Do not accept handshakes with peers trying to negotiate TLS lower than 1.2.
TLS 1.1 and 1.0 are not recommended and therefore will, by default,
allow TLS 1.2 as minimum version.
The minimum allowed version can still be controlled via
'--tls-version-min'.
At the same time automatically set '--tls-version-min' to 1.0 if the
user requires compatibility with versions onlder than 2.3.7, as that was
the only version supported back then.
Signed-off-by: Arne Schwabe <a...@rfc2549.org>
Signed-off-by: Antonio Quartulli <a...@unstable.cc>
---
Changes from v1:
- remove bogus ssl_flags initialization in init_options()
Changes.rst | 5 +++++
doc/man-sections/generic-options.rst | 2 ++
src/openvpn/options.c | 15 +++++++++++++++
3 files changed, 22 insertions(+)
diff --git a/Changes.rst b/Changes.rst
index 5195c634..a7389687 100644
--- a/Changes.rst
+++ b/Changes.rst
@@ -71,6 +71,11 @@ Deprecated features
This option mainly served a role as debug option when NCP was first
introduced. It should now no longer be necessary.
+TLS 1.0 and 1.1 are deprecated
+ ``tls-version-min`` is set to 1.2 by default. OpenVPN 2.6.0 defaults
+ to a minimum TLS version of 1.2 as TLS 1.0 and 1.1 should be generally
+ avoided. Note that OpenVPN versions older than 2.3.7 use TLS 1.0 only.
+
``--cipher`` argument is no longer included in ``--data-ciphers`` by default
Data cipher negotiation has been introduced in 2.4.0 and been significantly
improved in 2.5.0. The implicit fallback to the cipher specified in
diff --git a/doc/man-sections/generic-options.rst
b/doc/man-sections/generic-options.rst
index 3e099e12..e6c1fe45 100644
--- a/doc/man-sections/generic-options.rst
+++ b/doc/man-sections/generic-options.rst
@@ -70,6 +70,8 @@ which mode OpenVPN is configured as.
``--data-ciphers``
- 2.3.x or lower: ``--data-cipher-fallback`` is automatically added with
the same cipher as ``--cipher``
+ - 2.3.6 or lower: ``--tls-version-min 1.0`` is added to the configuration
+ when ``--tls-version-min`` is not explicitly set.
--config file
Load additional config options from ``file`` where each line corresponds
diff --git a/src/openvpn/options.c b/src/openvpn/options.c
index 4b6655d9..b3a83aa1 100644
--- a/src/openvpn/options.c
+++ b/src/openvpn/options.c
@@ -3164,6 +3164,21 @@ need_compatibility_before(const struct options *o,
unsigned int version)
static void
options_set_backwards_compatible_options(struct options *o)
{
+ /* TLS min version is not set */
+ if ((o->ssl_flags & SSLF_TLS_VERSION_MIN_MASK) == 0)
+ {
+ if (need_compatibility_before(o, 20307))
+ {
+ /* 2.3.6 and earlier have TLS 1.0 only, set minimum to TLS 1.0 */
+ o->ssl_flags = (TLS_VER_1_0 << SSLF_TLS_VERSION_MIN_SHIFT);
+ }
+ else
+ {
+ /* Use TLS 1.2 as proper default */
+ o->ssl_flags = (TLS_VER_1_2 << SSLF_TLS_VERSION_MIN_SHIFT);
+ }
+ }
+
/* Versions < 2.5.0 do need --cipher in the list of accepted ciphers.
* Version 2.4 might probably does not need it but NCP was not so
* good with 2.4 and ncp-disable might be more common on 2.4 peers.
--
2.32.0
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