Published:
21 April 1999
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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-1999.055 -- NetBSD Security Advisory 1999-009 SVR4 compatibility device creation vulnerability 22 April 1999 =========================================================================== The NetBSD Foundation, Inc. has released the following advisory concerning a vulnerability in the i386 port of NetBSD with SVR4 emulation additionally configured. This vulnerability may allow users to arbitrarily read or write any data stored on the NetBSD portion of the first IDE disk configured by the system. - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- NetBSD Security Advisory 1999-009 ================================= Topic: SVR4 compatibility device creation vulnerability Version: NetBSD 1.3.3 and prior; NetBSD-current until 19990420 Severity: Local users can access and modify any data on first IDE disk Abstract ======== In order to provide a system environment capable of executing System V Release 4 (`SVR4') binaries, it is necessary to create a set of device special files; to simplify this task, a shell script is shipped with the system. Due to a mismatch of device major numbers between NetBSD platforms, one device special file is erroneously created with a wrong major number, which may allow a regular user to arbitrarily read or write any data stored on the NetBSD portion of the first IDE disk configured by the system. This vulnerability is restricted to the i386 port of NetBSD with SVR4 emulation additionally configured only. Technical Details ================= The SVR4 /dev/wabi character device special file, usually created below the /emul/svr4 hierarchy, is currently supposed to be a synonym for the /dev/null device special file. Originally developed on the sparc port of NetBSD, the SVR4_MAKEDEV shell script creates this file with a major number of 3 and a minor number of 2, setting these properties equivalent to those of the /dev/null device special file on that platform. On the i386 port of NetBSD, the character device major number 3 is associated with the wd(4) driver, which supports IDE (and compatible) disks, and whose minor number 2 denotes the NetBSD portion of the first such disk configured by the systems; this corresponds to the special device file /dev/rwd0c in the base distribution. As the /dev/wabi special device file is created with world read and write permissions, a regular user may read and write any data stored on that portion of the disk. The effects of actually running the WABI software on a vulnerable system have not been investigated. Solutions and Workarounds ========================= A patch is available for the NetBSD 1.3.3 which makes the SVR4_MAKEDEV shell script create the wabi device special file with the correct properties. You may find this patch on the NetBSD ftp server: ftp://ftp.NetBSD.ORG/pub/NetBSD/misc/security/patches/19990419-SVR4_MAKEDEV NetBSD-current since 19990420 is not vulnerable. Users of NetBSD-current should upgrade to a source tree later than 19990420. Once the SVR4_MAKEDEV script is updated, re-run it to recreate the wabi device with the correct parameters. If this action cannot be taken, an immediate workaround is to remove the existing device special file and creating a new one, which can be done by executing the following shell command sequence as the super-user: # /bin/rm -f /emul/svr4/dev/wabi # /sbin/mknod /emul/svr4/dev/wabi c 2 2 # /bin/chmod u=rw,g=rw,o=rw /emul/svr4/dev/wabi Thanks To ========= The vulnerability was discovered by Klaus Klein <kleink@ira.uka.de>, who also provided the solution and authored this advisory. Revision History ================ 1999/04/17 - initial version 1999/04/19 - dates were incorrect More Information ================ Information about NetBSD and NetBSD security can be found at http://www.NetBSD.ORG/ and http://www.NetBSD.ORG/Security/. Copyright 1999, The NetBSD Foundation, Inc. All Rights Reserved. $NetBSD: NetBSD-SA1999-009.txt,v 1.2 1999/04/19 15:07:52 mrg Exp $ - -----BEGIN PGP SIGNATURE----- Version: 2.6.3ia Charset: noconv iQCVAwUBNxwkvz5Ru2/4N2IFAQEbuQQAtv2ho3MWYYihmZBagGnX6Wd0KD+mTIh0 liV32yx46kVELmCGrS4pEQh3fBNNgYkYBjympKrC/Iy1Vj9DMAMBNLGedFu10yXT oJnKLcmNmjEE8qRnqwjBRUIn/kURvG6wakgC9n6OuCOIcdtYeiUmgFhoPyl4lzKf FRpxHkqZnLo= =9Ypx - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to use any or all of this information is the responsibility of each user or organisation, and should be done so in accordance with site policies and procedures. NOTE: This is only the original release of the security bulletin. It will not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the original authors to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/Information/advisories.html If you believe that your system has been compromised, contact AusCERT or your representative in FIRST (Forum of Incident Response and Security Teams). Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). 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