mirror of
https://github.com/zeek/zeek.git
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b5af589246
Fixed reference to wrong field name. Added documentation of a function arg. Added a couple references to other parts of the documentation. Explained how not specifying extraction filename results in automatic filename generation. Several other minor clarifications.
368 lines
12 KiB
Text
368 lines
12 KiB
Text
##! An interface for driving the analysis of files, possibly independent of
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##! any network protocol over which they're transported.
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@load base/bif/file_analysis.bif
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@load base/frameworks/analyzer
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@load base/frameworks/logging
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@load base/utils/site
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module Files;
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export {
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redef enum Log::ID += {
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## Logging stream for file analysis.
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LOG
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};
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## A structure which parameterizes a type of file analysis.
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type AnalyzerArgs: record {
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## An event which will be generated for all new file contents,
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## chunk-wise. Used when *tag* (in the
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## :bro:see:`Files::add_analyzer` function) is
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## :bro:see:`Files::ANALYZER_DATA_EVENT`.
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chunk_event: event(f: fa_file, data: string, off: count) &optional;
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## An event which will be generated for all new file contents,
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## stream-wise. Used when *tag* is
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## :bro:see:`Files::ANALYZER_DATA_EVENT`.
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stream_event: event(f: fa_file, data: string) &optional;
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} &redef;
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## Contains all metadata related to the analysis of a given file.
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## For the most part, fields here are derived from ones of the same name
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## in :bro:see:`fa_file`.
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type Info: record {
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## The time when the file was first seen.
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ts: time &log;
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## An identifier associated with a single file.
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fuid: string &log;
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## If this file was transferred over a network
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## connection this should show the host or hosts that
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## the data sourced from.
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tx_hosts: set[addr] &log;
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## If this file was transferred over a network
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## connection this should show the host or hosts that
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## the data traveled to.
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rx_hosts: set[addr] &log;
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## Connection UIDs over which the file was transferred.
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conn_uids: set[string] &log;
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## An identification of the source of the file data. E.g. it
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## may be a network protocol over which it was transferred, or a
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## local file path which was read, or some other input source.
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source: string &log &optional;
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## A value to represent the depth of this file in relation
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## to its source. In SMTP, it is the depth of the MIME
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## attachment on the message. In HTTP, it is the depth of the
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## request within the TCP connection.
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depth: count &default=0 &log;
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## A set of analysis types done during the file analysis.
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analyzers: set[string] &log;
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## A mime type provided by libmagic against the *bof_buffer*
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## field of :bro:see:`fa_file`, or in the cases where no
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## buffering of the beginning of file occurs, an initial
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## guess of the mime type based on the first data seen.
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mime_type: string &log &optional;
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## A filename for the file if one is available from the source
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## for the file. These will frequently come from
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## "Content-Disposition" headers in network protocols.
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filename: string &log &optional;
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## The duration the file was analyzed for.
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duration: interval &log &default=0secs;
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## If the source of this file is a network connection, this field
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## indicates if the data originated from the local network or not as
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## determined by the configured :bro:see:`Site::local_nets`.
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local_orig: bool &log &optional;
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## If the source of this file is a network connection, this field
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## indicates if the file is being sent by the originator of the
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## connection or the responder.
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is_orig: bool &log &optional;
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## Number of bytes provided to the file analysis engine for the file.
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seen_bytes: count &log &default=0;
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## Total number of bytes that are supposed to comprise the full file.
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total_bytes: count &log &optional;
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## The number of bytes in the file stream that were completely missed
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## during the process of analysis e.g. due to dropped packets.
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missing_bytes: count &log &default=0;
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## The number of not all-in-sequence bytes in the file stream that
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## were delivered to file analyzers due to reassembly buffer overflow.
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overflow_bytes: count &log &default=0;
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## Whether the file analysis timed out at least once for the file.
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timedout: bool &log &default=F;
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## Identifier associated with a container file from which this one was
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## extracted as part of the file analysis.
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parent_fuid: string &log &optional;
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} &redef;
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## A table that can be used to disable file analysis completely for
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## any files transferred over given network protocol analyzers.
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const disable: table[Files::Tag] of bool = table() &redef;
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## The salt concatenated to unique file handle strings generated by
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## :bro:see:`get_file_handle` before hashing them in to a file id
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## (the *id* field of :bro:see:`fa_file`).
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## Provided to help mitigate the possibility of manipulating parts of
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## network connections that factor in to the file handle in order to
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## generate two handles that would hash to the same file id.
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const salt = "I recommend changing this." &redef;
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## Sets the *timeout_interval* field of :bro:see:`fa_file`, which is
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## used to determine the length of inactivity that is allowed for a file
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## before internal state related to it is cleaned up. When used within
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## a :bro:see:`file_timeout` handler, the analysis will delay timing out
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## again for the period specified by *t*.
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##
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## f: the file.
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##
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## t: the amount of time the file can remain inactive before discarding.
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##
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## Returns: true if the timeout interval was set, or false if analysis
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## for the file isn't currently active.
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global set_timeout_interval: function(f: fa_file, t: interval): bool;
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## Adds an analyzer to the analysis of a given file.
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##
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## f: the file.
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##
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## tag: the analyzer type.
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##
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## args: any parameters the analyzer takes.
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##
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## Returns: true if the analyzer will be added, or false if analysis
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## for the file isn't currently active or the *args*
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## were invalid for the analyzer type.
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global add_analyzer: function(f: fa_file,
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tag: Files::Tag,
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args: AnalyzerArgs &default=AnalyzerArgs()): bool;
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## Removes an analyzer from the analysis of a given file.
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##
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## f: the file.
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##
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## tag: the analyzer type.
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##
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## args: the analyzer (type and args) to remove.
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##
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## Returns: true if the analyzer will be removed, or false if analysis
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## for the file isn't currently active.
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global remove_analyzer: function(f: fa_file,
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tag: Files::Tag,
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args: AnalyzerArgs &default=AnalyzerArgs()): bool;
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## Stops/ignores any further analysis of a given file.
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##
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## f: the file.
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##
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## Returns: true if analysis for the given file will be ignored for the
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## rest of its contents, or false if analysis for the file
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## isn't currently active.
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global stop: function(f: fa_file): bool;
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## Translates a file analyzer enum value to a string with the
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## analyzer's name.
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##
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## tag: The analyzer tag.
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##
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## Returns: The analyzer name corresponding to the tag.
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global analyzer_name: function(tag: Files::Tag): string;
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## Provides a text description regarding metadata of the file.
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## For example, with HTTP it would return a URL.
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##
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## f: The file to be described.
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##
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## Returns: a text description regarding metadata of the file.
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global describe: function(f: fa_file): string;
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type ProtoRegistration: record {
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## A callback to generate a file handle on demand when
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## one is needed by the core.
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get_file_handle: function(c: connection, is_orig: bool): string;
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## A callback to "describe" a file. In the case of an HTTP
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## transfer the most obvious description would be the URL.
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## It's like an extremely compressed version of the normal log.
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describe: function(f: fa_file): string
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&default=function(f: fa_file): string { return ""; };
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};
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## Register callbacks for protocols that work with the Files framework.
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## The callbacks must uniquely identify a file and each protocol can
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## only have a single callback registered for it.
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##
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## tag: Tag for the protocol analyzer having a callback being registered.
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##
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## reg: A :bro:see:`Files::ProtoRegistration` record.
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##
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## Returns: true if the protocol being registered was not previously registered.
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global register_protocol: function(tag: Analyzer::Tag, reg: ProtoRegistration): bool;
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## Register a callback for file analyzers to use if they need to do some
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## manipulation when they are being added to a file before the core code
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## takes over. This is unlikely to be interesting for users and should
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## only be called by file analyzer authors but is *not required*.
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##
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## tag: Tag for the file analyzer.
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##
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## callback: Function to execute when the given file analyzer is being added.
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global register_analyzer_add_callback: function(tag: Files::Tag, callback: function(f: fa_file, args: AnalyzerArgs));
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## Event that can be handled to access the Info record as it is sent on
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## to the logging framework.
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global log_files: event(rec: Info);
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}
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redef record fa_file += {
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info: Info &optional;
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};
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# Store the callbacks for protocol analyzers that have files.
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global registered_protocols: table[Analyzer::Tag] of ProtoRegistration = table();
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global analyzer_add_callbacks: table[Files::Tag] of function(f: fa_file, args: AnalyzerArgs) = table();
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event bro_init() &priority=5
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{
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Log::create_stream(Files::LOG, [$columns=Info, $ev=log_files]);
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}
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function set_info(f: fa_file)
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{
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if ( ! f?$info )
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{
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local tmp: Info = Info($ts=f$last_active,
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$fuid=f$id);
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f$info = tmp;
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}
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if ( f?$parent_id )
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f$info$parent_fuid = f$parent_id;
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if ( f?$source )
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f$info$source = f$source;
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f$info$duration = f$last_active - f$info$ts;
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f$info$seen_bytes = f$seen_bytes;
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if ( f?$total_bytes )
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f$info$total_bytes = f$total_bytes;
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f$info$missing_bytes = f$missing_bytes;
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f$info$overflow_bytes = f$overflow_bytes;
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if ( f?$is_orig )
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f$info$is_orig = f$is_orig;
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if ( f?$mime_type )
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f$info$mime_type = f$mime_type;
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}
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function set_timeout_interval(f: fa_file, t: interval): bool
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{
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return __set_timeout_interval(f$id, t);
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}
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function add_analyzer(f: fa_file, tag: Files::Tag, args: AnalyzerArgs): bool
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{
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add f$info$analyzers[Files::analyzer_name(tag)];
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if ( tag in analyzer_add_callbacks )
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analyzer_add_callbacks[tag](f, args);
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if ( ! __add_analyzer(f$id, tag, args) )
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{
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Reporter::warning(fmt("Analyzer %s not added successfully to file %s.", tag, f$id));
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return F;
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}
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return T;
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}
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function register_analyzer_add_callback(tag: Files::Tag, callback: function(f: fa_file, args: AnalyzerArgs))
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{
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analyzer_add_callbacks[tag] = callback;
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}
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function remove_analyzer(f: fa_file, tag: Files::Tag, args: AnalyzerArgs): bool
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{
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return __remove_analyzer(f$id, tag, args);
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}
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function stop(f: fa_file): bool
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{
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return __stop(f$id);
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}
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function analyzer_name(tag: Files::Tag): string
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{
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return __analyzer_name(tag);
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}
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event file_new(f: fa_file) &priority=10
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{
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set_info(f);
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}
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event file_over_new_connection(f: fa_file, c: connection, is_orig: bool) &priority=10
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{
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set_info(f);
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add f$info$conn_uids[c$uid];
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local cid = c$id;
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add f$info$tx_hosts[f$is_orig ? cid$orig_h : cid$resp_h];
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if( |Site::local_nets| > 0 )
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f$info$local_orig=Site::is_local_addr(f$is_orig ? cid$orig_h : cid$resp_h);
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add f$info$rx_hosts[f$is_orig ? cid$resp_h : cid$orig_h];
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}
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event file_timeout(f: fa_file) &priority=10
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{
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set_info(f);
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f$info$timedout = T;
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}
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event file_state_remove(f: fa_file) &priority=10
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{
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set_info(f);
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}
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event file_state_remove(f: fa_file) &priority=-10
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{
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Log::write(Files::LOG, f$info);
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}
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function register_protocol(tag: Analyzer::Tag, reg: ProtoRegistration): bool
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{
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local result = (tag !in registered_protocols);
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registered_protocols[tag] = reg;
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return result;
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}
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function describe(f: fa_file): string
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{
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local tag = Analyzer::get_tag(f$source);
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if ( tag !in registered_protocols )
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return "";
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local handler = registered_protocols[tag];
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return handler$describe(f);
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}
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event get_file_handle(tag: Analyzer::Tag, c: connection, is_orig: bool) &priority=5
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{
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if ( tag !in registered_protocols )
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return;
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local handler = registered_protocols[tag];
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set_file_handle(handler$get_file_handle(c, is_orig));
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}
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