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qcow2: include LUKS payload overhead in qemu-img measure

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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>
This commit is contained in:
Stefan Hajnoczi 2019-02-18 10:45:24 +00:00 committed by Max Reitz
parent 8a57a4be83
commit 61914f8906
1 changed files with 71 additions and 1 deletions
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72
block/qcow2.c
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@ -4236,6 +4236,60 @@ 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)
{
@ -4245,11 +4299,13 @@ static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs,
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 @@ static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs,
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 @@ static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs,
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