-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ============================================================================= FreeBSD-SA-08:01.pty Security Advisory The FreeBSD Project Topic: pty snooping Category: core Module: libc_stdlib / libutil Announced: 2008-01-14 Credits: John Baldwin Affects: FreeBSD 5.0 and later. Corrected: 2008-01-14 22:57:45 UTC (RELENG_7, 7.0-PRERELEASE) 2008-01-14 22:55:54 UTC (RELENG_7_0, 7.0-RC2) 2008-01-14 22:56:05 UTC (RELENG_6, 6.3-PRERELEASE) 2008-01-14 22:56:18 UTC (RELENG_6_3, 6.3-RELEASE) 2008-01-14 22:56:44 UTC (RELENG_6_2, 6.2-RELEASE-p10) 2008-01-14 22:56:56 UTC (RELENG_6_1, 6.1-RELEASE-p22) 2008-01-14 22:57:06 UTC (RELENG_5, 5.5-STABLE) 2008-01-14 22:57:19 UTC (RELENG_5_5, 5.5-RELEASE-p18) CVE Name: CVE-2008-0216, CVE-2008-0217 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit . I. Background pt_chown is a setuid root support utility used by grantpt(3) to change ownership of a tty. openpty(3) is a support function in libutil which is used to obtain a pseudo-terminal. script(1) is a utility which makes a typescript of everything printed on a terminal. II. Problem Description Two issues exist in the FreeBSD pty handling. If openpty(3) is called as non-root user the newly created pseudo-terminal is world readable and writeable. While this is documented to be the case, script(1) still uses openpty(3) and script(1) may be used by non-root users [CVE-2008-0217]. The ptsname(3) function incorrectly extracts two characters from the name of a device node in /dev without verifying that it's actually operating on a valid pty which the calling user owns. pt_chown uses the bad result from ptsname(3) to change ownership of a pty to the user calling pt_chown [CVE-2008-0216]. III. Impact If an unprivileged user is running script(1), or another program which uses openpty(3), an attacker may snoop text which is printed to the users terminal. If a malicious user has read access to a device node with characters in the device name that match the name of a pty, then the malicious user can read the content of the pty from another user. The malicious user can open a lot of tty's resulting in a high probabilty of a new user obtaining the pty name of a "vulnerable" pty. NOTE WELL: If a user snoops a pty the snooped text will not be shown to the real user, which in many cases mean the real owner of the pty will be able to know the attack is taking place. IV. Workaround Do not run script(1) as a non-root user. The ptsname(3) issue only affects FreeBSD 6.0 and newer. V. Solution Perform one of the following: 1) Upgrade your vulnerable system to 5-STABLE, 6-STABLE, or 7.0-PRERELEASE, or to the RELENG_7_0, RELENG_6_3, RELENG_6_2, RELENG_6_1, or RELENG_5_5 security branch dated after the correction date. 2) To patch your present system: The following patches have been verified to apply to FreeBSD 5.5, 6.1, 6.2, 6.3, and 7.0 systems. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. [FreeBSD 5.5] # fetch http://security.FreeBSD.org/patches/SA-08:01/pty5.patch # fetch http://security.FreeBSD.org/patches/SA-08:01/pty5.patch.asc [FreeBSD 6.x] # fetch http://security.FreeBSD.org/patches/SA-08:01/pty6.patch # fetch http://security.FreeBSD.org/patches/SA-08:01/pty6.patch.asc [FreeBSD 7.0] # fetch http://security.FreeBSD.org/patches/SA-08:01/pty7.patch # fetch http://security.FreeBSD.org/patches/SA-08:01/pty7.patch.asc b) Execute the following commands as root: # cd /usr/src # patch < /path/to/patch c) Recompile the operating system as described in and reboot the system. VI. Correction details The following list contains the revision numbers of each file that was corrected in FreeBSD. Branch Revision Path - ------------------------------------------------------------------------- RELENG_5 src/lib/libutil/pty.c 1.15.4.1 RELENG_5_5 src/UPDATING 1.342.2.35.2.18 src/sys/conf/newvers.sh 1.62.2.21.2.20 src/lib/libutil/pty.c 1.15.16.1 RELENG_6 src/lib/libc/stdlib/grantpt.c 1.4.2.2 src/lib/libutil/pty.c 1.15.10.2 RELENG_6_3 src/UPDATING 1.416.2.37.2.3 src/sys/conf/newvers.sh 1.69.2.15.2.3 src/lib/libc/stdlib/grantpt.c 1.4.10.2 src/lib/libutil/pty.c 1.15.20.2 RELENG_6_2 src/UPDATING 1.416.2.29.2.13 src/sys/conf/newvers.sh 1.69.2.13.2.13 src/lib/libc/stdlib/grantpt.c 1.4.8.1 src/lib/libutil/pty.c 1.15.18.1 RELENG_6_1 src/UPDATING 1.416.2.22.2.24 src/sys/conf/newvers.sh 1.69.2.11.2.24 src/lib/libc/stdlib/grantpt.c 1.4.6.1 src/lib/libutil/pty.c 1.15.14.1 RELENG_7 src/lib/libc/stdlib/grantpt.c 1.7.2.4 src/lib/libutil/pty.c 1.17.2.3 RELENG_7_0 src/UPDATING 1.507.2.3.2.1 src/sys/conf/newvers.sh 1.72.2.5.2.2 src/lib/libc/stdlib/grantpt.c 1.7.2.2.2.2 src/lib/libutil/pty.c 1.17.2.2.2.1 - ------------------------------------------------------------------------- VII. References http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-0216 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-0217 The latest revision of this advisory is available at http://security.FreeBSD.org/advisories/FreeBSD-SA-08:01.pty.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (FreeBSD) iD8DBQFHi+nfFdaIBMps37IRAhtUAJ9GXtRjTIxcbrCOxoMnO50ZLc5mAgCdGSyO D83MVnUtP9rhzD2JfOPbaOw= =V/kt -----END PGP SIGNATURE-----