tor

commit 789beca7831253737ea91bd3ab516a581051fa4d
parent 86fdddccb27f15edcfd49038c87a0f66c11fb52e
Author: David Goulet <dgoulet@torproject.org>
Date:   Mon,  6 Jul 2020 08:45:12 -0400

channel: Refactor NETINFO process function

In order to process a NETINFO cell, the OR connection needs to go through a
series of validation else we don't process the cell.

Move those into its own function in and improve documentation.

This is an attempt at reducing technical debt of the rather large and
complicated channel_tls_process_netinfo_cell() function.

Related to #40022

Signed-off-by: David Goulet <dgoulet@torproject.org>

Diffstat:
M
src/core/or/channeltls.c
 | 
51
+++++++++++++++++++++++++++++++++++++++------------

1 file changed, 39 insertions(+), 12 deletions(-)
diff --git a/src/core/or/channeltls.c b/src/core/or/channeltls.c
@@ -1688,6 +1688,41 @@ time_abs(time_t val)
   return (val < 0) ? -val : val;
 }
 
+/** Return true iff the channel can process a NETINFO cell. For this to return
+ * true, these channel conditions apply:
+ *
+ *    1. Link protocol is version 2 or higher (tor-spec.txt, NETINFO cells
+ *       section).
+ *
+ *    2. Underlying OR connection of the channel is either in v2 or v3
+ *       handshaking state.
+ */
+static bool
+can_process_netinfo_cell(const channel_tls_t *chan)
+{
+  /* NETINFO cells can only be negotiated on link protocol 2 or higher. */
+  if (chan->conn->link_proto < 2) {
+    log_fn(LOG_PROTOCOL_WARN, LD_OR,
+           "Received a NETINFO cell on %s connection; dropping.",
+           chan->conn->link_proto == 0 ? "non-versioned" : "a v1");
+    return false;
+  }
+
+  /* Can't process a NETINFO cell if the connection is not handshaking. */
+  if (chan->conn->base_.state != OR_CONN_STATE_OR_HANDSHAKING_V2 &&
+      chan->conn->base_.state != OR_CONN_STATE_OR_HANDSHAKING_V3) {
+    log_fn(LOG_PROTOCOL_WARN, LD_OR,
+           "Received a NETINFO cell on non-handshaking connection; dropping.");
+    return false;
+  }
+
+  /* Make sure we do have handshake state. */
+  tor_assert(chan->conn->handshake_state);
+  tor_assert(chan->conn->handshake_state->received_versions);
+
+  return true;
+}
+
 /**
  * Process a 'netinfo' cell
  *
@@ -1713,20 +1748,12 @@ channel_tls_process_netinfo_cell(cell_t *cell, channel_tls_t *chan)
   tor_assert(chan);
   tor_assert(chan->conn);
 
-  if (chan->conn->link_proto < 2) {
-    log_fn(LOG_PROTOCOL_WARN, LD_OR,
-           "Received a NETINFO cell on %s connection; dropping.",
-           chan->conn->link_proto == 0 ? "non-versioned" : "a v1");
+  /* Make sure we can process a NETINFO cell. Link protocol and state
+   * validation is done to make sure of it. */
+  if (!can_process_netinfo_cell(chan)) {
     return;
   }
-  if (chan->conn->base_.state != OR_CONN_STATE_OR_HANDSHAKING_V2 &&
-      chan->conn->base_.state != OR_CONN_STATE_OR_HANDSHAKING_V3) {
-    log_fn(LOG_PROTOCOL_WARN, LD_OR,
-           "Received a NETINFO cell on non-handshaking connection; dropping.");
-    return;
-  }
-  tor_assert(chan->conn->handshake_state &&
-             chan->conn->handshake_state->received_versions);
+
   started_here = connection_or_nonopen_was_started_here(chan->conn);
   identity_digest = chan->conn->identity_digest;