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

NAME
     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
     library "libcap_pwd"

SYNOPSIS
     #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);

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

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

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

     int
     cap_setpassent(cap_channel_t *chan, int stayopen);

     void
     cap_setpwent(cap_channel_t *chan);

     void
     cap_endpwent(cap_channel_t *chan);

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

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

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

DESCRIPTION
     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.

EXAMPLES
     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. */
     cap_close(capcas);

     /* 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_close(cappwd);

SEE ALSO
     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)

HISTORY
     The cap_pwd service first appeared in FreeBSD 10.3.

AUTHORS
     The cap_pwd service was implemented by Pawel Jakub Dawidek
     <pawel@dawidek.net> under sponsorship from the FreeBSD Foundation.

     This manual page was written by
     Mariusz Zaborski <oshogbo@FreeBSD.org>.

FreeBSD 13.1-RELEASE-p6           May 5, 2020          FreeBSD 13.1-RELEASE-p6