security/tomoyo/realpath.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * security/tomoyo/realpath.c
   4  *
   5  * Copyright (C) 2005-2011  NTT DATA CORPORATION
   6  */
   7
   8 #include "common.h"
   9 #include <linux/magic.h>
  10
  11 /**
  12  * tomoyo_encode2 - Encode binary string to ascii string.
  13  *
  14  * @str:     String in binary format.
  15  * @str_len: Size of @str in byte.
  16  *
  17  * Returns pointer to @str in ascii format on success, NULL otherwise.
  18  *
  19  * This function uses kzalloc(), so caller must kfree() if this function
  20  * didn't return NULL.
  21  */
  22 char *tomoyo_encode2(const char *str, int str_len)
  23 {
  24         int i;
  25         int len = 0;
  26         const char *p = str;
  27         char *cp;
  28         char *cp0;
  29
  30         if (!p)
  31                 return NULL;
  32         for (i = 0; i < str_len; i++) {
  33                 const unsigned char c = p[i];
  34
  35                 if (c == '\\')
  36                         len += 2;
  37                 else if (c > ' ' && c < 127)
  38                         len++;
  39                 else
  40                         len += 4;
  41         }
  42         len++;
  43         /* Reserve space for appending "/". */
  44         cp = kzalloc(len + 10, GFP_NOFS);
  45         if (!cp)
  46                 return NULL;
  47         cp0 = cp;
  48         p = str;
  49         for (i = 0; i < str_len; i++) {
  50                 const unsigned char c = p[i];
  51
  52                 if (c == '\\') {
  53                         *cp++ = '\\';
  54                         *cp++ = '\\';
  55                 } else if (c > ' ' && c < 127) {
  56                         *cp++ = c;
  57                 } else {
  58                         *cp++ = '\\';
  59                         *cp++ = (c >> 6) + '0';
  60                         *cp++ = ((c >> 3) & 7) + '0';
  61                         *cp++ = (c & 7) + '0';
  62                 }
  63         }
  64         return cp0;
  65 }
  66
  67 /**
  68  * tomoyo_encode - Encode binary string to ascii string.
  69  *
  70  * @str: String in binary format.
  71  *
  72  * Returns pointer to @str in ascii format on success, NULL otherwise.
  73  *
  74  * This function uses kzalloc(), so caller must kfree() if this function
  75  * didn't return NULL.
  76  */
  77 char *tomoyo_encode(const char *str)
  78 {
  79         return str ? tomoyo_encode2(str, strlen(str)) : NULL;
  80 }
  81
  82 /**
  83  * tomoyo_get_absolute_path - Get the path of a dentry but ignores chroot'ed root.
  84  *
  85  * @path:   Pointer to "struct path".
  86  * @buffer: Pointer to buffer to return value in.
  87  * @buflen: Sizeof @buffer.
  88  *
  89  * Returns the buffer on success, an error code otherwise.
  90  *
  91  * If dentry is a directory, trailing '/' is appended.
  92  */
  93 static char *tomoyo_get_absolute_path(const struct path *path, char * const buffer,
  94                                       const int buflen)
  95 {
  96         char *pos = ERR_PTR(-ENOMEM);
  97         if (buflen >= 256) {
  98                 /* go to whatever namespace root we are under */
  99                 pos = d_absolute_path(path, buffer, buflen - 1);
 100                 if (!IS_ERR(pos) && *pos == '/' && pos[1]) {
 101                         struct inode *inode = d_backing_inode(path->dentry);
 102                         if (inode && S_ISDIR(inode->i_mode)) {
 103                                 buffer[buflen - 2] = '/';
 104                                 buffer[buflen - 1] = '\0';
 105                         }
 106                 }
 107         }
 108         return pos;
 109 }
 110
 111 /**
 112  * tomoyo_get_dentry_path - Get the path of a dentry.
 113  *
 114  * @dentry: Pointer to "struct dentry".
 115  * @buffer: Pointer to buffer to return value in.
 116  * @buflen: Sizeof @buffer.
 117  *
 118  * Returns the buffer on success, an error code otherwise.
 119  *
 120  * If dentry is a directory, trailing '/' is appended.
 121  */
 122 static char *tomoyo_get_dentry_path(struct dentry *dentry, char * const buffer,
 123                                     const int buflen)
 124 {
 125         char *pos = ERR_PTR(-ENOMEM);
 126         if (buflen >= 256) {
 127                 pos = dentry_path_raw(dentry, buffer, buflen - 1);
 128                 if (!IS_ERR(pos) && *pos == '/' && pos[1]) {
 129                         struct inode *inode = d_backing_inode(dentry);
 130                         if (inode && S_ISDIR(inode->i_mode)) {
 131                                 buffer[buflen - 2] = '/';
 132                                 buffer[buflen - 1] = '\0';
 133                         }
 134                 }
 135         }
 136         return pos;
 137 }
 138
 139 /**
 140  * tomoyo_get_local_path - Get the path of a dentry.
 141  *
 142  * @dentry: Pointer to "struct dentry".
 143  * @buffer: Pointer to buffer to return value in.
 144  * @buflen: Sizeof @buffer.
 145  *
 146  * Returns the buffer on success, an error code otherwise.
 147  */
 148 static char *tomoyo_get_local_path(struct dentry *dentry, char * const buffer,
 149                                    const int buflen)
 150 {
 151         struct super_block *sb = dentry->d_sb;
 152         char *pos = tomoyo_get_dentry_path(dentry, buffer, buflen);
 153         if (IS_ERR(pos))
 154                 return pos;
 155         /* Convert from $PID to self if $PID is current thread. */
 156         if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') {
 157                 char *ep;
 158                 const pid_t pid = (pid_t) simple_strtoul(pos + 1, &ep, 10);
 159                 if (*ep == '/' && pid && pid ==
 160                     task_tgid_nr_ns(current, sb->s_fs_info)) {
 161                         pos = ep - 5;
 162                         if (pos < buffer)
 163                                 goto out;
 164                         memmove(pos, "/self", 5);
 165                 }
 166                 goto prepend_filesystem_name;
 167         }
 168         /* Use filesystem name for unnamed devices. */
 169         if (!MAJOR(sb->s_dev))
 170                 goto prepend_filesystem_name;
 171         {
 172                 struct inode *inode = d_backing_inode(sb->s_root);
 173                 /*
 174                  * Use filesystem name if filesystem does not support rename()
 175                  * operation.
 176                  */
 177                 if (!inode->i_op->rename)
 178                         goto prepend_filesystem_name;
 179         }
 180         /* Prepend device name. */
 181         {
 182                 char name[64];
 183                 int name_len;
 184                 const dev_t dev = sb->s_dev;
 185                 name[sizeof(name) - 1] = '\0';
 186                 snprintf(name, sizeof(name) - 1, "dev(%u,%u):", MAJOR(dev),
 187                          MINOR(dev));
 188                 name_len = strlen(name);
 189                 pos -= name_len;
 190                 if (pos < buffer)
 191                         goto out;
 192                 memmove(pos, name, name_len);
 193                 return pos;
 194         }
 195         /* Prepend filesystem name. */
 196 prepend_filesystem_name:
 197         {
 198                 const char *name = sb->s_type->name;
 199                 const int name_len = strlen(name);
 200                 pos -= name_len + 1;
 201                 if (pos < buffer)
 202                         goto out;
 203                 memmove(pos, name, name_len);
 204                 pos[name_len] = ':';
 205         }
 206         return pos;
 207 out:
 208         return ERR_PTR(-ENOMEM);
 209 }
 210
 211 /**
 212  * tomoyo_get_socket_name - Get the name of a socket.
 213  *
 214  * @path:   Pointer to "struct path".
 215  * @buffer: Pointer to buffer to return value in.
 216  * @buflen: Sizeof @buffer.
 217  *
 218  * Returns the buffer.
 219  */
 220 static char *tomoyo_get_socket_name(const struct path *path, char * const buffer,
 221                                     const int buflen)
 222 {
 223         struct inode *inode = d_backing_inode(path->dentry);
 224         struct socket *sock = inode ? SOCKET_I(inode) : NULL;
 225         struct sock *sk = sock ? sock->sk : NULL;
 226         if (sk) {
 227                 snprintf(buffer, buflen, "socket:[family=%u:type=%u:"
 228                          "protocol=%u]", sk->sk_family, sk->sk_type,
 229                          sk->sk_protocol);
 230         } else {
 231                 snprintf(buffer, buflen, "socket:[unknown]");
 232         }
 233         return buffer;
 234 }
 235
 236 /**
 237  * tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
 238  *
 239  * @path: Pointer to "struct path".
 240  *
 241  * Returns the realpath of the given @path on success, NULL otherwise.
 242  *
 243  * If dentry is a directory, trailing '/' is appended.
 244  * Characters out of 0x20 < c < 0x7F range are converted to
 245  * \ooo style octal string.
 246  * Character \ is converted to \\ string.
 247  *
 248  * These functions use kzalloc(), so the caller must call kfree()
 249  * if these functions didn't return NULL.
 250  */
 251 char *tomoyo_realpath_from_path(const struct path *path)
 252 {
 253         char *buf = NULL;
 254         char *name = NULL;
 255         unsigned int buf_len = PAGE_SIZE / 2;
 256         struct dentry *dentry = path->dentry;
 257         struct super_block *sb;
 258         if (!dentry)
 259                 return NULL;
 260         sb = dentry->d_sb;
 261         while (1) {
 262                 char *pos;
 263                 struct inode *inode;
 264                 buf_len <<= 1;
 265                 kfree(buf);
 266                 buf = kmalloc(buf_len, GFP_NOFS);
 267                 if (!buf)
 268                         break;
 269                 /* To make sure that pos is '\0' terminated. */
 270                 buf[buf_len - 1] = '\0';
 271                 /* Get better name for socket. */
 272                 if (sb->s_magic == SOCKFS_MAGIC) {
 273                         pos = tomoyo_get_socket_name(path, buf, buf_len - 1);
 274                         goto encode;
 275                 }
 276                 /* For "pipe:[\$]". */
 277                 if (dentry->d_op && dentry->d_op->d_dname) {
 278                         pos = dentry->d_op->d_dname(dentry, buf, buf_len - 1);
 279                         goto encode;
 280                 }
 281                 inode = d_backing_inode(sb->s_root);
 282                 /*
 283                  * Get local name for filesystems without rename() operation
 284                  * or dentry without vfsmount.
 285                  */
 286                 if (!path->mnt ||
 287                     (!inode->i_op->rename))
 288                         pos = tomoyo_get_local_path(path->dentry, buf,
 289                                                     buf_len - 1);
 290                 /* Get absolute name for the rest. */
 291                 else {
 292                         pos = tomoyo_get_absolute_path(path, buf, buf_len - 1);
 293                         /*
 294                          * Fall back to local name if absolute name is not
 295                          * available.
 296                          */
 297                         if (pos == ERR_PTR(-EINVAL))
 298                                 pos = tomoyo_get_local_path(path->dentry, buf,
 299                                                             buf_len - 1);
 300                 }
 301 encode:
 302                 if (IS_ERR(pos))
 303                         continue;
 304                 name = tomoyo_encode(pos);
 305                 break;
 306         }
 307         kfree(buf);
 308         if (!name)
 309                 tomoyo_warn_oom(__func__);
 310         return name;
 311 }
 312
 313 /**
 314  * tomoyo_realpath_nofollow - Get realpath of a pathname.
 315  *
 316  * @pathname: The pathname to solve.
 317  *
 318  * Returns the realpath of @pathname on success, NULL otherwise.
 319  */
 320 char *tomoyo_realpath_nofollow(const char *pathname)
 321 {
 322         struct path path;
 323
 324         if (pathname && kern_path(pathname, 0, &path) == 0) {
 325                 char *buf = tomoyo_realpath_from_path(&path);
 326                 path_put(&path);
 327                 return buf;
 328         }
 329         return NULL;
 330 }