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CAP_GRP(3)		 BSD Library Functions Manual		    CAP_GRP(3)

     cap_getgrent, cap_getgrnam, cap_getgrgid, cap_getgrent_r, cap_getgrnam_r,
     cap_getgrgid_r, cap_setgroupent, cap_setgrent, cap_endgrent,
     cap_grp_limit_cmds, cap_grp_limit_fields, cap_grp_limit_groups -- library
     for group database	operations in capability mode

     library "libcap_grp"

     #include <sys/nv.h>
     #include <libcasper.h>
     #include <casper/cap_grp.h>

     struct group *
     cap_getgrent(cap_channel_t	*chan);

     struct group *
     cap_getgrnam(cap_channel_t	*chan, const char *name);

     struct group *
     cap_getgrgid(cap_channel_t	*chan, gid_t gid);

     cap_getgrent_r(cap_channel_t *chan, struct	group *grp, char *buffer,
	 size_t	bufsize, struct	group **result);

     cap_getgrnam_r(cap_channel_t *chan, const char *name, struct group	*grp,
	 char *buffer, size_t bufsize, struct group **result);

     cap_getgrgid_r(cap_channel_t *chan, gid_t gid, struct group *grp,
	 char *buffer, size_t bufsize, struct group **result);

     cap_setgroupent(cap_channel_t *chan, int stayopen);

     cap_setgrent(cap_channel_t	*chan);

     cap_endgrent(cap_channel_t	*chan);

     cap_grp_limit_cmds(cap_channel_t *chan, const char	* const	*cmds,
	 size_t	ncmds);

     cap_grp_limit_fields(cap_channel_t	*chan, const char * const *fields,
	 size_t	nfields);

     cap_grp_limit_groups(cap_channel_t	*chan, const char * const *names,
	 size_t	nnames,	const gid_t *gids, size_t ngids);

     The functions cap_getgrent(), cap_getgrnam(), cap_getgrgid(),
     cap_getgrent_r(), cap_getgrnam_r(), cap_getgrgid_r(), cap_setgroupent(),
     cap_setgrent(), and cap_endgrent()	are respectively equivalent to
     getgrent(3), getgrnam(3), getgrgid(3), getgrent_r(3), getgrnam_r(3),
     getgrgid_r(3), setgroupent(3), setgrent(3), and endgrent(3) except	that
     the connection to the system.grp service needs to be provided.

     The cap_grp_limit_cmds() function limits the functions allowed in the
     service.  The cmds	variable can be	set to getgrent, getgrnam, getgrgid,
     getgrent_r, getgrnam_r, getgrgid_r, setgroupent, setgrent,	or endgrent
     which will	allow to use the function associated with the name.  The ncmds
     variable contains the number of cmds provided.

     The cap_grp_limit_fields()	function allows	limit fields returned in the
     structure group.  The fields variable can be set to gr_name gr_passwd
     gr_gid or gr_mem.	The field which	was set	as the limit will be returned,
     while the rest of the values not set this way will	have default values.
     The nfields variable contains the number of fields	provided.

     The cap_grp_limit_groups()	function allows	to limit access	to groups.
     The names variable	allows to limit	groups by name and the gids variable
     by	the group number.  The nnames and ngids	variables provide numbers of
     limited names and gids.

     The following example first opens a capability to casper and then uses
     this capability to	create the system.grp casper service and uses it to
     get a group name.

     cap_channel_t *capcas, *capgrp;
     const char	*cmds[]	= { "getgrgid" };
     const char	*fields[] = { "gr_name"	};
     const gid_t gid[] = { 1 };
     struct group *group;

     /*	Open capability	to Casper. */
     capcas = cap_init();
     if	(capcas	== NULL)
	     err(1, "Unable to contact Casper");

     /*	Enter capability mode sandbox. */
     if	(cap_enter() < 0 && errno != ENOSYS)
	     err(1, "Unable to enter capability	mode");

     /*	Use Casper capability to create	capability to the system.grp service. */
     capgrp = cap_service_open(capcas, "system.grp");
     if	(capgrp	== NULL)
	     err(1, "Unable to open system.grp service");

     /*	Close Casper capability, we don't need it anymore. */

     /*	Limit service to one single function. */
     if	(cap_grp_limit_cmds(capgrp, cmds, nitems(cmds)))
	     err(1, "Unable to limit access to system.grp service");

     /*	Limit service to one field as we only need name	of the group. */
     if	(cap_grp_limit_fields(capgrp, fields, nitems(fields)))
	     err(1, "Unable to limit access to system.grp service");

     /*	Limit service to one gid. */
     if	(cap_grp_limit_groups(capgrp, NULL, 0, gid, nitems(gid)))
	     err(1, "Unable to limit access to system.grp service");

     group = cap_getgrgid(capgrp, gid[0]);
     if	(group == NULL)
	     err(1, "Unable to get name	of group");

     printf("GID %d is associated with name %s.\n", gid[0], group->gr_name);


     cap_enter(2), endgrent(3),	err(3),	getgrent(3), getgrent_r(3),
     getgrgid(3), getgrgid_r(3), getgrnam(3), getgrnam_r(3), setgrent(3),
     setgroupent(3), capsicum(4), nv(9)

     The cap_grp service was implemented by Pawel Jakub	Dawidek
     <> under sponsorship from	the FreeBSD Foundation.

     This manual page was written by
     Mariusz Zaborski <>.

BSD				March 18, 2018				   BSD


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