HardenedBSD/usr.bin/chpass/chpass.1

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.Dd May 25, 2021
.Dt CHPASS 1
.Os
.Sh NAME
.Nm chpass ,
.Nm chfn ,
.Nm chsh ,
.Nm ypchpass ,
.Nm ypchfn ,
.Nm ypchsh
.Nd add or change user database information
.Sh SYNOPSIS
.Nm chpass
.Op Fl a Ar list
.Op Fl e Ar expiretime
.Op Fl p Ar encpass
.Op Fl s Ar newshell
.Op user
.Nm ypchpass
.Op Fl loy
.Op Fl a Ar list
.Op Fl d Ar domain
.Op Fl e Ar expiretime
.Op Fl h Ar host
.Op Fl p Ar encpass
.Op Fl s Ar newshell
.Op user
.Sh DESCRIPTION
The
.Nm
utility
allows editing of the user database information associated
with
.Ar user
or, by default, the current user.
.Pp
The
.Nm chfn ,
.Nm chsh ,
.Nm ypchpass ,
.Nm ypchfn
and
.Nm ypchsh
utilities behave identically to
.Nm .
(There is only one program.)
.Pp
The information is formatted and supplied to an editor for changes.
.Pp
Only the information that the user is allowed to change is displayed.
.Pp
The options are as follows:
.Bl -tag -width "-e expiretime"
.It Fl a Ar list
The super-user is allowed to directly supply a user database
entry, in the format specified by
.Xr passwd 5 ,
as an argument.
This argument must be a colon
.Pq Dq \&:
separated list of all the
user database fields, although they may be empty.
.It Fl e Ar expiretime
Change the account expire time.
This option is used to set the expire time
from a script as if it was done in the interactive editor.
.It Fl p Ar encpass
The super-user is allowed to directly supply an encrypted password field,
in the format used by
.Xr crypt 3 ,
as an argument.
.It Fl s Ar newshell
Attempt to change the user's shell to
.Ar newshell .
.El
.Pp
Possible display items are as follows:
.Pp
.Bl -tag -width "Other Information:" -compact -offset indent
.It Login:
user's login name
.It Password:
user's encrypted password
.It Uid:
user's login
.It Gid:
user's login group
.It Class:
user's general classification
.It Change:
password change time
.It Expire:
account expiration time
.It Full Name:
user's real name
.It Office Location:
user's office location (1)
.It Office Phone:
user's office phone (1)
.It Home Phone:
user's home phone (1)
.It Other Information:
any locally defined parameters for user (1)
.It Home Directory:
user's home directory
.It Shell:
user's login shell
.Pp
.It NOTE(1) -
In the actual master.passwd file, these fields are comma-delimited
fields embedded in the FullName field.
.El
.Pp
The
.Ar login
field is the user name used to access the computer account.
.Pp
The
.Ar password
field contains the encrypted form of the user's password.
.Pp
The
.Ar uid
field is the number associated with the
.Ar login
field.
Both of these fields should be unique across the system (and often
across a group of systems) as they control file access.
.Pp
While it is possible to have multiple entries with identical login names
and/or identical user id's, it is usually a mistake to do so.
Routines
that manipulate these files will often return only one of the multiple
entries, and that one by random selection.
.Pp
The
.Ar gid
field is the group that the user will be placed in at login.
Since
.Bx
supports multiple groups (see
.Xr groups 1 )
this field currently has little special meaning.
This field may be filled in with either a number or a group name (see
.Xr group 5 ) .
.Pp
The
.Ar class
field references class descriptions in
.Pa /etc/login.conf
and is typically used to initialize the user's system resource limits
when they login.
.Pp
The
.Ar change
field is the date by which the password must be changed.
.Pp
The
.Ar expire
field is the date on which the account expires.
.Pp
Both the
.Ar change
and
.Ar expire
fields should be entered in the form
.Dq month day year
where
.Ar month
is the month name (the first three characters are sufficient),
.Ar day
is the day of the month, and
.Ar year
is the year.
.Pp
Five fields are available for storing the user's
.Ar full name , office location ,
.Ar work
and
.Ar home telephone
numbers and finally
.Ar other information
which is a single comma delimited string to represent any additional
gecos fields (typically used for site specific user information).
Note that
.Xr finger 1
will display the office location and office phone together under the
heading
.Ar Office\&: .
.Pp
The user's
.Ar home directory
is the full
.Ux
path name where the user
will be placed at login.
.Pp
The
.Ar shell
field is the command interpreter the user prefers.
If the
.Ar shell
field is empty, the Bourne shell,
.Pa /bin/sh ,
is assumed.
When altering a login shell, and not the super-user, the user
may not change from a non-standard shell or to a non-standard
shell.
Non-standard is defined as a shell not found in
.Pa /etc/shells .
.Pp
Once the information has been verified,
.Nm
uses
.Xr pwd_mkdb 8
to update the user database.
.Sh ENVIRONMENT
The
.Xr vi 1
editor will be used unless the environment variable
.Ev EDITOR
is set to
an alternate editor.
When the editor terminates, the information is re-read and used to
update the user database itself.
Only the user, or the super-user, may edit the information associated
with the user.
.Pp
See
.Xr pwd_mkdb 8
for an explanation of the impact of setting the
.Ev PW_SCAN_BIG_IDS
environment variable.
.Sh NIS INTERACTION
The
.Nm
utility can also be used in conjunction with NIS, however some restrictions
apply.
Currently,
.Nm
can only make changes to the NIS passwd maps through
.Xr rpc.yppasswdd 8 ,
which normally only permits changes to a user's password, shell and GECOS
fields.
Except when invoked by the super-user on the NIS master server,
.Nm
(and, similarly,
.Xr passwd 1 )
cannot use the
.Xr rpc.yppasswdd 8
server to change other user information or
add new records to the NIS passwd maps.
Furthermore,
.Xr rpc.yppasswdd 8
requires password authentication before it will make any
changes.
The only user allowed to submit changes without supplying
a password is the super-user on the NIS master server; all other users,
including those with root privileges on NIS clients (and NIS slave
servers) must enter a password.
(The super-user on the NIS master is allowed to bypass these restrictions
largely for convenience: a user with root access
to the NIS master server already has the privileges required to make
updates to the NIS maps, but editing the map source files by hand can
be cumbersome.
.Pp
Note: these exceptions only apply when the NIS master server is a
.Fx
system).
.Pp
Consequently, except where noted, the following restrictions apply when
.Nm
is used with NIS:
.Bl -enum -offset indent
.It
.Em "Only the shell and GECOS information may be changed" .
All other
fields are restricted, even when
.Nm
is invoked by the super-user.
While support for
changing other fields could be added, this would lead to
compatibility problems with other NIS-capable systems.
Even though the super-user may supply data for other fields
while editing an entry, the extra information (other than the
password \(em see below) will be silently discarded.
.Pp
Exception: the super-user on the NIS master server is permitted to
change any field.
.It
.Em "Password authentication is required" .
The
.Nm
utility will prompt for the user's NIS password before effecting
any changes.
If the password is invalid, all changes will be
discarded.
.Pp
Exception: the super-user on the NIS master server is allowed to
submit changes without supplying a password.
(The super-user may
choose to turn off this feature using the
.Fl o
flag, described below.)
.It
.Em "Adding new records to the local password database is discouraged" .
The
.Nm
utility will allow the administrator to add new records to the
local password database while NIS is enabled, but this can lead to
some confusion since the new records are appended to the end of
the master password file, usually after the special NIS '+' entries.
The administrator should use
.Xr vipw 8
to modify the local password
file when NIS is running.
.Pp
The super-user on the NIS master server is permitted to add new records
to the NIS password maps, provided the
.Xr rpc.yppasswdd 8
server has been started with the
.Fl a
flag to permitted additions (it refuses them by default).
The
.Nm
utility tries to update the local password database by default; to update the
NIS maps instead, invoke chpass with the
.Fl y
flag.
.It
.Em "Password changes are not permitted".
Users should use
.Xr passwd 1
or
.Xr yppasswd 1
to change their NIS passwords.
The super-user is allowed to specify
a new password (even though the
.Dq Password:
field does not show
up in the editor template, the super-user may add it back by hand),
but even the super-user must supply the user's original password
otherwise
.Xr rpc.yppasswdd 8
will refuse to update the NIS maps.
.Pp
Exception: the super-user on the NIS master server is permitted to
change a user's NIS password with
.Nm .
.El
.Pp
There are also a few extra option flags that are available when
.Nm
is compiled with NIS support:
.Bl -tag -width "-d domain"
.It Fl d Ar domain
Specify a particular NIS domain.
The
.Nm
utility uses the system domain name by default, as set by the
.Xr domainname 1
utility.
The
.Fl d
option can be used to override a default, or to specify a domain
when the system domain name is not set.
.It Fl h Ar host
Specify the name or address of an NIS server to query.
Normally,
.Nm
will communicate with the NIS master host specified in the
.Pa master.passwd
or
.Pa passwd
maps.
On hosts that have not been configured as NIS clients, there is
no way for the program to determine this information unless the user
provides the hostname of a server.
Note that the specified hostname need
not be that of the NIS master server; the name of any server, master or
slave, in a given NIS domain will do.
.Pp
When using the
.Fl d
option, the hostname defaults to
.Dq localhost .
The
.Fl h
option can be used in conjunction with the
.Fl d
option, in which case the user-specified hostname will override
the default.
.It Fl l
Force
.Nm
to modify the local copy of a user's password
information in the event that a user exists in both
the local and NIS databases.
.It Fl o
Force the use of RPC-based updates when communicating with
.Xr rpc.yppasswdd 8
.Pq Dq old-mode .
When invoked by the super-user on the NIS master server,
.Nm
allows unrestricted changes to the NIS passwd maps using dedicated,
non-RPC-based mechanism (in this case, a
.Ux
domain socket).
The
.Fl o
flag can be used to force
.Nm
to use the standard update mechanism instead.
This option is provided
mainly for testing purposes.
.It Fl y
Opposite effect of
.Fl l .
This flag is largely redundant since
.Nm
operates on NIS entries by default if NIS is enabled.
.El
.Sh FILES
.Bl -tag -width /etc/master.passwd -compact
.It Pa /etc/master.passwd
the user database
.It Pa /etc/passwd
a Version 7 format password file
.It Pa /etc/pw.XXXXXX
temporary file
.It Pa /etc/shells
the list of approved shells
.El
.Sh EXAMPLES
Change the shell of the current user to
.Ql /usr/local/bin/zsh :
.Bd -literal -offset indent
chsh -s /usr/local/bin/zsh
.Ed
.Sh SEE ALSO
.Xr finger 1 ,
.Xr login 1 ,
.Xr passwd 1 ,
.Xr getusershell 3 ,
.Xr login.conf 5 ,
.Xr passwd 5 ,
.Xr pw 8 ,
.Xr pwd_mkdb 8 ,
.Xr vipw 8
.Rs
.%A Robert Morris
.%A Ken Thompson
.%T "UNIX Password security"
.Re
.Sh HISTORY
The
.Nm
utility appeared in
.Bx 4.3 Reno .
.Sh BUGS
User information should (and eventually will) be stored elsewhere.