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Thu, 7 May 2020 12:54:36 +0000 (UTC) From: Maxim Levitsky To: qemu-devel@nongnu.org Subject: [PATCH v5 07/14] block/crypto: implement the encryption key management Date: Thu, 7 May 2020 15:54:07 +0300 Message-Id: <20200507125414.2151-8-mlevitsk@redhat.com> In-Reply-To: <20200507125414.2151-1-mlevitsk@redhat.com> References: <20200507125414.2151-1-mlevitsk@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=205.139.110.120; envelope-from=mlevitsk@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/07 03:15:48 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action 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=20P=2E=20Berrang=C3=A9?= , qemu-block@nongnu.org, John Snow , Markus Armbruster , Max Reitz , Maxim Levitsky Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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 u= sers), 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 Reviewed-by: Daniel P. Berrang=C3=A9 --- block/crypto.c | 127 +++++++++++++++++++++++++++++++++++++++++++++++-- block/crypto.h | 34 +++++++++++++ 2 files changed, 158 insertions(+), 3 deletions(-) diff --git a/block/crypto.c b/block/crypto.c index 38ab0e6aa4..dbc3ab25f4 100644 --- a/block/crypto.c +++ b/block/crypto.c @@ -37,6 +37,7 @@ typedef struct BlockCrypto BlockCrypto; =20 struct BlockCrypto { QCryptoBlock *block; + bool updating_keys; }; =20 =20 @@ -71,6 +72,24 @@ static ssize_t block_crypto_read_func(QCryptoBlock *bloc= k, 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) +{ + 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 header"); + return ret; + } + return ret; +} + =20 struct BlockCryptoCreateData { BlockBackend *blk; @@ -149,6 +168,19 @@ static QemuOptsList block_crypto_create_opts_luks =3D = { }; =20 =20 +static QemuOptsList block_crypto_amend_opts_luks =3D { + .name =3D "crypto", + .head =3D QTAILQ_HEAD_INITIALIZER(block_crypto_create_opts_luks.head), + .desc =3D { + BLOCK_CRYPTO_OPT_DEF_LUKS_STATE(""), + BLOCK_CRYPTO_OPT_DEF_LUKS_KEYSLOT(""), + BLOCK_CRYPTO_OPT_DEF_LUKS_OLD_SECRET(""), + BLOCK_CRYPTO_OPT_DEF_LUKS_NEW_SECRET(""), + BLOCK_CRYPTO_OPT_DEF_LUKS_ITER_TIME(""), + { /* end of list */ } + }, +}; + QCryptoBlockOpenOptions * block_crypto_open_opts_init(QDict *opts, Error **errp) { @@ -741,6 +773,95 @@ block_crypto_get_specific_info_luks(BlockDriverState *= bs, Error **errp) return spec_info; } =20 +static int +block_crypto_amend_options_luks(BlockDriverState *bs, + QemuOpts *opts, + BlockDriverAmendStatusCB *status_cb, + void *cb_opaque, + bool force, + Error **errp) +{ + BlockCrypto *crypto =3D bs->opaque; + QDict *cryptoopts =3D NULL; + QCryptoBlockAmendOptions *amend_options =3D NULL; + int ret; + + assert(crypto); + assert(crypto->block); + crypto->updating_keys =3D true; + + ret =3D bdrv_child_refresh_perms(bs, bs->file, errp); + if (ret < 0) { + goto cleanup; + } + + cryptoopts =3D qemu_opts_to_qdict(opts, NULL); + qdict_put_str(cryptoopts, "format", "luks"); + amend_options =3D block_crypto_amend_opts_init(cryptoopts, errp); + if (!amend_options) { + ret =3D -EINVAL; + goto cleanup; + } + + ret =3D qcrypto_block_amend_options(crypto->block, + block_crypto_read_func, + block_crypto_write_func, + bs, + amend_options, + force, + errp); +cleanup: + crypto->updating_keys =3D false; + bdrv_child_refresh_perms(bs, bs->file, errp); + qapi_free_QCryptoBlockAmendOptions(amend_options); + qobject_unref(cryptoopts); + return ret; +} + + +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; + + bdrv_filter_default_perms(bs, c, role, reopen_queue, + perm, shared, nperm, nshared); + /* + * 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, since + * we will unshare that permission while trying to + * update the encryption keys + */ + if (!(bs->open_flags & BDRV_O_NO_IO)) { + *nperm |=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/read permission. However we need it + * when we are updating the keys, to ensure that only we + * have access to the device. + * + * 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 */ + *nperm |=3D BLK_PERM_WRITE; + /* unshare read and write permission */ + *nshared &=3D ~(BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE); + } +} + + static const char *const block_crypto_strong_runtime_opts[] =3D { BLOCK_CRYPTO_OPT_LUKS_KEY_SECRET, =20 @@ -753,13 +874,12 @@ static BlockDriver bdrv_crypto_luks =3D { .bdrv_probe =3D block_crypto_probe_luks, .bdrv_open =3D block_crypto_open_luks, .bdrv_close =3D block_crypto_close, - /* This driver doesn't modify LUKS metadata except when creating image= . - * Allow share-rw=3Don as a special case. */ - .bdrv_child_perm =3D bdrv_filter_default_perms, + .bdrv_child_perm =3D block_crypto_child_perms, .bdrv_co_create =3D block_crypto_co_create_luks, .bdrv_co_create_opts =3D block_crypto_co_create_opts_luks, .bdrv_co_truncate =3D block_crypto_co_truncate, .create_opts =3D &block_crypto_create_opts_luks, + .amend_opts =3D &block_crypto_amend_opts_luks, =20 .bdrv_reopen_prepare =3D block_crypto_reopen_prepare, .bdrv_refresh_limits =3D block_crypto_refresh_limits, @@ -769,6 +889,7 @@ static BlockDriver bdrv_crypto_luks =3D { .bdrv_measure =3D block_crypto_measure, .bdrv_get_info =3D block_crypto_get_info_luks, .bdrv_get_specific_info =3D block_crypto_get_specific_info_luks, + .bdrv_amend_options =3D block_crypto_amend_options_luks, =20 .strong_runtime_opts =3D block_crypto_strong_runtime_opts, }; diff --git a/block/crypto.h b/block/crypto.h index 06e044c9be..c72c3dec61 100644 --- a/block/crypto.h +++ b/block/crypto.h @@ -41,6 +41,11 @@ #define BLOCK_CRYPTO_OPT_LUKS_IVGEN_HASH_ALG "ivgen-hash-alg" #define BLOCK_CRYPTO_OPT_LUKS_HASH_ALG "hash-alg" #define BLOCK_CRYPTO_OPT_LUKS_ITER_TIME "iter-time" +#define BLOCK_CRYPTO_OPT_LUKS_KEYSLOT "keyslot" +#define BLOCK_CRYPTO_OPT_LUKS_STATE "state" +#define BLOCK_CRYPTO_OPT_LUKS_OLD_SECRET "old-secret" +#define BLOCK_CRYPTO_OPT_LUKS_NEW_SECRET "new-secret" + =20 #define BLOCK_CRYPTO_OPT_DEF_LUKS_KEY_SECRET(prefix) \ BLOCK_CRYPTO_OPT_DEF_KEY_SECRET(prefix, \ @@ -88,6 +93,35 @@ .help =3D "Time to spend in PBKDF in milliseconds", \ } =20 +#define BLOCK_CRYPTO_OPT_DEF_LUKS_STATE(prefix) = \ + { = \ + .name =3D prefix BLOCK_CRYPTO_OPT_LUKS_STATE, = \ + .type =3D QEMU_OPT_STRING, = \ + .help =3D "Select new state of affected keyslots (active/inactive)= ",\ + } + +#define BLOCK_CRYPTO_OPT_DEF_LUKS_KEYSLOT(prefix) \ + { \ + .name =3D prefix BLOCK_CRYPTO_OPT_LUKS_KEYSLOT, \ + .type =3D QEMU_OPT_NUMBER, \ + .help =3D "Select a single keyslot to modify explicitly",\ + } + +#define BLOCK_CRYPTO_OPT_DEF_LUKS_OLD_SECRET(prefix) \ + { \ + .name =3D prefix BLOCK_CRYPTO_OPT_LUKS_OLD_SECRET, \ + .type =3D QEMU_OPT_STRING, \ + .help =3D "Select all keyslots that match this password", \ + } + +#define BLOCK_CRYPTO_OPT_DEF_LUKS_NEW_SECRET(prefix) \ + { \ + .name =3D prefix BLOCK_CRYPTO_OPT_LUKS_NEW_SECRET, \ + .type =3D QEMU_OPT_STRING, \ + .help =3D "New secret to set in the matching keyslots. " \ + "Empty string to erase", \ + } + QCryptoBlockCreateOptions * block_crypto_create_opts_init(QDict *opts, Error **errp); =20 --=20 2.17.2