aa_policy_cache(3)

NAME
aa_policy_cache - an opaque object representing an AppArmor policy cache

aa_policy_cache_new - create a new aa_policy_cache object from a path

aa_policy_cache_ref - increments the ref count of an aa_policy_cache object

aa_policy_cache_unref - decrements the ref count and frees the aa_policy_cache object when 0

aa_policy_cache_remove - removes all policy cache files under a path

aa_policy_cache_replace_all - performs a kernel policy replacement of all cached policies

aa_policy_cache_dir_path - returns the path to the aa_policy_cache directory

aa_policy_cache_dir_path_preview - returns a preview of the path to the aa_policy_cache directory without an existing aa_policy_cache object

SYNOPSIS
#include <sys/apparmor.h>

typedef struct aa_policy_cache aa_policy_cache;

int aa_policy_cache_new(aa_policy_cache **policy_cache, aa_features *kernel_features, int dirfd, const char *path, uint16_t max_caches);

int aa_policy_cache_add_ro_dir(aa_policy_cache *policy_cache, int dirfd, const char *path);

aa_policy_cache *aa_policy_cache_ref(aa_policy_cache *policy_cache);

void aa_policy_cache_unref(aa_policy_cache *policy_cache);

int aa_policy_cache_remove(int dirfd, const char *path);

int aa_policy_cache_replace_all(aa_policy_cache *policy_cache, aa_kernel_interface *kernel_interface);

char *aa_policy_cache_dir_path(aa_policy_cache *policy_cache, int level);

char *aa_policy_cache_dir_path_preview(aa_features *kernel_features, int dirfd, const char *path);

Link with -lapparmor when compiling.

DESCRIPTION
The aa_policy_cache object contains information about a set of AppArmor policy cache files. The policy cache files are the binary representation of a human-readable AppArmor profile. The binary representation is the form that is loaded into the kernel.

The aa_policy_cache_new() function creates an aa_policy_cache object based upon a directory file descriptor and path. See the openat(2) man page for examples of dirfd and path. The path must point to a directory and it will be used as the basis for the location of policy cache files. See aa_policy_cache_dir_path to find out which directory will be used to store the binary policy cache files. If additional overlay cache directories are used (see aa_policy_cache_add_ro_dir) the directory specified in aa_policy_cache_new is the first directory searched and is the writable overlay. If kernel_features is NULL, then the features of the current kernel are used. When specifying a valid kernel_features object, it must be compatible with the features of the kernel of interest. The value of max_caches should be equal to the number of caches that should be allowed before old caches are automatically reaped. The definition of what is considered to be an old cache is private to libapparmor. Specifying 0 means that no new caches should be created and only existing, valid caches may be used. Specifying UINT16_MAX means that a new cache may be created and that the reaping of old caches is disabled. The allocated aa_policy_cache object must be freed using aa_policy_cache_unref().

The aa_policy_cache_add_ro_dir() function adds an existing cache directory to the policy cache, as a readonly layer under the primary directory the cache was created with. When the cache is searched for an existing cache file the primary directory will be searched and then the readonly directories in the order that they were added to the policy cache. This allows the policy cache to be seeded with precompiled policy that can be updated by overlaying the read only cache file with one written to the primary cache dir.

aa_policy_cache_ref() increments the reference count on the policy_cache object.

aa_policy_cache_unref() decrements the reference count on the policy_cache object and releases all corresponding resources when the reference count reaches zero.

The aa_policy_cache_remove() function deletes all of the policy cache files based upon a directory file descriptor and path. The path must point to a directory. See the openat(2) man page for examples of dirfd and path.

The aa_policy_cache_replace_all() function can be used to perform a policy replacement of all of the cache policies in the cache directory represented by the policy_cache object. If kernel_interface is NULL, then the current kernel interface is used. When specifying a valid kernel_interface object, it must be the interface of the currently running kernel.

The aa_policy_cache_dir_path() function provides the path to the cache directory for a policy_cache object at level in the policy cache overlay of cache directories. A level of 0 will always be present and is the first directory to search in an overlay of cache directories, and will also be the writable cache directory layer. Binary policy cache files will be located in the directory returned by this function.

The aa_policy_cache_dir_levels() function provides access to the number of directories that are being overlaid to create the policy cache.

RETURN VALUE
The aa_policy_cache_new() function returns 0 on success and *policy_cache will point to an aa_policy_cache object that must be freed by aa_policy_cache_unref(). -1 is returned on error, with errno set appropriately, and *policy_cache will be set to NULL.

aa_policy_cache_ref() returns the value of policy_cache.

aa_policy_cache_remove() and aa_policy_cache_replace_all() return 0 on success. -1 is returned on error, with errno set appropriately.

aa_policy_cache_dir_path() returns a path string which must be freed by the caller. NULL is returned on error, with errno set appropriately.

aa_policy_cache_dir_levels() returns a number indicating the number of directory levels there are associated with the policy_cache.

aa_policy_cache_dir_path_preview() is the same as aa_policy_cache_dir_path() except that it doesn't require an existing aa_policy_cache object. This is useful if the calling program cannot create an aa_policy_cache object due to lack of privileges needed to create the cache directory.

ERRORS
The errno value will be set according to the underlying error in the aa_policy_cache family of functions that return -1 or NULL on error.

NOTES
All aa_policy_cache functions described above, except for the aa_policy_cache_dir_path() function was added in libapparmor version 2.13. All the other aa_policy_cache functions described above are present in libapparmor version 2.10.

aa_policy_cache_unref() saves the value of errno when called and restores errno before exiting in libapparmor version 2.12 and newer.

BUGS
None known. If you find any, please report them at <https://gitlab.com/apparmor/apparmor/-/issues>.

SEE ALSO
aa_features(3), aa_kernel_interface(3), openat(2) and <https://wiki.apparmor.net>.