qcow2: include LUKS payload overhead in qemu-img measure
LUKS encryption reserves clusters for its own payload data. The size of
this area must be included in the qemu-img measure calculation so that
we arrive at the correct minimum required image size.
(Ab)use the qcrypto_block_create() API to determine the payload
overhead. We discard the payload data that qcrypto thinks will be
written to the image.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190218104525.23674-2-stefanha@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
diff --git a/block/qcow2.c b/block/qcow2.c
index 92242fb..1de5e24 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -4236,6 +4236,60 @@
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)
{
@@ -4245,11 +4299,13 @@
uint64_t virtual_size; /* disk size as seen by guest */
uint64_t refcount_bits;
uint64_t l2_tables;
+ uint64_t luks_payload_size = 0;
size_t cluster_size;
int version;
char *optstr;
PreallocMode prealloc;
bool has_backing_file;
+ bool has_luks;
/* Parse image creation options */
cluster_size = qcow2_opt_get_cluster_size_del(opts, &local_err);
@@ -4279,6 +4335,20 @@
has_backing_file = !!optstr;
g_free(optstr);
+ optstr = qemu_opt_get_del(opts, BLOCK_OPT_ENCRYPT_FORMAT);
+ has_luks = optstr && strcmp(optstr, "luks") == 0;
+ g_free(optstr);
+
+ if (has_luks) {
+ size_t headerlen;
+
+ if (!qcow2_measure_luks_headerlen(opts, &headerlen, &local_err)) {
+ goto err;
+ }
+
+ luks_payload_size = ROUND_UP(headerlen, cluster_size);
+ }
+
virtual_size = qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0);
virtual_size = ROUND_UP(virtual_size, cluster_size);
@@ -4349,7 +4419,7 @@
info = g_new(BlockMeasureInfo, 1);
info->fully_allocated =
qcow2_calc_prealloc_size(virtual_size, cluster_size,
- ctz32(refcount_bits));
+ ctz32(refcount_bits)) + luks_payload_size;
/* Remove data clusters that are not required. This overestimates the
* required size because metadata needed for the fully allocated file is
