The given user on the corresponding host is permitted to log in
+without password. The same file is used by rlogind and rshd.
+The file must
+be writable only by the user; it is recommended that it not be
+accessible by others.
+.Pp
+If is also possible to use netgroups in the file. Either host or user
+name may be of the form +@groupname to specify all hosts or all users
+in the group.
+.It Pa $HOME/.shosts
+For ssh,
+this file is exactly the same as for
+.Pa .rhosts .
+However, this file is
+not used by rlogin and rshd, so using this permits access using SSH only.
+.Pa /etc/hosts.equiv
+This file is used during
+.Pa .rhosts
+authentication. In the
+simplest form, this file contains host names, one per line. Users on
+those hosts are permitted to log in without a password, provided they
+have the same user name on both machines. The host name may also be
+followed by a user name; such users are permitted to log in as
+.Em any
+user on this machine (except root). Additionally, the syntax
+.Dq +@group
+can be used to specify netgroups. Negated entries start with
+.Ql \&- .
+.Pp
+If the client host/user is successfully matched in this file, login is
+automatically permitted provided the client and server user names are the
+same. Additionally, successful RSA host authentication is normally
+required. This file must be writable only by root; it is recommended
+that it be world-readable.
+.Pp
+.Sy "Warning: It is almost never a good idea to use user names in"
+.Pa hosts.equiv .
+Beware that it really means that the named user(s) can log in as
+.Em anybody ,
+which includes bin, daemon, adm, and other accounts that own critical
+binaries and directories. Using a user name practically grants the
+user root access. The only valid use for user names that I can think
+of is in negative entries.
+.Pp
+Note that this warning also applies to rsh/rlogin.
+.It Pa /etc/shosts.equiv
+This is processed exactly as
+.Pa /etc/hosts.equiv .
+However, this file may be useful in environments that want to run both
+rsh/rlogin and ssh.
+.It Pa $HOME/.ssh/environment
+This file is read into the environment at login (if it exists). It
+can only contain empty lines, comment lines (that start with
+.Ql # ) ,
+and assignment lines of the form name=value. The file should be writable
+only by the user; it need not be readable by anyone else.
+.It Pa $HOME/.ssh/rc
+If this file exists, it is run with /bin/sh after reading the
+environment files but before starting the user's shell or command. If
+X11 spoofing is in use, this will receive the "proto cookie" pair in
+standard input (and
+.Ev DISPLAY
+in environment). This must call
+.Xr xauth 1
+in that case.
+.Pp
+The primary purpose of this file is to run any initialization routines
+which may be needed before the user's home directory becomes
+accessible; AFS is a particular example of such an environment.
+.Pp
+This file will probably contain some initialization code followed by
+something similar to: "if read proto cookie; then echo add $DISPLAY
+$proto $cookie | xauth -q -; fi".
+.Pp
+If this file does not exist,
+.Pa /etc/sshrc
+is run, and if that
+does not exist either, xauth is used to store the cookie.
+.Pp
+This file should be writable only by the user, and need not be
+readable by anyone else.
+.It Pa /etc/sshrc
+Like
+.Pa $HOME/.ssh/rc .
+This can be used to specify
+machine-specific login-time initializations globally. This file
+should be writable only by root, and should be world-readable.
+.Sh AUTHOR
+Tatu Ylonen <ylo@cs.hut.fi>
+.Pp
+Information about new releases, mailing lists, and other related
+issues can be found from the SSH WWW home page:
+.Pp
+.Dl http://www.cs.hut.fi/ssh.
+.Pp
+OpenSSH
+is a derivative of the original (free) ssh 1.2.12 release, but with bugs
+removed and newer features re-added. Rapidly after the 1.2.12 release,
+newer versions bore successively more restrictive licenses. This version
+of OpenSSH
+.Bl -bullet
+.It
+has all components of a restrictive nature (ie. patents, see
+.Xr ssl 8 )
+directly removed from the source code; any licensed or patented components
+are chosen from
+external libraries.
+.It
+has been updated to support ssh protocol 1.5.
+.It
+contains added support for
+.Xr kerberos 8
+authentication and ticket passing.
+.It
+supports one-time password authentication with
+.Xr skey 1 .
+.El
+.Pp
+The libraries described in
+.Xr ssl 8
+are required for proper operation.
+.Sh SEE ALSO
+.Xr rlogin 1 ,
+.Xr rsh 1 ,
+.Xr scp 1 ,
+.Xr ssh 1 ,
+.Xr ssh-add 1 ,
+.Xr ssh-agent 1 ,
+.Xr ssh-keygen 1 ,
+.Xr ssl 8