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/*
fix-gnustack.c: check and optionally remove exec flag on Elf GNU_STACK
Copyright (C) 2011 Anthony G. Basile
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <error.h>
#include <libgen.h>
#include <gelf.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <config.h>
void
print_help(char *v)
{
printf(
"Package Name : " PACKAGE_STRING "\n"
"Bug Reports : " PACKAGE_BUGREPORT "\n"
"Program Name : %s\n"
"Description : Check for, or conditionally remove, executable flag from PT_GNU_STACK\n\n"
"Usage : %s {[-f] ELF | [-h]}\n"
"options : Print out protection flags on PT_GNU_STACK\n"
" : -f Remove X if WX flags are set on PT_GNU_STACK\n"
" : -h Print out this help\n",
basename(v),
basename(v)
);
exit(EXIT_SUCCESS);
}
char *
parse_cmd_args( int c, char *v[], int *flagv )
{
int i, oc;
if((c != 2)&&(c != 3))
error(EXIT_FAILURE, 0, "Usage: %s {-h | [-f] ELF}", v[0]);
*flagv = 0 ;
while((oc = getopt(c, v,":fh")) != -1)
switch(oc)
{
case 'f':
*flagv = 1 ;
break ;
case 'h':
print_help(v[0]);
break;
case '?':
default:
error(EXIT_FAILURE, 0, "option -%c is invalid: ignored.", optopt ) ;
}
return v[optind] ;
}
int
main( int argc, char *argv[])
{
int fd, flagv;
char *f_name;
size_t i, phnum;
Elf *elf;
GElf_Phdr phdr;
f_name = parse_cmd_args(argc, argv, &flagv);
if(elf_version(EV_CURRENT) == EV_NONE)
error(EXIT_FAILURE, 0, "Library out of date.");
if(flagv)
{
if((fd = open(f_name, O_RDWR)) < 0)
error(EXIT_FAILURE, 0, "open() fail.");
if((elf = elf_begin(fd, ELF_C_RDWR_MMAP, NULL)) == NULL)
error(EXIT_FAILURE, 0, "elf_begin() fail: %s", elf_errmsg(elf_errno()));
}
else
{
if((fd = open(f_name, O_RDONLY)) < 0)
error(EXIT_FAILURE, 0, "open() fail.");
if((elf = elf_begin(fd, ELF_C_READ, NULL)) == NULL)
error(EXIT_FAILURE, 0, "elf_begin() fail: %s", elf_errmsg(elf_errno()));
}
if(elf_kind(elf) != ELF_K_ELF)
error(EXIT_FAILURE, 0, "elf_kind() fail: this is not an elf file.");
elf_getphdrnum(elf, &phnum);
for(i=0; i<phnum; ++i)
{
if(gelf_getphdr(elf, i, &phdr) != &phdr)
error(EXIT_FAILURE, 0, "gelf_getphdr(): %s", elf_errmsg(elf_errno()));
if(phdr.p_type == PT_GNU_STACK)
{
printf("GNU_STACK: ");
if( phdr.p_flags & PF_R ) printf("R");
if( phdr.p_flags & PF_W ) printf("W");
if( phdr.p_flags & PF_X ) printf("X");
printf("\n");
if(flagv && (phdr.p_flags & PF_W) && (phdr.p_flags & PF_X))
{
printf("W&X FOUND: X flag removed\n");
phdr.p_flags ^= PF_X;
if(!gelf_update_phdr(elf, i, &phdr))
error(EXIT_FAILURE, 0, "gelf_update_phdr(): %s", elf_errmsg(elf_errno()));
}
}
}
elf_end(elf);
close(fd);
}
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