##/bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (c) 2016 Google, Inc.  All Rights Reserved.
#
# Functions for setting up and testing file encryption

#
# _require_scratch_encryption [-c CONTENTS_MODE] [-n FILENAMES_MODE]
#
# Require encryption support on the scratch device.
#
# This checks for support for the default type of encryption policy (AES-256-XTS
# and AES-256-CTS).  Options can be specified to also require support for a
# different type of encryption policy.
#
_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 ! _try_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 _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

	# If required, check for support for the specific type of encryption
	# policy required by the test.
	if [ $# -ne 0 ]; then
		_require_encryption_policy_support $SCRATCH_MNT "$@"
	fi

	_scratch_unmount
}

_require_encryption_policy_support()
{
	local mnt=$1
	local dir=$mnt/tmpdir
	local set_encpolicy_args=""
	local c

	OPTIND=2
	while getopts "c:n:" c; do
		case $c in
		c|n)
			set_encpolicy_args+=" -$c $OPTARG"
			;;
		*)
			_fail "Unrecognized option '$c'"
			;;
		esac
	done
	set_encpolicy_args=${set_encpolicy_args# }

	echo "Checking whether kernel supports encryption policy: $set_encpolicy_args" \
		>> $seqres.full

	mkdir $dir
	_require_command "$KEYCTL_PROG" keyctl
	_new_session_keyring
	local keydesc=$(_generate_encryption_key)
	if _set_encpolicy $dir $keydesc $set_encpolicy_args \
		2>&1 >>$seqres.full | egrep -q 'Invalid argument'; then
		_notrun "kernel does not support encryption policy: '$set_encpolicy_args'"
	fi
	# fscrypt allows setting policies with modes it knows about, even
	# without kernel crypto API support.  E.g. a policy using Adiantum
	# encryption can be set on a kernel without CONFIG_CRYPTO_ADIANTUM.
	# But actually trying to use such an encrypted directory will fail.
	if ! touch $dir/file; then
		_notrun "encryption policy '$set_encpolicy_args' is unusable; probably missing kernel crypto API support"
	fi
	$KEYCTL_PROG clear @s
	rm -r $dir
}

_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
}

_scratch_mkfs_sized_encrypted()
{
	case $FSTYP in
	ext4|f2fs)
		MKFS_OPTIONS="$MKFS_OPTIONS -O encrypt" _scratch_mkfs_sized $*
		;;
	*)
		_notrun "Filesystem $FSTYP not supported in _scratch_mkfs_sized_encrypted"
		;;
	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
}

# Set an encryption policy on the specified directory.
_set_encpolicy()
{
	local dir=$1
	shift

	$XFS_IO_PROG -c "set_encpolicy $*" "$dir"
}

_user_do_set_encpolicy()
{
	local dir=$1
	shift

	_user_do "$XFS_IO_PROG -c \"set_encpolicy $*\" \"$dir\""
}

# Display the specified file or directory's encryption policy.
_get_encpolicy()
{
	local file=$1
	shift

	$XFS_IO_PROG -c "get_encpolicy $*" "$file"
}