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BinPAC SSH analyzer basic functionality.
This commit is contained in:
Vlad Grigorescu
parent
9d6c8769ea
commit
78b5f6b94b
12 changed files with 465 additions and 301 deletions
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Support for Secure Shell (SSH) protocol analysis.
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@ -1,3 +1,3 @@
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# Generated by binpac_quickstart
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@load ./main
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@load-sigs ./dpd.sig
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@ -1,66 +1,31 @@
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##! Base SSH analysis script. The heuristic to blindly determine success or
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##! failure for SSH connections is implemented here. At this time, it only
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##! uses the size of the data being returned from the server to make the
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##! heuristic determination about success of the connection.
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##! Requires that :bro:id:`use_conn_size_analyzer` is set to T! The heuristic
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##! is not attempted if the connection size analyzer isn't enabled.
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##! Implements base functionality for SSH analysis. Generates the ssh.log file.
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@load base/protocols/conn
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@load base/frameworks/notice
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@load base/utils/site
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@load base/utils/thresholds
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@load base/utils/conn-ids
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@load base/utils/directions-and-hosts
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# Generated by binpac_quickstart
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module SSH;
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export {
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## The SSH protocol logging stream identifier.
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redef enum Log::ID += { LOG };
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type Info: record {
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## Time when the SSH connection began.
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ts: time &log;
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## Timestamp for when the event happened.
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ts: time &log;
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## Unique ID for the connection.
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uid: string &log;
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uid: string &log;
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## The connection's 4-tuple of endpoint addresses/ports.
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id: conn_id &log;
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## Indicates if the login was heuristically guessed to be
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## "success", "failure", or "undetermined".
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status: string &log &default="undetermined";
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## Direction of the connection. If the client was a local host
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## logging into an external host, this would be OUTBOUND. INBOUND
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## would be set for the opposite situation.
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# TODO: handle local-local and remote-remote better.
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direction: Direction &log &optional;
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## Software string from the client.
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client: string &log &optional;
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## Software string from the server.
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server: string &log &optional;
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## Indicate if the SSH session is done being watched.
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done: bool &default=F;
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id: conn_id &log;
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## The client's version string
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client: string &log &optional;
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## The server's version string
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server: string &log &optional;
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## Auth result
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result: string &log &optional;
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## Auth method
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method: string &log &optional;
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};
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## The size in bytes of data sent by the server at which the SSH
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## connection is presumed to be successful.
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const authentication_data_size = 4000 &redef;
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## If true, we tell the event engine to not look at further data
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## packets after the initial SSH handshake. Helps with performance
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## (especially with large file transfers) but precludes some
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## kinds of analyses.
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const skip_processing_after_detection = F &redef;
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## Event that is generated when the heuristic thinks that a login
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## was successful.
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global heuristic_successful_login: event(c: connection);
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## Event that is generated when the heuristic thinks that a login
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## failed.
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global heuristic_failed_login: event(c: connection);
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## Event that can be handled to access the :bro:type:`SSH::Info`
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## record as it is sent on to the logging framework.
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## Event that can be handled to access the SSH record as it is sent on
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## to the loggin framework.
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global log_ssh: event(rec: Info);
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}
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@ -69,136 +34,55 @@ redef record connection += {
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};
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const ports = { 22/tcp };
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redef likely_server_ports += { ports };
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event bro_init() &priority=5
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{
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{
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Log::create_stream(SSH::LOG, [$columns=Info, $ev=log_ssh]);
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Analyzer::register_for_ports(Analyzer::ANALYZER_SSH, ports);
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}
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function set_session(c: connection)
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{
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if ( ! c?$ssh )
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{
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local info: Info;
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info$ts=network_time();
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info$uid=c$uid;
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info$id=c$id;
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c$ssh = info;
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}
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}
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function check_ssh_connection(c: connection, done: bool)
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event ssh_version(c: connection, is_orig: bool, version: string)
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{
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# If already done watching this connection, just return.
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if ( c$ssh$done )
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return;
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if ( done )
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if ( !c?$ssh )
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{
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# If this connection is done, then we can look to see if
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# this matches the conditions for a failed login. Failed
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# logins are only detected at connection state removal.
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if ( # Require originators and responders to have sent at least 50 bytes.
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c$orig$size > 50 && c$resp$size > 50 &&
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# Responders must be below 4000 bytes.
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c$resp$size < authentication_data_size &&
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# Responder must have sent fewer than 40 packets.
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c$resp$num_pkts < 40 &&
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# If there was a content gap we can't reliably do this heuristic.
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c?$conn && c$conn$missed_bytes == 0 )# &&
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# Only "normal" connections can count.
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#c$conn?$conn_state && c$conn$conn_state in valid_states )
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{
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c$ssh$status = "failure";
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event SSH::heuristic_failed_login(c);
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}
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if ( c$resp$size >= authentication_data_size )
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{
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c$ssh$status = "success";
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event SSH::heuristic_successful_login(c);
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}
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local s: SSH::Info;
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s$ts = network_time();
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s$uid = c$uid;
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s$id = c$id;
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c$ssh = s;
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}
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if ( is_orig )
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c$ssh$client = version;
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else
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{
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# If this connection is still being tracked, then it's possible
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# to watch for it to be a successful connection.
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if ( c$resp$size >= authentication_data_size )
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{
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c$ssh$status = "success";
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event SSH::heuristic_successful_login(c);
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}
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else
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# This connection must be tracked longer. Let the scheduled
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# check happen again.
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return;
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}
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# Set the direction for the log.
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c$ssh$direction = Site::is_local_addr(c$id$orig_h) ? OUTBOUND : INBOUND;
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# Set the "done" flag to prevent the watching event from rescheduling
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# after detection is done.
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c$ssh$done=T;
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if ( skip_processing_after_detection )
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{
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# Stop watching this connection, we don't care about it anymore.
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skip_further_processing(c$id);
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set_record_packets(c$id, F);
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}
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c$ssh$server = version;
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# print c$ssh;
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}
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event heuristic_successful_login(c: connection) &priority=-5
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event ssh_auth_successful(c: connection, method: string)
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{
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Log::write(SSH::LOG, c$ssh);
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}
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event heuristic_failed_login(c: connection) &priority=-5
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{
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Log::write(SSH::LOG, c$ssh);
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}
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event connection_state_remove(c: connection) &priority=-5
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{
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if ( c?$ssh )
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{
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check_ssh_connection(c, T);
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if ( c$ssh$status == "undetermined" )
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Log::write(SSH::LOG, c$ssh);
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}
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}
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event ssh_watcher(c: connection)
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{
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local id = c$id;
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# don't go any further if this connection is gone already!
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if ( ! connection_exists(id) )
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if ( !c?$ssh )
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return;
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lookup_connection(c$id);
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check_ssh_connection(c, F);
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if ( ! c$ssh$done )
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schedule +15secs { ssh_watcher(c) };
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c$ssh$result = "success";
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c$ssh$method = method;
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Log::write(SSH::LOG, c$ssh);
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}
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event ssh_server_version(c: connection, version: string) &priority=5
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event ssh_auth_failed(c: connection, method: string)
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{
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set_session(c);
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c$ssh$server = version;
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if ( !c?$ssh )
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return;
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c$ssh$result = "failure";
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c$ssh$method = method;
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Log::write(SSH::LOG, c$ssh);
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}
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event ssh_client_version(c: connection, version: string) &priority=5
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event connection_closed(c: connection)
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{
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set_session(c);
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c$ssh$client = version;
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# The heuristic detection for SSH relies on the ConnSize analyzer.
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# Don't do the heuristics if it's disabled.
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if ( use_conn_size_analyzer )
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schedule +15secs { ssh_watcher(c) };
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}
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if ( c?$ssh && !c$ssh?$result )
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{
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c$ssh$result = "unknown";
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c$ssh$method = "unknown";
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Log::write(SSH::LOG, c$ssh);
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}
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}
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