Security¶

CVE-2021-3716 reset structured replies on starttls

nbdkit was vulnerable to injected plaintext when upgrading to a secure connection. For the full announcement see https://www.redhat.com/archives/libguestfs/2021-August/msg00083.html (Eric Blake).

All past security issues and information about how to report new ones can be found in nbdkit-security(1).

Plugins¶

nbdkit-data-plugin(1) has new "le<NN>:" and "be<NN>:" prefixes for little and big endian words. Also the plugin tries much harder to optimize expressions. The test suite has been greatly expanded to catch potential regressions.

nbdkit-floppy-plugin(1) now allows you to reserve free space (Nolan Leake).

nbdkit-ssh-plugin(1) no longer references SHA1 host keys as part of the effort to remove insecure algorithms (Daniel Berrangé).

nbdkit-vddk-plugin(1) reports "can_flush" and "can_fua" based on what the version of VDDK supports. New debug flag -D vddk.stats=1 prints the amount of time spent in VDDK calls on exit which can be useful for profiling performance.

Filters¶

nbdkit-cow-filter(1) and nbdkit-cache-filter(1) no longer break up large read requests into page-sized requests. In addition the default block size for both filters is now 64K. Both changes greatly improve performance.

nbdkit-cache-filter(1) has a new "cache-on-read=/PATH" parameter allowing callers to enable and disable the cache-on-read feature at runtime. Also there is a new "cache-min-block-size" parameter letting you select the block size at runtime (thanks Martin Kletzander).

nbdkit-cow-filter(1) has a new "cow-on-read" parameter which works similarly to the corresponding cache filter feature. The new "cow-block-size" parameter lets you select the block size at runtime.

nbdkit-cow-filter(1) has less verbose debugging. To restore the old debug output use -D cow.verbose=1

nbdkit-delay-filter(1) has new "delay-open" and "delay-close" parameters to inject delays when clients connect and disconnect. Delay filter parameters are now parsed more accurately (thanks Ming Xie).

Language bindings¶

The OCaml bindings now call "caml_shutdown" when unloading the plugin. This causes "Stdlib.at_exit" handlers to run correctly, closes file descriptors, releases dependent shared libraries and frees memory. Valgrind on OCaml plugins should not show any false positives about leaked memory.

OCaml and Python bindings may now use the ".cleanup" method.

References to Python 2 in nbdkit-python-plugin(3) have been removed.

Server¶

Fix captive nbdkit $uri variable so when TLS is used the URI is constructed with the "nbds:" prefix. Additionally add a new variable $tls which can be used by the subprocess to tell if TLS is enabled.

Debug messages are now printed atomically. This means that debug messages are no longer broken up across multiple lines if there are other processes writing to stderr at the same time (which often happened when using captive nbdkit).

Enhanced valgrind support (./configure --enable-valgrind) can now be enabled safely and with no performance impact even in production builds (Eric Blake).

API¶

Plugins or filters using "nbdkit_nanosleep" now don't hang if the client closes the socket abruptly (thanks Ming Xie).

Bug fixes¶

nbdkit-data-plugin(1) and nbdkit-memory-plugin(1) using allocator=malloc no longer crash because of memory corruption in some corner cases (only seen on s390x, but could happen on other architectures). Meanwhile "allocator=zstd" no longer crashes when zeroing unallocated space.

Tests¶

Tests now use the new "GLIBC_TUNABLES" feature, replacing "MALLOC_CHECK_" on glibc ≥ 2.34 (thanks Eric Blake, Siddhesh Poyarekar).

Build¶

configure.ac now uses spaces consistently, and has been modernized to support the latest autotools (Eric Blake).

podwrapper.pl has been unified (almost) with the copy in libnbd.

Continue fuzzing using AFL++. Updated the fuzzing documentation.