When tls-version-min is unspecified, revert to original versioning approach.

For OpenSSL, this means to use TLSv1_(client|server)_method rather
than SSLv23_(client|server)_method combined with SSL_OP_NO_x flags
for specific TLS versions to disable.

For PolarSSL, this means to implicitly control the TLS version via allowed
ciphersuites.

Point out off-by-default-now setting in the openvpn(8) man page.

This patch is only included in the release/2.3 branch, because it's a
stopgap measure.  2.4 will have it on-by-default, when the remaining
handshake problems are fully debugged and solved.

Signed-off-by: James Yonan <james@openvpn.net>
Signed-off-by: Gert Doering <gert@greenie.muc.de>
Signed-off-by: Steffan Karger <steffan@karger.me>
Acked-by: James Yonan <james@openvpn.net>
Message-Id: <535EC5FE.6060302@karger.me>
URL: http://article.gmane.org/gmane.network.openvpn.devel/8665
Signed-off-by: Gert Doering <gert@greenie.muc.de>

diff --git a/doc/openvpn.8 b/doc/openvpn.8
index 7a33f8aec35195a030f0cf4976ed3e99ae4b719b..ec56030441be8634bb462c900c07459ef26026de 100644 (file)
--- a/doc/openvpn.8
+++ b/doc/openvpn.8
@@ -4275,12 +4275,18 @@ above).
 .\"*********************************************************
 .TP
 .B \-\-tls-version-min version ['or-highest']
-Sets the minimum
+Enable TLS version negotiation, and set the minimum
 TLS version we will accept from the peer (default is "1.0").
 Examples for version
 include "1.0", "1.1", or "1.2".  If 'or-highest' is specified
 and version is not recognized, we will only accept the highest TLS
 version supported by the local SSL implementation.
+
+If this options is not set, the code in OpenVPN 2.3.4 will default
+to using TLS 1.0 only, without any version negotiation.  This reverts
+the beaviour to what OpenVPN versions up to 2.3.2 did, as it turned
+out that TLS version negotiation can lead to handshake problems due
+to new signature algorithms in TLS 1.2.
 .\"*********************************************************
 .TP
 .B \-\-pkcs12 file

diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c
index 93d81e281c1e373134305009c715ac5dab4920a6..ac6818ef405f3dcd0219c0c7dc7589dc8f83bfa5 100644 (file)
--- a/src/openvpn/ssl.c
+++ b/src/openvpn/ssl.c
@@ -486,12 +486,12 @@ init_ssl (const struct options *options, struct tls_root_ctx *new_ctx)
 
   if (options->tls_server)
     {
-      tls_ctx_server_new(new_ctx);
+      tls_ctx_server_new(new_ctx, options->ssl_flags);
       tls_ctx_load_dh_params(new_ctx, options->dh_file, options->dh_file_inline);
     }
   else                         /* if client */
     {
-      tls_ctx_client_new(new_ctx);
+      tls_ctx_client_new(new_ctx, options->ssl_flags);
     }
 
   tls_ctx_set_options(new_ctx, options->ssl_flags);

diff --git a/src/openvpn/ssl_backend.h b/src/openvpn/ssl_backend.h
index 9777242df6c825481342570071ab900c0a4356ef..b37b1e5a9044fbad8c7fd456ad1d5ec93925b7c8 100644 (file)
--- a/src/openvpn/ssl_backend.h
+++ b/src/openvpn/ssl_backend.h
@@ -109,10 +109,11 @@ void tls_clear_error();
  * @return             One of the TLS_VER_x constants or TLS_VER_BAD
  *                      if a parse error should be flagged.
  */
-#define TLS_VER_BAD   -1
-#define TLS_VER_1_0    0 /* default */
-#define TLS_VER_1_1    1
-#define TLS_VER_1_2    2
+#define TLS_VER_BAD    -1
+#define TLS_VER_UNSPEC  0 /* default */
+#define TLS_VER_1_0     1
+#define TLS_VER_1_1     2
+#define TLS_VER_1_2     3
 int tls_version_min_parse(const char *vstr, const char *extra);
 
 /**
@@ -127,15 +128,17 @@ int tls_version_max(void);
  * Initialise a library-specific TLS context for a server.
  *
  * @param ctx          TLS context to initialise
+ * @param ssl_flags     SSLF_x flags from ssl_common.h
  */
-void tls_ctx_server_new(struct tls_root_ctx *ctx);
+void tls_ctx_server_new(struct tls_root_ctx *ctx, unsigned int ssl_flags);
 
 /**
  * Initialises a library-specific TLS context for a client.
  *
  * @param ctx          TLS context to initialise
+ * @param ssl_flags     SSLF_x flags from ssl_common.h
  */
-void tls_ctx_client_new(struct tls_root_ctx *ctx);
+void tls_ctx_client_new(struct tls_root_ctx *ctx, unsigned int ssl_flags);
 
 /**
  * Frees the library-specific TLSv1 context

diff --git a/src/openvpn/ssl_openssl.c b/src/openvpn/ssl_openssl.c
index 08e35925fdb4e4e212c34946cbea44c24f9c3da0..481600a08340add37a9b09c83befc26273f32924 100644 (file)
--- a/src/openvpn/ssl_openssl.c
+++ b/src/openvpn/ssl_openssl.c
@@ -119,11 +119,16 @@ tmp_rsa_cb (SSL * s, int is_export, int keylength)
 }
 
 void
-tls_ctx_server_new(struct tls_root_ctx *ctx)
+tls_ctx_server_new(struct tls_root_ctx *ctx, unsigned int ssl_flags)
 {
+  const int tls_version_min = (ssl_flags >> SSLF_TLS_VERSION_SHIFT) & SSLF_TLS_VERSION_MASK;
+
   ASSERT(NULL != ctx);
 
-  ctx->ctx = SSL_CTX_new (SSLv23_server_method ());
+  if (tls_version_min > TLS_VER_UNSPEC)
+    ctx->ctx = SSL_CTX_new (SSLv23_server_method ());
+  else
+    ctx->ctx = SSL_CTX_new (TLSv1_server_method ());
 
   if (ctx->ctx == NULL)
     msg (M_SSLERR, "SSL_CTX_new SSLv23_server_method");
@@ -132,11 +137,16 @@ tls_ctx_server_new(struct tls_root_ctx *ctx)
 }
 
 void
-tls_ctx_client_new(struct tls_root_ctx *ctx)
+tls_ctx_client_new(struct tls_root_ctx *ctx, unsigned int ssl_flags)
 {
+  const int tls_version_min = (ssl_flags >> SSLF_TLS_VERSION_SHIFT) & SSLF_TLS_VERSION_MASK;
+
   ASSERT(NULL != ctx);
 
-  ctx->ctx = SSL_CTX_new (SSLv23_client_method ());
+  if (tls_version_min > TLS_VER_UNSPEC)
+    ctx->ctx = SSL_CTX_new (SSLv23_client_method ());
+  else
+    ctx->ctx = SSL_CTX_new (TLSv1_client_method ());
 
   if (ctx->ctx == NULL)
     msg (M_SSLERR, "SSL_CTX_new SSLv23_client_method");

diff --git a/src/openvpn/ssl_polarssl.c b/src/openvpn/ssl_polarssl.c
index 6334783d14722317f674dd231fb171492713842a..0dfffd6e99ace0e18e5d859a102b431254ab38e8 100644 (file)
--- a/src/openvpn/ssl_polarssl.c
+++ b/src/openvpn/ssl_polarssl.c
@@ -67,7 +67,7 @@ tls_clear_error()
 }
 
 void
-tls_ctx_server_new(struct tls_root_ctx *ctx)
+tls_ctx_server_new(struct tls_root_ctx *ctx, unsigned int ssl_flags)
 {
   ASSERT(NULL != ctx);
   CLEAR(*ctx);
@@ -84,7 +84,7 @@ tls_ctx_server_new(struct tls_root_ctx *ctx)
 }
 
 void
-tls_ctx_client_new(struct tls_root_ctx *ctx)
+tls_ctx_client_new(struct tls_root_ctx *ctx, unsigned int ssl_flags)
 {
   ASSERT(NULL != ctx);
   CLEAR(*ctx);