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Hash: SHA1 |
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Gentoo Linux Security Advisory GLSA 200404-01 |
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~ http://security.gentoo.org |
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|
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~ Severity: Normal |
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~ Title: Insecure sandbox temporary lockfile vulnerabilities in |
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~ Portage |
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~ Date: April 04, 2004 |
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~ Bugs: #21923 |
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~ ID: 200404-01 |
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|
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Synopsis |
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======== |
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|
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A flaw has been found in the temporary file handling algorithms for the |
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sandboxing code used within Portage. Lockfiles created during normal |
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Portage operation of portage could be manipulated by local users |
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resulting in the truncation of hard linked files; causing a Denial of |
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Service attack on the system. |
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|
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Background |
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========== |
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|
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Portage is Gentoo's package management system which is responsible for |
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installing, compiling and updating any ebuilds on the system through the |
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Gentoo rsync tree. Under default configurations, most ebuilds run under |
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a sandbox which prevent the build process writing to the "real" system |
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outside the build directory - packages are installed into a temporary |
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location and then copied over safely by Portage instead. During the |
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process the sandbox wrapper creates lockfiles in the /tmp directory |
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which are vulnerable to a hard-link attack. |
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|
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Affected packages |
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================= |
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|
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~ ------------------------------------------------------------------- |
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~ Package / Vulnerable / Unaffected |
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~ ------------------------------------------------------------------- |
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~ sys-apps/portage < 2.0.50-r3 >= 2.0.50-r3 |
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|
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Description |
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=========== |
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|
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A flaw in Portage's sandbox wrapper has been found where the temporary |
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lockfiles are subject to a hard-link attack which allows linkable files |
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to be overwritten to an empty file. This can be used to damage critical |
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files on a system causing a Denial of Service, or alternatively this |
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attack may be used to cause other security risks; for example firewall |
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configuration data could be overwritten without notice. |
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|
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The vulnerable sandbox functions have been patched to test for these new |
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conditions: namely; for the existance of a hard-link which would be |
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removed before the sandbox process would continue, for the existance of |
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a world-writable lockfile in which case the sandbox would also remove |
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it, and also for any mismatches in the UID ( anything but root ) and the |
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GID ( anything but the group of the sandbox process ). |
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|
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If the vulnerable files cannot be removed by the sandbox, then the |
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sandbox would exit with a fatal error warning the adminstrator of the |
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issue. The patched functions also fix any other sandbox I/O operations |
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which do not explicitly include the mentioned lockfile. |
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|
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Impact |
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====== |
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|
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Any user with write access to the /tmp directory can hard-link a file to |
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/tmp/sandboxpids.tmp - this file would eventually be replaced with an |
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empty one; effectively wiping out the file it was linked to as well with |
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no prior warning. This could be used to potentially disable a vital |
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component of the system and cause a path for other possible exploits. |
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|
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This vulnerability only affects systems that have /tmp on the root |
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partition: since symbolic link attacks are filtered, /tmp has to be on |
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the same partition for an attack to take place. |
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|
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Workaround |
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========== |
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|
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A workaround is not currently known for this issue. All users are |
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advised to upgrade to the latest version of Portage. |
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|
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Resolution |
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========== |
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|
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Users should upgrade to Portage 2.0.50-r3 or later: |
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|
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~ # emerge sync |
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|
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~ # emerge -pv ">=sys-apps/portage-2.0.50-r3" |
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~ # emerge ">=sys-apps/portage-2.0.50-r3" |
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|
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Concerns? |
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========= |
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|
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Security is a primary focus of Gentoo Linux and ensuring the |
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confidentiality and security of our users machines is of utmost |
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importance to us. Any security concerns should be addressed to |
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security@g.o or alternatively, you may file a bug at |
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http://bugs.gentoo.org. |
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