Hi,
Finally found some time to start looking at this patch set.
On 17-11-2019 19:12, Arne Schwabe wrote:
> We currently always announce IV_NCP=2 when we support these ciphers even
> when we do not accept them. This lead to a server pushing a AES-GCM-128
> cipher to clients and the client then rejecting it.
>
> Signed-off-by: Arne Schwabe <a...@rfc2549.org>
> ---
> doc/openvpn.8 | 2 ++
> src/openvpn/init.c | 4 ++++
> src/openvpn/openvpn.h | 1 +
> src/openvpn/ssl.c | 4 +++-
> src/openvpn/ssl_common.h | 1 +
> 5 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/doc/openvpn.8 b/doc/openvpn.8
> index 457c2667..ae24b6c0 100644
> --- a/doc/openvpn.8
> +++ b/doc/openvpn.8
> @@ -4392,6 +4392,8 @@ NCP server (v2.4+) with "\-\-cipher BF\-CBC" and
> "\-\-ncp\-ciphers
> AES\-256\-GCM:AES\-256\-CBC" set can either specify "\-\-cipher BF\-CBC" or
> "\-\-cipher AES\-256\-CBC" and both will work.
>
> +Note, for using NCP with a OpenVPN 2.4 server this list must include
> +the AES\-256\-GCM and AES\-128\-GCM ciphers.
> .\"*********************************************************
> .TP
> .B \-\-ncp\-disable
> diff --git a/src/openvpn/init.c b/src/openvpn/init.c
> index 0bdb0a9c..8f142311 100644
> --- a/src/openvpn/init.c
> +++ b/src/openvpn/init.c
> @@ -623,6 +623,7 @@ save_ncp_options(struct context *c)
> c->c1.ciphername = c->options.ciphername;
> c->c1.authname = c->options.authname;
> c->c1.keysize = c->options.keysize;
> + c->c1.ncp_ciphers = c->options.ncp_ciphers;
> }
>
> /* Restores NCP-negotiable options to original values */
> @@ -632,6 +633,7 @@ restore_ncp_options(struct context *c)
> c->options.ciphername = c->c1.ciphername;
> c->options.authname = c->c1.authname;
> c->options.keysize = c->c1.keysize;
> + c->options.ncp_ciphers = c->c1.ncp_ciphers;
> }
options->ncp_ciphers itself is not negotiable, and thus does not need
restoring, I would think.
> void
> @@ -2827,6 +2829,7 @@ do_init_crypto_tls(struct context *c, const unsigned
> int flags)
> to.tcp_mode = link_socket_proto_connection_oriented(options->ce.proto);
> to.config_ciphername = c->c1.ciphername;
> to.config_authname = c->c1.authname;
> + to.config_ncp_ciphers = c->c1.ncp_ciphers;
> to.ncp_enabled = options->ncp_enabled;
> to.transition_window = options->transition_window;
> to.handshake_window = options->handshake_window;
> @@ -4532,6 +4535,7 @@ inherit_context_child(struct context *dest,
> dest->c1.ciphername = src->c1.ciphername;
> dest->c1.authname = src->c1.authname;
> dest->c1.keysize = src->c1.keysize;
> + dest->c1.ncp_ciphers = src->c1.ncp_ciphers;
>
> /* inherit auth-token */
> dest->c1.ks.auth_token_key = src->c1.ks.auth_token_key;
> diff --git a/src/openvpn/openvpn.h b/src/openvpn/openvpn.h
> index 900db7e1..9e46ad6c 100644
> --- a/src/openvpn/openvpn.h
> +++ b/src/openvpn/openvpn.h
> @@ -209,6 +209,7 @@ struct context_1
>
> const char *ciphername; /**< Data channel cipher from config file */
> const char *authname; /**< Data channel auth from config file */
> + const char *ncp_ciphers; /**< NCP Ciphers */
> int keysize; /**< Data channel keysize from config file */
> #endif
> };
> diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c
> index 4455ebb8..6ca5c79a 100644
> --- a/src/openvpn/ssl.c
> +++ b/src/openvpn/ssl.c
> @@ -2322,7 +2322,9 @@ push_peer_info(struct buffer *buf, struct tls_session
> *session)
>
> /* support for Negotiable Crypto Parameters */
> if (session->opt->ncp_enabled
> - && (session->opt->mode == MODE_SERVER || session->opt->pull))
> + && (session->opt->mode == MODE_SERVER || session->opt->pull)
> + && tls_item_in_cipher_list("AES-128-GCM",
> session->opt->config_ncp_ciphers)
> + && tls_item_in_cipher_list("AES-256-GCM",
> session->opt->config_ncp_ciphers))
> {
> buf_printf(&out, "IV_NCP=2\n");
> }
> diff --git a/src/openvpn/ssl_common.h b/src/openvpn/ssl_common.h
> index 8dd08862..fb82f610 100644
> --- a/src/openvpn/ssl_common.h
> +++ b/src/openvpn/ssl_common.h
> @@ -290,6 +290,7 @@ struct tls_options
>
> const char *config_ciphername;
> const char *config_authname;
> + const char *config_ncp_ciphers;
> bool ncp_enabled;
>
> bool tls_crypt_v2;
>
Otherwise this makes sense and looks good.
-Steffan
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