This is the mail archive of the
glibc-bugs@sourceware.org
mailing list for the glibc project.
[Bug libc/14552] New: Two security issues in strcoll() function
- From: "shaun.colley at ioactive dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: Thu, 06 Sep 2012 16:18:35 +0000
- Subject: [Bug libc/14552] New: Two security issues in strcoll() function
- Auto-submitted: auto-generated
http://sourceware.org/bugzilla/show_bug.cgi?id=14552
Bug #: 14552
Summary: Two security issues in strcoll() function
Product: glibc
Version: 2.17
Status: NEW
Severity: normal
Priority: P2
Component: libc
AssignedTo: unassigned@sourceware.org
ReportedBy: shaun.colley@ioactive.com
CC: drepper.fsp@gmail.com
Classification: Unclassified
There are two problems with the strcoll() interface.
1) alloca() stack overflow
If the malloc() call fails (i.e. OOM conditions), strcoll() will failsafe back
to alloca(), which could result in unbounded alloca() calls and exploitable
conditions if the stack pointer is shifted over the guard area and into the
heap. See vulnerable code below.
if (idx1arr == NULL) // [5] memory allocation failed, use alloca()
...
/* No memory. Well, go with the stack then.
XXX Once this implementation is stable we will handle this
differently. Instead of precomputing the indeces we will
do this in time. This means, though, that this happens for
every pass again. */
goto try_stack;
use_malloc = 1;
}
else
{
try_stack:
idx1arr = (int32_t *) alloca (s1len * sizeof (int32_t)); // [6]
stack pointer shifting
idx2arr = (int32_t *) alloca (s2len * sizeof (int32_t));
rule1arr = (unsigned char *) alloca (s1len);
rule2arr = (unsigned char *) alloca (s2len);
Here's my testcase.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <locale.h>
#define LEN 500000
int main() {
char *ptr1 = malloc(LEN + 1);
char *ptr2 = malloc(LEN + 1);
char *wasted = NULL;
int i = 0, ret = 0;
if(!ptr1 || !ptr2) {
printf("memory allocation failed\n");
return -1;
}
memset(ptr1, 0x61, LEN);
memset(ptr2, 0x61, LEN);
ptr1[LEN] = 0;
ptr2[LEN] = 0;
printf("strings allocated\n");
char *ptr = setlocale(LC_ALL, "en_US.UTF-8");
if(!ptr) {
printf("error setting locale\n");
return -1;
}
/* malloc() big chunks until we're out of memory */
do {
wasted = malloc(1000000);
printf("%p\n", wasted);
i++;
} while(wasted);
ret = strcoll(ptr1, ptr2);
if(!ret) {
printf("strings were lexicographically identical\n");
}
else {
printf("strings were different\n");
}
return 0;
}
2) Integer overflows in the malloc() memory allocation.
int
STRCOLL (s1, s2, l)
const STRING_TYPE *s1;
const STRING_TYPE *s2;
__locale_t l;
{
[ â ]
/* We need this a few times. */
s1len = STRLEN (s1);
s2len = STRLEN (s2);
[ â ]
Please note that the localedef programs makes sure that `position'
is not used at the first level. */
if (! __libc_use_alloca ((s1len + s2len) * (sizeof (int32_t) + 1))) // [1]
if arithmetic is greater 65536, use malloc() instead of alloca()
{
idx1arr = (int32_t *) malloc ((s1len + s2len) * (sizeof (int32_t) + 1));
// [2] attempt to get memory using malloc()
If s1 and s2 point to long strongs, the arithmetic in the malloc() argument may
give an integer overflow, and result in subsequent heap corruption.
Cheers,
Shaun
--
Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.