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Path: utzoo!utgpu!!mailrus!!
From: bos...@OKEEFFE.BERKELEY.EDU (Keith Bostic)
Newsgroups: comp.bugs.4bsd.ucb-fixes
Subject: V1.81 (Shadow passwords)
Message-ID: <8905091915.AA18887@okeeffe.Berkeley.EDU>
Date: 9 May 89 19:15:04 GMT
Sender: dae...@ucbvax.BERKELEY.EDU
Organization: University of California at Berkeley
Lines: 70

Subject: Shadow passwords
Index: lib 4.3BSD-tahoe

	     A shadow  password implementation is now available from
	Berkeley,  and  will  be  a  standard  part of the next 4BSD
	distribution.  The following describes the package  in  more
	detail.  To get copies of the package, send electronic  mail
	to,  or  call the BSD
	distribution office at 415-642-7780.
	     In the current BSD  system, there  are  three  password
	files:  /etc/passwd,  /etc/passwd.pag,  and /etc/passwd.dir.
	The first is the password file as  described  in  passwd(5);
	the  others  are  files  containing  an ndbm(3) style hashed
	database version of /etc/passwd.
	     In the new  system,  there  are  four  password  files:
	/etc/passwd,    /etc/master.passwd,   /etc/passwd.pag,   and
	/etc/passwd.dir.  The first is exactly as it has always been
	with  the  exception  that  the encrypted password field has
	been replaced with a single asterisk.  The next three  files
	have  much  the  same  relationship  as  the original model;
	master.passwd is the new password file, and  passwd.pag  and
	passwd.dir  comprise  the  ndbm version.  The one difference
	between the contents of master.passwd and  the  contents  of
	its  ndbm files is that only master.passwd has the encrypted
	form of the password.  The ndbm  files  have,  instead,  its
	offset  in  master.passwd.  Note, the file /etc/passwd is no
	longer used for anything, it is simply  left  in  place  for
	backward  compatibility  with  shell  scripts.
	     The model we are  using  assumes  that  standard,  non-
	privileged  programs  do  not  need to look at the encrypted
	form of  the  password.   Therefore,  we  have  altered  the
	getpwent(3) routines to read the standard data from the ndbm
	files, and only attempt to read  and  return  the  encrypted
	password  if  the  process  is running as super-user.  Obvi-
	ously, master.passwd is read/writable only by the super-user
	and  and  the ndbm files are readable by anyone and writable
	only by the super-user.
	     We also added three new fields to the password file;  a
	``change''  field,  for password aging, an ``expire'' field,
	for account expiration, and a ``class'' field for everything
	else.   The  first two are implemented in login(1), and are,
	respectively,  the  date  by  which  the  password  must  be
	changed,  and  the date when the account expires.  The third
	will be part of the next  4BSD  release,  but  is  currently
	unimplemented.   It will be a ``pointer'' to a termcap style
	database that may be used to store  site-dependent  informa-
	tion  about a user, from when the user may be allowed to log
	into the system, to how often the user is required to change
	their password.
	     The include file, pwd.h, has changed  in  fairly  major
	ways.   We've  deleted  the two unused fields, ``pw_quota'',
	and ``pw_comment'', and replaced them with ``pw_change'' and
	``pw_class'',    respectively.    The   other   new   field,
	``pw_expire'', has been added at the end of the structure.
	     The only known problem with the current  implementation
	of  password aging is that there is no ``reset'' -- when the
	user changes his or her password it  essentially  shuts  off
	password  aging  for  that  user.   To  reenable  aging,  an
	administrator will have to use vipw(8) or chpass(1) to  pro-
	vide  a new password timeout.  We expect to remedy this with
	the new ``class'' database, where one of the provided fields
	will  be  a value specifying how often the password needs to
	be updated.  Once this is in place,  passwd(1)  will  simply
	reset  the password timeout value each time the user changes
	their password.
	     Two programs have been deleted by this package, chfn(1)
	and  chsh(1).  They are replaced by the much more comprehen-
	sive program chpass(1).  The other programs affected by this
	package behave much like they have always behaved.

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