Refuse to make direct connections to private OR addresses

Refuse connection requests to private OR addresses unless
ExtendAllowPrivateAddresses is set. Previously, tor would
connect, then refuse to send any cells to a private address.

Fixes bugs 17674 and 8976; bugfix on b7c172c9ec76 (28 Aug 2012)
Original bug 6710, released in 0.2.3.21-rc and an 0.2.2 maint
release.

Patch by "teor".

diff --git a/doc/tor.1.txt b/doc/tor.1.txt
index aba0c1c39690bcc35eb0452874e02a71c0366b04..2ada5688cdaf82877bfe765899a6c485ee448003 100644 (file)
--- a/doc/tor.1.txt
+++ b/doc/tor.1.txt
@@ -1898,9 +1898,11 @@ is non-zero):
     (Default: 1)
 
 [[ExtendAllowPrivateAddresses]] **ExtendAllowPrivateAddresses** **0**|**1**::
-    When this option is enabled, Tor routers allow EXTEND request to
-    localhost, RFC1918 addresses, and so on. This can create security issues;
-    you should probably leave it off. (Default: 0)
+    When this option is enabled, Tor will connect to localhost, RFC1918
+    addresses, and so on. In particular, Tor will make direct connections, and
+    Tor routers allow EXTEND requests, to these private addresses. This can
+    create security issues; you should probably leave it off.
+    (Default: 0)
 
 [[MaxMemInQueues]] **MaxMemInQueues**  __N__ **bytes**|**KB**|**MB**|**GB**::
     This option configures a threshold above which Tor will assume that it

diff --git a/src/or/circuitbuild.c b/src/or/circuitbuild.c
index 0688398f6da670ac8a005f725ffb4f0b72ebf723..933d70bd8bf46506076ab666ed2bd5aec4cd7732 100644 (file)
--- a/src/or/circuitbuild.c
+++ b/src/or/circuitbuild.c
@@ -498,6 +498,14 @@ circuit_handle_first_hop(origin_circuit_t *circ)
   tor_assert(firsthop);
   tor_assert(firsthop->extend_info);
 
+  /* XX/teor - does tor ever need build a circuit directly to itself? */
+  if (tor_addr_is_internal(&firsthop->extend_info->addr, 0) &&
+      !get_options()->ExtendAllowPrivateAddresses) {
+    log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
+           "Client asked me to connect directly to a private address");
+    return -END_CIRC_REASON_TORPROTOCOL;
+  }
+
   /* now see if we're already connected to the first OR in 'route' */
   log_debug(LD_CIRC,"Looking for firsthop '%s'",
             fmt_addrport(&firsthop->extend_info->addr,