rsnapshot Security Information
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001 - chown() follow symlink bug
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rsnapshot Security Advisory 001 security@rsnapshot.org
http://www.rsnapshot.org/security/
Apr 10th, 2005 Nathan Rosenquist
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Severity: high
Vulnerability: local privilege escalation
Fix provided: yes
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1) Background
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rsnapshot is a filesystem snapshot utility for making backups of local and
remote systems.
Using rsync and hard links, it is possible to keep multiple, full backups
instantly available. The disk space required is just a little more than the
space of one full backup, plus incrementals.
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2) Problem description
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The copy_symlink() subroutine in rsnapshot incorrectly changes file
ownership on the files pointed to by symlinks, not on the symlinks
themselves. This would allow, under certain circumstances, an arbitrary
user to take ownership of a file on the main filesystem.
This subroutine is called under the following circumstances:
a) If the cmd_cp parameter has NOT been enabled, OR
b) If the backup_script parameter is set, and the backup script
generates symlinks as part of its output
c) AND if the attacker can create symlinks in a directory that is backed
up, either by creating them directly or influencing a backup script.
This vulnerability has been fixed in rsnapshot versions 1.1.7 and 1.2.1.
It is recommended that all users upgrade immediately.
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3) Upgrade Instructions
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For users of rsnapshot 1.2.0, download and install version 1.2.1.
For users of rsnapshot 1.1.6 or earlier, download and install version
1.1.7.
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rsnapshot 1.2.1
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http://www.rsnapshot.org/downloads/rsnapshot-1.2.1.tar.gz
http://www.rsnapshot.org/downloads/rsnapshot-1.2.1.tar.gz.asc
http://www.rsnapshot.org/downloads/rsnapshot-1.2.1-1.noarch.rpm
http://www.rsnapshot.org/downloads/rsnapshot-1.2.1-1.noarch.rpm.asc
http://www.rsnapshot.org/downloads/rsnapshot_1.2.1-1_all.deb
http://www.rsnapshot.org/downloads/rsnapshot_1.2.1-1_all.deb.asc
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rsnapshot 1.1.7
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http://www.rsnapshot.org/downloads/rsnapshot-1.1.7.tar.gz
http://www.rsnapshot.org/downloads/rsnapshot-1.1.7.tar.gz.asc
http://www.rsnapshot.org/downloads/rsnapshot-1.1.7-1.noarch.rpm
http://www.rsnapshot.org/downloads/rsnapshot-1.1.7-1.noarch.rpm.asc
http://www.rsnapshot.org/downloads/rsnapshot_1.1.7-1_all.deb
http://www.rsnapshot.org/downloads/rsnapshot_1.1.7-1_all.deb.asc
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4) Workarounds
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Enable the cmd_cp parameter (requires GNU cp, and works best on Linux).
Make sure any scripts specified by the backup_script parameter do not
create symlinks.
If you suspect you have discovered a security hole in rsnapshot, please send an e-mail to
security@rsnapshot.org.
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