similar to: [libnbd PATCH] states: Avoid magic number for h->tls

Similar to the recent --mask-handshake command line added to nbdkit to test client fallbacks to crippled servers, it can be worth testing server fallbacks to crippled clients. And just as we have exposed whether the client will request structured replies, we can also expose whether the client will understand various handshake flags from the NBD protocol. Of course, we default to supporting all

We discovered a possible Downgrade Attack in libnbd. Lifecycle --------- Reported: 2019-09-14 Fixed: 2019-09-16 Published: 2019-09-16 There is no CVE number assigned for this issue yet, but the bug is being categorized and processed by Red Hat's security team which may result in a CVE being published later. Description ----------- Libnbd includes the method nbd_set_tls(h,

When LIBNBD_TLS_ALLOW is used we don't have a way to find out if TLS was really negotiated. This adds a flag and a way to read it back. Unfortunately there is no test yet, because LIBNBD_TLS_ALLOW is not tested -- it really should be but requires quite a complicated set of tests because ideally we'd like to find out whether it falls back correctly for all supported servers. --- TODO

Simple refactoring. --- generator/states-newstyle-opt-export-name.c | 12 +++++------ generator/states-newstyle-opt-go.c | 13 ++++++------ generator/states-oldstyle.c | 10 +++------- lib/flags.c | 22 +++++++++++++++++++++ lib/internal.h | 5 +++++ 5 files changed, 42 insertions(+), 20 deletions(-) diff

On 8/11/20 12:12 PM, Richard W.M. Jones wrote: > I think this needs extra documentation in docs/libnbd.pod because it's > definitely not clear just from the rather thin manual page for > set_opt_mode how it works. docs/libnbd.pod is a good place for a > broader description of how it works. Yes, good idea. State-wise, the existing flow was: Created - Progress only by command

This is the bare minimum needed to allow the user to take control over the rest of option negotiating. This patch adds several new API: nbd_set_opt_mode() - called during Created to enable the new mode nbd_get_opt_mode() - query whether opt mode is enabled nbd_opt_go() - used in Negotiating state to attempt to use export nbd_opt_abort() - used in Negotiating state to skip Connected state

Per recent discussion here: https://www.redhat.com/archives/libguestfs/2019-May/thread.html#00175

This isn't quite finished because not all of the tests or examples have been updated, but it demonstrates an idea: Should we forget about the concept of having multiple connections managed under a single handle? In this patch there is a single ‘struct nbd_handle *’ which manages a single state machine and connection (and therefore no nbd_connection). To connect to a multi-conn server you must

Some of these affect attempts to connect to older qemu-nbd versions, some of them were triggered by manual edits to qemu-nbd source code to provoke various other compliant (if uncommon) server behaviors. Eric Blake (4): starttls: Skip error payload if falling back to unencrypted states: Reject payload to NBD_REP_ACK meta-context: Skip error payload if server lacks meta_context states: Add

It is finally time to introduce our first negotiating option command. With this change, we can now enter NEWSTYLE.START more than once; as such, it needs to know whether it is the first entry (proceed with gflags/cflags, TLS, and structured reply) or a later entry (all nbd_opt_* will cause an IssueCommand event to kick the state machine out of NEGOTIATING, at which point we want to jump to the

No need to duplicate maintenance of export flag computation between old and new style handshakes. Signed-off-by: Eric Blake <eblake@redhat.com> --- src/connections.c | 120 +++++++++++++++++++++--------------------------------- 1 file changed, 47 insertions(+), 73 deletions(-) diff --git a/src/connections.c b/src/connections.c index 8dc1925..f9edea7 100644 --- a/src/connections.c +++

This commit adds a new API which can be used from the connected to state to read back which NBD protocol (eg. oldstyle, newstyle-fixed) we are using. It was helpful to add a new state in newstyle negotiation (%NEWSTYLE.FINISHED) so we can route all successful option negotiations through a single path before moving to the %READY state, allowing us to set h->protocol in one place. ---

Most of the states were calling SET_NEXT_STATE(%.DEAD) then using return -1 on error, to reflect the fact that they had also called set_error() and wanted the caller to notice the failure. Unfortunately, the state machine engine refuses to run the entry code of the next state when the current state returned -1, which meant the DEAD state entry code never runs. A concrete example of the problems

Used both for servers that are not fixed newstyle, and for servers that don't understand NBD_OPT_GO. --- generator/Makefile.am | 1 + generator/generator | 39 +++++++++++ generator/states-newstyle-opt-export-name.c | 73 +++++++++++++++++++++ generator/states-newstyle-opt-go.c | 8 +-- generator/states-newstyle.c | 11

Well, I'm not quite done (I still want to get nbdinfo to work on a single nbd connection for all cases when reading the heads of the file is not required), but I'm happy with patches 1-11, and 12-13 show where I'm headed for getting NBD_OPT_INFO to work. Posting now to see if some of the earlier patches are ready to commit while I continue working on the latter half. Eric Blake (13):

Experimental and only very lightly tested so far. Rich.

I think this needs extra documentation in docs/libnbd.pod because it's definitely not clear just from the rather thin manual page for set_opt_mode how it works. docs/libnbd.pod is a good place for a broader description of how it works. IIUC let me try to explain: we get through as far as the end of group OPT_STRUCTURED_REPLY before we check the opt flag, and then the remainder of opt

The code handling the NBD protocol was located in the same file as the code handling connections, for not really any reason except historical. This is quite a large code movement which splits out the protocol code into four new files: server/protocol-handshake.c initial handshake server/protocol-handshake-newstyle.c " " (newstyle)

Diff against libnbd’s copy of this file, and change this one until it matches. --- common/protocol/nbd-protocol.h | 76 +++++++++++++++++----------- server/protocol-handshake-newstyle.c | 26 +++++----- server/protocol-handshake-oldstyle.c | 4 +- server/protocol.c | 25 ++++----- tests/test-layers.c | 14 ++--- 5 files changed, 81 insertions(+), 64

More nbd-protocol.h improvements Eric Blake (2): common/protocol: Switch nbdmagic to uint64_t common/protocol: Declare additional constants common/protocol/nbd-protocol.h | 16 ++++++++++------ server/protocol-handshake-newstyle.c | 2 +- server/protocol-handshake-oldstyle.c | 2 +- plugins/nbd/nbd-standalone.c | 2 +- tests/test-layers.c | 2 +- 5 files