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files.zeek
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files.zeek
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@load ./main
@load base/utils/conn-ids
@load base/frameworks/files
@load base/files/x509
module SSL;
export {
## Set this to true to include the server certificate subject and
## issuer from the SSL log file. This information is still available
## in x509.log.
const log_include_server_certificate_subject_issuer = F &redef;
## Set this to true to include the client certificate subject
## and issuer in the SSL logfile. This information is rarely present
## and probably only interesting in very specific circumstances
const log_include_client_certificate_subject_issuer = F &redef;
redef record Info += {
## Chain of certificates offered by the server to validate its
## complete signing chain.
cert_chain: vector of Files::Info &optional;
## An ordered vector of all certificate fingerprints for the
## certificates offered by the server.
cert_chain_fps: vector of string &optional &log;
## Chain of certificates offered by the client to validate its
## complete signing chain.
client_cert_chain: vector of Files::Info &optional;
## An ordered vector of all certificate fingerprints for the
## certificates offered by the client.
client_cert_chain_fps: vector of string &optional &log;
## Subject of the X.509 certificate offered by the server.
subject: string &log &optional;
## Issuer of the signer of the X.509 certificate offered by the
## server.
issuer: string &log &optional;
## Subject of the X.509 certificate offered by the client.
client_subject: string &log &optional;
## Subject of the signer of the X.509 certificate offered by the
## client.
client_issuer: string &log &optional;
## Set to true if the hostname sent in the SNI matches the certificate.
## Set to false if they do not match. Unset if the client did not send
## an SNI.
sni_matches_cert: bool &log &optional;
## Current number of certificates seen from either side. Used
## to create file handles.
server_depth: count &default=0;
client_depth: count &default=0;
};
## Default file handle provider for SSL.
global get_file_handle: function(c: connection, is_orig: bool): string;
## Default file describer for SSL.
global describe_file: function(f: fa_file): string;
}
function get_file_handle(c: connection, is_orig: bool): string
{
# Unused. File handles are generated in the analyzer.
return "";
}
function describe_file(f: fa_file): string
{
if ( f$source != "SSL" || ! f?$info || ! f$info?$x509 || ! f$info$x509?$certificate )
return "";
# It is difficult to reliably describe a certificate - especially since
# we do not know when this function is called (hence, if the data structures
# are already populated).
#
# Just return a bit of our connection information and hope that is good enough.
for ( _, c in f$conns )
{
if ( c?$ssl )
{
return cat(c$id$resp_h, ":", c$id$resp_p);
}
}
return cat("Serial: ", f$info$x509$certificate$serial, " Subject: ",
f$info$x509$certificate$subject, " Issuer: ",
f$info$x509$certificate$issuer);
}
event zeek_init() &priority=5
{
Files::register_protocol(Analyzer::ANALYZER_SSL,
[$get_file_handle = SSL::get_file_handle,
$describe = SSL::describe_file]);
Files::register_protocol(Analyzer::ANALYZER_DTLS,
[$get_file_handle = SSL::get_file_handle,
$describe = SSL::describe_file]);
local ssl_filter = Log::get_filter(SSL::LOG, "default");
if ( ssl_filter$name != "<not found>" )
{
if ( ! ssl_filter?$exclude )
ssl_filter$exclude = set();
if ( ! log_include_server_certificate_subject_issuer )
{
add ssl_filter$exclude["subject"];
add ssl_filter$exclude["issuer"];
}
if ( ! log_include_client_certificate_subject_issuer )
{
add ssl_filter$exclude["client_subject"];
add ssl_filter$exclude["client_issuer"];
}
Log::add_filter(SSL::LOG, ssl_filter);
}
}
event file_sniff(f: fa_file, meta: fa_metadata) &priority=5
{
if ( ! f?$conns || |f$conns| != 1 )
return;
if ( ! f?$info || ! f$info?$mime_type )
return;
if ( ! ( f$info$mime_type == "application/x-x509-ca-cert" || f$info$mime_type == "application/x-x509-user-cert"
|| f$info$mime_type == "application/pkix-cert" ) )
return;
local c: connection &is_assigned; # to help static analysis
for ( _, c in f$conns )
{
if ( ! c?$ssl )
return;
}
if ( ! c$ssl?$cert_chain )
{
c$ssl$cert_chain = vector();
c$ssl$client_cert_chain = vector();
c$ssl$cert_chain_fps = string_vec();
c$ssl$client_cert_chain_fps = string_vec();
}
# Note - for SSL connections, is_orig indicates client/server, not necessary originator/responder.
if ( f$is_orig )
c$ssl$client_cert_chain += f$info;
else
c$ssl$cert_chain += f$info;
}
hook ssl_finishing(c: connection) &priority=20
{
if ( c$ssl?$cert_chain)
for ( i in c$ssl$cert_chain )
if ( c$ssl$cert_chain[i]?$x509 && c$ssl$cert_chain[i]$x509?$fingerprint )
c$ssl$cert_chain_fps += c$ssl$cert_chain[i]$x509$fingerprint;
if ( c$ssl?$client_cert_chain )
for ( i in c$ssl$client_cert_chain )
if ( c$ssl$client_cert_chain[i]?$x509 && c$ssl$client_cert_chain[i]$x509?$fingerprint )
c$ssl$client_cert_chain_fps += c$ssl$client_cert_chain[i]$x509$fingerprint;
if ( c$ssl?$cert_chain && |c$ssl$cert_chain| > 0 &&
c$ssl$cert_chain[0]?$x509 )
{
if ( c$ssl?$server_name )
{
if ( x509_check_cert_hostname(c$ssl$cert_chain[0]$x509$handle, c$ssl$server_name) != "" )
c$ssl$sni_matches_cert = T;
else
c$ssl$sni_matches_cert = F;
}
c$ssl$subject = c$ssl$cert_chain[0]$x509$certificate$subject;
c$ssl$issuer = c$ssl$cert_chain[0]$x509$certificate$issuer;
}
if ( c$ssl?$client_cert_chain && |c$ssl$client_cert_chain| > 0 &&
c$ssl$client_cert_chain[0]?$x509 )
{
c$ssl$client_subject = c$ssl$client_cert_chain[0]$x509$certificate$subject;
c$ssl$client_issuer = c$ssl$client_cert_chain[0]$x509$certificate$issuer;
}
}