security/tomoyo/realpath.c

   1 /*
   2  * security/tomoyo/realpath.c
   3  *
   4  * Pathname calculation functions for TOMOYO.
   5  *
   6  * Copyright (C) 2005-2010  NTT DATA CORPORATION
   7  */
   8
   9 #include <linux/types.h>
  10 #include <linux/mount.h>
  11 #include <linux/mnt_namespace.h>
  12 #include <linux/fs_struct.h>
  13 #include <linux/magic.h>
  14 #include <linux/slab.h>
  15 #include "common.h"
  16
  17 /**
  18  * tomoyo_encode: Convert binary string to ascii string.
  19  *
  20  * @buffer:  Buffer for ASCII string.
  21  * @buflen:  Size of @buffer.
  22  * @str:     Binary string.
  23  *
  24  * Returns 0 on success, -ENOMEM otherwise.
  25  */
  26 int tomoyo_encode(char *buffer, int buflen, const char *str)
  27 {
  28         while (1) {
  29                 const unsigned char c = *(unsigned char *) str++;
  30
  31                 if (tomoyo_is_valid(c)) {
  32                         if (--buflen <= 0)
  33                                 break;
  34                         *buffer++ = (char) c;
  35                         if (c != '\\')
  36                                 continue;
  37                         if (--buflen <= 0)
  38                                 break;
  39                         *buffer++ = (char) c;
  40                         continue;
  41                 }
  42                 if (!c) {
  43                         if (--buflen <= 0)
  44                                 break;
  45                         *buffer = '\0';
  46                         return 0;
  47                 }
  48                 buflen -= 4;
  49                 if (buflen <= 0)
  50                         break;
  51                 *buffer++ = '\\';
  52                 *buffer++ = (c >> 6) + '0';
  53                 *buffer++ = ((c >> 3) & 7) + '0';
  54                 *buffer++ = (c & 7) + '0';
  55         }
  56         return -ENOMEM;
  57 }
  58
  59 /**
  60  * tomoyo_realpath_from_path2 - Returns realpath(3) of the given dentry but ignores chroot'ed root.
  61  *
  62  * @path:        Pointer to "struct path".
  63  * @newname:     Pointer to buffer to return value in.
  64  * @newname_len: Size of @newname.
  65  *
  66  * Returns 0 on success, negative value otherwise.
  67  *
  68  * If dentry is a directory, trailing '/' is appended.
  69  * Characters out of 0x20 < c < 0x7F range are converted to
  70  * \ooo style octal string.
  71  * Character \ is converted to \\ string.
  72  */
  73 int tomoyo_realpath_from_path2(struct path *path, char *newname,
  74                                int newname_len)
  75 {
  76         int error = -ENOMEM;
  77         struct dentry *dentry = path->dentry;
  78         char *sp;
  79
  80         if (!dentry || !path->mnt || !newname || newname_len <= 2048)
  81                 return -EINVAL;
  82         if (dentry->d_op && dentry->d_op->d_dname) {
  83                 /* For "socket:[\$]" and "pipe:[\$]". */
  84                 static const int offset = 1536;
  85                 sp = dentry->d_op->d_dname(dentry, newname + offset,
  86                                            newname_len - offset);
  87         } else {
  88                 struct path ns_root = {.mnt = NULL, .dentry = NULL};
  89
  90                 spin_lock(&dcache_lock);
  91                 /* go to whatever namespace root we are under */
  92                 sp = __d_path(path, &ns_root, newname, newname_len);
  93                 spin_unlock(&dcache_lock);
  94                 /* Prepend "/proc" prefix if using internal proc vfs mount. */
  95                 if (!IS_ERR(sp) && (path->mnt->mnt_flags & MNT_INTERNAL) &&
  96                     (path->mnt->mnt_sb->s_magic == PROC_SUPER_MAGIC)) {
  97                         sp -= 5;
  98                         if (sp >= newname)
  99                                 memcpy(sp, "/proc", 5);
 100                         else
 101                                 sp = ERR_PTR(-ENOMEM);
 102                 }
 103         }
 104         if (IS_ERR(sp))
 105                 error = PTR_ERR(sp);
 106         else
 107                 error = tomoyo_encode(newname, sp - newname, sp);
 108         /* Append trailing '/' if dentry is a directory. */
 109         if (!error && dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)
 110             && *newname) {
 111                 sp = newname + strlen(newname);
 112                 if (*(sp - 1) != '/') {
 113                         if (sp < newname + newname_len - 4) {
 114                                 *sp++ = '/';
 115                                 *sp = '\0';
 116                         } else {
 117                                 error = -ENOMEM;
 118                         }
 119                 }
 120         }
 121         if (error)
 122                 tomoyo_warn_oom(__func__);
 123         return error;
 124 }
 125
 126 /**
 127  * tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
 128  *
 129  * @path: Pointer to "struct path".
 130  *
 131  * Returns the realpath of the given @path on success, NULL otherwise.
 132  *
 133  * These functions use kzalloc(), so the caller must call kfree()
 134  * if these functions didn't return NULL.
 135  */
 136 char *tomoyo_realpath_from_path(struct path *path)
 137 {
 138         char *buf = kzalloc(sizeof(struct tomoyo_page_buffer), GFP_NOFS);
 139
 140         BUILD_BUG_ON(TOMOYO_MAX_PATHNAME_LEN > PATH_MAX);
 141         BUILD_BUG_ON(sizeof(struct tomoyo_page_buffer)
 142                      <= TOMOYO_MAX_PATHNAME_LEN - 1);
 143         if (!buf)
 144                 return NULL;
 145         if (tomoyo_realpath_from_path2(path, buf,
 146                                        TOMOYO_MAX_PATHNAME_LEN - 1) == 0)
 147                 return buf;
 148         kfree(buf);
 149         return NULL;
 150 }
 151
 152 /**
 153  * tomoyo_realpath - Get realpath of a pathname.
 154  *
 155  * @pathname: The pathname to solve.
 156  *
 157  * Returns the realpath of @pathname on success, NULL otherwise.
 158  */
 159 char *tomoyo_realpath(const char *pathname)
 160 {
 161         struct path path;
 162
 163         if (pathname && kern_path(pathname, LOOKUP_FOLLOW, &path) == 0) {
 164                 char *buf = tomoyo_realpath_from_path(&path);
 165                 path_put(&path);
 166                 return buf;
 167         }
 168         return NULL;
 169 }
 170
 171 /**
 172  * tomoyo_realpath_nofollow - Get realpath of a pathname.
 173  *
 174  * @pathname: The pathname to solve.
 175  *
 176  * Returns the realpath of @pathname on success, NULL otherwise.
 177  */
 178 char *tomoyo_realpath_nofollow(const char *pathname)
 179 {
 180         struct path path;
 181
 182         if (pathname && kern_path(pathname, 0, &path) == 0) {
 183                 char *buf = tomoyo_realpath_from_path(&path);
 184                 path_put(&path);
 185                 return buf;
 186         }
 187         return NULL;
 188 }