app/config: reject non-UTF-8 ContactInfo

Closes ticket #27428.

changes/bug27428

@@ -0,0 +1,3 @@
+  o Minor bugfixes (torrc):
+    - Tor now validates that the ContactInfo config option is valid UTF-8
+      when parsing torrc. Fixes bug 27428; bugfix on 0.0.8pre1.

src/app/config/config.c

@@ -3381,6 +3381,9 @@ options_validate(or_options_t *old_options, or_options_t *options,
     log_notice(LD_CONFIG, "Your ContactInfo config option is not set. "
         "Please consider setting it, so we can contact you if your server is "
         "misconfigured or something else goes wrong.");
+  const char *ContactInfo = options->ContactInfo;
+  if (ContactInfo && !string_is_utf8(ContactInfo, strlen(ContactInfo)))
+    REJECT("ContactInfo config option must be UTF-8.");
 
   /* Special case on first boot if no Log options are given. */
   if (!options->Logs && !options->RunAsDaemon && !from_setconf) {