How can one detect being in a chroot jail without root privileges? Assume a standard BSD or Linux system. The best I came up with was to look at the inode value for ‘/’ and to consider whether it is reasonably low, but I would like a more accurate method for detection.
[edit 20080916 142430 EST] Simply looking around the filesystem isn’t sufficient, as it’s not difficult to duplicate things like /boot and /dev to fool the jailed user.
[edit 20080916 142950 EST] For Linux systems, checking for unexpected values within /proc is reasonable, but what about systems that don’t support /proc in the first place?
The inode for / will always be 2 if it’s the root directory of an ext2/ext3/ext4 filesystem, but you may be chrooted inside a complete filesystem. If it’s just chroot (and not some other virtualization), you could run mount and compare the mounted filesystems against what you see. Verify that every mount point has inode 2.