[Bro] Bro 1.5 release now available
vern at icir.org
Wed Dec 16 22:28:05 PST 2009
Bro release 1.5 is now available from:
This release includes new functionality as well as numerous refinements
and fixes, per the appended changelog entries.
Previous releases are available at http://www.bro-ids.org/download.html .
1.5 Wed Dec 16 21:28:47 PST 2009
- Bro now comes with a new framework, BroControl, for managing an
operational Bro setup, including support for installation, configuration,
and maintainance tasks such a log archival and mail notification. The
framework transparently supports both traditional standalone setups as
well as cluster installations in which multiple Bro boxes coordinate to
analyze a high-volume network link.
See aux/broctl/README for more information about BroControl.
Note, BroControl supersedes the older BroLite system, which is no longer
supported and has been deprecated for a while now.
- Numerous adjustments to DPD = dynamic protocol detection (Robin Sommer):
o The Analyzer::ProtocolViolation?() method can now be passed the
offending data (which POP3, SMTP, and FTP now do). This information
is added to the "reason" string passed to the script level.
o SMTP now more accurately reports violations.
o FTP stops processing when client & server successfully negotiate
an AUTH scheme (leading to subsequent encryption).
o Analyzer::ProtocolViolation() is virtual, and
TCP_ApplicationAnalyzer() overrides it to not report violations
for any partial connections, because very likely these arise just
due to the analyzer getting confused.
o TCP::IsPartial() returns true if any side did not start with
a SYN packet (used to be just be for the originator).
o The connection_state_remove handler in conn.bro now has a higher
&priority so that other handlers for the same event can use
determine_service() and see any changes it performs.
o DynDisable:max_volume specifies a volume limit (default 10K).
Once a connection exceeds this limit, further protocol
limitations will neither raise ProtocolViolation notices nor
cause the analyzer to be disabled.
o The event engine no longer raises protocol_violation events for
TCP connections which had gaps, as these have proven too unreliable.
(Note that, ideally, the *analyzers* should avoid reporting
protocol_violations when they can't reliably parse a connection
anymore after a gap; but many don't.)
- A set of new script functions provide support for incrementally computing
MD5 checksums (Seth Hall).
md5_hash_init(index: any): bool
Initializes an incremental hashing instance. "index" is
a value of arbitrary type, used to identify this particular
instance (you can have multiple concurrent instances by
using different index values). Returns T on success,
F on failure (such as the index is already in use).
md5_hash_update(index: any, data: string): bool
For the given hashing instance, updates the hash
based on the given data. Returns T on success, F on
failure (such as the index has not been initialized).
md5_hash_finish(index: any): string
Returns the MD5-printable hash for the given index
and terminates the instance, or the string "" if the
index was not active.
- Bro now supports a believed-to-be-robust mechanism for estimating the
proportion of traffic that it failed to capture ("measurement drops"),
which can arise due to overload in either Bro itself, the kernel's
packet filter, or problems with the link tapping mechanism (Vern Paxson).
The event engine can generate estimates for either live traffic or what
was previously recorded in a trace file, though traces subject to some
forms of selective omission (such as skipping over parts of a connection
to reduce storage) can lead to erroneous values.
The estimates are based on observing gaps in TCP data streams, and
come in two forms: the rate at which such gaps appear, and the relative
volume of data missing due to the gaps. (We've found however that the
volume-based estimator is not robust due to occasional packets with
incorrect sequence numbers, so this estimator is off by default.)
The easy way to get the estimates is to load capture-loss.bro.
By default, it generates a CaptureLossSummary notice upon Bro's exit,
which can look like:
1130222759.344066 CaptureLossSummary estimated rate = 0.00089124 / 0.000970997 (events/bytes)
If the estimated loss is none, however, it suppresses this notice,
unless you redef CaptureLoss::summary_if_none to T.
You can also get finer-grained access by defining a "gap_report"
event handler and redef'ing gap_report_freq to a non-zero interval
(such as "10 sec"). This event allows you to pinpoint regions in
time that exhibit significant capture loss. See capture-loss.bro
for an example of a handler for this event.
Finally, these changes include a number of fixes to Bro's
ack_above_hole/content_gap analysis, which is now significantly
- GeoIP support now supports ASN lookups via the built-in
function lookup_asn(a: addr): count (Scott Campbell and Seth Hall).
- The GeoIP built-in's lookup_location() and lookup_asn() now
support IPv6 (Seth Hall). Note, the current GeoIP distribution
doesn't include any IPv6 databases, so for now these won't succeed,
but the hooks are in place for when databases become available.
- lookup_location() now falls back back to the country database if
the city database isn't available (Seth Hall).
- The new SuccessfulPasswordGuessing Notice is generated when a host
has been seen attempting password guessing (currently only for FTP
sessions) and then successfully logs in (Royal Chan). You can control the
threshold for such reports in terms of how many attempts the host must
have made by redef'ing the variable password_guessing_success_threshhold,
which defaults to 20.
- The new script http-detect-passwd.bro analyzes the Web items returned
for fetches that appear to be accessing the passwd file (Akhil Dhar).
It generates a PasswordFullFetch Notice if it appears that the item
includes a full password file, and PasswordShadowFetch if it looks like
a shadowed password file.
- The new built-in
system_env(cmd: string, env: table[string] of string)
works like system(), but puts the table entries into the environment
before invoking the command (Robin Sommer). Each <index> in the table
creates an environment variable of the form "BRO_ARG_<index>", whose
value is the corresponding table entry.
- The new script function
execute_with_notice(cmd: string, notice_info)
executes "cmd" with an environment containing the fields of the
notice_info, i.e., the information associated with a Notice (Robin Sommer).
Per the new system_env() function above, the environment variables appear
as "BRO_ARG_<tag>", where <tag> is the field tag as it appears in
notice.log when you enable use_tagging.
- The new built-in enable_raw_output(file) acts the same as
the attribute &raw_output (Seth Hall).
- The new built-in file_opened(f: file) event is generated any time Bro
opens a script-level file (Justin Azoff). You can use this, for example,
if you want to ensure that a given file has a prelude in it such as
human-readable headers, even when the file is rotated.
- The notice_info record has a new field
aux: table[string] of string &optional
which you can use for information specific to a given type of notice
(Robin Sommer). Entries in $aux appear as "aux_<index>" tags in notice.log.
- Another new notice_info record field is the boolean do_alarm (default=T),
which, if set to F, overides a notice action otherwise specifying to
generate an alarm (Robin Sommer). In other words, if do_alarm is F, no
alarm will be generated independent of the notice action.
This is a work-around for the fact that we can't specify more than one
action. In particular, we couldn't NOTICE_DROP but then *not* alarm,
which we now can by returning NOTICE_DROP yet setting do_alarm to F.
- The notice_info record field $dropped now appears in the tagged output
format if true (Robin Sommer).
- NOTICEs relating to scan detection now no longer include the connection
that triggered the notice, as it really doesn't contain any useful
information, given that the particular trigger simply depends on the
detection algorithm and its parameters (Robin Sommer). However, we do
explicitly set $p (port number) in the notice, and also $n with the
number of attempts.
- drop.bro now hardwires a Catch-and-Release redrop after seeing one
connection from a previously-dropped-but-already-released host
- drop.bro now provides some new hooks (Robin Sommer):
event address_dropped(a: addr)
Generated when an address has been dropped.
event address_restored(a: addr)
Generated when connectivity to an address has been restored,
such as using the Catch-and-Release mechanism.
event address_cleared(a: addr)
Generated when an address that was dropped in the past is
no longer being monitored looking for new connections
(as part of the Catch-and-Release mechanism).
- The new built-in function
hexdump(data_str: string) : string
returns a hex dump representation of the given input data (Christian
Kreibich). The dump renders 16 bytes per line, with hex on the left and
ASCII (where printable) on the right.
- Bro's notion of when a TCP connection begins now dastes to the first
instance of an initial SYN packet seen, rather than the last (Gregor Maier).
- The Time Machine script tm-contents.bro now generates
event contents_saved: event(c: connection, orig_file: string,
when the content of a connection has been completely saved to disk
- The mime.bro script now exports the MIME header callback table, and also
marks it as &redef'able so you can modify its entries (Matthias Vallentin).
The mime_log file is also now exported.
- A new signature file, policy/sigs/http-bots.sig, contains signatures
to detect some of the current HTTP based controlled bot families (Seth Hall).
- The signature engine's HTTP pattern matching has been fixed (Seth Hall)
to align with the documentation at:
In particular, the content condition "http" is now referred to as
"http-request" (though "http" still works for backward compatibility),
"http-request-header" and "http-reply-header" now provide access to
headers seen in only one direction, and similarly for "http-request-body"
and "http-reply-body". (This latter is still accessible as "http-body"
for backwards compatibility.)
- The new script variable max_remote_events_processed: count (default 10)
sets a limit on the number of remote events processed in each round,
before tending to other inputs (Robin Sommer).
- If you set the new script variable dump_used_event_handlers to T,
then on startup Bro dumps out all of the event handlers that the
loaded set of scripts can invoke (Matthias Vallenti).
- Summaries for DNS PTR scanning now use a separate Notice,
DNS_PTR_Scan_Summary, rather than overloading DNS_PTR_Scan (Robin Sommer).
- scan.bro now provides a table skip_dest_server_ports: set[addr, port]
which lists servers (defined as an address and a port) excluded from
scan detection computations (Craig Leres and Jay Krous).
- When redefining values on the command line directly (using var=value),
quotation marks are now implicit only if "var" is a variable of type
string (Christian Kreibich). This allows other string-like values
(such as enum's) to be passed as well.
- scan.bro now explicitly loads conn.bro so that it can itself
be loaded independently (Robin Sommer).
- login.bro depends on scan.bro (because of tracking authentication
"scans"), so now it explicitly loads it (Vern Paxson).
- UDP_datagram_length_mismatch is now by default flagged just once per
originating host rather than once per connection, as it can generate
tons of messages (Vern Paxson).
- Removed now-long-boring flagging of access to Solaris "listen"
service as "hot" (Vern Paxson).
- Removal of libedit, since libreadline provides similar functionality
- Added scripts missing from distribution: dce.bro, ncp.bro, and smb.bro
- ssh.bro now exports ssh_ports (Seth Hall)
- A number of improvements to inter-Bro communication (Robin Sommer).
(1) Remote communication now no longer includes location information for
serialized objects; that removes quite a bit of redundacy from the network
(2) The new option 'remote_check_sync_consistency" disables the cross-check
on the receiving side of &synchronized state of whether the current value
of a variable has the value expected by the sender. Transmitting the
original values in addition to the updates generates quite a bit CPU &
network load in some cases (in particular, a table of tables). The default
for remote_check_sync_consistency is off, and so far that in particular
seems to reduce the proxy's load quite a bit.
(3) Complete overhaul of the internal caching of serialized objects. The
objective of the caching is avoid retransmitting already sent values over
and over again. It turns out, however, that some objects are very stable
and hardly change or get replaced (e.g., Bro types); while other change
all the time and are hardly reused some time later (e.g., Vals). Now
we maintain *two* caches independently for these types of objects; one
with a low turn-over one and another with a high one. This should reduce
CPU load on both sender and receiver sides.
The new scheme is only used if both communicating Bros support it; with
older Bros, as well as with Broccoli, we continue using the old scheme.
- Some reworking of remote printing (Robin Sommer), as follows. Bro now
uses a new interprocess message rather than print_hook events, to better
manage buffering and associated load (these can produce failures depending
on system configuration; see remote.log). A number of timeouts and
buffer sizes have been tuned. Internally, EINTR errors are now treated
separately from EAGAIN. Finally, even with remote_check_sync_consistency=F,
one type of consistency check was still being done; this is no longer
- The DNS analyzer now generates events (dns_query_reply/dns_rejected)
for replies with zero questions (Robin Sommer).
- Perftools support for incompatible changes in the 1.0 API (Robin Sommer).
- Rearranged (generally reducing, though not always) some state timeouts
associated with scan detection (Robin Sommer). In addition, when a
scanning address crosses ignore_scanners_threshold (meaning that it will
be ignored from now on anyway), it gets discarded from all state-tracking
tables. Finally, the ignore_scanners_threshold now applies all kinds
of scans, not just address scans.
- Substantial Broccoli updates, including a new initialization requirement
that breaks backward compatibility, support for enqueueing serialized
event data for transmission, and OpenSSL threadsafe initialization.
See aux/broccoli/ChangeLog for details (Christian Kreibich, Robin
Sommer, and Matthias Vallentin).
- Broccoli hashtable optimisation. See aux/broccoli/ChangeLog for
details (Christian Kreibich & Matthias Vallentin).
- Broccoli memory leak fixed, see aux/broccoli/ChangeLog for details
- Broccoli: updates to bropipe tool (Steve Chan and Robin Sommer).
- Bug fixes for Broccoli Python bindings (Robin Sommer and Matthias Vallentin).
- Fixed nasty bug due to module scoping that completely kept stepping-stone
detection from working (Vern Paxson).
- A serious bug in the packet sorter has been fixed (Robin Sommer).
- Bug fix for extra NULs getting embedded in escaped strings (Seth Hall).
- Bug fix for HTTP messages that use "Connection: close" rather than length
headers, which yielded erroneous reassembled messages with \r\n's when
only \n's were present (Bernhard Ager).
- Fix for reporting on ICMP flows that are expired from the flow table
(Vern Paxson). Previously there was a race condition if the flow
was flushed prior to its summary timer expiring.
- The -l option (list the scripts that Bro loads) now correctly prints
scripts loaded by the prefix mechanism, and uses indentation to indicate
the load hierarchy (Robin Sommer).
- A bug has been fixed (really, worked around) in drop.bro that prevented
dropped addresses from being properly restored (Robin Sommer).
- Fixes for deadlocking problems in the Broccoli protocol. See
aux/broccoli/ChangeLog for details (Christian Kreibich & Robin Sommer).
- Bug fix for DNS analyzer on 64-bit machines (Gregor Maier).
- Bug fix for asynchronous DNS lookups to prevent some successful lookups
being reported as timed out (Robin Sommer).
- Bug fix for tracking line numbers associated with compound statements
- Fix for a rare condition in which the main Bro process couldn't kill
its child process (Robin Sommer).
- Fix for file rotation when the underlying file is deleted before the
timer expires (Robin Sommer).
- Fix for potential crash when communication connections break down,
and also for releasing cached objects (Robin Sommer).
- Fix for default table entries computed by function invocation to not
cache previous results (Robin Sommer).
- Fix for Bro's internal DNS resolution (Scott Campbell and Robin Sommer).
- Portability fix for DAG packet capture (Gregor Maier).
- Portability fix for --enable-brov6 (Robin Sommer).
- Portability fixes for FreeBSD (Vern Paxson).
- A work around for new_packet() crashing on IPv6 packets (Vern Paxson).
For now, IPv6 packets are skipped. Also, for fragments the event handler
is now only called for the fully reassembled packet.
- The new configuration option --disable-nbdns supports disabling non-blocking
DNS at configure time (Sean McCreary). Note, there are some known problems
with it in some environments.
- A number of configuration fixes and enhancements (Christian Kreibich
and Robin Sommer).
- Consistency nit for the configuration process (Seth Hall).
- A number of reference-counting and other memory management fixes
- Bug fix for inter-Bro communication lockup (Seth Hall and Robin Sommer).
- Bug fix for computing TCP payload length in new_packet event (Lothar Braun).
- Bug fix for sending boolean True values via Broccoli (Seth Hall).
- make distcheck fix to clean up .bif.bro files (Christian Kreibich).
- Bug fix for DPD's recognition of SSLv2 connections (Seth Hall).
- Bug fix for &default for tables indexed by subnets (Seth Hall).
- A bug has been fixed that could crash Bro when you called get_event_peer()
after a remote connection had already disppeared (Robin Sommer).
- Introduced a work-around for crashes that occur when Bro exits
due to handling a signal (Robin Sommer).
- Bug fix for checkpoint.bro - don't schedule timers for times that
aren't actually in the future (Robin Sommer).
- Hostname formatting fix for anon.bro (Fabian Schneider).
- Bug fix for redundant .log extension in Time Machine log file
(reported by CS Lee).
- Removed now-outdated special-casing of Linux reporting of packet filter
statistics (Peter Wurzinger and Robin Sommer).
- A number of memory leaks fixed (Robin Sommer).
- Addressed warnings from newer versions of g++ (Robin Sommer and Vern Paxson).
- Fixed an invocation issue in the ca-create script that prevented it from
working with recent OpenSSL versions (Craig Leres & Christian Kreibich).
- Comment fixed in drop-adapt (Justin Azoff).
- Duplicate code removed from Val (Seth Hall).
More information about the Bro