Merge branch 'tmp-dtls12' into 'master'

Added support for DTLS1.2 with anyconnect clients

Closes #193 and #188

See merge request openconnect/ocserv!92

NEWS

@@ -1,6 +1,7 @@
 * Version 0.12.2 (unreleased)
 - Added support for AES256-SHA legacy cipher. This allows the anyconnect
   clients to use AES256.
+- Added support for the DTLS1.2 protocol hack used by in Anyconnect clients.
 
 
 * Version 0.12.1 (released 2018-05-12)

src/http-heads.gperf

@@ -12,6 +12,7 @@ X-DTLS-Accept-Encoding, HEADER_DTLS_ENCODING
 Connection, HEADER_CONNECTION
 X-DTLS-Master-Secret, HEADER_MASTER_SECRET
 X-DTLS-CipherSuite, HEADER_DTLS_CIPHERSUITE
+X-DTLS12-CipherSuite, HEADER_DTLS12_CIPHERSUITE
 X-CSTP-Base-MTU, HEADER_CSTP_BASE_MTU
 X-CSTP-MTU, HEADER_CSTP_MTU
 X-CSTP-Address-Type, HEADER_CSTP_ATYPE

src/worker-http.c

@@ -90,7 +90,6 @@ static const dtls_ciphersuite_st ciphersuites[] = {
 	 .gnutls_mac = GNUTLS_MAC_AEAD,
 	 .gnutls_kx = GNUTLS_KX_RSA,
 	 .gnutls_cipher = GNUTLS_CIPHER_AES_128_GCM,
-	 .txt_version = "3.2.7",
 	 .server_prio = 80},
 	{
 	 .oc_name = CS_AES256_GCM,
@@ -101,7 +100,6 @@ static const dtls_ciphersuite_st ciphersuites[] = {
 	 .gnutls_kx = GNUTLS_KX_RSA,
 	 .gnutls_cipher = GNUTLS_CIPHER_AES_256_GCM,
 	 .server_prio = 90,
-	 .txt_version = "3.2.7",
 	 },
 	{
 	 .oc_name = "AES256-SHA",
@@ -135,6 +133,39 @@ static const dtls_ciphersuite_st ciphersuites[] = {
 	 }
 };
 
+/* In the following we use %NO_SESSION_HASH:%DISABLE_SAFE_RENEGOTIATION because certain
+ * versions of openssl send the extended master secret extension in this
+ * resumed session. Since the state of this extension is undefined
+ * (it's not a real session we are resuming), we explicitly disable this
+ * extension to avoid interop issues. Furthermore gnutls does seem to
+ * be sending the renegotiation extension which openssl doesn't like (see #193) */
+
+#define WORKAROUND_STR "%NO_SESSION_HASH:%DISABLE_SAFE_RENEGOTIATION"
+static const dtls_ciphersuite_st ciphersuites12[] = {
+	{
+	 .oc_name = "AES128-GCM-SHA256",
+	 .gnutls_name =
+	 "NONE:+VERS-DTLS1.2:+COMP-NULL:+AES-128-GCM:+AEAD:+RSA:+SIGN-ALL:"WORKAROUND_STR,
+	 .gnutls_version = GNUTLS_DTLS1_2,
+	 .gnutls_mac = GNUTLS_MAC_AEAD,
+	 .gnutls_kx = GNUTLS_KX_RSA,
+	 .gnutls_cipher = GNUTLS_CIPHER_AES_128_GCM,
+	 .dtls12_mode = 1,
+	 .server_prio = 50
+	},
+	{
+	 .oc_name = "AES256-GCM-SHA384",
+	 .gnutls_name =
+	 "NONE:+VERS-DTLS1.2:+COMP-NULL:+AES-256-GCM:+AEAD:+RSA:+SIGN-ALL:"WORKAROUND_STR,
+	 .gnutls_version = GNUTLS_DTLS1_2,
+	 .gnutls_mac = GNUTLS_MAC_AEAD,
+	 .gnutls_kx = GNUTLS_KX_RSA,
+	 .gnutls_cipher = GNUTLS_CIPHER_AES_256_GCM,
+	 .dtls12_mode = 1,
+	 .server_prio = 90
+	}
+};
+
 #ifdef HAVE_LZ4
 /* Wrappers over LZ4 functions */
 static
@@ -223,6 +254,7 @@ void header_value_check(struct worker_st *ws, struct http_req_st *req)
 	char *token, *value;
 	char *str, *p;
 	const dtls_ciphersuite_st *cand = NULL;
+	const dtls_ciphersuite_st *saved_ciphersuite;
 	const compression_method_st *comp_cand = NULL;
 	const compression_method_st **selected_comp;
 	int want_cipher;
@@ -344,7 +376,9 @@ void header_value_check(struct worker_st *ws, struct http_req_st *req)
 		break;
 
 	case HEADER_DTLS_CIPHERSUITE:
-		req->selected_ciphersuite = NULL;
+		if (req->use_psk || !WSCONFIG(ws)->dtls_legacy)
+			break;
+
 		str = (char *)value;
 
 		p = strstr(str, DTLS_PROTO_INDICATOR);
@@ -353,10 +387,14 @@ void header_value_check(struct worker_st *ws, struct http_req_st *req)
 			if (WSCONFIG(ws)->dtls_psk) {
 				req->use_psk = 1;
 				req->master_secret_set = 1; /* we don't need it */
+				req->selected_ciphersuite = NULL;
 				break;
 			}
 		}
 
+		if (req->selected_ciphersuite) /* if set via HEADER_DTLS12_CIPHERSUITE */
+			break;
+
 		if (ws->session != NULL) {
 			want_mac = gnutls_mac_get(ws->session);
 			want_cipher = gnutls_cipher_get(ws->session);
@@ -370,10 +408,6 @@ void header_value_check(struct worker_st *ws, struct http_req_st *req)
 			     i < sizeof(ciphersuites) / sizeof(ciphersuites[0]);
 			     i++) {
 				if (strcmp(token, ciphersuites[i].oc_name) == 0) {
-					if (ciphersuites[i].txt_version != NULL && gnutls_check_version(ciphersuites[i].txt_version) == NULL) {
-						continue; /* not supported */
-					}
-
 					if (cand == NULL ||
 					    cand->server_prio < ciphersuites[i].server_prio ||
 					    (want_cipher != -1 && want_cipher == ciphersuites[i].gnutls_cipher &&
@@ -397,6 +431,76 @@ void header_value_check(struct worker_st *ws, struct http_req_st *req)
 	        req->selected_ciphersuite = cand;
 
 		break;
+
+	case HEADER_DTLS12_CIPHERSUITE:
+		if (req->use_psk || !WSCONFIG(ws)->dtls_legacy)
+			break;
+
+		/* in gnutls 3.6.0+ there is a regression which makes
+		 * anyconnect's openssl fail: https://gitlab.com/gnutls/gnutls/merge_requests/868
+		 */
+#ifdef gnutls_check_version_numeric
+		if (!gnutls_check_version_numeric(3,6,6) &&
+		    (!gnutls_check_version_numeric(3,3,0) || gnutls_check_version_numeric(3,6,0))) {
+			break;
+		}
+#endif
+
+		str = (char *)value;
+
+		p = strstr(str, DTLS_PROTO_INDICATOR);
+		if (p != NULL && (p[sizeof(DTLS_PROTO_INDICATOR)-1] == 0 || p[sizeof(DTLS_PROTO_INDICATOR)-1] == ':')) {
+			/* OpenConnect DTLS setup was detected. */
+			if (WSCONFIG(ws)->dtls_psk) {
+				req->use_psk = 1;
+				req->master_secret_set = 1; /* we don't need it */
+				req->selected_ciphersuite = NULL;
+				break;
+			}
+		}
+
+		saved_ciphersuite = req->selected_ciphersuite;
+		req->selected_ciphersuite = NULL;
+
+		if (ws->session != NULL) {
+			want_mac = gnutls_mac_get(ws->session);
+			want_cipher = gnutls_cipher_get(ws->session);
+		} else {
+			want_mac = -1;
+			want_cipher = -1;
+		}
+
+		while ((token = strtok(str, ":")) != NULL) {
+			for (i = 0;
+			     i < sizeof(ciphersuites12) / sizeof(ciphersuites12[0]);
+			     i++) {
+				if (strcmp(token, ciphersuites12[i].oc_name) == 0) {
+					if (cand == NULL ||
+					    cand->server_prio < ciphersuites12[i].server_prio ||
+					    (want_cipher != -1 && want_cipher == ciphersuites12[i].gnutls_cipher &&
+					     want_mac == ciphersuites12[i].gnutls_mac)) {
+						cand =
+						    &ciphersuites12[i];
+
+						/* if our candidate matches the TLS session
+						 * ciphersuite, we are finished */
+						if (want_cipher != -1) {
+							if (want_cipher == cand->gnutls_cipher &&
+							    want_mac == cand->gnutls_mac)
+							    goto ciphersuite12_finish;
+						}
+					}
+				}
+			}
+			str = NULL;
+		}
+ ciphersuite12_finish:
+	        req->selected_ciphersuite = cand;
+
+	        if (req->selected_ciphersuite == NULL && saved_ciphersuite)
+			req->selected_ciphersuite = saved_ciphersuite;
+
+		break;
 #ifdef ENABLE_COMPRESSION
 	case HEADER_DTLS_ENCODING:
 	case HEADER_CSTP_ENCODING:

src/worker-vpn.c

@@ -274,7 +274,7 @@ static int setup_dtls_psk_keys(gnutls_session_t session, struct worker_st *ws)
 	return 0;
 }
 
-static int setup_dtls0_9_keys(gnutls_session_t session, struct worker_st *ws)
+static int setup_legacy_dtls_keys(gnutls_session_t session, struct worker_st *ws)
 {
 	int ret;
 	gnutls_datum_t master =
@@ -351,8 +351,8 @@ static int setup_dtls_connection(struct worker_st *ws)
 			oclog(ws, LOG_INFO, "CISCO client compatibility (dtls-legacy) is disabled; will not setup a DTLS session");
 			goto fail;
 		}
-		oclog(ws, LOG_INFO, "setting up DTLS-0.9 connection");
-		ret = setup_dtls0_9_keys(session, ws);
+		oclog(ws, LOG_INFO, "setting up legacy DTLS (resumption) connection");
+		ret = setup_legacy_dtls_keys(session, ws);
 	}
 
 	if (ret < 0) {
@@ -2208,7 +2208,8 @@ static int connect_handler(worker_st * ws)
 			oclog(ws, LOG_INFO, "DTLS ciphersuite: %s",
 			      ws->req.selected_ciphersuite->oc_name);
 			ret =
-			    cstp_printf(ws, "X-DTLS-CipherSuite: %s\r\n",
+			    cstp_printf(ws, "X-DTLS%s-CipherSuite: %s\r\n",
+				        (ws->req.selected_ciphersuite->dtls12_mode!=0)?"12":"",
 				        ws->req.selected_ciphersuite->oc_name);
 			SEND_ERR(ret);
 

src/worker.h

@@ -57,6 +57,7 @@ enum {
 	HEADER_DEVICE_TYPE,
 	HEADER_PLATFORM,
 	HEADER_DTLS_CIPHERSUITE,
+	HEADER_DTLS12_CIPHERSUITE,
 	HEADER_CONNECTION,
 	HEADER_FULL_IPV6,
 	HEADER_USER_AGENT,
@@ -100,12 +101,12 @@ typedef struct compression_method_st {
 typedef struct dtls_ciphersuite_st {
 	const char* oc_name;
 	const char* gnutls_name; /* the gnutls priority string to set */
+	unsigned dtls12_mode;
 	unsigned server_prio; /* the highest the more we want to negotiate that */
 	unsigned gnutls_cipher;
 	unsigned gnutls_kx;
 	unsigned gnutls_mac;
 	unsigned gnutls_version;
-	const char *txt_version;
 } dtls_ciphersuite_st;
 
 #ifdef HAVE_GSSAPI