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>

7 files changed, 449 insertions, 2 deletions

diff --git a/src/sys/compat/unix/os/os_mac.c b/src/sys/compat/unix/os/os_mac.c
new file mode 100644
index 0000000..8180090
--- /dev/null
+++ b/src/sys/compat/unix/os/os_mac.c
@@ -0,0 +1,67 @@
+/*
+ * 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/syscall.h>
+#include <sys/proc.h>
+#include <sys/errno.h>
+#include <sys/types.h>
+#include <os/mac.h>
+#include <compat/unix/syscall.h>
+
+/*
+ * ARG0: Border ID (BORDER_*)
+ * ARG1: Length requested
+ * ARG2: Offset requested
+ * ARG3: Flags
+ * ARG4: Result
+ */
+scret_t
+sys_cross(struct syscall_args *scargs)
+{
+    border_id_t bd = SCARG(scargs, border_id_t, 0);
+    size_t len = SCARG(scargs, size_t, 1);
+    off_t off = SCARG(scargs, off_t, 2);
+    int flags = SCARG(scargs, int, 3);
+    void **res = SCARG(scargs, void **, 4);
+    struct mac_border *bop;
+    struct proc *self = proc_self();
+    int error;
+
+    error = proc_check_addr(self, (uintptr_t)res, len);
+    if (error < 0) {
+        return error;
+    }
+
+    bop = mac_get_border(bd);
+    if (bop == NULL) {
+        return -EIO;
+    }
+
+    return mac_map(bop, off, len, res, flags);
+}
diff --git a/src/sys/include/compat/unix/syscall.h b/src/sys/include/compat/unix/syscall.h
index daca2dc..a3e7257 100644
--- a/src/sys/include/compat/unix/syscall.h
+++ b/src/sys/include/compat/unix/syscall.h
@@ -35,11 +35,15 @@
 #include <sys/syscall.h>
 
 /*
- * Syscall numbers
+ * Default syscall numbers
+ *
+ * Defines marked as (mandatory) must be implemented
+ * between latches.
  */
 #define SYS_none    0x00
 #define SYS_exit    0x01
 #define SYS_write   0x02
+#define SYS_cross   0x03    /* cross a border (mandatory) */
 
 /*
  * Exit the current process - exit(2) syscall
@@ -51,11 +55,17 @@ scret_t sys_exit(struct syscall_args *scargs);
  */
 scret_t sys_write(struct syscall_args *scargs);
 
+/*
+ * Cross a resource border - L5 mandatory
+ */
+scret_t sys_cross(struct syscall_args *scargs);
+
 #ifdef _NEED_UNIX_SCTAB
 scret_t(*g_unix_sctab[])(struct syscall_args *) = {
     [SYS_none]   = NULL,
     [SYS_exit]   = sys_exit,
-    [SYS_write]  = sys_write
+    [SYS_write]  = sys_write,
+    [SYS_cross]  = sys_cross
 };
 
 #endif  /* !_NEED_UNIX_SCTAB */
diff --git a/src/sys/include/io/video/fbdev.h b/src/sys/include/io/video/fbdev.h
new file mode 100644
index 0000000..0502d46
--- /dev/null
+++ b/src/sys/include/io/video/fbdev.h
@@ -0,0 +1,37 @@
+/*
+ * 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.
+ */
+
+#ifndef _VIDEO_FBDEV_H_
+#define _VIDEO_FBDEV_H_
+
+#include <os/mac.h>
+
+extern struct mac_border g_fbdev_border;
+
+#endif  /* !_VIDEO_FBDEV_H_ */
diff --git a/src/sys/include/os/mac.h b/src/sys/include/os/mac.h
new file mode 100644
index 0000000..dbc09eb
--- /dev/null
+++ b/src/sys/include/os/mac.h
@@ -0,0 +1,132 @@
+/*
+ * 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.
+ */
+
+#ifndef _OS_MAC_H_
+#define _OS_MAC_H_ 1
+
+#include <sys/types.h>
+
+/* Forward declarations */
+struct mac_border;
+struct proc;
+
+typedef enum {
+    BORDER_NONE,
+    BORDER_FBDEV,
+    __BORDER_MAX
+} border_id_t;
+
+/*
+ * MAC levels
+ *
+ * Processes or users with lower levels cannot
+ * access higher levels, higher levels can access
+ * lower levels.
+ */
+typedef enum {
+    MAC_GLOBAL,
+    MAC_RESTRICTED,
+    MAC_SECRET
+} mac_level_t;
+
+/*
+ * Mapping arguments for MAC
+ *
+ * @off: Mapping offset
+ * @len: Mapping length
+ * @flags: Optional flags
+ * @dp_res: Data pointer result written here
+ */
+struct mac_map_args {
+    off_t off;
+    size_t len;
+    int flags;
+    void **dp_res;
+};
+
+/*
+ * MAC operation hooks
+ *
+ * @map: Map a resource, return length
+ * @sync: Sync resource with driver
+ * @getattr: Get attributes of resource
+ */
+struct mac_ops {
+    ssize_t(*map)(struct mac_border *mbp, struct mac_map_args *args);
+    int(*sync)(struct mac_border *mbp, int flags);
+    int(*getattr)(struct mac_border *mbp, void *p, size_t len);
+};
+
+/*
+ * A MAC border sits inbetween a resource and the user
+ * and controls if they can access it or not.
+ */
+struct mac_border {
+    mac_level_t level;
+    struct mac_ops *ops;
+};
+
+/*
+ * Check creds with a specific process and a specific
+ * resource border.
+ *
+ * @procp: Process to check with border
+ * @mbp: Border to 'procp' is trying to access
+ *
+ * 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);
+
+/*
+ * Map a resource into process address space by
+ * going through its border
+ *
+ * @mbp: Border of resource
+ * @off: Offset of mapping to make
+ * @len: Length of mapping to make
+ * @res: Result pointer is written here
+ * @flags: Optional flags
+ *
+ * Returns zero on success, otherwise a less than zero value
+ * on failure.
+ */
+int mac_map(struct mac_border *mbp, off_t off, size_t len, void **res, int flags);
+
+/*
+ * Acquire a specific border using an ID
+ *
+ * @id: ID to lookup
+ *
+ * Returns the pointer pointer on success, otherwise a NULL
+ * value on failure.
+ */
+struct mac_border *mac_get_border(border_id_t id);
+
+#endif  /* !_OS_MAC_H_ */
diff --git a/src/sys/include/sys/proc.h b/src/sys/include/sys/proc.h
index 6a356ef..43772be 100644
--- a/src/sys/include/sys/proc.h
+++ b/src/sys/include/sys/proc.h
@@ -35,6 +35,7 @@
 #include <sys/cdefs.h>
 #include <sys/param.h>
 #include <sys/queue.h>
+#include <os/mac.h>
 #include <vm/vm.h>
 #include <machine/pcb.h>    /* standard */
 
@@ -53,6 +54,7 @@
  * @flags: State flags (see PROC_*)
  * @pcb: Process control block
  * @scdom: Syscall domain
+ * @level: Access level
  * @maplist: List of mapped regions
  * @link: TAILQ link
  */
@@ -61,6 +63,7 @@ struct proc {
     uint32_t flags;
     struct md_pcb pcb;
     struct syscall_domain scdom;
+    mac_level_t level;
     TAILQ_HEAD(, vm_range) maplist;
     TAILQ_ENTRY(proc) link;
 };
diff --git a/src/sys/io/video/fbdev.c b/src/sys/io/video/fbdev.c
new file mode 100644
index 0000000..51abea3
--- /dev/null
+++ b/src/sys/io/video/fbdev.c
@@ -0,0 +1,92 @@
+/*
+ * 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/bootvars.h>
+#include <sys/proc.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <io/video/fbdev.h>
+#include <vm/map.h>
+#include <vm/mmu.h>
+
+/*
+ * Map the framebuffer, we'll decided how many bytes
+ * is mapped.
+ */
+static ssize_t
+fbdev_map(struct mac_border *mbp, struct mac_map_args *args)
+{
+    int prot = PROT_READ | PROT_WRITE | PROT_USER;
+    size_t max_size = 0;
+    struct bootvars bv;
+    struct proc *self = proc_self();
+    struct vm_vas vas;
+    struct bootvar_fb *fbvar;
+    struct mmu_map spec;
+    int error;
+
+    /* Grab the bootvars */
+    error = bootvars_read(&bv, 0);
+    if (error < 0) {
+        return error;
+    }
+
+    /* Grab the current VAS for mapping */
+    error = mmu_this_vas(&vas);
+    if (error < 0) {
+        return error;
+    }
+
+    fbvar = &bv.fbvars;
+    max_size = fbvar->width * fbvar->pitch;
+    if (args->len > max_size) {
+        args->len = max_size;
+    }
+
+    spec.pa = VIRT_TO_PHYS(fbvar->io);
+    spec.va = spec.pa;
+    error = vm_map(&vas, &spec, args->len, prot);
+    if (error < 0) {
+        return error;
+    }
+
+    *args->dp_res = (void *)VIRT_TO_PHYS(fbvar->io);
+    return args->len;
+}
+
+static struct mac_ops ops = {
+    .map = fbdev_map,
+    .sync = NULL,
+    .getattr = NULL
+};
+
+struct mac_border g_fbdev_border = {
+    .level = MAC_RESTRICTED,
+    .ops = &ops
+};
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];
+}