| Message ID | 20210818213354.687736-2-arne@rfc2549.org |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [Openvpn-devel,1/2] Detect unusable ciphers on patched OpenSSL of RHEL/Centos | expand |
Hi, On 18/08/2021 23:33, Arne Schwabe wrote: > 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 <arne@rfc2549.org> Not sure why this is 2/2 as it seems unrelated to 1/2. Indeed I applied and reviewed this patch alone. It does what it says and imho it is pretty clean. Tested with a client that connects against a server having default ciphers. The client, if willing, can specify chacha20poly1305 only and connect with it. This is a sensible change which IMHO will make a lot of people happy. Acked-by: Antonio Quartulli <antonio@openvpn.net>
I have not tested this "in-depth", but the code looks good, and the result
passes my t_client rig with various OpenSSL and mbedTLS versions.
(I have not actually tested "both server and client have CHACHA-POLY
active and using that works" but I trust Antonio there :-) )
Your patch has been applied to the master branch.
commit a38a377fd524d0e14a23ed17487ea3e3d3ad3fe7
Author: Arne Schwabe
Date: Wed Aug 18 23:33:54 2021 +0200
Include Chacha20-Poly1305 into default --data-ciphers when available
Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Antonio Quartulli <antonio@openvpn.net>
Message-Id: <20210818213354.687736-2-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg22745.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
--
kind regards,
Gert Doering
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);
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 <arne@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(-)