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RPC.YPPASSWDD(8)        FreeBSD System Manager's Manual       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 performed
     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
             generates the master.passwd and passwd maps for the default
             domain is called /var/yp/master.passwd.  This default can be
             overridden by specifying an alternate file name with the -t flag.

             Note: if the template file specified with this flag is
             /etc/master.passwd, rpc.yppasswdd will also automatically invoke
             pwd_mkdb(8) to rebuild the local password databases in addition
             to the NIS maps.

     -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.

     -i      If rpc.yppasswdd is invoked with this flag, it will perform map
             updates in place.  This means that instead of just modifying the
             password template file and starting a map update, the server will
             modify the map databases directly.  This is useful when the pass-
             word maps are large: if, for example, the password database has
             tens of thousands of entries, it can take several minutes for a
             map update to complete.  Updating the maps in place reduces this
             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
     gain unauthorized access to the user's account.

AUTHORS
     Bill Paul <wpaul@ctr.columbia.edu>

FreeBSD 4.10                   February 8, 1996                   FreeBSD 4.10

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | FILES | SEE ALSO | BUGS | AUTHORS

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