wip: linux: add landlock sandboxlandlock

1 files changed, 118 insertions, 0 deletions

diff --git a/vll_sandbox.c b/vll_sandbox.c
new file mode 100644
index 0000000..50d1dcc
--- /dev/null
+++ b/vll_sandbox.c
@@ -0,0 +1,118 @@
+/*
+ * Copyright 2026, Vincent Douillet <vincent@vdouillet.fr>
+ *
+ * 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 copyright holder 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 HOLDER 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 <linux/landlock.h>
+#include <sys/prctl.h>
+#include <sys/syscall.h>
+
+#include <fcntl.h>
+#include <stddef.h>
+
+#include "vll_sandbox.h"
+
+/*
+ * TODO add missing accesses to deny them by default.
+ * Also move inside vll_create_ruleset
+ */
+static struct landlock_ruleset_attr ruleset_attr = {
+    .handled_access_fs =
+        LANDLOCK_ACCESS_FS_WRITE_FILE |
+        LANDLOCK_ACCESS_FS_READ_FILE |
+        LANDLOCK_ACCESS_FS_READ_DIR |
+        LANDLOCK_ACCESS_FS_REMOVE_DIR |
+        LANDLOCK_ACCESS_FS_REMOVE_FILE |
+        LANDLOCK_ACCESS_FS_MAKE_DIR |
+        LANDLOCK_ACCESS_FS_MAKE_REG,
+};
+
+int
+vll_create_ruleset()
+{
+    int abi;
+
+    abi = syscall(SYS_landlock_create_ruleset, NULL, 0,
+            LANDLOCK_CREATE_RULESET_VERSION);
+    if (abi < 0)
+        return -1;
+
+    return syscall(SYS_landlock_create_ruleset, &ruleset_attr,
+            sizeof(ruleset_attr), 0);
+}
+
+int
+vll_add_rule(int ruleset_fd, const char *path, const char perm)
+{
+    int err;
+    struct landlock_path_beneath_attr path_beneath;
+
+    path_beneath.allowed_access = 0;
+    if (perm & VLL_READ)
+        path_beneath.allowed_access |= LANDLOCK_ACCESS_FS_READ_FILE |
+            LANDLOCK_ACCESS_FS_READ_DIR;
+    if (perm & VLL_WRITE)
+        path_beneath.allowed_access |= LANDLOCK_ACCESS_FS_WRITE_FILE |
+            LANDLOCK_ACCESS_FS_REMOVE_DIR | LANDLOCK_ACCESS_FS_REMOVE_FILE |
+            LANDLOCK_ACCESS_FS_MAKE_DIR | LANDLOCK_ACCESS_FS_MAKE_REG;
+
+    if (!path_beneath.allowed_access)
+        return -1;
+
+    path_beneath.parent_fd = open(path, O_CLOEXEC);
+    if (path_beneath.parent_fd < 0)
+        return -1;
+
+    err = syscall(SYS_landlock_add_rule, ruleset_fd,
+            LANDLOCK_RULE_PATH_BENEATH, &path_beneath, 0);
+    close(path_beneath.parent_fd);
+    if (err)
+        return -1;
+
+    return 0;
+}
+
+int
+vll_restrict_self(int ruleset_fd)
+{
+    int ret;
+
+    ret = 0;
+    if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+        ret = -1;
+        goto end;
+    }
+    if (syscall(SYS_landlock_restrict_self, ruleset_fd, 0)) {
+        ret = -1;
+        goto end;
+    }
+
+    end:
+    close(ruleset_fd);
+    return ret;
+}