If we know a node's version, and it can't do ntor, consider it not running.
If we have a node's descriptor, and it doesn't have a valid ntor key,
consider it not running.
Refactor these checks so they're consistent between authorities and clients.
Before, they checked for version 0.2.4.18-rc or later, but this
would not catch relays without version lines, or buggy or malicious
relays missing an ntor key.
If we did not find a non-private IPaddress by iterating over interfaces,
we would try to get one via
get_interface_address6_via_udp_socket_hack(). This opens a datagram
socket with IPPROTO_UDP. Previously all our datagram sockets (via
libevent) used IPPROTO_IP, so we did not have that in the sandboxing
whitelist. Add (SOCK_DGRAM, IPPROTO_UDP) sockets to the sandboxing
whitelist. Fixes bug 19660.
The test-network-all target assumes the test-driver script lives in the
current working directory. This assumption breaks out-of-tree builds
because it actually lives in the source directory.
Automake 1.12 introduces `LOG_DRIVER` which defines the location of the
test driver script. Because Tor still supports Automake 1.11 we use the
default value of this variable directly. The default value uses the
configured shell for calling the test driver script and explicitly
prefixes the source directory.
This fixes#19608, allowing IPv6-only clients to use
microdescriptors, while preserving the ability of bridge clients
to have some IPv4 bridges and some IPv6 bridges.
Fix on c281c036 in 0.2.8.2-alpha.
We introduded a shadowed variable, thereby causing a log message to
be wrong. Fixes 19578. I believe the bug was introduced by
54d7d31cba in 0.2.2.29-beta.
asciidoc adds a timestamp at the end of a generated HTML file.
This timestamp is based on the date of the file but it can change
depending on the TZ environment variable.
Our sandboxing code would not allow us to write to stats/hidserv-stats,
causing tor to abort while trying to write stats. This was previously
masked by bug#19556.
When sandboxing is enabled, we could not write any stats to disk.
check_or_create_data_subdir("stats"), which prepares the private stats
directory, calls check_private_dir(), which also opens and not just stats() the
directory. Therefore, we need to also allow open() for the stats dir in our
sandboxing setup.
From 0.2.7.2-alpha onwards, Exits would reject all the IP addresses
they knew about in their exit policy. But this may have disclosed
addresses that were otherwise unlisted.
Now, only advertised addresses are rejected by default by
ExitPolicyRejectPrivate. All known addresses are only rejected when
ExitPolicyRejectLocalInterfaces is explicitly set to 1.
If we manually remove fallbacks in C by adding '/*' and '*/' on separate
lines, stem still parses them as being present, because it only looks at
the start of a line.
Add a comment to this effect in the generated source code.
zlib 1.2 came out in 2003; earlier versions should be dead by now.
Our workaround code was only preventing us from using the gzip
encoding (if we decide to do so), and having some dead code linger
around in torgzip.c
The Autoconf macro AC_USE_SYSTEM_EXTENSIONS defines preprocessor macros
which turn on extensions to C and POSIX. The macro also makes it easier
for developers to use the extensions without needing (or forgetting) to
define them manually.
The macro can be safely used because it was introduced in Autoconf 2.60
and Tor requires Autoconf 2.63 and above.
When deleting an ephemeral HS, we were only iterating on circuit with an
OPEN state. However, it could be possible that an intro point circuit didn't
reached the open state yet.
This commit makes it that we close the circuit regardless of its state
except if it was already marked for close.
Fixes#18604
Signed-off-by: David Goulet <dgoulet@torproject.org>
The FetchHidServDescriptors check was placed before the descriptor cache
lookup which made the option not working because it was never using the
cache in the first place.
Fixes#18704
Patched-by: twim
Signef-off-by: David Goulet <dgoulet@torproject.org>
This is a fairly easy way for us to get our test coverage up on
compat_threads.c and workqueue.c -- I already implemented these
tests, so we might as well enable them.
Previously, we used !directory_fetches_from_authorities() to predict
that we would tunnel connections. But the rules have changed
somewhat over the course of 0.2.8
There was a > that should have been an ==, and a missing !. These
together prevented us from issuing a warning in the case that a
nickname matched an Unnamed node only.
Fixes bug 19203; bugfix on 0.2.3.1-alpha.
Remove support for "GET /tor/bytes.txt" DirPort request, and
"GETINFO dir-usage" controller request, which were only available
via a compile-time option in Tor anyway.
Feature was added in 0.2.2.1-alpha. Resolves ticket 19035.
If OpenSSL fails to generate an RSA key, do not retain a dangling
pointer to the previous (uninitialized) key value. The impact here
should be limited to a difficult-to-trigger crash, if OpenSSL is
running an engine that makes key generation failures possible, or if
OpenSSL runs out of memory. Fixes bug 19152; bugfix on
0.2.1.10-alpha. Found by Yuan Jochen Kang, Suman Jana, and Baishakhi
Ray.
This is potentially scary stuff, so let me walk through my analysis.
I think this is a bug, and a backport candidate, but not remotely
triggerable in any useful way.
Observation 1a:
Looking over the OpenSSL code here, the only way we can really fail in
the non-engine case is if malloc() fails. But if malloc() is failing,
then tor_malloc() calls should be tor_asserting -- the only way that an
attacker could do an exploit here would be to figure out some way to
make malloc() fail when openssl does it, but work whenever Tor does it.
(Also ordinary malloc() doesn't fail on platforms like Linux that
overcommit.)
Observation 1b:
Although engines are _allowed_ to fail in extra ways, I can't find much
evidence online that they actually _do_ fail in practice. More evidence
would be nice, though.
Observation 2:
We don't call crypto_pk_generate*() all that often, and we don't do it
in response to external inputs. The only way to get it to happen
remotely would be by causing a hidden service to build new introduction
points.
Observation 3a:
So, let's assume that both of the above observations are wrong, and the
attacker can make us generate a crypto_pk_env_t with a dangling pointer
in its 'key' field, and not immediately crash.
This dangling pointer will point to what used to be an RSA structure,
with the fields all set to NULL. Actually using this RSA structure,
before the memory is reused for anything else, will cause a crash.
In nearly every function where we call crypto_pk_generate*(), we quickly
use the RSA key pointer -- either to sign something, or to encode the
key, or to free the key. The only exception is when we generate an
intro key in rend_consider_services_intro_points(). In that case, we
don't actually use the key until the intro circuit is opened -- at which
point we encode it, and use it to sign an introduction request.
So in order to exploit this bug to do anything besides crash Tor, the
attacker needs to make sure that by the time the introduction circuit
completes, either:
* the e, d, and n BNs look valid, and at least one of the other BNs is
still NULL.
OR
* all 8 of the BNs must look valid.
To look like a valid BN, *they* all need to have their 'top' index plus
their 'd' pointer indicate an addressable region in memory.
So actually getting useful data of of this, rather than a crash, is
going to be pretty damn hard. You'd have to force an introduction point
to be created (or wait for one to be created), and force that particular
crypto_pk_generate*() to fail, and then arrange for the memory that the
RSA points to to in turn point to 3...8 valid BNs, all by the time the
introduction circuit completes.
Naturally, the signature won't check as valid [*], so the intro point
will reject the ESTABLISH_INTRO cell. So you need to _be_ the
introduction point, or you don't actually see this information.
[*] Okay, so if you could somehow make the 'rsa' pointer point to a
different valid RSA key, then you'd get a valid signature of an
ESTABLISH_INTRO cell using a key that was supposed to be used for
something else ... but nothing else looks like that, so you can't use
that signature elsewhere.
Observation 3b:
Your best bet as an attacker would be to make the dangling RSA pointer
actually contain a fake method, with a fake RSA_private_encrypt
function that actually pointed to code you wanted to execute. You'd
still need to transit 3 or 4 pointers deep though in order to make that
work.
Conclusion:
By 1, you probably can't trigger this without Tor crashing from OOM.
By 2, you probably can't trigger this reliably.
By 3, even if I'm wrong about 1 and 2, you have to jump through a pretty
big array of hoops in order to get any kind of data leak or code
execution.
So I'm calling it a bug, but not a security hole. Still worth
patching.
Fortunately, the arithmetic cannot actually overflow, so long as we
*always* check for the size of potentially hostile input before
copying it. I think we do, though. We do check each line against
MAX_LINE_LENGTH, and each object name or object against
MAX_UNPARSED_OBJECT_SIZE, both of which are 128k. So to get this
overflow, we need to have our memarea allocated way way too high up
in RAM, which most allocators won't actually do.
Bugfix on 0.2.1.1-alpha, where memarea was introduced.
Found by Guido Vranken.
Previously, if the header was present, we'd proceed even if the
function wasn't there.
Easy fix for bug 19161. A better fix would involve trying harder to
find libscrypt_scrypt.
We use a pretty specific pair of autoconf tests here to make sure
that we only add this code when:
a) a 64-bit signed multiply fails to link,
AND
b) the same 64-bit signed multiply DOES link correctly when
__mulodi4 is defined.
Closes ticket 19079.
The routerinfo we pass to routerinfo_incompatible_with_extrainfo is
the latest routerinfo for the relay. The signed_descriptor_t, on
the other hand, is the signed_descriptor_t that corresponds to the
extrainfo. That means we should be checking the digest256 match
with that signed_descriptor_t, not with the routerinfo.
Fixes bug 17150 (and 19017); bugfix on 0.2.7.2-alpha.
When parsing detached signature, we make sure that we use the length of the
digest algorithm instead of an hardcoded DIGEST256_LEN in order to avoid
comparing bytes out of bound with a smaller digest length such as SHA1.
Fixes#19066
Signed-off-by: David Goulet <dgoulet@torproject.org>
Previously we'd only check whether the hardening options succeeded
at the compile step. Now we'll try to link with them too, and tell
the user in advance if something seems likely to go wrong.
Closes ticket 18895.
We know there are overflows in curve25519-donna-c32, so we'll have
to have that one be fwrapv.
Only apply the asan, ubsan, and trapv options to the code that does
not need to run in constant time. Those options introduce branches
to the code they instrument.
(These introduced branches should never actually be taken, so it
might _still_ be constant time after all, but branch predictors are
complicated enough that I'm not really confident here. Let's aim for
safety.)
Closes 17983.
Make directory authorities write the v3-status-votes file out
to disk earlier in the consensus process, so we have the votes
even if we abort the consensus process later on.
Resolves ticket 19036.
In dirserv_compute_performance_thresholds, we allocate arrays based
on the length of 'routers', a list of routerinfo_t, but loop over
the nodelist. The 'routers' list may be shorter when relays were
filtered by routers_make_ed_keys_unique, leading to an out-of-bounds
write on directory authorities.
This bug was originally introduced in 26e89742, but it doesn't look
possible to trigger until routers_make_ed_keys_unique was introduced
in 13a31e72.
Fixes bug 19032; bugfix on tor 0.2.8.2-alpha.
This makes our compilation options checks in autoconf work better on
systems that already define _FORTIFY_SOURCE.
Fixes at least one case of bug 18841; bugfix on 0.2.3.17-beta. Patch
from "trudokal".
Previously, we were using the generic schedule for some downloads,
and the consensus schedule for others.
Resolves ticket 18816; fix on fddb814fe in 0.2.4.13-alpha.
We used to be locked in to the "tap" handshake length, and now we can
handle better handshakes like "ntor".
Resolves ticket 18998.
I checked that relay_send_command_from_edge() behaves fine when you
hand it a payload with length 0. Clients behave fine too, since current
clients remain strict about the required length in the rendezvous2 cells.
(Clients will want to become less strict once they have an alternate
format that they're willing to receive.)
This improves client anonymity and avoids directory header tampering.
The extra load on the authorities should be offset by the fallback
directories feature.
This also simplifies the fixes to #18809.
Delete an unnecessary check for non-preferred IP versions.
Allows clients which can't reach any directories of their
preferred IP address version to get directory documents.
Patch on #17840 in 0.2.8.1-alpha.
After #17840 in 0.2.8.1-alpha, we incorrectly chose an IPv4
address for all DIRIND_ONEHOP directory connections,
even if the routerstatus didn't have an IPv4 address.
This likely affected bridge clients with IPv6 bridges.
Resolves#18921.
The problem is that "q" is always set on the first iteration even
if the question is not a supported question. This set of "q" is
not necessary, and will be handled after exiting the loop if there
if a supported q->type was found.
[Changes file by nickm]
lease enter the commit message for your changes. Lines starting
* SHA-3/SHAKE use little endian for certain things, so byteswap as
needed.
* The code was written under the assumption that unaligned access to
quadwords is allowed, which isn't true particularly on non-Intel.
As well as the existing reports of IPv6 address additions or removals,
the script now warns when keys change but IPv4:ORPort or
IPv6:IPv6ORPort remain the same.
Existing checks for other whitelist detail changes have also
been re-worded and upgraded to warnings.
This makes it easier for changes to be identified so operators can
be contacted to confirm whether the change is stable.
Apparently somewhere along the line we decided that MIN might be
missing.
But we already defined it (if it was missing) in compat.h, which
everybody includes.
Closes ticket 18889.
When we connect to a hidden service as a client we may need three internal
circuits, one for the descriptor retrieval, introduction, and rendezvous.
Let's try to make sure we have them. Closes#13239.
Signed-off-by: David Goulet <dgoulet@ev0ke.net>
Unlike tor_assert(), these macros don't abort the process. They're
good for checking conditions we want to warn about, but which don't
warrant a full crash.
This commit also changes the default implementation for
tor_fragile_assert() to tor_assert_nonfatal_unreached_once().
Closes ticket 18613.
Document this convention.
Add a script to post-process .gcov files in order to stop nagging us
about excluded lines.
Teach cov-diff to handle these post-processed files.
Closes ticket 16792
When the directory authorities refuse a bad relay's descriptor,
encourage the relay operator to contact us. Many relay operators
won't notice this line in their logs, but it's a win if even a
few learn why we don't like what their relay was doing.
Resolves ticket 18760.
I didn't specify a contact mechanism (e.g. an email address), because
every time we've done that in the past, a few years later we noticed
that the code was pointing people to an obsolete contact address.
Also, put libor-testing.a at a better position in the list of
libraries, to avoid linker errors.
This is a fix, or part of a fix, for 18490.
Conflicts:
src/test/include.am
This changes simply renames them by removing "Testing" in front of them and
they do not require TestingTorNetwork to be enabled anymore.
Fixes#18481
Signed-off-by: David Goulet <dgoulet@ev0ke.net>
Yes, we could cast to unsigned char first, but it's probably safest
to just use our own (in test_util), or remove bad-idea features that
we don't use (in readpassphrase.c).
Fixes 18728.
Only when we were actually flushing the cell stats to a controller
would we free them. Thus, they could stay in RAM even after the
circuit was freed (eg if we didn't have any controllers).
Fixes bug 18673; bugfix on 0.2.5.1-alpha.
We added these a while ago, but they do no actual good, and
cause implicit declaration warnings in some situations. Rather than
just adding stdint.h, it's easier to remove the exit() calls
as redundant.
Fixes bug 18626; bugfix from "cypherpunks"
This change allows us to simplify path selection for clients, and it
should have minimal effect in practice since >99% of Guards already have
the Stable flag. Implements ticket 18624.
Regardless of the setting of ExtendAllowPrivateAddresses.
This fixes a bug with pluggable transports that ignore the
(potentially private) address in their bridge line.
Fixes bug 18517; bugfix on 23b088907f in tor-0.2.8.1-alpha.
When requesting extrainfo descriptors from a trusted directory
server, check whether it is an authority or a fallback directory
which supports extrainfo descriptors.
Fixes bug 18489; bugfix on 90f6071d8d in tor-0.2.4.7-alpha.
Reported by "atagar", patch by "teor".
Downgrade logs and backtraces about IP versions to
info-level. Only log backtraces once each time tor runs.
Assists in diagnosing bug 18351; bugfix on c3cc8e16e in
tor-0.2.8.1-alpha.
Reported by "sysrqb" and "Christian", patch by "teor".
I had a half-built mechanism to track, during the voting process,
whether the Ed25519 value (or lack thereof) reflected a true
consensus among the authorities. But we never actually inserted this
field in the consensus.
The key idea here is that we first attempt to match up votes by pairs
of <Ed,RSA>, where <Ed> can be NULL if we're told that there is no
Ed key. If this succeeds, then we can treat all those votes as 'a
consensus for Ed'. And we can include all other votes with a
matching RSA key and no statement about Ed keys as being "also about
the same relay."
After that, we look for RSA keys we haven't actually found an entry
for yet, and see if there are enough votes for them, NOT considering
Ed keys. If there are, we match them as before, but we treat them
as "not a consensus about ed".
When we include an entry in a consensus, if it does not reflect a
consensus about ed keys, then we include a new NoEdConsensus flag on
it.
This is all only for consensus method 22 or later.
Also see corresponding dir-spec patch.
When generating a vote, and we have two routerinfos with the same ed
key, omit the one published earlier.
This was supposed to have been solved by key pinning, but when I
made key pinning optional, I didn't realize that this would jump up
and bite us. It is part of bug 18318, and the root cause of 17668.
If we're a server with no address configured, resolve_my_hostname
will need this. But not otherwise. And the preseeding itself can
consume a few seconds if like tails we have no resolvers.
Fixes bug 18548.
Launching 7 descriptor fetches makes a connection to each HSDir that is 6
and the seventh one fails to pick an HSDir because they are all being used
already so it was killing all pending connections at once.
Fixes#15937
Signed-off-by: David Goulet <dgoulet@ev0ke.net>
This simplifies relay behavior, because the relay offers the hsdir
functionality independent of whether the directory authorities have
decided this relay is suitable for clients to use yet.
Implements ticket 18332.
This is in accordance with our usual policy against freelists,
now that working allocators are everywhere.
It should also make memarea.c's coverage higher.
I also doubt that this code ever helped performance.
Short version: clang asan hates the glibc strcmp macro in
bits/string2.h if you are passing it a constant string argument of
length two or less. (I could be off by one here, but that's the
basic idea.)
Closes issue 14821.
CentOS 6 is roughly the oldest thing we care about developers still
using, and it has autoconf 2.63 / automake 1.11. These are both
older than openssl 1.0.0, so anybody who can't upgrade past those
probably can't upgrade to a modern openssl either. And since only
people building from git or editing configure.ac/Makefile.am need to
use autotools, I'm not totally enthused about keeping support for
old ones anyway.
Closes ticket 17732.
Previously, I had left in some debugging code with /*XXX*/ after it,
which nobody noticed. Live and learn! Next time I will use /*XXX
DO NOT COMMIT*/ or something.
We need to define a new consensus method for this; consensus method
21 shouldn't actually be used.
Fixes bug 17702; bugfix on 0.2.7.2-alpha.
Now, when a user who has set EntryNodes finishes bootstrapping, Tor
automatically repopulates the guard set based on this new directory
information. Fixes bug 16825; bugfix on 0.2.3.1-alpha.
If unix socket was configured as listener (such as a ControlSocket or a
SocksPort unix socket), and tor was started as root but not configured
to switch to another user, tor would segfault while trying to string
compare a NULL value. Fixes bug 18261; bugfix on 0.2.8.1-alpha. Patch
by weasel.
We use sensible parameters taken from common sources, and no longer
have dynamic DH groups as an option, but it feels prudent to have
OpenSSL validate p and g at initialization time.
We've never actually tested this support, and we should probably assume
it's broken.
To the best of my knowledge, only OpenVMS has this, and even on
OpenVMS it's a compile-time option to disable it. And I don't think
we build on openvms anyway. (Everybody else seems to be working
around the 2038 problem by using a 64-bit time_t, which won't expire
for roughly 292 billion years.)
Closes ticket 18184.
ClientUseIPv4 0 tells tor to avoid IPv4 client connections.
ClientPreferIPv6DirPort 1 tells tor to prefer IPv6 directory connections.
Refactor policy for IPv4/IPv6 preferences.
Fix a bug where node->ipv6_preferred could become stale if
ClientPreferIPv6ORPort was changed after the consensus was loaded.
Update documentation, existing code, add unit tests.
This closes bug 18162; bugfix on a45b131590, which fixed a related
issue long ago.
In addition to the #18162 issues, this fixes a signed integer overflow
in smarltist_add_all(), which is probably not so great either.
Allow fallback directories which have been stable for 30 days
to work around #18050, which causes relays to submit descriptors
with 0 DirPorts when restarted. (Particularly during Tor version
upgrades.)
Ignore low fallback directory count in alpha builds.
Check size argument to memwipe() for underflow.
Closes bug #18089. Reported by "gk", patch by "teor".
Bugfix on 0.2.3.25 and 0.2.4.6-alpha (#7352),
commit 49dd5ef3 on 7 Nov 2012.
Otherwise, relays publish a descriptor with DirPort 0 when the DirPort
reachability test takes longer than the ORPort reachability test.
Closes bug #18050. Reported by "starlight", patch by "teor".
Bugfix on 0.1.0.1-rc, commit a1f1fa6ab on 27 Feb 2005.
* support maximum history age in _avg_generic_history()
* fix division-by-zero trap in _avg_generic_history()
* skip missing (i.e. null/None) intervals in _avg_generic_history()
* Python timedelta.total_seconds() function not available in 2.6;
replace with equivalent expression
* set DEBUG logging level to make relay exclusion reasons visible
* move CUTOFF_GUARD test to end in order to expose more exclusion
reasons
Patch by "starlight", merge modifications by "teor".
Allow cached or outdated Onionoo data to be used to choose
fallback directories, as long as it's less than a day old.
Modify last modified date checks in preparation for Onionoo change
When _list() is called with AF_UNSPEC family and fails to enumerate
network interfaces using platform specific API, have it call
_hack() twice to find out IPv4 and/or IPv6 address of a machine Tor
instance is running on. This is correct way to handle this case
because _hack() can only be called with AF_INET and AF_INET6 and
does not support any other address family.
OpenSSL doesn't use them, and fwict they were never called. If some
version of openssl *does* start using them, we should test them before
we turn them back on.
See ticket 17926
Fixes bug 17924; bugfix on 0.2.4.1-alpha.
In ddf5020ea8, we added config.log to CLEANFILES in doc/Makefile.am
so that distcheck would be happy about the presence of doc/config.log.
But when we moved to nonrecursie makefiles in 2a4a149624, we
accidentally left that filename unchanged, so that it referred to
config.log instead.
Patch from cypherpunks.
Applies the 6c443e987d fix to router_pick_directory_server_impl.
6c443e987d applied to directory servers chosen from the consensus,
and was:
"Tweak the 9969 fix a little
If we have busy nodes and excluded nodes, then don't retry with the
excluded ones enabled. Instead, wait for the busy ones to be nonbusy."
"Tor has included a feature to fetch the initial consensus from nodes
other than the authorities for a while now. We just haven't shipped a
list of alternate locations for clients to go to yet.
Reasons why we might want to ship tor with a list of additional places
where clients can find the consensus is that it makes authority
reachability and BW less important.
We want them to have been around and using their current key, address,
and port for a while now (120 days), and have been running, a guard,
and a v2 directory mirror for most of that time."
Features:
* whitelist and blacklist for an opt-in/opt-out trial.
* excludes BadExits, tor versions that aren't recommended, and low
consensus weight directory mirrors.
* reduces the weighting of Exits to avoid overloading them.
* places limits on the weight of any one fallback.
* includes an IPv6 address and orport for each FallbackDir, as
implemented in #17327. (Tor won't bootstrap using IPv6 fallbacks
until #17840 is merged.)
* generated output includes timestamps & Onionoo URL for traceability.
* unit test ensures that we successfully load all included default
fallback directories.
Closes ticket #15775. Patch by "teor".
OnionOO script by "weasel", "teor", "gsathya", and "karsten".
* The option is now KeepBindCapabilities
* We now warn if the user specifically asked for KeepBindCapabilities
and we can't deliver.
* The unit tests are willing to start.
* Fewer unused-variable warnings.
* More documentation, fewer misspellings.
Prop210: Add attempt-based connection schedules
Existing tor schedules increment the schedule position on failure,
then retry the connection after the scheduled time.
To make multiple simultaneous connections, we need to increment the
schedule position when making each attempt, then retry a (potentially
simultaneous) connection after the scheduled time.
(Also change find_dl_schedule_and_len to find_dl_schedule, as it no
longer takes or returns len.)
Prop210: Add multiple simultaneous consensus downloads for clients
Make connections on TestingClientBootstrapConsensus*DownloadSchedule,
incrementing the schedule each time the client attempts to connect.
Check if the number of downloads is less than
TestingClientBootstrapConsensusMaxInProgressTries before trying any
more connections.
UseDefaultFallbackDirs enables any hard-coded fallback
directory mirrors. Default is 1, set it to 0 to disable fallbacks.
Implements ticket 17576.
Patch by "teor".
On FreeBSD backtrace(3) uses size_t instead of int (as glibc does). This
causes integer precision loss errors when we used int to store its
results.
The issue is fixed by using size_t to store the results of backtrace(3).
The manual page of glibc does not mention that backtrace(3) returns
negative values. Therefore, no unsigned integer wrapping occurs when its
result is stored in an unsigned data type.
Update the code for IPv6 authorities and fallbacks for function
argument changes.
Update unit tests affected by the function argument changes in
the patch.
Add unit tests for authority and fallback:
* adding via a function
* line parsing
* adding default authorities
(Adding default fallbacks is unit tested in #15775.)
