kern: security: Improve scalability of MAC checks

The concept of resource borders is mostly used for resources that can
easily be mapped into memory, synced and contain attributes. However,
some things (e.g., a network resource, keyboard input, etc) may not be
great with raw memory mappings. This commit mitigates this problem.

Signed-off-by: Ian Moffett <ian@osmora.org>

3 files changed, 10 insertions, 12 deletions

diff --git a/src/sys/compat/unix/os/os_mac.c b/src/sys/compat/unix/os/os_mac.c
index be0ec84..4b52868 100644
--- a/src/sys/compat/unix/os/os_mac.c
+++ b/src/sys/compat/unix/os/os_mac.c
@@ -92,7 +92,7 @@ sys_query(struct syscall_args *scargs)
     }
 
     /* Can we even touch this? */
-    error = mac_check_creds(self, bop);
+    error = mac_check_lvl(self, bop->level);
     if (error < 0) {
         return error;
     }
diff --git a/src/sys/include/os/mac.h b/src/sys/include/os/mac.h
index 2c20eab..7e7f083 100644
--- a/src/sys/include/os/mac.h
+++ b/src/sys/include/os/mac.h
@@ -92,15 +92,16 @@ struct mac_border {
 
 /*
  * Check creds with a specific process and a specific
- * resource border.
+ * MAC level, useful when a resource border is not enough
+ * for a specific application.
  *
- * @procp: Process to check with border
- * @mbp: Border to 'procp' is trying to access
+ * @procp: Process to check with level
+ * @lvl: Level to check
  *
  * Returns zero if the check passed, otherwise a less than
  * zero value if the check failed.
  */
-int mac_check_creds(struct proc *procp, struct mac_border *mbp);
+int mac_check_lvl(struct proc *procp, mac_level_t lvl);
 
 /*
  * Map a resource into process address space by
diff --git a/src/sys/os/os_mac.c b/src/sys/os/os_mac.c
index 898b476..2443b23 100644
--- a/src/sys/os/os_mac.c
+++ b/src/sys/os/os_mac.c
@@ -39,17 +39,14 @@ static struct mac_border *bortab[__BORDER_MAX] = {
     [BORDER_FBDEV] = &g_fbdev_border
 };
 
-/*
- * Check process creds against border
- */
 int
-mac_check_creds(struct proc *procp, struct mac_border *mbp)
+mac_check_lvl(struct proc *procp, mac_level_t lvl)
 {
-    if (procp == NULL || mbp == NULL) {
+    if (procp == NULL) {
         return -EINVAL;
     }
 
-    if (procp->level < mbp->level) {
+    if (procp->level < lvl) {
         return -EACCES;
     }
 
@@ -75,7 +72,7 @@ mac_map(struct mac_border *mbp, off_t off, size_t len, void **res, int flags)
         return -EINVAL;
     }
 
-    error = mac_check_creds(procp, mbp);
+    error = mac_check_lvl(procp, mbp->level);
     if (error < 0) {
         return error;
     }