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This commit is contained in:
Seth Hall 2013-03-13 22:55:03 -04:00
parent 09cbaa7ccc
commit 8778761c07
30 changed files with 833 additions and 848 deletions
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108
scripts/base/protocols/ssh/main.bro
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@ -17,12 +17,6 @@ export {
## The SSH protocol logging stream identifier.
redef enum Log::ID += { LOG };
redef enum Notice::Type += {
## Indicates that a heuristically detected "successful" SSH
## authentication occurred.
Login
};
type Info: record {
## Time when the SSH connection began.
ts: time &log;
@ -30,9 +24,9 @@ export {
uid: string &log;
## The connection's 4-tuple of endpoint addresses/ports.
id: conn_id &log;
## Indicates if the login was heuristically guessed to be "success"
## or "failure".
status: string &log &optional;
## Indicates if the login was heuristically guessed to be "success",
## "failure", or "undetermined".
status: string &log &default="undetermined";
## Direction of the connection. If the client was a local host
## logging into an external host, this would be OUTBOUND. INBOUND
## would be set for the opposite situation.
@ -54,12 +48,12 @@ export {
## The size in bytes of data sent by the server at which the SSH
## connection is presumed to be successful.
const authentication_data_size = 5500 &redef;
const authentication_data_size = 4000 &redef;
## If true, we tell the event engine to not look at further data
## packets after the initial SSH handshake. Helps with performance
## (especially with large file transfers) but precludes some
## kinds of analyses (e.g., tracking connection size).
## kinds of analyses.
const skip_processing_after_detection = F &redef;
## Event that is generated when the heuristic thinks that a login
@ -104,54 +98,60 @@ function set_session(c: connection)
function check_ssh_connection(c: connection, done: bool)
{
# If done watching this connection, just return.
# If already done watching this connection, just return.
if ( c$ssh$done )
return;
# Make sure conn_size_analyzer is active by checking
# resp$num_bytes_ip. In general it should always be active though.
if ( ! c$resp?$num_bytes_ip )
return;
# Remove the IP and TCP header length from the total size.
# TODO: Fix for IPv6. This whole approach also seems to break in some
# cases where there are more header bytes than num_bytes_ip.
local header_bytes = c$resp$num_pkts*32 + c$resp$num_pkts*20;
local server_bytes = c$resp$num_bytes_ip;
if ( server_bytes >= header_bytes )
server_bytes = server_bytes - header_bytes;
else
server_bytes = c$resp$size;
# If this is still a live connection and the byte count has not crossed
# the threshold, just return and let the rescheduled check happen later.
if ( ! done && server_bytes < authentication_data_size )
return;
# Make sure the server has sent back more than 50 bytes to filter out
# hosts that are just port scanning. Nothing is ever logged if the server
# doesn't send back at least 50 bytes.
if ( server_bytes < 50 )
return;
c$ssh$direction = Site::is_local_addr(c$id$orig_h) ? OUTBOUND : INBOUND;
c$ssh$resp_size = server_bytes;
if ( server_bytes < authentication_data_size )
if ( done )
{
c$ssh$status = "failure";
event SSH::heuristic_failed_login(c);
# If this connection is done, then we can look to see if
# this matches the conditions for a failed login. Failed
# logins are only detected at connection state removal.
if ( # Require originators to have sent at least 50 bytes.
c$orig$size > 50 &&
# Responders must be below 4000 bytes.
c$resp$size < 4000 &&
# Responder must have sent fewer than 40 packets.
c$resp$num_pkts < 40 &&
# If there was a content gap we can't reliably do this heuristic.
c$conn$missed_bytes == 0)# &&
# Only "normal" connections can count.
#c$conn?$conn_state && c$conn$conn_state in valid_states )
{
c$ssh$status = "failure";
event SSH::heuristic_failed_login(c);
}
if ( c$resp$size > authentication_data_size )
{
c$ssh$status = "success";
event SSH::heuristic_successful_login(c);
}
}
else
{
# presumed successful login
c$ssh$status = "success";
event SSH::heuristic_successful_login(c);
{
# If this connection is still being tracked, then it's possible
# to watch for it to be a successful connection.
if ( c$resp$size > authentication_data_size )
{
c$ssh$status = "success";
event SSH::heuristic_successful_login(c);
}
else
# This connection must be tracked longer. Let the scheduled
# check happen again.
return;
}
# Set the direction for the log.
c$ssh$direction = Site::is_local_addr(c$id$orig_h) ? OUTBOUND : INBOUND;
# Set the "done" flag to prevent the watching event from rescheduling
# after detection is done.
c$ssh$done=T;
Log::write(SSH::LOG, c$ssh);
if ( skip_processing_after_detection )
{
@ -161,18 +161,6 @@ function check_ssh_connection(c: connection, done: bool)
}
}
event SSH::heuristic_successful_login(c: connection) &priority=-5
{
NOTICE([$note=Login,
$msg="Heuristically detected successful SSH login.",
$conn=c]);
Log::write(SSH::LOG, c$ssh);
}
event SSH::heuristic_failed_login(c: connection) &priority=-5
{
Log::write(SSH::LOG, c$ssh);
}
event connection_state_remove(c: connection) &priority=-5
{