Adding upstream version 2:2.3.7.upstream/2%2.3.7upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 806 insertions, 0 deletions

diff --git a/lib/luks2/luks2_disk_metadata.c b/lib/luks2/luks2_disk_metadata.c
new file mode 100644
index 0000000..3f6b3ae
--- /dev/null
+++ b/lib/luks2/luks2_disk_metadata.c
@@ -0,0 +1,806 @@
+/*
+ * LUKS - Linux Unified Key Setup v2
+ *
+ * Copyright (C) 2015-2021 Red Hat, Inc. All rights reserved.
+ * Copyright (C) 2015-2021 Milan Broz
+ *
+ * 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; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will 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 to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <assert.h>
+
+#include "luks2_internal.h"
+
+/*
+ * Helper functions
+ */
+static json_object *parse_json_len(struct crypt_device *cd, const char *json_area,
+			    uint64_t max_length, int *json_len)
+{
+	json_object *jobj;
+	struct json_tokener *jtok;
+
+	 /* INT32_MAX is internal (json-c) json_tokener_parse_ex() limit */
+	if (!json_area || max_length > INT32_MAX)
+		return NULL;
+
+	jtok = json_tokener_new();
+	if (!jtok) {
+		log_dbg(cd, "ERROR: Failed to init json tokener");
+		return NULL;
+	}
+
+	jobj = json_tokener_parse_ex(jtok, json_area, max_length);
+	if (!jobj)
+		log_dbg(cd, "ERROR: Failed to parse json data (%d): %s",
+			json_tokener_get_error(jtok),
+			json_tokener_error_desc(json_tokener_get_error(jtok)));
+	else
+		*json_len = jtok->char_offset;
+
+	json_tokener_free(jtok);
+
+	return jobj;
+}
+
+static void log_dbg_checksum(struct crypt_device *cd,
+			     const uint8_t *csum, const char *csum_alg, const char *info)
+{
+	char csum_txt[2*LUKS2_CHECKSUM_L+1];
+	int i;
+
+	for (i = 0; i < crypt_hash_size(csum_alg); i++)
+		snprintf(&csum_txt[i*2], 3, "%02hhx", (const char)csum[i]);
+	csum_txt[i*2+1] = '\0'; /* Just to be safe, sprintf should write \0 there. */
+
+	log_dbg(cd, "Checksum:%s (%s)", &csum_txt[0], info);
+}
+
+/*
+ * Calculate hash (checksum) of |LUKS2_bin|LUKS2_JSON_area| from in-memory structs.
+ * LUKS2 on-disk header contains uniques salt both for primary and secondary header.
+ * Checksum is always calculated with zeroed checksum field in binary header.
+ */
+static int hdr_checksum_calculate(const char *alg, struct luks2_hdr_disk *hdr_disk,
+				  const char *json_area, size_t json_len)
+{
+	struct crypt_hash *hd = NULL;
+	int hash_size, r;
+
+	hash_size = crypt_hash_size(alg);
+	if (hash_size <= 0 || crypt_hash_init(&hd, alg))
+		return -EINVAL;
+
+	/* Binary header, csum zeroed. */
+	r = crypt_hash_write(hd, (char*)hdr_disk, LUKS2_HDR_BIN_LEN);
+
+	/* JSON area (including unused space) */
+	if (!r)
+		r = crypt_hash_write(hd, json_area, json_len);
+
+	if (!r)
+		r = crypt_hash_final(hd, (char*)hdr_disk->csum, (size_t)hash_size);
+
+	crypt_hash_destroy(hd);
+	return r;
+}
+
+/*
+ * Compare hash (checksum) of on-disk and in-memory header.
+ */
+static int hdr_checksum_check(struct crypt_device *cd,
+			      const char *alg, struct luks2_hdr_disk *hdr_disk,
+			      const char *json_area, size_t json_len)
+{
+	struct luks2_hdr_disk hdr_tmp;
+	int hash_size, r;
+
+	hash_size = crypt_hash_size(alg);
+	if (hash_size <= 0)
+		return -EINVAL;
+
+	/* Copy header and zero checksum. */
+	memcpy(&hdr_tmp, hdr_disk, LUKS2_HDR_BIN_LEN);
+	memset(&hdr_tmp.csum, 0, sizeof(hdr_tmp.csum));
+
+	r = hdr_checksum_calculate(alg, &hdr_tmp, json_area, json_len);
+	if (r < 0)
+		return r;
+
+	log_dbg_checksum(cd, hdr_disk->csum, alg, "on-disk");
+	log_dbg_checksum(cd, hdr_tmp.csum, alg, "in-memory");
+
+	if (memcmp(hdr_tmp.csum, hdr_disk->csum, (size_t)hash_size))
+		return -EINVAL;
+
+	return 0;
+}
+
+/*
+ * Convert header from on-disk format to in-memory struct
+ */
+static void hdr_from_disk(struct luks2_hdr_disk *hdr_disk1,
+			  struct luks2_hdr_disk *hdr_disk2,
+			  struct luks2_hdr *hdr,
+			  int secondary)
+{
+	hdr->version  = be16_to_cpu(hdr_disk1->version);
+	hdr->hdr_size = be64_to_cpu(hdr_disk1->hdr_size);
+	hdr->seqid    = be64_to_cpu(hdr_disk1->seqid);
+
+	memcpy(hdr->label, hdr_disk1->label, LUKS2_LABEL_L);
+	hdr->label[LUKS2_LABEL_L - 1] = '\0';
+	memcpy(hdr->subsystem, hdr_disk1->subsystem, LUKS2_LABEL_L);
+	hdr->subsystem[LUKS2_LABEL_L - 1] = '\0';
+	memcpy(hdr->checksum_alg, hdr_disk1->checksum_alg, LUKS2_CHECKSUM_ALG_L);
+	hdr->checksum_alg[LUKS2_CHECKSUM_ALG_L - 1] = '\0';
+	memcpy(hdr->uuid, hdr_disk1->uuid, LUKS2_UUID_L);
+	hdr->uuid[LUKS2_UUID_L - 1] = '\0';
+
+	if (secondary) {
+		memcpy(hdr->salt1, hdr_disk2->salt, LUKS2_SALT_L);
+		memcpy(hdr->salt2, hdr_disk1->salt, LUKS2_SALT_L);
+	} else {
+		memcpy(hdr->salt1, hdr_disk1->salt, LUKS2_SALT_L);
+		memcpy(hdr->salt2, hdr_disk2->salt, LUKS2_SALT_L);
+	}
+}
+
+/*
+ * Convert header from in-memory struct to on-disk format
+ */
+static void hdr_to_disk(struct luks2_hdr *hdr,
+			struct luks2_hdr_disk *hdr_disk,
+			int secondary, uint64_t offset)
+{
+	assert(((char*)&(hdr_disk->_padding4096) - (char*)&(hdr_disk->magic)) == 512);
+
+	memset(hdr_disk, 0, LUKS2_HDR_BIN_LEN);
+
+	memcpy(&hdr_disk->magic, secondary ? LUKS2_MAGIC_2ND : LUKS2_MAGIC_1ST, LUKS2_MAGIC_L);
+	hdr_disk->version     = cpu_to_be16(hdr->version);
+	hdr_disk->hdr_size    = cpu_to_be64(hdr->hdr_size);
+	hdr_disk->hdr_offset  = cpu_to_be64(offset);
+	hdr_disk->seqid       = cpu_to_be64(hdr->seqid);
+
+	memcpy(hdr_disk->label, hdr->label, MIN(strlen(hdr->label), LUKS2_LABEL_L));
+	hdr_disk->label[LUKS2_LABEL_L - 1] = '\0';
+	memcpy(hdr_disk->subsystem, hdr->subsystem, MIN(strlen(hdr->subsystem), LUKS2_LABEL_L));
+	hdr_disk->subsystem[LUKS2_LABEL_L - 1] = '\0';
+	memcpy(hdr_disk->checksum_alg, hdr->checksum_alg, MIN(strlen(hdr->checksum_alg), LUKS2_CHECKSUM_ALG_L));
+	hdr_disk->checksum_alg[LUKS2_CHECKSUM_ALG_L - 1] = '\0';
+	memcpy(hdr_disk->uuid, hdr->uuid, MIN(strlen(hdr->uuid), LUKS2_UUID_L));
+	hdr_disk->uuid[LUKS2_UUID_L - 1] = '\0';
+
+	memcpy(hdr_disk->salt, secondary ? hdr->salt2 : hdr->salt1, LUKS2_SALT_L);
+}
+
+/*
+ * Sanity checks before checksum is validated
+ */
+static int hdr_disk_sanity_check_pre(struct crypt_device *cd,
+				     struct luks2_hdr_disk *hdr,
+				     size_t *hdr_json_size, int secondary,
+				     uint64_t offset)
+{
+	if (memcmp(hdr->magic, secondary ? LUKS2_MAGIC_2ND : LUKS2_MAGIC_1ST, LUKS2_MAGIC_L))
+		return -EINVAL;
+
+	if (be16_to_cpu(hdr->version) != 2) {
+		log_dbg(cd, "Unsupported LUKS2 header version %u.", be16_to_cpu(hdr->version));
+		return -EINVAL;
+	}
+
+	if (offset != be64_to_cpu(hdr->hdr_offset)) {
+		log_dbg(cd, "LUKS2 offset 0x%04x on device differs to expected offset 0x%04x.",
+			(unsigned)be64_to_cpu(hdr->hdr_offset), (unsigned)offset);
+		return -EINVAL;
+	}
+
+	if (secondary && (offset != be64_to_cpu(hdr->hdr_size))) {
+		log_dbg(cd, "LUKS2 offset 0x%04x in secondary header does not match size 0x%04x.",
+			(unsigned)offset, (unsigned)be64_to_cpu(hdr->hdr_size));
+		return -EINVAL;
+	}
+
+	/* FIXME: sanity check checksum alg. */
+
+	log_dbg(cd, "LUKS2 header version %u of size %u bytes, checksum %s.",
+		(unsigned)be16_to_cpu(hdr->version), (unsigned)be64_to_cpu(hdr->hdr_size),
+		hdr->checksum_alg);
+
+	*hdr_json_size = be64_to_cpu(hdr->hdr_size) - LUKS2_HDR_BIN_LEN;
+	return 0;
+}
+
+/*
+ * Read LUKS2 header from disk at specific offset.
+ */
+static int hdr_read_disk(struct crypt_device *cd,
+			 struct device *device, struct luks2_hdr_disk *hdr_disk,
+			 char **json_area, uint64_t offset, int secondary)
+{
+	size_t hdr_json_size = 0;
+	int devfd, r;
+
+	log_dbg(cd, "Trying to read %s LUKS2 header at offset 0x%" PRIx64 ".",
+		secondary ? "secondary" : "primary", offset);
+
+	devfd = device_open_locked(cd, device, O_RDONLY);
+	if (devfd < 0)
+		return devfd == -1 ? -EIO : devfd;
+
+	/*
+	 * Read binary header and run sanity check before reading
+	 * JSON area and validating checksum.
+	 */
+	if (read_lseek_blockwise(devfd, device_block_size(cd, device),
+				 device_alignment(device), hdr_disk,
+				 LUKS2_HDR_BIN_LEN, offset) != LUKS2_HDR_BIN_LEN) {
+		return -EIO;
+	}
+
+	r = hdr_disk_sanity_check_pre(cd, hdr_disk, &hdr_json_size, secondary, offset);
+	if (r < 0) {
+		return r;
+	}
+
+	/*
+	 * Allocate and read JSON area. Always the whole area must be read.
+	 */
+	*json_area = malloc(hdr_json_size);
+	if (!*json_area) {
+		return -ENOMEM;
+	}
+
+	if (read_lseek_blockwise(devfd, device_block_size(cd, device),
+				 device_alignment(device), *json_area, hdr_json_size,
+				 offset + LUKS2_HDR_BIN_LEN) != (ssize_t)hdr_json_size) {
+		free(*json_area);
+		*json_area = NULL;
+		return -EIO;
+	}
+
+	/*
+	 * Calculate and validate checksum and zero it afterwards.
+	 */
+	if (hdr_checksum_check(cd, hdr_disk->checksum_alg, hdr_disk,
+				*json_area, hdr_json_size)) {
+		log_dbg(cd, "LUKS2 header checksum error (offset %" PRIu64 ").", offset);
+		r = -EINVAL;
+	}
+	memset(hdr_disk->csum, 0, LUKS2_CHECKSUM_L);
+
+	return r;
+}
+
+/*
+ * Write LUKS2 header to disk at specific offset.
+ */
+static int hdr_write_disk(struct crypt_device *cd,
+			  struct device *device, struct luks2_hdr *hdr,
+			  const char *json_area, int secondary)
+{
+	struct luks2_hdr_disk hdr_disk;
+	uint64_t offset = secondary ? hdr->hdr_size : 0;
+	size_t hdr_json_len;
+	int devfd, r;
+
+	log_dbg(cd, "Trying to write LUKS2 header (%zu bytes) at offset %" PRIu64 ".",
+		hdr->hdr_size, offset);
+
+	/* FIXME: read-only device silent fail? */
+
+	devfd = device_open_locked(cd, device, O_RDWR);
+	if (devfd < 0)
+		return devfd == -1 ? -EINVAL : devfd;
+
+	hdr_json_len = hdr->hdr_size - LUKS2_HDR_BIN_LEN;
+
+	hdr_to_disk(hdr, &hdr_disk, secondary, offset);
+
+	/*
+	 * Write header without checksum but with proper seqid.
+	 */
+	if (write_lseek_blockwise(devfd, device_block_size(cd, device),
+				  device_alignment(device), (char *)&hdr_disk,
+				  LUKS2_HDR_BIN_LEN, offset) < (ssize_t)LUKS2_HDR_BIN_LEN) {
+		return -EIO;
+	}
+
+	/*
+	 * Write json area.
+	 */
+	if (write_lseek_blockwise(devfd, device_block_size(cd, device),
+				  device_alignment(device),
+				  CONST_CAST(char*)json_area, hdr_json_len,
+				  LUKS2_HDR_BIN_LEN + offset) < (ssize_t)hdr_json_len) {
+		return -EIO;
+	}
+
+	/*
+	 * Calculate checksum and write header with checksum.
+	 */
+	r = hdr_checksum_calculate(hdr_disk.checksum_alg, &hdr_disk,
+				   json_area, hdr_json_len);
+	if (r < 0) {
+		return r;
+	}
+	log_dbg_checksum(cd, hdr_disk.csum, hdr_disk.checksum_alg, "in-memory");
+
+	if (write_lseek_blockwise(devfd, device_block_size(cd, device),
+				  device_alignment(device), (char *)&hdr_disk,
+				  LUKS2_HDR_BIN_LEN, offset) < (ssize_t)LUKS2_HDR_BIN_LEN)
+		r = -EIO;
+
+	device_sync(cd, device);
+	return r;
+}
+
+static int LUKS2_check_sequence_id(struct crypt_device *cd, struct luks2_hdr *hdr, struct device *device)
+{
+	int devfd;
+	struct luks2_hdr_disk dhdr;
+
+	if (!hdr)
+		return -EINVAL;
+
+	devfd = device_open_locked(cd, device, O_RDONLY);
+	if (devfd < 0)
+		return devfd == -1 ? -EINVAL : devfd;
+
+	/* we need only first 512 bytes, see luks2_hdr_disk structure */
+	if ((read_lseek_blockwise(devfd, device_block_size(cd, device),
+	     device_alignment(device), &dhdr, 512, 0) != 512))
+		return -EIO;
+
+	/* there's nothing to check if there's no LUKS2 header */
+	if ((be16_to_cpu(dhdr.version) != 2) ||
+	    memcmp(dhdr.magic, LUKS2_MAGIC_1ST, LUKS2_MAGIC_L) ||
+	    strcmp(dhdr.uuid, hdr->uuid))
+		return 0;
+
+	return hdr->seqid != be64_to_cpu(dhdr.seqid);
+}
+
+int LUKS2_device_write_lock(struct crypt_device *cd, struct luks2_hdr *hdr, struct device *device)
+{
+	int r = device_write_lock(cd, device);
+
+	if (r < 0) {
+		log_err(cd, _("Failed to acquire write lock on device %s."), device_path(device));
+		return r;
+	}
+
+	/* run sequence id check only on first write lock (r == 1) and w/o LUKS2 reencryption in-progress */
+	if (r == 1 && !crypt_get_luks2_reencrypt(cd)) {
+		log_dbg(cd, "Checking context sequence id matches value stored on disk.");
+		if (LUKS2_check_sequence_id(cd, hdr, device)) {
+			device_write_unlock(cd, device);
+			log_err(cd, _("Detected attempt for concurrent LUKS2 metadata update. Aborting operation."));
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Convert in-memory LUKS2 header and write it to disk.
+ * This will increase sequence id, write both header copies and calculate checksum.
+ */
+int LUKS2_disk_hdr_write(struct crypt_device *cd, struct luks2_hdr *hdr, struct device *device, bool seqid_check)
+{
+	char *json_area;
+	const char *json_text;
+	size_t json_area_len;
+	int r;
+
+	if (hdr->version != 2) {
+		log_dbg(cd, "Unsupported LUKS2 header version (%u).", hdr->version);
+		return -EINVAL;
+	}
+
+	r = device_check_size(cd, crypt_metadata_device(cd), LUKS2_hdr_and_areas_size(hdr), 1);
+	if (r)
+		return r;
+
+	/*
+	 * Allocate and zero JSON area (of proper header size).
+	 */
+	json_area_len = hdr->hdr_size - LUKS2_HDR_BIN_LEN;
+	json_area = crypt_zalloc(json_area_len);
+	if (!json_area)
+		return -ENOMEM;
+
+	/*
+	 * Generate text space-efficient JSON representation to json area.
+	 */
+	json_text = json_object_to_json_string_ext(hdr->jobj,
+			JSON_C_TO_STRING_PLAIN | JSON_C_TO_STRING_NOSLASHESCAPE);
+	if (!json_text || !*json_text) {
+		log_dbg(cd, "Cannot parse JSON object to text representation.");
+		free(json_area);
+		return -ENOMEM;
+	}
+	if (strlen(json_text) > (json_area_len - 1)) {
+		log_dbg(cd, "JSON is too large (%zu > %zu).", strlen(json_text), json_area_len);
+		free(json_area);
+		return -EINVAL;
+	}
+	strncpy(json_area, json_text, json_area_len);
+
+	if (seqid_check)
+		r = LUKS2_device_write_lock(cd, hdr, device);
+	else
+		r = device_write_lock(cd, device);
+	if (r < 0) {
+		free(json_area);
+		return r;
+	}
+
+	/* Increase sequence id before writing it to disk. */
+	hdr->seqid++;
+
+	/* Write primary and secondary header */
+	r = hdr_write_disk(cd, device, hdr, json_area, 0);
+	if (!r)
+		r = hdr_write_disk(cd, device, hdr, json_area, 1);
+
+	if (r)
+		log_dbg(cd, "LUKS2 header write failed (%d).", r);
+
+	device_write_unlock(cd, device);
+
+	free(json_area);
+	return r;
+}
+static int validate_json_area(struct crypt_device *cd, const char *json_area,
+			      uint64_t json_len, uint64_t max_length)
+{
+	char c;
+
+	/* Enforce there are no needless opening bytes */
+	if (*json_area != '{') {
+		log_dbg(cd, "ERROR: Opening character must be left curly bracket: '{'.");
+		return -EINVAL;
+	}
+
+	if (json_len >= max_length) {
+		log_dbg(cd, "ERROR: Missing trailing null byte beyond parsed json data string.");
+		return -EINVAL;
+	}
+
+	/*
+	 * TODO:
+	 *	validate there are legal json format characters between
+	 *	'json_area' and 'json_area + json_len'
+	 */
+
+	do {
+		c = *(json_area + json_len);
+		if (c != '\0') {
+			log_dbg(cd, "ERROR: Forbidden ascii code 0x%02hhx found beyond json data string at offset %" PRIu64,
+				c, json_len);
+			return -EINVAL;
+		}
+	} while (++json_len < max_length);
+
+	return 0;
+}
+
+static int validate_luks2_json_object(struct crypt_device *cd, json_object *jobj_hdr, uint64_t length)
+{
+	int r;
+
+	/* we require top level object to be of json_type_object */
+	r = !json_object_is_type(jobj_hdr, json_type_object);
+	if (r) {
+		log_dbg(cd, "ERROR: Resulting object is not a json object type");
+		return r;
+	}
+
+	r = LUKS2_hdr_validate(cd, jobj_hdr, length);
+	if (r) {
+		log_dbg(cd, "Repairing JSON metadata.");
+		/* try to correct known glitches */
+		LUKS2_hdr_repair(cd, jobj_hdr);
+
+		/* run validation again */
+		r = LUKS2_hdr_validate(cd, jobj_hdr, length);
+	}
+
+	if (r)
+		log_dbg(cd, "ERROR: LUKS2 validation failed");
+
+	return r;
+}
+
+static json_object *parse_and_validate_json(struct crypt_device *cd,
+					    const char *json_area, uint64_t max_length)
+{
+	int json_len, r;
+	json_object *jobj = parse_json_len(cd, json_area, max_length, &json_len);
+
+	if (!jobj)
+		return NULL;
+
+	/* successful parse_json_len must not return offset <= 0 */
+	assert(json_len > 0);
+
+	r = validate_json_area(cd, json_area, json_len, max_length);
+	if (!r)
+		r = validate_luks2_json_object(cd, jobj, max_length);
+
+	if (r) {
+		json_object_put(jobj);
+		jobj = NULL;
+	}
+
+	return jobj;
+}
+
+static int detect_device_signatures(struct crypt_device *cd, const char *path)
+{
+	blk_probe_status prb_state;
+	int r;
+	struct blkid_handle *h;
+
+	if (!blk_supported()) {
+		log_dbg(cd, "Blkid probing of device signatures disabled.");
+		return 0;
+	}
+
+	if ((r = blk_init_by_path(&h, path))) {
+		log_dbg(cd, "Failed to initialize blkid_handle by path.");
+		return -EINVAL;
+	}
+
+	/* We don't care about details. Be fast. */
+	blk_set_chains_for_fast_detection(h);
+
+	/* Filter out crypto_LUKS. we don't care now */
+	blk_superblocks_filter_luks(h);
+
+	prb_state = blk_safeprobe(h);
+
+	switch (prb_state) {
+	case PRB_AMBIGUOUS:
+		log_dbg(cd, "Blkid probe couldn't decide device type unambiguously.");
+		/* fall through */
+	case PRB_FAIL:
+		log_dbg(cd, "Blkid probe failed.");
+		r = -EINVAL;
+		break;
+	case PRB_OK: /* crypto_LUKS type is filtered out */
+		r = -EINVAL;
+
+		if (blk_is_partition(h))
+			log_dbg(cd, "Blkid probe detected partition type '%s'", blk_get_partition_type(h));
+		else if (blk_is_superblock(h))
+			log_dbg(cd, "blkid probe detected superblock type '%s'", blk_get_superblock_type(h));
+		break;
+	case PRB_EMPTY:
+		log_dbg(cd, "Blkid probe detected no foreign device signature.");
+	}
+	blk_free(h);
+	return r;
+}
+
+/*
+ * Read and convert on-disk LUKS2 header to in-memory representation..
+ * Try to do recovery if on-disk state is not consistent.
+ */
+int LUKS2_disk_hdr_read(struct crypt_device *cd, struct luks2_hdr *hdr,
+			struct device *device, int do_recovery, int do_blkprobe)
+{
+	enum { HDR_OK, HDR_OBSOLETE, HDR_FAIL, HDR_FAIL_IO } state_hdr1, state_hdr2;
+	struct luks2_hdr_disk hdr_disk1, hdr_disk2;
+	char *json_area1 = NULL, *json_area2 = NULL;
+	json_object *jobj_hdr1 = NULL, *jobj_hdr2 = NULL;
+	unsigned int i;
+	int r;
+	uint64_t hdr_size;
+	uint64_t hdr2_offsets[] = LUKS2_HDR2_OFFSETS;
+
+	/* Skip auto-recovery if locks are disabled and we're not doing LUKS2 explicit repair */
+	if (do_recovery && do_blkprobe && !crypt_metadata_locking_enabled()) {
+		do_recovery = 0;
+		log_dbg(cd, "Disabling header auto-recovery due to locking being disabled.");
+	}
+
+	/*
+	 * Read primary LUKS2 header (offset 0).
+	 */
+	state_hdr1 = HDR_FAIL;
+	r = hdr_read_disk(cd, device, &hdr_disk1, &json_area1, 0, 0);
+	if (r == 0) {
+		jobj_hdr1 = parse_and_validate_json(cd, json_area1, be64_to_cpu(hdr_disk1.hdr_size) - LUKS2_HDR_BIN_LEN);
+		state_hdr1 = jobj_hdr1 ? HDR_OK : HDR_OBSOLETE;
+	} else if (r == -EIO)
+		state_hdr1 = HDR_FAIL_IO;
+
+	/*
+	 * Read secondary LUKS2 header (follows primary).
+	 */
+	state_hdr2 = HDR_FAIL;
+	if (state_hdr1 != HDR_FAIL && state_hdr1 != HDR_FAIL_IO) {
+		r = hdr_read_disk(cd, device, &hdr_disk2, &json_area2, be64_to_cpu(hdr_disk1.hdr_size), 1);
+		if (r == 0) {
+			jobj_hdr2 = parse_and_validate_json(cd, json_area2, be64_to_cpu(hdr_disk2.hdr_size) - LUKS2_HDR_BIN_LEN);
+			state_hdr2 = jobj_hdr2 ? HDR_OK : HDR_OBSOLETE;
+		} else if (r == -EIO)
+			state_hdr2 = HDR_FAIL_IO;
+	} else {
+		/*
+		 * No header size, check all known offsets.
+		 */
+		for (r = -EINVAL,i = 0; r < 0 && i < ARRAY_SIZE(hdr2_offsets); i++)
+			r = hdr_read_disk(cd, device, &hdr_disk2, &json_area2, hdr2_offsets[i], 1);
+
+		if (r == 0) {
+			jobj_hdr2 = parse_and_validate_json(cd, json_area2, be64_to_cpu(hdr_disk2.hdr_size) - LUKS2_HDR_BIN_LEN);
+			state_hdr2 = jobj_hdr2 ? HDR_OK : HDR_OBSOLETE;
+		} else if (r == -EIO)
+			state_hdr2 = HDR_FAIL_IO;
+	}
+
+	/*
+	 * Check sequence id if both headers are read correctly.
+	 */
+	if (state_hdr1 == HDR_OK && state_hdr2 == HDR_OK) {
+		if (be64_to_cpu(hdr_disk1.seqid) > be64_to_cpu(hdr_disk2.seqid))
+			state_hdr2 = HDR_OBSOLETE;
+		else if (be64_to_cpu(hdr_disk1.seqid) < be64_to_cpu(hdr_disk2.seqid))
+			state_hdr1 = HDR_OBSOLETE;
+	}
+
+	/* check header with keyslots to fit the device */
+	if (state_hdr1 == HDR_OK)
+		hdr_size = LUKS2_hdr_and_areas_size_jobj(jobj_hdr1);
+	else if (state_hdr2 == HDR_OK)
+		hdr_size = LUKS2_hdr_and_areas_size_jobj(jobj_hdr2);
+	else {
+		r = (state_hdr1 == HDR_FAIL_IO && state_hdr2 == HDR_FAIL_IO) ? -EIO : -EINVAL;
+		goto err;
+	}
+
+	r = device_check_size(cd, device, hdr_size, 0);
+	if (r)
+		goto err;
+
+	/*
+	 * Try to rewrite (recover) bad header. Always regenerate salt for bad header.
+	 */
+	if (state_hdr1 == HDR_OK && state_hdr2 != HDR_OK) {
+		log_dbg(cd, "Secondary LUKS2 header requires recovery.");
+
+		if (do_blkprobe && (r = detect_device_signatures(cd, device_path(device)))) {
+			log_err(cd, _("Device contains ambiguous signatures, cannot auto-recover LUKS2.\n"
+				      "Please run \"cryptsetup repair\" for recovery."));
+			goto err;
+		}
+
+		if (do_recovery) {
+			memcpy(&hdr_disk2, &hdr_disk1, LUKS2_HDR_BIN_LEN);
+			r = crypt_random_get(cd, (char*)hdr_disk2.salt, sizeof(hdr_disk2.salt), CRYPT_RND_SALT);
+			if (r)
+				log_dbg(cd, "Cannot generate master salt.");
+			else {
+				hdr_from_disk(&hdr_disk1, &hdr_disk2, hdr, 0);
+				r = hdr_write_disk(cd, device, hdr, json_area1, 1);
+			}
+			if (r)
+				log_dbg(cd, "Secondary LUKS2 header recovery failed.");
+		}
+	} else if (state_hdr1 != HDR_OK && state_hdr2 == HDR_OK) {
+		log_dbg(cd, "Primary LUKS2 header requires recovery.");
+
+		if (do_blkprobe && (r = detect_device_signatures(cd, device_path(device)))) {
+			log_err(cd, _("Device contains ambiguous signatures, cannot auto-recover LUKS2.\n"
+				      "Please run \"cryptsetup repair\" for recovery."));
+			goto err;
+		}
+
+		if (do_recovery) {
+			memcpy(&hdr_disk1, &hdr_disk2, LUKS2_HDR_BIN_LEN);
+			r = crypt_random_get(cd, (char*)hdr_disk1.salt, sizeof(hdr_disk1.salt), CRYPT_RND_SALT);
+			if (r)
+				log_dbg(cd, "Cannot generate master salt.");
+			else {
+				hdr_from_disk(&hdr_disk2, &hdr_disk1, hdr, 1);
+				r = hdr_write_disk(cd, device, hdr, json_area2, 0);
+			}
+			if (r)
+				log_dbg(cd, "Primary LUKS2 header recovery failed.");
+		}
+	}
+
+	free(json_area1);
+	json_area1 = NULL;
+	free(json_area2);
+	json_area2 = NULL;
+
+	/* wrong lock for write mode during recovery attempt */
+	if (r == -EAGAIN)
+		goto err;
+
+	/*
+	 * Even if status is failed, the second header includes salt.
+	 */
+	if (state_hdr1 == HDR_OK) {
+		hdr_from_disk(&hdr_disk1, &hdr_disk2, hdr, 0);
+		hdr->jobj = jobj_hdr1;
+		json_object_put(jobj_hdr2);
+	} else if (state_hdr2 == HDR_OK) {
+		hdr_from_disk(&hdr_disk2, &hdr_disk1, hdr, 1);
+		hdr->jobj = jobj_hdr2;
+		json_object_put(jobj_hdr1);
+	}
+
+	/*
+	 * FIXME: should this fail? At least one header was read correctly.
+	 * r = (state_hdr1 == HDR_FAIL_IO || state_hdr2 == HDR_FAIL_IO) ? -EIO : -EINVAL;
+	 */
+	return 0;
+err:
+	log_dbg(cd, "LUKS2 header read failed (%d).", r);
+
+	free(json_area1);
+	free(json_area2);
+	json_object_put(jobj_hdr1);
+	json_object_put(jobj_hdr2);
+	hdr->jobj = NULL;
+	return r;
+}
+
+int LUKS2_hdr_version_unlocked(struct crypt_device *cd, const char *backup_file)
+{
+	struct {
+		char magic[LUKS2_MAGIC_L];
+		uint16_t version;
+	}  __attribute__ ((packed)) hdr;
+	struct device *device = NULL;
+	int r = 0, devfd = -1, flags;
+
+	if (!backup_file)
+		device = crypt_metadata_device(cd);
+	else if (device_alloc(cd, &device, backup_file) < 0)
+		return 0;
+
+	if (!device)
+		return 0;
+
+	flags = O_RDONLY;
+	if (device_direct_io(device))
+		flags |= O_DIRECT;
+
+	devfd = open(device_path(device), flags);
+	if (devfd < 0)
+		goto err;
+
+	if ((read_lseek_blockwise(devfd, device_block_size(cd, device),
+	     device_alignment(device), &hdr, sizeof(hdr), 0) == sizeof(hdr)) &&
+	    !memcmp(hdr.magic, LUKS2_MAGIC_1ST, LUKS2_MAGIC_L))
+		r = (int)be16_to_cpu(hdr.version);
+err:
+	if (devfd != -1)
+		close(devfd);
+
+	if (backup_file)
+		device_free(cd, device);
+
+	return r;
+}