Security¶

Two security issues were found during development of nbdkit 1.16. Fixes for these were backported to older stable branches. Upgrading to the fixed versions is highly recommended. The new nbdkit-security(1) man page contains an up to date list of past security issues.

CVE-2019-14850 denial of service due to premature opening of back-end connection

See the full announcement and links to mitigation, tests and fixes here: https://www.redhat.com/archives/libguestfs/2019-September/msg00084.html

CVE-2019-14851 assertion failure by issuing commands in the wrong order

This CVE was caused by the fix to the previous issue.

See the full announcement and links to mitigation, tests and fixes here: https://www.redhat.com/archives/libguestfs/2019-September/msg00272.html

New features¶

Add support for fast zeroing. Plugins can expose this using the new ".can_fast_zero" method (Eric Blake).

nbdkit-partitioning-plugin(1) allows use of "mbr-id=default" or "type-guid=default" to go back to the default MBR byte or partition type GUID.

New --mask-handshake server flag can be used for testing client feature negotiation (Eric Blake).

The client export name is passed to nbdkit-captive(1) --run parameter as $exportname (Eric Blake).

Captive --run commands which fail (eg. aborting) now cause nbdkit to exit with an error instead of errors being silently ignored (Eric Blake).

File descriptors can be passed to password parameters, eg: "password=-3" which means that the password should be read from file descriptor 3.

nbdkit can now serve over the "AF_VSOCK" protocol (thanks Stefan Hajnoczi).

New --log=null option discards error messages.

Plugins¶

Python 2 support has been dropped from nbdkit-python-plugin(3) in line with Python 2 end of life at the beginning of 2020. Python ≥ 3.3 is required by this plugin. If you wish to continue to use Python 2 then you will need to use nbdkit 1.14.

New nbdkit-info-plugin(1) which returns various server information back to the client. It can be used for testing server latency amongst other things.

nbdkit-data-plugin(1) now allows you to write "BYTE*N" to get repeated bytes (eg. "nbdkit data data="0x55*4096"").

nbdkit-ssh-plugin(1) new parameter "compression=true|false" to control transport compression.

nbdkit-vddk-plugin(1) is no longer compiled on non-x86 platforms since VMware has only ever shipped VDDK on x86.

nbdkit-sh-plugin(3) scripts can now see the client exportname and can use the "magic_config_key" feature.

Filters¶

New nbdkit-retry-filter(1) which can reopen the plugin transparently on certain types of failures (lots of help from Eric Blake).

API¶

Macros "NBDKIT_VERSION_MAJOR", "NBDKIT_VERSION_MINOR", "NBDKIT_VERSION_MICRO" expose the compile-time version of nbdkit to plugins and filters (Eric Blake).

Filters (which unlike plugins do not have a public stable API) must now exactly match the version of nbdkit when loaded (Eric Blake).

New ".can_fast_zero" method (Eric Blake).

New "nbdkit_export_name" server function for reading the export name passed by the client.

New "nbdkit_peer_name" server function to return the client address (like getpeername(2)).

New server functions for safely parsing integers: "nbdkit_parse_int", "nbdkit_parse_unsigned", "nbdkit_parse_int8_t", "nbdkit_parse_uint8_t", "nbdkit_parse_int16_t", "nbdkit_parse_uint16_t", "nbdkit_parse_int32_t", "nbdkit_parse_uint32_t", "nbdkit_parse_int64_t", "nbdkit_parse_uint64_t".

Bug fixes¶

".trim" with FUA flag set now works (Eric Blake).

Documentation¶

The previous release notes have been turned into man pages.

Tests¶

Several tests now optionally use nbdsh(1) instead of qemu-io.

You can now fuzz nbdkit using either American Fuzzy Lop or clang’s libFuzzer.

Several tests have had sleep times increased to make them more stable when run on slow or heavily loaded machines.

Internals¶

Reproducible builds (Chris Lamb).

Compile code with -Wshadow warning (Eric Blake).

The internal backend system has been extensively overhauled. In particular this means that we now validate request ranges as requests are passed between filters and down to the plugin, making it easier to find bugs in filters early (Eric Blake).

Plugin size and "can_*" flags are cached more aggressively by the server (Eric Blake).

Variable Length Arrays (VLAs) on stack are now banned throughout the code.

The nbd-protocol.h header describing the NBD protocol is now shared with libnbd(3).

Plugin ".unload" method is now called after all worker threads have exited, avoiding races at server shutdown.

Code was audited using Coverity and various problems were fixed.