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authorMaxim Levitsky <mlevitsk@redhat.com>2020-06-25 14:55:42 +0200
committerMax Reitz <mreitz@redhat.com>2020-07-06 08:49:28 +0200
commitbbfdae91fb68783fd54a0f817e3dd9b1c6fe8f8a (patch)
tree0c4f99d982af0376f8e9aa38f7250d57b213d121 /block
parente0d0ddc591a079d2a3da6aa913ba7dd9551fb5ef (diff)
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block/crypto: implement the encryption key management
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> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <20200608094030.670121-8-mlevitsk@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
Diffstat (limited to 'block')
-rw-r--r--block/crypto.c130
-rw-r--r--block/crypto.h34
2 files changed, 161 insertions, 3 deletions
diff --git a/block/crypto.c b/block/crypto.c
index 1960b47..b9c40e6 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -37,6 +37,7 @@ typedef struct BlockCrypto BlockCrypto;
struct BlockCrypto {
QCryptoBlock *block;
+ bool updating_keys;
};
@@ -71,6 +72,24 @@ 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;
@@ -166,6 +185,19 @@ 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_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)
{
@@ -758,6 +790,98 @@ block_crypto_get_specific_info_luks(BlockDriverState *bs, Error **errp)
return spec_info;
}
+static int
+block_crypto_amend_options_luks(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_default_perms(bs, c, role, reopen_queue, perm, shared, nperm, nshared);
+
+ /*
+ * For backward compatibility, manually share the write
+ * and resize permission
+ */
+ *nshared |= (BLK_PERM_WRITE | BLK_PERM_RESIZE);
+ /*
+ * Since we are not fully a format driver, don't always request
+ * the read/resize permission but only when explicitly
+ * requested
+ */
+ *nperm &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE);
+ *nperm |= perm & (BLK_PERM_WRITE | BLK_PERM_RESIZE);
+
+ /*
+ * 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,
@@ -770,13 +894,12 @@ 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_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,
@@ -786,6 +909,7 @@ static BlockDriver bdrv_crypto_luks = {
.bdrv_measure = block_crypto_measure,
.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_luks,
.is_format = true,
diff --git a/block/crypto.h b/block/crypto.h
index 06e044c..c72c3de 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"
+
#define BLOCK_CRYPTO_OPT_DEF_LUKS_KEY_SECRET(prefix) \
BLOCK_CRYPTO_OPT_DEF_KEY_SECRET(prefix, \
@@ -88,6 +93,35 @@
.help = "Time to spend in PBKDF in milliseconds", \
}
+#define BLOCK_CRYPTO_OPT_DEF_LUKS_STATE(prefix) \
+ { \
+ .name = prefix BLOCK_CRYPTO_OPT_LUKS_STATE, \
+ .type = QEMU_OPT_STRING, \
+ .help = "Select new state of affected keyslots (active/inactive)",\
+ }
+
+#define BLOCK_CRYPTO_OPT_DEF_LUKS_KEYSLOT(prefix) \
+ { \
+ .name = prefix BLOCK_CRYPTO_OPT_LUKS_KEYSLOT, \
+ .type = QEMU_OPT_NUMBER, \
+ .help = "Select a single 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 = "Select 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. " \
+ "Empty string to erase", \
+ }
+
QCryptoBlockCreateOptions *
block_crypto_create_opts_init(QDict *opts, Error **errp);