Implement Prop #260: Single Onion Services

Add experimental OnionServiceSingleHopMode and
OnionServiceNonAnonymousMode options. When both are set to 1, every
hidden service on a tor instance becomes a non-anonymous Single Onion
Service. Single Onions make one-hop (direct) connections to their
introduction and renzedvous points. One-hop circuits make Single Onion
servers easily locatable, but clients remain location-anonymous.
This is compatible with the existing hidden service implementation, and
works on the current tor network without any changes to older relays or
clients.

Implements proposal #260, completes ticket #17178. Patch by teor & asn.

squash! fixup! fixup! fixup! fixup! fixup! fixup! fixup! fixup! fixup! fixup! fixup! fixup! fixup! Implement Prop #260: Single Onion Services

Redesign single onion service poisoning.

When in OnionServiceSingleHopMode, each hidden service key is poisoned
(marked as non-anonymous) on creation by creating a poison file in the
hidden service directory.

Existing keys are considered non-anonymous if this file exists, and
anonymous if it does not.

Tor refuses to launch in OnionServiceSingleHopMode if any existing keys
are anonymous. Similarly, it refuses to launch in anonymous client mode
if any existing keys are non-anonymous.

Rewrite the unit tests to match and be more comprehensive.
Adds a bonus unit test for rend_service_load_all_keys().

1 files changed, 26 insertions, 3 deletions

diff --git a/src/or/connection_edge.c b/src/or/connection_edge.c
index dc6b0930ca..8ad0f0c71d 100644
--- a/src/or/connection_edge.c
+++ b/src/or/connection_edge.c
@@ -27,6 +27,7 @@
 #include "control.h"
 #include "dns.h"
 #include "dnsserv.h"
+#include "directory.h"
 #include "dirserv.h"
 #include "hibernate.h"
 #include "main.h"
@@ -2271,6 +2272,7 @@ connection_ap_handshake_send_begin(entry_connection_t *ap_conn)
   char payload[CELL_PAYLOAD_SIZE];
   int payload_len;
   int begin_type;
+  const or_options_t *options = get_options();
   origin_circuit_t *circ;
   edge_connection_t *edge_conn = ENTRY_TO_EDGE_CONN(ap_conn);
   connection_t *base_conn = TO_CONN(edge_conn);
@@ -2314,10 +2316,31 @@ connection_ap_handshake_send_begin(entry_connection_t *ap_conn)
 
   begin_type = ap_conn->use_begindir ?
                  RELAY_COMMAND_BEGIN_DIR : RELAY_COMMAND_BEGIN;
+
+  /* Check that circuits are anonymised, based on their type. */
   if (begin_type == RELAY_COMMAND_BEGIN) {
-#ifndef NON_ANONYMOUS_MODE_ENABLED
-    tor_assert(circ->build_state->onehop_tunnel == 0);
-#endif
+    /* This connection is a standard OR connection.
+     * Make sure its path length is anonymous, or that we're in a
+     * non-anonymous mode. */
+    assert_circ_anonymity_ok(circ, options);
+  } else if (begin_type == RELAY_COMMAND_BEGIN_DIR) {
+    /* This connection is a begindir directory connection.
+     * Look at the linked directory connection to access the directory purpose.
+     * (This must be non-NULL, because we're doing begindir.) */
+    tor_assert(base_conn->linked);
+    connection_t *linked_dir_conn_base = base_conn->linked_conn;
+    tor_assert(linked_dir_conn_base);
+    /* Sensitive directory connections must have an anonymous path length.
+     * Otherwise, directory connections are typically one-hop.
+     * This matches the earlier check for directory connection path anonymity
+     * in directory_initiate_command_rend(). */
+    if (is_sensitive_dir_purpose(linked_dir_conn_base->purpose)) {
+      assert_circ_anonymity_ok(circ, options);
+    }
+  } else {
+    /* This code was written for the two connection types BEGIN and BEGIN_DIR
+     */
+    tor_assert_unreached();
   }
 
   if (connection_edge_send_command(edge_conn, begin_type,