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