This document describes a method for generating automatic rotating "snapshot"-style backups on a Unix-based system, with specific examples drawn from the author's GNU/Linux experience. Snapshot backups are a feature of some high-end industrial file servers; they create the illusion of multiple, full backups per day without the space or processing overhead. All of the snapshots are read-only, and are accessible directly by users as special system directories. . It is often possible to store several hours, days, and even weeks' worth of snapshots with slightly more than 2x storage. This method, while not as space-efficient as some of the proprietary technologies (which, using special copy-on-write filesystems, can operate on slightly more than 1x storage), makes use of only standard file utilities and the common rsync program, which is installed by default on most Linux distributions. Properly configured, the method can also protect against hard disk failure, root compromises, or even back up a network of heterogeneous desktops automatically. The link for this article located at is no longer available. . It is often possible to store several hours, days, and even weeks' worth of snapshots with slightly . document, describes, method, generating, automatic, rotating, 'snapshot'-style, backups. . LinuxSecurity.com Team
The rsync team has received evidence that a vulnerability in rsync was recently used in combination with a Linux kernel vulnerability to compromise the security of a public rsync server. While the forensic evidence we have is incomplete, we have pieced together the most likely way that this attack was conducted and we are releasing this advisory as a result of our investigations to date.. . .. The rsync team has received evidence that a vulnerability in rsync was recently used in combination with a Linux kernel vulnerability to compromise the security of a public rsync server. While the forensic evidence we have is incomplete, we have pieced together the most likely way that this attack was conducted and we are releasing this advisory as a result of our investigations to date. Background The rsync team has received evidence that a vulnerability in rsync was recently used in combination with a Linux kernel vulnerability to compromise the security of a public rsync server. While the forensic evidence we have is incomplete, we have pieced together the most likely way that this attack was conducted and we are releasing this advisory as a result of our investigations to date. Our conclusions are that: rsync version 2.5.6 contains a heap overflow vulnerability that can be used to remotely run arbitrary code. While this heap overflow vulnerability could not be used by itself to obtain root access on a rsync server, it could be used in combination with the recently announced brk vulnerability in the Linux kernel to produce a full remote compromise. The server that was compromised was using a non-default rsyncd.conf option "use chroot = no". The use of this option made the attack on the compromised server considerably easier. A successful attack is almost certainly still possible without this option, but it would be much more difficult. Please note that this vulnerability only affects the use of rsync as a "rsync server". To see if you are running a rsync server you should use the netstatcommand to see if you are listening on TCP port 873. If you are not listening on TCP port 873 then you are not running a rsync server. New rsync release In response we have released a new version of rsync, version 2.5.7. This is based on the current stable 2.5.6 release with only the changes necessary to prevent this heap overflow vulnerability. There are no new features in this release. We recommend that anyone running a rsync server take the following steps: Update to rsync version 2.5.7 immediately If you are running a Linux kernel prior to version 2.4.23 then you should upgrade your kernel immediately. Note that some distribution vendors may have patched versions of the 2.4.x series kernel that fix the brk vulnerability in versions before 2.4.23. Check with your vendor security site to ensure that you are not vulnerable to the brk problem. Review your /etc/rsyncd.conf configuration file. If you are using the option "use chroot = no" then remove that line or change it to "use chroot = yes". If you find that you need that option for your rsync service then you should disable your rsync service until you have discussed a workaround with the rsync maintainers on the rsync mailing list. The disabling of the chroot option should not be needed for any normal rsync server. The patches and full source for rsync version 2.5.7 are available from / and mirror sites. We expect that vendors will produce updated packages for their distributions shortly. Credits The rsync team would like to thank the following individuals for their assistance in investigating this vulnerability and producing this response: Mike Warfield Paul Russell Andrea Barisani Regards, The rsync team . Secure your server: exploit on Rsync discovered due to Linux kernel weakness; prompt measures essential.. rsync Vulnerability, Heap Overflow, Remote Access, Server Security, Linux Flaw. . LinuxSecurity.com Team
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