| Message ID | 20200114193350.10830-7-mlevitsk@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | LUKS: encryption slot management using amend interface | expand |
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 <mlevitsk@redhat.com> > --- > 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. > + { /* 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... > +{ > + 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 <berrange@redhat.com> Regards, Daniel
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 <mlevitsk@redhat.com> > > --- > > 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 <berrange@redhat.com> Best regards, Thanks for the review, Maxim Levitsky > > > Regards, > Daniel
diff --git a/block/crypto.c b/block/crypto.c index 0b37dae564..081880bced 100644 --- a/block/crypto.c +++ b/block/crypto.c @@ -36,6 +36,7 @@ typedef struct BlockCrypto BlockCrypto; struct BlockCrypto { QCryptoBlock *block; + bool updating_keys; }; @@ -70,6 +71,24 @@ static ssize_t block_crypto_read_func(QCryptoBlock *block, return ret; } +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 = opaque; + ssize_t ret; + + ret = bdrv_pwrite(bs->file, offset, buf, buflen); + if (ret < 0) { + error_setg_errno(errp, -ret, "Could not write encryption header"); + return ret; + } + return ret; +} + struct BlockCryptoCreateData { BlockBackend *blk; @@ -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."), + { /* end of list */ } + }, +}; + QCryptoBlockOpenOptions * block_crypto_open_opts_init(QDict *opts, Error **errp) { @@ -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) +{ + 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"); + 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; +} + + +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 = 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 |= 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 |= BLK_PERM_WRITE; + /* unshare read and write permission */ + *nshared &= ~(BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE); + } +} + + static const char *const block_crypto_strong_runtime_opts[] = { BLOCK_CRYPTO_OPT_LUKS_KEY_SECRET, @@ -673,13 +797,12 @@ static BlockDriver bdrv_crypto_luks = { .bdrv_probe = block_crypto_probe_luks, .bdrv_open = block_crypto_open_luks, .bdrv_close = block_crypto_close, - /* This driver doesn't modify LUKS metadata except when creating image. - * Allow share-rw=on as a special case. */ - .bdrv_child_perm = bdrv_filter_default_perms, + .bdrv_child_perm = block_crypto_child_perms, .bdrv_co_create = block_crypto_co_create_luks, .bdrv_co_create_opts = block_crypto_co_create_opts_luks, .bdrv_co_truncate = block_crypto_co_truncate, .create_opts = &block_crypto_create_opts_luks, + .amend_opts = &block_crypto_amend_opts_luks, .bdrv_reopen_prepare = block_crypto_reopen_prepare, .bdrv_refresh_limits = block_crypto_refresh_limits, @@ -688,6 +811,7 @@ static BlockDriver bdrv_crypto_luks = { .bdrv_getlength = block_crypto_getlength, .bdrv_get_info = block_crypto_get_info_luks, .bdrv_get_specific_info = block_crypto_get_specific_info_luks, + .bdrv_amend_options = block_crypto_amend_options, .strong_runtime_opts = block_crypto_strong_runtime_opts, }; diff --git a/block/crypto.h b/block/crypto.h index 06e044c9be..4af5ab4c94 100644 --- a/block/crypto.h +++ b/block/crypto.h @@ -41,6 +41,10 @@ #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_OLD_SECRET "old-secret" +#define BLOCK_CRYPTO_OPT_LUKS_NEW_SECRET "new-secret" + #define BLOCK_CRYPTO_OPT_DEF_LUKS_KEY_SECRET(prefix) \ BLOCK_CRYPTO_OPT_DEF_KEY_SECRET(prefix, \ @@ -88,6 +92,33 @@ .help = "Time to spend in PBKDF in milliseconds", \ } +#define BLOCK_CRYPTO_OPT_DEF_LUKS_KEYSLOT(prefix) \ + { \ + .name = prefix BLOCK_CRYPTO_OPT_LUKS_KEYSLOT, \ + .type = QEMU_OPT_NUMBER, \ + .help = "Select keyslot to modify explicitly", \ + } + +#define BLOCK_CRYPTO_OPT_DEF_LUKS_OLD_SECRET(prefix) \ + { \ + .name = prefix BLOCK_CRYPTO_OPT_LUKS_OLD_SECRET, \ + .type = QEMU_OPT_STRING, \ + .help = "Modify all keyslots that match this password", \ + } + +#define BLOCK_CRYPTO_OPT_DEF_LUKS_NEW_SECRET(prefix) \ + { \ + .name = prefix BLOCK_CRYPTO_OPT_LUKS_NEW_SECRET, \ + .type = QEMU_OPT_STRING, \ + .help = "New secret to set in the matching keyslots", \ + } + +#define BLOCK_CRYPTO_OPT_DEF_LUKS_KEYSLOT_UPDATE(prefix) \ + BLOCK_CRYPTO_OPT_DEF_LUKS_KEYSLOT(prefix), \ + BLOCK_CRYPTO_OPT_DEF_LUKS_OLD_SECRET(prefix), \ + BLOCK_CRYPTO_OPT_DEF_LUKS_NEW_SECRET(prefix), \ + BLOCK_CRYPTO_OPT_DEF_LUKS_ITER_TIME(prefix) \ + QCryptoBlockCreateOptions * block_crypto_create_opts_init(QDict *opts, Error **errp);
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 <mlevitsk@redhat.com> --- block/crypto.c | 130 +++++++++++++++++++++++++++++++++++++++++++++++-- block/crypto.h | 31 ++++++++++++ 2 files changed, 158 insertions(+), 3 deletions(-)