[tor-commits] [tor/release-0.3.4] Bug 26214: Check stream SENDME against max.

[nickm at torproject.org]

commit dc397f9a61e2e2caeea1acd46beab0e7205eaa9f
Author: Mike Perry <mikeperry-git at torproject.org>
Date:   Sun May 27 01:42:35 2018 +0000

    Bug 26214: Check stream SENDME against max.
---
 src/or/or.h    |  1 +
 src/or/relay.c | 24 ++++++++++++++++++++++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/or/or.h b/src/or/or.h
index e106ec66f..db8f9544f 100644
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -929,6 +929,7 @@ typedef enum {
 /** Initial value on both sides of a stream transmission window when the
  * stream is initialized.  Measured in cells. */
 #define STREAMWINDOW_START 500
+#define STREAMWINDOW_START_MAX 500
 /** Amount to increment a stream window when we get a stream SENDME. */
 #define STREAMWINDOW_INCREMENT 50
 
diff --git a/src/or/relay.c b/src/or/relay.c
index 50f59d6b9..3632678af 100644
--- a/src/or/relay.c
+++ b/src/or/relay.c
@@ -1752,8 +1752,7 @@ connection_edge_process_relay_cell(cell_t *cell, circuit_t *circ,
           circuit_resume_edge_reading(circ, layer_hint);
 
           /* We count circuit-level sendme's as valid delivered data because
-           * they are rate limited. Note that we cannot count stream
-           * sendme's because the other end could send as many as they like.
+           * they are rate limited.
            */
           if (CIRCUIT_IS_ORIGIN(circ)) {
             circuit_read_valid_data(TO_ORIGIN_CIRCUIT(circ),
@@ -1783,6 +1782,27 @@ connection_edge_process_relay_cell(cell_t *cell, circuit_t *circ,
                  rh.stream_id);
         return 0;
       }
+
+      /* Don't allow the other endpoint to request more than our maximim
+       * (ie initial) stream SENDME window worth of data. Well-behaved
+       * stock clients will not request more than this max (as per the check
+       * in the while loop of connection_edge_consider_sending_sendme()).
+       */
+      if (conn->package_window + STREAMWINDOW_INCREMENT >
+          STREAMWINDOW_START_MAX) {
+        static struct ratelim_t stream_warn_ratelim = RATELIM_INIT(600);
+        log_fn_ratelim(&stream_warn_ratelim,LOG_PROTOCOL_WARN, LD_PROTOCOL,
+               "Unexpected stream sendme cell. Closing circ (window %d).",
+               conn->package_window);
+        return -END_CIRC_REASON_TORPROTOCOL;
+      }
+
+      /* At this point, the stream sendme is valid */
+      if (CIRCUIT_IS_ORIGIN(circ)) {
+        circuit_read_valid_data(TO_ORIGIN_CIRCUIT(circ),
+                                rh.length);
+      }
+
       conn->package_window += STREAMWINDOW_INCREMENT;
       log_debug(domain,"stream-level sendme, packagewindow now %d.",
                 conn->package_window);