zeek/scripts/policy/protocols/ssl/validate-ocsp.zeek
2019-04-11 21:12:40 -05:00

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##! Perform validation of stapled OCSP responses.
#!
#! Note: this _only_ performs validation of stapled OCSP responsed. It does
#! not validate OCSP responses that are retrieved via HTTP, because we do not
#! have a mapping to certificates.
@load base/frameworks/notice
@load base/protocols/ssl
module SSL;
export {
redef enum Notice::Type += {
## This indicates that the OCSP response was not deemed
## to be valid.
Invalid_Ocsp_Response
};
redef record Info += {
## Result of ocsp validation for this connection.
ocsp_status: string &log &optional;
## ocsp response as string.
ocsp_response: string &optional;
};
}
# MD5 hash values for recently validated chains along with the OCSP validation
# status are kept in this table to avoid constant validation every time the same
# certificate chain is seen.
global recently_ocsp_validated: table[string] of string = table() &read_expire=5mins;
event ssl_stapled_ocsp(c: connection, is_orig: bool, response: string) &priority=3
{
c$ssl$ocsp_response = response;
}
event ssl_established(c: connection) &priority=3
{
if ( ! c$ssl?$cert_chain || |c$ssl$cert_chain| == 0 || ! c$ssl$cert_chain[0]?$x509 || !c$ssl?$ocsp_response )
return;
local hash = c$ssl$cert_chain[0]$sha1;
local chain: vector of opaque of x509 = vector();
for ( i in c$ssl$cert_chain )
{
if ( c$ssl$cert_chain[i]?$x509 )
chain[i] = c$ssl$cert_chain[i]$x509$handle;
}
local reply_id = cat(md5_hash(c$ssl$ocsp_response), join_string_vec(c$ssl$cert_chain_fuids, "."));
if ( reply_id in recently_ocsp_validated )
{
c$ssl$ocsp_status = recently_ocsp_validated[reply_id];
return;
}
local result = x509_ocsp_verify(chain, c$ssl$ocsp_response, root_certs);
c$ssl$ocsp_status = result$result_string;
recently_ocsp_validated[reply_id] = result$result_string;
if( result$result_string != "good" )
{
local message = fmt("OCSP response validation failed with (%s)", result$result_string);
NOTICE([$note=Invalid_Ocsp_Response, $msg=message,
$sub=c$ssl$subject, $conn=c,
$identifier=cat(c$id$resp_h,c$id$resp_p,c$ssl$ocsp_status)]);
}
}