NAME
avc_has_perm, avc_has_perm_noaudit, avc_audit, avc_entry_ref_init -
obtain and audit SELinux access decisions.
SYNOPSIS
#include <selinux/selinux.h>
#include <selinux/avc.h>
void avc_entry_ref_init(struct avc_entry_ref *aeref);
int avc_has_perm(security_id_t ssid, security_id_t tsid,
security_class_t tclass, access_vector_t requested,
struct avc_entry_ref *aeref, void *auditdata);
int avc_has_perm_noaudit(security_id_t ssid, security_id_t tsid,
security_class_t tclass, access_vector_t requested,
struct avc_entry_ref *aeref, struct av_decision *avd);
void avc_audit(security_id_t ssid, security_id_t tsid,
security_class_t tclass, access_vector_t requested,
struct av_decision *avd, int result, void *auditdata);
DESCRIPTION
avc_entry_ref_init initializes an avc_entry_ref structure; see ENTRY
REFERENCES below. This function may be implemented as a macro.
avc_has_perm checks whether the requested permissions are granted for
subject SID ssid and target SID tsid, interpreting the permissions
based on tclass and updating aeref, if non-NULL, to refer to a cache
entry with the resulting decision. The granting or denial of
permissions is audited in accordance with the policy. The auditdata
parameter is for supplemental auditing; see avc_audit below.
avc_has_perm_noaudit behaves as avc_has_perm without producing an audit
message. The access decision is returned in avd and can be passed to
avc_audit explicitly.
avc_audit produces an audit message for the access query represented by
ssid, tsid, tclass, and requested, with a decision represented by avd.
Pass the value returned by avc_has_perm_noaudit as result. The
auditdata parameter is passed to the user-supplied func_audit callback
and can be used to add supplemental information to the audit message;
see avc_init(3).
ENTRY REFERENCES
Entry references can be used to speed cache performance for repeated
queries on the same subject and target. The userspace AVC will check
the aeref argument, if supplied, before searching the cache on a
permission query. After a query is performed, aeref will be updated to
reference the cache entry for that query. A subsequent query on the
same subject and target will then have the decision at hand without
having to walk the cache.
After declaring an avc_entry_ref structure, use avc_entry_ref_init to
initialize it before passing it to avc_has_perm or avc_has_perm_noaudit
for the first time. Using an uninitialized structure will produce
undefined behavior.
RETURN VALUE
If requested permissions are granted, zero is returned. If requested
permissions are denied or an error occured, -1 is returned and errno is
set appropriately.
In permissive mode, zero will be returned and errno unchanged even if
permissions were denied. avc_has_perm will still produce an audit
message in this case.
ERRORS
EACCES A requested permission was denied.
EINVAL The tclass and/or the security contexts referenced by ssid and
tsid are not recognized by the currently loaded policy.
ENOMEM An attempt to allocate memory failed.
NOTES
Internal errors encountered by the userspace AVC may cause certain
values of errno to be returned unexpectedly. For example, netlink
socket errors may produce EACCES or EINVAL. Make sure that userspace
object managers are granted appropriate access to netlink by the
policy.
AUTHOR
Eamon Walsh <ewalsh@tycho.nsa.gov>
SEE ALSO
avc_init(3), avc_context_to_sid(3), avc_cache_stats(3),
avc_add_callback(3), security_compute_av(3) selinux(8)
27 May 2004 avc_has_perm(3)