kern: security: Add initial support for MAC

This commit introduces initial support for mandatory access control. As
one may recall, L5 follows "everything is memory". In order to interact
with a resource, a process must request it from the kernel in the form
of a (sometimes) syncable memory buffer.

Each resource as well as processes have an access level, if a process
attempts to request a resource with a higher access level than it, the
request is rejected by the kernel. However, if a process has a greater
than or equal access level as a resource, the request can be granted.

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

1 files changed, 106 insertions, 0 deletions

diff --git a/src/sys/os/os_mac.c b/src/sys/os/os_mac.c
new file mode 100644
index 0000000..e86e848
--- /dev/null
+++ b/src/sys/os/os_mac.c
@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the project nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/proc.h>
+#include <sys/errno.h>
+#include <sys/types.h>
+#include <sys/param.h>
+#include <io/video/fbdev.h>
+#include <os/mac.h>
+
+static struct mac_border *bortab[__BORDER_MAX] = {
+    [BORDER_NONE] = NULL,
+    [BORDER_FBDEV] = &g_fbdev_border
+};
+
+/*
+ * Check process creds against border
+ */
+int
+mac_check_creds(struct proc *procp, struct mac_border *mbp)
+{
+    if (procp == NULL || mbp == NULL) {
+        return -EINVAL;
+    }
+
+    if (procp->level < mbp->level) {
+        return -EACCES;
+    }
+
+    return 0;
+}
+
+/*
+ * Map a resource into process address space
+ */
+int
+mac_map(struct mac_border *mbp, off_t off, size_t len, void **res, int flags)
+{
+    struct mac_map_args args;
+    struct proc *procp = proc_self();
+    struct mac_ops *ops;
+    int error;
+
+    if (procp == NULL || mbp == NULL) {
+        return -EINVAL;
+    }
+
+    if (res == NULL) {
+        return -EINVAL;
+    }
+
+    error = mac_check_creds(procp, mbp);
+    if (error < 0) {
+        return error;
+    }
+
+    ops = mbp->ops;
+    if (ops->map == NULL) {
+        return -EIO;
+    }
+
+    args.off = off;
+    args.len = len;
+    args.flags = flags;
+    args.dp_res = res;
+    return ops->map(mbp, &args);
+}
+
+/*
+ * Grab a specific border using an ID
+ */
+struct mac_border *
+mac_get_border(border_id_t id)
+{
+    if (id >= NELEM(bortab)) {
+        return NULL;
+    }
+
+    return bortab[id];
+}