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 } 222