Quick Navigator

Search Site

Unix VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Contact Us
Online Help
Domain Status
Man Pages

Virtual Servers

Topology Map

Server Agreement
Year 2038

USA Flag



Man Pages
CAP_PWD(3) FreeBSD Library Functions Manual CAP_PWD(3)

cap_getpwent, cap_getpwnam, cap_getpwuid, cap_getpwent_r, cap_getpwnam_r, cap_getpwuid_r, cap_setpassent, cap_setpwent, cap_endpwent, cap_pwd_limit_cmds, cap_pwd_limit_fields, cap_pwd_limit_users
library for password database operations in capability mode

library “libcap_pwd”

#include <libcasper.h>
#include <casper/cap_pwd.h>

struct passwd *
cap_getpwent(cap_channel_t *chan);

struct passwd *
cap_getpwnam(cap_channel_t *chan, const char *login);

struct passwd *
cap_getpwuid(cap_channel_t *chan, uid_t uid);

cap_getpwent_r(cap_channel_t *chan, struct passwd *pwd, char *buffer, size_t bufsize, struct passwd **result);

cap_getpwnam_r(cap_channel_t *chan, const char *name, struct passwd *pwd, char *buffer, size_t bufsize, struct passwd **result);

cap_getpwuid_r(cap_channel_t *chan, uid_t uid, struct passwd *pwd, char *buffer, size_t bufsize, struct passwd **result);

cap_setpassent(cap_channel_t *chan, int stayopen);

cap_setpwent(cap_channel_t *chan);

cap_endpwent(cap_channel_t *chan);

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

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

cap_pwd_limit_users(cap_channel_t *chan, const char * const *names, size_t nnames, uid_t *uids, size_t nuids);

The functions cap_getpwent(), cap_getpwnam(), cap_getpwuid(), cap_getpwent_r(), cap_getpwnam_r(), cap_getpwuid_r(), cap_setpassent(), cap_setpwent(), and cap_endpwent() are respectively equivalent to getpwent(3), getpwnam(3), getpwuid(3), getpwent_r(3), getpwnam_r(3), getpwuid_r(3), setpassent(3), setpwent(3), and cap_endpwent(3) except that the connection to the system.pwd service needs to be provided.

The cap_pwd_limit_cmds() function limits the functions allowed in the service. The cmds variable can be set to getpwent, getpwnam, getpwuid, getpwent_r, getpwnam_r, getpwuid_r, setpassent, setpwent, or endpwent which will allow to use the function associated with the name. The ncmds variable contains the number of cmds provided.

The cap_pwd_limit_fields() function allows limit fields returned in the structure passwd. The fields variable can be set to pw_name, pw_passwd, pw_uid, pw_gid, pw_change, pw_class, pw_gecos, pw_dir, pw_shell, pw_expire or pw_fields 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_pwd_limit_users() function allows to limit access to users. The names variable allows to limit users by name and the uids variable by the user number. The nnames and nuids variables provide numbers of limited names and uids.

The following example first opens a capability to casper and then uses this capability to create the system.pwd casper service and uses it to get a user name.
cap_channel_t *capcas, *cappwd;
const char *cmds[] = { "getpwuid" };
const char *fields[] = { "pw_name" };
uid_t uid[] = { 1 };
struct passwd *passwd;

/* 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.pwd service. */
cappwd = cap_service_open(capcas, "system.pwd");
if (cappwd == NULL)
        err(1, "Unable to open system.pwd service");

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

/* Limit service to one single function. */
if (cap_pwd_limit_cmds(cappwd, cmds, nitems(cmds)))
	err(1, "Unable to limit access to system.pwd service");

/* Limit service to one field as we only need name of the user. */
if (cap_pwd_limit_fields(cappwd, fields, nitems(fields)))
	err(1, "Unable to limit access to system.pwd service");

/* Limit service to one uid. */
if (cap_pwd_limit_users(cappwd, NULL, 0, uid, nitems(uid)))
	err(1, "Unable to limit access to system.pwd service");

passwd = cap_getpwuid(cappwd, uid[0]);
if (passwd == NULL)
	err(1, "Unable to get name of user");

printf("UID %d is associated with name %s.\n", uid[0], passwd->pw_name);


cap_enter(2), endpwent(3), err(3), getpwent(3), getpwent_r(3), getpwnam(3), getpwnam_r(3), getpwuid(3), getpwuid_r(3), setpassent(3), setpwent(3), capsicum(4), nv(9)

The cap_pwd service first appeared in FreeBSD 10.3.

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

This manual page was written by
Mariusz Zaborski <>.

May 5, 2020 FreeBSD 13.1-RELEASE

Search for    or go to Top of page |  Section 3 |  Main Index

Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with ManDoc.