SSL: add support for signature_algorithms extension.

scripts/base/init-bare.bro

@@ -3009,6 +3009,23 @@ export {
 	};
 }
 
+module SSL;
+export {
+	type SignatureAndHashAlgorithm: record {
+		HashAlgorithm: count; ##< Hash algorithm number
+		SignatureAlgorithm: count; ##< Signature algorithm number
+	};
+}
+
+module GLOBAL;
+
+## A vector of Signature and Hash Algorithms.
+##
+## .. todo:: We need this type definition only for declaring builtin functions
+##    via ``bifcl``. We should extend ``bifcl`` to understand composite types
+##    directly and then remove this alias.
+type signature_and_hashalgorithm_vec: vector of SSL::SignatureAndHashAlgorithm;
+
 module X509;
 export {
 	type Certificate: record {

scripts/base/protocols/ssl/consts.bro

@@ -57,6 +57,27 @@ export {
 		[2] = "fatal",
 	} &default=function(i: count):string { return fmt("unknown-%d", i); };
 
+	## Mapping between numeric codes and human readable strings for hash
+	## algorithms.
+	const hash_algorithms: table[count] of string = {
+		[0] = "none",
+		[1] = "md5",
+		[2] = "sha1",
+		[3] = "sha224",
+		[4] = "sha256",
+		[5] = "sha384",
+		[6] = "sha512",
+	} &default=function(i: count):string { return fmt("unknown-%d", i); };
+
+	## Mapping between numeric codes and human readable strings for signature
+	## algorithms.
+	const signature_algorithms: table[count] of string = {
+		[0] = "anonymous",
+		[1] = "rsa",
+		[2] = "dsa",
+		[3] = "ecdsa",
+	} &default=function(i: count):string { return fmt("unknown-%d", i); };
+
 	## Mapping between numeric codes and human readable strings for alert
 	## descriptions.
 	const alert_descriptions: table[count] of string = {

src/analyzer/protocol/ssl/CMakeLists.txt

@@ -5,6 +5,7 @@ include_directories(BEFORE ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_BINARY_DI
 
 bro_plugin_begin(Bro SSL)
 bro_plugin_cc(SSL.cc DTLS.cc Plugin.cc)
+bro_plugin_bif(types.bif)
 bro_plugin_bif(events.bif)
 bro_plugin_pac(tls-handshake.pac tls-handshake-protocol.pac tls-handshake-analyzer.pac ssl-defs.pac
 	proc-client-hello.pac

src/analyzer/protocol/ssl/events.bif

@@ -83,7 +83,7 @@ event ssl_server_hello%(c: connection, version: count, possible_ts: time, server
 ## .. bro:see:: ssl_alert ssl_client_hello ssl_established ssl_server_hello
 ##    ssl_session_ticket_handshake ssl_extension_ec_point_formats
 ##    ssl_extension_elliptic_curves ssl_extension_application_layer_protocol_negotiation
-##    ssl_extension_server_name
+##    ssl_extension_server_name ssl_extension_signature_algorithm
 event ssl_extension%(c: connection, is_orig: bool, code: count, val: string%);
 
 ## Generated for an SSL/TLS Elliptic Curves extension. This TLS extension is
@@ -99,7 +99,7 @@ event ssl_extension%(c: connection, is_orig: bool, code: count, val: string%);
 ## .. bro:see:: ssl_alert ssl_client_hello ssl_established ssl_server_hello
 ##    ssl_session_ticket_handshake ssl_extension
 ##    ssl_extension_ec_point_formats ssl_extension_application_layer_protocol_negotiation
-##    ssl_extension_server_name ssl_server_curve
+##    ssl_extension_server_name ssl_server_curve ssl_extension_signature_algorithm
 event ssl_extension_elliptic_curves%(c: connection, is_orig: bool, curves: index_vec%);
 
 ## Generated for an SSL/TLS Supported Point Formats extension. This TLS extension
@@ -116,9 +116,26 @@ event ssl_extension_elliptic_curves%(c: connection, is_orig: bool, curves: index
 ## .. bro:see:: ssl_alert ssl_client_hello ssl_established ssl_server_hello
 ##    ssl_session_ticket_handshake ssl_extension
 ##    ssl_extension_elliptic_curves ssl_extension_application_layer_protocol_negotiation
-##    ssl_extension_server_name ssl_server_curve
+##    ssl_extension_server_name ssl_server_curve ssl_extension_signature_algorithm
 event ssl_extension_ec_point_formats%(c: connection, is_orig: bool, point_formats: index_vec%);
 
+## Generated for an Signature Algorithms extension. This TLS extension
+## is defined in :rfc:`5246` and sent by the client in the initial
+## handshake. It gives the list of signature and hash algorithms supported by the
+## client.
+##
+## c: The connection.
+##
+## is_orig: True if event is raised for originator side of the connection.
+##
+## signature_algorithms: List of supported signature and hash algorithm pairs.
+##
+## .. bro:see:: ssl_alert ssl_client_hello ssl_established ssl_server_hello
+##    ssl_session_ticket_handshake ssl_extension
+##    ssl_extension_elliptic_curves ssl_extension_application_layer_protocol_negotiation
+##    ssl_extension_server_name ssl_server_curve
+event ssl_extension_signature_algorithm%(c: connection, is_orig: bool, signature_algorithms: signature_and_hashalgorithm_vec%);
+
 ## Generated if a named curve is chosen by the server for an SSL/TLS connection.
 ## The curve is sent by the server in the ServerKeyExchange message as defined
 ## in :rfc:`4492`, in case an ECDH or ECDHE cipher suite is chosen.

src/analyzer/protocol/ssl/tls-handshake-analyzer.pac

@@ -102,6 +102,30 @@ refine connection Handshake_Conn += {
 		return true;
 		%}
 
+	function proc_signature_algorithm(rec: HandshakeRecord, supported_signature_algorithms: SignatureAndHashAlgorithm[]) : bool
+		%{
+		RecordType* rt = BifType::Record::SSL::SignatureAndHashAlgorithm;
+		VectorType* vt = new VectorType(rt);
+
+		VectorVal* slist = new VectorVal(vt);
+		Unref(vt); // not consumed, VectorVal refs.
+
+		if ( supported_signature_algorithms )
+			{
+			for ( unsigned int i = 0; i < supported_signature_algorithms->size(); ++i )
+				{
+				RecordVal* el = new RecordVal(rt);
+				el->Assign(0, new Val((*supported_signature_algorithms)[i]->HashAlgorithm(), TYPE_COUNT));
+				el->Assign(1, new Val((*supported_signature_algorithms)[i]->SignatureAlgorithm(), TYPE_COUNT));
+				slist->Assign(i, el);
+				}
+			}
+
+		BifEvent::generate_ssl_extension_signature_algorithm(bro_analyzer(), bro_analyzer()->Conn(), ${rec.is_orig}, slist);
+
+		return true;
+		%}
+
 	function proc_apnl(rec: HandshakeRecord, protocols: ProtocolName[]) : bool
 		%{
 		VectorVal* plist = new VectorVal(internal_type("string_vec")->AsVectorType());
@@ -247,6 +271,10 @@ refine typeattr EllipticCurves += &let {
 	proc : bool = $context.connection.proc_elliptic_curves(rec, elliptic_curve_list);
 };
 
+refine typeattr SignatureAlgorithm += &let {
+	proc : bool = $context.connection.proc_signature_algorithm(rec, supported_signature_algorithms);
+}
+
 refine typeattr ApplicationLayerProtocolNegotiationExtension += &let {
 	proc : bool = $context.connection.proc_apnl(rec, protocol_name_list);
 };

src/analyzer/protocol/ssl/tls-handshake-protocol.pac

@@ -458,6 +458,7 @@ type SSLExtension(rec: HandshakeRecord) = record {
 		EXT_EC_POINT_FORMATS -> ec_point_formats: EcPointFormats(rec)[] &until($element == 0 || $element != 0);
 #		EXT_STATUS_REQUEST -> status_request: StatusRequest(rec)[] &until($element == 0 || $element != 0);
 		EXT_SERVER_NAME -> server_name: ServerNameExt(rec)[] &until($element == 0 || $element != 0);
+		EXT_SIGNATURE_ALGORITHMS -> signature_algorithm: SignatureAlgorithm(rec)[] &until($element == 0 || $element != 0);
 		default -> data: bytestring &restofdata;
 	};
 } &length=data_len+4 &exportsourcedata;
@@ -501,6 +502,16 @@ type EcPointFormats(rec: HandshakeRecord) = record {
 	point_format_list: uint8[length];
 };
 
+type SignatureAndHashAlgorithm() = record {
+	HashAlgorithm: uint8;
+	SignatureAlgorithm: uint8;
+}
+
+type SignatureAlgorithm(rec: HandshakeRecord) = record {
+	length: uint16;
+	supported_signature_algorithms: SignatureAndHashAlgorithm[] &until($input.length() == 0);
+}
+
 type EllipticCurves(rec: HandshakeRecord) = record {
 	length: uint16;
 	elliptic_curve_list: uint16[length/2];

src/analyzer/protocol/ssl/tls-handshake.pac

@@ -3,6 +3,11 @@
 %include binpac.pac
 %include bro.pac
 
+%extern{
+#include "types.bif.h"
+#include "events.bif.h"
+%}
+
 analyzer TLSHandshake withcontext {
 	connection: Handshake_Conn;
 	flow:       Handshake_Flow;

testing/btest/Baseline/scripts.base.protocols.ssl.tls-extension-events/.stdout

@@ -6,6 +6,15 @@ secp521r1
 Point formats, 192.168.4.149, 74.125.239.152, T
 uncompressed
 ALPN, 192.168.4.149, 74.125.239.152, [spdy/3, spdy/3.1, http/1.1]
+signature_algorithm, 192.168.4.149, 74.125.239.152
+sha256, rsa
+sha384, rsa
+sha1, rsa
+sha256, ecdsa
+sha384, ecdsa
+sha1, ecdsa
+sha256, dsa
+sha1, dsa
 Point formats, 192.168.4.149, 74.125.239.152, F
 uncompressed
 ansiX962_compressed_prime

testing/btest/scripts/base/protocols/ssl/tls-extension-events.test

@@ -24,3 +24,12 @@ event ssl_extension_server_name(c: connection, is_orig: bool, names: string_vec)
 	{
 	print "server_name", c$id$orig_h, c$id$resp_h, names;
 	}
+
+event ssl_extension_signature_algorithm(c: connection, is_orig: bool, signature_algorithms: vector of SSL::SignatureAndHashAlgorithm)
+	{
+	print "signature_algorithm", c$id$orig_h, c$id$resp_h;
+	for ( i in signature_algorithms)
+		{
+		print SSL::hash_algorithms[signature_algorithms[i]$HashAlgorithm], SSL::signature_algorithms[signature_algorithms[i]$SignatureAlgorithm];
+		}
+	}