security/tomoyo/realpath.c

   1 /*
   2  * security/tomoyo/realpath.c
   3  *
   4  * Copyright (C) 2005-2011  NTT DATA CORPORATION
   5  */
   6
   7 #include <linux/types.h>
   8 #include <linux/mount.h>
   9 #include <linux/mnt_namespace.h>
  10 #include <linux/fs_struct.h>
  11 #include <linux/magic.h>
  12 #include <linux/slab.h>
  13 #include <net/sock.h>
  14 #include "common.h"
  15 #include "../../fs/internal.h"
  16
  17 /**
  18  * tomoyo_encode: Convert binary string to ascii string.
  19  *
  20  * @str: String in binary format.
  21  *
  22  * Returns pointer to @str in ascii format on success, NULL otherwise.
  23  *
  24  * This function uses kzalloc(), so caller must kfree() if this function
  25  * didn't return NULL.
  26  */
  27 char *tomoyo_encode(const char *str)
  28 {
  29         int len = 0;
  30         const char *p = str;
  31         char *cp;
  32         char *cp0;
  33
  34         if (!p)
  35                 return NULL;
  36         while (*p) {
  37                 const unsigned char c = *p++;
  38                 if (c == '\\')
  39                         len += 2;
  40                 else if (c > ' ' && c < 127)
  41                         len++;
  42                 else
  43                         len += 4;
  44         }
  45         len++;
  46         /* Reserve space for appending "/". */
  47         cp = kzalloc(len + 10, GFP_NOFS);
  48         if (!cp)
  49                 return NULL;
  50         cp0 = cp;
  51         p = str;
  52         while (*p) {
  53                 const unsigned char c = *p++;
  54
  55                 if (c == '\\') {
  56                         *cp++ = '\\';
  57                         *cp++ = '\\';
  58                 } else if (c > ' ' && c < 127) {
  59                         *cp++ = c;
  60                 } else {
  61                         *cp++ = '\\';
  62                         *cp++ = (c >> 6) + '0';
  63                         *cp++ = ((c >> 3) & 7) + '0';
  64                         *cp++ = (c & 7) + '0';
  65                 }
  66         }
  67         return cp0;
  68 }
  69
  70 /**
  71  * tomoyo_get_absolute_path - Get the path of a dentry but ignores chroot'ed root.
  72  *
  73  * @path:   Pointer to "struct path".
  74  * @buffer: Pointer to buffer to return value in.
  75  * @buflen: Sizeof @buffer.
  76  *
  77  * Returns the buffer on success, an error code otherwise.
  78  *
  79  * If dentry is a directory, trailing '/' is appended.
  80  */
  81 static char *tomoyo_get_absolute_path(struct path *path, char * const buffer,
  82                                       const int buflen)
  83 {
  84         char *pos = ERR_PTR(-ENOMEM);
  85         if (buflen >= 256) {
  86                 struct path ns_root = { };
  87                 /* go to whatever namespace root we are under */
  88                 pos = __d_path(path, &ns_root, buffer, buflen - 1);
  89                 if (!IS_ERR(pos) && *pos == '/' && pos[1]) {
  90                         struct inode *inode = path->dentry->d_inode;
  91                         if (inode && S_ISDIR(inode->i_mode)) {
  92                                 buffer[buflen - 2] = '/';
  93                                 buffer[buflen - 1] = '\0';
  94                         }
  95                 }
  96         }
  97         return pos;
  98 }
  99
 100 /**
 101  * tomoyo_get_dentry_path - Get the path of a dentry.
 102  *
 103  * @dentry: Pointer to "struct dentry".
 104  * @buffer: Pointer to buffer to return value in.
 105  * @buflen: Sizeof @buffer.
 106  *
 107  * Returns the buffer on success, an error code otherwise.
 108  *
 109  * If dentry is a directory, trailing '/' is appended.
 110  */
 111 static char *tomoyo_get_dentry_path(struct dentry *dentry, char * const buffer,
 112                                     const int buflen)
 113 {
 114         char *pos = ERR_PTR(-ENOMEM);
 115         if (buflen >= 256) {
 116                 pos = dentry_path_raw(dentry, buffer, buflen - 1);
 117                 if (!IS_ERR(pos) && *pos == '/' && pos[1]) {
 118                         struct inode *inode = dentry->d_inode;
 119                         if (inode && S_ISDIR(inode->i_mode)) {
 120                                 buffer[buflen - 2] = '/';
 121                                 buffer[buflen - 1] = '\0';
 122                         }
 123                 }
 124         }
 125         return pos;
 126 }
 127
 128 /**
 129  * tomoyo_get_local_path - Get the path of a dentry.
 130  *
 131  * @dentry: Pointer to "struct dentry".
 132  * @buffer: Pointer to buffer to return value in.
 133  * @buflen: Sizeof @buffer.
 134  *
 135  * Returns the buffer on success, an error code otherwise.
 136  */
 137 static char *tomoyo_get_local_path(struct dentry *dentry, char * const buffer,
 138                                    const int buflen)
 139 {
 140         struct super_block *sb = dentry->d_sb;
 141         char *pos = tomoyo_get_dentry_path(dentry, buffer, buflen);
 142         if (IS_ERR(pos))
 143                 return pos;
 144         /* Convert from $PID to self if $PID is current thread. */
 145         if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') {
 146                 char *ep;
 147                 const pid_t pid = (pid_t) simple_strtoul(pos + 1, &ep, 10);
 148                 if (*ep == '/' && pid && pid ==
 149                     task_tgid_nr_ns(current, sb->s_fs_info)) {
 150                         pos = ep - 5;
 151                         if (pos < buffer)
 152                                 goto out;
 153                         memmove(pos, "/self", 5);
 154                 }
 155                 goto prepend_filesystem_name;
 156         }
 157         /* Use filesystem name for unnamed devices. */
 158         if (!MAJOR(sb->s_dev))
 159                 goto prepend_filesystem_name;
 160         {
 161                 struct inode *inode = sb->s_root->d_inode;
 162                 /*
 163                  * Use filesystem name if filesystem does not support rename()
 164                  * operation.
 165                  */
 166                 if (inode->i_op && !inode->i_op->rename)
 167                         goto prepend_filesystem_name;
 168         }
 169         /* Prepend device name. */
 170         {
 171                 char name[64];
 172                 int name_len;
 173                 const dev_t dev = sb->s_dev;
 174                 name[sizeof(name) - 1] = '\0';
 175                 snprintf(name, sizeof(name) - 1, "dev(%u,%u):", MAJOR(dev),
 176                          MINOR(dev));
 177                 name_len = strlen(name);
 178                 pos -= name_len;
 179                 if (pos < buffer)
 180                         goto out;
 181                 memmove(pos, name, name_len);
 182                 return pos;
 183         }
 184         /* Prepend filesystem name. */
 185 prepend_filesystem_name:
 186         {
 187                 const char *name = sb->s_type->name;
 188                 const int name_len = strlen(name);
 189                 pos -= name_len + 1;
 190                 if (pos < buffer)
 191                         goto out;
 192                 memmove(pos, name, name_len);
 193                 pos[name_len] = ':';
 194         }
 195         return pos;
 196 out:
 197         return ERR_PTR(-ENOMEM);
 198 }
 199
 200 /**
 201  * tomoyo_get_socket_name - Get the name of a socket.
 202  *
 203  * @path:   Pointer to "struct path".
 204  * @buffer: Pointer to buffer to return value in.
 205  * @buflen: Sizeof @buffer.
 206  *
 207  * Returns the buffer.
 208  */
 209 static char *tomoyo_get_socket_name(struct path *path, char * const buffer,
 210                                     const int buflen)
 211 {
 212         struct inode *inode = path->dentry->d_inode;
 213         struct socket *sock = inode ? SOCKET_I(inode) : NULL;
 214         struct sock *sk = sock ? sock->sk : NULL;
 215         if (sk) {
 216                 snprintf(buffer, buflen, "socket:[family=%u:type=%u:"
 217                          "protocol=%u]", sk->sk_family, sk->sk_type,
 218                          sk->sk_protocol);
 219         } else {
 220                 snprintf(buffer, buflen, "socket:[unknown]");
 221         }
 222         return buffer;
 223 }
 224
 225 /**
 226  * tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
 227  *
 228  * @path: Pointer to "struct path".
 229  *
 230  * Returns the realpath of the given @path on success, NULL otherwise.
 231  *
 232  * If dentry is a directory, trailing '/' is appended.
 233  * Characters out of 0x20 < c < 0x7F range are converted to
 234  * \ooo style octal string.
 235  * Character \ is converted to \\ string.
 236  *
 237  * These functions use kzalloc(), so the caller must call kfree()
 238  * if these functions didn't return NULL.
 239  */
 240 char *tomoyo_realpath_from_path(struct path *path)
 241 {
 242         char *buf = NULL;
 243         char *name = NULL;
 244         unsigned int buf_len = PAGE_SIZE / 2;
 245         struct dentry *dentry = path->dentry;
 246         struct super_block *sb;
 247         if (!dentry)
 248                 return NULL;
 249         sb = dentry->d_sb;
 250         while (1) {
 251                 char *pos;
 252                 struct inode *inode;
 253                 buf_len <<= 1;
 254                 kfree(buf);
 255                 buf = kmalloc(buf_len, GFP_NOFS);
 256                 if (!buf)
 257                         break;
 258                 /* To make sure that pos is '\0' terminated. */
 259                 buf[buf_len - 1] = '\0';
 260                 /* Get better name for socket. */
 261                 if (sb->s_magic == SOCKFS_MAGIC) {
 262                         pos = tomoyo_get_socket_name(path, buf, buf_len - 1);
 263                         goto encode;
 264                 }
 265                 /* For "pipe:[\$]". */
 266                 if (dentry->d_op && dentry->d_op->d_dname) {
 267                         pos = dentry->d_op->d_dname(dentry, buf, buf_len - 1);
 268                         goto encode;
 269                 }
 270                 inode = sb->s_root->d_inode;
 271                 /*
 272                  * Get local name for filesystems without rename() operation
 273                  * or dentry without vfsmount.
 274                  */
 275                 if (!path->mnt || (inode->i_op && !inode->i_op->rename))
 276                         pos = tomoyo_get_local_path(path->dentry, buf,
 277                                                     buf_len - 1);
 278                 /* Get absolute name for the rest. */
 279                 else
 280                         pos = tomoyo_get_absolute_path(path, buf, buf_len - 1);
 281 encode:
 282                 if (IS_ERR(pos))
 283                         continue;
 284                 name = tomoyo_encode(pos);
 285                 break;
 286         }
 287         kfree(buf);
 288         if (!name)
 289                 tomoyo_warn_oom(__func__);
 290         return name;
 291 }
 292
 293 /**
 294  * tomoyo_realpath_nofollow - Get realpath of a pathname.
 295  *
 296  * @pathname: The pathname to solve.
 297  *
 298  * Returns the realpath of @pathname on success, NULL otherwise.
 299  */
 300 char *tomoyo_realpath_nofollow(const char *pathname)
 301 {
 302         struct path path;
 303
 304         if (pathname && kern_path(pathname, 0, &path) == 0) {
 305                 char *buf = tomoyo_realpath_from_path(&path);
 306                 path_put(&path);
 307                 return buf;
 308         }
 309         return NULL;
 310 }