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avc_add_callback(3)        SELinux API documentation       avc_add_callback(3)

NAME
       avc_add_callback  - additional event notification for SELinux userspace
       object managers
SYNOPSIS
       #include <selinux/selinux.h>
       #include <selinux/avc.h>
       int avc_add_callback(int (*callback)(uint32_t event,
                                            security_id_t ssid,
                                            security_id_t tsid,
                                            security_class_t tclass,
                                            access_vector_t perms,
                                            access_vector_t *out_retained),
                            uint32_t events, security_id_t ssid,
                            security_id_t tsid, security_class_t tclass,
                            access_vector_t perms);
DESCRIPTION
       avc_add_callback() is used to register callback functions  on  security
       events.  The purpose of this functionality is to allow userspace object
       managers to take additional action when a policy change, usually a pol-
       icy reload, causes permissions to be granted or revoked.
       events  is  the  bitwise-or of security events on which to register the
       callback; see SECURITY EVENTS below.
       ssid, tsid, tclass, and perms specify the source and target SID's, tar-
       get  class,  and specific permissions that the callback wishes to moni-
       tor.  The special symbol SECSID_WILD may be passed  as  the  source  or
       target and will cause any SID to match.
       callback is the callback function provided by the userspace object man-
       ager.  The event argument indicates the security event which  occurred;
       the  remaining  arguments  are  interpreted  according  to the event as
       described below.  The return value of the callback should  be  zero  on
       success, -1 on error with errno set appropriately (but see RETURN VALUE
       below).
SECURITY EVENTS
       In all cases below, ssid and/or tsid may be set to  SECSID_WILD,  indi-
       cating  that  the  change  applies  to  all source and/or target SID's.
       Unless otherwise indicated, the out_retained parameter is unused.
       AVC_CALLBACK_GRANT
              Previously denied permissions are now  granted  for  ssid,  tsid
              with  respect  to  tclass.   perms  indicates the permissions to
              grant.
       AVC_CALLBACK_TRY_REVOKE
              Previously granted permissions are now conditionally revoked for
              ssid,  tsid with respect to tclass.  perms indicates the permis-
              sions to revoke.  The callback should set  out_retained  to  the
              subset  of  perms  which  are  retained as migrated permissions.
              Note that out_retained is ignored if the callback returns -1.
       AVC_CALLBACK_REVOKE
              Previously granted permissions are now  unconditionally  revoked
              for ssid, tsid with respect to tclass.  perms indicates the per-
              missions to revoke.
       AVC_CALLBACK_RESET
              Indicates that the cache was flushed.  The SID, class, and  per-
              mission arguments are unused and are set to NULL.
       AVC_CALLBACK_AUDITALLOW_ENABLE
              The  permissions  given  by  perms  should  now  be audited when
              granted for ssid, tsid with respect to tclass.
       AVC_CALLBACK_AUDITALLOW_DISABLE
              The permissions given by perms should no longer be audited  when
              granted for ssid, tsid with respect to tclass.
       AVC_CALLBACK_AUDITDENY_ENABLE
              The permissions given by perms should now be audited when denied
              for ssid, tsid with respect to tclass.
       AVC_CALLBACK_AUDITDENY_DISABLE
              The permissions given by perms should no longer be audited  when
              denied for ssid, tsid with respect to tclass.
RETURN VALUE
       On  success, avc_add_callback() returns zero.  On error, -1 is returned
       and errno is set appropriately.
       A return value of -1 from a callback is interpreted as a failed  policy
       operation.   If such a return value is encountered, all remaining call-
       backs registered on the  event  are  called.   In  threaded  mode,  the
       netlink  handler  thread may then terminate and cause the userspace AVC
       to return EINVAL on all further permission checks until  avc_destroy(3)
       is  called.   In  non-threaded  mode, the permission check on which the
       error occurred will return -1 and the value of errno encountered to the
       caller.  In both cases, a log message is produced and the kernel may be
       notified of the error.
ERRORS
       ENOMEM An attempt to allocate memory failed.
NOTES
       If the userspace AVC is running in threaded mode, callbacks  registered
       via  avc_add_callback()  may  be executed in the context of the netlink
       handler thread.  This  will  likely  introduce  synchronization  issues
       requiring the use of locks.  See avc_init(3).
       Support for dynamic revocation and retained permissions is mostly unim-
       plemented in the SELinux kernel module.  The only security  event  that
       currently gets exercised is AVC_CALLBACK_RESET.
AUTHOR
       Eamon Walsh <ewalsh AT tycho.gov>
SEE ALSO
       avc_init(3), avc_has_perm(3), avc_context_to_sid(3),
       avc_cache_stats(3), security_compute_av(3) selinux(8)

                                  9 June 2004              avc_add_callback(3)