path: root/lib/libc/gen/getpwnam.3

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.Dd $Mdocdate: August 21 2018 $
.Dt GETPWNAM 3
.Os
.Sh NAME
.Nm getpwnam ,
.Nm getpwuid ,
.Nm getpwnam_r ,
.Nm getpwuid_r ,
.Nm getpwnam_shadow ,
.Nm getpwuid_shadow ,
.Nm setpassent
.Nd password database operations
.Sh SYNOPSIS
.In pwd.h
.Ft struct passwd *
.Fn getpwnam "const char *login"
.Ft struct passwd *
.Fn getpwuid "uid_t uid"
.Ft int
.Fn getpwnam_r "const char *login" "struct passwd *pwstore" "char *buf" "size_t bufsize" "struct passwd **result"
.Ft int
.Fn getpwuid_r "uid_t uid" "struct passwd *pwstore" "char *buf" "size_t bufsize" "struct passwd **result"
.Ft struct passwd *
.Fn getpwnam_shadow "const char *login"
.Ft struct passwd *
.Fn getpwuid_shadow "uid_t uid"
.Ft int
.Fn setpassent "int stayopen"
.Sh DESCRIPTION
These functions operate on the password database file which is described in
.Xr passwd 5 .
Each entry in the database is defined by the structure
.Li struct passwd
found in the include file
.In pwd.h :
.Bd -literal -offset indent
struct passwd {
	char	*pw_name;	/* user name */
	char	*pw_passwd;	/* encrypted password */
	uid_t	pw_uid;		/* user uid */
	gid_t	pw_gid;		/* user gid */
	time_t	pw_change;	/* password change time */
	char	*pw_class;	/* user access class */
	char	*pw_gecos;	/* Honeywell login info */
	char	*pw_dir;	/* home directory */
	char	*pw_shell;	/* default shell */
	time_t	pw_expire;	/* account expiration */
};
.Ed
.Pp
The functions
.Fn getpwnam
and
.Fn getpwuid
search the password database for the given login name or user ID,
respectively, always returning the first one encountered.
.Pp
The
.Fn getpwnam_r
and
.Fn getpwuid_r
functions both update the passwd structure pointed to by
.Fa pwstore
and store a pointer to that structure at the location pointed to by
.Fa result .
The structure is filled with an entry from the password database with a
matching
.Fa name
or
.Fa uid .
Storage referenced by the passwd structure will be allocated from
the memory provided with the
.Fa buf
parameter, which is
.Fa bufsiz
characters in size.
The maximum size needed for this buffer can be determined with
.Fn sysconf _SC_GETPW_R_SIZE_MAX .
.Pp
.Fn setpassent
accomplishes two purposes.
First, it causes
.Xr getpwent 3
to
.Dq rewind
to the beginning of the database.
Additionally, if
.Fa stayopen
is non-zero, file descriptors are left open, significantly speeding
up subsequent accesses for the lookup routines.
These file descriptors can be closed by a call to
.Xr endpwent 3 .
.Pp
It is dangerous for long-running programs to keep the file descriptors
open as the database will become out of date if it is updated while the
program is running.
However the file descriptors are automatically closed when
.Xr execve 2
is called.
.Pp
These routines have been written to
.Dq shadow
the password file, that is,
allow only certain programs to have access to the encrypted password.
The default functions will not return the true encrypted password, but
instead only the string
.Ql * .
If the process which calls them has an effective UID of 0 or has the
.Dq _shadow
group in its group vector, and wishes to access the encrypted password,
it should use the
.Fn getpwnam_shadow
and
.Fn getpwuid_shadow
functions.
.Ss YP support
If YP is active, the functions
.Fn getpwnam
and
.Fn getpwnam_r
also use the
.Pa master.passwd.byname
YP map (if available) or the
.Pa passwd.byname
YP map; and the functions
.Fn getpwuid
and
.Fn getpwuid_r
also use the
.Pa master.passwd.byuid
YP map (if available) or the
.Pa passwd.byuid
YP map.
This is in addition to the passwd file,
and respects the order of both normal and YP
entries in the passwd file.
.Sh RETURN VALUES
The functions
.Fn getpwnam ,
.Fn getpwnam_shadow ,
.Fn getpwuid ,
and
.Fn getpwuid_shadow
return a pointer to a passwd structure if a match is found or a null
pointer if no match is found or an error occurs.
Subsequent calls to
.Fn getpwent ,
.Fn getpwnam ,
.Fn getpwnam_shadow ,
.Fn getpwuid
or
.Fn getpwuid_shadow
may invalidate the returned pointer or overwrite the contents
of the passwd structure it points to.
.Pp
The functions
.Fn getpwnam_r
and
.Fn getpwuid_r
update
.Fa result
to point to
.Fa pwstore
if a match is found or set it to
.Dv NULL
if no match is found or an error occurs.
They return 0 on success, even if no match is found,
or an error number if an error occurs; see
.Sx ERRORS .
.Pp
The
.Fn setpassent
function returns 0 on failure or 1 on success.
.Sh FILES
.Bl -tag -width /etc/master.passwd -compact
.It Pa /etc/pwd.db
insecure password database file
.It Pa /etc/spwd.db
secure password database file
.It Pa /etc/master.passwd
current password file
.It Pa /etc/passwd
legacy password file
.El
.Sh ERRORS
The
.Fn getpwnam_r
and
.Fn getpwuid_r
functions may fail if:
.Bl -tag -width Er
.It Bq Er ERANGE
The storage supplied via
.Fa buf
and
.Fa bufsize
is too small and cannot contain all the strings to be returned in
.Fa pwstore .
.El
.Pp
The
.Fn getpwnam ,
.Fn getpwnam_r ,
.Fn getpwuid ,
and
.Fn getpwuid_r
functions may also fail for any of the errors specified for
.Xr dbopen 3
and its
.Fn get
routine.
.Pp
If YP is active, they may also fail due to errors caused by the YP
subsystem.
.Sh SEE ALSO
.Xr getlogin 2 ,
.Xr getgrent 3 ,
.Xr getgrouplist 3 ,
.Xr getpwent 3 ,
.Xr pw_dup 3 ,
.Xr sysconf 3 ,
.Xr passwd 5 ,
.Xr Makefile.yp 8 ,
.Xr pwd_mkdb 8 ,
.Xr vipw 8 ,
.Xr yp 8
.Sh STANDARDS
The
.Fn getpwnam ,
.Fn getpwnam_r ,
.Fn getpwuid ,
and
.Fn getpwuid_r
functions are compliant with the
.St -p1003.1-2008
specification.
.Pp
.Sx YP support
and the
.Fn setpassent
function are extensions to that specification.
.Sh HISTORY
A predecessor to
.Fn getpwuid ,
.Fn getpw ,
first appeared in
.At v4 .
The
.Fn getpwnam
and
.Fn getpwuid
functions appeared in
.At v7 ,
.Fn setpassent
in
.Bx 4.3 Reno ,
and
.Fn getpwnam_shadow
and
.Fn getpwuid_shadow
in
.Ox 5.9 .