получать и проверять решения доступа SELinux (obtain and audit SELinux access decisions)
Имя (Name)
avc_has_perm, avc_has_perm_noaudit, avc_audit, avc_entry_ref_init
- obtain and audit SELinux access decisions
Синопсис (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);
Описание (Description)
Direct use of these functions is generally discouraged in favor
of the higher level interface selinux_check_access(3) since the
latter automatically handles the dynamic mapping of class and
permission names to their policy values and proper handling of
allow_unknown.
When using any of the functions that take policy integer values
for classes or permissions as inputs, use
string_to_security_class(3) and string_to_av_perm(3) to map the
class and permission names to their policy values. These values
may change across a policy reload, so they should be re-acquired
on every use or using a SELINUX_CB_POLICYLOAD callback set via
selinux_set_callback(3).
An alternative approach is to use selinux_set_mapping(3) to
create a mapping from class and permission index values used by
the application to the policy values, thereby allowing the
application to pass its own fixed constants for the classes and
permissions to these functions and internally mapping them on
demand. However, this also requires setting up a callback as
above to address policy reloads.
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).
Входные ссылки (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.
Возвращаемое значение (Return value)
If requested permissions are granted, zero is returned. If
requested permissions are denied or an error occurred, -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.
Ошибки (Error)
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.
Примечание (Note)
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.
