apfstests/common/encrypt

#-----------------------------------------------------------------------
#
# Common functions for testing filesystem-level encryption
#
#-----------------------------------------------------------------------
# Copyright (c) 2016 Google, Inc.  All Rights Reserved.
#
# Author: Eric Biggers <ebiggers@google.com>
#
# 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.
#
# This program is distributed in the hope that it would 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, write the Free Software Foundation,
# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
#-----------------------------------------------------------------------

_require_scratch_encryption()
{
	_require_scratch

	_require_xfs_io_command "set_encpolicy"

	# The 'test_dummy_encryption' mount option interferes with trying to use
	# encryption for real, even if we are just trying to get/set policies
	# and never put any keys in the keyring.  So skip the real encryption
	# tests if the 'test_dummy_encryption' mount option was specified.
	_exclude_scratch_mount_option "test_dummy_encryption"

	# Make a filesystem on the scratch device with the encryption feature
	# enabled.  If this fails then probably the userspace tools (e.g.
	# e2fsprogs or f2fs-tools) are too old to understand encryption.
	if ! _scratch_mkfs_encrypted &>>$seqres.full; then
		_notrun "$FSTYP userspace tools do not support encryption"
	fi

	# Try to mount the filesystem.  If this fails then either the kernel
	# isn't aware of encryption, or the mkfs options were not compatible
	# with encryption (e.g. ext4 with block size != PAGE_SIZE).
	if ! _scratch_mount &>>$seqres.full; then
		_notrun "kernel is unaware of $FSTYP encryption feature," \
			"or mkfs options are not compatible with encryption"
	fi

	# The kernel may be aware of encryption without supporting it.  For
	# example, for ext4 this is the case with kernels configured with
	# CONFIG_EXT4_FS_ENCRYPTION=n.  Detect support for encryption by trying
	# to set an encryption policy.  (For ext4 we could instead check for the
	# presence of /sys/fs/ext4/features/encryption, but this is broken on
	# some older kernels and is ext4-specific anyway.)
	mkdir $SCRATCH_MNT/tmpdir
	if $XFS_IO_PROG -c set_encpolicy $SCRATCH_MNT/tmpdir \
		2>&1 >>$seqres.full | \
		egrep -q 'Inappropriate ioctl for device|Operation not supported'
	then
		_notrun "kernel does not support $FSTYP encryption"
	fi
	rmdir $SCRATCH_MNT/tmpdir
	_scratch_unmount
}

_scratch_mkfs_encrypted()
{
	case $FSTYP in
	ext4|f2fs)
		_scratch_mkfs -O encrypt
		;;
	ubifs)
		# erase the UBI volume; reformated automatically on next mount
		$UBIUPDATEVOL_PROG ${SCRATCH_DEV} -t
		;;
	*)
		_notrun "No encryption support for $FSTYP"
		;;
	esac
}

# Give the invoking shell a new session keyring.  This makes any keys we add to
# the session keyring scoped to the lifetime of the test script.
_new_session_keyring()
{
	$KEYCTL_PROG new_session >>$seqres.full
}

# Generate a key descriptor (16 character hex string)
_generate_key_descriptor()
{
	local keydesc=""
	local i
	for ((i = 0; i < 8; i++)); do
		keydesc="${keydesc}$(printf "%02x" $(( $RANDOM % 256 )))"
	done
	echo $keydesc
}

# Generate a raw encryption key, but don't add it to the keyring yet.
_generate_raw_encryption_key()
{
	local raw=""
	local i
	for ((i = 0; i < 64; i++)); do
		raw="${raw}\\x$(printf "%02x" $(( $RANDOM % 256 )))"
	done
	echo $raw
}

# Add the specified raw encryption key to the session keyring, using the
# specified key descriptor.
_add_encryption_key()
{
	local keydesc=$1
	local raw=$2

	#
	# Add the key to the session keyring.  The required structure is:
	#
	#	#define FS_MAX_KEY_SIZE 64
	#	struct fscrypt_key {
	#		u32 mode;
	#		u8 raw[FS_MAX_KEY_SIZE];
	#		u32 size;
	#	} __packed;
	#
	# The kernel ignores 'mode' but requires that 'size' be 64.
	#
	# Keys are named $FSTYP:KEYDESC where KEYDESC is the 16-character key
	# descriptor hex string.  Newer kernels (ext4 4.8 and later, f2fs 4.6
	# and later) also allow the common key prefix "fscrypt:" in addition to
	# their filesystem-specific key prefix ("ext4:", "f2fs:").  It would be
	# nice to use the common key prefix, but for now use the filesystem-
	# specific prefix to make it possible to test older kernels...
	#
	local big_endian=$(echo -ne '\x11' | od -tx2 | head -1 | \
			   cut -f2 -d' ' | cut -c1 )
	if (( big_endian )); then
		local mode='\x00\x00\x00\x00'
		local size='\x00\x00\x00\x40'
	else
		local mode='\x00\x00\x00\x00'
		local size='\x40\x00\x00\x00'
	fi
	echo -n -e "${mode}${raw}${size}" |
		$KEYCTL_PROG padd logon $FSTYP:$keydesc @s >>$seqres.full
}

#
# Generate a random encryption key, add it to the session keyring, and print out
# the resulting key descriptor (example: "8bf798e1a494e1ec").  Requires the
# keyctl program.  It's assumed the caller has already set up a test-scoped
# session keyring using _new_session_keyring.
#
_generate_encryption_key()
{
	local keydesc=$(_generate_key_descriptor)
	local raw=$(_generate_raw_encryption_key)

	_add_encryption_key $keydesc $raw

	echo $keydesc
}

# Unlink an encryption key from the session keyring, given its key descriptor.
_unlink_encryption_key()
{
	local keydesc=$1
	local keyid=$($KEYCTL_PROG search @s logon $FSTYP:$keydesc)
	$KEYCTL_PROG unlink $keyid >>$seqres.full
}

# Revoke an encryption key from the keyring, given its key descriptor.
_revoke_encryption_key()
{
	local keydesc=$1
	local keyid=$($KEYCTL_PROG search @s logon $FSTYP:$keydesc)
	$KEYCTL_PROG revoke $keyid >>$seqres.full
}