Merge remote-tracking branch 'origin/master' into topic/vladg/ssh

scripts/policy/protocols/ssl/validate-certs.bro

@@ -12,16 +12,16 @@ export {
 		## invalid.
 		Invalid_Server_Cert
 	};
-	
+
 	redef record Info += {
 		## Result of certificate validation for this connection.
 		validation_status: string &log &optional;
 	};
-	
+
 	## MD5 hash values for recently validated chains along with the
 	## validation status message are kept in this table to avoid constant
 	## validation every time the same certificate chain is seen.
-	global recently_validated_certs: table[string] of string = table() 
+	global recently_validated_certs: table[string] of string = table()
 		&read_expire=5mins &synchronized &redef;
 }
 
@@ -33,6 +33,7 @@ event ssl_established(c: connection) &priority=3
 		return;
 
 	local chain_id = join_string_vec(c$ssl$cert_chain_fuids, ".");
+	local hash = c$ssl$cert_chain[0]$sha1;
 
 	local chain: vector of opaque of x509 = vector();
 	for ( i in c$ssl$cert_chain )
@@ -57,7 +58,7 @@ event ssl_established(c: connection) &priority=3
 		local message = fmt("SSL certificate validation failed with (%s)", c$ssl$validation_status);
 		NOTICE([$note=Invalid_Server_Cert, $msg=message,
 		        $sub=c$ssl$subject, $conn=c,
-		        $identifier=cat(c$id$resp_h,c$id$resp_p,c$ssl$validation_status)]);
+		        $identifier=cat(c$id$resp_h,c$id$resp_p,hash,c$ssl$validation_status)]);
 		}
 	}
 

scripts/policy/protocols/ssl/validate-ocsp.bro

@@ -34,9 +34,10 @@ event ssl_stapled_ocsp(c: connection, is_orig: bool, response: string) &priority
 
 event ssl_established(c: connection) &priority=3
 	{
-	if ( ! c$ssl?$cert_chain || |c$ssl$cert_chain| == 0 || !c$ssl?$ocsp_response )
+	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 )
 		{

scripts/policy/protocols/ssl/weak-keys.bro

@@ -1,5 +1,5 @@
-##! Generate notices when SSL/TLS connections use certificates or DH parameters
-##! that have potentially unsafe key lengths.
+##! Generate notices when SSL/TLS connections use certificates, DH parameters,
+##! or cipher suites that are deemed to be insecure.
 
 @load base/protocols/ssl
 @load base/frameworks/notice
@@ -11,17 +11,20 @@ export {
 	redef enum Notice::Type += {
 		## Indicates that a server is using a potentially unsafe key.
 		Weak_Key,
+		## Indicates that a server is using a potentially unsafe version
+		Old_Version,
+		## Indicates that a server is using a potentially unsafe cipher
+		Weak_Cipher
 	};
 
-	## The category of hosts you would like to be notified about which have
-	## certificates that are going to be expiring soon.  By default, these
-	## notices will be suppressed by the notice framework for 1 day after a particular
-	## certificate has had a notice generated. Choices are: LOCAL_HOSTS, REMOTE_HOSTS,
-	## ALL_HOSTS, NO_HOSTS
+	## The category of hosts you would like to be notified about which are using weak
+	## keys/ciphers/protocol_versions.  By default, these notices will be suppressed
+	## by the notice framework for 1 day after a particular host has had a notice
+	## generated. Choices are: LOCAL_HOSTS, REMOTE_HOSTS, ALL_HOSTS, NO_HOSTS
 	const notify_weak_keys = LOCAL_HOSTS &redef;
 
 	## The minimal key length in bits that is considered to be safe. Any shorter
-	## (non-EC) key lengths will trigger the notice.
+	## (non-EC) key lengths will trigger a notice.
 	const notify_minimal_key_length = 2048 &redef;
 
 	## Warn if the DH key length is smaller than the certificate key length. This is
@@ -29,6 +32,17 @@ export {
 	## certificate key length. However, it is very common and cannot be avoided in some
 	## settings (e.g. with old jave clients).
 	const notify_dh_length_shorter_cert_length = T &redef;
+
+	## Warn if a server negotiates a SSL session with a protocol version smaller than
+	## the specified version. By default, the minimal version is TLSv10 because SSLv2
+	## and v3 have serious security issued.
+	## See https://tools.ietf.org/html/draft-thomson-sslv3-diediedie-00
+	## To disable, set to SSLv20
+	const tls_minimum_version = TLSv10 &redef;
+
+	## Warn if a server negotiates an unsafe cipher suite. By default, we only warn when
+	## encountering old export cipher suites, or RC4 (see RFC7465).
+	const unsafe_ciphers_regex = /(_EXPORT_)|(_RC4_)/ &redef;
 }
 
 # We check key lengths only for DSA or RSA certificates. For others, we do
@@ -43,6 +57,7 @@ event ssl_established(c: connection) &priority=3
 
 	local fuid = c$ssl$cert_chain_fuids[0];
 	local cert = c$ssl$cert_chain[0]$x509$certificate;
+	local hash = c$ssl$cert_chain[0]$sha1;
 
 	if ( !cert?$key_type || !cert?$key_length )
 		return;
@@ -56,7 +71,32 @@ event ssl_established(c: connection) &priority=3
 		NOTICE([$note=Weak_Key,
 			$msg=fmt("Host uses weak certificate with %d bit key", key_length),
 			$conn=c, $suppress_for=1day,
-			$identifier=cat(c$id$resp_h, c$id$resp_h, key_length)
+			$identifier=cat(c$id$resp_h, c$id$resp_h, hash, key_length)
+		]);
+	}
+
+# Check for old SSL versions and weak connection keys
+event ssl_server_hello(c: connection, version: count, possible_ts: time, server_random: string, session_id: string, cipher: count, comp_method: count) &priority=3
+	{
+	if ( ! addr_matches_host(c$id$resp_h, notify_weak_keys) )
+		return;
+
+	if ( version < tls_minimum_version )
+		{
+		local minimum_string = version_strings[tls_minimum_version];
+		local host_string = version_strings[version];
+		NOTICE([$note=Old_Version,
+			$msg=fmt("Host uses protocol version %s which is lower than the safe minimum %s", host_string, minimum_string),
+			$conn=c, $suppress_for=1day,
+			$identifier=cat(c$id$resp_h, c$id$resp_h)
+		]);
+		}
+
+	if ( unsafe_ciphers_regex in c$ssl$cipher )
+		NOTICE([$note=Weak_Cipher,
+			$msg=fmt("Host established connection using unsafe ciper suite %s", c$ssl$cipher),
+			$conn=c, $suppress_for=1day,
+			$identifier=cat(c$id$resp_h, c$id$resp_h, c$ssl$cipher)
 		]);
 	}