/usr/bin/ecryptfs-find is in ecryptfs-utils 111-0ubuntu1.1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | #!/bin/sh -e
#
#    ecryptfs-find - use inode numbers to match encrypted/decrypted filenames
#    Copyright (C) 2011 Dustin Kirkland
#    Copyright (C) 2011 Sergio Mena de la Cruz
#
#    Authors: Dustin Kirkland <kirkland@ubuntu.com>
#             Sergio Mena de la Cruz
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, version 2 of the License.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
if [ ! -e "$1" ]; then
	echo "ERROR: [$1] not found" 1>&2
	exit 1
fi
# Use one utility for both directions; same method is used
case "$1" in
	*ECRYPTFS_FNEK_ENCRYPTED.*)
		direction="decrypt"
	;;
	*)
		direction="encrypt"
	;;
esac
# Grab the target inode number
inum=$(ls -aid "$1" | awk '{print $1}')
mounts=
# Process /proc/mounts
while read lower upper fstype opts dump pass; do
	[ "$fstype" = "ecryptfs" ] || continue
	if [ "$direction" = "encrypt" ]; then
		find="$lower"
	else
		find="$upper"
	fi
	# Match against filesystem or mountpoint, build list of
	# mounts to search
	if [ -r "$find" ] && [ -x "$find" ]; then
		mounts="$mounts $find"
	fi
done < /proc/mounts
# Do the search
for m in $mounts; do
	find "$m/" -inum "$inum"
done
 |