Make KRB5SignedPath less fragile, only sign trivial parts of the encTicketPart

Sign the client and auth time (like its done in the PAC) and let that
be ehough for now. Add a Typed hole so that we don't break wireprotocol
next time.

kdc/kerberos5.c

@@ -1747,6 +1747,7 @@ _kdc_as_rep(krb5_context context,
 				  config,
 				  server,
 				  setype,
+				  client->entry.principal,
 				  NULL,
 				  NULL,
 				  &et);

kdc/krb5tgs.c

@@ -106,6 +106,7 @@ _kdc_add_KRB5SignedPath(krb5_context context,
 			krb5_kdc_configuration *config,
 			hdb_entry_ex *krbtgt,
 			krb5_enctype enctype,
+			krb5_principal client,
 			krb5_const_principal server,
 			krb5_principals principals,
 			EncTicketPart *tkt)
@@ -125,8 +126,10 @@ _kdc_add_KRB5SignedPath(krb5_context context,
     {
 	KRB5SignedPathData spd;
 	
-	spd.encticket = *tkt;
+	spd.client = client;
+	spd.authtime = tkt->authtime;
 	spd.delegated = principals;
+	spd.method_data = NULL;
 	
 	ASN1_MALLOC_ENCODE(KRB5SignedPathData, data.data, data.length,
 			   &spd, &size, ret);
@@ -153,6 +156,7 @@ _kdc_add_KRB5SignedPath(krb5_context context,
 
     sp.etype = enctype;
     sp.delegated = principals;
+    sp.method_data = NULL;
 
     ret = krb5_create_checksum(context, crypto, KRB5_KU_KRB5SIGNEDPATH, 0,
 			       data.data, data.length, &sp.cksum);
@@ -185,6 +189,7 @@ static krb5_error_code
 check_KRB5SignedPath(krb5_context context,
 		     krb5_kdc_configuration *config,
 		     hdb_entry_ex *krbtgt,
+		     krb5_principal cp,
 		     EncTicketPart *tkt,
 		     krb5_principals *delegated,
 		     int *signedpath)
@@ -200,7 +205,6 @@ check_KRB5SignedPath(krb5_context context,
     if (ret == 0) {
 	KRB5SignedPathData spd;
 	KRB5SignedPath sp;
-	AuthorizationData *ad;
 	size_t size;
 
 	ret = decode_KRB5SignedPath(data.data, data.length, &sp, NULL);
@@ -208,17 +212,13 @@ check_KRB5SignedPath(krb5_context context,
 	if (ret)
 	    return ret;
 
-	spd.encticket = *tkt;
-	/* the KRB5SignedPath is the last entry */
-	ad = spd.encticket.authorization_data;
-	if (--ad->len == 0)
-	    spd.encticket.authorization_data = NULL;
+	spd.client = cp;
+	spd.authtime = tkt->authtime;
 	spd.delegated = sp.delegated;
+	spd.method_data = sp.method_data;
 
 	ASN1_MALLOC_ENCODE(KRB5SignedPathData, data.data, data.length,
 			   &spd, &size, ret);
-	ad->len++;
-	spd.encticket.authorization_data = ad;
 	if (ret) {
 	    free_KRB5SignedPath(&sp);
 	    return ret;
@@ -244,7 +244,9 @@ check_KRB5SignedPath(krb5_context context,
 	free(data.data);
 	if (ret) {
 	    free_KRB5SignedPath(&sp);
-	    return ret;
+	    kdc_log(context, config, 5,
+		    "KRB5SignedPath not signed correctly, not marking as signed");
+	    return 0;
 	}
 
 	if (delegated && sp.delegated) {
@@ -884,6 +886,7 @@ tgs_make_reply(krb5_context context,
 					  config,
 					  krbtgt,
 					  krbtgt_etype,
+					  client_principal,
 					  NULL,
 					  spp,
 					  &et);
@@ -1663,6 +1666,7 @@ server_lookup:
     ret = check_KRB5SignedPath(context,
 			       config,
 			       krbtgt,
+			       cp,
 			       tgt,
 			       &spp,
 			       &signedpath);
@@ -1855,6 +1859,7 @@ server_lookup:
 	ret = check_KRB5SignedPath(context,
 				   config,
 				   krbtgt,
+				   cp,
 				   &adtkt,
 				   NULL,
 				   &ad_signedpath);

lib/asn1/krb5.asn1

@@ -645,8 +645,10 @@ PA-S4U2Self ::= SEQUENCE {
 
 -- never encoded on the wire, just used to checksum over
 KRB5SignedPathData ::= SEQUENCE {
-	encticket[0]	EncTicketPart,
-	delegated[1]	Principals OPTIONAL
+	client[0]	Principal OPTIONAL,
+	authtime[1]	KerberosTime,
+	delegated[2]	Principals OPTIONAL,
+	method_data[3]  METHOD-DATA OPTIONAL
 }
 
 KRB5SignedPath ::= SEQUENCE {
@@ -655,7 +657,8 @@ KRB5SignedPath ::= SEQUENCE {
 	etype[0]	ENCTYPE,
 	cksum[1]	Checksum,
 	-- srvs delegated though
-	delegated[2]	Principals OPTIONAL
+	delegated[2]	Principals OPTIONAL,
+	method_data[3]  METHOD-DATA OPTIONAL
 }
 
 PA-ClientCanonicalizedNames ::= SEQUENCE{