security/tomoyo/mount.c

/*
 * security/tomoyo/mount.c
 *
 * Copyright (C) 2005-2010  NTT DATA CORPORATION
 */

#include <linux/slab.h>
#include "common.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_encode2: Encode binary string to ascii string.
 *
 * @str: String in binary format.
 *
 * Returns pointer to @str in ascii format on success, NULL otherwise.
 *
 * This function uses kzalloc(), so caller must kfree() if this function
 * didn't return NULL.
 */
static char *tomoyo_encode2(const char *str)
{
	int len = 0;
	const char *p = str;
	char *cp;
	char *cp0;
	if (!p)
		return NULL;
	while (*p) {
		const unsigned char c = *p++;
		if (c == '\\')
			len += 2;
		else if (c > ' ' && c < 127)
			len++;
		else
			len += 4;
	}
	len++;
	/* Reserve space for appending "/". */
	cp = kzalloc(len + 10, GFP_NOFS);
	if (!cp)
		return NULL;
	cp0 = cp;
	p = str;
	while (*p) {
		const unsigned char c = *p++;
		if (c == '\\') {
			*cp++ = '\\';
			*cp++ = '\\';
		} else if (c > ' ' && c < 127) {
			*cp++ = c;
		} else {
			*cp++ = '\\';
			*cp++ = (c >> 6) + '0';
			*cp++ = ((c >> 3) & 7) + '0';
			*cp++ = (c & 7) + '0';
		}
	}
	return cp0;
}

/**
 * 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 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;

	/* Get fstype. */
	requested_type = tomoyo_encode2(type);
	if (!requested_type)
		goto out;
	rtype.name = requested_type;
	tomoyo_fill_path_info(&rtype);

	/* Get mount point. */
	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 (kern_path(dev_name, LOOKUP_FOLLOW, &path)) {
			error = -ENOENT;
			goto out;
		}
		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_encode2(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->type != TOMOYO_TYPE_MOUNT_ACL)
			continue;
		acl = container_of(ptr, struct tomoyo_mount_acl, head);
		if (acl->is_deleted ||
		    !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)))
			continue;
		error = 0;
		break;
	}
	if (error) {
		const char *dev = tomoyo_get_file_pattern(&rdev)->name;
		const char *dir = tomoyo_get_file_pattern(&rdir)->name;
		int len = strlen(dev) + strlen(dir) + strlen(requested_type)
			+ 64;
		char *buf = kzalloc(len, GFP_NOFS);
		if (buf) {
			snprintf(buf, len - 1, "%s %s %s 0x%lX",
				 dev, dir, requested_type, flags);
			tomoyo_write_mount_policy(buf, r->domain, false);
			kfree(buf);
		}
	}
 out:
	kfree(requested_dev_name);
	kfree(requested_dir_name);
	if (fstype)
		put_filesystem(fstype);
	kfree(requested_type);
	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
		error = tomoyo_mount_acl2(r, dev_name, dir, type, flags);
	if (r->mode != TOMOYO_CONFIG_ENFORCING)
		error = 0;
	return error;
}

/**
 * tomoyo_mount_permission - Check permission for mount() operation.
 *
 * @dev_name:  Name of device file.
 * @path:      Pointer to "struct path".
 * @type:      Name of filesystem type. May be NULL.
 * @flags:     Mount options.
 * @data_page: Optional data. May be NULL.
 *
 * Returns 0 on success, negative value otherwise.
 */
int tomoyo_mount_permission(char *dev_name, struct path *path, char *type,
			    unsigned long flags, void *data_page)
{
	struct tomoyo_request_info r;
	int error;
	int idx;

	if (tomoyo_init_request_info(&r, NULL) == TOMOYO_CONFIG_DISABLED)
		return 0;
	if (!type)
		type = "<NULL>";
	idx = tomoyo_read_lock();
	error = tomoyo_mount_acl(&r, dev_name, path, 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".
 * @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,
			      const bool is_delete)
{
	struct tomoyo_acl_info *ptr;
	struct tomoyo_mount_acl e = { .head.type = TOMOYO_TYPE_MOUNT_ACL };
	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 (mutex_lock_interruptible(&tomoyo_policy_lock))
		goto out;
	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 (!tomoyo_is_same_mount_acl(acl, &e))
			continue;
		acl->is_deleted = is_delete;
		error = 0;
		break;
	}
	if (!is_delete && error) {
		struct tomoyo_mount_acl *entry =
			tomoyo_commit_ok(&e, sizeof(e));
		if (entry) {
			list_add_tail_rcu(&entry->head.list,
					  &domain->acl_info_list);
			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);
	return error;
}