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rpc.yppasswdd(8)

NAME

     rpc.yppasswdd -- server for updating NIS passwords

SYNOPSIS

     rpc.yppasswdd [-t master.passwd template file] [-d default domain]
		   [-p path] [-s] [-f] [-a] [-m] [-i] [-v] [-u] [-h]

DESCRIPTION

     The rpc.yppasswdd utility allows users to change their NIS passwords and
     certain other information using the yppasswd(1) and ypchpass(1) commands.
     The rpc.yppasswdd utility is an RPC-based server that accepts incoming
     password change requests, authenticates them, places the updated informa-
     tion in the /var/yp/master.passwd template file and then updates the NIS
     master.passwd and passwd maps.

     The rpc.yppasswdd utility allows a normal NIS user to change his or her
     NIS password, full name (also known as 'GECOS' field) or shell.  These
     updates are typically done using the yppasswd(1), ypchfn(1), ypchsh(1),
     or ypchpass(1) commands.  (Some administrators don't want users to be
     able to change their full name information or shells; the server can be
     invoked with option flags that disallow such changes.)  When the server
     receives an update request, it compares the address of the client making
     the request against the securenets rules outlined in /var/yp/securenets.
     (See the ypserv(8) manual page for more information on securenets; the
     rpc.yppasswdd utility uses the same access control mechanism as
     ypserv(8).)

     The server then checks the 'old' password supplied by the user to make
     sure it's valid, then performs some sanity checks on the updated informa-
     tion (these include checking for embedded control characters, colons or
     invalid shells).  Once it is satisfied that the update request is valid,
     the server modifies the template password file (the default is
     /var/yp/master.passwd) and then runs the /usr/libexec/yppwupdate script
     to rebuild the NIS maps.  (This script has two arguments passed to it:
     the absolute pathname of the password template that was modified and the
     name of the domain that is to be updated.	These in turn are passed to
     /var/yp/Makefile).

     The FreeBSD version of rpc.yppasswdd also allows the super-user on the
     NIS master server to perform more sophisticated updates on the NIS passwd
     maps.  The super-user can modify any field in any user's master.passwd
     entry in any domain, and can do so without knowing the user's existing
     NIS password (when the server receives a request from the super-user, the
     password authentication check is bypassed).  Furthermore, if the server
     is invoked with the -a flag, the super-user can even add new entries to
     the maps using ypchpass(1).  Again, this only applies to the super-user
     on the NIS master server: none of these special functions can be per-
     formed over the network.

     The rpc.yppasswdd utility can only be run on a machine that is an NIS
     master server.

OPTIONS

     The following options are available:

     -t master.passwd template file
	     By default, rpc.yppasswdd assumes that the template file used to

     -d domain
	     The rpc.yppasswdd utility can support multiple domains, however
	     it must choose one domain as a default.  It will try to use the
	     system default domain name as set by the domainname(1) command
	     for this default.	However, if the system domain name is not set,
	     a default domain must be specified on the command line.  If the
	     system default domain is set, then this option can be used to
	     override it.

     -p path
	     This option can be used to override the default path to the loca-
	     tion of the NIS map databases.  The compiled-in default path is
	     /var/yp.

     -s      Disallow changing of shell information.

     -f      Disallow changing of full name ('GECOS') information.

     -a      Allow additions to be made to the NIS passwd databases.  The
	     super-user on the NIS master server is permitted to use the
	     ypchpass(1) command to perform unrestricted modifications to any
	     field in a user's master.passwd map entry.  When rpc.yppasswdd is
	     started with this flag, it will also allow the super-user to add
	     new records to the NIS passwd maps, just as is possible when
	     using chpass(1) to modify the local password database.

     -m      Turn on multi-domain mode.  Even though ypserv(8) can handle sev-
	     eral simultaneous domains, most implementations of rpc.yppasswdd
	     can only operate on a single NIS domain, which is generally the
	     same as the system default domain of the NIS master server.  The
	     FreeBSD rpc.yppasswdd attempts to overcome this problem in spite
	     of the inherent limitations of the yppasswd protocol, which does
	     not allow for a domain argument in client requests.  In multi-
	     domain mode, rpc.yppasswdd will search through all the passwd
	     maps of all the domains it can find under /var/yp until it finds
	     an entry that matches the user information specified in a given
	     update request.  (Matches are determined by checking the user-
	     name, UID and GID fields.)  The matched entry and corresponding
	     domain are then used for the update.

	     Note that in order for multi-domain mode to work, there have to
	     be separate template files for each domain.  For example, if a
	     server supports three domains, foo, bar, and baz, there should be
	     three separate master.passwd template files called
	     /var/yp/foo/master.passwd, /var/yp/bar/master.passwd, and
	     /var/yp/baz/master.passwd.  If foo happens to be the system
	     default domain, then its template file can be either
	     /var/yp/foo/master.passwd or /var/yp/master.passwd.  The server
	     will check for the latter file first and then use the former if
	     it can't find it.

	     Multi-domain mode is off by default since it can fail if there
	     are duplicate or near-duplicate user entries in different
	     domains.  The server will abort an update request if it finds
	     more than one user entry that matches its search criteria.  Even
	     so, paranoid administrators may wish to leave multi-domain mode
	     disabled.
	     time to a few seconds.

     -v      Turn on verbose logging mode.  The server normally only logs mes-
	     sages using the syslog(3) facility when it encounters an error
	     condition, or when processing updates for the super-user on the
	     NIS master server.  Running the server with the -v flag will
	     cause it to log informational messages for all updates.

     -u      Many commercial yppasswd(1) clients do not use a reserved port
	     when sending requests to rpc.yppasswdd.  This is either because
	     the yppasswd(1) program is not installed set-uid root, or because
	     the RPC implementation does not place any emphasis on binding to
	     reserved ports when establishing client connections for the
	     super-user.  By default, rpc.yppasswdd expects to receive
	     requests from clients using reserved ports; requests received
	     from non-privileged ports are rejected.  Unfortunately, this
	     behavior prevents any client systems that to not use privileged
	     ports from successfully submitting password updates.  Specifying
	     the -u flag to rpc.yppasswdd disables the privileged port check
	     so that it will work with yppasswd(1) clients that don't use
	     privileged ports.	This reduces security to a certain small
	     degree, but it might be necessary in cases where it is not possi-
	     ble to change the client behavior.

     -h      Display the list of flags and options understood by
	     rpc.yppasswdd.

FILES

     /usr/libexec/yppwupdate	       The script invoked by rpc.yppasswdd to
				       update and push the NIS maps after an
				       update.
     /var/yp/master.passwd	       The template password file for the
				       default domain.
     /var/yp/[domainname]/[maps]       The NIS maps for a particular NIS
				       domain.
     /var/yp/[domainname]/master.passwd
				       The template password file(s) for non-
				       default domains (used only in multi-
				       domain mode).

SEE ALSO

     yp(8), yppush(8), ypserv(8), ypxfr(8)

BUGS

     As listed in the yppasswd.x protocol definition, the YPPASSWDPROC_UPDATE
     procedure takes two arguments: a V7-style passwd structure containing
     updated user information and the user's existing unencrypted (cleartext)
     password.	Since rpc.yppasswdd is supposed to handle update requests from
     remote NIS client machines, this means that yppasswd(1) and similar
     client programs will in fact be transmitting users' cleartext passwords
     over the network.

     This is not a problem for password updates since the plaintext password
     sent with the update will no longer be valid once the new encrypted pass-
     word is put into place, but if the user is only updating his or her
     'GECOS' information or shell, then the cleartext password sent with the
     update will still be valid once the update is completed.  If the network
     is insecure, this cleartext password could be intercepted and used to

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