luks: extract qcrypto_block_calculate_payload_offset()

The qcow2 .bdrv_measure() code calculates the crypto payload offset.
This logic really belongs in crypto/block.c where it can be reused by
other image formats.

The "luks" block driver will need this same logic in order to implement
.bdrv_measure(), so extract the qcrypto_block_calculate_payload_offset()
function now.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200221112522.1497712-2-stefanha@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

1 files changed, 19 insertions, 55 deletions

diff --git a/block/qcow2.c b/block/qcow2.c
index 3640e8c07d..f667349e50 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -4608,60 +4608,6 @@ static coroutine_fn int qcow2_co_flush_to_os(BlockDriverState *bs)
     return ret;
 }
 
-static ssize_t qcow2_measure_crypto_hdr_init_func(QCryptoBlock *block,
-        size_t headerlen, void *opaque, Error **errp)
-{
-    size_t *headerlenp = opaque;
-
-    /* Stash away the payload size */
-    *headerlenp = headerlen;
-    return 0;
-}
-
-static ssize_t qcow2_measure_crypto_hdr_write_func(QCryptoBlock *block,
-        size_t offset, const uint8_t *buf, size_t buflen,
-        void *opaque, Error **errp)
-{
-    /* Discard the bytes, we're not actually writing to an image */
-    return buflen;
-}
-
-/* Determine the number of bytes for the LUKS payload */
-static bool qcow2_measure_luks_headerlen(QemuOpts *opts, size_t *len,
-                                         Error **errp)
-{
-    QDict *opts_qdict;
-    QDict *cryptoopts_qdict;
-    QCryptoBlockCreateOptions *cryptoopts;
-    QCryptoBlock *crypto;
-
-    /* Extract "encrypt." options into a qdict */
-    opts_qdict = qemu_opts_to_qdict(opts, NULL);
-    qdict_extract_subqdict(opts_qdict, &cryptoopts_qdict, "encrypt.");
-    qobject_unref(opts_qdict);
-
-    /* Build QCryptoBlockCreateOptions object from qdict */
-    qdict_put_str(cryptoopts_qdict, "format", "luks");
-    cryptoopts = block_crypto_create_opts_init(cryptoopts_qdict, errp);
-    qobject_unref(cryptoopts_qdict);
-    if (!cryptoopts) {
-        return false;
-    }
-
-    /* Fake LUKS creation in order to determine the payload size */
-    crypto = qcrypto_block_create(cryptoopts, "encrypt.",
-                                  qcow2_measure_crypto_hdr_init_func,
-                                  qcow2_measure_crypto_hdr_write_func,
-                                  len, errp);
-    qapi_free_QCryptoBlockCreateOptions(cryptoopts);
-    if (!crypto) {
-        return false;
-    }
-
-    qcrypto_block_free(crypto);
-    return true;
-}
-
 static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs,
                                        Error **errp)
 {
@@ -4712,9 +4658,27 @@ static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs,
     g_free(optstr);
 
     if (has_luks) {
+        g_autoptr(QCryptoBlockCreateOptions) create_opts = NULL;
+        QDict *opts_qdict;
+        QDict *cryptoopts;
         size_t headerlen;
 
-        if (!qcow2_measure_luks_headerlen(opts, &headerlen, &local_err)) {
+        opts_qdict = qemu_opts_to_qdict(opts, NULL);
+        qdict_extract_subqdict(opts_qdict, &cryptoopts, "encrypt.");
+        qobject_unref(opts_qdict);
+
+        qdict_put_str(cryptoopts, "format", "luks");
+
+        create_opts = block_crypto_create_opts_init(cryptoopts, errp);
+        qobject_unref(cryptoopts);
+        if (!create_opts) {
+            goto err;
+        }
+
+        if (!qcrypto_block_calculate_payload_offset(create_opts,
+                                                    "encrypt.",
+                                                    &headerlen,
+                                                    &local_err)) {
             goto err;
         }