elf/check-execstack.c

   1 /* Check for executable stacks in DSOs.
   2    Copyright (C) 2009 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contribute by Ulrich Drepper <drepper@redhat.com>. 2009.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <byteswap.h>
  22 #include <elf.h>
  23 #include <endian.h>
  24 #include <fcntl.h>
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28 #include <unistd.h>
  29
  30
  31 #ifdef BITS
  32
  33 # define AB(name) _AB (name, BITS)
  34 # define _AB(name, bits) __AB (name, bits)
  35 # define __AB(name, bits) name##bits
  36 # define E(name) _E (name, BITS)
  37 # define _E(name, bits) __E (name, bits)
  38 # define __E(name, bits) Elf##bits##_##name
  39 # define SWAP(val) \
  40   ({ __typeof (val) __res;                                                    \
  41      if (((ehdr.e_ident[EI_DATA] == ELFDATA2MSB                               \
  42            && BYTE_ORDER == LITTLE_ENDIAN)                                    \
  43           || (ehdr.e_ident[EI_DATA] == ELFDATA2LSB                            \
  44               && BYTE_ORDER == BIG_ENDIAN))                                   \
  45          && sizeof (val) != 1)                                                \
  46        {                                                                      \
  47          if (sizeof (val) == 2)                                               \
  48            __res = bswap_16 (val);                                            \
  49          else if (sizeof (val) == 4)                                          \
  50            __res = bswap_32 (val);                                            \
  51          else                                                                 \
  52            __res = bswap_64 (val);                                            \
  53        }                                                                      \
  54      else                                                                     \
  55        __res = (val);                                                         \
  56      __res; })
  57
  58
  59 static int
  60 AB(handle_file) (const char *fname, int fd)
  61 {
  62   E(Ehdr) ehdr;
  63
  64   if (pread (fd, &ehdr, sizeof (ehdr), 0) != sizeof (ehdr))
  65     {
  66     read_error:
  67       printf ("%s: read error: %m\n", fname);
  68       return 1;
  69     }
  70
  71   const size_t phnum = SWAP (ehdr.e_phnum);
  72   const size_t phentsize = SWAP (ehdr.e_phentsize);
  73
  74   /* Read the program header.  */
  75   E(Phdr) *phdr = alloca (phentsize * phnum);
  76   if (pread (fd, phdr, phentsize * phnum, SWAP (ehdr.e_phoff))
  77       != phentsize * phnum)
  78     goto read_error;
  79
  80   /* Search for the PT_GNU_STACK entry.  */
  81   for (size_t cnt = 0; cnt < phnum; ++cnt)
  82     if (SWAP (phdr[cnt].p_type) == PT_GNU_STACK)
  83       {
  84         unsigned int flags = SWAP(phdr[cnt].p_flags);
  85         if (flags & PF_X)
  86           {
  87             printf ("%s: executable stack signaled\n", fname);
  88             return 1;
  89           }
  90
  91         return 0;
  92       }
  93
  94   printf ("%s: no PT_GNU_STACK entry\n", fname);
  95   return 1;
  96 }
  97
  98 # undef BITS
  99 #else
 100
 101 # define BITS 32
 102 # include "check-execstack.c"
 103
 104 # define BITS 64
 105 # include "check-execstack.c"
 106
 107
 108 static int
 109 handle_file (const char *fname)
 110 {
 111   int fd = open (fname, O_RDONLY);
 112   if (fd == -1)
 113     {
 114       printf ("cannot open %s: %m\n", fname);
 115       return 1;
 116     }
 117
 118   /* Read was is supposed to be the ELF header.  Read the initial
 119      bytes to determine whether this is a 32 or 64 bit file.  */
 120   char ident[EI_NIDENT];
 121   if (read (fd, ident, EI_NIDENT) != EI_NIDENT)
 122     {
 123       printf ("%s: read error: %m\n", fname);
 124       close (fd);
 125       return 1;
 126     }
 127
 128   if (memcmp (&ident[EI_MAG0], ELFMAG, SELFMAG) != 0)
 129     {
 130       printf ("%s: not an ELF file\n", fname);
 131       close (fd);
 132       return 1;
 133     }
 134
 135   int result;
 136   if (ident[EI_CLASS] == ELFCLASS64)
 137     result = handle_file64 (fname, fd);
 138   else
 139     result = handle_file32 (fname, fd);
 140
 141   close (fd);
 142
 143   return result;
 144 }
 145
 146
 147 int
 148 main (int argc, char *argv[])
 149 {
 150   int cnt;
 151   int result = 0;
 152
 153   for (cnt = 1; cnt < argc; ++cnt)
 154     result |= handle_file (argv[cnt]);
 155
 156   return result;
 157 }
 158 #endif