crypto: Modify the qcrypto_block_create to support creation flags

Expand the signature of qcrypto_block_create to enable the
formation of LUKS volumes with detachable headers. To accomplish
that, introduce QCryptoBlockCreateFlags to instruct the creation
process to set the payload_offset_sector to 0.

Signed-off-by: Hyman Huang <yong.huang@smartx.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

3 files changed, 26 insertions, 8 deletions

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 {