[PULL,13/17] crypto: Modify the qcrypto_block_create to support creation flags

diff --git a/block/crypto.c b/block/crypto.c
index e87dc84111..1b3f87922a 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -369,6 +369,7 @@  block_crypto_co_create_generic(BlockDriverState *bs, int64_t size,
                                   block_crypto_create_init_func,
                                   block_crypto_create_write_func,
                                   &data,
+                                  0,
                                   errp);
 
     if (!crypto) {
diff --git a/block/qcow.c b/block/qcow.c
index c6d0e15f1e..ca8e1d5ec8 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -885,7 +885,7 @@  qcow_co_create(BlockdevCreateOptions *opts, Error **errp)
         header.crypt_method = cpu_to_be32(QCOW_CRYPT_AES);
 
         crypto = qcrypto_block_create(qcow_opts->encrypt, "encrypt.",
-                                      NULL, NULL, NULL, errp);
+                                      NULL, NULL, NULL, 0, errp);
         if (!crypto) {
             ret = -EINVAL;
             goto exit;
diff --git a/block/qcow2.c b/block/qcow2.c
index 9bee66fff5..204f5854cf 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3216,7 +3216,7 @@  qcow2_set_up_encryption(BlockDriverState *bs,
     crypto = qcrypto_block_create(cryptoopts, "encrypt.",
                                   qcow2_crypto_hdr_init_func,
                                   qcow2_crypto_hdr_write_func,
-                                  bs, errp);
+                                  bs, 0, errp);
     if (!crypto) {
         return -EINVAL;
     }
diff --git a/crypto/block-luks.c b/crypto/block-luks.c
index 7e1235c213..ab52c9dce1 100644
--- a/crypto/block-luks.c
+++ b/crypto/block-luks.c
@@ -1315,6 +1315,7 @@  qcrypto_block_luks_create(QCryptoBlock *block,
     const char *hash_alg;
     g_autofree char *cipher_mode_spec = NULL;
     uint64_t iters;
+    uint64_t detached_header_size;
 
     memcpy(&luks_opts, &options->u.luks, sizeof(luks_opts));
     if (!luks_opts.has_iter_time) {
@@ -1543,19 +1544,32 @@  qcrypto_block_luks_create(QCryptoBlock *block,
         slot->stripes = QCRYPTO_BLOCK_LUKS_STRIPES;
     }
 
-    /* The total size of the LUKS headers is the partition header + key
-     * slot headers, rounded up to the nearest sector, combined with
-     * the size of each master key material region, also rounded up
-     * to the nearest sector */
-    luks->header.payload_offset_sector = header_sectors +
-            QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS * split_key_sectors;
+    if (block->detached_header) {
+        /*
+         * For a detached LUKS header image, set the payload_offset_sector
+         * to 0 to specify the starting point for read/write
+         */
+        luks->header.payload_offset_sector = 0;
+    } else {
+        /*
+         * The total size of the LUKS headers is the partition header + key
+         * slot headers, rounded up to the nearest sector, combined with
+         * the size of each master key material region, also rounded up
+         * to the nearest sector
+         */
+        luks->header.payload_offset_sector = header_sectors +
+                QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS * split_key_sectors;
+    }
 
     block->sector_size = QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
     block->payload_offset = luks->header.payload_offset_sector *
         block->sector_size;
+    detached_header_size =
+        (header_sectors + QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS *
+         split_key_sectors) * block->sector_size;
 
     /* Reserve header space to match payload offset */
-    initfunc(block, block->payload_offset, opaque, &local_err);
+    initfunc(block, detached_header_size, opaque, &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
         goto error;
diff --git a/crypto/block.c b/crypto/block.c
index 7bb4b74a37..506ea1d1a3 100644
--- a/crypto/block.c
+++ b/crypto/block.c
@@ -87,6 +87,7 @@  QCryptoBlock *qcrypto_block_create(QCryptoBlockCreateOptions *options,
                                    QCryptoBlockInitFunc initfunc,
                                    QCryptoBlockWriteFunc writefunc,
                                    void *opaque,
+                                   unsigned int flags,
                                    Error **errp)
 {
     QCryptoBlock *block = g_new0(QCryptoBlock, 1);
@@ -102,6 +103,7 @@  QCryptoBlock *qcrypto_block_create(QCryptoBlockCreateOptions *options,
     }
 
     block->driver = qcrypto_block_drivers[options->format];
+    block->detached_header = flags & QCRYPTO_BLOCK_CREATE_DETACHED;
 
     if (block->driver->create(block, options, optprefix, initfunc,
                               writefunc, opaque, errp) < 0) {
@@ -146,7 +148,7 @@  qcrypto_block_calculate_payload_offset(QCryptoBlockCreateOptions *create_opts,
         qcrypto_block_create(create_opts, optprefix,
                              qcrypto_block_headerlen_hdr_init_func,
                              qcrypto_block_headerlen_hdr_write_func,
-                             len, errp);
+                             len, 0, errp);
     return crypto != NULL;
 }
 
diff --git a/crypto/blockpriv.h b/crypto/blockpriv.h
index 3c7ccea504..836f3b4726 100644
--- a/crypto/blockpriv.h
+++ b/crypto/blockpriv.h
@@ -42,6 +42,8 @@  struct QCryptoBlock {
     size_t niv;
     uint64_t payload_offset; /* In bytes */
     uint64_t sector_size; /* In bytes */
+
+    bool detached_header; /* True if disk has a detached LUKS header */
 };
 
 struct QCryptoBlockDriver {
diff --git a/include/crypto/block.h b/include/crypto/block.h
index d0d97f5d12..92e823c9f2 100644
--- a/include/crypto/block.h
+++ b/include/crypto/block.h
@@ -116,6 +116,10 @@  QCryptoBlock *qcrypto_block_open(QCryptoBlockOpenOptions *options,
                                  size_t n_threads,
                                  Error **errp);
 
+typedef enum {
+    QCRYPTO_BLOCK_CREATE_DETACHED = (1 << 0),
+} QCryptoBlockCreateFlags;
+
 /**
  * qcrypto_block_create:
  * @options: the encryption options
@@ -123,6 +127,7 @@  QCryptoBlock *qcrypto_block_open(QCryptoBlockOpenOptions *options,
  * @initfunc: callback for initializing volume header
  * @writefunc: callback for writing data to the volume header
  * @opaque: data to pass to @initfunc and @writefunc
+ * @flags: bitmask of QCryptoBlockCreateFlags values
  * @errp: pointer to a NULL-initialized error object
  *
  * Create a new block encryption object for initializing
@@ -134,6 +139,11 @@  QCryptoBlock *qcrypto_block_open(QCryptoBlockOpenOptions *options,
  * generating new master keys, etc as required. Any existing
  * data present on the volume will be irrevocably destroyed.
  *
+ * If @flags contains QCRYPTO_BLOCK_CREATE_DETACHED then
+ * the open process will set the payload_offset_sector to 0
+ * to specify the starting point for the read/write of a
+ * detached LUKS header image.
+ *
  * If any part of initializing the encryption context
  * fails an error will be returned. This could be due
  * to the volume being in the wrong format, a cipher
@@ -147,6 +157,7 @@  QCryptoBlock *qcrypto_block_create(QCryptoBlockCreateOptions *options,
                                    QCryptoBlockInitFunc initfunc,
                                    QCryptoBlockWriteFunc writefunc,
                                    void *opaque,
+                                   unsigned int flags,
                                    Error **errp);
 
 /**
diff --git a/tests/unit/test-crypto-block.c b/tests/unit/test-crypto-block.c
index 347cd5f3d7..6cfc817a92 100644
--- a/tests/unit/test-crypto-block.c
+++ b/tests/unit/test-crypto-block.c
@@ -283,6 +283,7 @@  static void test_block(gconstpointer opaque)
                                test_block_init_func,
                                test_block_write_func,
                                &header,
+                               0,
                                &error_abort);
     g_assert(blk);
 
@@ -362,6 +363,7 @@  test_luks_bad_header(gconstpointer data)
                                test_block_init_func,
                                test_block_write_func,
                                &buf,
+                               0,
                                &error_abort);
     g_assert(blk);