Hey Emacs! This file is -*- nroff -*- source.
Author: Eamon Walsh ([email protected]) 2004
The two fields of the structure should be pointers to functions which behave as
malloc (3) and
free (3), which are used by default.
Use an
avc_log_callback structure to specify alternate functions for logging.
The
func_log callback should accept a
printf (3) style format and arguments and log them as desired. The default behavior prints the message on the standard error. The
func_audit callback should interpret the
auditdata parameter for the given
class , printing a human-readable interpretation to
msgbuf using no more than
msgbufsize characters. The default behavior is to ignore
auditdata .
Use an
avc_thread_callback structure to specify functions for starting and manipulating threads.
The
func_create_thread callback should create a new thread and return a pointer which references it. The thread should execute the
run argument, which does not return under normal conditions. The
func_stop_thread callback should cancel the running thread referenced by
thread . By default, threading is not used; see
KERNEL STATUS PAGE and
NETLINK NOTIFICATION below.
Use an
avc_lock_callback structure to specify functions to create, obtain, and release locks for use by threads.
The
func_alloc_lock callback should create a new lock, returning a pointer which references it. The
func_get_lock callback should obtain
lock , blocking if necessary. The
func_release_lock callback should release
lock . The
func_free_lock callback should destroy
lock , freeing any resources associated with it. The default behavior is not to perform any locking. Note that undefined behavior may result if threading is used without appropriate locking.
.
Author: Eamon Walsh ([email protected]) 2004
"avc_init" "3" "27 May 2004" "" "SELinux API documentation"
"NAME"
avc_init - legacy userspace SELinux AVC setup
.
"SYNOPSIS"
#include <selinux/selinux.h> #include <selinux/avc.h> "int avc_init(const char *" msgprefix , "const struct avc_memory_callback *" mem_callbacks ,
"const struct avc_log_callback *" log_callbacks ,
"const struct avc_thread_callback *" thread_callbacks ,
"const struct avc_lock_callback *" lock_callbacks ");" .
"DESCRIPTION"
avc_init () is deprecated; please use
avc_open (3) in conjunction with
selinux_set_callback (3) in all new code.
avc_init () initializes the userspace AVC and must be called before any other AVC operation can be performed. A non-NULL
msgprefix will be prepended to all audit messages produced by the userspace AVC. The default is `uavc'. The remaining arguments, if non-NULL, specify callbacks to be used by the userspace AVC.
.
"CALLBACKS"
The userspace AVC can be directed how to perform memory allocation, logging, thread creation, and locking via callback functions passed to
avc_init (). The purpose of this functionality is to allow the userspace AVC to be smoothly integrated into existing userspace object managers.
Use an
avc_memory_callback structure to specify alternate functions for dynamic memory allocation.
struct avc_memory_callback {
void *(*func_malloc)(size_t size);
void (*func_free)(void *ptr);
};
struct avc_log_callback {
void (*func_log)(const char *fmt, ...);
void (*func_audit)(void *auditdata,
security_class_t class,
char *msgbuf, size_t msgbufsize);
};
struct avc_thread_callback {
void *(*func_create_thread)(void (*run)(void));
void (*func_stop_thread)(void *thread);
};
struct avc_lock_callback {
void *(*func_alloc_lock)(void);
void (*func_get_lock)(void *lock);
void (*func_release_lock)(void *lock);
void (*func_free_lock)(void *lock);
};
"KERNEL STATUS PAGE"
Linux kernel version 2.6.37 supports the SELinux kernel status page, enabling userspace applications to
mmap (2) SELinux status state in read-only mode to avoid system calls during the cache hit code path.
avc_init () calls
selinux_status_open (3) to initialize the selinux status state. If successfully initialized, the userspace AVC will default to single-threaded mode and ignore the
func_create_thread and
func_stop_thread callbacks. All callbacks set via
selinux_set_callback (3) will still be honored.
avc_has_perm (3) and
selinux_check_access (3) both check for status updates through calls to
selinux_status_updated (3) at the start of each permission query and take the appropriate action.
Two status types are currently implemented.
setenforce events will change the effective enforcing state used within the AVC, and
policyload events will result in a cache flush.
.
"NETLINK NOTIFICATION"
In the event that the kernel status page is not successfully
mmap (2)'ed the AVC will default to the netlink fallback mechanism, which opens a netlink socket for receiving status updates.
setenforce and
policyload events will have the same results as for the status page implementation, but all status update checks will now require a system call.
By default,
avc_open (3) does not set threading or locking callbacks. In the fallback case, the userspace AVC checks for new netlink messages at the start of each permission query. If threading and locking callbacks are passed to
avc_init (), a dedicated thread will be started to listen on the netlink socket. This may increase performance in the absence of the status page and will ensure that log messages are generated immediately rather than at the time of the next permission query.
.
"RETURN VALUE"
Functions with a return value return zero on success. On error, -1 is returned and
errno is set appropriately.
.
"NOTES"
The
msgprefix argument to
avc_init () currently has a length limit of 15 characters and will be truncated if necessary.
If a provided
func_malloc callback does not set
errno appropriately on error, userspace AVC calls may exhibit the
same behavior.
If a netlink thread has been created and an error occurs on the socket (such as an access error), the thread may terminate and cause the userspace AVC to return
EINVAL on all further permission checks until
avc_destroy is called.
.
"AUTHOR"
Eamon Walsh <[email protected]>
.
"SEE ALSO"
avc_open (3), selinux_status_open (3), selinux_status_updated (3), selinux_set_callback (3), selinux (8)