HP-UX shar utility creates files with predictable names in "/tmp" directory

2004-01-23T00:00:00
ID VU:509454
Type cert
Reporter CERT
Modified 2004-01-23T16:12:00

Description

Overview

The shar program distributed with some versions of the HP-UX operating system creates files insecurely. This vulnerability could allow local users to gain escalated privilege on the system.

Description

shar is a program commonly available on UNIX systems to create a shell script that will recreate a file hierarchy specified by the command line operands. The shar program is often used for distributing a directory of files by FTP or email. The shar program distributed with some versions of the HP-UX operating system creates files with predictable names in the /tmp directory. In environments where multiple users have write access to the /tmp directory, this behavior could be exploited by an attacker to overwrite files with another user's privileges.


Impact

An attacker with the ability to create symbolic links for predictable filenames in the /tmp directory may be able to overwrite files owned by another user. When a shell script generated by the flawed version of the shar program is executed, the symbolic links would be followed and the target files created with the permissions of the user who ran the script.


Solution

Apply a patch from the vendor

Patches that address this vulnerability have been released. Please see the vendor information in the Systems Affected section of this document for more details.

NOTE: After the patches have been applied, Hewlett-Packard recommends that users always specify a secure directory in the TMPDIR environment variable when creating shar archives. Hewlett-Packard also states that shar archives created with previous versions of the shar program will still use the /tmp directory even after the recommended patches are installed. Users are encouraged to inspect existing shar archives and replace references to /tmp with $TMPDIR. This can be accomplished by manually editing the files or with the simple script provided in the Hewlett-Packard bulletin.


Vendor Information

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Hewlett-Packard Company

Updated: January 22, 2004

Status

__ Vulnerable

Vendor Statement

HP Support Information Digests

=============================================================================== o Security Bulletin Digest Split ------------------------------

` The security bulletins digest has been split into multiple digests
based on the operating system (HP-UX, MPE/iX, and HP Secure OS
Software for Linux). You will continue to receive all security
bulletin digests unless you choose to update your subscriptions.

To update your subscriptions, use your browser to access the
IT Resource Center on the World Wide Web at:`

``<http://support.itrc.hp.com/>

Under the Maintenance and Support Menu, click on the "more..." link. Then use the 'login' link at the left side of the screen to login using your IT Resource Center User ID and Password.

Under the notifications section (near the bottom of the page), select ITRC Maintenance/Support.

To subscribe or unsubscribe to a specific security bulletin digest, select or unselect the checkbox beside it. Then click the "Update Subscriptions" button at the bottom of the page.

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If you subscribed through the IT Resource Center and would like to be REMOVED from this mailing list, access the IT Resource Center on the World Wide Web at:

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Login using your IT Resource Center User ID and Password. Then select ITRC Maintenance/Support (located under Maintenance and Support). You may then unsubscribe from the appropriate digest. ===============================================================================

Digest Name: daily HP-UX security bulletins digest Created: Tue Dec 2 6:19:32 EST 2003

Table of Contents:

`Document ID Title


HPSBUX0312-304 SSRT3630 Security Vulnerability in shar(1)`

The documents are listed below. -------------------------------------------------------------------------------

Document ID: HPSBUX0312-304 Date Loaded: 20031201 Title: SSRT3630 Security Vulnerability in shar(1)

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1

----------------------------------------------------------------- Source: HEWLETT-PACKARD COMPANY SECURITY BULLETIN: HPSBUX0312-304 Originally issued: 01 Dec 2003 SSRT3630 Security Vulnerability in shar(1) -----------------------------------------------------------------

NOTICE: There are no restrictions for distribution of this Bulletin provided that it remains complete and intact.

The information in the following Security Bulletin should be acted upon as soon as possible. Hewlett-Packard Company will not be liable for any consequences to any customer resulting from customer's failure to fully implement instructions in this Security Bulletin as soon as possible.

----------------------------------------------------------------- PROBLEM: shar(1) creates tmp files insecurely.

IMPACT: Possible filesystem damage, execution of arbitrary code, or Denial of Service.

PLATFORM: HP9000 servers running HP-UX versions B.11.00, B.11.04, and B.11.11.

SOLUTION: Apply the appropriate patch from itrc.hp.com: PHCO_29010 B.11.11 PHCO_29697 B.11.04 PHCO_28954 B.11.00

MANUAL ACTIONS: Yes If the /tmp directory is not trusted specify a trusted directory in the TMPDIR environment variable. Shar archives which do not use TMPDIR should be modified as discussed below.

`AVAILABILITY: All patches are available now on <itrc.hp.com>

A. Background
The shar(1) utility, which among other things is used to
package HP-UX patches, creates temporary files with
predictable names on /tmp. If shar files are unpacked on
a system where /tmp cannot be trusted a potential
vulnerability exists.`

Shar archives created with the new version of shar(1) can specify a safe directory for temporary file creation using the TMPDIR environment variable. Shar archives created with previous versions of shar(1) will still use /tmp even after the recommended patches are installed.

There are additions to the man page for shar(1) describing the new environment variable TMPDIR.

The following procedure can be used to replace references to /tmp with TMPDIR in existing shar archives.

$ cat addTMPDIR.awk /..@EOF/ {scan_off=1} /^@EOF/ {scan_off=0} /unpacker &lt;&lt;.@eof./ {scan_off=1} { if(scan_off != 1) { gsub ("/tmp", "$TMPDIR") } print $0 }

$ cp PHCO_29010 PHCO_29010.orig $ export TMPDIR=$HOME $ awk -f addTMPDIR.awk PHCO_29010.orig &gt;PHCO_29010 $ sh PHCO_29010 x - PHCO_29010.text x - PHCO_29010.depot [non-ascii]

NOTE: This issue does not impact HP Tru64 UNIX nor HP NonStop Servers.

AFFECTED VERSIONS The following is a list by HP-UX revision of affected filesets and the fileset revision or patch containing the fix. To determine if a system has an affected version, search the output of "swlist -a revision -l fileset" for an affected fileset, then determine if a fixed revision or the applicable patch is installed.

` HP-UX B.11.11

OS-Core.CMDS-AUX
fix: install PHCO_29010 or subsequent and unpack patches
using the new procedure.`

` HP-UX B.11.04

OS-Core.CMDS-AUX
fix: install PHCO_29697 or subsequent and unpack patches
using the new procedure.`

` HP-UX B.11.00

OS-Core.CMDS-AUX
fix: install PHCO_28954 or subsequent and unpack patches
using the new procedure.`

END AFFECTED VERSIONS

B. Recommended solution

Retrieve and install the patches for each applicable release from &lt;itrc.hp.com&gt;:

PHCO_29010 B.11.11 PHCO_29697 B.11.04 PHCO_28954 B.11.00

C. To subscribe to automatically receive future NEW HP Security Bulletins from the HP IT Resource Center via electronic mail, do the following:

Use your browser to get to the HP IT Resource Center page at:

``&lt;http://itrc.hp.com&gt;

Use the 'Login' tab at the left side of the screen to login using your ID and password. Use your existing login or the "Register" button at the left to create a login, in order to gain access to many areas of the ITRC. Remember to save the User ID assigned to you, and your password.

In the left most frame select "Maintenance and Support".

Under the "Notifications" section (near the bottom of the page), select "Support Information Digests".

To -subscribe- to future HP Security Bulletins or other Technical Digests, click the check box (in the left column) for the appropriate digest and then click the "Update Subscriptions" button at the bottom of the page.

or

To -review- bulletins already released, select the link (in the middle column) for the appropriate digest.

NOTE: Using your itrc account security bulletins can be found here: ``&lt;http://itrc.hp.com/cki/bin/doc.pl/screen=ckiSecurityBulletin&gt;

To -gain access- to the Security Patch Matrix, select the link for "The Security Bulletins Archive". (near the bottom of the page) Once in the archive the third link is to the current Security Patch Matrix. Updated daily, this matrix categorizes security patches by platform/OS release, and by bulletin topic. Security Patch Check completely automates the process of reviewing the patch matrix for 11.XX systems. Please note that installing the patches listed in the Security Patch Matrix will completely implement a security bulletin _only_ if the MANUAL ACTIONS field specifies "No."

The Security Patch Check tool can verify that a security bulletin has been implemented on HP-UX 11.XX systems providing that the fix is completely implemented in a patch with no manual actions required. The Security Patch Check tool cannot verify fixes implemented via a product upgrade.

For information on the Security Patch Check tool, see: ``&lt;http://www.software.hp.com/cgi-bin/swdepot_parser.cgi/cgi/&gt;`` displayProductInfo.pl?productNumber=B6834AA

The security patch matrix is also available via anonymous ftp:

``&lt;ftp://ftp.itrc.hp.com/export/patches/hp-ux_patch_matrix/&gt;

On the "Support Information Digest Main" page: click on the "HP Security Bulletin Archive".

The PGP key used to sign this bulletin is available from several PGP Public Key servers. The key identification information is:

2D2A7D59 HP Security Response Team (Security Bulletin signing only) &lt;security-alert@hp.com&gt; Fingerprint = 6002 6019 BFC1 BC62 F079 862E E01F 3AFC 2D2A 7D59

If you have problems locating the key please write to security-alert@hp.com. Please note that this key is for signing bulletins only and is not the key returned by sending 'get key' to security-alert@hp.com.

D. To report new security vulnerabilities, send email to

security-alert@hp.com

Please encrypt any exploit information using the security-alert PGP key, available from your local key server, or by sending a message with a -subject- (not body) of 'get key' (no quotes) to security-alert@hp.com.

-----------------------------------------------------------------

(c)Copyright 2003 Hewlett-Packard Company Hewlett-Packard Company shall not be liable for technical or editorial errors or omissions contained herein. The information in this document is subject to change without notice. Hewlett-Packard Company and the names of HP products referenced herein are trademarks and/or service marks of Hewlett-Packard Company. Other product and company names mentioned herein may be trademarks and/or service marks of their respective owners. ________________________________________________________________

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Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

NOTE: The Hewlett-Packard bulletin included above states that shar archives created with previous versions of the shar program will still use the /tmp directory even after the recommended patches are installed. Users are encouraged to inspect existing shar archives and replace references to /tmp with $``TMPDIR either manually or with a script.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

CVSS Metrics

Group | Score | Vector
---|---|---
Base | N/A | N/A
Temporal | N/A | N/A
Environmental | | N/A

References

<http://www.secunia.com/advisories/10339/>

Acknowledgements

Thanks to the Hewlett-Packard Company for reporting this vulnerability.

This document was written by Chad R Dougherty.

Other Information

CVE IDs: | None
---|---
Severity Metric:** | 2.13
Date Public:
| 2003-12-02
Date First Published: | 2004-01-23
Date Last Updated: | 2004-01-23 16:12 UTC
Document Revision: | 7