[TOMOYO #16 15/25] TOMOYO: Add mount restriction.

[Tetsuo Handa]

This patch contains code for checking mount operations.

Checking mount operations is a part of checking file operations, but the code
is separated from file access because the code is complicated.

Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
 security/tomoyo/mount.c |  366 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 366 insertions(+)

--- /dev/null
+++ security-testing-2.6/security/tomoyo/mount.c
@@ -0,0 +1,366 @@
+/*
+ * security/tomoyo/mount.c
+ *
+ * Copyright (C) 2005-2009  NTT DATA CORPORATION
+ */
+#include "internal.h"
+
+/* Keywords for mount restrictions. */
+
+/* Allow to call 'mount --bind /source_dir /dest_dir' */
+#define TOMOYO_MOUNT_BIND_KEYWORD                           "--bind"
+/* Allow to call 'mount --move /old_dir    /new_dir ' */
+#define TOMOYO_MOUNT_MOVE_KEYWORD                           "--move"
+/* Allow to call 'mount -o remount /dir             ' */
+#define TOMOYO_MOUNT_REMOUNT_KEYWORD                        "--remount"
+/* Allow to call 'mount --make-unbindable /dir'       */
+#define TOMOYO_MOUNT_MAKE_UNBINDABLE_KEYWORD                "--make-unbindable"
+/* Allow to call 'mount --make-private /dir'          */
+#define TOMOYO_MOUNT_MAKE_PRIVATE_KEYWORD                   "--make-private"
+/* Allow to call 'mount --make-slave /dir'            */
+#define TOMOYO_MOUNT_MAKE_SLAVE_KEYWORD                     "--make-slave"
+/* Allow to call 'mount --make-shared /dir'           */
+#define TOMOYO_MOUNT_MAKE_SHARED_KEYWORD                    "--make-shared"
+
+/**
+ * tomoyo_audit_mount_log - Audit mount log.
+ *
+ * @r:          Pointer to "struct tomoyo_request_info".
+ * @dev_name:   Device file.
+ * @dir_name:   Mount point.
+ * @type:       Filesystem type.
+ * @flags:      Mount flags.
+ * @is_granted: True if this is a granted log.
+ *
+ * Returns 0 on success, negative value otherwise.
+ */
+static int tomoyo_audit_mount_log(struct tomoyo_request_info *r,
+				  const char *dev_name, const char *dir_name,
+				  const char *type, const unsigned long flags,
+				  const bool is_granted)
+{
+	if (!is_granted) {
+		if (!strcmp(type, TOMOYO_MOUNT_REMOUNT_KEYWORD))
+			tomoyo_warn_log(r, "mount -o remount %s 0x%lX",
+					dir_name, flags);
+		else if (!strcmp(type, TOMOYO_MOUNT_BIND_KEYWORD)
+			 || !strcmp(type, TOMOYO_MOUNT_MOVE_KEYWORD))
+			tomoyo_warn_log(r, "mount %s %s %s 0x%lX", type,
+					dev_name, dir_name, flags);
+		else if (!strcmp(type, TOMOYO_MOUNT_MAKE_UNBINDABLE_KEYWORD) ||
+			 !strcmp(type, TOMOYO_MOUNT_MAKE_PRIVATE_KEYWORD) ||
+			 !strcmp(type, TOMOYO_MOUNT_MAKE_SLAVE_KEYWORD) ||
+			 !strcmp(type, TOMOYO_MOUNT_MAKE_SHARED_KEYWORD))
+			tomoyo_warn_log(r, "mount %s %s 0x%lX", type, dir_name,
+					flags);
+		else
+			tomoyo_warn_log(r, "mount -t %s %s %s 0x%lX", type,
+					dev_name, dir_name, flags);
+	}
+	return tomoyo_write_audit_log(is_granted, r, TOMOYO_KEYWORD_ALLOW_MOUNT
+				      "%s %s %s 0x%lu\n", dev_name, dir_name,
+				      type, flags);
+}
+
+/**
+ * tomoyo_mount_acl2 - Check permission for mount() operation.
+ *
+ * @r:        Pointer to "struct tomoyo_request_info".
+ * @dev_name: Name of device file.
+ * @dir:      Pointer to "struct path".
+ * @type:     Name of filesystem type.
+ * @flags:    Mount options.
+ *
+ * Returns 0 on success, negative value otherwise.
+ *
+ * Caller holds tomoyo_read_lock().
+ */
+static int tomoyo_mount_acl2(struct tomoyo_request_info *r, char *dev_name,
+			     struct path *dir, char *type, unsigned long flags)
+{
+	struct tomoyo_obj_info obj = { };
+	struct path path;
+	struct tomoyo_acl_info *ptr;
+	struct file_system_type *fstype = NULL;
+	const char *requested_type = NULL;
+	const char *requested_dir_name = NULL;
+	const char *requested_dev_name = NULL;
+	struct tomoyo_path_info rtype;
+	struct tomoyo_path_info rdev;
+	struct tomoyo_path_info rdir;
+	int need_dev = 0;
+	int error = -ENOMEM;
+	r->obj = &obj;
+
+	/* Get fstype. */
+	requested_type = tomoyo_encode(type);
+	if (!requested_type)
+		goto out;
+	rtype.name = requested_type;
+	tomoyo_fill_path_info(&rtype);
+
+	/* Get mount point. */
+	obj.path2 = *dir;
+	requested_dir_name = tomoyo_realpath_from_path(dir);
+	if (!requested_dir_name) {
+		error = -ENOMEM;
+		goto out;
+	}
+	rdir.name = requested_dir_name;
+	tomoyo_fill_path_info(&rdir);
+
+	/* Compare fs name. */
+	if (!strcmp(type, TOMOYO_MOUNT_REMOUNT_KEYWORD)) {
+		/* dev_name is ignored. */
+	} else if (!strcmp(type, TOMOYO_MOUNT_MAKE_UNBINDABLE_KEYWORD) ||
+		   !strcmp(type, TOMOYO_MOUNT_MAKE_PRIVATE_KEYWORD) ||
+		   !strcmp(type, TOMOYO_MOUNT_MAKE_SLAVE_KEYWORD) ||
+		   !strcmp(type, TOMOYO_MOUNT_MAKE_SHARED_KEYWORD)) {
+		/* dev_name is ignored. */
+	} else if (!strcmp(type, TOMOYO_MOUNT_BIND_KEYWORD) ||
+		   !strcmp(type, TOMOYO_MOUNT_MOVE_KEYWORD)) {
+		need_dev = -1; /* dev_name is a directory */
+	} else {
+		fstype = get_fs_type(type);
+		if (!fstype) {
+			error = -ENODEV;
+			goto out;
+		}
+		if (fstype->fs_flags & FS_REQUIRES_DEV)
+			/* dev_name is a block device file. */
+			need_dev = 1;
+	}
+	if (need_dev) {
+		/* Get mount point or device file. */
+		if (tomoyo_get_path(dev_name, &path)) {
+			error = -ENOENT;
+			goto out;
+		}
+		obj.path1 = path;
+		requested_dev_name = tomoyo_realpath_from_path(&path);
+		if (!requested_dev_name) {
+			error = -ENOENT;
+			goto out;
+		}
+	} else {
+		/* Map dev_name to "<NULL>" if no dev_name given. */
+		if (!dev_name)
+			dev_name = "<NULL>";
+		requested_dev_name = tomoyo_encode(dev_name);
+		if (!requested_dev_name) {
+			error = -ENOMEM;
+			goto out;
+		}
+	}
+	rdev.name = requested_dev_name;
+	tomoyo_fill_path_info(&rdev);
+	list_for_each_entry_rcu(ptr, &r->domain->acl_info_list, list) {
+		struct tomoyo_mount_acl *acl;
+		if (ptr->is_deleted || ptr->type != TOMOYO_TYPE_MOUNT_ACL)
+			continue;
+		acl = container_of(ptr, struct tomoyo_mount_acl,
+				   head);
+		if (!tomoyo_compare_number_union(flags, &acl->flags) ||
+		    !tomoyo_compare_name_union(&rtype, &acl->fs_type) ||
+		    !tomoyo_compare_name_union(&rdir, &acl->dir_name) ||
+		    (need_dev &&
+		     !tomoyo_compare_name_union(&rdev, &acl->dev_name)) ||
+		    !tomoyo_condition(r, ptr))
+			continue;
+		r->cond = ptr->cond;
+		error = 0;
+		break;
+	}
+	tomoyo_audit_mount_log(r, requested_dev_name, requested_dir_name,
+			       requested_type, flags, !error);
+	if (error)
+		error = tomoyo_supervisor(r, TOMOYO_KEYWORD_ALLOW_MOUNT
+					  "%s %s %s 0x%lX\n",
+					  tomoyo_file_pattern(&rdev),
+					  tomoyo_file_pattern(&rdir),
+					  requested_type, flags);
+ out:
+	kfree(requested_dev_name);
+	kfree(requested_dir_name);
+	if (fstype)
+		put_filesystem(fstype);
+	kfree(requested_type);
+	/* Drop refcount obtained by tomoyo_get_path(). */
+	if (obj.path1.dentry)
+		path_put(&obj.path1);
+	return error;
+}
+
+/**
+ * tomoyo_mount_acl - Check permission for mount() operation.
+ *
+ * @r:        Pointer to "struct tomoyo_request_info".
+ * @dev_name: Name of device file.
+ * @dir:      Pointer to "struct path".
+ * @type:     Name of filesystem type.
+ * @flags:    Mount options.
+ *
+ * Returns 0 on success, negative value otherwise.
+ *
+ * Caller holds tomoyo_read_lock().
+ */
+static int tomoyo_mount_acl(struct tomoyo_request_info *r, char *dev_name,
+			    struct path *dir, char *type, unsigned long flags)
+{
+	int error;
+	error = -EPERM;
+	if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
+		flags &= ~MS_MGC_MSK;
+	switch (flags & (MS_REMOUNT | MS_MOVE | MS_BIND)) {
+	case MS_REMOUNT:
+	case MS_MOVE:
+	case MS_BIND:
+	case 0:
+		break;
+	default:
+		printk(KERN_WARNING "ERROR: "
+		       "%s%s%sare given for single mount operation.\n",
+		       flags & MS_REMOUNT ? "'remount' " : "",
+		       flags & MS_MOVE    ? "'move' " : "",
+		       flags & MS_BIND    ? "'bind' " : "");
+		return -EINVAL;
+	}
+	switch (flags & (MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED)) {
+	case MS_UNBINDABLE:
+	case MS_PRIVATE:
+	case MS_SLAVE:
+	case MS_SHARED:
+	case 0:
+		break;
+	default:
+		printk(KERN_WARNING "ERROR: "
+		       "%s%s%s%sare given for single mount operation.\n",
+		       flags & MS_UNBINDABLE ? "'unbindable' " : "",
+		       flags & MS_PRIVATE    ? "'private' " : "",
+		       flags & MS_SLAVE      ? "'slave' " : "",
+		       flags & MS_SHARED     ? "'shared' " : "");
+		return -EINVAL;
+	}
+	if (flags & MS_REMOUNT)
+		error = tomoyo_mount_acl(r, dev_name, dir,
+					 TOMOYO_MOUNT_REMOUNT_KEYWORD,
+					 flags & ~MS_REMOUNT);
+	else if (flags & MS_MOVE)
+		error = tomoyo_mount_acl(r, dev_name, dir,
+					 TOMOYO_MOUNT_MOVE_KEYWORD,
+					 flags & ~MS_MOVE);
+	else if (flags & MS_BIND)
+		error = tomoyo_mount_acl(r, dev_name, dir,
+					 TOMOYO_MOUNT_BIND_KEYWORD,
+					 flags & ~MS_BIND);
+	else if (flags & MS_UNBINDABLE)
+		error = tomoyo_mount_acl(r, dev_name, dir,
+					 TOMOYO_MOUNT_MAKE_UNBINDABLE_KEYWORD,
+					 flags & ~MS_UNBINDABLE);
+	else if (flags & MS_PRIVATE)
+		error = tomoyo_mount_acl(r, dev_name, dir,
+					 TOMOYO_MOUNT_MAKE_PRIVATE_KEYWORD,
+					 flags & ~MS_PRIVATE);
+	else if (flags & MS_SLAVE)
+		error = tomoyo_mount_acl(r, dev_name, dir,
+					 TOMOYO_MOUNT_MAKE_SLAVE_KEYWORD,
+					 flags & ~MS_SLAVE);
+	else if (flags & MS_SHARED)
+		error = tomoyo_mount_acl(r, dev_name, dir,
+					 TOMOYO_MOUNT_MAKE_SHARED_KEYWORD,
+					 flags & ~MS_SHARED);
+	else
+		do {
+			error = tomoyo_mount_acl2(r, dev_name, dir, type,
+						  flags);
+		} while (error == 1);
+	if (r->mode != TOMOYO_CONFIG_ENFORCING)
+		error = 0;
+	return error;
+}
+
+/**
+ * tomoyo_mount_permission - Check permission for mount() operation.
+ *
+ * @dev_name: Name of device file.
+ * @dir:      Pointer to "struct path".
+ * @type:     Name of filesystem type. May be NULL.
+ * @flags:    Mount options.
+ *
+ * Returns 0 on success, negative value otherwise.
+ */
+int tomoyo_mount_permission(char *dev_name, struct path *dir, char *type,
+			    const unsigned long flags)
+{
+	struct tomoyo_request_info r;
+	int error;
+	int idx;
+	if (!tomoyo_capable(TOMOYO_SYS_MOUNT))
+		return -EPERM;
+	if (tomoyo_init_request_info(&r, NULL, TOMOYO_MAC_FILE_MOUNT)
+	    == TOMOYO_CONFIG_DISABLED)
+		return 0;
+	if (!type)
+		type = "<NULL>";
+	idx = tomoyo_read_lock();
+	error = tomoyo_mount_acl(&r, dev_name, dir, type, flags);
+	tomoyo_read_unlock(idx);
+	return error;
+}
+
+/**
+ * tomoyo_write_mount_policy - Write "struct tomoyo_mount_acl" list.
+ *
+ * @data:      String to parse.
+ * @domain:    Pointer to "struct tomoyo_domain_info".
+ * @condition: Pointer to "struct tomoyo_condition". May be NULL.
+ * @is_delete: True if it is a delete request.
+ *
+ * Returns 0 on success, negative value otherwise.
+ */
+int tomoyo_write_mount_policy(char *data, struct tomoyo_domain_info *domain,
+			      struct tomoyo_condition *condition,
+			      const bool is_delete)
+{
+	struct tomoyo_mount_acl *entry = NULL;
+	struct tomoyo_acl_info *ptr;
+	struct tomoyo_mount_acl e = { .head.type = TOMOYO_TYPE_MOUNT_ACL,
+				      .head.cond = condition };
+	int error = is_delete ? -ENOENT : -ENOMEM;
+	char *w[4];
+	if (!tomoyo_tokenize(data, w, sizeof(w)) || !w[3][0])
+		return -EINVAL;
+	if (!tomoyo_parse_name_union(w[0], &e.dev_name) ||
+	    !tomoyo_parse_name_union(w[1], &e.dir_name) ||
+	    !tomoyo_parse_name_union(w[2], &e.fs_type) ||
+	    !tomoyo_parse_number_union(w[3], &e.flags))
+		goto out;
+	if (!is_delete)
+		entry = kmalloc(sizeof(e), GFP_KERNEL);
+	mutex_lock(&tomoyo_policy_lock);
+	list_for_each_entry_rcu(ptr, &domain->acl_info_list, list) {
+		struct tomoyo_mount_acl *acl =
+			container_of(ptr, struct tomoyo_mount_acl, head);
+		if (ptr->type != TOMOYO_TYPE_MOUNT_ACL ||
+		    ptr->cond != condition
+		    || tomoyo_memcmp(acl, &e, offsetof(typeof(e), dev_name),
+				     sizeof(e)))
+			continue;
+		ptr->is_deleted = is_delete;
+		error = 0;
+		break;
+	}
+	if (!is_delete && error && tomoyo_commit_ok(entry, &e, sizeof(e))) {
+		tomoyo_add_domain_acl(domain, &entry->head);
+		entry = NULL;
+		error = 0;
+	}
+	mutex_unlock(&tomoyo_policy_lock);
+ out:
+	tomoyo_put_name_union(&e.dev_name);
+	tomoyo_put_name_union(&e.dir_name);
+	tomoyo_put_name_union(&e.fs_type);
+	tomoyo_put_number_union(&e.flags);
+	kfree(entry);
+	return error;
+}

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