config: Remove FastFirstHopPK option

Deprecated in 0.2.9.2-alpha, this commits changes it as OBSOLETE() and cleans
up the code associated with it.

Partially fixes #22060

Signed-off-by: David Goulet <dgoulet@torproject.org>

changes/bug22060

@@ -7,3 +7,5 @@
       rendered obsolete. Code has been removed and feature no longer exists.
     - ExcludeSingleHopRelays was deprecated in 0.2.9.2-alpha and now has been
       rendered obsolete. Code has been removed and feature no longer exists.
+    - FastFirstHopPK was deprecated in 0.2.9.2-alpha and now has been rendered
+      obsolete. Code has been removed and feature no longer exists.

doc/tor.1.txt

@@ -1326,18 +1326,6 @@ The following options are useful only for clients (that is, if
     the node "foo". Disabled by default since attacking websites and exit
     relays can use it to manipulate your path selection. (Default: 0)
 
-[[FastFirstHopPK]] **FastFirstHopPK** **0**|**1**|**auto**::
-    When this option is disabled, Tor uses the public key step for the first
-    hop of creating circuits. Skipping it is generally safe since we have
-    already used TLS to authenticate the relay and to establish forward-secure
-    keys. Turning this option off makes circuit building a little
-    slower. Setting this option to "auto" takes advice from the authorities
-    in the latest consensus about whether to use this feature.  +
- +
-    Note that Tor will always use the public key step for the first hop if it's
-    operating as a relay, and it will never use the public key step if it
-    doesn't yet know the onion key of the first hop. (Default: auto)
-
 [[TransPort]] **TransPort**  \['address':]__port__|**auto** [_isolation flags_]::
     Open this port to listen for transparent proxy connections.  Set this to
     0 if you don't want to allow transparent proxy connections.  Set the port

src/or/circuitbuild.c

@@ -816,12 +816,7 @@ should_use_create_fast_for_circuit(origin_circuit_t *circ)
      * creating on behalf of others. */
     return 0;
   }
-  if (options->FastFirstHopPK == -1) {
-    /* option is "auto", so look at the consensus. */
-    return networkstatus_get_param(NULL, "usecreatefast", 0, 0, 1);
-  }
-
-  return options->FastFirstHopPK;
+  return networkstatus_get_param(NULL, "usecreatefast", 0, 0, 1);
 }
 
 /** Return true if <b>circ</b> is the type of circuit we want to count

src/or/config.c

@@ -323,7 +323,7 @@ static config_var_t option_vars_[] = {
   OBSOLETE("FallbackNetworkstatusFile"),
   V(FascistFirewall,             BOOL,     "0"),
   V(FirewallPorts,               CSV,      ""),
-  V(FastFirstHopPK,              AUTOBOOL, "auto"),
+  OBSOLETE("FastFirstHopPK"),
   V(FetchDirInfoEarly,           BOOL,     "0"),
   V(FetchDirInfoExtraEarly,      BOOL,     "0"),
   V(FetchServerDescriptors,      BOOL,     "1"),
@@ -664,8 +664,6 @@ static const config_deprecation_t option_deprecation_notes_[] = {
     "a wide variety of application-level attacks." },
   { "ClientDNSRejectInternalAddresses", "Turning this on makes your client "
     "easier to fingerprint, and may open you to esoteric attacks." },
-  { "FastFirstHopPK", "Changing this option does not make your client more "
-    "secure, but does make it easier to fingerprint." },
   { "CloseHSClientCircuitsImmediatelyOnTimeout", "This option makes your "
     "client easier to fingerprint." },
   { "CloseHSServiceRendCircuitsImmediatelyOnTimeout", "This option makes "

src/or/or.h

@@ -4057,8 +4057,6 @@ typedef struct {
   int NumDirectoryGuards; /**< How many dir guards do we try to establish?
                            * If 0, use value from NumEntryGuards. */
   int RephistTrackTime; /**< How many seconds do we keep rephist info? */
-  int FastFirstHopPK; /**< If Tor believes it is safe, should we save a third
-                       * of our PK time by sending CREATE_FAST cells? */
   /** Should we always fetch our dir info on the mirror schedule (which
    * means directly from the authorities) no matter our other config? */
   int FetchDirInfoEarly;