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Eric Biggers
b09ba3318e
Test that encryption nonces are unique and random, where randomness is approximated as "incompressible by the xz program". This gets indirectly tested by generic/399, but there are some gaps. It's good to test for this directly too. This test runs and passes on ext4 and f2fs. It doesn't currently run on ubifs because _get_encryption_nonce() isn't implemented for ubifs yet. (At some point I'll probably switch _get_encryption_nonce() to use FS_IOC_GET_ENCRYPTION_NONCE, which was added in Linux 5.7. But for now I'd like to keep the tests using it runnable on older kernels too.) Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Eryu Guan <guaneryu@gmail.com>
119 lines
3.7 KiB
Bash
Executable File
119 lines
3.7 KiB
Bash
Executable File
#! /bin/bash
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# SPDX-License-Identifier: GPL-2.0
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# Copyright 2020 Google LLC
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#
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# FS QA Test No. 613
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#
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# Test that encryption nonces are unique and random, where randomness is
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# approximated as "incompressible by the xz program".
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#
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# An encryption nonce is the 16-byte value that the filesystem generates for
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# each encrypted file. These nonces must be unique in order to cause different
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# files to be encrypted differently, which is an important security property.
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# In practice, they need to be random to achieve that; and it's easy enough to
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# test for both uniqueness and randomness, so we test for both.
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#
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seq=`basename $0`
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seqres=$RESULT_DIR/$seq
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echo "QA output created by $seq"
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here=`pwd`
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tmp=/tmp/$$
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status=1 # failure is the default!
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trap "_cleanup; exit \$status" 0 1 2 3 15
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_cleanup()
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{
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cd /
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rm -f $tmp.*
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}
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# get standard environment, filters and checks
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. ./common/rc
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. ./common/filter
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. ./common/encrypt
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# remove previous $seqres.full before test
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rm -f $seqres.full
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# real QA test starts here
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_supported_fs generic
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_require_scratch_encryption -v 2
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_require_get_encryption_nonce_support
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_require_command "$XZ_PROG" xz
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_scratch_mkfs_encrypted &>> $seqres.full
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_scratch_mount
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echo -e "\n# Adding encryption keys"
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_add_enckey $SCRATCH_MNT "$TEST_RAW_KEY"
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_add_enckey $SCRATCH_MNT "$TEST_RAW_KEY" -d $TEST_KEY_DESCRIPTOR
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# Create a bunch of encrypted files and directories -- enough for the uniqueness
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# and randomness tests to be meaningful, but not so many that this test takes a
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# long time. Test using both v1 and v2 encryption policies, and for each of
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# those test the case of an encryption policy that is assigned to an empty
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# directory as well as the case of a file created in an encrypted directory.
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echo -e "\n# Creating encrypted files and directories"
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inodes=()
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for i in {1..50}; do
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dir=$SCRATCH_MNT/v1_policy_dir_$i
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mkdir $dir
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inodes+=("$(stat -c %i $dir)")
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_set_encpolicy $dir $TEST_KEY_DESCRIPTOR
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dir=$SCRATCH_MNT/v2_policy_dir_$i
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mkdir $dir
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inodes+=("$(stat -c %i $dir)")
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_set_encpolicy $dir $TEST_KEY_IDENTIFIER
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done
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for i in {1..50}; do
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file=$SCRATCH_MNT/v1_policy_dir_1/$i
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touch $file
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inodes+=("$(stat -c %i $file)")
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file=$SCRATCH_MNT/v2_policy_dir_1/$i
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touch $file
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inodes+=("$(stat -c %i $file)")
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done
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_scratch_unmount
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# Build files that contain all the nonces. nonces_hex contains them in hex, one
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# per line. nonces_bin contains them in binary, all concatenated.
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echo -e "\n# Getting encryption nonces from inodes"
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echo -n > $tmp.nonces_hex
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echo -n > $tmp.nonces_bin
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for inode in "${inodes[@]}"; do
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nonce=$(_get_encryption_nonce $SCRATCH_DEV $inode)
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if (( ${#nonce} != 32 )) || [ -n "$(echo "$nonce" | tr -d 0-9a-fA-F)" ]
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then
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_fail "Expected nonce to be 16 bytes (32 hex characters), but got \"$nonce\""
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fi
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echo $nonce >> $tmp.nonces_hex
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echo -ne "$(echo $nonce | sed 's/[0-9a-fA-F]\{2\}/\\x\0/g')" \
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>> $tmp.nonces_bin
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done
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# Verify the uniqueness and randomness of the nonces. In theory randomness
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# implies uniqueness here, but it's easy enough to explicitly test for both.
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echo -e "\n# Verifying uniqueness of nonces"
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echo "Listing non-unique nonces:"
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sort < $tmp.nonces_hex | uniq -d
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echo -e "\n# Verifying randomness of nonces"
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uncompressed_size=$(stat -c %s $tmp.nonces_bin)
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echo "Uncompressed size is $uncompressed_size bytes"
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compressed_size=$($XZ_PROG -c < $tmp.nonces_bin | wc -c)
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echo "Compressed size is $compressed_size bytes" >> $seqres.full
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# The xz format has 60 bytes of overhead. Go a bit lower to avoid flakiness.
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if (( compressed_size >= uncompressed_size + 55 )); then
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echo "Nonces are incompressible, as expected"
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else
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_fail "Nonces are compressible (non-random); compressed $uncompressed_size => $compressed_size bytes!"
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fi
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# success, all done
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status=0
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exit
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