248 lines
6.7 KiB
C
248 lines
6.7 KiB
C
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/*
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* AppArmor security module
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*
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* This file contains AppArmor function for pathnames
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*
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* Copyright (C) 1998-2008 Novell/SUSE
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* Copyright 2009-2010 Canonical Ltd.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*/
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#include <linux/magic.h>
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#include <linux/mount.h>
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#include <linux/namei.h>
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#include <linux/nsproxy.h>
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#include <linux/path.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/fs_struct.h>
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#include "include/apparmor.h"
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#include "include/path.h"
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#include "include/policy.h"
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/* modified from dcache.c */
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static int prepend(char **buffer, int buflen, const char *str, int namelen)
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{
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buflen -= namelen;
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if (buflen < 0)
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return -ENAMETOOLONG;
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*buffer -= namelen;
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memcpy(*buffer, str, namelen);
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return 0;
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}
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#define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT)
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/* If the path is not connected to the expected root,
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* check if it is a sysctl and handle specially else remove any
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* leading / that __d_path may have returned.
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* Unless
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* specifically directed to connect the path,
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* OR
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* if in a chroot and doing chroot relative paths and the path
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* resolves to the namespace root (would be connected outside
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* of chroot) and specifically directed to connect paths to
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* namespace root.
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*/
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static int disconnect(const struct path *path, char *buf, char **name,
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int flags)
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{
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int error = 0;
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if (!(flags & PATH_CONNECT_PATH) &&
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!(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) &&
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our_mnt(path->mnt))) {
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/* disconnected path, don't return pathname starting
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* with '/'
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*/
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error = -EACCES;
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if (**name == '/')
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*name = *name + 1;
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} else if (**name != '/')
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/* CONNECT_PATH with missing root */
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error = prepend(name, *name - buf, "/", 1);
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return error;
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}
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/**
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* d_namespace_path - lookup a name associated with a given path
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* @path: path to lookup (NOT NULL)
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* @buf: buffer to store path to (NOT NULL)
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* @buflen: length of @buf
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* @name: Returns - pointer for start of path name with in @buf (NOT NULL)
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* @flags: flags controlling path lookup
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*
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* Handle path name lookup.
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*
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* Returns: %0 else error code if path lookup fails
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* When no error the path name is returned in @name which points to
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* to a position in @buf
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*/
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static int d_namespace_path(const struct path *path, char *buf, int buflen,
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char **name, int flags)
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{
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char *res;
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int error = 0;
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int connected = 1;
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if (path->mnt->mnt_flags & MNT_INTERNAL) {
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/* it's not mounted anywhere */
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res = dentry_path(path->dentry, buf, buflen);
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*name = res;
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if (IS_ERR(res)) {
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*name = buf;
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return PTR_ERR(res);
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}
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if (path->dentry->d_sb->s_magic == PROC_SUPER_MAGIC &&
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strncmp(*name, "/sys/", 5) == 0) {
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/* TODO: convert over to using a per namespace
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* control instead of hard coded /proc
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*/
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return prepend(name, *name - buf, "/proc", 5);
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} else
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return disconnect(path, buf, name, flags);
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return 0;
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}
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/* resolve paths relative to chroot?*/
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if (flags & PATH_CHROOT_REL) {
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struct path root;
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get_fs_root(current->fs, &root);
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res = __d_path(path, &root, buf, buflen);
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path_put(&root);
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} else {
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res = d_absolute_path(path, buf, buflen);
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if (!our_mnt(path->mnt))
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connected = 0;
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}
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/* handle error conditions - and still allow a partial path to
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* be returned.
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*/
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if (!res || IS_ERR(res)) {
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if (PTR_ERR(res) == -ENAMETOOLONG)
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return -ENAMETOOLONG;
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connected = 0;
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res = dentry_path_raw(path->dentry, buf, buflen);
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if (IS_ERR(res)) {
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error = PTR_ERR(res);
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*name = buf;
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goto out;
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};
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} else if (!our_mnt(path->mnt))
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connected = 0;
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*name = res;
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/* Handle two cases:
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* 1. A deleted dentry && profile is not allowing mediation of deleted
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* 2. On some filesystems, newly allocated dentries appear to the
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* security_path hooks as a deleted dentry except without an inode
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* allocated.
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*/
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if (d_unlinked(path->dentry) && d_is_positive(path->dentry) &&
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!(flags & PATH_MEDIATE_DELETED)) {
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error = -ENOENT;
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goto out;
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}
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if (!connected)
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error = disconnect(path, buf, name, flags);
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out:
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return error;
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}
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/**
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* get_name_to_buffer - get the pathname to a buffer ensure dir / is appended
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* @path: path to get name for (NOT NULL)
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* @flags: flags controlling path lookup
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* @buffer: buffer to put name in (NOT NULL)
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* @size: size of buffer
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* @name: Returns - contains position of path name in @buffer (NOT NULL)
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*
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* Returns: %0 else error on failure
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*/
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static int get_name_to_buffer(const struct path *path, int flags, char *buffer,
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int size, char **name, const char **info)
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{
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int adjust = (flags & PATH_IS_DIR) ? 1 : 0;
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int error = d_namespace_path(path, buffer, size - adjust, name, flags);
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if (!error && (flags & PATH_IS_DIR) && (*name)[1] != '\0')
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/*
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* Append "/" to the pathname. The root directory is a special
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* case; it already ends in slash.
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*/
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strcpy(&buffer[size - 2], "/");
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if (info && error) {
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if (error == -ENOENT)
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*info = "Failed name lookup - deleted entry";
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else if (error == -EACCES)
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*info = "Failed name lookup - disconnected path";
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else if (error == -ENAMETOOLONG)
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*info = "Failed name lookup - name too long";
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else
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*info = "Failed name lookup";
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}
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return error;
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}
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/**
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* aa_path_name - compute the pathname of a file
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* @path: path the file (NOT NULL)
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* @flags: flags controlling path name generation
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* @buffer: buffer that aa_get_name() allocated (NOT NULL)
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* @name: Returns - the generated path name if !error (NOT NULL)
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* @info: Returns - information on why the path lookup failed (MAYBE NULL)
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*
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* @name is a pointer to the beginning of the pathname (which usually differs
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* from the beginning of the buffer), or NULL. If there is an error @name
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* may contain a partial or invalid name that can be used for audit purposes,
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* but it can not be used for mediation.
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*
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* We need PATH_IS_DIR to indicate whether the file is a directory or not
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* because the file may not yet exist, and so we cannot check the inode's
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* file type.
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*
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* Returns: %0 else error code if could retrieve name
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*/
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int aa_path_name(const struct path *path, int flags, char **buffer,
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const char **name, const char **info)
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{
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char *buf, *str = NULL;
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int size = 256;
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int error;
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*name = NULL;
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*buffer = NULL;
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for (;;) {
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/* freed by caller */
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buf = kmalloc(size, GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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error = get_name_to_buffer(path, flags, buf, size, &str, info);
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if (error != -ENAMETOOLONG)
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break;
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kfree(buf);
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size <<= 1;
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if (size > aa_g_path_max)
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return -ENAMETOOLONG;
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*info = NULL;
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}
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*buffer = buf;
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*name = str;
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return error;
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}
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