monitor: Introduce 'block_passwd' command

When using encrypted disk images, QEMU will prompt the user
for passwords when started.

This makes sense for the user protocol, but doesn't for QMP.

The solution is to have Monitor command which allows the user
or a Client to set passwords in advance, so that we avoid
the prompt completely.

This is what block_passwd does, for example:

(QEMU) block_passwd ide0-hd0 foobar

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

2 files changed, 30 insertions, 0 deletions

diff --git a/monitor.c b/monitor.c
index ba76f3416d..27c696b2d4 100644
--- a/monitor.c
+++ b/monitor.c
@@ -772,6 +772,22 @@ static void do_eject(Monitor *mon, const QDict *qdict, QObject **ret_data)
     eject_device(mon, bs, force);
 }
 
+static void do_block_set_passwd(Monitor *mon, const QDict *qdict,
+                                QObject **ret_data)
+{
+    BlockDriverState *bs;
+
+    bs = bdrv_find(qdict_get_str(qdict, "device"));
+    if (!bs) {
+        qemu_error_new(QERR_DEVICE_NOT_FOUND, qdict_get_str(qdict, "device"));
+        return;
+    }
+
+    if (bdrv_set_key(bs, qdict_get_str(qdict, "password")) < 0) {
+        qemu_error_new(QERR_INVALID_PASSWORD);
+    }
+}
+
 static void do_change_block(Monitor *mon, const char *device,
                             const char *filename, const char *fmt)
 {
diff --git a/qemu-monitor.hx b/qemu-monitor.hx
index 62e395bffd..c2670ee1d9 100644
--- a/qemu-monitor.hx
+++ b/qemu-monitor.hx
@@ -1047,6 +1047,20 @@ Close the file descriptor previously assigned to @var{fdname} using the
 used by another monitor command.
 ETEXI
 
+    {
+        .name       = "block_passwd",
+        .args_type  = "device:B,password:s",
+        .params     = "block_passwd device password",
+        .help       = "set the password of encrypted block devices",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_block_set_passwd,
+    },
+
+STEXI
+@item block_passwd @var{device} @var{password}
+Set the encrypted device @var{device} password to @var{password}
+ETEXI
+
 STEXI
 @end table
 ETEXI