diff options
Diffstat (limited to 'security/apparmor/path.c')
| -rw-r--r-- | security/apparmor/path.c | 235 |
1 files changed, 235 insertions, 0 deletions
diff --git a/security/apparmor/path.c b/security/apparmor/path.c new file mode 100644 index 000000000000..96bab9469d48 --- /dev/null +++ b/security/apparmor/path.c @@ -0,0 +1,235 @@ +/* + * AppArmor security module + * + * This file contains AppArmor function for pathnames + * + * Copyright (C) 1998-2008 Novell/SUSE + * Copyright 2009-2010 Canonical Ltd. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation, version 2 of the + * License. + */ + +#include <linux/magic.h> +#include <linux/mnt_namespace.h> +#include <linux/mount.h> +#include <linux/namei.h> +#include <linux/nsproxy.h> +#include <linux/path.h> +#include <linux/sched.h> +#include <linux/slab.h> +#include <linux/fs_struct.h> + +#include "include/apparmor.h" +#include "include/path.h" +#include "include/policy.h" + + +/* modified from dcache.c */ +static int prepend(char **buffer, int buflen, const char *str, int namelen) +{ + buflen -= namelen; + if (buflen < 0) + return -ENAMETOOLONG; + *buffer -= namelen; + memcpy(*buffer, str, namelen); + return 0; +} + +#define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT) + +/** + * d_namespace_path - lookup a name associated with a given path + * @path: path to lookup (NOT NULL) + * @buf: buffer to store path to (NOT NULL) + * @buflen: length of @buf + * @name: Returns - pointer for start of path name with in @buf (NOT NULL) + * @flags: flags controlling path lookup + * + * Handle path name lookup. + * + * Returns: %0 else error code if path lookup fails + * When no error the path name is returned in @name which points to + * to a position in @buf + */ +static int d_namespace_path(struct path *path, char *buf, int buflen, + char **name, int flags) +{ + struct path root, tmp; + char *res; + int deleted, connected; + int error = 0; + + /* Get the root we want to resolve too */ + if (flags & PATH_CHROOT_REL) { + /* resolve paths relative to chroot */ + read_lock(¤t->fs->lock); + root = current->fs->root; + /* released below */ + path_get(&root); + read_unlock(¤t->fs->lock); + } else { + /* resolve paths relative to namespace */ + root.mnt = current->nsproxy->mnt_ns->root; + root.dentry = root.mnt->mnt_root; + /* released below */ + path_get(&root); + } + + spin_lock(&dcache_lock); + /* There is a race window between path lookup here and the + * need to strip the " (deleted) string that __d_path applies + * Detect the race and relookup the path + * + * The stripping of (deleted) is a hack that could be removed + * with an updated __d_path + */ + do { + tmp = root; + deleted = d_unlinked(path->dentry); + res = __d_path(path, &tmp, buf, buflen); + + } while (deleted != d_unlinked(path->dentry)); + spin_unlock(&dcache_lock); + + *name = res; + /* handle error conditions - and still allow a partial path to + * be returned. + */ + if (IS_ERR(res)) { + error = PTR_ERR(res); + *name = buf; + goto out; + } + if (deleted) { + /* On some filesystems, newly allocated dentries appear to the + * security_path hooks as a deleted dentry except without an + * inode allocated. + * + * Remove the appended deleted text and return as string for + * normal mediation, or auditing. The (deleted) string is + * guaranteed to be added in this case, so just strip it. + */ + buf[buflen - 11] = 0; /* - (len(" (deleted)") +\0) */ + + if (path->dentry->d_inode && !(flags & PATH_MEDIATE_DELETED)) { + error = -ENOENT; + goto out; + } + } + + /* Determine if the path is connected to the expected root */ + connected = tmp.dentry == root.dentry && tmp.mnt == root.mnt; + + /* If the path is not connected, + * check if it is a sysctl and handle specially else remove any + * leading / that __d_path may have returned. + * Unless + * specifically directed to connect the path, + * OR + * if in a chroot and doing chroot relative paths and the path + * resolves to the namespace root (would be connected outside + * of chroot) and specifically directed to connect paths to + * namespace root. + */ + if (!connected) { + /* is the disconnect path a sysctl? */ + if (tmp.dentry->d_sb->s_magic == PROC_SUPER_MAGIC && + strncmp(*name, "/sys/", 5) == 0) { + /* TODO: convert over to using a per namespace + * control instead of hard coded /proc + */ + error = prepend(name, *name - buf, "/proc", 5); + } else if (!(flags & PATH_CONNECT_PATH) && + !(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) && + (tmp.mnt == current->nsproxy->mnt_ns->root && + tmp.dentry == tmp.mnt->mnt_root))) { + /* disconnected path, don't return pathname starting + * with '/' + */ + error = -ESTALE; + if (*res == '/') + *name = res + 1; + } + } + +out: + path_put(&root); + + return error; +} + +/** + * get_name_to_buffer - get the pathname to a buffer ensure dir / is appended + * @path: path to get name for (NOT NULL) + * @flags: flags controlling path lookup + * @buffer: buffer to put name in (NOT NULL) + * @size: size of buffer + * @name: Returns - contains position of path name in @buffer (NOT NULL) + * + * Returns: %0 else error on failure + */ +static int get_name_to_buffer(struct path *path, int flags, char *buffer, + int size, char **name) +{ + int adjust = (flags & PATH_IS_DIR) ? 1 : 0; + int error = d_namespace_path(path, buffer, size - adjust, name, flags); + + if (!error && (flags & PATH_IS_DIR) && (*name)[1] != '\0') + /* + * Append "/" to the pathname. The root directory is a special + * case; it already ends in slash. + */ + strcpy(&buffer[size - 2], "/"); + + return error; +} + +/** + * aa_get_name - compute the pathname of a file + * @path: path the file (NOT NULL) + * @flags: flags controlling path name generation + * @buffer: buffer that aa_get_name() allocated (NOT NULL) + * @name: Returns - the generated path name if !error (NOT NULL) + * + * @name is a pointer to the beginning of the pathname (which usually differs + * from the beginning of the buffer), or NULL. If there is an error @name + * may contain a partial or invalid name that can be used for audit purposes, + * but it can not be used for mediation. + * + * We need PATH_IS_DIR to indicate whether the file is a directory or not + * because the file may not yet exist, and so we cannot check the inode's + * file type. + * + * Returns: %0 else error code if could retrieve name + */ +int aa_get_name(struct path *path, int flags, char **buffer, const char **name) +{ + char *buf, *str = NULL; + int size = 256; + int error; + + *name = NULL; + *buffer = NULL; + for (;;) { + /* freed by caller */ + buf = kmalloc(size, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + error = get_name_to_buffer(path, flags, buf, size, &str); + if (error != -ENAMETOOLONG) + break; + + kfree(buf); + size <<= 1; + if (size > aa_g_path_max) + return -ENAMETOOLONG; + } + *buffer = buf; + *name = str; + + return error; +} |