On 15.04.2016 00:02, Eric Blake wrote: > 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 <[email protected]> > --- > > In v2: tweak commit message, continue to drop connection on > NBD_OPT_EXPORT_NAME > > nbd/server.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-)
Thanks Eric, applied to my block branch: https://github.com/XanClic/qemu/commits/block Max
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