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 <net/sock.h>
  16 #include "common.h"
  17 #include "../../fs/internal.h"
  18
  19 /**
  20  * tomoyo_encode: Convert binary string to ascii string.
  21  *
  22  * @str: String in binary format.
  23  *
  24  * Returns pointer to @str in ascii format on success, NULL otherwise.
  25  *
  26  * This function uses kzalloc(), so caller must kfree() if this function
  27  * didn't return NULL.
  28  */
  29 char *tomoyo_encode(const char *str)
  30 {
  31         int len = 0;
  32         const char *p = str;
  33         char *cp;
  34         char *cp0;
  35
  36         if (!p)
  37                 return NULL;
  38         while (*p) {
  39                 const unsigned char c = *p++;
  40                 if (c == '\\')
  41                         len += 2;
  42                 else if (c > ' ' && c < 127)
  43                         len++;
  44                 else
  45                         len += 4;
  46         }
  47         len++;
  48         /* Reserve space for appending "/". */
  49         cp = kzalloc(len + 10, GFP_NOFS);
  50         if (!cp)
  51                 return NULL;
  52         cp0 = cp;
  53         p = str;
  54         while (*p) {
  55                 const unsigned char c = *p++;
  56
  57                 if (c == '\\') {
  58                         *cp++ = '\\';
  59                         *cp++ = '\\';
  60                 } else if (c > ' ' && c < 127) {
  61                         *cp++ = c;
  62                 } else {
  63                         *cp++ = '\\';
  64                         *cp++ = (c >> 6) + '0';
  65                         *cp++ = ((c >> 3) & 7) + '0';
  66                         *cp++ = (c & 7) + '0';
  67                 }
  68         }
  69         return cp0;
  70 }
  71
  72 /**
  73  * tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
  74  *
  75  * @path: Pointer to "struct path".
  76  *
  77  * Returns the realpath of the given @path on success, NULL otherwise.
  78  *
  79  * If dentry is a directory, trailing '/' is appended.
  80  * Characters out of 0x20 < c < 0x7F range are converted to
  81  * \ooo style octal string.
  82  * Character \ is converted to \\ string.
  83  *
  84  * These functions use kzalloc(), so the caller must call kfree()
  85  * if these functions didn't return NULL.
  86  */
  87 char *tomoyo_realpath_from_path(struct path *path)
  88 {
  89         char *buf = NULL;
  90         char *name = NULL;
  91         unsigned int buf_len = PAGE_SIZE / 2;
  92         struct dentry *dentry = path->dentry;
  93         bool is_dir;
  94         if (!dentry)
  95                 return NULL;
  96         is_dir = dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode);
  97         while (1) {
  98                 struct path ns_root = { .mnt = NULL, .dentry = NULL };
  99                 char *pos;
 100                 buf_len <<= 1;
 101                 kfree(buf);
 102                 buf = kmalloc(buf_len, GFP_NOFS);
 103                 if (!buf)
 104                         break;
 105                 /* Get better name for socket. */
 106                 if (dentry->d_sb && dentry->d_sb->s_magic == SOCKFS_MAGIC) {
 107                         struct inode *inode = dentry->d_inode;
 108                         struct socket *sock = inode ? SOCKET_I(inode) : NULL;
 109                         struct sock *sk = sock ? sock->sk : NULL;
 110                         if (sk) {
 111                                 snprintf(buf, buf_len - 1, "socket:[family=%u:"
 112                                          "type=%u:protocol=%u]", sk->sk_family,
 113                                          sk->sk_type, sk->sk_protocol);
 114                         } else {
 115                                 snprintf(buf, buf_len - 1, "socket:[unknown]");
 116                         }
 117                         name = tomoyo_encode(buf);
 118                         break;
 119                 }
 120                 /* For "socket:[\$]" and "pipe:[\$]". */
 121                 if (dentry->d_op && dentry->d_op->d_dname) {
 122                         pos = dentry->d_op->d_dname(dentry, buf, buf_len - 1);
 123                         if (IS_ERR(pos))
 124                                 continue;
 125                         name = tomoyo_encode(pos);
 126                         break;
 127                 }
 128                 /* If we don't have a vfsmount, we can't calculate. */
 129                 if (!path->mnt)
 130                         break;
 131                 /* go to whatever namespace root we are under */
 132                 pos = __d_path(path, &ns_root, buf, buf_len);
 133                 /* Prepend "/proc" prefix if using internal proc vfs mount. */
 134                 if (!IS_ERR(pos) && (path->mnt->mnt_flags & MNT_INTERNAL) &&
 135                     (path->mnt->mnt_sb->s_magic == PROC_SUPER_MAGIC)) {
 136                         pos -= 5;
 137                         if (pos >= buf)
 138                                 memcpy(pos, "/proc", 5);
 139                         else
 140                                 pos = ERR_PTR(-ENOMEM);
 141                 }
 142                 if (IS_ERR(pos))
 143                         continue;
 144                 name = tomoyo_encode(pos);
 145                 break;
 146         }
 147         kfree(buf);
 148         if (!name)
 149                 tomoyo_warn_oom(__func__);
 150         else if (is_dir && *name) {
 151                 /* Append trailing '/' if dentry is a directory. */
 152                 char *pos = name + strlen(name) - 1;
 153                 if (*pos != '/')
 154                         /*
 155                          * This is OK because tomoyo_encode() reserves space
 156                          * for appending "/".
 157                          */
 158                         *++pos = '/';
 159         }
 160         return name;
 161 }
 162
 163 /**
 164  * tomoyo_realpath_nofollow - Get realpath of a pathname.
 165  *
 166  * @pathname: The pathname to solve.
 167  *
 168  * Returns the realpath of @pathname on success, NULL otherwise.
 169  */
 170 char *tomoyo_realpath_nofollow(const char *pathname)
 171 {
 172         struct path path;
 173
 174         if (pathname && kern_path(pathname, 0, &path) == 0) {
 175                 char *buf = tomoyo_realpath_from_path(&path);
 176                 path_put(&path);
 177                 return buf;
 178         }
 179         return NULL;
 180 }