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>

1 files changed, 34 insertions, 0 deletions

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"
+
 
 #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);