Allow --reduce-device-size and --device-size in encrypt action.

Fixes: #822

man/common_options.adoc

@@ -124,6 +124,13 @@ ifdef::ACTION_REENCRYPT[]
 It means that only specified area (from the start of the device
 to the specified size) will be reencrypted.
 +
+*LUKS2*:
+When used together with --reduce-device-size, only the initial _size_ value
+(--device-size parameter) of data is shifted backwards while being encrypted.
++
+*NOTE*:
+The sum of --device-size and --reduce-device-size values must not exceed real device size.
++
 *WARNING:* This is destructive operation. Data beyond --device-size limit may
 be lost after operation gets finished.
 endif::[]
@@ -993,11 +1000,18 @@ unrecoverable.
 +
 *LUKS2*:
 Initialize LUKS2 reencryption with data device size reduction
-(currently only encryption mode is supported).
+(currently only encryption mode is supported). The last _size_ sectors
+on the original plaintext device is used for temporarily storing original
+first data segment. The former first data segment is replaced with LUKS2
+header (half the _size_ value) and plaintext data are shifted backwards (
+again half the _size_ value) while being encrypted.
 +
 Recommended minimal size is twice the default LUKS2 header size
 (--reduce-device-size 32M) for encryption mode.
 +
+*NOTE*:
+The sum of --device-size and --reduce-device-size values must not exceed real device size.
++
 *LUKS1*:
 Enlarge data offset to specified value by shrinking device size.
 +

man/cryptsetup-reencrypt.8.adoc

@@ -142,6 +142,13 @@ is unused (e.g.: does not contain filesystem data):
 
 *cryptsetup reencrypt --encrypt --type luks2 --reduce-device-size 32m /dev/plaintext_device*
 
+Encrypt LUKS2 device (in-place). Only the initial 1 GiB of original
+_/dev/plaintext_ data is encrypted while being shifted backwards.
+Make sure last 32 MiB (tail) on the data device is unused (e.g.: does
+not contain any data):
+
+*cryptsetup reencrypt --encrypt --type luks2 --device-size 1g --reduce-device-size 32m /dev/plaintext_device*
+
 Encrypt LUKS2 device (in-place) with detached header put in a file:
 
 *cryptsetup reencrypt --encrypt --type luks2 --header my_luks2_header /dev/plaintext_device*

src/cryptsetup.c

@@ -3377,9 +3377,6 @@ static const char *verify_resize(void)
 
 static const char *verify_reencrypt(void)
 {
-	if (ARG_SET(OPT_REDUCE_DEVICE_SIZE_ID) && ARG_SET(OPT_DEVICE_SIZE_ID))
-		return _("Options --reduce-device-size and --device-size cannot be combined.");
-
 	if (isLUKS1(luksType(device_type)) && ARG_SET(OPT_ACTIVE_NAME_ID))
 		return _("Option --active-name can be set only for LUKS2 device.");
 

src/utils_reencrypt.c

@@ -680,13 +680,15 @@ static int encrypt_luks2_init(struct crypt_device **cd, const char *data_device,
 		}
 	}
 
+	/* The --reduce-device-size has to be at least twice the size of first moved segment (LUKS2
+	 * data offset) */
 	if (!ARG_SET(OPT_HEADER_ID) && ARG_UINT64(OPT_OFFSET_ID) &&
 	    data_shift && (ARG_UINT64(OPT_OFFSET_ID) > (uint64_t)(imaxabs(data_shift) / (2 * SECTOR_SIZE)))) {
 		log_err(_("Requested data offset must be less than or equal to half of --reduce-device-size parameter."));
 		return -EINVAL;
 	}
 
-	/* TODO: ask user to confirm. It's useless to do data device reduction and than use smaller value */
+	/* It's useless to do data device reduction and than use smaller value */
 	if (!ARG_SET(OPT_HEADER_ID) && ARG_UINT64(OPT_OFFSET_ID) &&
 	    data_shift && (ARG_UINT64(OPT_OFFSET_ID) < (uint64_t)(imaxabs(data_shift) / (2 * SECTOR_SIZE)))) {
 		data_shift = -(ARG_UINT64(OPT_OFFSET_ID) * 2 * SECTOR_SIZE);

tests/compat-args-test

@@ -285,7 +285,6 @@ exp_fail reencrypt DEV --reduce-device-size 2G # max 1g
 exp_fail reencrypt DEV --reduce-device-size $((64*1024*1024+1))
 exp_fail reencrypt DEV --reduce-device-size -64m
 exp_pass reencrypt DEV --reduce-device-size 64m
-exp_fail reencrypt DEV --reduce-device-size 64m --device-size 100g
 # bugs
 # exp_fail open DEV --decrypt --header H
 # exp_fail open DEV --encrypt

tests/luks2-reencryption-test

@@ -297,6 +297,28 @@ resize_file() # $1 dev, $2 shrink bytes
 	losetup -c $LOOPDEV
 }
 
+error_io() { # $1 dmdev, $2 data dev, $3 offset, $4 size
+	local _dev_size=$(blockdev --getsz /dev/mapper/$1)
+	local _offset=$(($3+$4))
+	local _size=$((_dev_size-_offset))
+	local _table=
+	dmsetup create $1-err --table "0 $_dev_size error" || fail
+
+	if [ $3 -ne 0 ]; then
+		_table="0 $3 linear $2 0\n"
+	fi
+
+	_table=$_table"$3 $4 error"
+
+	if [ $_size -ne 0 ]; then
+		_table="$_table\n$_offset $_size linear $2 $_offset"
+	fi
+
+	echo -e "$_table" | dmsetup load $1 || fail
+	dmsetup resume $1 || fail
+	blockdev --setra 0 /dev/mapper/$1
+}
+
 error_writes() { # $1 dmdev, $2 data dev, $3 offset, $4 size
 	local _dev_size=$(blockdev --getsz /dev/mapper/$1)
 	local _offset=$(($3+$4))
@@ -1206,6 +1228,50 @@ echo $PWD1 | $CRYPTSETUP reencrypt $DEV --encrypt --reduce-device-size 64M --ini
 check_hash_dev_head /dev/mapper/$DEV_NAME 2048 $HASH2
 echo $PWD1 | $CRYPTSETUP reencrypt $DEV -q || fail
 check_hash_dev_head /dev/mapper/$DEV_NAME 2048 $HASH2
+$CRYPTSETUP close $DEV_NAME || fail
+
+# encryption with both data shift and reduced data size
+prepare_linear_dev 65
+
+# --reduce-device-size + --device-size (1MiB+512B) is larger than real device size
+echo $PWD1 | $CRYPTSETUP reencrypt $DEV --encrypt --init-only --device-size 2049s --reduce-device-size 64M -q $FAST_PBKDF_ARGON >/dev/null 2>&1 && fail
+$CRYPTSETUP isLuks --type luks2 $DEV && fail
+# no changes in data device
+check_hash_dev_head $DEV 2048 $HASH2
+
+# --reduce-device-size (1MiB+8KiB) + --device-size (64MiB - (8KiB-512B)) is larger than real device size
+echo $PWD1 | $CRYPTSETUP reencrypt $DEV --encrypt --init-only --device-size 131057s --reduce-device-size 2064s -q $FAST_PBKDF_ARGON >/dev/null 2>&1 && fail
+$CRYPTSETUP isLuks --type luks2 $DEV && fail
+# no changes in data device
+check_hash_dev_head $DEV 2048 $HASH2
+
+echo $PWD1 | $CRYPTSETUP reencrypt $DEV --encrypt --device-size 1M --reduce-device-size 32M -q $FAST_PBKDF_ARGON || fail
+check_hash_head $PWD1 2048 $HASH2
+
+# test limit values (--device-size + --reduce-device-size = real device size)
+wipe_dev_head $DEV 43
+echo $PWD1 | $CRYPTSETUP reencrypt $DEV --encrypt --device-size 43M --reduce-device-size 22M -q $FAST_PBKDF_ARGON || fail
+check_hash_head $PWD1 88064 $HASH6
+
+wipe_dev_head $DEV 1
+# check reencryption code does not touch data in-between --device-size and --reduce-device-size
+# data device: [ reduce-device-size / 2 ] [ device-size ] [ error minefield ] [ reduce-device-size / 2]
+ERROFFSET=34816
+ERRLENGTH=65536
+error_io $OVRDEV $OLD_DEV $ERROFFSET $ERRLENGTH
+echo $PWD1 | $CRYPTSETUP reencrypt $DEV --encrypt --device-size 1M --reduce-device-size 32M -q $FAST_PBKDF_ARGON  || fail
+fix_writes $OVRDEV $OLD_DEV
+check_hash_head $PWD1 2048 $HASH2
+
+wipe_dev_head $DEV 43
+
+ERROFFSET=104448
+ERRLENGTH=12288
+# data device: [ reduce-device-size / 2 ] [ device-size ] [ error minefield ] [ reduce-device-size / 2]
+error_io $OVRDEV $OLD_DEV $ERROFFSET $ERRLENGTH
+echo $PWD1 | $CRYPTSETUP reencrypt $DEV --encrypt --device-size 43M --reduce-device-size 16M -q $FAST_PBKDF_ARGON || fail
+fix_writes $OVRDEV $OLD_DEV
+check_hash_head $PWD1 88064 $HASH6
 
 echo "[3] Encryption with detached header"
 preparebig 256