in.rshd(1M)						  System Administration Commands					       in.rshd(1M)

NAME

       in.rshd, rshd - remote shell server

SYNOPSIS

       in.rshd [-k5eciU] [-s tos] [-S keytab] [-M realm] [-L env_var] host.port

DESCRIPTION

       in.rshd	is  the server for the rsh(1) program. The server provides remote execution facilities with authentication based on Kerberos V5 or
       privileged port numbers.

       in.rshd is invoked by inetd(1M) each time a shell service is requested.

       When Kerberos V5 authentication is required (this can be set with Kerberos-specific options listed below), the following protocol is initi-
       ated:

       1.  Check Kerberos V5 authentication.

       2.  Check authorization according to rules in krb5_auth_rules(5).

       3.  A  null byte is returned on the initial socket and the command line is passed to the normal login shell of the user. (The PATH variable
	   is set to /usr/bin.) The shell inherits the network connections established by in.rshd.

       If Kerberos V5 authentication is not enabled, then in.rshd executes the following protocol:

       1.  The server checks the client's source port. If the port is not in the range 512-1023, the server aborts the connection.   The  client's
	   host address (in hex) and port number (in decimal) are the arguments passed to in.rshd.

       2.  The server reads characters from the socket up to a null ( ) byte. The resultant string is interpreted as an ASCII number, base 10.

       3.  If  the  number received in step 2 is non-zero, it is interpreted as the port number of a secondary stream to be used for the stderr. A
	   second connection is then created to the specified port on the client's machine. The source port of this second connection is  also	in
	   the range 512-1023.

       4.  A  null-terminated  user  name  of  at most 16 characters is retrieved on the initial socket. This user name is interpreted as the user
	   identity on the client's machine.

       5.  A null terminated user name of at most 16 characters is retrieved on the initial socket. This user name is interpreted as a user  iden-
	   tity to use on the server's machine.

       6.  A  null  terminated	command  to  be passed to a shell is retrieved on the initial socket.  The length of the command is limited by the
	   upper bound on the size of the system's argument list.

       7.  in.rshd then validates the user according to the following steps. The remote user name is looked up in the password file and a chdir is
	   performed  to  the  user's  home directory. If the lookup fails, the connection is terminated. If the chdir fails, it does a chdir to /
	   (root). If the user is not the superuser, (user ID 0), and if the pam_rhosts_auth  PAM module is  configured  for  authentication,  the
	   file  /etc/hosts.equiv is consulted for a list of hosts considered "equivalent". If the client's host name is present in this file, the
	   authentication is considered successful. See the SECURITY section  below for a discussion of  PAM authentication.

	   If the lookup fails, or the user is the superuser, then the file .rhosts in the home directory of the remote user is  checked  for  the
	   machine name and identity of the user on the client's machine. If this lookup fails, the connection is terminated

       8.
	   A  null byte is returned on the initial connection and the command line is passed to the normal login shell of the user. The PATH vari-
	   able is set to /usr/bin.  The shell inherits the network connections established by in.rshd.

OPTIONS

       The following options are supported:

       -5	       Same as -k, for backwards compatibility

       -c	       Requires Kerberos V5 clients to present a cryptographic checksum of initial connection information like	the  name  of  the
		       user  that  the client is  trying to access in the initial authenticator. This checksum provides additionl security by pre-
		       venting an attacker from changing the initial connection information. This option is mutually exclusive with the -i option.

       -e	       Requires the client to encrypt the connection.

       -i	       Ignores authenticator checksums if provided. This option ignores authenticator  checksums  presented  by  current  Kerberos
		       clients to protect initial connection  information. Option -i is the opposite of option -c.

       -k	       Allows  Kerberos  V5  authentication  with the .k5login access control file to be trusted. If this authentication system is
		       used by the client and the authorization check is passed, then the user is allowed to log in.

       -L env_var      List of environment variables that need to be saved and passed along.

       -M realm        Uses the indicated Kerberos V5 realm. By default, the daemon will determine its realm from the settings in the krb5.conf(4)
		       file.

       -s tos	       Sets the IP TOS option.

       -S keytab       Sets the KRB5 keytab file to use. The/etc/krb5/krb5.keytab file is used by default.

       -U	       Refuses connections that cannot be mapped to a name through the getnameinfo(3SOCKET) function.

USAGE

       rshd and in.rshd are IPv6-enabled. See ip6(7P). IPv6 is not currently supported with Kerberos V5 authentication.

       The Kerberized rshd service runs on port 544 (kshell). The corresponding FMRI entry is: :

       svc:/network/shell:kshell (rshd with kerberos (ipv4 only))

SECURITY

       in.rshd	uses  pam(3PAM)  for  authentication,  account	management,  and session management.  The PAM configuration policy, listed through
       /etc/pam.conf, specifies the modules to be used for in.rshd. Here is a partial pam.conf file with entries for the rsh command using  rhosts
       authentication, UNIX account management, and session management module.

       rsh	 auth	   required   pam_rhosts_auth.so.1

       rsh	 account   required   pam_unix_roles.so.1
       rsh	 session   required   pam_unix_projects.so.1
       rsh	 session   required   pam_unix_account.so.1

       rsh	 session   required   pam_unix_session.so.1

       If  there are no entries for the rsh service, then the entries for the "other" service are used. To maintain the authentication requirement
       for in.rshd, the rsh entry must always be configured with the pam_rhosts_auth.so.1 module.

       in.rshd can authenticate using Kerberos V5 authentication or pam(3PAM). For Kerberized rsh service, the appropriate  PAM  service  name	is
       "krsh".

FILES

       /etc/hosts.equiv

       $HOME/.k5login	       File containing Kerberos principals that are allowed access.

       /etc/krb5/krb5.conf     Kerberos configuration file.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWrcmds 		   |
       +-----------------------------+-----------------------------+

SEE ALSO

       rsh(1),	svcs(1), inetadm(1M), inetd(1M), svcadm(1M), pam(3PAM), getnameinfo(3SOCKET), hosts(4), krb5.conf(4), pam.conf(4),  attributes(5),
       environ(5),  krb5_auth_rules(5),  pam_authtok_check(5),	pam_authtok_get(5),   pam_authtok_store(5),   pam_dhkeys(5),   pam_passwd_auth(5),
       pam_rhosts_auth(5), pam_unix_account(5), pam_unix_auth(5), pam_unix_session(5), smf(5), ip6(7P)

DIAGNOSTICS

       The  following  diagnostic messages are returned on the connection associated with  stderr, after which any network connections are closed.
       An error is indicated by a leading byte with a value of 1 in step 8 above (0 is returned above upon successful completion of all the  steps
       prior to the command execution).

       locuser too long

	   The name of the user on the client's machine is longer than 16 characters.

       remuser too long

	   The name of the user on the remote machine is longer than 16 characters.

       command too long

	   The command line passed exceeds the size of the argument list (as configured into the system).

       Hostname for your address unknown.

	   No entry in the host name database existed for the client's machine.

       Login incorrect.

	   No password file entry for the user name existed.

       Permission denied.

	   The authentication procedure described above failed.

       Can't make pipe.

	   The pipe needed for the stderr was not created.

       Try again.

	   A fork by the server failed.

NOTES

       The authentication procedure used here assumes the integrity of each client machine and the connecting medium.  This is insecure, but it is
       useful in an "open" environment.

       A facility to allow all data exchanges to be encrypted should be present.

       The pam_unix(5) module is no longer supported. Similar functionality is provided  by  pam_authtok_check(5),  pam_authtok_get(5),  pam_auth-
       tok_store(5), pam_dhkeys(5), pam_passwd_auth(5), pam_unix_account(5), pam_unix_auth(5), and pam_unix_session(5).

       The in.rshd service is managed by the service management facility, smf(5), under the service identifier:

       svc:/network/shell:default

       Administrative actions on this service, such as enabling, disabling, or requesting restart, can be performed using svcadm(1M). Responsibil-
       ity for initiating and restarting this service is delegated to inetd(1M). Use inetadm(1M) to make configuration changes and to view config-
       uration information for this service. The service's status can be queried using the svcs(1) command.

SunOS 5.10							    4 Nov 2004							       in.rshd(1M)