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##! Detect the TLS heartbleed attack. See http://heartbleed.com for more.
@load base/protocols/ssl
@load base/frameworks/notice
module Heartbleed;
export {
redef enum Notice::Type += {
## Indicates that a host performed a heartbleed attack or scan.
SSL_Heartbeat_Attack,
## Indicates that a host performing a heartbleed attack was probably successful.
SSL_Heartbeat_Attack_Success,
## Indicates we saw heartbeat requests with odd length. Probably an attack or scan.
SSL_Heartbeat_Odd_Length,
## Indicates we saw many heartbeat requests without a reply. Might be an attack.
SSL_Heartbeat_Many_Requests
};
}
# Do not disable analyzers after detection - otherwhise we will not notice
# encrypted attacks.
redef SSL::disable_analyzer_after_detection=F;
redef record SSL::Info += {
last_originator_heartbeat_request_size: count &optional;
last_responder_heartbeat_request_size: count &optional;
originator_heartbeats: count &default=0;
responder_heartbeats: count &default=0;
# Unencrypted connections - was an exploit attempt detected yet.
heartbleed_detected: bool &default=F;
# Count number of appdata packages and bytes exchanged so far.
enc_appdata_packages: count &default=0;
enc_appdata_bytes: count &default=0;
};
type min_length: record {
cipher: pattern;
min_length: count;
};
global min_lengths: vector of min_length = vector();
global min_lengths_tls11: vector of min_length = vector();
event bro_init()
{
# Minimum length a heartbeat packet must have for different cipher suites.
# Note - tls 1.1f and 1.0 have different lengths :(
# This should be all cipher suites usually supported by vulnerable servers.
min_lengths_tls11 += [$cipher=/_AES_256_GCM_SHA384$/, $min_length=43];
min_lengths_tls11 += [$cipher=/_AES_128_GCM_SHA256$/, $min_length=43];
min_lengths_tls11 += [$cipher=/_256_CBC_SHA384$/, $min_length=96];
min_lengths_tls11 += [$cipher=/_256_CBC_SHA256$/, $min_length=80];
min_lengths_tls11 += [$cipher=/_256_CBC_SHA$/, $min_length=64];
min_lengths_tls11 += [$cipher=/_128_CBC_SHA256$/, $min_length=80];
min_lengths_tls11 += [$cipher=/_128_CBC_SHA$/, $min_length=64];
min_lengths_tls11 += [$cipher=/_3DES_EDE_CBC_SHA$/, $min_length=48];
min_lengths_tls11 += [$cipher=/_SEED_CBC_SHA$/, $min_length=64];
min_lengths_tls11 += [$cipher=/_IDEA_CBC_SHA$/, $min_length=48];
min_lengths_tls11 += [$cipher=/_DES_CBC_SHA$/, $min_length=48];
min_lengths_tls11 += [$cipher=/_DES40_CBC_SHA$/, $min_length=48];
min_lengths_tls11 += [$cipher=/_RC4_128_SHA$/, $min_length=39];
min_lengths_tls11 += [$cipher=/_RC4_128_MD5$/, $min_length=35];
min_lengths_tls11 += [$cipher=/_RC4_40_MD5$/, $min_length=35];
min_lengths_tls11 += [$cipher=/_RC2_CBC_40_MD5$/, $min_length=48];
min_lengths += [$cipher=/_256_CBC_SHA$/, $min_length=48];
min_lengths += [$cipher=/_128_CBC_SHA$/, $min_length=48];
min_lengths += [$cipher=/_3DES_EDE_CBC_SHA$/, $min_length=40];
min_lengths += [$cipher=/_SEED_CBC_SHA$/, $min_length=48];
min_lengths += [$cipher=/_IDEA_CBC_SHA$/, $min_length=40];
min_lengths += [$cipher=/_DES_CBC_SHA$/, $min_length=40];
min_lengths += [$cipher=/_DES40_CBC_SHA$/, $min_length=40];
min_lengths += [$cipher=/_RC4_128_SHA$/, $min_length=39];
min_lengths += [$cipher=/_RC4_128_MD5$/, $min_length=35];
min_lengths += [$cipher=/_RC4_40_MD5$/, $min_length=35];
min_lengths += [$cipher=/_RC2_CBC_40_MD5$/, $min_length=40];
}
event ssl_heartbeat(c: connection, is_orig: bool, length: count, heartbeat_type: count, payload_length: count, payload: string)
{
if ( ! c?$ssl )
return;
if ( heartbeat_type == 1 )
{
local checklength: count = (length<(3+16)) ? length : (length - 3 - 16);
if ( payload_length > checklength )
{
c$ssl$heartbleed_detected = T;
NOTICE([$note=Heartbleed::SSL_Heartbeat_Attack,
$msg=fmt("An TLS heartbleed attack was detected! Record length %d. Payload length %d", length, payload_length),
$conn=c,
$identifier=cat(c$uid, length, payload_length)
]);
}
else if ( is_orig )
{
NOTICE([$note=Heartbleed::SSL_Heartbeat_Attack,
$msg=fmt("Heartbeat request before encryption. Probable Scan without exploit attempt. Message length: %d. Payload length: %d", length, payload_length),
$conn=c,
$n=length,
$identifier=cat(c$uid, length)
]);
}
}
if ( heartbeat_type == 2 && c$ssl$heartbleed_detected )
{
NOTICE([$note=Heartbleed::SSL_Heartbeat_Attack_Success,
$msg=fmt("An TLS heartbleed attack detected before was probably exploited. Message length: %d. Payload length: %d", length, payload_length),
$conn=c,
$identifier=c$uid
]);
}
}
event ssl_encrypted_heartbeat(c: connection, is_orig: bool, length: count)
{
if ( is_orig )
++c$ssl$originator_heartbeats;
else
++c$ssl$responder_heartbeats;
local duration = network_time() - c$start_time;
if ( c$ssl$enc_appdata_packages == 0 )
NOTICE([$note=SSL_Heartbeat_Attack,
$msg=fmt("Heartbeat before ciphertext. Probable attack or scan. Length: %d, is_orig: %d", length, is_orig),
$conn=c,
$n=length,
$identifier=fmt("%s%s", c$uid, "early")
]);
else if ( duration < 1min )
NOTICE([$note=SSL_Heartbeat_Attack,
$msg=fmt("Heartbeat within first minute. Possible attack or scan. Length: %d, is_orig: %d, time: %s", length, is_orig, duration),
$conn=c,
$n=length,
$identifier=fmt("%s%s", c$uid, "early")
]);
if ( c$ssl$originator_heartbeats > c$ssl$responder_heartbeats + 3 )
NOTICE([$note=SSL_Heartbeat_Many_Requests,
$msg=fmt("More than 3 heartbeat requests without replies from server. Possible attack. Client count: %d, server count: %d", c$ssl$originator_heartbeats, c$ssl$responder_heartbeats),
$conn=c,
$n=(c$ssl$originator_heartbeats-c$ssl$responder_heartbeats),
$identifier=fmt("%s%d", c$uid, c$ssl$responder_heartbeats/1000) # re-throw every 1000 heartbeats
]);
if ( c$ssl$responder_heartbeats > c$ssl$originator_heartbeats + 3 )
NOTICE([$note=SSL_Heartbeat_Many_Requests,
$msg=fmt("Server sending more heartbeat responses than requests seen. Possible attack. Client count: %d, server count: %d", c$ssl$originator_heartbeats, c$ssl$responder_heartbeats),
$conn=c,
$n=(c$ssl$originator_heartbeats-c$ssl$responder_heartbeats),
$identifier=fmt("%s%d", c$uid, c$ssl$responder_heartbeats/1000) # re-throw every 1000 heartbeats
]);
if ( is_orig && length < 19 )
NOTICE([$note=SSL_Heartbeat_Odd_Length,
$msg=fmt("Heartbeat message smaller than minimum required length. Probable attack or scan. Message length: %d. Cipher: %s. Time: %f", length, c$ssl$cipher, duration),
$conn=c,
$n=length,
$identifier=fmt("%s-weak-%d", c$uid, length)
]);
# Examine request lengths based on used cipher...
local min_length_choice: vector of min_length;
if ( (c$ssl$version == "TLSv11") || (c$ssl$version == "TLSv12") ) # tls 1.1+ have different lengths for CBC
min_length_choice = min_lengths_tls11;
else
min_length_choice = min_lengths;
for ( i in min_length_choice )
{
if ( min_length_choice[i]$cipher in c$ssl$cipher )
{
if ( length < min_length_choice[i]$min_length )
{
NOTICE([$note=SSL_Heartbeat_Odd_Length,
$msg=fmt("Heartbeat message smaller than minimum required length. Probable attack. Message length: %d. Required length: %d. Cipher: %s. Cipher match: %s", length, min_length_choice[i]$min_length, c$ssl$cipher, min_length_choice[i]$cipher),
$conn=c,
$n=length,
$identifier=fmt("%s-weak-%d", c$uid, length)
]);
}
break;
}
}
if ( is_orig )
{
if ( c$ssl?$last_responder_heartbeat_request_size )
{
# server originated heartbeat. Ignore & continue
delete c$ssl$last_responder_heartbeat_request_size;
}
else
c$ssl$last_originator_heartbeat_request_size = length;
}
else
{
if ( c$ssl?$last_originator_heartbeat_request_size && c$ssl$last_originator_heartbeat_request_size < length )
{
NOTICE([$note=SSL_Heartbeat_Attack_Success,
$msg=fmt("An encrypted TLS heartbleed attack was probably detected! First packet client record length %d, first packet server record length %d. Time: %f",
c$ssl$last_originator_heartbeat_request_size, length, duration),
$conn=c,
$identifier=c$uid # only throw once per connection
]);
}
else if ( ! c$ssl?$last_originator_heartbeat_request_size )
c$ssl$last_responder_heartbeat_request_size = length;
if ( c$ssl?$last_originator_heartbeat_request_size )
delete c$ssl$last_originator_heartbeat_request_size;
}
}
event ssl_encrypted_data(c: connection, is_orig: bool, record_version: count, content_type: count, length: count)
{
if ( !c?$ssl )
return;
if ( content_type == SSL::HEARTBEAT )
event ssl_encrypted_heartbeat(c, is_orig, length);
else if ( (content_type == SSL::APPLICATION_DATA) && (length > 0) )
{
++c$ssl$enc_appdata_packages;
c$ssl$enc_appdata_bytes += length;
}
}