backport r17970

svn:r17972

ChangeLog

@@ -70,6 +70,9 @@ Changes in version 0.2.0.33 - 2009-01-??
     - If a broken client asks a non-exit router to connect somewhere,
       do not even do the DNS lookup before rejecting the connection.
       Fixes another case of bug 619. Patch from rovv.
+    - When a relay gets a create cell it can't decrypt (e.g. because it's
+      using the wrong onion key), we were dropping it and letting the
+      client time out. Now actually answer with a destroy cell. Fixes                 bug 904. Bugfix on 0.0.2pre8.
 
   o Minor bugfixes (hidden services):
     - Do not throw away existing introduction points on SIGHUP. Bugfix on

src/or/cpuworker.c

@@ -276,7 +276,10 @@ cpuworker_main(void *data)
           reply_to_proxy, keys, CPATH_KEY_MATERIAL_LEN) < 0) {
         /* failure */
         log_debug(LD_OR,"onion_skin_server_handshake failed.");
-        memset(buf,0,LEN_ONION_RESPONSE); /* send all zeros for failure */
+        *buf = 0; /* indicate failure in first byte */
+        memcpy(buf+1,tag,TAG_LEN);
+        /* send all zeros as answer */
+        memset(buf+1+TAG_LEN, 0, LEN_ONION_RESPONSE-(1+TAG_LEN));
       } else {
         /* success */
         log_debug(LD_OR,"onion_skin_server_handshake succeeded.");