--GDLQamdgIxhPcIwq Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable ----- Forwarded message from FreeBSD Security Officer <security-officer@Fre= eBSD.ORG> ----- Delivered-To: freebsd-announceat_private Date: Wed, 15 Sep 1999 23:25:03 -0600 (MDT) From: FreeBSD Security Officer <security-officerat_private> Subject: FreeBSD Security Advisory: FreeBSD-SA-99:04.core Reply-To: security-officerat_private X-Loop: FreeBSD.org Precedence: bulk To: undisclosed-recipients: ; -----BEGIN PGP SIGNED MESSAGE----- =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D FreeBSD-SA-99:04 Security Adviso= ry FreeBSD, In= c. Topic: Coredumps and symbolic links Category: core Module: kernel Announced: 1999-09-15 Affects: FreeBSD 3.2 (and earlier) FreeBSD-current before the correction date. FreeBSD 3.2-stable before the correction date. FreeBSD 2.2.8-stable before the correction date. Corrected: FreeBSD-3.3 RELEASE FreeBSD-current as of 1999/08/26 FreeBSD-3.2-stable as of 1999/08/26 FreeBSD-2.2.8-stable as of 1999/08/29 The FreeBSD-3.3-RC series of releases are not affected. FreeBSD only: NO Patches: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-99:04/ I. Background As a diagnostic aid to help programmers find bugs in their programs, the system creates core files when an illegal instruction or other fatal error happens. A flaw in the kernel allowed it to follow symbolic links when creating core files. II. Problem Description The fts library functions had a flaw in them where which would lead to a core dump when periodic ran the security checking scripts (or other scripts which traverse trees that can be controlled by users). periodic(3) should limit core size to zero to disable core dumps while it is executing commands, but does not do so. In addition, the kernel should not follow symbolic links. All three of these problems caused a situation where it was possible for an attacker could create or overwrite an arbitrary file on the system with a moderate degree of controll of its contents to cause a problem. III. Impact Local users could gain root access. IV. Workaround One can workaround this problem by preventing core dumps for periodic. This solution is less than completely satisfying, since it only plugs the known exploit hole. None the less, this may provide a short term stopgap solution until a new kernel and/or userland can be installed. # mv /usr/sbin/periodic /usr/sbin/periodic.bin # cat > /usr/sbin/periodic #!/bin/sh ulimit -c 0 /usr/sbin/periodic.bin $* ^D # chmod 555 /usr/sbin/periodic Another alternative would be to update the fts routines to a version newer than 1999/09/02 (for -current or 3.3-stable) or 1999/09/04 (for 2.2.8-stable). However, this requires that you rebuild via "make world" to take effect. V. Solution Please note: there is a separate advisory describing the fts problem and solution. Please see FreeBSD-SA-99:05.fts.asc in the advisories directory for additional information about the fts patch. Apply the following patches to your kernel. They will disallow following symbolic links when creating core files. This will stop this attack, and all similar such attacks. Here's the patch for freebsd-current: *** kern/imgact_elf.c 1999/07/09 19:10:14 1.61 --- kern/imgact_elf.c 1999/08/26 17:32:48 1.62 *************** *** 722,729 **** if (name =3D=3D NULL) return (EFAULT); /* XXX -- not the best error */ ! NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, name, p); ! error =3D vn_open(&nd, O_CREAT | FWRITE, S_IRUSR | S_IWUSR); free(name, M_TEMP); if (error) return (error); --- 722,729 ---- if (name =3D=3D NULL) return (EFAULT); /* XXX -- not the best error */ ! NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name, p); ! error =3D vn_open(&nd, O_CREAT | FWRITE | O_NOFOLLOW, S_IRUSR | S_IW= USR); free(name, M_TEMP); if (error) return (error); *** kern/imgact_aout.c 1999/05/17 00:53:36 1.52 --- kern/imgact_aout.c 1999/08/26 17:32:48 1.53 *************** *** 264,271 **** name =3D expand_name(p->p_comm, p->p_ucred->cr_uid, p->p_pid); if (name =3D=3D NULL) return (EFAULT); /* XXX -- not the best error */ ! NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, name, p); ! error =3D vn_open(&nd, O_CREAT | FWRITE, S_IRUSR | S_IWUSR); free(name, M_TEMP); if (error) return (error); --- 264,271 ---- name =3D expand_name(p->p_comm, p->p_ucred->cr_uid, p->p_pid); if (name =3D=3D NULL) return (EFAULT); /* XXX -- not the best error */ ! NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name, p); ! error =3D vn_open(&nd, O_CREAT | FWRITE | O_NOFOLLOW, S_IRUSR | S_IW= USR); free(name, M_TEMP); if (error) return (error); Here's the patch for freebsd-3.2-stable: *** kern/imgact_elf.c 1999/07/15 13:01:54 1.44.2.4 --- kern/imgact_elf.c 1999/08/26 17:35:03 1.44.2.5 *************** *** 699,706 **** if (name =3D=3D NULL) return (EFAULT); /* XXX -- not the best error */ ! NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, name, p); ! error =3D vn_open(&nd, O_CREAT | FWRITE, S_IRUSR | S_IWUSR); free(name, M_TEMP); if (error) return (error); --- 699,706 ---- if (name =3D=3D NULL) return (EFAULT); /* XXX -- not the best error */ ! NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name, p); ! error =3D vn_open(&nd, O_CREAT | FWRITE | O_NOFOLLOW, S_IRUSR | S_IW= USR); free(name, M_TEMP); if (error) return (error); *** kern/imgact_aout.c 1999/04/14 04:55:22 1.44.2.1 --- kern/imgact_aout.c 1999/08/26 17:35:02 1.44.2.2 *************** *** 259,266 **** name =3D expand_name(p->p_comm, p->p_ucred->cr_uid, p->p_pid); if (name =3D=3D NULL) return (EFAULT); /* XXX -- not the best error */ ! NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, name, p); ! error =3D vn_open(&nd, O_CREAT | FWRITE, S_IRUSR | S_IWUSR); free(name, M_TEMP); if (error) return (error); --- 259,266 ---- name =3D expand_name(p->p_comm, p->p_ucred->cr_uid, p->p_pid); if (name =3D=3D NULL) return (EFAULT); /* XXX -- not the best error */ ! NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name, p); ! error =3D vn_open(&nd, O_CREAT | FWRITE | O_NOFOLLOW, S_IRUSR | S_IW= USR); free(name, M_TEMP); if (error) return (error); Here's the patch for FreeBSD-2.2.8-stable *** sys/LINK/fcntl.h Wed Dec 18 05:08:08 1996 --- sys/fcntl.h Fri Aug 27 14:39:26 1999 *************** *** 84,89 **** --- 84,90 ---- #define O_EXLOCK 0x0020 /* open with exclusive file lock */ #define O_ASYNC 0x0040 /* signal pgrp when data ready */ #define O_FSYNC 0x0080 /* synchronous writes */ + #define O_NOFOLLOW 0x0100 /* don't follow symlinks */ #endif #define O_CREAT 0x0200 /* create if nonexistent */ #define O_TRUNC 0x0400 /* truncate to zero length */ *** kern/LINK/kern_sig.c Sat Dec 21 10:57:24 1996 --- kern/kern_sig.c Fri Aug 27 14:38:25 1999 *************** *** 1241,1249 **** p->p_rlimit[RLIMIT_CORE].rlim_cur) return (EFAULT); sprintf(name, "%s.core", p->p_comm); ! NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, name, p); if ((error =3D vn_open(&nd, ! O_CREAT | FWRITE, S_IRUSR | S_IWUSR))) return (error); vp =3D nd.ni_vp; --- 1241,1249 ---- p->p_rlimit[RLIMIT_CORE].rlim_cur) return (EFAULT); sprintf(name, "%s.core", p->p_comm); ! NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name, p); if ((error =3D vn_open(&nd, ! O_CREAT | FWRITE | O_NOFOLLOW, S_IRUSR | S_IWUSR))) return (error); vp =3D nd.ni_vp; *** kern/LINK/vfs_vnops.c Sat Mar 8 07:16:18 1997 --- kern/vfs_vnops.c Fri Aug 27 14:37:01 1999 *************** *** 87,93 **** if (fmode & O_CREAT) { ndp->ni_cnd.cn_nameiop =3D CREATE; ndp->ni_cnd.cn_flags =3D LOCKPARENT | LOCKLEAF; ! if ((fmode & O_EXCL) =3D=3D 0) ndp->ni_cnd.cn_flags |=3D FOLLOW; error =3D namei(ndp); if (error) --- 87,93 ---- if (fmode & O_CREAT) { ndp->ni_cnd.cn_nameiop =3D CREATE; ndp->ni_cnd.cn_flags =3D LOCKPARENT | LOCKLEAF; ! if ((fmode & O_EXCL) =3D=3D 0 && (fmode & O_NOFOLLOW) =3D=3D 0) ndp->ni_cnd.cn_flags |=3D FOLLOW; error =3D namei(ndp); if (error) *************** *** 119,125 **** } } else { ndp->ni_cnd.cn_nameiop =3D LOOKUP; ! ndp->ni_cnd.cn_flags =3D FOLLOW | LOCKLEAF; error =3D namei(ndp); if (error) return (error); --- 119,126 ---- } } else { ndp->ni_cnd.cn_nameiop =3D LOOKUP; ! ndp->ni_cnd.cn_flags =3D ! ((fmode & O_NOFOLLOW) ? NOFOLLOW : FOLLOW) | LOCKLEAF; error =3D namei(ndp); if (error) return (error); *** kern/LINK/vfs_syscalls.c Wed Aug 4 12:44:30 1999 --- kern/vfs_syscalls.c Sat Aug 28 10:48:51 1999 *************** *** 694,699 **** --- 694,701 ---- flags =3D FFLAGS(uap->flags); if ((flags & FREAD + FWRITE) =3D=3D 0) return (EINVAL); + if (flags & O_NOFOLLOW) + flags &=3D ~O_NOFOLLOW; error =3D falloc(p, &nfp, &indx); if (error) return (error); =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D FreeBSD, Inc. Web Site: http://www.freebsd.org/ Confidential contacts: security-officerat_private Security notifications: security-notificationsat_private Security public discussion: freebsd-securityat_private PGP Key: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/public_key.a= sc Notice: Any patches in this document may not apply cleanly due to modifications caused by digital signature or mailer software. Please reference the URL listed at the top of this document for original copies of all patches if necessary. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D -----BEGIN PGP SIGNATURE----- Version: 2.6.3ia Charset: noconv Comment: Processed by Mailcrypt 3.4, an Emacs/PGP interface iQCVAwUBN+B44VUuHi5z0oilAQHkwwP9HeLkRJY/iXIYXUx8/A38EAxM/TAqxoiI ym7ZyktNtuCbum8ovCIfmkpnafaFyXmVSDhCX77LbIy+1clEBnelyueJ9TbKpBgU KWjTWmfj/7QsU2Ya/f7FK80ee8y7GjTTYxilnxxzTmM8ihHzFXrPHudoO4lTR7Op 2VII3pQVxOM=3D =3DbJXX -----END PGP SIGNATURE----- This is the moderated mailing list freebsd-announce. The list contains announcements of new FreeBSD capabilities, important events and project milestones. See also the FreeBSD Web pages at http://www.freebsd.org To Unsubscribe: send mail to majordomoat_private with "unsubscribe freebsd-announce" in the body of the message ----- End forwarded message ----- --=20 Patrick Oonk - PO1-6BONE - patrickat_private - www.pine.nl/~patrick Pine Internet B.V. PGP key ID BE7497F1 =20 Tel: +31-70-3111010 - Fax: +31-70-3111011 - http://www.pine.nl/ -- Pine Security Digest - http://security.pine.nl/ (Dutch) ---- Excuse of the day: The computer fletely, mouse and all. --GDLQamdgIxhPcIwq Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: 2.6.3ia iQB1AwUBN+COl/MOST2+dJfxAQEqrwL+NQr403Q1c0ry4k77WYu/HRrRb5y/WrtL F5RQMEc4PW+NhgP6//2c+6Qs93Pbt6gjqToiO1MYEXN8bz3cXvJQr5nlXwMWsp/p nOHzs8y99fqizsf8V5yxxfRDRqkfxEnn =5WJ9 -----END PGP SIGNATURE----- --GDLQamdgIxhPcIwq--
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