Merge branch 'maint-0.3.5' into release-0.3.5

3 files changed, 120 insertions, 10 deletions

diff --git a/src/core/or/protover.c b/src/core/or/protover.c
index dfb0e9e303..82e4f64c94 100644
--- a/src/core/or/protover.c
+++ b/src/core/or/protover.c
@@ -376,12 +376,49 @@ protocol_list_supports_protocol_or_later(const char *list,
   return contains;
 }
 
+/*
+ * XXX START OF HAZARDOUS ZONE XXX
+ */
+
 /** Return the canonical string containing the list of protocols
- * that we support. */
+ * that we support.
+ **/
 /// C_RUST_COUPLED: src/rust/protover/protover.rs `SUPPORTED_PROTOCOLS`
 const char *
 protover_get_supported_protocols(void)
 {
+
+  /*
+   * XXX: WARNING!
+   *
+   * Be EXTREMELY CAREFUL when *removing* versions from this list.  If you
+   * remove an entry while it still appears as "recommended" in the consensus,
+   * you'll cause all the instances without it to warn.
+   *
+   * If you remove an entry while it still appears as "required" in the
+   * consensus, you'll cause all the instances without it to refuse to connect
+   * to the network, and shut down.
+   *
+   * If you need to remove a version from this list, you need to make sure that
+   * it is not listed in the _current consensuses_: just removing it from the
+   * required list below is NOT ENOUGH.  You need to remove it from the
+   * required list, and THEN let the authorities upgrade and vote on new
+   * consensuses without it. Only once those consensuses are out is it safe to
+   * remove from this list.
+   *
+   * One concrete example of a very dangerous race that could occur:
+   *
+   * Suppose that the client supports protocols "HsDir=1-2" and the consensus
+   * requires protocols "HsDir=1-2.  If the client supported protocol list is
+   * then changed to "HSDir=2", while the consensus stills lists "HSDir=1-2",
+   * then these clients, even very recent ones, will shut down because they
+   * don't support "HSDir=1".
+   *
+   * And so, changes need to be done in strict sequence as described above.
+   *
+   * XXX: WARNING!
+   */
+
   return
     "Cons=1-2 "
     "Desc=1-2 "
@@ -399,6 +436,80 @@ protover_get_supported_protocols(void)
     "Relay=1-2";
 }
 
+/*
+ * XXX: WARNING!
+ *
+ * The recommended and required values are hardwired, to avoid disaster. Voting
+ * on the wrong subprotocols here has the potential to take down the network.
+ *
+ * In particular, you need to be EXTREMELY CAREFUL before adding new versions
+ * to the required protocol list.  Doing so will cause every relay or client
+ * that doesn't support those versions to refuse to connect to the network and
+ * shut down.
+ *
+ * Note that this applies to versions, not just protocols!  If you say that
+ * Foobar=8-9 is required, and the client only has Foobar=9, it will shut down.
+ *
+ * It is okay to do this only for SUPER OLD relays that are not supported on
+ * the network anyway.  For clients, we really shouldn't kick them off the
+ * network unless their presence is causing serious active harm.
+ *
+ * The following required and recommended lists MUST be changed BEFORE the
+ * supported list above is changed, so that these lists appear in the
+ * consensus BEFORE clients need them.
+ *
+ * Please, see the warning in protocol_get_supported_versions().
+ *
+ * XXX: WARNING!
+ */
+
+/*
+ * NOTE: A keen observer will notice that "LinkAuth" is not recommended nor
+ * required.  This is due to the HAVE_WORKING_TOR_TLS_GET_TLSSECRETS define
+ * that can either set "1" or "1,3" and so we can't enforce one or the other
+ * due to this uncertainty on how tor was built.
+ */
+
+/** Return the recommended client protocols list that directory authorities
+ * put in the consensus. */
+const char *
+protover_get_recommended_client_protocols(void)
+{
+  return "Cons=1-2 Desc=1-2 DirCache=1 HSDir=1 HSIntro=3 HSRend=1 "
+         "Link=4 Microdesc=1-2 Relay=2";
+}
+
+/** Return the recommended relay protocols list that directory authorities
+ * put in the consensus. */
+const char *
+protover_get_recommended_relay_protocols(void)
+{
+  return "Cons=1-2 Desc=1-2 DirCache=1 HSDir=1 HSIntro=3 HSRend=1 "
+         "Link=4 Microdesc=1-2 Relay=2";
+}
+
+/** Return the required client protocols list that directory authorities
+ * put in the consensus. */
+const char *
+protover_get_required_client_protocols(void)
+{
+  return "Cons=1-2 Desc=1-2 DirCache=1 HSDir=1 HSIntro=3 HSRend=1 "
+         "Link=4 Microdesc=1-2 Relay=2";
+}
+
+/** Return the required relay protocols list that directory authorities
+ * put in the consensus. */
+const char *
+protover_get_required_relay_protocols(void)
+{
+  return "Cons=1 Desc=1 DirCache=1 HSDir=1 HSIntro=3 HSRend=1 "
+         "Link=3-4 Microdesc=1 Relay=1-2";
+}
+
+/*
+ * XXX END OF HAZARDOUS ZONE XXX
+ */
+
 /** The protocols from protover_get_supported_protocols(), as parsed into a
  * list of proto_entry_t values. Access this via
  * get_supported_protocol_list. */
diff --git a/src/core/or/protover.h b/src/core/or/protover.h
index 7e181ba97a..c99dfe40ae 100644
--- a/src/core/or/protover.h
+++ b/src/core/or/protover.h
@@ -49,6 +49,10 @@ bool protover_contains_long_protocol_names(const char *s);
 int protover_all_supported(const char *s, char **missing);
 int protover_is_supported_here(protocol_type_t pr, uint32_t ver);
 const char *protover_get_supported_protocols(void);
+const char *protover_get_recommended_client_protocols(void);
+const char *protover_get_recommended_relay_protocols(void);
+const char *protover_get_required_client_protocols(void);
+const char *protover_get_required_relay_protocols(void);
 
 char *protover_compute_vote(const struct smartlist_t *list_of_proto_strings,
                             int threshold);
diff --git a/src/feature/dirauth/dirvote.c b/src/feature/dirauth/dirvote.c
index 9e01cee42a..d6a99d3ef8 100644
--- a/src/feature/dirauth/dirvote.c
+++ b/src/feature/dirauth/dirvote.c
@@ -4577,19 +4577,14 @@ dirserv_generate_networkstatus_vote_obj(crypto_pk_t *private_key,
   v3_out->client_versions = client_versions;
   v3_out->server_versions = server_versions;
 
-  /* These are hardwired, to avoid disaster. */
   v3_out->recommended_relay_protocols =
-    tor_strdup("Cons=1-2 Desc=1-2 DirCache=1 HSDir=1 HSIntro=3 HSRend=1 "
-               "Link=4 Microdesc=1-2 Relay=2");
+    tor_strdup(protover_get_recommended_relay_protocols());
   v3_out->recommended_client_protocols =
-    tor_strdup("Cons=1-2 Desc=1-2 DirCache=1 HSDir=1 HSIntro=3 HSRend=1 "
-               "Link=4 Microdesc=1-2 Relay=2");
+    tor_strdup(protover_get_recommended_client_protocols());
   v3_out->required_client_protocols =
-    tor_strdup("Cons=1-2 Desc=1-2 DirCache=1 HSDir=1 HSIntro=3 HSRend=1 "
-               "Link=4 Microdesc=1-2 Relay=2");
+    tor_strdup(protover_get_required_client_protocols());
   v3_out->required_relay_protocols =
-    tor_strdup("Cons=1 Desc=1 DirCache=1 HSDir=1 HSIntro=3 HSRend=1 "
-               "Link=3-4 Microdesc=1 Relay=1-2");
+    tor_strdup(protover_get_required_relay_protocols());
 
   /* We are not allowed to vote to require anything we don't have. */
   tor_assert(protover_all_supported(v3_out->required_relay_protocols, NULL));