[Openvpn-devel,v3,1/5] Extract update_session_cipher into standalone function

Message ID 20220625234150.3398864-1-arne@rfc2549.org
State Superseded
Headers show
Series [Openvpn-devel,v3,1/5] Extract update_session_cipher into standalone function | expand

Commit Message

Arne Schwabe June 25, 2022, 11:41 p.m. UTC
This allow the code later to check if the cipher is okay to use and
update it for the calculation for the max MTU size.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
---
 src/openvpn/ssl.c     | 11 +----------
 src/openvpn/ssl_ncp.c | 22 ++++++++++++++++++++++
 src/openvpn/ssl_ncp.h |  8 ++++++++
 3 files changed, 31 insertions(+), 10 deletions(-)

Comments

Gert Doering July 27, 2022, 6:58 p.m. UTC | #1
Hi,

On Sun, Jun 26, 2022 at 01:41:46AM +0200, Arne Schwabe wrote:
> +
> +/**
> + * Checks if the cipher is allowed and updates the TLS session cipher with it,
> + * otherwise returns false
> + */
> +bool
> +update_session_cipher(struct tls_session *session, struct options *options);
> +

Is that comment correct?  I can't find any "updating" here, only "checking".

What am I overlooking?

gert
Arne Schwabe July 28, 2022, 1:47 p.m. UTC | #2
Am 27.07.22 um 20:58 schrieb Gert Doering:
> Hi,
> 
> On Sun, Jun 26, 2022 at 01:41:46AM +0200, Arne Schwabe wrote:
>> +
>> +/**
>> + * Checks if the cipher is allowed and updates the TLS session cipher with it,
>> + * otherwise returns false
>> + */
>> +bool
>> +update_session_cipher(struct tls_session *session, struct options *options);
>> +
> 
> Is that comment correct?  I can't find any "updating" here, only "checking".
> 
> What am I overlooking?
>

It sets options->cipher sometimes but the name is misleading. I will 
rename to check_session_cipher

Arne
Gert Doering July 28, 2022, 1:51 p.m. UTC | #3
Hi,

On Thu, Jul 28, 2022 at 03:47:53PM +0200, Arne Schwabe wrote:
> > Is that comment correct?  I can't find any "updating" here, only "checking".
> > 
> > What am I overlooking?
> 
> It sets options->cipher sometimes but the name is misleading. I will 
> rename to check_session_cipher

The "options->cipher setting" part is more "restore to config if
requested cipher is not allowed" - so that one I understood ;-)

gert

Patch

diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c
index 61dea996d..ddd90080b 100644
--- a/src/openvpn/ssl.c
+++ b/src/openvpn/ssl.c
@@ -1678,17 +1678,8 @@  tls_session_update_crypto_params(struct tls_session *session,
                                  struct frame *frame_fragment,
                                  struct link_socket_info *lsi)
 {
-
-    bool cipher_allowed_as_fallback = options->enable_ncp_fallback
-                                      && streq(options->ciphername, session->opt->config_ciphername);
-
-    if (!session->opt->server && !cipher_allowed_as_fallback
-        && !tls_item_in_cipher_list(options->ciphername, options->ncp_ciphers))
+    if (!update_session_cipher(session, options))
     {
-        msg(D_TLS_ERRORS, "Error: negotiated cipher not allowed - %s not in %s",
-            options->ciphername, options->ncp_ciphers);
-        /* undo cipher push, abort connection setup */
-        options->ciphername = session->opt->config_ciphername;
         return false;
     }
 
diff --git a/src/openvpn/ssl_ncp.c b/src/openvpn/ssl_ncp.c
index 564942503..c800f718f 100644
--- a/src/openvpn/ssl_ncp.c
+++ b/src/openvpn/ssl_ncp.c
@@ -490,3 +490,25 @@  p2p_mode_ncp(struct tls_multi *multi, struct tls_session *session)
 
     gc_free(&gc);
 }
+
+
+bool
+update_session_cipher(struct tls_session *session, struct options *options)
+{
+    bool cipher_allowed_as_fallback = options->enable_ncp_fallback
+                                      && streq(options->ciphername, session->opt->config_ciphername);
+
+    if (!session->opt->server && !cipher_allowed_as_fallback
+        && !tls_item_in_cipher_list(options->ciphername, options->ncp_ciphers))
+    {
+        msg(D_TLS_ERRORS, "Error: negotiated cipher not allowed - %s not in %s",
+            options->ciphername, options->ncp_ciphers);
+        /* undo cipher push, abort connection setup */
+        options->ciphername = session->opt->config_ciphername;
+        return false;
+    }
+    else
+    {
+        return true;
+    }
+}
diff --git a/src/openvpn/ssl_ncp.h b/src/openvpn/ssl_ncp.h
index 853017f5f..5ba2f7ae7 100644
--- a/src/openvpn/ssl_ncp.h
+++ b/src/openvpn/ssl_ncp.h
@@ -148,4 +148,12 @@  const char *
 get_p2p_ncp_cipher(struct tls_session *session, const char *peer_info,
                    struct gc_arena *gc);
 
+
+/**
+ * Checks if the cipher is allowed and updates the TLS session cipher with it,
+ * otherwise returns false
+ */
+bool
+update_session_cipher(struct tls_session *session, struct options *options);
+
 #endif /* ifndef OPENVPN_SSL_NCP_H */