openconnect-7.05-ensure-dtls-ciphers-match-the-allowed.patch

From 4892c7a53bb0adec98c4540a0b127b209625f82a Mon Sep 17 00:00:00 2001
From: Nikos Mavrogiannopoulos <nmav@redhat.com>
Date: Wed, 4 Mar 2015 10:29:06 +0100
Subject: [PATCH 2/2] when using gnutls enable only the DTLS ciphersuites that
 were available during TLS

Signed-off-by: Nikos Mavrogiannopoulos <nmav@redhat.com>
---
 cstp.c                 |  3 ++
 dtls.c                 | 79 ++++++++++++++++++++++++++++++++++++++++++++++----
 gnutls.c               |  7 ++---
 openconnect-internal.h |  2 ++
 4 files changed, 81 insertions(+), 10 deletions(-)

diff --git a/cstp.c b/cstp.c
index d0d7eff..a06ca34 100644
--- a/cstp.c
+++ b/cstp.c
@@ -202,6 +202,9 @@ static int start_cstp_connection(struct openconnect_info *vpninfo)
 	vpninfo->ip_info.domain = vpninfo->ip_info.proxy_pac = NULL;
 	vpninfo->banner = NULL;
 
+	if (!vpninfo->dtls_ciphers)
+		vpninfo->dtls_ciphers = dtls_ciphers_from_conn(vpninfo);
+
 	for (i = 0; i < 3; i++)
 		vpninfo->ip_info.dns[i] = vpninfo->ip_info.nbns[i] = NULL;
 	free_split_routes(vpninfo);
diff --git a/dtls.c b/dtls.c
index abffbf1..6ac537d 100644
--- a/dtls.c
+++ b/dtls.c
@@ -222,6 +222,11 @@ static SSL_SESSION *generate_dtls_session(struct openconnect_info *vpninfo,
 }
 #endif
 
+char *dtls_ciphers_from_conn(struct openconnect_info *vpninfo)
+{
+	return NULL;
+}
+
 static int start_dtls_handshake(struct openconnect_info *vpninfo, int dtls_fd)
 {
 	STACK_OF(SSL_CIPHER) *ciphers;
@@ -438,27 +443,89 @@ void dtls_shutdown(struct openconnect_info *vpninfo)
 #include <gnutls/dtls.h>
 #include "gnutls.h"
 
+#define SSTR(x) x,sizeof(x)
 struct {
 	const char *name;
+	unsigned name_len;
 	gnutls_protocol_t version;
 	gnutls_cipher_algorithm_t cipher;
 	gnutls_mac_algorithm_t mac;
 	const char *prio;
+	unsigned disabled;
 } gnutls_dtls_ciphers[] = {
-	{ "AES128-SHA", GNUTLS_DTLS0_9, GNUTLS_CIPHER_AES_128_CBC, GNUTLS_MAC_SHA1,
+	{ SSTR("AES128-SHA"), GNUTLS_DTLS0_9, GNUTLS_CIPHER_AES_128_CBC, GNUTLS_MAC_SHA1,
 	  "NONE:+VERS-DTLS0.9:+COMP-NULL:+AES-128-CBC:+SHA1:+RSA:%COMPAT" },
-	{ "AES256-SHA", GNUTLS_DTLS0_9, GNUTLS_CIPHER_AES_256_CBC, GNUTLS_MAC_SHA1,
+	{ SSTR("AES256-SHA"), GNUTLS_DTLS0_9, GNUTLS_CIPHER_AES_256_CBC, GNUTLS_MAC_SHA1,
 	  "NONE:+VERS-DTLS0.9:+COMP-NULL:+AES-256-CBC:+SHA1:+RSA:%COMPAT" },
-	{ "DES-CBC3-SHA", GNUTLS_DTLS0_9, GNUTLS_CIPHER_3DES_CBC, GNUTLS_MAC_SHA1,
+	{ SSTR("DES-CBC3-SHA"), GNUTLS_DTLS0_9, GNUTLS_CIPHER_3DES_CBC, GNUTLS_MAC_SHA1,
 	  "NONE:+VERS-DTLS0.9:+COMP-NULL:+3DES-CBC:+SHA1:+RSA:%COMPAT" },
 #if GNUTLS_VERSION_NUMBER >= 0x030207 /* if DTLS 1.2 is supported (and a bug in gnutls is solved) */
-	{ "OC-DTLS1_2-AES128-GCM", GNUTLS_DTLS1_2, GNUTLS_CIPHER_AES_128_GCM, GNUTLS_MAC_AEAD,
+	{ SSTR("OC-DTLS1_2-AES128-GCM"), GNUTLS_DTLS1_2, GNUTLS_CIPHER_AES_128_GCM, GNUTLS_MAC_AEAD,
 	  "NONE:+VERS-DTLS1.2:+COMP-NULL:+AES-128-GCM:+AEAD:+RSA:%COMPAT:+SIGN-ALL" },
-	{ "OC-DTLS1_2-AES256-GCM", GNUTLS_DTLS1_2, GNUTLS_CIPHER_AES_256_GCM, GNUTLS_MAC_AEAD,
+	{ SSTR("OC-DTLS1_2-AES256-GCM"), GNUTLS_DTLS1_2, GNUTLS_CIPHER_AES_256_GCM, GNUTLS_MAC_AEAD,
 	  "NONE:+VERS-DTLS1.2:+COMP-NULL:+AES-256-GCM:+AEAD:+RSA:%COMPAT:+SIGN-ALL" },
 #endif
 };
 
+char *dtls_ciphers_from_conn(struct openconnect_info *vpninfo)
+{
+	/* only enable the ciphers that would have been negotiated in the TLS channel */
+	unsigned i, j;
+	int ret;
+	unsigned idx;
+	gnutls_cipher_algorithm_t cipher;
+	gnutls_mac_algorithm_t mac;
+	struct oc_text_buf *buf;
+	gnutls_priority_t cache;
+	char *p;
+
+	/* everything is disabled by default */
+	for (i = 0; i < sizeof(gnutls_dtls_ciphers)/sizeof(gnutls_dtls_ciphers[0]); i++) {
+		gnutls_dtls_ciphers[i].disabled = 1;
+	}
+
+	ret = gnutls_priority_init(&cache, vpninfo->gnutls_default_prio, NULL);
+	if (ret < 0)
+		return NULL;
+
+	for (j=0;;j++) {
+		ret = gnutls_priority_get_cipher_suite_index(cache, j, &idx);
+		if (ret == GNUTLS_E_UNKNOWN_CIPHER_SUITE)
+			continue;
+		else if (ret < 0)
+			break;
+
+		if (gnutls_cipher_suite_info(idx, NULL, NULL, &cipher, &mac, NULL) != NULL) {
+			for (i = 0; i < sizeof(gnutls_dtls_ciphers)/sizeof(gnutls_dtls_ciphers[0]); i++) {
+				if (gnutls_dtls_ciphers[i].mac == mac && gnutls_dtls_ciphers[i].cipher == cipher) {
+					gnutls_dtls_ciphers[i].disabled = 0;
+					break;
+				}
+			}
+		}
+	}
+
+	buf = buf_alloc();
+
+	for (i = 0; i < sizeof(gnutls_dtls_ciphers)/sizeof(gnutls_dtls_ciphers[0]); i++) {
+		if (!gnutls_dtls_ciphers[i].disabled) {
+			if (buf->buf_len == 0) {
+				buf_append(buf, "%s", gnutls_dtls_ciphers[i].name);
+			} else {
+				buf_append(buf, ":%s", gnutls_dtls_ciphers[i].name);
+			}
+		}
+	}
+
+	/* steal buffer */
+	p = buf->data;
+	buf->data = NULL;
+
+	buf_free(buf);
+ 	gnutls_priority_deinit(cache);
+	return p;
+}
+
 #define DTLS_SEND gnutls_record_send
 #define DTLS_RECV gnutls_record_recv
 #define DTLS_FREE gnutls_deinit
@@ -470,7 +537,7 @@ static int start_dtls_handshake(struct openconnect_info *vpninfo, int dtls_fd)
 	int cipher;
 
 	for (cipher = 0; cipher < sizeof(gnutls_dtls_ciphers)/sizeof(gnutls_dtls_ciphers[0]); cipher++) {
-		if (!strcmp(vpninfo->dtls_cipher, gnutls_dtls_ciphers[cipher].name))
+		if (!strcmp(vpninfo->dtls_cipher, gnutls_dtls_ciphers[cipher].name) && !gnutls_dtls_ciphers[cipher].disabled)
 			goto found_cipher;
 	}
 	vpn_progress(vpninfo, PRG_ERR, _("Unknown DTLS parameters for requested CipherSuite '%s'\n"),
diff --git a/gnutls.c b/gnutls.c
index 34119da..e121842 100644
--- a/gnutls.c
+++ b/gnutls.c
@@ -2070,7 +2070,6 @@ int openconnect_open_https(struct openconnect_info *vpninfo)
 {
 	int ssl_sock = -1;
 	int err;
-	const char * prio;
 
 	if (vpninfo->https_sess)
 		return 0;
@@ -2196,13 +2195,13 @@ int openconnect_open_https(struct openconnect_info *vpninfo)
 				       strlen(vpninfo->hostname));
 
 	if (vpninfo->pfs) {
-		prio = DEFAULT_PRIO":-RSA";
+		vpninfo->gnutls_default_prio = DEFAULT_PRIO":-RSA";
 	} else {
-		prio = DEFAULT_PRIO;
+		vpninfo->gnutls_default_prio = DEFAULT_PRIO;
 	}
 
 	err = gnutls_priority_set_direct(vpninfo->https_sess,
-					prio, NULL);
+					vpninfo->gnutls_default_prio, NULL);
 	if (err) {
 		vpn_progress(vpninfo, PRG_ERR,
 			     _("Failed to set TLS priority string: %s\n"),
diff --git a/openconnect-internal.h b/openconnect-internal.h
index 04cb226..7b7161c 100644
--- a/openconnect-internal.h
+++ b/openconnect-internal.h
@@ -469,6 +469,7 @@ struct openconnect_info {
 	gnutls_session_t https_sess;
 	gnutls_certificate_credentials_t https_cred;
 	char local_cert_md5[MD5_SIZE * 2 + 1]; /* For CSD */
+	const char *gnutls_default_prio;
 #ifdef HAVE_TROUSERS
 	TSS_HCONTEXT tpm_context;
 	TSS_HKEY srk;
@@ -765,6 +766,7 @@ int dtls_setup(struct openconnect_info *vpninfo, int dtls_attempt_period);
 int dtls_mainloop(struct openconnect_info *vpninfo, int *timeout);
 void dtls_close(struct openconnect_info *vpninfo);
 void dtls_shutdown(struct openconnect_info *vpninfo);
+char *dtls_ciphers_from_conn(struct openconnect_info *vpninfo);
 
 /* cstp.c */
 void cstp_common_headers(struct openconnect_info *vpninfo, struct oc_text_buf *buf);
-- 
2.1.0