Commit graph

10669 commits

Author SHA1 Message Date
Aram Sargsyan
6539f73e3a Introduce the concept of broken catalog zones
The DNS catalog zones draft version 5 document describes various
situations when a catalog zones must be considered as "broken" and
not be processed.

Implement those checks in catz.c and add corresponding system tests.

(cherry picked from commit a8228d5f19)
2022-04-28 12:48:41 +00:00
Artem Boldariev
02208acbb5 Dig: do not hang on TLS context creation errors
There was a query_detach() call missing in dig, which could lead to
dig hanging on TLS context creation errors. This commit fixes.

The error was introduced because the Strict TLS implementation was
initially made over an older version of the code, where this extra
query_detach() call was not needed.
2022-04-28 13:39:22 +03:00
Artem Boldariev
337943c047 Extend the 'doth' system test with Strict/Mutual TLS checks
This commit extends the 'doth' system test with a set of Strict/Mutual
TLS related checks.

This commit also makes each doth NS instance use its own TLS
certificate that includes FQDN, IPv4, and IPv6 addresses, issued using
a common Certificate Authority, instead of ad-hoc certs.

Extend servers initialisation timeout to 60 seconds to improve the
tests stability in the CI as certain configurations could fail to
initialise on time under load.
2022-04-28 13:39:21 +03:00
Artem Boldariev
d03b4026d5 Add missing plain HTTP options to dig's help output
A couple of dig options were missing in the help output, while been
properly documented and supported. This commit fixes this overlook.
2022-04-28 13:39:21 +03:00
Artem Boldariev
6c05fb09c3 Add support for Strict/Mutual TLS into BIND
This commit adds support for Strict/Mutual TLS into BIND. It does so
by implementing the backing code for 'hostname' and 'ca-file' options
of the 'tls' statement. The commit also updates the documentation
accordingly.
2022-04-28 13:39:21 +03:00
Artem Boldariev
05091f0095 Restore disabled unused 'tls' options: 'ca-file' and 'hostname'
This commit restores the 'tls' options disabled in
78b73d0865.
2022-04-28 13:39:21 +03:00
Artem Boldariev
1f60b32a51 Add support for Strict/Mutual TLS to dig
This commit adds support for Strict/Mutual TLS to dig.

The new command-line options and their behaviour are modelled after
kdig (+tls-ca, +tls-hostname, +tls-certfile, +tls-keyfile) for
compatibility reasons. That is, using +tls-* is sufficient to enable
DoT in dig, implying +tls-ca

If there is no other DNS transport specified via command-line,
specifying any of +tls-* options makes dig use DoT. In this case, its
behaviour is the same as if +tls-ca is specified: that is, the remote
peer's certificate is verified using the platform-specific
intermediate CA certificates store. This behaviour is introduced for
compatibility with kdig.
2022-04-28 13:39:21 +03:00
Matthijs Mekking
125603a543 Add stale answer extended errors
Add DNS extended errors 3 (Stale Answer) and 19 (Stale NXDOMAIN Answer)
to responses. Add extra text with the reason why the stale answer was
returned.

To test, we need to change the configuration such that for the first
set of tests the stale-refresh-time window does not interfer with the
expected extended errors.

(cherry picked from commit c66b9abc0b)
2022-04-28 11:21:22 +02:00
Artem Boldariev
67b9f97664 Extend the doth system test
This commit adds simple checks that the TLS contexts in question are
indeed being updated on DoT and DoH listeners.
2022-04-28 00:03:22 +03:00
Artem Boldariev
f83d128ece Rename yield() to the test_server_yield()
This commit ensures that the test_server binary will build on Solaris,
which has yield() definition within 'unistd.h'.
2022-04-27 20:13:24 +03:00
Petr Špaček
a84871ccca
Add hyperlinks to dig/mdig/delv +options
(cherry picked from commit ac0c2378ca)
2022-04-26 14:06:33 +02:00
Petr Špaček
4c21534009
Split negative and positive dig/mdig/delv options to support Sphinx 1.4.9
Man pages for dig/mdig/delv used `.. option:: +[no]bla` to describe two
options at once, and very old Sphinx does not support that [] in option
names.

Solution is to split negative and positive options into `+bla, +nobla`
form. In the end it improves readability because it transforms hard to
read strings with double brackets from
`+[no]subnet=addr[/prefix-length]` to
`+subnet=addr[/prefix-length], +nosubnet`.

As a side-effect it also allows easier linking to dig/mdig/delv options
using their name directly instead of always overriding the link target
to `+[no]bla` form.

Transformation was done using regex:
    s/:: +\[no\]\(.*\)/:: +\1, +no\1
... and manual review around occurences matching regex
    +no.*=

Fixes: #3301
(cherry picked from commit 0342dddce7)
2022-04-26 14:00:38 +02:00
Petr Špaček
355aebc6df
Use unique program + option names for link anchors to support Sphinx 1.8.5
Sphinx "standard domain" provides directive types ".. program::" and
".. option::" to create link anchor for a program name + option combination.
These can be referenced using :ref:`program option` syntax.

The problem is that Sphinx 1.8.5 (e.g. in Ubuntu 18.04) generates
conflicting link targets if a page contains two option directives
starting with the same word, e.g.:

.. program:: dnssec-settime
.. option:: -P date
.. option:: -P ds date

The reason is that option directive consumes only first word as "option
name" (-P) and all the rest is considered "option argument" (date, ds
date). Newer versions of Sphinx (e.g. 4.5.0) handle this by creating
numbered link anchors, but older versions warn and BIND build system
turns the warning into a hard error.

To handle that we use method recommended by Sphinx maintainer:
https://github.com/sphinx-doc/sphinx/issues/10218#issuecomment-1059925508
As a bonus it provides more accurate link anchors for sub-options.

Alternatives considered:
- Replacing standard domain definition of .. option - causes more
  problems, see BIND issue #3294.
- Removing hyperlinks for options - that would be a step back.

Fixes: #3295
(cherry picked from commit bbb24264bb)
2022-04-25 14:46:37 +02:00
Michał Kępień
fd1f39fe59 Fix a PyLint 2.13.7 error
PyLint 2.13.7 reports the following error:

    bin/tests/system/doth/conftest.py:34:28: E0601: Using variable 'stderr' before assignment (used-before-assignment)

The reason the current code has not caused problems before is that
invoking gnutls-cli with just the --logfile=/dev/null argument causes it
to always return with a non-zero exit code, either due to the option not
being supported or due to the hostname argument not being provided.  In
other words, the 'except' branch has always been taken.  PyLint is
obviously right on a syntactical level, though.

Instead of relying on a less than obvious code flow (where the 'except'
branch is always taken), rework the flagged code by employing
subprocess.run(..., check=False) instead of subprocess.check_output(),
making exception handling redundant.

While this issue was investigated, it was also noticed that
subprocess.check_output() was incorrectly used as a context manager:
Popen objects are context managers, but subprocess.check_output() and
subprocess.run() are not.  Fix by dropping the relevant 'with'
statement.

(cherry picked from commit 3f5318f094)
2022-04-22 12:14:50 +02:00
Michał Kępień
f8d17c6263 Fix "digdelv" system test requirements
Commit f64cd23e7b added a Python-based
name server (bin/tests/system/digdelv/ans8/ans.py) to the "digdelv"
system test, but did not update bin/tests/system/Makefile.am to ensure
Python is present in the test environment before the "digdelv" system
test is run.  Update bin/tests/system/Makefile.am to enforce that
requirement.

(cherry picked from commit aaa0223752)
2022-04-22 12:14:50 +02:00
Tony Finch
037223211c Use wait_for_log_re in the autosign system test
Fix another occurrence of the mistake of passing a regex to
wait_for_log by using the new wait_for_log_re instead.

(cherry picked from commit f4c2909353)
2022-04-20 17:51:40 +01:00
Tony Finch
19cf15313c Avoid timeouts in the notify system test
There were two problems in the notify system test when it waited for
log messages to appear: the shellcheck refactoring introduced a call
to `wait_for_log` with a regex, but `wait_for_log` only supports fixed
strings, so it always ran for the full 45 second timeout; and the new
test to ensure that notify messages time out failed to reset the
nextpart pointer, so if the notify messages timed out before the test
ran, it would fail to see them.

This change adds a `wait_for_log_re` helper that matches a regex, and
uses it where appropriate in the notify system test, which stops the
test from waiting longer than necessary; and it resets the nextpart
pointer so that the notify timeout test works reliably.

Closes #3275

(cherry picked from commit 4a30733ae5)
2022-04-20 17:51:40 +01:00
Mark Andrews
b597ea863e Check that pending negative cache entries for DS can be used successfully
Prime the cache with a negative cache DS entry then make a query for
name beneath that entry. This will cause the DS entry to be retieved
as part of the validation process.  Each RRset in the ncache entry
will be validated and the trust level for each will be updated.

(cherry picked from commit d2d9910da2)
2022-04-19 09:44:09 +10:00
Evan Hunt
50dc4f1587 ensure dig sets exitcode after local UDP connection failure
dig previously set an exit code of 9 when a TCP connection failed
or when a UDP connection timed out, but when the server address is
localhost it's possible for a UDP query to fail with ISC_R_CONNREFUSED.
that code path didn't update the exit code, causing dig to exit with
status 0. we now set the exit code to 9 in this failure case.

(cherry picked from commit 4eee6460ff)
2022-04-15 11:08:46 -07:00
Aram Sargsyan
c37a75df5d Implement catalog zones change of ownership (coo) support
Catalog zones change of ownership is special mechanism to facilitate
controlled migration of a member zone from one catalog to another.

It is implemented using catalog zones property named "coo" and is
documented in DNS catalog zones draft version 5 document.

Implement the feature using a new hash table in the catalog zone
structure, which holds the added "coo" properties for the catalog zone
(containing the target catalog zone's name), and the key for the hash
table being the member zone's name for which the "coo" property is being
created.

Change some log messages to have consistent zone name quoting types.

Update the ARM with change of ownership documentation and usage
examples.

Add tests which check newly the added features.

(cherry picked from commit bb837db4ee)
2022-04-14 20:53:31 +00:00
Aram Sargsyan
f75c39811d Implement catalog zones options new syntax based on custom properties
According to DNS catalog zones draft version 5 document, catalog
zone custom properties must be placed under the "ext" label.

Make necessary changes to support the new custom properties syntax in
catalog zones with version "2" of the schema.

Change the default catalog zones schema version from "1" to "2" in
ARM to prepare for the new features and changes which come starting
from this commit in order to support the latest DNS catalog zones draft
document.

Make some restructuring in ARM and rename the term catalog zone "option"
to "custom property" to better reflect the terms used in the draft.

Change the version of 'catalog1.zone.' catalog zone in the "catz" system
test to "2", and leave the version of 'catalog2.zone.' catalog zone at
version "1" to test both versions.

Add tests to check that the new syntax works only with the new schema
version, and that the old syntax works only with the legacy schema
version catalog zones.

(cherry picked from commit cedfebc64a)
2022-04-14 19:51:22 +00:00
Evan Hunt
7c0ef393d8 detach unfinished query when canceling
when a query was canceled while still in the process of connecting,
tcp_connected() and udp_ready() didn't detach the query object.

(cherry picked from commit 6bf8535542)
2022-04-14 09:40:50 +00:00
Aram Sargsyan
7683d6ce69 Unify dig +nssearch next query starting code for TCP and UDP protocols
In `+nssearch` mode `dig` starts the next query of the followup lookup
using `start_udp()` or `start_tcp()` calls without waiting for the
previous query to complete.

In UDP mode that happens in the `send_done()` callback of the previous
query, but in TCP mode that happens in the `start_tcp()` call of the
previous query (recursion) which doesn't work because `start_tcp()`
attaches the `lookup->current_query` to the query it is starting, so a
recursive call will result in an assertion failure.

Make the TCP mode to start the next query in `send_done()`, just like in
the UDP mode. During that time the `lookup->current_query` is already
detached by the `tcp_connected()`/`udp_ready()` callbacks.

(cherry picked from commit b944bf4120)
2022-04-14 09:40:37 +00:00
Matthijs Mekking
d975d07155 Test CDS DELETE persists after zone sign
Add a test case for a dynamically added CDS DELETE record and make
sure it is not removed when signing the zone. This happens because
BIND maintains CDS and CDNSKEY publishing and it will only allow
CDS DELETE records if the zone is transitioning to insecure. This is
a state that can be identified when using KASP through 'dnssec-policy',
but not when using 'auto-dnssec'.

(cherry picked from commit f08277f9fb)
2022-04-13 14:43:34 +02:00
Michał Kępień
80089f52e5 Fix "forward" system test requirements
Commit 3b3495a631 added a Python-based
name server (bin/tests/system/forward/ans11/ans.py) to the "forward"
system test, but did not update bin/tests/system/Makefile.am to ensure
Python is present in the test environment before the "forward" system
test is run.  Update bin/tests/system/Makefile.am to enforce that
requirement.

(cherry picked from commit 806f457147)
2022-04-12 15:30:31 +02:00
Aram Sargsyan
db3ab0b46e
Add a hung fetch check while chasing DS in the forward system test
Implement TCP support in the `ans11` Python-based DNS server.

Implement a control command channel in `ans11` to support an optional
silent mode of operation, which, when enabled, will ignore incoming
queries.

In the added check, make the `ans11` the NS server of
"a.root-servers.nil." for `ns3`, so it uses `ans11` (in silent mode)
for the regular (non-forwarded) name resolutions.

This will trigger the "hung fetch" scenario, which was causing `named`
to crash.

(cherry picked from commit 848094d6f7)
2022-04-08 12:19:04 +02:00
Mark Andrews
3b3495a631
Add tests for forwarder cache poisoning scenarios
- Check that an NS in an authority section returned from a forwarder
  which is above the name in a configured "forward first" or "forward
  only" zone (i.e., net/NS in a response from a forwarder configured for
  local.net) is not cached.
- Test that a DNAME for a parent domain will not be cached when sent
  in a response from a forwarder configured to answer for a child.
- Check that glue is rejected if its name falls below that of zone
  configured locally.
- Check that an extra out-of-bailiwick data in the answer section is
  not cached (this was already working correctly, but was not explicitly
  tested before).

(cherry picked from commit bf3fffff67)
2022-04-07 19:30:43 +02:00
Matthijs Mekking
b79c04d5f6
Add system test lingering CLOSE_WAIT TCP sockets
Add a test case to check for lingering TCP sockets stuck in the
CLOSE_WAIT state. This can happen if a client sends some garbage after
its first query.

The system test runs the reproducer script and then sends another TCP
query to the resolver. The resolver is configured to allow one TCP
client only. If BIND has its TCP socket stuck in CLOSE_WAIT, it does
not have the resources available to answer the second query.

Note: A better test would be to check if the named daemon does not
have a TCP socket stuck in CLOSE_WAIT for example with netstat. When
running this test locally you can examine named with netstat manually.
But since netstat is platform specific it is not a good candidate to do
this as a system test.

If you, if you could return, don't let it burn.
Do you have to let it linger?
- Cranberries

(cherry picked from commit b9ebde705b)
2022-04-07 18:07:08 +02:00
Petr Špaček
8961dc452e
Generate JUnit reports for unit & system tests
This allows Gitlab to show nice summary for individual tests/test
directories and to expose the results in Gitlab API for consumption
elsewhere.

A catch: As of Gitlab 14.7.7, the detailed results are stored
only in artifacts and thus expire. All consumers (including API) need
to be "fast enough" to get the data before they disappear.
This also forces us to always store the artifacts intead of storing them
only on failure.

(cherry picked from commit d26d4f289f)
2022-04-06 21:16:00 +02:00
Tony Finch
4191fd01be Ensure that dns_request_createvia() has a retry limit
There are a couple of problems with dns_request_createvia(): a UDP
retry count of zero means unlimited retries (it should mean no
retries), and the overall request timeout is not enforced. The
combination of these bugs means that requests can be retried forever.

This change alters calls to dns_request_createvia() to avoid the
infinite retry bug by providing an explicit retry count. Previously,
the calls specified infinite retries and relied on the limit implied
by the overall request timeout and the UDP timeout (which did not work
because the overall timeout is not enforced). The `udpretries`
argument is also changed to be the number of retries; previously, zero
was interpreted as infinity because of an underflow to UINT_MAX, which
appeared to be a mistake. And `mdig` is updated to match the change in
retry accounting.

The bug could be triggered by zone maintenance queries, including
NOTIFY messages, DS parental checks, refresh SOA queries and stub zone
nameserver lookups. It could also occur with `nsupdate -r 0`.
(But `mdig` had its own code to avoid the bug.)

(cherry picked from commit 71ce8b0a51)
2022-04-06 18:17:55 +01:00
Tony Finch
9bcc537882 Make notify test shellcheck clean
Use POSIX shell syntax, and use functions to reduce repetition.

(cherry picked from commit 5867c1b727)
2022-04-06 18:16:44 +01:00
Ondřej Surý
a1f3ff0dd1 Rename the configuration option to load balance sockets to reuseport
After some back and forth, it was decidede to match the configuration
option with unbound ("so-reuseport"), PowerDNS ("reuseport") and/or
nginx ("reuseport").

(cherry picked from commit 7e71c4d0cc)
2022-04-06 17:24:13 +02:00
Aram Sargsyan
bf9bec6f91 Fix using unset pointer when printing a debug message in dighost.c
The used `query->handle` is always `NULL` at this point.

Change the code to use `handle` instead.

(cherry picked from commit 5b2b3e589c)
2022-04-05 11:54:06 +00:00
Aram Sargsyan
927f00e15d Add a missing clear_current_lookup() call in recv_done()
The error code path handling the `ISC_R_CANCELED` code lacks a
`clear_current_lookup()` call, without which dig hangs indefinitely
when handling the error.

Add the missing call to account for all references of the lookup so
it can be destroyed.

(cherry picked from commit 2771a5b64d)
2022-04-05 11:53:52 +00:00
Aram Sargsyan
8e57030f69 When using +qr in dig print the data of the current query
In `send_udp()` and `launch_next_query()` functions, when calling
`dighost_printmessage()` to print detailed information about the
sent query, dig always prints the data of the first query in the
lookup's queries list.

The first query in the list can be already finished, having its handles
freed, and accessing this information results in assertion failure.

Print the current query's information instead.

(cherry picked from commit f831e758d1)
2022-04-05 11:53:45 +00:00
Mark Andrews
072e77dc9d
Add regression test for CVE-2022-0635
(cherry picked from commit 56fbed2f0f)
2022-04-05 11:03:20 +02:00
Mark Andrews
88265211cb Use multiple fixed expressions for portable grep usage
Additionally add "network unreachable" as an expected error message.

(cherry picked from commit 9ef4d2b583)
2022-04-05 14:34:40 +10:00
Ondřej Surý
cd24556e14 Enable the load-balance-sockets configuration
Previously, HAVE_SO_REUSEPORT_LB has been defined only in the private
netmgr-int.h header file, making the configuration of load balanced
sockets inoperable.

Move the missing HAVE_SO_REUSEPORT_LB define the isc/netmgr.h and add
missing isc_nm_getloadbalancesockets() implementation.

(cherry picked from commit 142c63dda8)
2022-04-05 01:38:49 +02:00
Ondřej Surý
64265f1c0e Add option to configure load balance sockets
Previously, the option to enable kernel load balancing of the sockets
was always enabled when supported by the operating system (SO_REUSEPORT
on Linux and SO_REUSEPORT_LB on FreeBSD).

It was reported that in scenarios where the networking threads are also
responsible for processing long-running tasks (like RPZ processing, CATZ
processing or large zone transfers), this could lead to intermitten
brownouts for some clients, because the thread assigned by the operating
system might be busy.  In such scenarious, the overall performance would
be better served by threads competing over the sockets because the idle
threads can pick up the incoming traffic.

Add new configuration option (`load-balance-sockets`) to allow enabling
or disabling the load balancing of the sockets.

(cherry picked from commit 85c6e797aa)
2022-04-04 23:59:59 +02:00
Tony Finch
541222043d MacOS needs more IP addresses to run the system tests
The launchd script only counted up to 8 whereas ifconfig.sh went all
the way up to 10, and even a bit further than that.

(cherry picked from commit 29a3e77425)
2022-04-04 15:06:31 +01:00
Aram Sargsyan
1294de8e36 Fix dig hanging issue in cases when the lookup's next query can't start
In recv_done(), when dig decides to start the lookup's next query in
the line using `start_udp()` or `start_tcp()`, and for some reason,
no queries get started, dig doesn't cancel the lookup.

This can occur, for example, when there are two queries in the lookup,
one with a regular IP address, and another with a IPv4 mapped IPv6
address. When the regular IP address fails to serve the query, its
`recv_done()` callback starts the next query in the line (in this
case the one with a mapped IP address), but because `dig` doesn't
connect to such IP addresses, and there are no other queries in the
list, no new queries are being started, and the lookup keeps hanging.

After calling `start_udp()` or `start_tcp()` in `recv_done()`, check
if there are no pending/working queries then cancel the lookup instead
of only detaching from the current query.

(cherry picked from commit 7e2f50c369)
2022-04-04 09:18:46 +00:00
Evan Hunt
a18c824f6a fix resolver test when built without --enable-querytrace
a test case in the 'resolver' system test was reliant on
logged output that would only be present when query tracing
was enabled, as in developer builds. that test case is now
disabled when query tracing is not available. Thanks to
Anton Castelli.

(cherry picked from commit 5319d8adea)
2022-04-01 10:17:00 -07:00
Aram Sargsyan
cfdf95d437 Synchronze udp_ready() and tcp_connected() functions entry behavior
The `udp_ready()` and `tcp_connected()` functions in dighost.c are
used for similar purposes for UDP and TCP respectively.

Synchronize the `udp_ready()` function entry code to behave like
`tcp_connected()` by adding input validation, debug messages and
early exit code when `cancel_now` is `true`.

(cherry picked from commit 4477f71868)
2022-04-01 11:53:47 +00:00
Aram Sargsyan
16bdced2ca Fix "dig +nssearch" indefinitely hanging issue
When finishing the NSSEARCH task and there is no more followup
lookups to start, dig does not destroy the last lookup, which
causes it to hang indefinitely.

Rename the unused `first_pass` member of `dig_query_t` to `started`
and make it `true` in the first callback after `start_udp()` or
`start_tcp()` of the query to indicate that the query has been
started.

Create a new `check_if_queries_done()` function to check whether
all of the queries inside a lookup have been started and finished,
or canceled.

Use the mentioned function in the TRACE code block in `recv_done()`
to check whether the current query is the last one in the lookup and
cancel the lookup in that case to free the resources.

(cherry picked from commit 7d360bd05e)
2022-04-01 11:53:33 +00:00
Evan Hunt
953f62c1e7 add a system test for $GENERATE with an integer overflow
the line "$GENERATE 19-28/2147483645 $ CNAME x" should generate
a single CNAME with the owner "19.example.com", but prior to the
overflow bug it generated several CNAMEs, half of them with large
negative values.

we now test for the bugfix by using "named-checkzone -D" and
grepping for a single CNAME in the output.

(cherry picked from commit bd814b79d4)
2022-04-01 21:42:35 +11:00
Evan Hunt
8ac8197f0d update shell syntax
clean up the shell syntax in the checkzone test prior to adding
a new test.

(cherry picked from commit 2261c853b5)
2022-04-01 21:42:35 +11:00
Tony Finch
ec54de9e47 Log "not authoritative for update zone" more clearly
Ensure the update zone name is mentioned in the NOTAUTH error message
in the server log, so that it is easier to track down problematic
update clients. There are two cases: either the update zone is
unrelated to any of the server's zones (previously no zone was
mentioned); or the update zone is a subdomain of one or more of the
server's zones (previously the name of the irrelevant parent zone was
misleadingly logged).

Closes #3209

(cherry picked from commit 84c4eb02e7)
2022-03-30 13:19:46 +01:00
Ondřej Surý
fc500b96eb Consistenly use UNREACHABLE() instead of ISC_UNREACHABLE()
In couple places, we have missed INSIST(0) or ISC_UNREACHABLE()
replacement on some branches with UNREACHABLE().  Replace all
ISC_UNREACHABLE() or INSIST(0) calls with UNREACHABLE().
2022-03-28 23:27:33 +02:00
Aram Sargsyan
263b9d69af Cleanup the code to remove unnecessary indentation
Because of the "goto" in the "if" body the "else" part is unnecessary
and adds another level of indentation.

Cleanup the code to not have the "else" part.

(cherry picked from commit 9b84bfb5f4)
2022-03-28 10:26:42 +00:00
Aram Sargsyan
c79c059c4e Log a warning when catz is told to modify a zone not added by catz
Catz logs a warning message when it is told to modify a zone which was
not added by the current catalog zone.

When logging a warning, distinguish the two cases when the zone
was not added by a catalog zone at all, and when the zone was
added by a different catalog zone.

(cherry picked from commit d29e5f197b)
2022-03-28 10:26:35 +00:00