TruBlueEnvironment Privilege Escalation Attack in Mac OS X Information: Computers running Mac OS X prior to 10.2.4 and unpatched contain a vulnerability that can be exploited to create files that can be run at evelated privileges because of the TruBlueEnvironment. Included is the security advisory covering the issue discovered by @Stake's Dave. For those unable to update they can change the permissions of the vulnerable files to the admin group. sudo chown .admin /System/Library/CoreServices/Classic\ Startup.app/Contents/Resources/TruBlueEnvironment sudo chmod 4750 /System/Library/CoreServices/Classic\ Startup.app/Contents/Resources/TruBlueEnvironment @stake, Inc. www.atstake.com Security Advisory Advisory Name: TruBlueEnvironment Privilege Escalation Attack Release Date: 02/14/2003 Application: TruBlueEnvironment Platform: MacOS X (10.2.3 and below) Severity: Local users can gain root privileges Author: Dave G. Vendor Status: updated version of OS available CVE Candidate: CAN-2003-XXXX Reference: www.atstake.com/research/advisories/2003/a021403-1.txt Overview: TruBlueEnvironment is part of the MacOS Classic Emulator. It is setuid root and installed by default. By setting certain environment variables, it is possible to overwrite any file on the system, or create arbitrary files owned as root with the attacker's umask. This vulnerability can be leveraged to create files that will get executed by root through the cron facility. Details: TruBluEnvironment uses an environment variable to determine where to write out debugging information. Local users can set this to environment variable to point at any file on the filesystem. If the file exists, it will be reset to zero bytes. If the file does not exist, it will be created with the umask inherited from the calling process. While attackers cannot create files with execute permissions set, they can create files that are world writable. Under MacOS X, this vulnerability can be used to create files that will be run automatically via cron. By default, cron will launch maintenance scripts using the periodic command. This command will take several files and either 'source' them or run them through a shell interpreter. Since these scripts are running as root, it is possible to obtain administrator privileges on any MacOS X system running cron and TruBlueEnvironment. Vendor Response: Classic: The Mac OS X 10.2.4 release fixes CAN-2003-0088, where an attacker may change an environment variable to create arbitrary files or overwrite existing files, which could lead to obtaining elevated privileges. Credit to Dave G. from @stake, Inc. for discovering this issue. Recommendation: If possible upgrade to Mac OS X 10.2.4. Another solution is to restrict access to the TruBlueEnvironment(*) executable, or remove it entirely if it is not being used. One approach to restricting access would be to remove global execute permissions from the TruBlueEnvironment executable, and only allow a specific group to execute the application. The following commands will restrict access to the 'admin' group: sudo chown .admin /System/Library/CoreServices/Classic\ Startup.app/Contents/Resources/TruBlueEnvironment sudo chmod 4750 /System/Library/CoreServices/Classic\ Startup.app/Contents/Resources/TruBlueEnvironment (*) Located in /System/Library/CoreServices/Classic Startup.app/Contents/Resources/TruBlueEnvironment Common Vulnerabilities and Exposures (CVE) Information: The Common Vulnerabilities and Exposures (CVE) project has assigned the following names to these issues. These are candidates for inclusion in the CVE list (http://cve.mitre.org), which standardizes names for security problems. CAN-2003-0088 @stake Vulnerability Reporting Policy: http://www.atstake.com/research/policy/ @stake Advisory Archive: http://www.atstake.com/research/advisories/ PGP Key: http://www.atstake.com/research/pgp_key.asc Copyright 2003 @stake, Inc. All rights reserved. Interact: Could not connect