[Openvpn-devel,11/28] Refactor tls-auth/tls-crypt wrapping into into own function

Message ID 20220422142953.3805364-2-arne@rfc2549.org
State Accepted
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Series
  • Stateless three-way handshake and control channel improvements
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Commit Message

Arne Schwabe April 22, 2022, 2:29 p.m.
This allows the the wrapping to be easier reused by a function that
does not have access to a full TLS session.
---
 src/openvpn/ssl_pkt.c | 82 ++++++++++++++++++++++++++-----------------
 1 file changed, 50 insertions(+), 32 deletions(-)

Comments

Frank Lichtenheld April 26, 2022, 9:23 a.m. | #1
Acked-By: Frank Lichtenheld <frank@lichtenheld.com>

Verified visually that this only moves code around and doesn't change behavior.
Only compile/UT tested.

> Arne Schwabe <arne@rfc2549.org> hat am 22.04.2022 16:29 geschrieben:
> 
>  
> This allows the the wrapping to be easier reused by a function that
> does not have access to a full TLS session.
> ---
>  src/openvpn/ssl_pkt.c | 82 ++++++++++++++++++++++++++-----------------
>  1 file changed, 50 insertions(+), 32 deletions(-)

Regards,
--
Frank Lichtenheld
Gert Doering April 26, 2022, 9:57 a.m. | #2
I've done a bit of "extra eyes stare at the code" and things look good
(due to the newly named options, git is not that helpful in confirming
"it's all the same code").  Will test together with 12.

Your patch has been applied to the master branch.

commit 9bbebf100a07f4dca3f088dce19cd87608e82b4c
Author: Arne Schwabe
Date:   Fri Apr 22 16:29:36 2022 +0200

     Refactor tls-auth/tls-crypt wrapping into into own function

     Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
     Message-Id: <20220422142953.3805364-2-arne@rfc2549.org>
     URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg24150.html
     Signed-off-by: Gert Doering <gert@greenie.muc.de>


--
kind regards,

Gert Doering

Patch

diff --git a/src/openvpn/ssl_pkt.c b/src/openvpn/ssl_pkt.c
index e8cc7dee9..86c1f0e29 100644
--- a/src/openvpn/ssl_pkt.c
+++ b/src/openvpn/ssl_pkt.c
@@ -110,51 +110,48 @@  swap_hmac(struct buffer *buf, const struct crypto_options *co, bool incoming)
 
 #undef SWAP_BUF_SIZE
 
-void
-write_control_auth(struct tls_session *session,
-                   struct key_state *ks,
-                   struct buffer *buf,
-                   struct link_socket_actual **to_link_addr,
-                   int opcode,
-                   int max_ack,
-                   bool prepend_ack)
+/**
+ * Wraps a TLS control packet by adding tls-auth HMAC or tls-crypt(-v2)
+ * encryption and opcode header including session id.
+ *
+ * @param ctx           tls wrapping context
+ * @param header        first byte of the packet (opcode and key id)
+ * @param buf           buffer to write the resulting packet to
+ * @param session_id    session id to use as our session id
+ */
+static void
+tls_wrap_control(struct tls_wrap_ctx *ctx, uint8_t header, struct buffer *buf,
+                 struct session_id *session_id)
 {
-    uint8_t header = ks->key_id | (opcode << P_OPCODE_SHIFT);
-    struct buffer null = clear_buf();
-
-    ASSERT(link_socket_actual_defined(&ks->remote_addr));
-    ASSERT(reliable_ack_write
-               (ks->rec_ack, buf, &ks->session_id_remote, max_ack, prepend_ack));
-
-    msg(D_TLS_DEBUG, "%s(): %s", __func__, packet_opcode_name(opcode));
-
-    if (session->tls_wrap.mode == TLS_WRAP_AUTH
-        || session->tls_wrap.mode == TLS_WRAP_NONE)
+    if (ctx->mode == TLS_WRAP_AUTH
+        || ctx->mode == TLS_WRAP_NONE)
     {
-        ASSERT(session_id_write_prepend(&session->session_id, buf));
+        ASSERT(session_id_write_prepend(session_id, buf));
         ASSERT(buf_write_prepend(buf, &header, sizeof(header)));
     }
-    if (session->tls_wrap.mode == TLS_WRAP_AUTH)
+    if (ctx->mode == TLS_WRAP_AUTH)
     {
+        struct buffer null = clear_buf();
+
         /* no encryption, only write hmac */
-        openvpn_encrypt(buf, null, &session->tls_wrap.opt);
-        ASSERT(swap_hmac(buf, &session->tls_wrap.opt, false));
+        openvpn_encrypt(buf, null, &ctx->opt);
+        ASSERT(swap_hmac(buf, &ctx->opt, false));
     }
-    else if (session->tls_wrap.mode == TLS_WRAP_CRYPT)
+    else if (ctx->mode == TLS_WRAP_CRYPT)
     {
-        ASSERT(buf_init(&session->tls_wrap.work, buf->offset));
-        ASSERT(buf_write(&session->tls_wrap.work, &header, sizeof(header)));
-        ASSERT(session_id_write(&session->session_id, &session->tls_wrap.work));
-        if (!tls_crypt_wrap(buf, &session->tls_wrap.work, &session->tls_wrap.opt))
+        ASSERT(buf_init(&ctx->work, buf->offset));
+        ASSERT(buf_write(&ctx->work, &header, sizeof(header)));
+        ASSERT(session_id_write(session_id, &ctx->work));
+        if (!tls_crypt_wrap(buf, &ctx->work, &ctx->opt))
         {
             buf->len = 0;
             return;
         }
 
-        if (opcode == P_CONTROL_HARD_RESET_CLIENT_V3)
+        if ((header >> P_OPCODE_SHIFT) == P_CONTROL_HARD_RESET_CLIENT_V3)
         {
-            if (!buf_copy(&session->tls_wrap.work,
-                          session->tls_wrap.tls_crypt_v2_wkc))
+            if (!buf_copy(&ctx->work,
+                          ctx->tls_crypt_v2_wkc))
             {
                 msg(D_TLS_ERRORS, "Could not append tls-crypt-v2 client key");
                 buf->len = 0;
@@ -164,8 +161,29 @@  write_control_auth(struct tls_session *session,
 
         /* Don't change the original data in buf, it's used by the reliability
          * layer to resend on failure. */
-        *buf = session->tls_wrap.work;
+        *buf = ctx->work;
     }
+}
+
+void
+write_control_auth(struct tls_session *session,
+                   struct key_state *ks,
+                   struct buffer *buf,
+                   struct link_socket_actual **to_link_addr,
+                   int opcode,
+                   int max_ack,
+                   bool prepend_ack)
+{
+    uint8_t header = ks->key_id | (opcode << P_OPCODE_SHIFT);
+
+    ASSERT(link_socket_actual_defined(&ks->remote_addr));
+    ASSERT(reliable_ack_write
+               (ks->rec_ack, buf, &ks->session_id_remote, max_ack, prepend_ack));
+
+    msg(D_TLS_DEBUG, "%s(): %s", __func__, packet_opcode_name(opcode));
+
+    tls_wrap_control(&session->tls_wrap, header, buf, &session->session_id);
+
     *to_link_addr = &ks->remote_addr;
 }