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diff --git a/crypto/openssh/sshd.8 b/crypto/openssh/sshd.8 deleted file mode 100644 index 3fb255af05f4e..0000000000000 --- a/crypto/openssh/sshd.8 +++ /dev/null @@ -1,987 +0,0 @@ -.\" -*- 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 1.51 2000/05/08 17:42:31 hugh Exp $ -.\" -.Dd September 25, 1999 -.Dt SSHD 8 -.Os -.Sh NAME -.Nm sshd -.Nd secure shell daemon -.Sh SYNOPSIS -.Nm sshd -.Op Fl diqQ46 -.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 -.Op Fl V Ar client_protocol_id -.Sh DESCRIPTION -.Nm -(Secure Shell Daemon) is the daemon program for -.Xr ssh 1 . -Together these programs replace rlogin and rsh, 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. -This implementation of -.Nm -supports both SSH protocol version 1 and 2 simultaneously. -.Nm -works as follows. -.Pp -.Ss SSH protocol version 1 -.Pp -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 responds with its public -host and server keys. -The client compares the -RSA 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 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 or 3DES, with 3DES -being 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 the machine). -.Pp -.Ss SSH protocol version 2 -.Pp -Version 2 works similar: -Each host has a host-specific DSA key used to identify the host. -However, when the daemon starts, it does not generate a server key. -Forward security is provided through a Diffie-Hellman key agreement. -This key agreement results in a shared session key. -The rest of the session is encrypted -using a symmetric cipher, currently -Blowfish, 3DES or CAST128 in CBC mode or Arcfour. -The client selects the encryption algorithm -to use from those offered by the server. -Additionally, session integrity is provided -through a cryptographic message authentication code -(hmac-sha1 or hmac-md5). -.Pp -Protocol version 2 provides a public key based -user authentication method (DSAAuthentication) -and conventional password authentication. -.Pp -.Ss Command execution and data forwarding -.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 -.Nm -rereads its configuration file when it receives a hangup signal, -.Dv SIGHUP . -.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 RSA 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. -.It Fl V Ar client_protocol_id -SSH2 compatibility mode. -When this option is specified -.Nm -assumes the client has sent the supplied version string -and skips the -Protocol Version Identification Exchange. -.It Fl 4 -Forces -.Nm -to use IPv4 addresses only. -.It Fl 6 -Forces -.Nm -to use IPv6 addresses only. -.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 Ciphers -Specifies the ciphers allowed for protocol version 2. -Multiple ciphers must be comma-separated. -The default is -.Dq 3des-cbc,blowfish-cbc,arcfour,cast128-cbc . -.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 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. -.It Cm DSAAuthentication -Specifies whether DSA authentication is allowed. -The default is -.Dq yes . -Note that this option applies to protocol version 2 only. -.It Cm GatewayPorts -Specifies whether remote hosts are allowed to connect to ports -forwarded for the client. -The argument must be -.Dq yes -or -.Dq no . -The default is -.Dq no . -.It Cm HostDsaKey -Specifies the file containing the private DSA host key (default -.Pa /etc/ssh_host_dsa_key ) -used by SSH protocol 2.0. -Note that -.Nm -disables protocol 2.0 if this file is group/world-accessible. -.It Cm HostKey -Specifies the file containing the private RSA host key (default -.Pa /etc/ssh_host_key ) -used by SSH protocols 1.3 and 1.5. -Note that -.Nm -disables protocols 1.3 and 1.5 if this file is group/world-accessible. -.It Cm IgnoreRhosts -Specifies that -.Pa .rhosts -and -.Pa .shosts -files will not be used in authentication. -.Pa /etc/hosts.equiv -and -.Pa /etc/shosts.equiv -are still used. -The default is -.Dq yes . -.It Cm IgnoreUserKnownHosts -Specifies whether -.Nm -should ignore the user's -.Pa $HOME/.ssh/known_hosts -during -.Cm RhostsRSAAuthentication . -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 sent, -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. -Multiple options of this type are permitted. -Additionally, the -.Cm Ports -options must precede this option. -.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 LogLevel -Gives the verbosity level that is used when logging messages from -.Nm sshd . -The possible values are: -QUIET, FATAL, ERROR, INFO, VERBOSE and DEBUG. -The default is INFO. -Logging with level DEBUG violates the privacy of users -and is not recommended. -.It Cm PasswordAuthentication -Specifies whether password authentication is allowed. -The default is -.Dq yes . -Note that this option applies to both protocol version 1 and 2. -.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 no . -.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 PidFile -Specifies the file that contains the process identifier of the -.Nm -daemon. -The default is -.Pa /var/run/sshd.pid . -.It Cm Port -Specifies the port number that -.Nm -listens on. -The default is 22. -Multiple options of this type are permitted. -.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 Protocol -Specifies the protocol versions -.Nm -should support. -The possible values are -.Dq 1 -and -.Dq 2 . -Multiple versions must be comma-separated. -The default is -.Dq 1 . -.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 no . -.It Cm RSAAuthentication -Specifies whether pure RSA authentication is allowed. -The default is -.Dq yes . -Note that this option applies to protocol version 1 only. -.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 X11DisplayOffset -Specifies the first display number available for -.Nm sshd Ns 's -X11 forwarding. -This prevents -.Nm -from interfering with real X11 servers. -The default is 10. -.It Cm X11Forwarding -Specifies whether X11 forwarding is permitted. -The default is -.Dq no . -Note that disabling X11 forwarding does not improve security in any -way, as users can always install their own forwarders. -.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 in SSH protocols 1.3 and 1.5 -Similarly, the -.Pa $HOME/.ssh/authorized_keys2 -file lists the DSA keys that are -permitted for DSA authentication in SSH protocol 2.0. -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 -.Pf ( Ql * -and -.Ql ? -serve as wildcards). -The list may also contain -patterns negated by prefixing them with -.Ql ! ; -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. -Note that the client may specify TCP/IP and/or X11 -forwarding 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 , -.Pa /etc/ssh_known_hosts2 , -.Pa $HOME/.ssh/known_hosts , -and -.Pa $HOME/.ssh/known_hosts2 -files contain host public keys for all known hosts. -The global file should -be prepared by the administrator (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 RSA 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. -Users will place the contents of their -.Pa identity.pub -files into this file, as described in -.Xr ssh-keygen 1 . -.It Pa $HOME/.ssh/authorized_keys2 -Lists the DSA keys that can be used to log into the user's account. -This file must be readable by root (which may on some machines imply -it being world-readable if the user's home directory resides on an NFS -volume). -It is recommended that it not be accessible by others. -The format of this file is described above. -Users will place the contents of their -.Pa id_dsa.pub -files into this file, as described in -.Xr ssh-keygen 1 . -.It Pa "/etc/ssh_known_hosts" and "$HOME/.ssh/known_hosts" -These files are consulted when using rhosts with RSA host -authentication to check the public key of the host. -The key must be listed in one of these files to be accepted. -The client uses the same files -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 -OpenSSH -is a derivative of the original (free) ssh 1.2.12 release by Tatu Ylonen, -but with bugs removed and newer features re-added. -Rapidly after the -1.2.12 release, newer versions of the original ssh bore successively -more restrictive licenses, and thus demand for a free version was born. -.Pp -This version of OpenSSH -.Bl -bullet -.It -has all components of a restrictive nature (i.e., 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 and 2, making it compatible with -all other SSH clients and servers. -.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. -.Pp -OpenSSH has been created by Aaron Campbell, Bob Beck, Markus Friedl, -Niels Provos, Theo de Raadt, and Dug Song. -.Pp -The support for SSH protocol 2 was written by Markus Friedl. -.Sh SEE ALSO -.Xr scp 1 , -.Xr ssh 1 , -.Xr ssh-add 1 , -.Xr ssh-agent 1 , -.Xr ssh-keygen 1 , -.Xr ssl 8 , -.Xr rlogin 1 , -.Xr rsh 1 |