diff options
| author | Eric Blake <eblake@redhat.com> | 2016-04-14 16:02:23 -0600 |
|---|---|---|
| committer | Max Reitz <mreitz@redhat.com> | 2016-04-15 17:56:56 +0200 |
| commit | d1129a8ad96af6bc47404490769a637bcd860493 (patch) | |
| tree | cb982c9869a1919426e1b74366f5788c744bea31 | |
| parent | 23994a5f524aa575c7a4b2e5250f17b127d2cf2f (diff) | |
nbd: Don't kill server on client that doesn't request TLS
Upstream NBD documents (as of commit 4feebc95) that servers MAY
choose to operate in a conditional mode, where it is up to the
client whether to use TLS. For qemu's case, we want to always be
in FORCEDTLS mode, because of the risk of man-in-the-middle
attacks, and since we never export more than one device; likewise,
the qemu client will ALWAYS send NBD_OPT_STARTTLS as its first
option. But now that SELECTIVETLS servers exist, it is feasible
to encounter a (non-qemu) client that is programmed to talk to
such a server, and does not do NBD_OPT_STARTTLS first, but rather
wants to probe if it can use a non-encrypted export.
The NBD protocol documents that we should let such a client
continue trying, on the grounds that maybe the client will get the
hint to send NBD_OPT_STARTTLS, rather than immediately dropping
the connection.
Note that NBD_OPT_EXPORT_NAME is a special case: since it is the
only option request that can't have an error return, we have to
(continue to) drop the connection on that one; rather, what we are
fixing here is that all other replies prior to TLS initiation tell
the client NBD_REP_ERR_TLS_REQD, but keep the connection alive.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-id: 1460671343-18485-1-git-send-email-eblake@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
| -rw-r--r-- | nbd/server.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/nbd/server.c b/nbd/server.c index 2a4dd10f52..a13a69169a 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -449,11 +449,19 @@ static int nbd_negotiate_options(NBDClient *client) client->ioc = QIO_CHANNEL(tioc); break; + case NBD_OPT_EXPORT_NAME: + /* No way to return an error to client, so drop connection */ + TRACE("Option 0x%x not permitted before TLS", clientflags); + return -EINVAL; + default: TRACE("Option 0x%x not permitted before TLS", clientflags); + if (nbd_negotiate_drop_sync(client->ioc, length) != length) { + return -EIO; + } nbd_negotiate_send_rep(client->ioc, NBD_REP_ERR_TLS_REQD, clientflags); - return -EINVAL; + break; } } else if (fixedNewstyle) { switch (clientflags) { @@ -471,6 +479,9 @@ static int nbd_negotiate_options(NBDClient *client) return nbd_negotiate_handle_export_name(client, length); case NBD_OPT_STARTTLS: + if (nbd_negotiate_drop_sync(client->ioc, length) != length) { + return -EIO; + } if (client->tlscreds) { TRACE("TLS already enabled"); nbd_negotiate_send_rep(client->ioc, NBD_REP_ERR_INVALID, @@ -480,7 +491,7 @@ static int nbd_negotiate_options(NBDClient *client) nbd_negotiate_send_rep(client->ioc, NBD_REP_ERR_POLICY, clientflags); } - return -EINVAL; + break; default: TRACE("Unsupported option 0x%x", clientflags); if (nbd_negotiate_drop_sync(client->ioc, length) != length) { |