Most TLS 1.3 libraries inlcude the Chacha20-Poly1305 based cipher suite
beside the AES-GCM based ones int he list of default ciphers suites.
Chacha20-Poly1305 is accepted as good alternative AEAD algorithm to the
AES-GCM algorithm by crypto community.
Follow this and include Chacha20-Poly1305 by default in data-ciphers
when available. This makes picking Chacha20-Poly1305 easier as it only
requires to change server (by changing priority) or client side (removing
AES-GCM from data-ciphers) to change to Chacha20-Poly1305.
Signed-off-by: Arne Schwabe <a...@rfc2549.org>
---
Changes.rst | 5 +++++
doc/man-sections/cipher-negotiation.rst | 3 ++-
doc/man-sections/protocol-options.rst | 3 ++-
src/openvpn/options.c | 25 ++++++++++++++++++++++++-
4 files changed, 33 insertions(+), 3 deletions(-)
diff --git a/Changes.rst b/Changes.rst
index 0323a7f7a..637ed97a6 100644
--- a/Changes.rst
+++ b/Changes.rst
@@ -65,6 +65,11 @@ Deprecated features
This option mainly served a role as debug option when NCP was first
introduced. It should now no longer be necessary.
+
+User-visible Changes
+--------------------
+- CHACHA20-POLY1305 is included in the default of ``--data-ciphers`` when
available.
+
Overview of changes in 2.5
==========================
diff --git a/doc/man-sections/cipher-negotiation.rst
b/doc/man-sections/cipher-negotiation.rst
index a2feb5f9c..423b5ab6a 100644
--- a/doc/man-sections/cipher-negotiation.rst
+++ b/doc/man-sections/cipher-negotiation.rst
@@ -18,7 +18,8 @@ with a AUTH_FAILED message (as seen in client log):
OpenVPN 2.5 will only allow the ciphers specified in ``--data-ciphers``. To
ensure
backwards compatibility also if a cipher is specified using the ``--cipher``
option
it is automatically added to this list. If both options are unset the default
is
-:code:`AES-256-GCM:AES-128-GCM`.
+:code:`AES-256-GCM:AES-128-GCM`. In 2.6 and later the default is changed to
+:code:`AES-256-GCM:AES-128-GCM:CHACHA20-POLY1305` when Chacha20-Poly1305 is
available.
OpenVPN 2.4 clients
-------------------
diff --git a/doc/man-sections/protocol-options.rst
b/doc/man-sections/protocol-options.rst
index 5ae780e1f..0fef90f7b 100644
--- a/doc/man-sections/protocol-options.rst
+++ b/doc/man-sections/protocol-options.rst
@@ -192,7 +192,8 @@ configured in a compatible way between both the local and
remote side.
--data-ciphers cipher-list
Restrict the allowed ciphers to be negotiated to the ciphers in
``cipher-list``. ``cipher-list`` is a colon-separated list of ciphers,
- and defaults to :code:`AES-256-GCM:AES-128-GCM`.
+ and defaults to :code:`AES-256-GCM:AES-128-GCM:CHACHA20-POLY1305` when
+ Chacha20-Poly1305 is available and otherwise :code:`AES-256-GCM:AES-128-GCM`.
For servers, the first cipher from ``cipher-list`` that is also
supported by the client will be pushed to clients that support cipher
diff --git a/src/openvpn/options.c b/src/openvpn/options.c
index 7e146db90..9c01d6a1d 100644
--- a/src/openvpn/options.c
+++ b/src/openvpn/options.c
@@ -842,7 +842,6 @@ init_options(struct options *o, const bool init_gc)
o->stale_routes_check_interval = 0;
o->ifconfig_pool_persist_refresh_freq = 600;
o->scheduled_exit_interval = 5;
- o->ncp_ciphers = "AES-256-GCM:AES-128-GCM";
o->authname = "SHA1";
o->prng_hash = "SHA1";
o->prng_nonce_secret_len = 16;
@@ -3077,6 +3076,29 @@ options_postprocess_verify(const struct options *o)
}
}
+/**
+ * Checks for availibility of Chacha20-Poly1305 and sets
+ * the ncp_cipher to either AES-256-GCM:AES-128-GCM or
+ * AES-256-GCM:AES-128-GCM:CHACHA20-POLY1305.
+ */
+static void
+options_postprocess_setdefault_ncpciphers(struct options *o)
+{
+ if (o->ncp_ciphers)
+ {
+ /* custom --data-ciphers set, keep list */
+ return;
+ }
+ else if (cipher_kt_get("CHACHA20-POLY1305"))
+ {
+ o->ncp_ciphers = "AES-256-GCM:AES-128-GCM:CHACHA20-POLY1305";
+ }
+ else
+ {
+ o->ncp_ciphers = "AES-256-GCM:AES-128-GCM";
+ }
+}
+
static void
options_postprocess_cipher(struct options *o)
{
@@ -3137,6 +3159,7 @@ options_postprocess_mutate(struct options *o)
helper_keepalive(o);
helper_tcp_nodelay(o);
+ options_postprocess_setdefault_ncpciphers(o);
options_postprocess_cipher(o);
options_postprocess_mutate_invariant(o);
--
2.32.0
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