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Re: [PATCH 06/13] block/crypto: implement the encryption key management
From: |
Maxim Levitsky |
Subject: |
Re: [PATCH 06/13] block/crypto: implement the encryption key management |
Date: |
Thu, 30 Jan 2020 18:08:00 +0200 |
On Tue, 2020-01-28 at 17:27 +0000, Daniel P. Berrangé wrote:
> On Tue, Jan 14, 2020 at 09:33:43PM +0200, Maxim Levitsky wrote:
> > This implements the encryption key management using the generic code in
> > qcrypto layer and exposes it to the user via qemu-img
> >
> > This code adds another 'write_func' because the initialization
> > write_func works directly on the underlying file, and amend
> > works on instance of luks device.
> >
> > This commit also adds a 'hack/workaround' I and Kevin Wolf (thanks)
> > made to make the driver both support write sharing (to avoid breaking the
> > users),
> > and be safe against concurrent metadata update (the keyslots)
> >
> > Eventually the write sharing for luks driver will be deprecated
> > and removed together with this hack.
> >
> > The hack is that we ask (as a format driver) for BLK_PERM_CONSISTENT_READ
> > and then when we want to update the keys, we unshare that permission.
> > So if someone else has the image open, even readonly, encryption
> > key update will fail gracefully.
> >
> > Also thanks to Daniel Berrange for the idea of
> > unsharing read, rather that write permission which allows
> > to avoid cases when the other user had opened the image read-only.
> >
> > Signed-off-by: Maxim Levitsky <address@hidden>
> > ---
> > block/crypto.c | 130 +++++++++++++++++++++++++++++++++++++++++++++++--
> > block/crypto.h | 31 ++++++++++++
> > 2 files changed, 158 insertions(+), 3 deletions(-)
> >
> > @@ -148,6 +167,22 @@ static QemuOptsList block_crypto_create_opts_luks = {
> > };
> >
> >
> > +static QemuOptsList block_crypto_amend_opts_luks = {
> > + .name = "crypto",
> > + .head = QTAILQ_HEAD_INITIALIZER(block_crypto_create_opts_luks.head),
> > + .desc = {
> > + BLOCK_CRYPTO_OPT_DEF_LUKS_KEYSLOT_UPDATE("keys.0."),
> > + BLOCK_CRYPTO_OPT_DEF_LUKS_KEYSLOT_UPDATE("keys.1."),
> > + BLOCK_CRYPTO_OPT_DEF_LUKS_KEYSLOT_UPDATE("keys.2."),
> > + BLOCK_CRYPTO_OPT_DEF_LUKS_KEYSLOT_UPDATE("keys.3."),
> > + BLOCK_CRYPTO_OPT_DEF_LUKS_KEYSLOT_UPDATE("keys.4."),
> > + BLOCK_CRYPTO_OPT_DEF_LUKS_KEYSLOT_UPDATE("keys.5."),
> > + BLOCK_CRYPTO_OPT_DEF_LUKS_KEYSLOT_UPDATE("keys.6."),
> > + BLOCK_CRYPTO_OPT_DEF_LUKS_KEYSLOT_UPDATE("keys.7."),
>
> I'd probably suggest "key.0" or "keyslot.0" as a name.
To be honest, I don't like either of these.
I don't like the 'keys'
array, because it is a bit misleading, as basically each 'key' is a command
that can add/erase an arbitrary keyslot.
I would call this 'command' or cmd at least.
Also note that the 'keys' here is passed as is to qmp parser so if I change it
here, I will have probably
to update the qmp version as well and there the 'keys' name is more or less
agreed upon.
Thoughts?
>
> > + { /* end of list */ }
> > + },
> > +};
> > +
>
>
> > @@ -661,6 +696,95 @@ block_crypto_get_specific_info_luks(BlockDriverState
> > *bs, Error **errp)
> > return spec_info;
> > }
> >
> > +static int
> > +block_crypto_amend_options(BlockDriverState *bs,
> > + QemuOpts *opts,
> > + BlockDriverAmendStatusCB *status_cb,
> > + void *cb_opaque,
> > + bool force,
> > + Error **errp)
>
> This method should have a "_luks" suffix since...
Oops, thanks!
>
> > +{
> > + BlockCrypto *crypto = bs->opaque;
> > + QDict *cryptoopts = NULL;
> > + QCryptoBlockAmendOptions *amend_options = NULL;
> > + int ret;
> > +
> > + assert(crypto);
> > + assert(crypto->block);
> > + crypto->updating_keys = true;
> > +
> > + ret = bdrv_child_refresh_perms(bs, bs->file, errp);
> > + if (ret < 0) {
> > + goto cleanup;
> > + }
> > +
> > + cryptoopts = qemu_opts_to_qdict(opts, NULL);
> > + qdict_put_str(cryptoopts, "format", "luks");
>
> ...it is hardcoded here to assume luks.
>
> > + amend_options = block_crypto_amend_opts_init(cryptoopts, errp);
> > + if (!amend_options) {
> > + ret = -EINVAL;
> > + goto cleanup;
> > + }
> > +
> > + ret = qcrypto_block_amend_options(crypto->block,
> > + block_crypto_read_func,
> > + block_crypto_write_func,
> > + bs,
> > + amend_options,
> > + force,
> > + errp);
> > +cleanup:
> > + crypto->updating_keys = false;
> > + bdrv_child_refresh_perms(bs, bs->file, errp);
> > + qapi_free_QCryptoBlockAmendOptions(amend_options);
> > + qobject_unref(cryptoopts);
> > + return ret;
> > +}
>
> With the minor changes above
>
> Reviewed-by: Daniel P. Berrangé <address@hidden>
Best regards,
Thanks for the review,
Maxim Levitsky
>
>
> Regards,
> Daniel
- Re: [PATCH 04/13] block: amend: separate amend and create options for qemu-img, (continued)
- [PATCH 05/13] block/crypto: rename two functions, Maxim Levitsky, 2020/01/14
- [PATCH 08/13] iotests: filter few more luks specific create options, Maxim Levitsky, 2020/01/14
- [PATCH 07/13] qcow2: extend qemu-img amend interface with crypto options, Maxim Levitsky, 2020/01/14
- [PATCH 06/13] block/crypto: implement the encryption key management, Maxim Levitsky, 2020/01/14
- [PATCH 10/13] block: add generic infrastructure for x-blockdev-amend qmp command, Maxim Levitsky, 2020/01/14
- [PATCH 09/13] qemu-iotests: qemu-img tests for luks key management, Maxim Levitsky, 2020/01/14
- [PATCH 12/13] block/qcow2: implement blockdev-amend, Maxim Levitsky, 2020/01/14
- [PATCH 13/13] iotests: add tests for blockdev-amend, Maxim Levitsky, 2020/01/14
- [PATCH 11/13] block/crypto: implement blockdev-amend, Maxim Levitsky, 2020/01/14