Add uid_from_user() and gid_from_group(), derived from pax's cache.c.

It replaces the existing pwcache.c functions user_from_uid(3) and
group_from_gid(3) with the pax equivalents.  Adapted from NetBSD
(mycroft) changes from our own pax's cache.c.  OK guenther@

include/grp.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: grp.h,v 1.12 2014/08/31 04:04:38 guenther Exp $	*/
+/*	$OpenBSD: grp.h,v 1.13 2018/09/13 12:31:15 millert Exp $	*/
 /*	$NetBSD: grp.h,v 1.7 1995/04/29 05:30:40 cgd Exp $	*/
 
 /*-
@@ -70,7 +70,8 @@ int		 getgrnam_r(const char *, struct group *, char *,
 #endif
 #if __BSD_VISIBLE
 int		 setgroupent(int);
-char		*group_from_gid(gid_t, int);
+int		 gid_from_group(const char *, gid_t *);
+const char	*group_from_gid(gid_t, int);
 #endif
 __END_DECLS
 

include/pwd.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: pwd.h,v 1.25 2017/03/09 10:13:03 fcambus Exp $	*/
+/*	$OpenBSD: pwd.h,v 1.26 2018/09/13 12:31:15 millert Exp $	*/
 /*	$NetBSD: pwd.h,v 1.9 1996/05/15 21:36:45 jtc Exp $	*/
 
 /*-
@@ -106,7 +106,8 @@ void		 endpwent(void);
 #endif
 #if __BSD_VISIBLE
 int		 setpassent(int);
-char		*user_from_uid(uid_t, int);
+int		 uid_from_user(const char *, uid_t *);
+const char	*user_from_uid(uid_t, int);
 char		*bcrypt_gensalt(u_int8_t);
 char		*bcrypt(const char *, const char *);
 int		bcrypt_newhash(const char *, int, char *, size_t);

lib/libc/Symbols.list

@@ -663,6 +663,7 @@ getpwuid_shadow
 getttyent
 getttynam
 getusershell
+gid_from_group
 glob
 globfree
 group_from_gid
@@ -798,6 +799,7 @@ ttyname
 ttyname_r
 ttyslot
 ualarm
+uid_from_user
 uname
 unvis
 user_from_uid

lib/libc/gen/getgrent.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: getgrent.c,v 1.46 2015/12/01 15:08:25 deraadt Exp $ */
+/*	$OpenBSD: getgrent.c,v 1.47 2018/09/13 12:31:15 millert Exp $ */
 /*
  * Copyright (c) 1989, 1993
  *	The Regents of the University of California.  All rights reserved.
@@ -144,6 +144,7 @@ getgrnam_r(const char *name, struct group *grp, char *buffer,
 	errno = errnosave;
 	return ret;
 }
+DEF_WEAK(getgrnam_r);
 
 static struct group *
 getgrgid_gs(gid_t gid, struct group *p_gr, struct group_storage *gs)

lib/libc/gen/pwcache.3

@@ -1,4 +1,4 @@
-.\"	$OpenBSD: pwcache.3,v 1.13 2016/03/26 14:36:37 schwarze Exp $
+.\"	$OpenBSD: pwcache.3,v 1.14 2018/09/13 12:31:15 millert Exp $
 .\"
 .\" Copyright (c) 1989, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -27,19 +27,25 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: March 26 2016 $
+.Dd $Mdocdate: September 13 2018 $
 .Dt USER_FROM_UID 3
 .Os
 .Sh NAME
 .Nm user_from_uid ,
+.Nm uid_from_user ,
 .Nm group_from_gid
+.Nm gid_from_group
 .Nd cache password and group entries
 .Sh SYNOPSIS
-.In grp.h
 .In pwd.h
-.Ft char *
+.Ft int
+.Fn uid_from_user "const char *name" "uid_t *uid"
+.Ft const char *
 .Fn user_from_uid "uid_t uid" "int nouser"
-.Ft char *
+.In grp.h
+.Ft int
+.Fn gid_from_group "const char *name" "gid_t *gid"
+.Ft const char *
 .Fn group_from_gid "gid_t gid" "int nogroup"
 .Sh DESCRIPTION
 The
@@ -60,6 +66,23 @@ unless the argument
 is non-zero, in which case a null pointer is returned.
 .Pp
 The
+.Fn uid_from_user
+function returns the user ID associated with the argument
+.Fa name .
+The user ID is cached so that multiple calls with the same
+.Fa name
+do not require additional calls to
+.Xr getpwnam 3 .
+If there is no user ID associated with the
+.Fa name ,
+the
+.Fn uid_from_user
+function returns -1;
+otherwise it stores the user ID at the location pointed to by
+.Fa uid
+and returns 0.
+.Pp
+The
 .Fn group_from_gid
 function returns the group name associated with the argument
 .Fa gid .
@@ -75,6 +98,23 @@ to a string representation of the
 unless the argument
 .Fa nogroup
 is non-zero, in which case a null pointer is returned.
+.Pp
+The
+.Fn gid_from_group
+function returns the group ID associated with the argument
+.Fa name .
+The group ID is cached so that multiple calls with the same
+.Fa name
+do not require additional calls to
+.Xr getgrnam 3 .
+If there is no group ID associated with the
+.Fa name ,
+the
+.Fn gid_from_group
+function returns -1;
+otherwise it stores the group ID at the location pointed to by
+.Fa gid
+and returns 0.
 .Sh SEE ALSO
 .Xr getgrgid 3 ,
 .Xr getpwuid 3
@@ -85,3 +125,12 @@ and
 .Fn group_from_gid
 functions first appeared in
 .Bx 4.4 .
+.Pp
+The
+.Fn uid_from_user
+and
+.Fn gid_from_group
+functions were ported from
+.Nx
+and first appeared in
+.Ox 6.4 .