Add --ncp-disable to completely disable cipher negotiation, and
--ncp-ciphers to specify which ciphers to accept from the server.
v2:
* fix --disable-crypto builds
* use register_signal() instead of operating directly on c->sig
* add man-page entry for new options
Signed-off-by: Steffan Karger <stef...@karger.me>
restrict man fix
---
doc/openvpn.8 | 13 +++++++++++++
src/openvpn/init.c | 36 ++++++++++++++++++++++++++++++------
src/openvpn/init.h | 4 ++--
src/openvpn/openvpn.h | 3 +++
src/openvpn/options.c | 40 +++++++++++++++++++++++++++++-----------
src/openvpn/options.h | 4 +++-
src/openvpn/push.c | 11 ++++++++++-
src/openvpn/ssl.c | 30 +++++++++++++++++++++++++++++-
src/openvpn/ssl_common.h | 4 ++++
9 files changed, 123 insertions(+), 22 deletions(-)
diff --git a/doc/openvpn.8 b/doc/openvpn.8
index 03f31bb..e349b77 100644
--- a/doc/openvpn.8
+++ b/doc/openvpn.8
@@ -4128,6 +4128,19 @@ Set
to disable encryption.
.\"*********************************************************
.TP
+.B \-\-ncp\-ciphers cipher_list
+Restrict the allowed ciphers to be negotiated to the ciphers in
+.B cipher_list\fR.
+.B cipher_list
+is a colon-separated list of ciphers, and defaults to
+"AES-256-GCM:AES-128-GCM".
+.\"*********************************************************
+.TP
+.B \-\-ncp\-disable
+Disable "negotiable crypto parameters". This completely disables cipher
+negotiation.
+.\"*********************************************************
+.TP
.B \-\-keysize n
Size of cipher key in bits (optional).
If unspecified, defaults to cipher-specific default. The
diff --git a/src/openvpn/init.c b/src/openvpn/init.c
index 8f81b09..c2e3b2e 100644
--- a/src/openvpn/init.c
+++ b/src/openvpn/init.c
@@ -1739,7 +1739,7 @@ options_hash_changed_or_zero(const struct md5_digest *a,
}
#endif /* P2MP */
-void
+bool
do_up (struct context *c, bool pulled_options, unsigned int option_types_found)
{
if (!c->c2.do_up_ran)
@@ -1747,7 +1747,13 @@ do_up (struct context *c, bool pulled_options, unsigned
int option_types_found)
reset_coarse_timers (c);
if (pulled_options && option_types_found)
- do_deferred_options (c, option_types_found);
+ {
+ if (!do_deferred_options (c, option_types_found))
+ {
+ msg (D_PUSH_ERRORS, "ERROR: Failed to apply push options");
+ return false;
+ }
+ }
/* if --up-delay specified, open tun, do ifconfig, and run up script now
*/
if (c->options.up_delay || PULL_DEFINED (&c->options))
@@ -1802,6 +1808,7 @@ do_up (struct context *c, bool pulled_options, unsigned
int option_types_found)
c->c2.do_up_ran = true;
}
+ return true;
}
/*
@@ -1819,7 +1826,6 @@ pull_permission_mask (const struct context *c)
| OPT_P_SHAPER
| OPT_P_TIMER
| OPT_P_COMP
- | OPT_P_CRYPTO
| OPT_P_PERSIST
| OPT_P_MESSAGES
| OPT_P_EXPLICIT_NOTIFY
@@ -1830,13 +1836,18 @@ pull_permission_mask (const struct context *c)
if (!c->options.route_nopull)
flags |= (OPT_P_ROUTE | OPT_P_IPWIN32);
+#ifdef ENABLE_CRYPTO
+ if (c->options.ncp_enabled)
+ flags |= OPT_P_NCP;
+#endif
+
return flags;
}
/*
* Handle non-tun-related pulled options.
*/
-void
+bool
do_deferred_options (struct context *c, const unsigned int found)
{
if (found & OPT_P_MESSAGES)
@@ -1927,10 +1938,17 @@ do_deferred_options (struct context *c, const unsigned
int found)
/* process (potenitally pushed) crypto options */
if (c->options.pull)
{
- tls_session_update_crypto_params(&c->c2.tls_multi->session[TM_ACTIVE],
- &c->options, &c->c2.frame);
+ if (found & OPT_P_NCP)
+ msg (D_PUSH, "OPTIONS IMPORT: data channel crypto options modified");
+ if (!tls_session_update_crypto_params(
+ &c->c2.tls_multi->session[TM_ACTIVE], &c->options, &c->c2.frame))
+ {
+ msg (D_TLS_ERRORS, "OPTIONS ERROR: failed to import crypto options");
+ return false;
+ }
}
#endif
+ return true;
}
/*
@@ -2250,6 +2268,9 @@ do_init_crypto_tls_c1 (struct context *c)
&c->c1.ks.tls_auth_key, file, options->key_direction, flags);
}
+ c->c1.ciphername = options->ciphername;
+ c->c1.authname = options->authname;
+
#if 0 /* was: #if ENABLE_INLINE_FILES -- Note that enabling this code will
break restarts */
if (options->priv_key_file_inline)
{
@@ -2326,6 +2347,9 @@ do_init_crypto_tls (struct context *c, const unsigned int
flags)
to.replay_window = options->replay_window;
to.replay_time = options->replay_time;
to.tcp_mode = link_socket_proto_connection_oriented (options->ce.proto);
+ to.config_ciphername = c->c1.ciphername;
+ to.config_authname = c->c1.authname;
+ to.ncp_enabled = options->ncp_enabled;
to.transition_window = options->transition_window;
to.handshake_window = options->handshake_window;
to.packet_timeout = options->tls_timeout;
diff --git a/src/openvpn/init.h b/src/openvpn/init.h
index a819bd2..524bc64 100644
--- a/src/openvpn/init.h
+++ b/src/openvpn/init.h
@@ -81,7 +81,7 @@ bool do_test_crypto (const struct options *o);
void context_gc_free (struct context *c);
-void do_up (struct context *c,
+bool do_up (struct context *c,
bool pulled_options,
unsigned int option_types_found);
@@ -91,7 +91,7 @@ const char *format_common_name (struct context *c, struct
gc_arena *gc);
void reset_coarse_timers (struct context *c);
-void do_deferred_options (struct context *c, const unsigned int found);
+bool do_deferred_options (struct context *c, const unsigned int found);
void inherit_context_child (struct context *dest,
const struct context *src);
diff --git a/src/openvpn/openvpn.h b/src/openvpn/openvpn.h
index 3281fd7..395195f 100644
--- a/src/openvpn/openvpn.h
+++ b/src/openvpn/openvpn.h
@@ -210,6 +210,9 @@ struct context_1
struct user_pass *auth_user_pass;
/**< Username and password for
* authentication. */
+
+ const char *ciphername; /**< Data channel cipher from config file */
+ const char *authname; /**< Data channel auth from config file
*/
#endif
};
diff --git a/src/openvpn/options.c b/src/openvpn/options.c
index a595dff..d17a2ce 100644
--- a/src/openvpn/options.c
+++ b/src/openvpn/options.c
@@ -523,6 +523,8 @@ static const char usage_message[] =
"--cipher alg : Encrypt packets with cipher algorithm alg\n"
" (default=%s).\n"
" Set alg=none to disable encryption.\n"
+ "--ncp-ciphers list : List of ciphers that are allowed to be negotiated.\n"
+ "--ncp-disable : Disable cipher negotiation.\n"
"--prng alg [nsl] : For PRNG, use digest algorithm alg, and\n"
" nonce_secret_len=nsl. Set alg=none to disable PRNG.\n"
#ifdef HAVE_EVP_CIPHER_CTX_SET_KEY_LENGTH
@@ -830,6 +832,12 @@ init_options (struct options *o, const bool init_gc)
#ifdef ENABLE_CRYPTO
o->ciphername = "BF-CBC";
o->ciphername_defined = true;
+#ifdef HAVE_AEAD_CIPHER_MODES /* IV_NCP=2 requires GCM support */
+ o->ncp_enabled = true;
+#else
+ o->ncp_enabled = false;
+#endif
+ o->ncp_ciphers = "AES-256-GCM:AES-128-GCM";
o->authname = "SHA1";
o->authname_defined = true;
o->prng_hash = "SHA1";
@@ -6632,7 +6640,7 @@ add_option (struct options *options,
}
else if (streq (p[0], "auth") && p[1] && !p[2])
{
- VERIFY_PERMISSION (OPT_P_CRYPTO);
+ VERIFY_PERMISSION (OPT_P_GENERAL);
options->authname_defined = true;
options->authname = p[1];
if (streq (options->authname, "none"))
@@ -6643,12 +6651,12 @@ add_option (struct options *options,
}
else if (streq (p[0], "auth") && !p[1])
{
- VERIFY_PERMISSION (OPT_P_CRYPTO);
+ VERIFY_PERMISSION (OPT_P_GENERAL);
options->authname_defined = true;
}
else if (streq (p[0], "cipher") && p[1] && !p[2])
{
- VERIFY_PERMISSION (OPT_P_CRYPTO);
+ VERIFY_PERMISSION (OPT_P_NCP);
options->ciphername_defined = true;
options->ciphername = p[1];
if (streq (options->ciphername, "none"))
@@ -6659,12 +6667,22 @@ add_option (struct options *options,
}
else if (streq (p[0], "cipher") && !p[1])
{
- VERIFY_PERMISSION (OPT_P_CRYPTO);
+ VERIFY_PERMISSION (OPT_P_GENERAL);
options->ciphername_defined = true;
}
+ else if (streq (p[0], "ncp-ciphers") && p[1] && !p[2])
+ {
+ VERIFY_PERMISSION (OPT_P_GENERAL);
+ options->ncp_ciphers = p[1];
+ }
+ else if (streq (p[0], "ncp-disable") && !p[1])
+ {
+ VERIFY_PERMISSION (OPT_P_GENERAL);
+ options->ncp_enabled = false;
+ }
else if (streq (p[0], "prng") && p[1] && !p[3])
{
- VERIFY_PERMISSION (OPT_P_CRYPTO);
+ VERIFY_PERMISSION (OPT_P_GENERAL);
if (streq (p[1], "none"))
options->prng_hash = NULL;
else
@@ -6686,12 +6704,12 @@ add_option (struct options *options,
}
else if (streq (p[0], "no-replay") && !p[1])
{
- VERIFY_PERMISSION (OPT_P_CRYPTO);
+ VERIFY_PERMISSION (OPT_P_GENERAL);
options->replay = false;
}
else if (streq (p[0], "replay-window") && !p[3])
{
- VERIFY_PERMISSION (OPT_P_CRYPTO);
+ VERIFY_PERMISSION (OPT_P_GENERAL);
if (p[1])
{
int replay_window;
@@ -6731,12 +6749,12 @@ add_option (struct options *options,
}
else if (streq (p[0], "mute-replay-warnings") && !p[1])
{
- VERIFY_PERMISSION (OPT_P_CRYPTO);
+ VERIFY_PERMISSION (OPT_P_GENERAL);
options->mute_replay_warnings = true;
}
else if (streq (p[0], "no-iv") && !p[1])
{
- VERIFY_PERMISSION (OPT_P_CRYPTO);
+ VERIFY_PERMISSION (OPT_P_GENERAL);
options->use_iv = false;
}
else if (streq (p[0], "replay-persist") && p[1] && !p[2])
@@ -6766,7 +6784,7 @@ add_option (struct options *options,
{
int keysize;
- VERIFY_PERMISSION (OPT_P_CRYPTO);
+ VERIFY_PERMISSION (OPT_P_NCP);
keysize = atoi (p[1]) / 8;
if (keysize < 0 || keysize > MAX_CIPHER_KEY_LENGTH)
{
@@ -6795,7 +6813,7 @@ add_option (struct options *options,
}
else if (streq (p[0], "ecdh-curve") && p[1] && !p[2])
{
- VERIFY_PERMISSION (OPT_P_CRYPTO);
+ VERIFY_PERMISSION (OPT_P_GENERAL);
options->ecdh_curve= p[1];
}
else if (streq (p[0], "tls-server") && !p[1])
diff --git a/src/openvpn/options.h b/src/openvpn/options.h
index 514511b..ea63c4c 100644
--- a/src/openvpn/options.h
+++ b/src/openvpn/options.h
@@ -474,6 +474,8 @@ struct options
int key_direction;
bool ciphername_defined;
const char *ciphername;
+ bool ncp_enabled;
+ const char *ncp_ciphers;
bool authname_defined;
const char *authname;
int keysize;
@@ -618,7 +620,7 @@ struct options
#define OPT_P_PERSIST_IP (1<<9)
#define OPT_P_COMP (1<<10) /* TODO */
#define OPT_P_MESSAGES (1<<11)
-#define OPT_P_CRYPTO (1<<12) /* TODO */
+#define OPT_P_NCP (1<<12) /**< Negotiable crypto parameters */
#define OPT_P_TLS_PARMS (1<<13) /* TODO */
#define OPT_P_MTU (1<<14) /* TODO */
#define OPT_P_NICE (1<<15)
diff --git a/src/openvpn/push.c b/src/openvpn/push.c
index 38ac59e..4239e3e 100644
--- a/src/openvpn/push.c
+++ b/src/openvpn/push.c
@@ -239,11 +239,20 @@ incoming_push_message (struct context *c, const struct
buffer *buffer)
{
c->options.push_option_types_found |= option_types_found;
+ /* delay bringing tun/tap up until --push parms received from remote */
if (status == PUSH_MSG_REPLY)
- do_up (c, true, c->options.push_option_types_found ); /* delay bringing
tun/tap up until --push parms received from remote */
+ {
+ if (!do_up (c, true, c->options.push_option_types_found))
+ {
+ msg (D_PUSH_ERRORS, "Failed to open tun/tap interface");
+ register_signal (c, SIGUSR1, "do_up-failed");
+ goto cleanup;
+ }
+ }
event_timeout_clear (&c->c2.push_request_interval);
}
+cleanup:
gc_free (&gc);
}
diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c
index 0c0061c..7ced41d 100644
--- a/src/openvpn/ssl.c
+++ b/src/openvpn/ssl.c
@@ -1636,6 +1636,24 @@ key_ctx_update_implicit_iv(struct key_ctx *ctx, uint8_t
*key, size_t key_len) {
}
}
+static bool
+item_in_list(const char *item, const char *list)
+{
+ char *tmp_ciphers = string_alloc (list, NULL);
+ char *tmp_ciphers_orig = tmp_ciphers;
+
+ const char *token = strtok (tmp_ciphers, ":");
+ while(token)
+ {
+ if (0 == strcmp (token, item))
+ break;
+ token = strtok (NULL, ":");
+ }
+ free(tmp_ciphers_orig);
+
+ return token != NULL;
+}
+
bool
tls_session_update_crypto_params(struct tls_session *session,
const struct options *options, struct frame *frame)
@@ -1646,6 +1664,15 @@ tls_session_update_crypto_params(struct tls_session
*session,
ASSERT (!session->opt->server);
ASSERT (ks->authenticated);
+ if (0 != strcmp(options->ciphername, session->opt->config_ciphername) &&
+ !item_in_list(options->ciphername, options->ncp_ciphers))
+ {
+ msg (D_TLS_ERRORS, "Error: pushed cipher not allowed - %s not in %s or
%s",
+ options->ciphername, session->opt->config_ciphername,
+ options->ncp_ciphers);
+ return false;
+ }
+
init_key_type (&session->opt->key_type, options->ciphername,
options->ciphername_defined, options->authname, options->authname_defined,
options->keysize, true, true);
@@ -1927,7 +1954,8 @@ push_peer_info(struct buffer *buf, struct tls_session
*session)
buf_printf(&out, "IV_PROTO=2\n");
/* support for Negotiable Crypto Paramters */
- buf_printf(&out, "IV_NCP=2\n");
+ if (session->opt->ncp_enabled)
+ buf_printf(&out, "IV_NCP=2\n");
/* push compression status */
#ifdef USE_COMP
diff --git a/src/openvpn/ssl_common.h b/src/openvpn/ssl_common.h
index 9183dab..6bfde6b 100644
--- a/src/openvpn/ssl_common.h
+++ b/src/openvpn/ssl_common.h
@@ -273,6 +273,10 @@ struct tls_options
int replay_time; /* --replay-window parm */
bool tcp_mode;
+ const char *config_ciphername;
+ const char *config_authname;
+ bool ncp_enabled;
+
/* packet authentication for TLS handshake */
struct crypto_options tls_auth;
--
2.7.4
