This document summarizes the most important changes in the current Bro release. For a complete list of changes, see the ``CHANGES`` file (note that submodules, such as BroControl and Broccoli, come with their own CHANGES.) Bro 2.2 (Work In Progress) ========================== New Functionality ----------------- - GPRS Tunnelling Protocol (GTPv1) decapsulation. - GridFTP support. TODO: Extend. - Modbus support. TODO: Extend. - DNP3 support. TODO: Extend. - ssl.log now also records the subject client and issuer certificates. - Hooks: TODO: Briefly summarize the documention from doc/scripts/builtins.rst here. - The ASCII writer can now output CSV files on a per filter basis. - Bro's language now has a working "switch" statement that generally behaves like C-style switches except case labels can be comprised of multiple literal constants delimited by commas. Only atomic types are allowed for now. Case label bodies that don't execute a "return" or "break" statement will fall through to subsequent cases. A default case label is allowed. - Bro's language now has a new set of types "opaque of X". Opaque values can be passed around like other values but they can only be manipulated with BiF functions, not with other operators. Currently, the following opaque types are supported: - opaque of md5 - opaque of sha1 - opaque of sha256 - opaquey of entropy. They go along with the corrsponding BiF functions md5_*, sha1_*, sha256_*, and entropy_*, respectively. Note that these functions have changed their signatures to work with opaques types rather than global state as it was before. - The scripting language now supports a constructing sets, tables, vectors, and records by name:: type MyRecordType: record { c: count; s: string &optional; }; global r: MyRecordType = record($c = 7); type MySet: set[MyRec]; global s = MySet([$c=1], [$c=2]); - Strings now support the subscript operator to extract individual characters and substrings (e.g., s[4], s[1,5]). The index expression can take up to two indices for the start and end index of the substring to return (e.g. "mystring[1,3]"). - Functions now support default parameters, e.g.: global foo: function(s: string, t: string &default="abc", u: count &default=0); - Scripts can now use two new "magic constants" @DIR and @FILENAME that expand to the directory path of the current script and just the script file name without path, respectively. (Jon Siwek) - The new file analysis framework moves most of the processing of file content from script-land into the core, where it belongs. See doc/file-analysis.rst for more information. Much of this is an internal change, but the framework also comes with the following user-visibible functionality (some of that was already available before, but done differently): [TODO: Update with changes from 984e9793db56.] - A binary input reader interfaces the input framework with file analysis, allowing to inject files on disk into Bro's processing. - Supports for analyzing data transfereed via HTTP range requests. - HTTP: * Identify MIME type of message. * Extract message to disk. * Compute MD5 for messages. - SMTP: * Identify MIME type of message. * Extract message to disk. * Compute MD5 for messages. * Provide access to start of entity data. - FTP data transfers: Identify MIME type; record to disk. - IRC DCC transfers: Record to disk. - New packet filter framework supports BPF-based load-balancing, shunting, and sampling; plus plugin support to customize filters dynamically. - Bro now provides Bloom filters of two kinds: basic Bloom filters supporting membership tests, and counting Bloom filters that track the frequency of elements. The corresponding functions are: bloomfilter_basic_init(fp: double, capacity: count, name: string &default=""): opaque of bloomfilter bloomfilter_basic_init2(k: count, cells: count, name: string &default=""): opaque of bloomfilter bloomfilter_counting_init(k: count, cells: count, max: count, name: string &default=""): opaque of bloomfilter bloomfilter_add(bf: opaque of bloomfilter, x: any) bloomfilter_lookup(bf: opaque of bloomfilter, x: any): count bloomfilter_merge(bf1: opaque of bloomfilter, bf2: opaque of bloomfilter): opaque of bloomfilter bloomfilter_clear(bf: opaque of bloomfilter) See for full documentation. - Bro now provides a probabilistic data structure for computing "top k" elements. The corresponding functions are: topk_init(size: count): opaque of topk topk_add(handle: opaque of topk, value: any) topk_get_top(handle: opaque of topk, k: count) topk_count(handle: opaque of topk, value: any): count topk_epsilon(handle: opaque of topk, value: any): count topk_size(handle: opaque of topk): count topk_sum(handle: opaque of topk): count topk_merge(handle1: opaque of topk, handle2: opaque of topk) topk_merge_prune(handle1: opaque of topk, handle2: opaque of topk) See for full documentation. - base/utils/exec.bro provides a module to start external processes asynchronously and retrieve their output on termination. base/utils/dir.bro uses it to monitor a directory for changes, and base/utils/active-http.bro for providing an interface for querying remote web servers. - Summary statistics framework. [Extend] - A number of new applications build on top of the summary statistics framework: * Scan detection: Detectors for port and address scans return. See policy/misc/scan.bro. * Tracerouter detector: policy/misc/detect-traceroute * Web application detection/measurement: policy/misc/app-metrics.bro * FTP brute-forcing detector: policy/protocols/ftp/detect-bruteforcing.bro * HTTP-based SQL injection detector: policy/protocols/http/detect-sqli.bro (existed before, but now ported to the new framework) * SSH brute-forcing detector feeding the intelligence framework: policy/protocols/ssh/detect-bruteforcing.bro Changed Functionality --------------------- - We removed the following, already deprecated, functionality: * Scripting language: - &disable_print_hook attribute. * BiF functions: - parse_dotted_addr(), dump_config(), make_connection_persistent(), generate_idmef(), split_complete() - md5_*, sha1_*, sha256_*, and entropy_* have all changed their signatures to work with opaque types (see above). - Removed a now unused argument from "do_split" helper function. - "this" is no longer a reserved keyword. - The Input Framework's update_finished event has been renamed to end_of_data. It will now not only fire after table-reads have been completed, but also after the last event of a whole-file-read (or whole-db-read, etc.). - Renamed the option defining the frequency of alarm summary mails to 'Logging::default_alarm_mail_interval'. When using BroControl, the value can now be set with the new broctl.cfg option "MailAlarmsInterval". - We have completely reworded the "notice_policy" mechanism. It now no linger uses a record of policy items but a "hook", a new language element that's roughly equivalent to a function with multiple bodies. The documentation [TODO: insert link] describes how to use the new notice policy. For existing code, the two main changes are: - What used to be a "redef" of "Notice::policy" now becomes a hook implementation. Example: Old:: redef Notice::policy += { [$pred(n: Notice::Info) = { return n$note == SSH::Login && n$id$resp_h == 10.0.0.1; }, $action = Notice::ACTION_EMAIL] }; New:: hook Notice::policy(n: Notice::Info) { if ( n$note == SSH::Login && n$id$resp_h == 10.0.0.1 ) add n$actions[Notice::ACTION_EMAIL]; } - notice() is now likewise a hook, no longer an event. If you have handlers for that event, you'll likely just need to change the type accordingly. Example: Old:: event notice(n: Notice::Info) { ... } New:: hook notice(n: Notice::Info) { ... } - The notice_policy.log is gone. That's a result of the new notice policy setup. - Removed the byte_len() and length() bif functions. Use the ``|...|`` operator instead. - The SSH::Login notice has been superseded by an corresponding intelligence framework observation (SSH::SUCCESSFUL_LOGIN). - PacketFilter::all_packets has been replaced with PacketFilter::enable_auto_protocol_capture_filters. - We removed the BitTorrent DPD signatures pending further updates to that analyzer. Bro 2.1 ======= New Functionality ----------------- - Bro now comes with extensive IPv6 support. Past versions offered only basic IPv6 functionality that was rarely used in practice as it had to be enabled explicitly. IPv6 support is now fully integrated into all parts of Bro including protocol analysis and the scripting language. It's on by default and no longer requires any special configuration. Some of the most significant enhancements include support for IPv6 fragment reassembly, support for following IPv6 extension header chains, and support for tunnel decapsulation (6to4 and Teredo). The DNS analyzer now handles AAAA records properly, and DNS lookups that Bro itself performs now include AAAA queries, so that, for example, the result returned by script-level lookups is a set that can contain both IPv4 and IPv6 addresses. Support for the most common ICMPv6 message types has been added. Also, the FTP EPSV and EPRT commands are now handled properly. Internally, the way IP addresses are stored has been improved, so Bro can handle both IPv4 and IPv6 by default without any special configuration. In addition to Bro itself, the other Bro components have also been made IPv6-aware by default. In particular, significant changes were made to trace-summary, PySubnetTree, and Broccoli to support IPv6. - Bro now decapsulates tunnels via its new tunnel framework located in scripts/base/frameworks/tunnels. It currently supports Teredo, AYIYA, IP-in-IP (both IPv4 and IPv6), and SOCKS. For all these, it logs the outer tunnel connections in both conn.log and tunnel.log, and then proceeds to analyze the inner payload as if it were not tunneled, including also logging that session in conn.log. For SOCKS, it generates a new socks.log in addition with more information. - Bro now features a flexible input framework that allows users to integrate external information in real-time into Bro while it's processing network traffic. The most direct use-case at the moment is reading data from ASCII files into Bro tables, with updates picked up automatically when the file changes during runtime. See doc/input.rst for more information. Internally, the input framework is structured around the notion of "reader plugins" that make it easy to interface to different data sources. We will add more in the future. - BroControl now has built-in support for host-based load-balancing when using either PF_RING, Myricom cards, or individual interfaces. Instead of adding a separate worker entry in node.cfg for each Bro worker process on each worker host, it is now possible to just specify the number of worker processes on each host and BroControl configures everything correctly (including any neccessary enviroment variables for the balancers). This change adds three new keywords to the node.cfg file (to be used with worker entries): lb_procs (specifies number of workers on a host), lb_method (specifies what type of load balancing to use: pf_ring, myricom, or interfaces), and lb_interfaces (used only with "lb_method=interfaces" to specify which interfaces to load-balance on). - Bro's default ASCII log format is not exactly the most efficient way for storing and searching large volumes of data. An alternatives, Bro now comes with experimental support for two alternative output formats: * DataSeries: an efficient binary format for recording structured bulk data. DataSeries is developed and maintained at HP Labs. See doc/logging-dataseries for more information. * ElasticSearch: a distributed RESTful, storage engine and search engine built on top of Apache Lucene. It scales very well, both for distributed indexing and distributed searching. See doc/logging-elasticsearch.rst for more information. Note that at this point, we consider Bro's support for these two formats as prototypes for collecting experience with alternative outputs. We do not yet recommend them for production (but welcome feedback!) Changed Functionality --------------------- The following summarizes the most important differences in existing functionality. Note that this list is not complete, see CHANGES for the full set. - Changes in dependencies: * Bro now requires CMake >= 2.6.3. * On Linux, Bro now links in tcmalloc (part of Google perftools) if found at configure time. Doing so can significantly improve memory and CPU use. On the other platforms, the new configure option --enable-perftools can be used to enable linking to tcmalloc. (Note that perftools's support for non-Linux platforms may be less reliable). - The configure switch --enable-brov6 is gone. - DNS name lookups performed by Bro now also query AAAA records. The results of the A and AAAA queries for a given hostname are combined such that at the scripting layer, the name resolution can yield a set with both IPv4 and IPv6 addresses. - The connection compressor was already deprecated in 2.0 and has now been removed from the code base. - We removed the "match" statement, which was no longer used by any of the default scripts, nor was it likely to be used by anybody anytime soon. With that, "match" and "using" are no longer reserved keywords. - The syntax for IPv6 literals changed from "2607:f8b0:4009:802::1012" to "[2607:f8b0:4009:802::1012]". When an IP address variable or IP address literal is enclosed in pipes (for example, ``|[fe80::db15]|``) the result is now the size of the address in bits (32 for IPv4 and 128 for IPv6). - Bro now spawns threads for doing its logging. From a user's perspective not much should change, except that the OS may now show a bunch of Bro threads. - We renamed the configure option --enable-perftools to --enable-perftools-debug to indicate that the switch is only relevant for debugging the heap. - Bro's ICMP analyzer now handles both IPv4 and IPv6 messages with a joint set of events. The `icmp_conn` record got a new boolean field 'v6' that indicates whether the ICMP message is v4 or v6. - Log postprocessor scripts get an additional argument indicating the type of the log writer in use (e.g., "ascii"). - BroControl's make-archive-name script also receives the writer type, but as its 2nd(!) argument. If you're using a custom version of that script, you need to adapt it. See the shipped version for details. - Signature files can now be loaded via the new "@load-sigs" directive. In contrast to the existing (and still supported) signature_files constant, this can be used to load signatures relative to the current script (e.g., "@load-sigs ./foo.sig"). - The options "tunnel_port" and "parse_udp_tunnels" have been removed. Bro now supports decapsulating tunnels directly for protocols it understands. - ASCII logs now record the time when they were opened/closed at the beginning and end of the file, respectively (wall clock). The options LogAscii::header_prefix and LogAscii::include_header have been renamed to LogAscii::meta_prefix and LogAscii::include_meta, respectively. - The ASCII writers "header_*" options have been renamed to "meta_*" (because there's now also a footer). - Some built-in functions have been removed: "addr_to_count" (use "addr_to_counts" instead), "bro_has_ipv6" (this is no longer relevant because Bro now always supports IPv6), "active_connection" (use "connection_exists" instead), and "connection_record" (use "lookup_connection" instead). - The "NFS3::mode2string" built-in function has been renamed to "file_mode". - Some built-in functions have been changed: "exit" (now takes the exit code as a parameter), "to_port" (now takes a string as parameter instead of a count and transport protocol, but "count_to_port" is still available), "connect" (now takes an additional string parameter specifying the zone of a non-global IPv6 address), and "listen" (now takes three additional parameters to enable listening on IPv6 addresses). - Some Bro script variables have been renamed: "LogAscii::header_prefix" has been renamed to "LogAscii::meta_prefix", "LogAscii::include_header" has been renamed to "LogAscii::include_meta". - Some Bro script variables have been removed: "tunnel_port", "parse_udp_tunnels", "use_connection_compressor", "cc_handle_resets", "cc_handle_only_syns", and "cc_instantiate_on_data". - A couple events have changed: the "icmp_redirect" event now includes the target and destination addresses and any Neighbor Discovery options in the message, and the last parameter of the "dns_AAAA_reply" event has been removed because it was unused. - The format of the ASCII log files has changed very slightly. Two new lines are automatically added, one to record the time when the log was opened, and the other to record the time when the log was closed. - In BroControl, the option (in broctl.cfg) "CFlowAddr" was renamed to "CFlowAddress". Bro 2.0 ======= As the version number jump from 1.5 suggests, Bro 2.0 is a major upgrade and lots of things have changed. Most importantly, we have rewritten almost all of Bro's default scripts from scratch, using quite different structure now and focusing more on operational deployment. The result is a system that works much better "out of the box", even without much initial site-specific configuration. The down-side is that 1.x configurations will need to be adapted to work with the new version. The two rules of thumb are: (1) If you have written your own Bro scripts that do not depend on any of the standard scripts formerly found in ``policy/``, they will most likely just keep working (although you might want to adapt them to use some of the new features, like the new logging framework; see below). (2) If you have custom code that depends on specifics of 1.x default scripts (including most configuration tuning), that is unlikely to work with 2.x. We recommend to start by using just the new scripts first, and then port over any customizations incrementally as necessary (they may be much easier to do now, or even unnecessary). Send mail to the Bro user mailing list if you need help. Below we summarize changes from 1.x to 2.x in more detail. This list isn't complete, see the ``CHANGES`` file in the distribution or :doc:`here ` for the full story. Script Organization ------------------- In versions before 2.0, Bro scripts were all maintained in a flat directory called ``policy/`` in the source tree. This directory is now renamed to ``scripts/`` and contains major subdirectories ``base/``, ``policy/``, and ``site/``, each of which may also be subdivided further. The contents of the new ``scripts/`` directory, like the old/flat ``policy/`` still gets installed under the ``share/bro`` subdirectory of the installation prefix path just like previous versions. For example, if Bro was compiled like ``./configure --prefix=/usr/local/bro && make && make install``, then the script hierarchy can be found in ``/usr/local/bro/share/bro``. The main subdirectories of that hierarchy are as follows: - ``base/`` contains all scripts that are loaded by Bro by default (unless the ``-b`` command line option is used to run Bro in a minimal configuration). Note that is a major conceptual change: rather than not loading anything by default, Bro now uses an extensive set of default scripts out of the box. The scripts under this directory generally either accumulate/log useful state/protocol information for monitored traffic, configure a default/recommended mode of operation, or provide extra Bro scripting-layer functionality that has no significant performance cost. - ``policy/`` contains all scripts that a user will need to explicitly tell Bro to load. These are scripts that implement functionality/analysis that not all users may want to use and may have more significant performance costs. For a new installation, you should go through these and see what appears useful to load. - ``site/`` remains a directory that can be used to store locally developed scripts. It now comes with some preinstalled example scripts that contain recommended default configurations going beyond the ``base/`` setup. E.g. ``local.bro`` loads extra scripts from ``policy/`` and does extra tuning. These files can be customized in place without being overwritten by upgrades/reinstalls, unlike scripts in other directories. With version 2.0, the default ``BROPATH`` is set to automatically search for scripts in ``policy/``, ``site/`` and their parent directory, but **not** ``base/``. Generally, everything under ``base/`` is loaded automatically, but for users of the ``-b`` option, it's important to know that loading a script in that directory requires the extra ``base/`` path qualification. For example, the following two scripts: * ``$PREFIX/share/bro/base/protocols/ssl/main.bro`` * ``$PREFIX/share/bro/policy/protocols/ssl/validate-certs.bro`` are referenced from another Bro script like: .. code:: bro @load base/protocols/ssl/main @load protocols/ssl/validate-certs Notice how ``policy/`` can be omitted as a convenience in the second case. ``@load`` can now also use relative path, e.g., ``@load ../main``. Logging Framework ----------------- - The logs generated by scripts that ship with Bro are entirely redone to use a standardized, machine parsable format via the new logging framework. Generally, the log content has been restructured towards making it more directly useful to operations. Also, several analyzers have been significantly extended and thus now log more information. Take a look at ``ssl.log``. * A particular format change that may be useful to note is that the ``conn.log`` ``service`` field is derived from DPD instead of well-known ports (while that was already possible in 1.5, it was not the default). * Also, ``conn.log`` now reports raw number of packets/bytes per endpoint. - The new logging framework makes it possible to extend, customize, and filter logs very easily. See the :doc:`logging framework ` for more information on usage. - A common pattern found in the new scripts is to store logging stream records for protocols inside the ``connection`` records so that state can be collected until enough is seen to log a coherent unit of information regarding the activity of that connection. This state is now frequently seen/accessible in event handlers, for example, like ``c$`` where ```` is replaced by the name of the protocol. This field is added to the ``connection`` record by ``redef``'ing it in a ``base/protocols//main.bro`` script. - The logging code has been rewritten internally, with script-level interface and output backend now clearly separated. While ASCII logging is still the default, we will add further output types in the future (binary format, direct database logging). Notice Framework ---------------- The way users interact with "notices" has changed significantly in order to make it easier to define a site policy and more extensible for adding customized actions. See the :doc:`notice framework `. New Default Settings -------------------- - Dynamic Protocol Detection (DPD) is now enabled/loaded by default. - The default packet filter now examines all packets instead of dynamically building a filter based on which protocol analysis scripts are loaded. See ``PacketFilter::all_packets`` for how to revert to old behavior. API Changes ----------- - The ``@prefixes`` directive works differently now. Any added prefixes are now searched for and loaded *after* all input files have been parsed. After all input files are parsed, Bro searches ``BROPATH`` for prefixed, flattened versions of all of the parsed input files. For example, if ``lcl`` is in ``@prefixes``, and ``site.bro`` is loaded, then a file named ``lcl.site.bro`` that's in ``BROPATH`` would end up being automatically loaded as well. Packages work similarly, e.g. loading ``protocols/http`` means a file named ``lcl.protocols.http.bro`` in ``BROPATH`` gets loaded automatically. - The ``make_addr`` BIF now returns a ``subnet`` versus an ``addr`` Variable Naming --------------- - ``Module`` is more widely used for namespacing. E.g. the new ``site.bro`` exports the ``local_nets`` identifier (among other things) into the ``Site`` module. - Identifiers may have been renamed to conform to new `scripting conventions `_ Removed Functionality --------------------- We have remove a bunch of functionality that was rarely used and/or had not been maintained for a while already: - The ``net`` script data type. - The ``alarm`` statement; use the notice framework instead. - Trace rewriting. - DFA state expiration in regexp engine. - Active mapping. - Native DAG support (may come back eventually) - ClamAV support. - The connection compressor is now disabled by default, and will be removed in the future. BroControl Changes ------------------ BroControl looks pretty much similar to the version coming with Bro 1.x, but has been cleaned up and streamlined significantly internally. BroControl has a new ``process`` command to process a trace on disk offline using a similar configuration to what BroControl installs for live analysis. BroControl now has an extensive plugin interface for adding new commands and options. Note that this is still considered experimental. We have removed the ``analysis`` command, and BroControl currently does not send daily alarm summaries anymore (this may be restored later). Development Infrastructure -------------------------- Bro development has moved from using SVN to Git for revision control. Users that want to use the latest Bro development snapshot by checking it out from the source repositories should see the `development process `_. Note that all the various sub-components now reside in their own repositories. However, the top-level Bro repository includes them as git submodules so it's easy to check them all out simultaneously. Bro now uses `CMake `_ for its build system so that is a new required dependency when building from source. Bro now comes with a growing suite of regression tests in ``testing/``.