This file is indexed.

/lib/cryptsetup/scripts/decrypt_derived is in cryptsetup 2:1.4.1-2ubuntu4.

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
#!/bin/sh

# WARNING: If you use the decrypt_derived keyscript for devices with
# persistent data (i.e. not swap or temp devices), then you will lose
# access to that data permanently if something damages the LUKS header
# of the LUKS device you derive from. The same applies if you luksFormat
# the device, even if you use the same passphrase(s). A LUKS header 
# backup, or better a backup of the data on the derived device may be 
# a good idea. See the Cryptsetup FAQ on how to do this right.

countlines() {
	local IFS input count tmp
	input="$1"
	count=0
	IFS='
'
	for tmp in $input; do
		count=$(( $count + 1 ))
	done
	echo $count
}

if [ -z "$1" ]; then
	echo "$0: must be executed with a crypto device as argument" >&2
	exit 1
fi

if ! device=$(dmsetup --showkeys table 2> /dev/null | grep "^$1:"); then
	echo "$0: failed to find $1 in dmtable" >&2
	exit 1
fi

if [ -z "$device" ]; then
	echo "$0: device $1 doesn't exist" >&2
	exit 1
fi

count=$(countlines "$device")
if [ $count -ne 1 ]; then
	echo "$0: more than one device match $1" >&2
	exit 1
fi

eval set -- $device
type="$4"
key="$6"

if [ "$type" != "crypt" ]; then
	echo "$0: device $1 is not a crypto device" >&2
	exit 1
fi

echo -n "$key"
exit 0