John Johansen | cdff264 | 2010-07-29 14:47:57 -0700 | [diff] [blame] | 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/mnt_namespace.h> |
| 17 | #include <linux/mount.h> |
| 18 | #include <linux/namei.h> |
| 19 | #include <linux/nsproxy.h> |
| 20 | #include <linux/path.h> |
| 21 | #include <linux/sched.h> |
| 22 | #include <linux/slab.h> |
| 23 | #include <linux/fs_struct.h> |
| 24 | |
| 25 | #include "include/apparmor.h" |
| 26 | #include "include/path.h" |
| 27 | #include "include/policy.h" |
| 28 | |
| 29 | |
| 30 | /* modified from dcache.c */ |
| 31 | static int prepend(char **buffer, int buflen, const char *str, int namelen) |
| 32 | { |
| 33 | buflen -= namelen; |
| 34 | if (buflen < 0) |
| 35 | return -ENAMETOOLONG; |
| 36 | *buffer -= namelen; |
| 37 | memcpy(*buffer, str, namelen); |
| 38 | return 0; |
| 39 | } |
| 40 | |
| 41 | #define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT) |
| 42 | |
| 43 | /** |
| 44 | * d_namespace_path - lookup a name associated with a given path |
| 45 | * @path: path to lookup (NOT NULL) |
| 46 | * @buf: buffer to store path to (NOT NULL) |
| 47 | * @buflen: length of @buf |
| 48 | * @name: Returns - pointer for start of path name with in @buf (NOT NULL) |
| 49 | * @flags: flags controlling path lookup |
| 50 | * |
| 51 | * Handle path name lookup. |
| 52 | * |
| 53 | * Returns: %0 else error code if path lookup fails |
| 54 | * When no error the path name is returned in @name which points to |
| 55 | * to a position in @buf |
| 56 | */ |
| 57 | static int d_namespace_path(struct path *path, char *buf, int buflen, |
| 58 | char **name, int flags) |
| 59 | { |
| 60 | struct path root, tmp; |
| 61 | char *res; |
| 62 | int deleted, connected; |
| 63 | int error = 0; |
| 64 | |
| 65 | /* Get the root we want to resolve too */ |
| 66 | if (flags & PATH_CHROOT_REL) { |
| 67 | /* resolve paths relative to chroot */ |
| 68 | read_lock(¤t->fs->lock); |
| 69 | root = current->fs->root; |
| 70 | /* released below */ |
| 71 | path_get(&root); |
| 72 | read_unlock(¤t->fs->lock); |
| 73 | } else { |
| 74 | /* resolve paths relative to namespace */ |
| 75 | root.mnt = current->nsproxy->mnt_ns->root; |
| 76 | root.dentry = root.mnt->mnt_root; |
| 77 | /* released below */ |
| 78 | path_get(&root); |
| 79 | } |
| 80 | |
| 81 | spin_lock(&dcache_lock); |
| 82 | /* There is a race window between path lookup here and the |
| 83 | * need to strip the " (deleted) string that __d_path applies |
| 84 | * Detect the race and relookup the path |
| 85 | * |
| 86 | * The stripping of (deleted) is a hack that could be removed |
| 87 | * with an updated __d_path |
| 88 | */ |
| 89 | do { |
| 90 | tmp = root; |
| 91 | deleted = d_unlinked(path->dentry); |
| 92 | res = __d_path(path, &tmp, buf, buflen); |
| 93 | |
| 94 | } while (deleted != d_unlinked(path->dentry)); |
| 95 | spin_unlock(&dcache_lock); |
| 96 | |
| 97 | *name = res; |
| 98 | /* handle error conditions - and still allow a partial path to |
| 99 | * be returned. |
| 100 | */ |
| 101 | if (IS_ERR(res)) { |
| 102 | error = PTR_ERR(res); |
| 103 | *name = buf; |
| 104 | goto out; |
| 105 | } |
| 106 | if (deleted) { |
| 107 | /* On some filesystems, newly allocated dentries appear to the |
| 108 | * security_path hooks as a deleted dentry except without an |
| 109 | * inode allocated. |
| 110 | * |
| 111 | * Remove the appended deleted text and return as string for |
| 112 | * normal mediation, or auditing. The (deleted) string is |
| 113 | * guaranteed to be added in this case, so just strip it. |
| 114 | */ |
| 115 | buf[buflen - 11] = 0; /* - (len(" (deleted)") +\0) */ |
| 116 | |
| 117 | if (path->dentry->d_inode && !(flags & PATH_MEDIATE_DELETED)) { |
| 118 | error = -ENOENT; |
| 119 | goto out; |
| 120 | } |
| 121 | } |
| 122 | |
| 123 | /* Determine if the path is connected to the expected root */ |
| 124 | connected = tmp.dentry == root.dentry && tmp.mnt == root.mnt; |
| 125 | |
| 126 | /* If the path is not connected, |
| 127 | * check if it is a sysctl and handle specially else remove any |
| 128 | * leading / that __d_path may have returned. |
| 129 | * Unless |
| 130 | * specifically directed to connect the path, |
| 131 | * OR |
| 132 | * if in a chroot and doing chroot relative paths and the path |
| 133 | * resolves to the namespace root (would be connected outside |
| 134 | * of chroot) and specifically directed to connect paths to |
| 135 | * namespace root. |
| 136 | */ |
| 137 | if (!connected) { |
| 138 | /* is the disconnect path a sysctl? */ |
| 139 | if (tmp.dentry->d_sb->s_magic == PROC_SUPER_MAGIC && |
| 140 | strncmp(*name, "/sys/", 5) == 0) { |
| 141 | /* TODO: convert over to using a per namespace |
| 142 | * control instead of hard coded /proc |
| 143 | */ |
| 144 | error = prepend(name, *name - buf, "/proc", 5); |
| 145 | } else if (!(flags & PATH_CONNECT_PATH) && |
| 146 | !(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) && |
| 147 | (tmp.mnt == current->nsproxy->mnt_ns->root && |
| 148 | tmp.dentry == tmp.mnt->mnt_root))) { |
| 149 | /* disconnected path, don't return pathname starting |
| 150 | * with '/' |
| 151 | */ |
| 152 | error = -ESTALE; |
| 153 | if (*res == '/') |
| 154 | *name = res + 1; |
| 155 | } |
| 156 | } |
| 157 | |
| 158 | out: |
| 159 | path_put(&root); |
| 160 | |
| 161 | return error; |
| 162 | } |
| 163 | |
| 164 | /** |
| 165 | * get_name_to_buffer - get the pathname to a buffer ensure dir / is appended |
| 166 | * @path: path to get name for (NOT NULL) |
| 167 | * @flags: flags controlling path lookup |
| 168 | * @buffer: buffer to put name in (NOT NULL) |
| 169 | * @size: size of buffer |
| 170 | * @name: Returns - contains position of path name in @buffer (NOT NULL) |
| 171 | * |
| 172 | * Returns: %0 else error on failure |
| 173 | */ |
| 174 | static int get_name_to_buffer(struct path *path, int flags, char *buffer, |
| 175 | int size, char **name) |
| 176 | { |
| 177 | int adjust = (flags & PATH_IS_DIR) ? 1 : 0; |
| 178 | int error = d_namespace_path(path, buffer, size - adjust, name, flags); |
| 179 | |
| 180 | if (!error && (flags & PATH_IS_DIR) && (*name)[1] != '\0') |
| 181 | /* |
| 182 | * Append "/" to the pathname. The root directory is a special |
| 183 | * case; it already ends in slash. |
| 184 | */ |
| 185 | strcpy(&buffer[size - 2], "/"); |
| 186 | |
| 187 | return error; |
| 188 | } |
| 189 | |
| 190 | /** |
| 191 | * aa_get_name - compute the pathname of a file |
| 192 | * @path: path the file (NOT NULL) |
| 193 | * @flags: flags controlling path name generation |
| 194 | * @buffer: buffer that aa_get_name() allocated (NOT NULL) |
| 195 | * @name: Returns - the generated path name if !error (NOT NULL) |
| 196 | * |
| 197 | * @name is a pointer to the beginning of the pathname (which usually differs |
| 198 | * from the beginning of the buffer), or NULL. If there is an error @name |
| 199 | * may contain a partial or invalid name that can be used for audit purposes, |
| 200 | * but it can not be used for mediation. |
| 201 | * |
| 202 | * We need PATH_IS_DIR to indicate whether the file is a directory or not |
| 203 | * because the file may not yet exist, and so we cannot check the inode's |
| 204 | * file type. |
| 205 | * |
| 206 | * Returns: %0 else error code if could retrieve name |
| 207 | */ |
| 208 | int aa_get_name(struct path *path, int flags, char **buffer, const char **name) |
| 209 | { |
| 210 | char *buf, *str = NULL; |
| 211 | int size = 256; |
| 212 | int error; |
| 213 | |
| 214 | *name = NULL; |
| 215 | *buffer = NULL; |
| 216 | for (;;) { |
| 217 | /* freed by caller */ |
| 218 | buf = kmalloc(size, GFP_KERNEL); |
| 219 | if (!buf) |
| 220 | return -ENOMEM; |
| 221 | |
| 222 | error = get_name_to_buffer(path, flags, buf, size, &str); |
| 223 | if (error != -ENAMETOOLONG) |
| 224 | break; |
| 225 | |
| 226 | kfree(buf); |
| 227 | size <<= 1; |
| 228 | if (size > aa_g_path_max) |
| 229 | return -ENAMETOOLONG; |
| 230 | } |
| 231 | *buffer = buf; |
| 232 | *name = str; |
| 233 | |
| 234 | return error; |
| 235 | } |