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Fri, 4 Oct 2019 18:41:37 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-204-31.brq.redhat.com [10.40.204.31]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B61E019C4F; Fri, 4 Oct 2019 18:41:30 +0000 (UTC) Subject: Re: [PATCH v2 05/11] block/crypto: implement the encryption key management To: Maxim Levitsky , qemu-devel@nongnu.org References: <20190912223028.18496-1-mlevitsk@redhat.com> <20190912223028.18496-6-mlevitsk@redhat.com> From: Max Reitz Autocrypt: addr=mreitz@redhat.com; prefer-encrypt=mutual; keydata= mQENBFXOJlcBCADEyyhOTsoa/2ujoTRAJj4MKA21dkxxELVj3cuILpLTmtachWj7QW+TVG8U /PsMCFbpwsQR7oEy8eHHZwuGQsNpEtNC2G/L8Yka0BIBzv7dEgrPzIu+W3anZXQW4702+uES U29G8TP/NGfXRRHGlbBIH9KNUnOSUD2vRtpOLXkWsV5CN6vQFYgQfFvmp5ZpPeUe6xNplu8V mcTw8OSEDW/ZnxJc8TekCKZSpdzYoxfzjm7xGmZqB18VFwgJZlIibt1HE0EB4w5GsD7x5ekh awIe3RwoZgZDLQMdOitJ1tUc8aqaxvgA4tz6J6st8D8pS//m1gAoYJWGwwIVj1DjTYLtABEB AAG0HU1heCBSZWl0eiA8bXJlaXR6QHJlZGhhdC5jb20+iQFTBBMBCAA9AhsDBQkSzAMABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheABQJVzie5FRhoa3A6Ly9rZXlzLmdudXBnLm5ldAAKCRD0 B9sAYdXPQDcIB/9uNkbYEex1rHKz3mr12uxYMwLOOFY9fstP5aoVJQ1nWQVB6m2cfKGdcRe1 2/nFaHSNAzT0NnKz2MjhZVmcrpyd2Gp2QyISCfb1FbT82GMtXFj1wiHmPb3CixYmWGQUUh+I AvUqsevLA+WihgBUyaJq/vuDVM1/K9Un+w+Tz5vpeMidlIsTYhcsMhn0L9wlCjoucljvbDy/ 8C9L2DUdgi3XTa0ORKeflUhdL4gucWoAMrKX2nmPjBMKLgU7WLBc8AtV+84b9OWFML6NEyo4 4cP7cM/07VlJK53pqNg5cHtnWwjHcbpGkQvx6RUx6F1My3y52vM24rNUA3+ligVEgPYBuQEN BFXOJlcBCADAmcVUNTWT6yLWQHvxZ0o47KCP8OcLqD+67T0RCe6d0LP8GsWtrJdeDIQk+T+F xO7DolQPS6iQ6Ak2/lJaPX8L0BkEAiMuLCKFU6Bn3lFOkrQeKp3u05wCSV1iKnhg0UPji9V2 W5eNfy8F4ZQHpeGUGy+liGXlxqkeRVhLyevUqfU0WgNqAJpfhHSGpBgihUupmyUg7lfUPeRM DzAN1pIqoFuxnN+BRHdAecpsLcbR8sQddXmDg9BpSKozO/JyBmaS1RlquI8HERQoe6EynJhd 64aICHDfj61rp+/0jTIcevxIIAzW70IadoS/y3DVIkuhncgDBvGbF3aBtjrJVP+5ABEBAAGJ ASUEGAEIAA8FAlXOJlcCGwwFCRLMAwAACgkQ9AfbAGHVz0CbFwf9F/PXxQR9i4N0iipISYjU sxVdjJOM2TMut+ZZcQ6NSMvhZ0ogQxJ+iEQ5OjnIputKvPVd5U7WRh+4lF1lB/NQGrGZQ1ic alkj6ocscQyFwfib+xIe9w8TG1CVGkII7+TbS5pXHRxZH1niaRpoi/hYtgzkuOPp35jJyqT/ /ELbqQTDAWcqtJhzxKLE/ugcOMK520dJDeb6x2xVES+S5LXby0D4juZlvUj+1fwZu+7Io5+B bkhSVPb/QdOVTpnz7zWNyNw+OONo1aBUKkhq2UIByYXgORPFnbfMY7QWHcjpBVw9MgC4tGeF R4bv+1nAMMxKmb5VvQCExr0eFhJUAHAhVg== Message-ID: Date: Fri, 4 Oct 2019 20:41:29 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.0 MIME-Version: 1.0 In-Reply-To: <20190912223028.18496-6-mlevitsk@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="RoQBTW66M6aB0Wq27WZhC9VvC1g5fkdbz" X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Fri, 04 Oct 2019 18:41:37 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , qemu-block@nongnu.org, Markus Armbruster , John Snow Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --RoQBTW66M6aB0Wq27WZhC9VvC1g5fkdbz Content-Type: multipart/mixed; boundary="MemsBdKijLAv3NxoNfQwSfMT0Nj4b3TfE" --MemsBdKijLAv3NxoNfQwSfMT0Nj4b3TfE Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 13.09.19 00:30, Maxim Levitsky wrote: > This implements the encryption key management > using the generic code in qcrypto layer > (currently only for qemu-img amend) >=20 > This code adds another 'write_func' because the initialization > write_func works directly on the underlying file, > because during the creation, there is no open instance > of the luks driver, but during regular use, we have it, > and should use it instead. >=20 >=20 > This commit also adds a 'hack/workaround' I and Kevin Wolf (thanks) > made to make the driver still support write sharing, > but be safe against concurrent metadata update (the keys) > Eventually write sharing for luks driver will be deprecated > and removed together with this hack. >=20 > The hack is that we ask (as a format driver) for > BLK_PERM_CONSISTENT_READ always > (technically always unless opened with BDRV_O_NO_IO) >=20 > and then when we want to update the keys, we > unshare that permission. So if someone else > has the image open, even readonly, this will fail. >=20 > Also thanks to Daniel Berrange for the variant of > that hack that involves asking for read, > rather that write permission >=20 > Signed-off-by: Maxim Levitsky > --- > block/crypto.c | 118 +++++++++++++++++++++++++++++++++++++++++++++++--= > 1 file changed, 115 insertions(+), 3 deletions(-) >=20 > diff --git a/block/crypto.c b/block/crypto.c > index a6a3e1f1d8..f42fa057e6 100644 > --- a/block/crypto.c > +++ b/block/crypto.c > @@ -36,6 +36,7 @@ typedef struct BlockCrypto BlockCrypto; > =20 > struct BlockCrypto { > QCryptoBlock *block; > + bool updating_keys; > }; > =20 > =20 > @@ -70,6 +71,24 @@ static ssize_t block_crypto_read_func(QCryptoBlock *= block, > return ret; > } > =20 > +static ssize_t block_crypto_write_func(QCryptoBlock *block, > + size_t offset, > + const uint8_t *buf, > + size_t buflen, > + void *opaque, > + Error **errp) There=E2=80=99s already a function of this name for creation. > +{ > + BlockDriverState *bs =3D opaque; > + ssize_t ret; > + > + ret =3D bdrv_pwrite(bs->file, offset, buf, buflen); > + if (ret < 0) { > + error_setg_errno(errp, -ret, "Could not write encryption heade= r"); > + return ret; > + } > + return ret; > +} > + > =20 > struct BlockCryptoCreateData { > BlockBackend *blk; [...] > +static void > +block_crypto_child_perms(BlockDriverState *bs, BdrvChild *c, > + const BdrvChildRole *role, > + BlockReopenQueue *reopen_queue, > + uint64_t perm, uint64_t shared, > + uint64_t *nperm, uint64_t *nshared) > +{ > + > + BlockCrypto *crypto =3D bs->opaque; > + > + /* > + * Ask for consistent read permission so that if > + * someone else tries to open this image with this permission > + * neither will be able to edit encryption keys > + */ > + if (!(bs->open_flags & BDRV_O_NO_IO)) { > + perm |=3D BLK_PERM_CONSISTENT_READ; > + } > + > + /* > + * This driver doesn't modify LUKS metadata except > + * when updating the encryption slots. > + * Thus unlike a proper format driver we don't ask for > + * shared write permission. However we need it > + * when we area updating keys, to ensure that only we > + * had opened the device r/w > + * > + * Encryption update will set the crypto->updating_keys > + * during that period and refresh permissions > + * > + */ > + > + if (crypto->updating_keys) { > + /*need exclusive write access for header update */ > + perm |=3D BLK_PERM_WRITE; > + shared &=3D ~(BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE); > + } > + > + bdrv_filter_default_perms(bs, c, role, reopen_queue, > + perm, shared, nperm, nshared); > +} This will probably work, but usually drivers do it the other way around: First call any of the default_perms(), and then adjust *nperm and *nshared as required. (perm/shared are what the parents need, *nperm/*nshared is what this driver needs, so it makes more sense that way; and this way nobody has to check whether the settings survived the default_perms() call.) ((But the permissions themselves do look correct.)) Max --MemsBdKijLAv3NxoNfQwSfMT0Nj4b3TfE-- --RoQBTW66M6aB0Wq27WZhC9VvC1g5fkdbz Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl2XklkACgkQ9AfbAGHV z0BINQf9Hj21q3YV5h5AXWwK5ZiA+GOKZTQH4VgzKKobCy5YBlKEaKHHAeupbm2F hTZgBMtlxHy6T2WWMSMj4G8ExtY/Gl4pmpQg2jKlx01ao6s4nHtnImpJZSsSvdyD STaLExoYwA9EYu6Yup4JArKJ0/FvN6hdRxuMPA8Z40PTjjwGwNKb997uGZX7a9j4 cEjA6qSZ7/hdhxlxCuXurYe1B/ff899RMxmHUrHP6dSeGjFHnQo3w5GremUQg2KV RyYXIqPkou/MfYeTfqbLgDOGFNXPJTpqvdKJ2f3Ws38We5svVU9JVVvOaqlb0khy D2Bg2r9GAZ7C4klgPPivvz5fu3CRZQ== =D+aH -----END PGP SIGNATURE----- --RoQBTW66M6aB0Wq27WZhC9VvC1g5fkdbz--