Reload Ed25519 keys on sighup.

Closes ticket 16790.

changes/ed25519_hup

@@ -0,0 +1,4 @@
+  o Minor features (relay, Ed25519):
+    - On receiving a HUP signal, check to see whether the Ed25519
+      signing key has changed, and reload it if so. Closes ticket
+      16790.

src/or/main.c

@@ -2019,6 +2019,14 @@ do_hup(void)
    * force a retry there. */
 
   if (server_mode(options)) {
+    /* Maybe we've been given a new ed25519 key or certificate?
+     */
+    time_t now = approx_time();
+    if (load_ed_keys(options, now) < 0 ||
+         generate_ed_link_cert(options, now)) {
+      log_warn(LD_OR, "Problem reloading Ed25519 keys; still using old keys.");
+    }
+
     /* Update cpuworker and dnsworker processes, so they get up-to-date
      * configuration options. */
     cpuworkers_rotate_keyinfo();

src/or/routerkeys.c

@@ -635,10 +635,12 @@ load_ed_keys(const or_options_t *options, time_t now)
     goto err;                                   \
   } while (0)
 #define SET_KEY(key, newval) do {               \
+    if ((key) != (newval))                      \
       ed25519_keypair_free(key);                \
     key = (newval);                             \
   } while (0)
 #define SET_CERT(cert, newval) do {             \
+    if ((cert) != (newval))                     \
       tor_cert_free(cert);                      \
     cert = (newval);                            \
   } while (0)
@@ -648,10 +650,7 @@ load_ed_keys(const or_options_t *options, time_t now)
   /* XXXX support encrypted identity keys fully */
 
   /* First try to get the signing key to see how it is. */
-  if (master_signing_key) {
+  {
-    check_signing_cert = signing_key_cert;
-    use_signing = master_signing_key;
-  } else {
     char *fname =
       options_get_datadir_fname2(options, "keys", "ed25519_signing");
     sign = ed_key_init_from_file(
@@ -665,6 +664,11 @@ load_ed_keys(const or_options_t *options, time_t now)
     use_signing = sign;
   }
 
+  if (!use_signing && master_signing_key) {
+    check_signing_cert = signing_key_cert;
+    use_signing = master_signing_key;
+  }
+
   const int need_new_signing_key =
     NULL == use_signing ||
     EXPIRES_SOON(check_signing_cert, 0) ||