security/apparmor/path.c

   1 /*
   2  * AppArmor security module
   3  *
   4  * This file contains AppArmor function for pathnames
   5  *
   6  * Copyright (C) 1998-2008 Novell/SUSE
   7  * Copyright 2009-2010 Canonical Ltd.
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License as
  11  * published by the Free Software Foundation, version 2 of the
  12  * License.
  13  */
  14
  15 #include <linux/magic.h>
  16 #include <linux/mount.h>
  17 #include <linux/namei.h>
  18 #include <linux/nsproxy.h>
  19 #include <linux/path.h>
  20 #include <linux/sched.h>
  21 #include <linux/slab.h>
  22 #include <linux/fs_struct.h>
  23
  24 #include "include/apparmor.h"
  25 #include "include/path.h"
  26 #include "include/policy.h"
  27
  28 /* modified from dcache.c */
  29 static int prepend(char **buffer, int buflen, const char *str, int namelen)
  30 {
  31         buflen -= namelen;
  32         if (buflen < 0)
  33                 return -ENAMETOOLONG;
  34         *buffer -= namelen;
  35         memcpy(*buffer, str, namelen);
  36         return 0;
  37 }
  38
  39 #define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT)
  40
  41 /* If the path is not connected to the expected root,
  42  * check if it is a sysctl and handle specially else remove any
  43  * leading / that __d_path may have returned.
  44  * Unless
  45  *     specifically directed to connect the path,
  46  * OR
  47  *     if in a chroot and doing chroot relative paths and the path
  48  *     resolves to the namespace root (would be connected outside
  49  *     of chroot) and specifically directed to connect paths to
  50  *     namespace root.
  51  */
  52 static int disconnect(const struct path *path, char *buf, char **name,
  53                       int flags, const char *disconnected)
  54 {
  55         int error = 0;
  56
  57         if (!(flags & PATH_CONNECT_PATH) &&
  58             !(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) &&
  59               our_mnt(path->mnt))) {
  60                 /* disconnected path, don't return pathname starting
  61                  * with '/'
  62                  */
  63                 error = -EACCES;
  64                 if (**name == '/')
  65                         *name = *name + 1;
  66         } else {
  67                 if (**name != '/')
  68                         /* CONNECT_PATH with missing root */
  69                         error = prepend(name, *name - buf, "/", 1);
  70                 if (!error && disconnected)
  71                         error = prepend(name, *name - buf, disconnected,
  72                                         strlen(disconnected));
  73         }
  74
  75         return error;
  76 }
  77
  78 /**
  79  * d_namespace_path - lookup a name associated with a given path
  80  * @path: path to lookup  (NOT NULL)
  81  * @buf:  buffer to store path to  (NOT NULL)
  82  * @name: Returns - pointer for start of path name with in @buf (NOT NULL)
  83  * @flags: flags controlling path lookup
  84  * @disconnected: string to prefix to disconnected paths
  85  *
  86  * Handle path name lookup.
  87  *
  88  * Returns: %0 else error code if path lookup fails
  89  *          When no error the path name is returned in @name which points to
  90  *          to a position in @buf
  91  */
  92 static int d_namespace_path(const struct path *path, char *buf, char **name,
  93                             int flags, const char *disconnected)
  94 {
  95         char *res;
  96         int error = 0;
  97         int connected = 1;
  98         int isdir = (flags & PATH_IS_DIR) ? 1 : 0;
  99         int buflen = aa_g_path_max - isdir;
 100
 101         if (path->mnt->mnt_flags & MNT_INTERNAL) {
 102                 /* it's not mounted anywhere */
 103                 res = dentry_path(path->dentry, buf, buflen);
 104                 *name = res;
 105                 if (IS_ERR(res)) {
 106                         *name = buf;
 107                         return PTR_ERR(res);
 108                 }
 109                 if (path->dentry->d_sb->s_magic == PROC_SUPER_MAGIC &&
 110                     strncmp(*name, "/sys/", 5) == 0) {
 111                         /* TODO: convert over to using a per namespace
 112                          * control instead of hard coded /proc
 113                          */
 114                         error = prepend(name, *name - buf, "/proc", 5);
 115                         goto out;
 116                 } else
 117                         error = disconnect(path, buf, name, flags,
 118                                            disconnected);
 119                 goto out;
 120         }
 121
 122         /* resolve paths relative to chroot?*/
 123         if (flags & PATH_CHROOT_REL) {
 124                 struct path root;
 125                 get_fs_root(current->fs, &root);
 126                 res = __d_path(path, &root, buf, buflen);
 127                 path_put(&root);
 128         } else {
 129                 res = d_absolute_path(path, buf, buflen);
 130                 if (!our_mnt(path->mnt))
 131                         connected = 0;
 132         }
 133
 134         /* handle error conditions - and still allow a partial path to
 135          * be returned.
 136          */
 137         if (!res || IS_ERR(res)) {
 138                 if (PTR_ERR(res) == -ENAMETOOLONG) {
 139                         error = -ENAMETOOLONG;
 140                         *name = buf;
 141                         goto out;
 142                 }
 143                 connected = 0;
 144                 res = dentry_path_raw(path->dentry, buf, buflen);
 145                 if (IS_ERR(res)) {
 146                         error = PTR_ERR(res);
 147                         *name = buf;
 148                         goto out;
 149                 };
 150         } else if (!our_mnt(path->mnt))
 151                 connected = 0;
 152
 153         *name = res;
 154
 155         if (!connected)
 156                 error = disconnect(path, buf, name, flags, disconnected);
 157
 158         /* Handle two cases:
 159          * 1. A deleted dentry && profile is not allowing mediation of deleted
 160          * 2. On some filesystems, newly allocated dentries appear to the
 161          *    security_path hooks as a deleted dentry except without an inode
 162          *    allocated.
 163          */
 164         if (d_unlinked(path->dentry) && d_is_positive(path->dentry) &&
 165             !(flags & (PATH_MEDIATE_DELETED | PATH_DELEGATE_DELETED))) {
 166                         error = -ENOENT;
 167                         goto out;
 168         }
 169
 170 out:
 171         /*
 172          * Append "/" to the pathname.  The root directory is a special
 173          * case; it already ends in slash.
 174          */
 175         if (!error && isdir && ((*name)[1] != '\0' || (*name)[0] != '/'))
 176                 strcpy(&buf[aa_g_path_max - 2], "/");
 177
 178         return error;
 179 }
 180
 181 /**
 182  * aa_path_name - get the pathname to a buffer ensure dir / is appended
 183  * @path: path the file  (NOT NULL)
 184  * @flags: flags controlling path name generation
 185  * @buffer: buffer to put name in (NOT NULL)
 186  * @name: Returns - the generated path name if !error (NOT NULL)
 187  * @info: Returns - information on why the path lookup failed (MAYBE NULL)
 188  * @disconnected: string to prepend to disconnected paths
 189  *
 190  * @name is a pointer to the beginning of the pathname (which usually differs
 191  * from the beginning of the buffer), or NULL.  If there is an error @name
 192  * may contain a partial or invalid name that can be used for audit purposes,
 193  * but it can not be used for mediation.
 194  *
 195  * We need PATH_IS_DIR to indicate whether the file is a directory or not
 196  * because the file may not yet exist, and so we cannot check the inode's
 197  * file type.
 198  *
 199  * Returns: %0 else error code if could retrieve name
 200  */
 201 int aa_path_name(const struct path *path, int flags, char *buffer,
 202                  const char **name, const char **info, const char *disconnected)
 203 {
 204         char *str = NULL;
 205         int error = d_namespace_path(path, buffer, &str, flags, disconnected);
 206
 207         if (info && error) {
 208                 if (error == -ENOENT)
 209                         *info = "Failed name lookup - deleted entry";
 210                 else if (error == -EACCES)
 211                         *info = "Failed name lookup - disconnected path";
 212                 else if (error == -ENAMETOOLONG)
 213                         *info = "Failed name lookup - name too long";
 214                 else
 215                         *info = "Failed name lookup";
 216         }
 217
 218         *name = str;
 219
 220         return error;
 221 }