Commit 0849d2a2 authored by Nick Mathewson's avatar Nick Mathewson 🥔
Browse files

Avoid using labs() on time_t in channeltls.c 

On some windows builds, time_t is 64 bits but long is not.  This is
causing appveyor builds to fail.

Also, one of our uses of labs() on time_t was logically incorrect:
it was telling us to accept NETINFO cells up to three minutes
_before_ the message they were responding to, which doesn't make
sense.

This patch adds a time_abs() function that we should eventually move
to intmath.h or something.  For now, though, it will make merges
easier to have it file-local in channeltls.c.

Fixes bug 31343; bugfix on 0.2.4.4-alpha.
parent fb977f8c

changes/bug31343

0 → 100644
+9 −0
Original line number Diff line number Diff line 
  o Minor bugfixes (compilation):

    - Avoid using labs() on time_t, which can cause compilation warnings

      on 64-bit Windows builds.  Fixes bug 31343; bugfix on 0.2.4.4-alpha.



  o Minor bugfixes (clock skew detection):

    - Don't believe clock skew results from NETINFO cells that appear to

      arrive before the VERSIONS cells they are responding to were sent.

      Previously, we would accept them up to 3 minutes "in the past".

      Fixes bug 31343; bugfix on 0.2.4.4-alpha.

src/or/channeltls.c

+19 −4
Original line number Diff line number Diff line
@@ -1583,6 +1583,18 @@ channel_tls_process_versions_cell(var_cell_t *cell, channel_tls_t *chan) 
  }

}



/**

 * Helper: compute the absolute value of a time_t.

 *

 * (we need this because labs() doesn't always work for time_t, since

 * long can be shorter than time_t.)

 */

static inline time_t

time_abs(time_t val)

{

  return (val < 0) ? -val : val;

}



/**

 * Process a 'netinfo' cell

 *
@@ -1601,7 +1613,7 @@ channel_tls_process_netinfo_cell(cell_t *cell, channel_tls_t *chan) 
  uint8_t n_other_addrs;

  time_t now = time(NULL);



  long apparent_skew = 0;

  time_t apparent_skew = 0;

  tor_addr_t my_apparent_addr = TOR_ADDR_NULL;



  tor_assert(cell);
@@ -1659,7 +1671,11 @@ channel_tls_process_netinfo_cell(cell_t *cell, channel_tls_t *chan) 


  /* Decode the cell. */

  timestamp = ntohl(get_uint32(cell->payload));

  if (labs(now - chan->conn->handshake_state->sent_versions_at) < 180) {

  const time_t sent_versions_at =

    chan->conn->handshake_state->sent_versions_at;

  if (now > sent_versions_at && (now - sent_versions_at) < 180) {

    /* If we have gotten the NETINFO cell reasonably soon after having

     * sent our VERSIONS cell, maybe we can learn skew information from it. */

    apparent_skew = now - timestamp;

  }
@@ -1705,7 +1721,7 @@ channel_tls_process_netinfo_cell(cell_t *cell, channel_tls_t *chan) 
  /* Act on apparent skew. */

  /** Warn when we get a netinfo skew with at least this value. */

#define NETINFO_NOTICE_SKEW 3600

  if (labs(apparent_skew) > NETINFO_NOTICE_SKEW &&

  if (time_abs(apparent_skew) &&

      router_get_by_id_digest(chan->conn->identity_digest)) {

    int trusted = router_digest_is_trusted_dir(chan->conn->identity_digest);

    clock_skew_warning(TO_CONN(chan->conn), apparent_skew, trusted, LD_GENERAL,
@@ -2182,4 +2198,3 @@ channel_tls_process_authenticate_cell(var_cell_t *cell, channel_tls_t *chan) 


#undef ERR

}