security_compute_av(3) SELinux API documentation security_compute_av(3)
NAME
security_compute_av, security_compute_av_flags, security_compute_cre-
ate, security_compute_create_name, security_compute_relabel, secu-
rity_compute_member, security_compute_user, security_validatetrans, se-
curity_get_initial_context - query the SELinux policy database in the
kernel
SYNOPSIS
#include <selinux/selinux.h>
int security_compute_av(char *scon, char *tcon, security_class_t
tclass, access_vector_t requested, struct av_decision *avd);
int security_compute_av_raw(char *scon, char *tcon, security_class_t
tclass, access_vector_t requested, struct av_decision *avd);
int security_compute_av_flags(char *scon, char *tcon, security_class_t
tclass, access_vector_t requested, struct av_decision *avd);
int security_compute_av_flags_raw(char *scon, char *tcon, secu-
rity_class_t tclass, access_vector_t requested, struct av_decision
*avd);
int security_compute_create(char *scon, char *tcon, security_class_t
tclass, char **newcon);
int security_compute_create_raw(char *scon, char *tcon, secu-
rity_class_t tclass, char **newcon);
int security_compute_create_name(char *scon, char *tcon, secu-
rity_class_t tclass, const char *objname, char **newcon);
int security_compute_create_name_raw(char *scon, char *tcon, secu-
rity_class_t tclass, const char *objname, char **newcon);
int security_compute_relabel(char *scon, char *tcon, security_class_t
tclass, char **newcon);
int security_compute_relabel_raw(char *scon, char *tcon, secu-
rity_class_t tclass, char **newcon);
int security_compute_member(char *scon, char *tcon, security_class_t
tclass, char **newcon);
int security_compute_member_raw(char *scon, char *tcon, secu-
rity_class_t tclass, char **newcon);
int security_compute_user(char *scon, const char *username, char
***con);
int security_compute_user_raw(char *scon, const char *username, char
***con);
int security_validatetrans(char *scon, const char *tcon, secu-
rity_class_t tclass, char *newcon);
int security_validatetrans_raw(char *scon, const char *tcon, secu-
rity_class_t tclass, char *newcon);
int security_get_initial_context(const char *name, char **con);
int security_get_initial_context_raw(const char *name, char **con);
int selinux_check_access(const char *scon, const char *tcon, const char
*class, const char *perm, void *auditdata);
int selinux_check_passwd_access(access_vector_t requested);
int checkPasswdAccess(access_vector_t requested);
DESCRIPTION
This family of functions is used to obtain policy decisions from the
SELinux kernel security server (policy engine). In general, direct use
of security_compute_av() and its variant interfaces is discouraged in
favor of using selinux_check_access() since the latter automatically
handles the dynamic mapping of class and permission names to their pol-
icy values, initialization and use of the Access Vector Cache (AVC),
and proper handling of per-domain and global permissive mode and al-
low_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.
security_compute_av() queries whether the policy permits the source
context scon to access the target context tcon via class tclass with
the requested access vector. The decision is returned in avd.
security_compute_av_flags() is identical to security_compute_av but ad-
ditionally sets the flags field of avd. Currently one flag is sup-
ported: SELINUX_AVD_FLAGS_PERMISSIVE, which indicates the decision is
computed on a permissive domain.
security_compute_create() is used to compute a context to use for la-
beling a new object in a particular class based on a SID pair.
security_compute_create_name() is identical to
security_compute_create() but also takes name of the new object in cre-
ation as an argument. When TYPE_TRANSITION rule on the given class and
a SID pair has object name extension, we shall be able to obtain a cor-
rect newcon according to the security policy. Note that this interface
is only supported on the linux 2.6.40 or later. In the older kernel,
the object name will be simply ignored.
security_compute_relabel() is used to compute the new context to use
when relabeling an object, it is used in the pam_selinux.so source and
the newrole source to determine the correct label for the tty at login
time, but can be used for other things.
security_compute_member() is used to compute the context to use when
labeling a polyinstantiated object instance.
security_compute_user() is used to determine the set of user contexts
that can be reached from a source context. This function is deprecated;
use get_ordered_context_list(3) instead.
security_validatetrans() is used to determine if a transition from scon
to newcon using tcon as the object is valid for object class tclass.
This checks against the mlsvalidatetrans and validatetrans constraints
in the loaded policy. Returns 0 if allowed, and -1 if an error occurred
with errno set.
security_get_initial_context() is used to get the context of a kernel
initial security identifier specified by name
security_compute_av_raw(), security_compute_av_flags_raw(),
security_compute_create_raw(), security_compute_create_name_raw(),
security_compute_relabel_raw(), security_compute_member_raw(),
security_compute_user_raw() security_validatetrans_raw() and
security_get_initial_context_raw() behave identically to their non-raw
counterparts but do not perform context translation.
selinux_check_access() is used to check if the source context has the
access permission for the specified class on the target context.
selinux_check_passwd_access() is used to check for a permission in the
passwd class. selinux_check_passwd_access() uses getprevcon(3) for the
source and target security contexts.
checkPasswdAccess() is a deprecated alias of the
selinux_check_passwd_access() function.
RETURN VALUE
Returns zero on success or -1 on error.
SEE ALSO
string_to_security_class(3), string_to_av_perm(3), selinux_set_call-
back(3), selinux_set_mapping(3), getprevcon(3), get_ordered_con-
text_list(3), selinux(8)
russell@coker.com.au 1 January 2004 security_compute_av(3)
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