Date: Tue, 22 Jul 2014 14:00:03 -0700 (PDT) From: Raphael Geissert <geissert@...ian.org> To: Open Source Security <oss-security@...ts.openwall.com> Subject: ecryptfs-setup-private nitpick Hi, Taking a look at ecryptfs-utils 103's ecryptfs-setup-private, there is a bit of code that writes the mount pass to a file in /dev/shm hoping to "keep it from leaking to the hard-drive": 8<-------->8 # This will be wrapped by pam_ecryptfs's chauthtok as soon as the user # chooses a password. Until that happens (hopefully soon), standard # file permissions (600) are all that's protecting it. Write it to # ramdisk, to keep it from leaking to the hard-drive. temp=`mktemp /dev/shm/.ecryptfs-XXXXXX` printf "%s" "$MOUNTPASS" > "$temp" mv -f -T "$temp" "/dev/shm/.ecryptfs-$USER" || error "Could not create passphrase file" 8<-------->8 Fastforward to 2014 and /dev/shm is, well, not a ramfs/ramdisk: /dev/shm -> /run/shm, which is a tmpfs at least on Debian. And as clearly stated by Documentation/filesystems/tmpfs.txt: "If you compare it to ramfs (which was the template to create tmpfs) you gain swapping and limit checking." So in the hope of avoiding a persistent storage the mount pass is written to a file in a tmpfs that can be swapped to... disk. The file is left on /dev/shm until pam_ecryptfs actually wraps it with the login pass. Cheers, -- Raphael Geissert - Debian Developer www.debian.org - get.debian.net
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