/var/tmp et all are written to disk
On tempfs, content is lost at poweroff, preventing the MSS, FBI or other thieves from reading what was stored there. On the other hand, /var/log and /var/tmp are on disk. If logs were on RAM, you'd lose your logs at every reboot, making some things impossible to diagnose. KDE at least used to store emails in /var/tmp, a serious security issue when /home is encrpyted. A simple workaround for this is to create directories owned by root in /home and bind mount them on /var/tmp, /var/spool (print jobs, etc) and /var/log (records of what you mounted, etc). That's what I did before I switched to encrypting everything but /boot, something I did to reduce the attack surface for an enemy installing malicious software to a powered down machine.
With only /boot encrypted, there are ways to check post-boot for tampering. You can counter that checking with a smart enough "evil maid" attack, but that requires knowing what you are up against, etc and at that point a BIOS or hardware keylogger gets easier to install. There are of course detection methods and defenses for those as well.
Do keep in mind I use encryption to foil governmental forensics, if protecting your data from street thieves other than organized crime is your reason for encrypting a computer you may need less security than that required to defeat the FBI and Secret Service and especially less than that needed to defeat the NSA. Speaking of that, if the NSA was ever able to decrypt a randomly picked disk encrypted with AES dropped into their laps, there would soon be stories about US government and military contractors being told not to use AES anymore, for fear of other governments also finding the same crack. As of now they are permitted to use it even for Top Secret stuff.
Originally posted by russofris
View Post
With only /boot encrypted, there are ways to check post-boot for tampering. You can counter that checking with a smart enough "evil maid" attack, but that requires knowing what you are up against, etc and at that point a BIOS or hardware keylogger gets easier to install. There are of course detection methods and defenses for those as well.
Do keep in mind I use encryption to foil governmental forensics, if protecting your data from street thieves other than organized crime is your reason for encrypting a computer you may need less security than that required to defeat the FBI and Secret Service and especially less than that needed to defeat the NSA. Speaking of that, if the NSA was ever able to decrypt a randomly picked disk encrypted with AES dropped into their laps, there would soon be stories about US government and military contractors being told not to use AES anymore, for fear of other governments also finding the same crack. As of now they are permitted to use it even for Top Secret stuff.
Comment