[Openvpn-devel,05/28] Extend tls_pre_decrypt_lite to return type of packet and keep state

diff --git a/src/openvpn/mudp.c b/src/openvpn/mudp.c
index 910268333..6dd026701 100644
--- a/src/openvpn/mudp.c
+++ b/src/openvpn/mudp.c
@@ -46,7 +46,16 @@  do_pre_decrypt_check(struct multi_context *m)
     {
         return false;
     }
-    if (!tls_pre_decrypt_lite(m->top.c2.tls_auth_standalone, &m->top.c2.from, &m->top.c2.buf))
+
+    enum first_packet_verdict verdict;
+    struct tls_pre_decrypt_state state = {0};
+
+    verdict = tls_pre_decrypt_lite(m->top.c2.tls_auth_standalone, &state,
+                                   &m->top.c2.from, &m->top.c2.buf);
+
+    free_tls_pre_decrypt_state(&state);
+
+    if (verdict == VERDICT_INVALID || verdict == VERDICT_VALID_CONTROL_V1)
     {
         return false;
     }
diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c
index f58f3b727..452433ebb 100644
--- a/src/openvpn/ssl.c
+++ b/src/openvpn/ssl.c
@@ -1367,7 +1367,6 @@  tls_multi_free(struct tls_multi *multi, bool clear)
 
 
 
-
 /*
  * Dependent on hmac size, opcode size, and session_id size.
  * Will assert if too small.
@@ -1380,10 +1379,10 @@  tls_multi_free(struct tls_multi *multi, bool clear)
  *
  * Turning the on wire format that starts with the opcode to a format
  * that starts with the hmac
- * e.g. "onwire" [opcode + packet id] [hmac] [remainder of packed]
  *
+ *    "onwire" [opcode, peer session id] [hmac, packet id] [remainder of packed]
  *
- *    "internal" [hmac] [opcode + packet id] [remainer of packet]
+ *  "internal" [hmac, packet id] [opcode, peer session id] [remainder of packet]
  *
  *  @param buf      the buffer the swap operation is executed on
  *  @param incoming determines the direction of the swap
@@ -1404,7 +1403,7 @@  swap_hmac(struct buffer *buf, const struct crypto_options *co, bool incoming)
         /* hmac + packet_id (8 bytes) */
         const int hmac_size = hmac_ctx_size(ctx->hmac) + packet_id_size(true);
 
-        /* opcode + session_id */
+        /* opcode (1 byte) + session_id (8 bytes) */
         const int osid_size = 1 + SID_SIZE;
 
         int e1, e2;
@@ -3755,6 +3754,17 @@  error:
     goto done;
 }
 
+void
+free_tls_pre_decrypt_state(struct tls_pre_decrypt_state *state)
+{
+    free_buf(&state->newbuf);
+    free_buf(&state->tls_wrap_tmp.tls_crypt_v2_metadata);
+    if (state->tls_wrap_tmp.cleanup_key_ctx)
+    {
+        free_key_ctx_bi(&state->tls_wrap_tmp.opt.key_ctx_bi);
+    }
+}
+
 /*
  * This function is similar to tls_pre_decrypt, except it is called
  * when we are in server mode and receive an initial incoming
@@ -3766,17 +3776,21 @@  error:
  * This function is essentially the first-line HMAC firewall
  * on the UDP port listener in --mode server mode.
  */
-bool
+enum first_packet_verdict
 tls_pre_decrypt_lite(const struct tls_auth_standalone *tas,
+                     struct tls_pre_decrypt_state *state,
                      const struct link_socket_actual *from,
                      const struct buffer *buf)
-
 {
-    if (buf->len <= 0)
+    struct gc_arena gc = gc_new();
+    /* A packet needs to have at least an opcode and session id */
+    if (buf->len < (1 + SID_SIZE))
     {
-        return false;
+        dmsg(D_TLS_STATE_ERRORS,
+             "TLS State Error: Too short packet (length  %d) received from %s",
+             buf->len, print_link_socket_actual(from, &gc));
+        goto error;
     }
-    struct gc_arena gc = gc_new();
 
     /* get opcode and key ID */
     uint8_t pkt_firstbyte = *BPTR(buf);
@@ -3786,8 +3800,10 @@  tls_pre_decrypt_lite(const struct tls_auth_standalone *tas,
     /* this packet is from an as-yet untrusted source, so
      * scrutinize carefully */
 
+    /* Allow only the reset packet or the first packet of the actual handshake. */
     if (op != P_CONTROL_HARD_RESET_CLIENT_V2
-        && op != P_CONTROL_HARD_RESET_CLIENT_V3)
+        && op != P_CONTROL_HARD_RESET_CLIENT_V3
+        && op != P_CONTROL_V1)
     {
         /*
          * This can occur due to bogus data or DoS packets.
@@ -3808,17 +3824,28 @@  tls_pre_decrypt_lite(const struct tls_auth_standalone *tas,
         goto error;
     }
 
-    struct buffer newbuf = clone_buf(buf);
-    struct tls_wrap_ctx tls_wrap_tmp = tas->tls_wrap;
-
-    /* HMAC test, if --tls-auth was specified */
-    bool status = read_control_auth(&newbuf, &tls_wrap_tmp, from, NULL);
-    free_buf(&newbuf);
-    free_buf(&tls_wrap_tmp.tls_crypt_v2_metadata);
-    if (tls_wrap_tmp.cleanup_key_ctx)
+    /* read peer session id, we do this at this point since
+     * read_control_auth will skip over it */
+    struct buffer tmp = *buf;
+    buf_advance(&tmp, 1);
+    if (!session_id_read(&state->peer_session_id, &tmp)
+        || !session_id_defined(&state->peer_session_id))
     {
-        free_key_ctx_bi(&tls_wrap_tmp.opt.key_ctx_bi);
+        msg(D_TLS_ERRORS,
+            "TLS Error: session-id not found in packet from %s",
+            print_link_socket_actual(from, &gc));
+        goto error;
     }
+
+    state->newbuf = clone_buf(buf);
+    state->tls_wrap_tmp = tas->tls_wrap;
+
+    /* HMAC test and unwrapping the encrypted part of the control message
+     * into newbuf or just setting newbuf to point to the start of control
+     * message */
+    bool status = read_control_auth(&state->newbuf, &state->tls_wrap_tmp,
+                                    from, NULL);
+
     if (!status)
     {
         goto error;
@@ -3840,12 +3867,19 @@  tls_pre_decrypt_lite(const struct tls_auth_standalone *tas,
      * of authentication solely up to TLS.
      */
     gc_free(&gc);
-    return true;
+    if (op == P_CONTROL_V1)
+    {
+        return VERDICT_VALID_CONTROL_V1;
+    }
+    else
+    {
+        return VERDICT_VALID_RESET;
+    }
 
 error:
     tls_clear_error();
     gc_free(&gc);
-    return false;
+    return VERDICT_INVALID;
 }
 
 struct key_state *
diff --git a/src/openvpn/ssl.h b/src/openvpn/ssl.h
index 5b9232006..d72bf3c50 100644
--- a/src/openvpn/ssl.h
+++ b/src/openvpn/ssl.h
@@ -323,6 +323,33 @@  bool tls_pre_decrypt(struct tls_multi *multi,
 /** @name Functions for managing security parameter state for data channel packets
  *  @{ */
 
+
+enum first_packet_verdict {
+    /** This packet is a valid reset packet from the peer */
+    VERDICT_VALID_RESET,
+    /** This packet is a valid control packet from the peer,
+     * i.e. it has a valid session id hmac in it */
+    VERDICT_VALID_CONTROL_V1,
+    /** the packet failed on of the various checks */
+    VERDICT_INVALID
+};
+
+/**
+ * struct that stores the temporary data for the tls lite decrypt
+ * functions
+ */
+struct tls_pre_decrypt_state {
+    struct tls_wrap_ctx tls_wrap_tmp;
+    struct buffer newbuf;
+    struct session_id peer_session_id;
+};
+
+/**
+ *
+ * @param state
+ */
+void free_tls_pre_decrypt_state(struct tls_pre_decrypt_state *state);
+
 /**
  * Inspect an incoming packet for which no VPN tunnel is active, and
  * determine whether a new VPN tunnel should be created.
@@ -343,6 +370,8 @@  bool tls_pre_decrypt(struct tls_multi *multi,
  * whether a new VPN tunnel should be created.  If so, that new VPN tunnel
  * instance will handle processing of the packet.
  *
+ * This function is only used in the UDP p2mp server code path
+ *
  * @param tas - The standalone TLS authentication setting structure for
  *     this process.
  * @param from - The source address of the packet.
@@ -354,9 +383,11 @@  bool tls_pre_decrypt(struct tls_multi *multi,
  * @li False if the packet is not valid, did not pass the HMAC firewall
  *     test, or some other error occurred.
  */
-bool tls_pre_decrypt_lite(const struct tls_auth_standalone *tas,
-                          const struct link_socket_actual *from,
-                          const struct buffer *buf);
+enum first_packet_verdict
+tls_pre_decrypt_lite(const struct tls_auth_standalone *tas,
+                     struct tls_pre_decrypt_state *state,
+                     const struct link_socket_actual *from,
+                     const struct buffer *buf);
 
 
 /**