#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright 2020 Google LLC
#
# FS QA Test No. 613
#
# Test that encryption nonces are unique and random, where randomness is
# approximated as "incompressible by the xz program".
#
# An encryption nonce is the 16-byte value that the filesystem generates for
# each encrypted file.  These nonces must be unique in order to cause different
# files to be encrypted differently, which is an important security property.
# In practice, they need to be random to achieve that; and it's easy enough to
# test for both uniqueness and randomness, so we test for both.
#
seq=`basename $0`
seqres=$RESULT_DIR/$seq
echo "QA output created by $seq"

here=`pwd`
tmp=/tmp/$$
status=1	# failure is the default!
trap "_cleanup; exit \$status" 0 1 2 3 15

_cleanup()
{
	cd /
	rm -f $tmp.*
}

# get standard environment, filters and checks
. ./common/rc
. ./common/filter
. ./common/encrypt

# remove previous $seqres.full before test
rm -f $seqres.full

# real QA test starts here
_supported_fs generic
_require_scratch_encryption -v 2
_require_get_encryption_nonce_support
_require_command "$XZ_PROG" xz

_scratch_mkfs_encrypted &>> $seqres.full
_scratch_mount

echo -e "\n# Adding encryption keys"
_add_enckey $SCRATCH_MNT "$TEST_RAW_KEY"
_add_enckey $SCRATCH_MNT "$TEST_RAW_KEY" -d $TEST_KEY_DESCRIPTOR

# Create a bunch of encrypted files and directories -- enough for the uniqueness
# and randomness tests to be meaningful, but not so many that this test takes a
# long time.  Test using both v1 and v2 encryption policies, and for each of
# those test the case of an encryption policy that is assigned to an empty
# directory as well as the case of a file created in an encrypted directory.
echo -e "\n# Creating encrypted files and directories"
inodes=()
for i in {1..50}; do
	dir=$SCRATCH_MNT/v1_policy_dir_$i
	mkdir $dir
	inodes+=("$(stat -c %i $dir)")
	_set_encpolicy $dir $TEST_KEY_DESCRIPTOR

	dir=$SCRATCH_MNT/v2_policy_dir_$i
	mkdir $dir
	inodes+=("$(stat -c %i $dir)")
	_set_encpolicy $dir $TEST_KEY_IDENTIFIER
done
for i in {1..50}; do
	file=$SCRATCH_MNT/v1_policy_dir_1/$i
	touch $file
	inodes+=("$(stat -c %i $file)")

	file=$SCRATCH_MNT/v2_policy_dir_1/$i
	touch $file
	inodes+=("$(stat -c %i $file)")
done
_scratch_unmount

# Build files that contain all the nonces.  nonces_hex contains them in hex, one
# per line.  nonces_bin contains them in binary, all concatenated.
echo -e "\n# Getting encryption nonces from inodes"
echo -n > $tmp.nonces_hex
echo -n > $tmp.nonces_bin
for inode in "${inodes[@]}"; do
	nonce=$(_get_encryption_nonce $SCRATCH_DEV $inode)
	if (( ${#nonce} != 32 )) || [ -n "$(echo "$nonce" | tr -d 0-9a-fA-F)" ]
	then
		_fail "Expected nonce to be 16 bytes (32 hex characters), but got \"$nonce\""
	fi
	echo $nonce >> $tmp.nonces_hex
	echo -ne "$(echo $nonce | sed 's/[0-9a-fA-F]\{2\}/\\x\0/g')" \
		>> $tmp.nonces_bin
done

# Verify the uniqueness and randomness of the nonces.  In theory randomness
# implies uniqueness here, but it's easy enough to explicitly test for both.

echo -e "\n# Verifying uniqueness of nonces"
echo "Listing non-unique nonces:"
sort < $tmp.nonces_hex | uniq -d

echo -e "\n# Verifying randomness of nonces"
uncompressed_size=$(stat -c %s $tmp.nonces_bin)
echo "Uncompressed size is $uncompressed_size bytes"
compressed_size=$($XZ_PROG -c < $tmp.nonces_bin | wc -c)
echo "Compressed size is $compressed_size bytes" >> $seqres.full
# The xz format has 60 bytes of overhead.  Go a bit lower to avoid flakiness.
if (( compressed_size >= uncompressed_size + 55 )); then
	echo "Nonces are incompressible, as expected"
else
	_fail "Nonces are compressible (non-random); compressed $uncompressed_size => $compressed_size bytes!"
fi

# success, all done
status=0
exit