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Timezone Vulnerability
There is a flaw in lockdownd:
MOVW R0, #(aPrivateVarDbTi-0x4DB8A) ; "/private/var/db/timezone" MOVW R1, #0x1FF ; mode_t -> 0777 MOVT.W R0, #4 ADD R0, PC ; char * BLX _chmod
This means chmod("/private/var/db/timezone",0777) without any further checks and is executed on every launch. By setting a symbolic link on /var/db/timezone though MobileBackup and pointing the symlink to any other file and crashing lockdownd by sending it a malformed property list to make it relaunch (another probably non-exploitable vulnerability) causes it to perform the actual permission change on any file.
This vulnerability is CVE-2013-0979 and Apple describes it in the iOS 6.1.3 security fixes like this:
Lockdown
Impact: A local user may be able to change permissions on arbitrary files
Description: When restoring from backup, lockdownd changed permissions on certain files even if the path to the file included a symbolic link. This issue was addressed by not changing permissions on any file with a symlink in its path.
