| Message ID | 20190923133224.13899-1-arne@rfc2549.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [Openvpn-devel] Only announce IV_NCP=2 when we are willing to support these ciphers | expand |
Hi, On 23/09/2019 15:32, 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. > --- > src/openvpn/init.c | 1 + > src/openvpn/openvpn.h | 1 + > src/openvpn/options.c | 7 +++++++ > src/openvpn/ssl.c | 4 +++- > src/openvpn/ssl_common.h | 1 + > 5 files changed, 13 insertions(+), 1 deletion(-) > > diff --git a/src/openvpn/init.c b/src/openvpn/init.c > index b5a034dc..32f7bc7a 100644 > --- a/src/openvpn/init.c > +++ b/src/openvpn/init.c > @@ -2795,6 +2795,7 @@ 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; I can't find where config_ncp_ciphers is used and I can't find where ncp_ciphers is set...something is missing? > to.ncp_enabled = options->ncp_enabled; > to.transition_window = options->transition_window; > to.handshake_window = options->handshake_window; > diff --git a/src/openvpn/openvpn.h b/src/openvpn/openvpn.h > index 29d21f0a..1fdbfe3c 100644 > --- a/src/openvpn/openvpn.h > +++ b/src/openvpn/openvpn.h > @@ -208,6 +208,7 @@ 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/options.c b/src/openvpn/options.c > index c84b9d5e..cb25db5b 100644 > --- a/src/openvpn/options.c > +++ b/src/openvpn/options.c > @@ -7687,6 +7687,13 @@ add_option(struct options *options, > { > VERIFY_PERMISSION(OPT_P_GENERAL|OPT_P_INSTANCE); > options->ncp_ciphers = p[1]; > + > + if (!(tls_item_in_cipher_list("AES-128-GCM", options->ncp_ciphers) > + && tls_item_in_cipher_list("AES-256-GCM", options->ncp_ciphers))) > + { > + msg(M_INFO, "Not including AES-128-GCM and AES-256-GCM in ncp-ciphers " > + "disables announcing NCP support with IV_NCP=2"); > + } The condition and the text message are not agreeing with each other. How about making the if condition easier to read by applying De Morgan's law: if (!tls_item_in_cipher_list("AES-128-GCM", options->ncp_ciphers) || !tls_item_in_cipher_list("AES-256-GCM", options->ncp_ciphers))) This reads to me as: "Not enabling AES-128 or AES-256 disables NCP" (Which I think is what you wanted to express in the debug message?) What do you think? > } > else if (streq(p[0], "ncp-disable") && !p[1]) > { > diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c > index d5833ac6..f1719303 100644 > --- a/src/openvpn/ssl.c > +++ b/src/openvpn/ssl.c > @@ -2327,7 +2327,9 @@ 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 0312c1f8..133c3c22 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; > Cheers,
Hi, On Mon, Sep 23, 2019 at 03:32:24PM +0200, Arne Schwabe wrote: > + if (!(tls_item_in_cipher_list("AES-128-GCM", options->ncp_ciphers) > + && tls_item_in_cipher_list("AES-256-GCM", options->ncp_ciphers))) What about AES-192-GCM? What *exactly* does IV_NCP=2 guarantee? Can we have something nicer for cipher negotiation instead? gert
Am 23.09.19 um 16:34 schrieb Gert Doering: > Hi, > > On Mon, Sep 23, 2019 at 03:32:24PM +0200, Arne Schwabe wrote: >> + if (!(tls_item_in_cipher_list("AES-128-GCM", options->ncp_ciphers) >> + && tls_item_in_cipher_list("AES-256-GCM", options->ncp_ciphers))) > > What about AES-192-GCM? What *exactly* does IV_NCP=2 guarantee? > Our manpage says only 128 and 256 are in the default ncp-cihper list, so lets not guarantee 192. Arne
diff --git a/src/openvpn/init.c b/src/openvpn/init.c index b5a034dc..32f7bc7a 100644 --- a/src/openvpn/init.c +++ b/src/openvpn/init.c @@ -2795,6 +2795,7 @@ 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; diff --git a/src/openvpn/openvpn.h b/src/openvpn/openvpn.h index 29d21f0a..1fdbfe3c 100644 --- a/src/openvpn/openvpn.h +++ b/src/openvpn/openvpn.h @@ -208,6 +208,7 @@ 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/options.c b/src/openvpn/options.c index c84b9d5e..cb25db5b 100644 --- a/src/openvpn/options.c +++ b/src/openvpn/options.c @@ -7687,6 +7687,13 @@ add_option(struct options *options, { VERIFY_PERMISSION(OPT_P_GENERAL|OPT_P_INSTANCE); options->ncp_ciphers = p[1]; + + if (!(tls_item_in_cipher_list("AES-128-GCM", options->ncp_ciphers) + && tls_item_in_cipher_list("AES-256-GCM", options->ncp_ciphers))) + { + msg(M_INFO, "Not including AES-128-GCM and AES-256-GCM in ncp-ciphers " + "disables announcing NCP support with IV_NCP=2"); + } } else if (streq(p[0], "ncp-disable") && !p[1]) { diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c index d5833ac6..f1719303 100644 --- a/src/openvpn/ssl.c +++ b/src/openvpn/ssl.c @@ -2327,7 +2327,9 @@ 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 0312c1f8..133c3c22 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;